ThinkRF R5500 Manual

ThinkRF R5500/R5550
Real-Time Spectrum Analyzer
Programmer's Guide
Version 4.4.1
April 2 , 2020
Document no. 75-0025-20042
Copyright © 2015-2020 ThinkRF Corporation, all rights reserved.
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HARDWARE WARRANTY AND LI ITATION OF LIABILITY
Read this warranty carefully before you use the product.
WSA5000 and R55x0 Real Time Spectrum Analyzers are warranted for
workmanship and materials for a period of one (1) year from the date of shipment as
identified by the Customer’s packing slip or carrier waybill. ThinkRF reserves the
right to void the warranty on any equipment that has been altered or damaged due
to Customer negligence, unauthorized repair, misuse of equipment, evidence of
physical or environmental damage, transportation abuse or removal of any ThinkRF
identification labels or serial numbers.
It will remain the responsibility of the Customer, having obtained a Return Material
Authorization (RMA) and shipping instructions from ThinkRF, to return, at the
Customer's expense, the defective unit to ThinkRF’s repair facilities. ThinkRF will
incur shipping charges for the return of warranty repaired equipment. The RMA
number can be secured by calling ThinkRF Customer Service and Support (1- 13-
3 9-5104). If the product does not fall within ThinkRF’s warranty period or the
product is found to be functioning as designed, then under the terms of ThinkRF’s
warranty policy, all costs of repairs and shipping will be charged directly to the
Customer. ThinkRF will warrant repaired units for a period of 90 days from date of
shipment from ThinkRF to the Customer. If the remaining period on the original
hardware warranty is greater than 30 days, then ThinkRF will honor this remaining
warranty period.
THINKRF EXPRESSLY DISCLAIMS ALL OTHER WARRANTIES AND
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DAMAGES.
USE OF PRODUCTS IN HIGH RISK ACTIVITIES
THINKRF PRODUCTS ARE INTENDED FOR STANDARD INDOOR COMMERCIAL
USE. WITHOUT THE APPROPRIATE NETWORK DESIGN ENGINEERING, THEY
MUST NOT BE USED FOR ANY “HIGH RISK ACTIVITY”, as described in this
paragraph. Customer acknowledges and agrees that the products supplied
hereunder are not fault-tolerant and are not designed, manufactured or intended for
use or resale as on-line control equipment in hazardous environments requiring fail
safe performance including but not limited to the operation of nuclear facilities,
aircraft navigation or communication systems, air traffic control, direct life support
machines, or weapons systems, in which the failure of products could lead directly to
death, personal injury, or severe physical or environmental damage, all of which are
examples of “High Risk Activity”. THINKRF AND ITS SUPPLIERS EXPRESSLY
DISCLAIM ANY EXPRESS OR IMPLIED WARRANTY OF FITNESS FOR HIGH
RISK ACTIVITIES.
GNU General Public License
This device contains free firmware: you can redistribute it and/or modify it under the
terms of the GNU General Public License as published by the Free Software
Foundation, either version 2 of the License, or (at your option) any later version. This
program is distributed in the hope that it will be useful, but WITHOUT ANY
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FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
for more details. GNU General Public License is available at
http://www.gnu.org/licenses.

Table of Contents
Abbreviations ................................................................................................................................... 7
List of Figures .................................................................................................................................. 8
List of Tables .................................................................................................................................... 9
Preface ............................................................................................................................................... 10
Audience ................................................................................................................................... 10
Conventions ............................................................................................................................ 10
Obtaining Documentation and Releases .......................................................................... 10
Document Feedback .............................................................................................................. 11
Obtaining Technical Assistance ......................................................................................... 11
R5500/R5550 Functional Overview ..................................................................................... 12
System Overview .................................................................................................................... 12
The Architecture ..................................................................................................................... 15
RF Receiver Front-End .......................................................................................................... 17
Direct-Conversion Receiver Technology ............................................................................. 18
DC Offset Correction ..................................................................................................... 18
IQ Offset Correction ....................................................................................................... 19
Digital Signal Processing ..................................................................................................... 20
Digital Down Converter ........................................................................................................ 20
Triggers ..................................................................................................................................... 21
Frequency Domain Triggering ............................................................................................. 21
Periodic Triggering .............................................................................................................. 22
External Triggering .............................................................................................................. 22
Capture Controller .................................................................................................................. 23
Trace Capture Control ......................................................................................................... 23
Sweep Capture Control ....................................................................................................... 24
Synchronized Sweep ........................................................................................................... 25
VITA-49 Radio Transport Protocol ...................................................................................... 28
Purpose ..................................................................................................................................... 28
R55x0's VRT Overview .......................................................................................................... 28
Packet Classes and Streams ............................................................................................... 29
Receiver Context Packet Class ........................................................................................... 29
Context Field Change Indicator ..................................................................................... 31
RF Reference Frequency .............................................................................................. 31
Gain ............................................................................................................................... 31
Digitizer Context Packet Class ............................................................................................ 31
Context Field Change Indicator ..................................................................................... 33
Bandwidth ...................................................................................................................... 33
RF Frequency Offset ..................................................................................................... 33
Reference Level ............................................................................................................ 33
Extension Context Packet Class .......................................................................................... 34
Context Field Change Indicator ..................................................................................... 3
IQ Swapped Indicator .................................................................................................... 3
New Stream Start ID ...................................................................................................... 3
New Sweep Start ID ...................................................................................................... 37
IF Data Packet Class ........................................................................................................... 37
Picosecond Timestamp Words Format .......................................................................... 38
Data Payload Format ..................................................................................................... 38
Trailer Word Format ...................................................................................................... 40

SCPI Command Set ..................................................................................................................... 43
SCPI Language Overview ..................................................................................................... 43
IEEE andated SCPI Commands ....................................................................................... 44
*CLS .................................................................................................................................... 44
*ESE/*ESE? ........................................................................................................................ 44
*ESR? .................................................................................................................................. 45
*IDN? ................................................................................................................................... 45
*OPC/*OPC? ....................................................................................................................... 45
*RST .................................................................................................................................... 45
*SRE/*SRE? ........................................................................................................................ 4
*STB? .................................................................................................................................. 4
*TST? .................................................................................................................................. 4
*WAI .................................................................................................................................... 47
SYSTem Commands .............................................................................................................. 47
:SYSTem:ABORt ................................................................................................................. 47
:SYSTem:CAPTure:MODE? ................................................................................................ 47
:SYSTem:COMMunicate:HISLip:SESSion? ........................................................................ 48
:SYSTem:COMMunicate:LAN:APPLy .................................................................................. 48
:SYSTem:COMMunicate:LAN:CONFigure .......................................................................... 48
:SYSTem:COMMunicate:LAN:DNS ..................................................................................... 49
:SYSTem:COMMunicate:LAN:GATEway ............................................................................ 49
:SYSTem:COMMunicate:LAN:IP ......................................................................................... 50
:SYSTem:COMMunicate:LAN:MTU ..................................................................................... 50
:SYSTem:COMMunicate:LAN:NETMask ............................................................................. 51
:SYSTem:COMMunicate:NTP ............................................................................................. 51
:SYSTem:ERRor[:NEXT]? ................................................................................................... 52
:SYSTem:ERRor:ALL? ........................................................................................................ 52
:SYSTem:ERRor:CODE[:NEXT]? ........................................................................................ 52
:SYSTem:ERRor:CODE:ALL? ............................................................................................. 53
:SYSTem:ERRor:COUNt? ................................................................................................... 53
:SYSTem:FLUSh ................................................................................................................. 53
:SYSTem:LOCK:HAVE? ...................................................................................................... 54
:SYSTem:LOCK:REQuest? ................................................................................................. 54
:SYSTem:OPTions? ............................................................................................................ 55
:SYSTem:SYNC:MASTer .................................................................................................... 5
:SYSTem:SYNC:WAIT ........................................................................................................ 5
:SYSTem:VERSion? ............................................................................................................ 5
:SYSTem:DATE ................................................................................................................... 5
:SYSTem:TIME .................................................................................................................... 57
:SYSTem:TIME:ADJust ....................................................................................................... 57
:SYSTem:TIME:SYNC ......................................................................................................... 58
STATus Commands ............................................................................................................... 59
:STATus:OPERation[:EVENt]? ............................................................................................ 0
:STATus:OPERation:CONDition? ........................................................................................ 0
:STATus:OPERation:ENABle .............................................................................................. 1
:STATus:OPERation:NTRansition ....................................................................................... 1
:STATus:OPERation:PTRansition ....................................................................................... 1
:STATus:PRESET ............................................................................................................... 2
:STATus:QUEStionable[:EVENt]? ....................................................................................... 2
:STATus:QUEStionable:CONDition? ................................................................................... 2
:STATus:QUEStionable:ENABle ......................................................................................... 3
:STATus:QUEStionable:NTRansition .................................................................................. 3
:STATus:QUEStionable:PTRansition ................................................................................... 3
:STATus:TEMPerature? ...................................................................................................... 4
INPut Commands .................................................................................................................... 64
:INPut:ATTenuator ............................................................................................................... 4
:INPut:ATTenuator:VARiable ............................................................................................... 4

:INPut:GAIN ......................................................................................................................... 5
:INPut:GAIN:HDR ................................................................................................................
:INPut:MODE .......................................................................................................................
SOURce Commands .............................................................................................................. 67
:SOURce:REFerence:PLL ................................................................................................... 7
SENSe Commands ................................................................................................................. 67
[:SENSe]:DECimation .......................................................................................................... 7
[:SENSe]:FREQuency:CENTer ........................................................................................... 8
[:SENSe]:FREQuency:IF? ................................................................................................... 9
[:SENSe]:FREQuency:INVersion? ....................................................................................... 9
[:SENSe]:FREQuency:LOSCillator? .................................................................................... 70
[:SENSe]:FREQuency:SHIFt ............................................................................................... 70
[:SENSe]:LOCK:REFerence? .............................................................................................. 71
[:SENSe]:LOCK:RF? ........................................................................................................... 71
OUTput Commands ............................................................................................................... 71
:OUTput:MODE ................................................................................................................... 71
TRIGger Commands .............................................................................................................. 72
:TRIGger:TYPE ................................................................................................................... 72
:TRIGger:LEVel ................................................................................................................... 73
:TRIGger:PERiodic .............................................................................................................. 74
TRACe Commands ................................................................................................................. 74
:TRACe:BLOCk:DATA? ....................................................................................................... 74
:TRACe:BLOCk:PACKets .................................................................................................... 75
:TRACe:SPPacket ............................................................................................................... 7
:TRACe:STReam:STARt ..................................................................................................... 7
:TRACe:STReam:STOP ...................................................................................................... 77
SWEep Commands ................................................................................................................ 78
:SWEep:LIST:ITERations .................................................................................................... 79
:SWEep:LIST:STARt ........................................................................................................... 79
:SWEep:LIST:STATus? ....................................................................................................... 80
:SWEep:LIST:STOP ............................................................................................................ 80
:SWEep:ENTRy:COPY ........................................................................................................ 80
:SWEep:ENTRy:COUNt? .................................................................................................... 81
:SWEep:ENTRy:DELETE .................................................................................................... 81
:SWEep:ENTRy:NEW .......................................................................................................... 81
:SWEep:ENTRy:READ? ...................................................................................................... 81
:SWEep:ENTRy:SAVE ........................................................................................................ 82
:SWEep:ENTRy:ATTenuator ............................................................................................... 82
:SWEep:ENTRy:ATTenuator:VARiable ............................................................................... 82
:SWEep:ENTRy:DECimation ............................................................................................... 82
:SWEep:ENTRy:FREQuency:CENTer ................................................................................. 83
:SWEep:ENTRy:FREQuency:STEP .................................................................................... 83
:SWEep:ENTRy:FREQuency:SHIFt .................................................................................... 83
:SWEep:ENTRy:GAIN:HDR ................................................................................................ 84
:SWEep:ENTRy:MODE ....................................................................................................... 84
:SWEep:ENTRy:DWELl ....................................................................................................... 84
:SWEep:ENTRy:PPBlock .................................................................................................... 84
:SWEep:ENTRy:SPPacket .................................................................................................. 85
:SWEep:ENTRy:TRIGger:LEVel .......................................................................................... 85
:SWEep:ENTRy:TRIGger:TYPE .......................................................................................... 85
Appendix A: Connecting to RTSA ...................................................................................... 86
Simple 2-port TCP/IP Connection ....................................................................................... 86
Connection Using HiSLIP ..................................................................................................... 87

Appendix B: Protocols for Discovering RTSA ............................................................. 90
Discovery Using mDNS/DNS-SD ........................................................................................ 90
Discovery Using Broadcast UDP ........................................................................................ 90
Appendix C: SCPI Command Syntax ................................................................................ 92
Entering Commands .............................................................................................................. 92
Notation .................................................................................................................................... 93
Parameter types ...................................................................................................................... 93
Default Units ............................................................................................................................ 93
Appendix D: SCPI Status and Event Registers ........................................................... 95
Status Byte Register (SBR) .................................................................................................. 95
Standard Event Status Register (ESR) .............................................................................. 95
Operational Status Register (OSR) .................................................................................... 96
Questionable Status Register (QSR) ................................................................................. 96
Output Queue .......................................................................................................................... 97
Error and Event Queue ......................................................................................................... 97
Appendix E: SCPI Error Codes Used ................................................................................ 98
Appendix F: SCPI Commands Quick Reference ......................................................... 99
WSA5000 vs. R5500/R5550 List of Changes ............................................................... 105
References ..................................................................................................................................... 106
Document Revision History ................................................................................................. 107

Abbreviations
ADC Analog-to-Digital Converter
API Application Programming Interface
CIC Cascaded Integrator-Comb
DC Direct Current
DD Direct Digitizer
DDC Digital Down Converter
DDS Direct Digital Synthesizer
DSP Digital Signal Processing
FFT Fast Fourier Transform
FIR Finite Impulse Response
FPGA Field-Programmable Gate Array
GPIO General Purpose Input/Output
GUI Graphical User Interface
HDR High Dynamic Range
HIF High Intermediate Frequency
IBW Instantaneous Bandwidth
IEEE Institute of Electrical and Electronics Engineers
IF Intermediate Frequency
IQ In-phase and Quadrature
LAN Local Area Network
B Mega-Bytes
SB Most Significant Byte
Sa Mega-Samples
NB Narrowband
NCO Numerically Controlled Oscillator
NTP Network Time Protocol
NTPD Network Time Protocol Daemon
PLL Phase-Locked Loop
RF Radio Frequency
RFE Receiver Front-End
RTSA Real Time Spectrum Analyzer
Sa/s Samples-per-Second
SCPI Standard Commands for Programmable Instruments
SH Super-Heterodyne
SHN Super-Heterodyne with narrower bandwidth
TCP/IP Transmission Control Protocol/Internet Protocol
TD Time Domain
TSF TimeStamp-Fractional
TSI TimeStamp-Integer
TS TimeStamp Mode
UTC Coordinated Universal Time
VCO Voltage Control Oscillator
VRT VITA-49 Radio Transport
WB Wideband
ZIF Zero Intermediate Frequency

List of Figures
Figure 1: R55x0 Functional Block Diagram .............................................................................................. 13
Figure 2: RF Receiver Front-end and Capture Controller Functional Block Diagram ............................... 1
Figure 3: DC Offset with Amplitude Roll-Off at +50MHz .......................................................................... 18
Figure 4: IQ Offset Correction .................................................................................................................. 19
Figure 5: DDC Functional Block Diagram ................................................................................................ 21
Figure 6: Association between Time and Frequency Domain .................................................................. 22
Figure 7: Synchronized Sweep using Sync-Word .................................................................................... 2
Figure 8: Synchronized Sweep with a Missed Capture ............................................................................ 27
Figure 9: Connectivity and 4 Different Packet Streams Supported by R55x0 .......................................... 28
Figure 10: An Example Illustrating Uninverted and Inverted Spectrums .................................................. 42
Figure 11: SCPI Language Hierarchical or Tree Structure Example ........................................................ 43
Figure 12: SCPI Measurement Function Block ........................................................................................ 44
Figure 13: Status Reporting Structure with Status & Enable Registers .................................................... 59
Figure 14: 2-port TCP/IP connection to RTSA ......................................................................................... 8
Figure 15: HiSLIP and TCP connections to RTSA ................................................................................... 88

List of Tables
Table 1: System Level Control/Status Commands ................................................................................... 13
Table 2: Radio RFE Modes and DSP Data Output Formats .................................................................... 17
Table 3: RF Front-End Control/Status Commands .................................................................................. 19
Table 4: Trigger Control/Status Commands ............................................................................................. 23
Table 5: Trace Capture Control Commands ............................................................................................ 24
Table 6: Sweep Capture Control/Status Interface .................................................................................... 24
Table 7: The Categories of VRT Packet Streams Supported by ThinkRF's R55x0 .................................. 28
Table 8: A List of Stream Identifiers as Used by ThinkRF for Different Packet Classes .......................... 29
Table 9: Receiver Context Packet Class Structure .................................................................................. 30
Table 10: Receiver Context Indicator Field Positions ............................................................................... 30
Table 11: Receiver Context Field Definition and Values .......................................................................... 30
Table 12: RF Reference Frequency Word Format ................................................................................... 31
Table 13: Gain Field Format .................................................................................................................... 31
Table 14: Digitizer Context Packet Class Structure ................................................................................. 32
Table 15: Digitizer Context Indicator Field Bit Positions ........................................................................... 32
Table 16: Digitizer Context Field Values .................................................................................................. 33
Table 17: Bandwidth Word Format .......................................................................................................... 33
Table 18: RF Frequency Offset Word Format .......................................................................................... 33
Table 19: Reference Level Field Format .................................................................................................. 34
Table 20: Extension Context Packet Class Structure ............................................................................... 35
Table 21: Extension Context Indicator Field Positions ............................................................................. 35
Table 22: Extension Context Field Definition and Values ........................................................................ 3
Table 23: IQ Swapped Field Format ........................................................................................................ 3
Table 24: New Stream Start ID Field Format ........................................................................................... 37
Table 25: New Sweep Start ID Field Format ............................................................................................ 37
Table 26: Output Data Width and Packing Method for Different Data Formats ........................................ 37
Table 27: IF Data Class Field Values ....................................................................................................... 37
Table 28: Stream Identifier Values for Different Data Output Formats ..................................................... 38
Table 29: 4-bit or Two Words Picosecond Timestamp Format .............................................................. 38
Table 30: {I14Q14} Data Payload Arrangement with Upper 2-bit Signed Extended to {I1 Q1 } .................... 39
Table 31: {I14} Data Payload Arrangement with Upper 2-bit Signed Extended to {I1 } .............................. 39
Table 32: {I24} Data Payload Arrangement with Upper 8-bit Signed Extended to {I32} .............................. 40
Table 33: Trailer Word Format ................................................................................................................. 40
Table 34: Trailer Indicator and Enable Bits .............................................................................................. 40
Table 35: Conditions Causing Abnormal Indicator State and Suggested Resolution ............................... 41
Table 36: RTSA Option Codes and the Corresponding Description ........................................................ 5
Table 37: Performance of The Gain Settings of R55x0-418, 427 and Their Variants .............................. 5
Table 38: Maximum Threshold Level Where +/-3 dBm Error or Less Still Hold For A Given Attenuation
Level ....................................................................................................................................... 73
Table 39: Max, Min, and Required Multiples for SPP and Samples-per-word for Different Data Output
Format .................................................................................................................................... 7
Table 40: HiSLIP Message Header Format ............................................................................................. 88
Table 41: ThinkRF Vendor Specific Message Type Value Definitions ..................................................... 89
Table 42: ThinkRF Data Channel Initialization Transaction ..................................................................... 89

Preface
This preface describes the audience for, the organization of, and conventions used in this
document. It also identifies related documentation and explains how to access electronic
documentation.
Audience
This document is written for software developers wishing to develop and/or maintain a
software interface to the R5500/R5550 (R55x0 for short) and who have a basic
understanding, familiarity and experience with network test and measurement equipment.
Conventions
This section describes the conventions used in this document.
Grayed-out Font
Indicates a command or a feature is not yet available in the current release.
Courier Font
Illustrates this is an example for a command or a concept.
Light Blue Font
Contains hyperlink to the referenced source that can be clicked on.
Normal Bold Font
When used within a sentence or a paragraph, it emphasizes an idea to be paid attention
to particularly.
Red Font
Conveys special information of that section.
Note: This symbol means take note. Notes contain helpful suggestions or references to
additional information and material.
Caution: This symbol means be careful. In this situation, you might do something that
could result in equipment damage or loss of data.
Warning: This symbol means danger. You are in a situation that could cause bodily
injury. Before you work on any equipment, be aware of the hazards involved with
electrical circuitry and be familiar with the standard practices for preventing accidents.
Obtaining Documentation and Releases
You can access the most current ThinkRF documentation and the latest release bundles
at http://www.thinkrf.com/resources.

Document Feedback
Please send your comments about this document or our other documentation to
[email protected].
Thank you, we appreciate your comments.
Obtaining Technical Assistance
The ThinkRF Support website provides online documents for resolving technical issues
with ThinkRF products at www.thinkrf.com/resources.
For all customers who hold a valid end-user license, ThinkRF provides technical
assistance 9 AM to 5 PM Eastern Time, Monday to Friday. Contact us at
www.thinkrf.com/support/ or by calling +1.613.369.5104.
Before contacting Support, please have the following information available:
•R55x0's serial number and product version, which are located on the identification
label on the R55x0's underside.
•The firmware version running on the R55x0.
•Versions of ThinkRF software you are using, potentially including the S240, API
libraries to third-party applications.
•The operating system and version you are using.

R5500/R5550 Functional Overview
R5500/R5550 Functional Overview
This section overviews the R5500/5550's (R55x0 for short) functionality and protocols
used, and summarizes the SCPI command sets for controlling the individual functions.
Note: This is a living and evolving document. We welcome your feedback.
The features and functionality described in this section may exist in the current product
firmware release or are scheduled for a future product firmware release (grayed out
commands and/or text). Please refer to Appendix F: SCPI Commands Quick Reference
for the complete list of commands and the availability information. No hardware upgrade
is required at each feature release (unless specified though unlikely).
System Overview
The R55x0 Real Time Spectrum Analyzer (RTSA) is a high-performance software-
defined RF receiver, digitizer and analyzer, as illustrated in Figure 1. With patent-
pending software-defined RF receiver technology, the RTSA provides industry leading
combined sensitivity, tuning range, instantaneous bandwidth (IBW) and scan rate.
Additionally, it provides real-time sophisticated triggering and capture control.
The R55x0 is designed for stand-alone, remote and/or distributed wireless signal
analysis. It is ideal for monitoring, management and surveillance of transmitters, whether
they are in-building or spread across a geographic area. Applications include, but are not
limited to:
•5G wireless technology;
•research;
•test and measurement;
•monitoring;
•OEM integration.
The R55x0 hardware largely consists of:
•a hybrid super-heterodyne, direct-conversion and direct-digitization RF receiver
front-end (RFE);
•receiver front end inputs and outputs to support clock synchronization, and IF
outputs for high-end digitization;
•a 125 MSample/sec 14-bit wideband (WB) ADC with a dynamic range of greater
than 70 dB;
•a 325 kSample/sec 24-bit narrowband (NB) ADC with a dynamic range in excess of
100 dB;
•a Xilinx's Zynq FPGA with built-in dual-core ARM®-based processor, Gigabit
Ethernet interface and custom embedded digital signal processing (DSP) logic;
•1 GB of DDR3 shared between firmware and real-time caching of digitized data;
•a general purpose input/output (GPIO) port.
ThinkRF R5500/R5550 Real Time Spectrum Analyzer Programmer's Guide 12

R5500/R5550 Functional Overview
Figure 1: R55x0 Functional Block Diagram
ThinkRF's products conform with standardized protocols for interoperability. ThinkRF
provides application programming interfaces (APIs) designed for easy integration with
third-party applications. Standard protocols include the Standard Commands for
Programmable Instruments (SCPI) protocol for controlling and obtaining status from the
RTSA and the VITA-49 Radio Transport (VRT) protocol for digitized data and its
associated context information.
In addition, API libraries, written in C/C++, Python, MATLAB and NI LabVIEW, are
provided for quick interfacing, data acquisition and as well as for spectral analysis with
MATLAB® applications. The Python API is built within the PyRF development framework
and is open-source under BSD licensing. PyRF handles the low-level details of real-time
acquisition, signal processing and visualization, and provides feature rich libraries,
example applications and source code, all specific to the requirements of signal analysis.
Usage examples are provided through the available source codes of the Graphical User
Interfaces (GUIs) or any applications included in each release package.
Refer to Appendix A for how to connect to an RTSA and Appendix B for the protocol on
how to find any RTSAs available on the local network. The source code provided for the
aforementioned APIs and GUIs/applications would serve as examples.
The R55x0 provides system level control and status commands as defined in Table 1.
Table 1: System Level Control/Status Commands
SCPI Command Description
:SYSTem Page 47
:ABORt Aborts the current data capturing process and puts the RTSA system into
a normal manual mode (i.e. sweep, trigger, and streaming will be aborted)
:CAPTure
:MODE? Gets the current capture mode of the RTSA (i.e. sweeping, streaming or
block mode)
13 ThinkRF R5500/R5550 Real Time Spectrum Analyzer Programmer's Guide

R5500/R5550 Functional Overview
SCPI Command Description
:COMMunicate
:HISLip
:SESSion? Returns the HiSLIP connection’s session ID
:LAN<commands> Subset of commands for configuring/querying RTSA's LAN settings
:ERRor
[:NEXT]? Returns the next error code and message from the SCPI error/event
queue
:ALL? Returns all the error codes and messages from the SCPI error/event
queue
:CODE
[:NEXT]? Returns next the error code from the SCPI error/event queue
:ALL? Returns all the error codes from the SCPI error/event queue
:COUNt? Returns the number of errors in the SCPI error/event queue
:FLUSh Clears the R55x0's internal data storage buffer of any remaining data that
has not transferred out of the RTSA
:LOCK
:HAVE? Returns the current lock state of the task specified
:REQuest? Requests the R55x0 to provide a lock on a specific task such that only the
application that has the lock can perform the task
:OPTions? Returns comma separated 3-digit values to represent the hardware
option(s) or features available with a particular RTSA model
:SYNC
:MASTer[?] Sets an RTSA unit to be the master or slave for a synchronization trigger
system with multiple units. Affects :TRIGger:TYPE PULSe or WORD.
:WAIT[?] Sets the delay time in nanoseconds that the system must wait after
receiving the trigger signal before performing data capture
:VERSion? Returns the SCPI version number that the instrument complies with
:DATE[?] Sets/reads date
:TIME[?] Sets/reads time
:ADJust Adjust the system time relative to its current time
:SYNC[?] Sets/ gets the System time synchronization source via network or SCPI,
or disable
:STATus? Status of the time synchronization
:STATus Page 59
:OPERation
[:EVENt]? Queries the Operation Status Register for any operation event
:CONDition? Queries the Operation Condition Register for any operation event
:ENABle[?] Enables or queries bits in the Operation Enable Register
:NTRansition[?] Enables or queries bits in the Operation Negative Transition Register
:PTRansition[?] Enables or queries bits in the Operation Positive Transition Register
:PRESET Presets the R55x0 (similar to *RST)
:QUEStionable
[:EVENt]? Queries the Questionable Status Register for any questionable event
:CONDition? Queries the Questionable Condition Register for any questionable event
:ENABle[?] Enables or queries bits in the Questionable Enable Register
ThinkRF R5500/R5550 Real Time Spectrum Analyzer Programmer's Guide 14

R5500/R5550 Functional Overview
SCPI Command Description
:NTRansition[?] Enables or queries bits in the Questionable Negative Transition Register
:PTRansition[?] Enables or queries bits in the Questionable Positive Transition Register
:TEMPerature? Returns the R55x0's internal ambient temperature
See SCPI Command Set section (page 43 onward) for further details on the commands.
Caution pertaining to multi-users: See Appendix A: Connecting to RTSA for important
notes on this caution.
The Architecture
The R55x0 is an integrated wireless radio receiver and digitizer/analyzer. It has an
embedded capture controller that enables users to:
•define and execute real-time and sophisticated triggers, traces and sweeps;
•configure the radio RFE and DSP in association with those traces or sweeps; and
•time-stamping and data output for captures.
Traces and sweeps are controlled by the capture controller as illustrated in the Digitizer
portion of Figure 2. A trace and a sweep are defined as a single (block or continuously
streamed) capture and a series of captures, respectively, each with their associated
hardware configurations.
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R5500/R5550 Functional Overview
Figure 2: RF Receiver Front-end and Capture Controller Functional Block Diagram
(Note: The GPS (GNSS) o tion is not included in R55x0)
The R55x0 supports different RFE modes of operation and subsequent DSP capabilities
as per Table 2 and as described in the following subsections.
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R5500/R5550 Functional Overview
Table 2: Radio RFE Modes and DSP Data Output Formats
ode1Description Freq
Range
(MHz)
IBW4
(MHz)
Ouput
Format
No DSP
DSP Data Output Format
Decim-
ation
Frequency
Shift
IBW4
(MHz)
ZIF Zero-IF Receiver 50 - max 100 I14 Q14 I14 Q14 I14 Q14 100 /
decimation
SH Super-
Heterodyne
Receiver
50 - max 40 I14 I14 Q142I14 Q14 100 /
decimation
SHN SH Receiver with
narrower BW
50 - max 10 I14 I14 Q142I14 Q14 100 /
decimation
HDR High Dynamic
Range Receiver
50 - max 0.1 I24 – – –
DD Direct
Digitization
Receiver
0.009 -
503
50 I14 I14 Q14 I14 Q14 No shifting:
50 / dec
With shifting:
100 / dec
HIF High IF Receiver 50 - max – – – – –
1 The RFE Mode availability is product dependent.
2 For SH and SHN modes, when the decimation is used, a frequency shift will be applied
automatically to bring the R55x0's center frequency back to the zero IF. Thus, the data output will
be I and Q.
3 In DD mode, there is no frequency tuning except for performing frequency shift. When
decimation is applied, the decimation will be around the DD’s center frequency of 0 Hz, plus the
frequency shift value when used.
4 IBW here refers also to the usable operating BW of the full hardware BW (which is of the sample
rate, varies depending on the RFE mode and I/Q format).
R55x0 complies to VRT protocol for sending digitized IF data packets and their
associated context information depending on the capture mode. It is very important to
follow the VRT's IF Data Packet Class section (page 37) for the exact VRT data output
formats as well as packing method.
RF Receiver Front-End
The Receiver portion of Figure 2 shows a block diagram of the RFE within the R55x0.
The architecture consists of a super-heterodyne (SH) front-end with a back-end that
utilizes an I/Q mixer similar to that in a direct-conversion (or zero-IF) receiver.
Depending on the frequency of the signals being analyzed, one of the three receiver
signal processing paths is selected. Signals in the frequency range 9kHz to 50MHz are
directly digitized, while all other signals are translated to the frequencies of the first IF
block via one of the other two signal processing paths. The IF block consists of a bank of
multiple SAW filters. SAW filter selection depends on the frequency of the input signal.
The output of the SAW filter feeds the I/Q mixer.
The three signal processing paths are further classified into different modes of operation
for the capture engine as shown in Table 2. The radio modes ZIF, SH, SHN and HDR
support tuning the center frequency from 50MHz to the maximum frequency supported by
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R5500/R5550 Functional Overview
the particular product model (ex. 8GHz, 18GHz, and 27GHz for R55x0-x08, -x18, and -
x27, respectively, where x is a model number variant).
The ZIF, SH and SHN radio modes support a tuning resolution of 10Hz. Digital
frequency shifting is then used to enhance the tuning resolution to the nearest 1Hz
(±0.23Hz). The frequency shifting technology used is an embedded Numerically
Controlled Oscillator (NCO) (a Direct Digital Synthesizer or DDS) as described in the
Digital Down Converter subsection (page 20).
The HDR radio mode supports a tuning resolution of 10Hz. No further fine tuning is
available.
The remaining radio mode, DD, support 50MHz IBW direct digitization of the baseband
from the external RF IN. Hence, this mode does not support frequency tuning of the
radio although the DSP's frequency shift mode may be applied.
Direct-Conversion Receiver Technology
Direct-conversion (or ZIF) receivers are ideal for signal analysis of wideband waveforms,
such as 4G/5G/LTE, Wi-Fi and Bluetooth. With that benefit comes the drawback of both
IQ and DC offsets which are inherent to direct-conversion technology.
DC Offset Correction
The R55x0's WB ADC sampling rate is 125 MSa/s, intermediate frequency (IF) is 0 and
the entire IF bandwidth is 125MHz. The analog filter results in an amplitude roll-off at
approximately +50MHz around the center frequency Fc, as illustrated in Figure 3.
Direct-conversion receivers have a DC offset at the center of the band. The offset is
primarily compensated for in real-time in the receiver hardware but there always is some
residual offset that (depending on the application and bandwidth of interest) might need
to be compensated for in software. Several options such as calibration or dynamic offset
compensation in software have been described in the open literature.
D C
O f f s e t
F c - 5 0 M H z F c + 5 0 M H z
1 2 5 M H z
F c
A n a l o g f i l t e r
Figure 3: DC Offset with Amplitude Roll-Off at +50MHz
If the application only needs to utilize up to 50MHz of IBW, a simple alternative to DC
offset compensation is to use the SH mode of operation.
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R5500/R5550 Functional Overview
IQ Offset Correction
Direct-conversion receivers have phase and/or amplitude offsets between in-phase (I)
and quadrature (Q) components of the baseband signal. Due to this, when an FFT is
performed on digitized baseband data where there is a signal tone present, there will be
an ‘image’ at the same frequency offset from the center frequency as the tone itself. This
is illustrated in Figure 4.
S i g n a l
I m a g e
X d B
F r e q u e n c y
F
c
F r e q u e n c y
F
c
F c + F s
F c - F s
c a l i b r a t e I Q
Figure 4: IQ Offset Correction
A correction algorithm would be needed to adjust this offset necessary for signal analysis,
especially for the ZIF mode. The ThinkRF's APIs have included a correction.
Table 3: RF Front-End Control/Status Commands
SCPI Command Description
:INPut Page 64
:ATTenuator[?] Enables/disables the front-end's attenuation for R55x0-304, -408 & their
variants only
:VARiable[?] Sets the variable attenuation for R55x0-418 and -427 & their variants
:GAIN[?] Sets the input gain stage for R55x0-418, -427 & their variants
:HDR[?] Sets gain level for the NB ADC of of the HDR signal path
:MODE[?] Selects the receiver mode of operation
:SOURce Page 67
:REFerence
:PLL[?] Selects the 10MHz reference clock source
[:SENSe] Page 67
:DECimation[?] Sets the decimation rate as an exponent of 2 (i.e. rate = 2level where
level = 0, 1, 2 - 10)
:FREQuency
:CENTer[?] Sets the center frequency of the RFE
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R5500/R5550 Functional Overview
SCPI Command Description
:IF? Queries the IF frequencies that are used for the current input mode and
center frequency
:INVersion? Queries if a spectral inversion is required at a given frequency
:LOSCillator? Gets the frequency of the external LO 1, 2 or 3 in corresponding to
current the RTSA's center frequency
:SHIFt[?] Sets the frequency shift value (not available for HDR mode)
:LOCK
:REFerence? Queries the lock status of the PLL reference clock
:RF? Queries the lock status of the RFE's PLL
:OUTput Page 71
:MODE[?] Selects the IQ output path to be from the external connector or the
digitizer
See SCPI Command Set section (page 43 onward) for further details on each set of
commands.
Digital Signal Processing
The R55x0 has embedded DSP blocks to provide further signal processing capabilities,
such as DDC with up to 10 levels of decimation and FFT computation.
Digital Down Converter
The DDC block takes the frequency band of interest and shifts it down in frequency, then
provides decimation of the sampling rate to one that is lower and consistent with the
bandwidth of the signal of interest. This enables channelization of signals having
bandwidth smaller than the IBW.
Referring to Figure 5, the DDC has two major elements, an NCO (DDS) and a down
sampling with filtering. The NCO generates a complex sinusoid, which is mixed with the
IQ input using a complex multiplier, to shift or offset the signal spectrum from the selected
carrier frequency. This process provides the frequency fine-tuning (and shifting) feature
as mentioned in the previous subsections.
ThinkRF R5500/R5550 Real Time Spectrum Analyzer Programmer's Guide 20