Keysight 775D Service manual

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Keysight 775D
Dual Directional Couplers
Operating and
Service Manual

ii 775D Operating And Service Manual
Notice
The information contained in this document is subject to change without
notice.
Keysight Technologies makes no warranty of any kind with regard to this
material, including, but not limited to, the implied warranties of
merchantability and fitness for a particular purpose. Keysight Technologies
shall not be liable for errors contained herein or for incidental or
consequential damages in connection with the furnishing, performance, or
use of this material.
Keysight Technologies assumes no responsibility for the use or reliability of
its software on equipment that is not furnished by Keysight Technologies.
This document contains proprietary information which is protected by
copyright. All rights are reserved. No part of this document may be
photocopied, reproduced, or translated to another language without prior
written consent of Keysight Technologies.
RESTRICTED RIGHTS LEGEND
Use, duplication, or disclosure by the U.S. Government is subject to
restrictions as set forth in subparagraph (c)(1)(ii) of the Rights in Technical
Data and Computer Software clause at DFARS 252.227-7013 for DOD
agencies, and subparagraphs (c)(1) and (c)(2) of the Commercial Computer
Software Restricted Rights clause at FAR 52.227-19 for other agencies.
Keysight Technologies
1400 Fountaingrove Parkway
Santa Rosa, CA 95403-1799, U.S.A.

775D Operating And Service Manual iii
In This Manual…
•Overview, page 1
•Specifications, page 2
•Unpacking and Setup, page 3
•Applications, page 6
•Performance Tests, page 10
•Directivity Test, page 12
•Primary-Line SWR Test, page 14
•Swept-Frequency Test, page 14
•Fixed-Frequency Test, page 15
•Auxiliary Arm SWR Test, page 17
•Fixed-Frequency Auxiliary-Arm SWR Test, page 19
•Coupling Test, page 21
•Insertion Loss Test, page 23

iv 775D Operating And Service Manual
Warranty
Custom systems are warranted by contractual agreement between
Keysight Technologies and the customer.
Certification Keysight Technologies certifies that this product met its published
specifications at the time of shipment from the factory. Keysight
Technologies further certifies that its calibration measurements are
traceable to the United States National Institute of Standards and
Technology (NIST, formerly NBS), to the extent allowed by the Institute’s
calibration facility, and to the calibration facilities of other International
Standards Organization members.
Warranty This Keysight Technologies system product is warranted against defects in
materials and workmanship for a period corresponding to the individual
warranty periods of its component products. Instruments are warranted for a
period of one year. During the warranty period, Keysight Technologies will,
at its option, either repair or replace products that prove to be defective.
Warranty service for products installed by Keysight Technologies and
certain other products designated by Keysight Technologies will be
performed at Buyer’s facility at no charge within Keysight Technologies
service travel areas. Outside Keysight Technologies service travel areas,
warranty service will be performed at Buyer’s facility only upon Keysight
Technologies’ prior agreement and Buyer shall pay Keysight Technologies’
round trip travel expenses. In all other areas, products must be returned to a
service facility designated by Keysight Technologies.
For products returned to Keysight Technologies for warranty service, Buyer
shall prepay shipping charges to Keysight Technologies and Keysight
Technologies shall pay shipping charges to return the product to Buyer.
However, Buyer shall pay all shipping charges, duties, and taxes for products
returned to Keysight Technologies from another country.
Keysight Technologies warrants that its software and firmware designated
by Keysight Technologies for use with an instrument will execute its
programming instructions when properly installed on that instrument.
Keysight Technologies does not warrant that the operation of the
instrument, or software, or firmware will be uninterrupted or error free.
LIMITATION OF WARRANTY. The foregoing warranty shall not apply
to defects resulting from improper or inadequate maintenance by Buyer,
Buyer-supplied software or interfacing, unauthorized modification or
misuse, operation outside of the environmental specifications for the
product, or improper site preparation or maintenance.

775D Operating And Service Manual v
NO OTHER WARRANTY IS EXPRESSED OR IMPLIED. KEYSIGHT
TECHNOLOGIES SPECIFICALLY DISCLAIMS THE IMPLIED
WARRANTIES OR MERCHANTABILITY AND FITNESS FOR A
PARTICULAR PURPOSE.
EXCLUSIVE REMEDIES. THE REMEDIES PROVIDED HEREIN ARE
BUYER’S SOLE AND EXCLUSIVE REMEDIES. KEYSIGHT
TECHNOLOGIES SHALL NOT BE LIABLE FOR ANY DIRECT,
INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES,
WHETHER BASED ON CONTRACT, TORT, OR ANY OTHER LEGAL
THEORY.
YEAR 2000. Keysight Technologies warrants that each Keysight Technologies
hardware, software, and firmware product on Keysight Technologies’
Corporate Price List (dated July 1, 1998 or later) delivered under the product’s
contract of sale will be able to accurately process date data
(including, but not limited to, calculating, comparing, and sequencing) from,
into, and between the twentieth and twenty-first centuries, and the years 1999
and 2000, including leap year calculations, when used in accordance with the
product documentation provided that all other products (that is, hardware,
software, firmware) used in combination with such Keysight Technologies
product(s) properly exchange date data with it. If the agreement requires that
specific Keysight Technologies products must perform as a system in
accordance with the foregoing warranty, then that warranty will apply to those
Keysight Technologies products as a system, and Customer retains sole
responsibility to ensure the year 2000 readiness of its information technology
and business environment. The duration of this warranty extends through
January 31, 2001.
The remedies available under this warranty will be defined in, and subject to,the
terms and limitations of the warranties contained in the contract of sale. To the
extent permitted by local law, this warranty applies only to branded Keysight
Technologies products and not to products manufacture by others that may be
sold or distributed by Keysight Technologies. Nothing in this warranty will be
construed to limit any rights or remedies provided elsewhere in the contract of
sale with respect to matters other than year 2000 compliance.
Assistance Product maintenance agreements and other customer assistance agreements
are available for Keysight Technologies products.
For assistance, call your local Keysight Technologies Sales and Service
Office (refer to “Service and Support” on page vi).

vi 775D Operating And Service Manual
Service and Support
By internet, phone, or fax, get assistance with all your test and measurement needs.
Online assistance: www.keysight.com/find/assist
United States
(tel) 1 800 452 4844 Latin America (tel) [phone]
(fax) [phone]
Canada
(tel) 1 877 894 4414
(fax) [phone]
Europe
(tel) ([phone]
(fax) ([phone]
New Zealand
(tel) 0 800 738 378
(fax) ([phone]
Japan
(tel) ([phone]
(fax) ([phone]
Australia
(tel) 1 800 629 485
(fax) ([phone]
Asia Call Center Numbers
Country Phone Number Fax Number
Singapore 1-800-375-8100 (65) 836-0252
Malaysia 1-800-828-848 1-800-801664
Philippines (632) 8426802
1-800-16510170 (PLDT Subscriber Only) (632) 8426809 1-800-16510288 (PLDT
Subscriber Only)
Thailand [phone] (outside Bangkok)
[phone] (within Bangkok) (66) 1-661-3714
Hong Kong 800-930-871 (852) 2506 9233
Taiwan 0800-047-866 (886) 2 25456723
People’s Republic of
China 800-810-0189 (preferred) 10800-650-0021 10800-650-0121
India 1-600-11-2929 000-800-650-1101

775D Operating And Service Manual vii
Safety and Regulatory Information
Review this product and related documentation to familiarize yourself with
safety markings and instructions before you operate the instrument. This
product has been designed and tested in accordance with international
standards.
WARNING The WARNING notice denotes a hazard. It calls attention to a procedure,
practice, or the like, that, if not correctly performed or adhered to, could result
in personal injury. Do not proceed beyond a WARNING notice until the
indicated conditions are fully understood and met.
CAUTION The CAUTION notice denotes a hazard. It calls attention to an operating
procedure, practice, or the like, which, if not correctly performed or adhered
to, could result in damage to the product or loss of important data. Do not
proceed beyond a CAUTION notice until the indicated conditions are fully
understood and met.
Instrument Markings
When you see this symbol on your instrument, you should refer to the instrument’s
instruction manual for important information.
This symbol indicates hazardous voltages.
The laser radiation symbol is marked on products that have a laser output.
This symbol indicates that the instrument requires alternating current (ac) input.
The CE mark is a registered trademark of the European Community. If it is
accompanied by a year, it indicates the year the design was proven.
The CSA mark is a registered trademark of the Canadian Standards Association.
1SM1-A This text indicates that the instrument is an Industrial Scientific and Medical Group 1
Class A product (CISPER 11, Clause 4).
This symbol indicates that the power line switch is ON.
This symbol indicates that the power line switch is OFF or in STANDBY position.
!

viii 775D Operating And Service Manual
Safety Earth
Ground This is a Safety Class I product (provided with a protective earthing
terminal). An uninterruptible safety earth ground must be provided from the
main power source to the product input wiring terminals, power cord, or
supplied power cord set. Whenever it is likely that the protection has been
impaired, the product must be made inoperative and secured against any
unintended operation.
Before Applying Power Verify that the product is configured to match the available main power
source as described in the input power configuration instructions in this
manual. If this product is to be powered by autotransformer, make sure the
common terminal is connected to the neutral (grounded) side of the ac power
supply.

775D Operating and Service Manual 1
Overview
The Keysight 775D dual directional couplers are three-port passive devices
for use in 7-mm, 50-ohm systems. A coupler is essentially a device for
sampling power flowing in one direction in a transmission line. Since no
coupler is perfect, some power flowing in the opposite (unwanted) direction
is also sampled. The rejection of power flowing in the unwanted direction is
called directivity and is the most important specification of a directional
coupler. The 775D dual directional coupler also has forward coupling
attenuation (usually called just coupling) which is the fractional amount of
power transferred in the wanted direction. These terms are defined in
Figure 2, which also shows a typical coupling curve.
NOTE This curve is not a specification.
Port Terminology The two directly-connected ports (on opposite ends of the coupler) are the
primary line ports. The coupled ports on each side are the auxiliary ports.
Coupling is in the direction of the arrows on the nameplate. These coupled
ports are called auxiliary line ports.
Accessories Available Two shorting connectors, Keysight 11511A Type N female short and
11512A Type N male short, are available as accessories.
Figure 1 Type N Connector Dimensions

2775D Operating and Service Manual
Specifications
Specifications
Specifications for the 775D are shown in Table 1.
Table 1 Specifications
Characteristic Value
Frequency range 450 to 940 MHz
Minimum directivity1
1. Measured with Keysight H02-909A (male) or H03-909A (female) termination.
40 dB
Coupling attenuation (each secondary arm) 20 dB (nominal)
Accuracy of coupling (each secondary arm) Mean coupling level within 0.5 dB of 20 dB
Maximum coupling variation ±1 dB
Maximum primary-line SWR1
(50-ohm terminations) 1.15
Maximum auxillary-arm SWR
(50-ohm terminations) 1.20
Primary-line power handling capacity 50 watts average, 10 kW peak
Primary-line insertion loss ≤0.4 dB
Primary-line connectors Type N connectors one male and one female2
2. Compatible with connectors whose dimensions conform to MIL-C-39012 or MIL-C-71.
Auxiliary-arm connectors Type N female connectors 2
Dimensions 9.0625 in x 3.1250 in x 1.7500 in
230 mm x 79 mm x 45 mm
Weight (net) 3 lb (1.4 kg)

775D Operating and Service Manual 3
Unpacking and Setup
Unpacking and Setup
Initial Inspection
Mechanical Check If damage to the shipping carton is evident, ask that the carrier’s agent be
present when the coupler is unpacked. Inspect the parts for mechanical
damage, such as scratches or dents. Also check the cushioning material for
signs of severe stress (compacting).
Electrical Check The electrical performance should be verified as soon as possible after
receipt. Refer to the performance test for further information.
Claim for Damage If a coupler is mechanically damaged or fails to meet specifications upon
receipt, notify the carrier and your nearest Keysight Technologies Office
immediately (a list of Keysight Technologies offices is at the end of this
operating note). Retain the shipping carton and the padding material for the
carrier’s inspection.
Repackaging for
Shipment
Using Original-Type
Packaging Containers and materials like those used in factory packaging can be
obtained through Keysight Technologies offices listed at the end of
this operating note.
If the coupler is being returned to Keysight for servicing, attach a tag
indicating the type of service required; return address, model number, and
serial number. Also, mark the container FRAGILE to assure careful
handling.
In any correspondence refer to the instrument by model number and serial
number.
Using Other Packaging The following general instructions should be used for repackaging with
commercially available materials.
1. Wrap the coupler in heavy paper or plastic (if shipping to a Keysight
Technologies office attach a tag indicating the type of service required,
return address, model number, and serial number).
2. Use a strong shipping container. A double wall carton made of
350-pound test material is adequate.

4775D Operating and Service Manual
Unpacking and Setup
3. Use enough shock-absorbing material (3 to 4 inch layer) around all sides
of the coupler to provide firm cushion and prevent movement inside the
carton.
4. Seal the shipping carton securely.
5. Mark the shipping carton FRAGILE to assure careful handling.
Setup Precautions
Connectors The Type N connectors used on these couplers will mate with all other Type
N connectors whose dimensions conform to MIL-C-71B and MIL-C-39012.
Do not mate with the male Type N connector on 775D’s with serials below
3141 (see caution below). See Figure 1 for dimensions.
CAUTION Do not mate with 0.071" diameter pin male connectors. Damage may result.
When installing be sure auxiliary equipment supports its own weight. The
coupler, particularly the connectors, is not designed to carry weight.
CAUTION Do not drop the coupler. While the coupler probably will not break, it can be
jarred out of adjustment and the connectors can be damaged.
Ambient Conditions Do not heat cycle this coupler during use or storage. Keep coupler near room
temperature (25°C). Coupler will stand relative humidity of 95% but will be
affected by condensation (keep at room temperature).
Signal Flow Signal flow is indicated in Figure 2. Coupling is indicated by arrows. This
coupler is bi-directional (signal may go through the coupler in either
direction).

775D Operating and Service Manual 5
Unpacking and Setup
Figure 2 775D Coupler Terminology

6775D Operating and Service Manual
Applications
Applications
Introduction The 775D couplers are usually used in a reflectometer. Figures 3, 4, 5, and 6
illustrate typical setups. Note that a line stretcher (or a longer length of
cable) must be used with vector voltmeters or network analyzers to balance
the two signal paths in the coupler for zero phase reference.
Complementary
Equipment Figure 3, 4, 5 and 6 show Keysight equipment suitable for use with the
775D couplers.
Error Analysis There are certain errors present in all reflectometer systems. Usually the
most significant error is that caused by the directivity of the directional
coupler. The magnitude of this error can be measured accurately over the
frequency band (see Directivity Test, page 12). Once the directivity is
known, the ambiguity of any measurement can be determined with the
reflectometer calculator obtainable from Keysight Technologies (part
number 5952-0948).
Error also results from multiple reflections or mismatch losses of the
components of the reflectometer system. The ambiguity introduced by this
error can also be calculated with the reflectometer calculator mentioned
above.
Power Measurement The 775D may also be used for measuring power as shown in Figure 6. Here
the coupler samples primary-line power and a coaxial thermistor mount is
used as a power-detecting device. The coupler can also be used for
measuring peak power up to 10 kW, provided average power remains below
the rating of the coupler (50 W) and the sampled pulses are attenuated to the
power-handling capability of the thermistor mount.
When monitoring power with this coupler keep in mind that the output
power is the coupling (20 dB nominally) above the power sampled at the
auxiliary port. For very precise work, the insertion loss of the coupler
(attenuation of primary line) must be subtracted from the calculated output
power.

775D Operating and Service Manual 7
Applications
Figure 3 Typical Reflectometry Setup
Figure 4 Setup for Impedance Measurement

8775D Operating and Service Manual
Applications
Figure 5 Network Analyzer in Reflectometer Setup
Figure 6 Power Measuring Setup
The couplers can be used not only for power measurement, but for system
adjustment for best power transfer as well. This adjustment can be made
easily with the setups of Figure 3, 4, or 5. This adjustment can also be made
with only a power meter and a coupler. Alternately connect the thermistor
mount first to the incident auxiliary arm and then to the reflected auxiliary
arm. Connect first as shown in Figure 6. Take a reading, then interchange the
thermistor mount and the load and take another reading. Adjust the system
for a maximum incident/reflected power ratio.

775D Operating and Service Manual 9
Applications
Power Leveling The 775D can also be used for power leveling, if a single directional coupler
is not available. Connect as shown in the left half of Figure 3. Terminate the
unused auxiliary arm with a 50-ohm termination.