Agilent Technologies 11867A? Service manual

Agilent Technologies
Agilent
11867A
RF Limiter




Operating and Service Guide

Notices
© Agilent Technologies, Inc. 1995, 2001,
2013
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laws.
Manual Part Number
11867-90005
Edition
October 2013
Supersedes: November 2001

Agilent Technologies, Inc.
5301 Stevens Creek Blvd
Santa Clara, CA 95051
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11867A Operating and Service Guide 1
11867A RF Limiter
General Information
To obtain optimum performance from this RF limiter, observe these simple precautions:
• Make connections carefully to avoid misalignment and connector damage, which will result in
inaccurate measurements.
• Keep the connectors free of dirt and any particles.
• When you clean the connectors, try using compressed air first. Do not use abrasives. With a clean foam
swab, apply only isopropyl alcohol.
• For more information, refer to the Connector Care for RF and Microwave Coaxial Connectors document. It
can be viewed online by searching for part number 08510-90064 at www.agilent.com.
Introduction
The 11867A RF limiter is an instrument accessory that can be used to protect input circuitry from transients
and accidental overloads. This manual explains how to use the limiter, briefly describes tests that can be
used to verify the specifications, and explains how to repair the limiter.
Instrument specifications are listed in Table 1. These specifications are performance standards or limits
against which the instrument may be tested.
Tabl e 1 11867A RF Limiter Specifications
Frequency Range 10 Hz to 1800 MHz
Insertion Loss <1.0 dB
Frequency Responsea
a. For operation to 2.4 GHz, see typical response shown in Figure 1.
<±0.25 dB about a 0.25 dB/GHz slope
Maximum Input Power Levels --
Continuous 10 watts average (+40 dBm); 
<1.3 Vdc with no RF applied; 
0.0 Vdc with RF applied
Pulse 100 watts peak, pulse width sec, 0.001 duty cycle
Limiting Threshold 1 mW (0 dBm) gives approximately 1 dB compression
Impedance 50 ohm nominal
Reflection Coefficient <0.13 (1.3:1 VSWR)
RF Input Connectorb
b. Device is not suitable for bilateral operation. Input and output may not be interchanged.
Type-N female
RF Output ConnectorbType-N male
Weight 90 grams (0.2 lb)
Dimensions 21 mm x 60 mm (0.81 in. x 2.38 in.)

2 11867A Operating and Service Guide
Figure 1 Typical Insertion Loss Versus Frequency
Description
The 11867A RF limiter is a unidirectional, solid state, passive device for use from 10 Hz to 1800 MHz. It
consists of four oxide-passivated silicon diodes: two PIN diodes and two Schottky-Barrier diodes. These
diodes are functionally integrated in a 50 ohm transmission line as part of a low pass filter with a cutoff
frequency (Fc) of approximately 2.5 GHz. The limiter has no adjustments, and its diodes are not field
replaceable.
For noise considerations, the limiter behaves as a thermal resistance shunted across the transmission line.
The excess noise temperature is less than 20Kelvin. This results in a noise figure that is essentially equal
to the insertion loss below the limiting threshold. (Figure 1 shows typical insertion loss below the limiting
threshold.)
The VSWR specification in Table 1 applies below the limiting threshold. (Typical VSWR into either port is
shown in Figure 2.) VSWR above the threshold is unpredictable, since the limiter effects its limiting by
reflecting some of the input power.
Limiting is non-linear and depends on input power and ambient temperature. The typical limiting curves
shown in Figure 3 apply at an ambient temperature of 25C.

11867A Operating and Service Guide 3
Figure 2 Typical Return Loss Versus Frequency
Figure 3 Typical Output Power Versus Input Power at 25C

4 11867A Operating and Service Guide
Installation
Initial Inspection
Verify that the shipment is complete by referring to the contents list in the shipping container.
If the container or device appears damaged, or if the shipment is incomplete, contact Agilent Technologies
— see “Contacting Agilent” on page 8. Agilent will arrange for repair or replacement of incomplete or
damaged shipments without waiting for a settlement from the transportation company.
Electrical Inspection
VSWR To check that the limiter meets the VSWR specification listed in Ta b le 1, use any test system that
can measure return loss. Terminate the unused port with an accurate 50 ohm termination. Incident power
must be less than 1 mW (the limiting threshold).
Insertion Loss and Frequency Response To check that the limiter meets the insertion loss and frequency
response specifications listed in Ta b l e 1 , use any test system that can measure insertion loss. The input and
output ports must be provided with a good 50 ohm match. Incident power must be less than 1 mW (the
limiting threshold).
CAUTION During the test of limiting specifications, do not apply more than 10W average power to the
limiter. There should be <1.3 Vdc with no RF applied, and 0.0 Vdc when RF is applied.
Permanent damage to the diodes could result from exceeding these levels.
Limiting The power limiting performance can be compared against the typical performance shown in Figure
3by using the same test system that is used to check insertion loss. Incident power should be slowly
increased from below 1 mW to 10 W while the output power is observed.
Storage Environment
The limiter should be stored in a clean, dry environment with the following environmental limitations:
•Temperature:–40C to +75C
• Humidity: <95% relative
• Altitude: <7620 meters (25,000 feet)
Operation
Operating Environment
The operating environment should be with the following limitations:
•Temperature:0C to +55C
• Humidity: <95% relative
• Altitude: <4572 meters (15,000 feet)

11867A Operating and Service Guide 5
Mating Connectors
Mating connectors used with the limiter should be Type-N connectors that are compatible with US
MIL-C-39012.
Instructions
CAUTION Do not apply more than 10 W average power or 100 W peak power to the limiter. There
should be <1.3 Vdc with no RF applied, and 0.0 Vdc when RF is applied. Permanent damage to
the diodes could result from exceeding these levels.
For reliable operation over its full frequency and power range, the limiter must be used as a unidirectional
device. Incident power must be applied as shown on the label of the limiter. The limiter can be used to
protect the input mixer of a spectrum analyzer, the sampler of a network analyzer, the power sensor (or
thermistor mount) of a power meter, or the input circuitry of any other device that might be subjected to
transients and accidental overloads.
The use of an attenuator between the limiter and the device it is protecting is recommended to minimize
measurement uncertainty that is due to multiple mismatches. For example, set the input attenuator of a
spectrum analyzer to at least 10 dB.
Harmonic distortion is generated by the limiter while it is limiting. If the incident signal exceeds the limiting
threshold, use attenuation between the limiter and the source to reduce the signal below 1 mW. Typical
harmonic distortion below the limiting threshold is shown in Figure 4. The limiter will still prevent transients
from damaging the device it is protecting.

6 11867A Operating and Service Guide
Figure 4 Typical Harmonic Distortion Versus Input Power
Repair
Diodes
If the diodes of the limiter fail to function correctly or have been damaged, return the limiter to Agilent
Technologies for repair – see“Contacting Agilent” on page 8. Do NOT attempt to remove or replace the
diodes.
Connectors
If a connector is damaged or worn, it can be disassembled, the worn or damaged parts replaced, and the
connector reassembled.
To disassemble a connector, carefully remove the label, place the limiter in a vise, and remove the connector
body, which has right-hand threads. Replace the worn or damaged part (see Figure 5) and reassemble the
connector.

11867A Operating and Service Guide 7
Figure 5 11867A Illustrated Parts Breakdown
Tabl e 5 11867A Illustrated Parts Breakdown
Item Description Part Number
1Nut, RF Connector 1250-0918
2Ring, RF Connector, Series N 1250-0016
3Housing, Male Connector 08491-2100
4Pin Assembly, Male 08491-4000
5Spacer 08491-20003
6 Plug 11867-20001
7Contact, Elastomer 8160-0729
8Limiter Assembly (not field replaceable) --
9Spacer 08491-20003
10 Pin Assembly, Female 08491-4001
11 Connector, Female 08491-2101
12 Spacer, Outer Conductor (optional, not shown) 08742-0006

8 11867A Operating and Service Guide
Contacting Agilent
Assistance with test and measurement needs and information on finding a local Agilent office are available
on the Web at:
www.agilent.com/find/assist
NOTE In any correspondence or telephone conversation, refer to the Agilent product by its model
number and full serial number. With this information, the Agilent representative can
determine whether your product is still within its warranty period.