Dual Directional Coupler 100 to 2000 MHz
Data Sheet
Features
• Multi-octave frequency range: 100 to 2000 MHz• High directivity: 36 dB to 1 GHz, 32 dB to 2 GHz
• Reflection coefficient measurement: Over 4 octaves with 1 coupler
Broadband 20 dB Dual Directional Coupler
This dual directional 20 dB coupler has a frequency range extending over 4 octaves from 100 MHz to 2 GHz. The multi-octave capability makes measurements easier–setup and calibration time are reduced, since normally several couplers are required over this frequency band. The coupling factor increases about 6 dB per octave below 100 MHz; thus, usefulness below this frequency is restricted only by the amount of signal source power and/or the sensitivity of the RF detector con-nected to the coupler. Figure 1 shows typical coupling and directivity characteristics of the 778D.
Simultaneous Reflection and Transmission Measurements
The 778D is ideal for measuring the reflection and transmission characteristics of a device from 100 MHz to 2000 MHz. Figure 2 shows a test configuration in which a 778D dual directional coupler is used to separate and isolate the incident, reflected, and transmitted signals in a swept-frequency measurement. These signals are detected and their ratio displayed on a CRT. This coupler is an ideal companion for the Agilent 8755 frequency response test set, a detection and display system operating from 15 MHz to 18 GHz.
The high directivity and close tracking of the auxiliary arms of this couplermake it particularly useful for this type of broadband measurement. The highdirectivity insures accurate measurements by a true separation of the forwardand reflected signals. Close tracking of signal variation from the auxiliary arms gives a flat frequency response that makes display readings easy to interpret.
Figure 1. Coupling and directivity characteristics of the 778D coupler.
Figure 2. Setup diagram for simultaneous measurements of insertion and return loss.
Maximum amplitude errors in a reflection measuring system are shown in thefollowing table
Maximum magnitude error ∆GLFrequency range 0.1 to 1 GHz 1 to 2 GHz
Swept frequency± (0.015 + 0.02 |GL| + 0.05 |GL|2)± (0.025 + 0.02 |GL| + 0.05 |GL|2)
Fixed frequency± (0.015 + 0.05 |GL|2)± (0.025 + 0.05 |GL|2)
Maximum phase error = ±sin-1 (∆GL/GL)
|GL|= reflection coefficient of unknown
2
Impedance Measurements
System Monitoring
Choice of Output Connectors
Error components include a fixed term due to coupler directivity, and severalGL -dependent terms relating to source match and reference setting (detectionerrors are not included). These errors apply over broad swept-frequency bands.Somewhat improved accuracy can be achieved by simple recalibration at thefrequency of interest.
The 778D is also well suited for measurements of impedance when used withthe Agilent 8405A vector voltmeter. The technique is described in ApplicationNote 77-3, Measurement of Complex Impedance, available at your nearestAgilent sales office. Again, a reflectometry technique is used. With the vectorvoltmeter, however, both magnitude and phase angle of the reflection coefficientcan be measured. This setup is shown in Figure 3.
Figure 3. Setup of impedance measurement of coaxial devices from ~10 to 1000 MHz.
Data can be read from the two meters of the vector voltmeter and transferreddirectly to a Smith Chart to provide impedance of such devices as antennas orother passive components. In addition, with an appropriate bias supply, activecomponents, such as transistors, can also be quickly measured and character-ized with this setup. The 778D is well-suited for these types of measurementssince both the phase and the magnitude variation between the two couplingarms have been closely controlled in the design of the coupler.
Because of the high power capability of the dual directional coupler, it canbe permanently installed in coaxial systems to monitor the power traveling inboth directions simultaneously. This enables a system to be continually moni-tored to indicate whether the system is in need of adjustment or maintenancedue to excessive standing-wave rations on the transmission lines.
To achieve its broad frequency coverage, the 778D’s directivity is optimizedfor mainline energy flowing in one direction, Thus, the test device or systemshould be connected where the 778D is labeled TEST PORT. To accommodatetest devices with type-N or APC-71 connectors, a choice of connectors is avail-able on the TEST PORT; see the options outlined under Specifications.The APC-7 precision sexless connector is recommended on the output, sincethe coupler can be conveniently converted to other types of connectors by useof an adapter, Adapters are available to OSM, TNC, GR900, and others, so thatthe coupler becomes a versatile device for making measurements on manydifferent types of connector configurations. The Amphenol, APC-7 is a sexlessconnector with very low SWR. This precision connector makes possible theconstruction of adapters with the lowest possible SWR.
The type-N connectors are stainless steel for long wear and are compatiblewith connectors whose dimensions conform to MIL-C-39012, or MIL-C-71.
3
Specifications
Frequency range 100 MHz to 2000 MHz (usable below 100 MHz)
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Directivity
Coupling factor
Tracking
Phase tracking SWR
Insertion loss Maximum power Connectors
Dimensions
Weight
Auxiliary arm 0.1 to 1 GHz 1 to 2 GHz
A 36 dB 32 dBB 30 dB 30 dB
20 dB nominal ±1 dB cyclic variation with frequency (coupling ~23 dB at 100 MHz. 6 dB rolloff per octave below 100 MHz).Auxiliary outputs typically track within 0.7 dB.typically 4°.
Primary line: 1.1; auxiliary arms: 1.1.0.6 dB
50 W average; 500 W peak (peak power duration of 10us).Choice of mainline connectors (see options); auxiliary arms have type-N female connectors, All type-N connectors stain- less steel, compatible with MIL-C-39012 and MIL-C-71.16.75 inches long, 4.375 inches high, 1.189 inches wide (425 x 111 x 30 mm).
Net, 3.75 lb (1,5 kg). Shipping, 5 lb (2,3 kg).
Americas
Canada (877) 894-4414 Latin America 305 269 7500United States (800) 829-4444Asia PacificAustralia China
Hong Kong India Japan Korea Malaysia Singapore Taiwan Thailand
1 800 629 485800 810 0189800 938 6931 800 112 9290120 (421) 345080 769 08001 800 888 8481 800 375 81000800 047 8661 800 226 008
Accessories available
Adapters
Part number
APC-7 to OSM® male 11533AAPC-7 to OSM female 11534AAPC-7 to type-N male 11525AAPC-7 to type-N female 11524A
(Adapters from APC-7 to TNC, GR-900, GR-874 as well as the above are available from Amphenol RF Division, Danbury, Conn.)
778D (type-N female output, type-N male input connectors)Option 11 (APC-7 output, type-N female input connectors)
Option 12 (type-N male output, type-N female input connectors)
Europe & Middle EastAustria 01 36027 71571Belgium 32 (0) 2 404 93 40 Denmark 45 70 13 15 15Finland 358 (0) 10 855 2100France 0825 010 700*
*0.125 €/minute
Germany 07031 464 6333 Ireland 1890 924 204Israel 972-3-9288-504/544Italy 39 02 92 60 8484Netherlands 31 (0) 20 547 2111Spain 34 (91) 631 3300Sweden 0200-88 22 55Switzerland 0800 80 53 53
United Kingdom 44 (0) 118 9276201Other European Countries:
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Revised: July 2, 2009
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Product specifications and descriptions in this document subject to change without notice.
© Agilent Technologies, Inc. 2004, 2009Printed in USA, September 11, 20095952-8133
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