Description

Features and Specifications of Keysight (Agilent/HP) 778D:

• Superior RF Performance
•  Reflection coefficient measurement: Over 4 octaves with 1 coupler
•  High directivity: 36 dB to 1 GHz, 32 dB to 2 GHz
•  Multi-octave frequency range: 100 to 2000 MHz
  • Nominal Coupling and Variation: 20 ±1.0 dB
  • Directivity: >36dB to 1 GHz
  • Maximum SWR: 1.1
  • Insertion Loss: <0.60 dB
• Power ratings
  • Power Rating Average, Peak: 50 W, 500 W
  • Power Rating Average, Peak: 50 W, 500 W

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 connected to the coupler. Figure 1 shows typical coupling and directivity characteristics of the 778D.

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 coupler make it particularly useful for this type of broadband measurement. The high directivity insures accurate measurements by a true separation of the forward and reflected signals. Close tracking of signal variation from the auxiliary arms gives a flat frequency response that makes display readings easy to interpret.