Prototype circuit demonstrates IF-VGA gain characteristic - IF VGA design - Part 6

SYSTEM designs based on complex signal-processing functions-such as radar, direction finding (DF), electronic countermeasures (ECM), and threshold detection-often require intermediate-frequency (IF) amplifiers with automatic-gain-control (AGC) capability. An innovative IF variable-gain-amplifier (VGA) design delivers a prescribed gain characteristic that incorporates a discontinuity as well as a slope change. The VGA provides a 60-dB gain-control range, with a 3-dB bandwidth of 20 to 50 MHz that is centered at 150 MHz. The concluding article of a six-part series describes the amplifier's series-to-parallel transformation network, which is Used to implement the desired VGA gain response. In addition, the measured performance of a production prototype IF VGA is presented.