A Heterodyned Programmable Gain Detector for Precision Power Control in Stimulus-Response Measurement Systems

A unique power leveling loop based on a heterodyned programmable gain detector for use in broad band, millimeter wave network analyzers and other stimulus-response measurement systems is described. The system allows precise power control over a wide range of power levels and a broad range of frequencies. Power adjustment is linear and is independent of frequency. In addition, excellent power accuracy is achieved via a simple calibration technique. The specific implementation described in this article has at least 20 dB of linear power tuning range with better than 0.1 dB resolution in the frequency range from 45 MHz to 110 GHz.