A Technique to Control the Harmonic Levels in Time-Modulated Antenna Arrays—Theoretical Concept and Hardware Verification Platform

This article presents techniques into prediction and control of the radiated harmonic levels in time-modulated antenna arrays (TMAs). The effect of ramping on the controlling switching waveform, due to slew in the RF switches, is analyzed first. This is followed by a novel technique for controlling and reducing the fundamental carrier component (due to the Fourier series 0 Hz term) that is always produced by TMAs. A new bespoke, steerable, TMA RF hardware test platform is presented, using three gain states to pragmatically implement the proposed carrier reduction technique. The platform implementation utilizes binary logic control interfaces to the TMA, rather than analog control interfaces. Laboratory measurements using the test platform demonstrate a 16.5 dB reduction (limited by PCB emissions) in the level of the fundamental carrier component relative to the steered first harmonic, from a possible reduction of 21.3 dB. The array gain for the first harmonic beam is 2 dBi.