In-Situ Current Measurements of Wideband Signals for Radar Arrays

Ensuring accurate array calibration is essential to maintaining optimized system performance of phased-array transmitters. Wideband signals increase the complexity of the issue by requiring an accurate calibration over a larger bandwidth. Reconfigurable hardware such as tunable impedance matching circuits can help optimize performance over a broad frequency range, but also dynamically interfere with both the phase and amplitude of transmitted signals, thus undermining any preset array calibration and altering the array transmission pattern. To combat this issue, a method for monitoring antenna current in real-time is required to enable accurate calibrations to be continuously enforced as conditions change. This paper provides measurement validation of an in-situ current measurement method for wideband signals using a software-defined radio (SDR) to measure voltages from a dual-directional coupler. This experiment found that antenna reflection coefficients measured from the in-situ technique correspond very well with direct measurements performed for validation. This novel technique advances the cutting edge, enabling real-time self-contained transmitter calibration for wideband systems with reconfigurable components.