WIDE-BAND I Q DEMODULATORS - MEASUREMENT TECHNIQUE AND MATCHING CHARACTERISTICS/

Wideband I/Q demodulators which can be used to measure the amplitude, phase and instantaneous frequency of radar signals are investigated. A simple Fourier transform technique is developed to characterise the i mbalances and DC offsets of I/Q demodulators by injecting a test signa l. Imbalances and DC offsets are minimised using component matching an d calibration techniques. Average RMS fractional amplitude and phase i mbalance errors of 0.011 and 0.302 degrees, respectively, can be achie ved on custom matched units at a centre frequency of 1GHz over an inst antaneous bandwidth of 100MHz and a dynamic range of 24dB. Finally, th e matching characteristics over time and temperature on some of these wideband I/Q demodulators are also evaluated.