Channelized multi-frequency measurement system based on asymmetric double sideband detection

A channelized multi-frequency measurement system based on asymmetric double sideband detection is proposed. In this scheme, the sub-modulators of the dual-parallel Mach-Zehnder modulator are utilized for optical frequency comb (OFC) generation and under-test signal modulation. Subsequently, a sawtooth wave voltage is applied to the main modulator to introduce frequency shift to the modulated signals, breaking the symmetry between the RF signals and the OFC. The coupled signal is then divided into upper and lower sidebands for frequency down-conversion. By calibrating the measurement results of the two sidebands with each other, the frequency of the signal can be accurately measured. Simulation is preformed to realize multi-frequency measurement of microwave signals with measurement error less than 2 MHz in the range of 2.2-20 GHz. It is also found that the proposal can solve the problem of frequency ambiguity.