A Simple Radiophotonic Device for Instantaneous Frequency Measurement of Multiple Microwave Signals Based on a Symmetrical Unequal Comb Generator

The paper presents the results and analysis of a radiophotonic device for instantaneous frequency measurements of microwave signals, including the situation with simultaneous measurements of multitude instantaneous frequencies. The device’s principle of operation is to combine the “frequency–amplitude” measurement conversion for the determined frequency with carrier suppression and the formation of equidistant channels based on the frequency comb to estimate its magnitude. An efficient method for unequal symmetric optical frequency comb generation based on the phase switching of an optical carrier with its suppression in a phase modulator is proposed. The comb allows for the formation of up to ten channels with a width of 2 GHz that can be adjusted. The amplitudes of the boundary frequencies of the channels are not equal, which makes it possible to differentiate the measured frequencies in relation to the powers of their beats. Separately, the features of the instantaneous frequency measurement in the zero channel of the device are studied. The use of information signals with a suppressed carrier makes it possible to reduce the requirements for the laser frequency stability. The bandwidth of the photodetector is equal to the channel width, thus making it possible to use it as a channel filter. The device is first simulated in the Optiwave System software environment, and the factors affecting the system performance are then studied on a test bench. The design simplicity of the device, built on only two modulators, is noted.