Method for distinguishing a signal and its image

A method for identifying a signal and its image signal in a heterodyne frequency sweep system, the method comprising:

• circuits and an identifying model;
• the circuits further comprising an input module, a mixing module with heterodyne frequency sweep and a detection and identification module;
• the input module further comprising input impedance matching and signal adjustment sub-circuits, wherein a low-pass filter that may filters the image signal to be detected is not included;
• the mixing module with heterodyne frequency sweep further comprising a mixer, a frequency sweep local oscillator (SLO), an intermediate frequency (IF) filter, a positive and a negative sign filter (PNS filters) sub-circuits,
• wherein the center frequency of positive sign filter is higher than that of the IF filter and the center frequency of negative sign filter is lower than that of the IF filter, and
• the pass band of IF filter, positive sign filter and negative sign filter does not intersect each other;
• the detection and identification module further comprising an IF detector, a positive sign detector, a negative sign detector, analog-digital convertors, and a digital circuit;
• a configuration wherein the output signal from the input module is mixed with the frequency sweep local signal in the mixing module;
• a configuration wherein the output signals of the mixing module are input to the IF filter, the positive sign filter and the negative sign filter, respectively;
• a configuration wherein the output signals from the IF filter, the positive sign filter and negative sign filter are input to the detection and identification module, the signal and its image are identified by an identifying model using the timing order sequence of the output signals from the IF, PNS filters in the detection and identification module.