| The stepped frequency radar transmits N narrowband pulses which are stepped in frequency by a fixed step size, to obtain the frequency response of the targets. Then, the time domain response, ie. the range profile is synthesized by inverse Fourier transform. The advantage of the stepped frequency approach is that it can provide a wide effective bandwidth while still maintain a narrow instantaneous bandwidth, which reduces the A/D sampling rate.Ultra-wideband stepped frequency radar front end includes ultra-wideband stepped frequency signal synthesizer, ultra-wideband transmitter and ultra-wideband receiver. This thesis describes the step-frequency ultra-wideband radar front-end design of each part in detail. The stepped frequency radar front-end is completed with the frequency range of3-5.044GHz, equivalent bandwidth of2.044GHz, frequency points to512, frequency hopping time less than20us, transmit power greater than20dBm, receiver noise figure of2.8dB～3.7dB.This thesis proposed a method based on entropy minimization to compensate the I/Q channel errors of the quadrature demodulator of stepped frequency radar receiver. Profile entropy is used as the cost function to search the I/Q channel errors. The method is based on radar echoes and avoids the extra complex test operation in traditional methods. And it is a real time method so that it can feel the changes in device characteristics. Finally, in the target sparse imaging scene, compressive sensing theory is used in stepped frequency radar, to synthesize the profile with less frequency domain data. And and the impact of the echo signal to noise ratio and the number of frequency step on the reconstruction error is explored. |
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