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Design Notes

Chirp Radar System

The chirp signal is generated by CHIRP_LFM, whose parameters allow user to define the pulse frequency span, PRF, duty cycle, etc.

The IF spectrum is shown in the graph "IF Output." The instantaneous frequency of the transmitted signal (black), and instantaneous IF is shown in the graph "Instantaneous Frequency." You can tune on the delay of the received signal and simultaneously monitor the change in the IF frequency.

The spectrum of the chirp signal is shown in the graph "TX Spectrum."  This graph has its RBW set to 0.25 MHz and its VBW set to 0.25 KHz. A Blackman-Harris window is applied to the time domain signal prior to generating the spectrum.

The output of the chirp generator is used to feed a coupler sub-circuit that is used to couple a portion of the transmitted signal to the receiver's down converter.  Another coupler is used to simulate the leakage of the transmitted signal to the receive RF link.

The received signal path is simulated through the use of an attenuator, delay element, and an AWGN channel used to add ambient noise seen by a receiver's antenna.

Further processing of the inphase and quadrature signals can be added after the complex to real/imaginary converter.

System Diagram - Chirp System

Graph - Instantaneous Frequency

Graph - IF Output

Graph - Chirp Signal

Graph - TX Spectrum