Digital Receiver Used In Microwave Modulated Laser Doppler Radar

With the rapid development of VHIC and VLSIC, digital receiver has been widely used in areas such as Radar, EW, and wireless communication. The analog intermediate frequency (IF) echo signals or analog radio frequency(RF) echo signals in radar are sampled and then converted to digital signals by ADC located in digital receiver. Quadrature demodulation and wave filtering are realized by Very High-Speed Digital Signal Processing (DSP) and Very Large-Scale FPGA in digital processing. More and more analog circuits are replaced by digital circuits, bad effects caused by analog circuits such as temperature excursion, gain alteration and DC voltage offset have been greatly reduced and the performances of radar system have been improved significantly. Moreover, a solution of universal processing platform with special software is used in digital receiver. This makes the system more flexible, open and general.The basic theorem and structure of the digital receiver, especially the intermediate frequency sampling digital receiver are discussed in the paper. The key theories are also narrated such as sample theorem, High-Speed A/D convertor and quadrature demodulator. Detailed analysis and design on IF digital receiver are illustrated with an emphasis on analog front and Digital IF. In the end, an application example about digital receiver used in microwave modulated laser Doppler radar is given order to illustrate the key points and basic design theories.