Research And Design On Wideband Stepped Frequency Synthesizer In Radar Target Simulator

Radar target simulator has been widely investigated and applied for its advantages of avoiding the high cost, long period and inconvenient control of echo parameters of field experiments. With the complicated system structure and perfect functions of modern radar, the requirements for frequency synthesizer are becoming higher. In combination with specific project purpose, a stepped frequency synthesizer with wide band, small frequency hopping step has been verified and implemented in this dissertation.The main task contains:First of all, the popular frequency synthesis methods including direct synthesis, phase locked loop, direct digital synthesis and hybrid synthesis are presented, and their basic principles and pros and cons are also been discussed. In combination with the project purpose of fast frequency hopping, the DDS and PLL mixing outside the loop is chosen to be the final scheme.The DDS circuit has been designed using AD9912. The output frequency range is150~400MHz, which steps by 250 Hz in minimum. The typical output power is 3dBm, and the phase noise value is typically-116dBc/Hz@10KHz.Multiple PLLs have been designed using ADF4350 and ADF4107. The output frequency values are 1.4GHz, 3GHz, 4GHz, 5GHz, and 6GHz. The output power is typically 10 dBm, and the typical spur level is lower than-60 dBc.The up-converter circuitry has been designed with multiple amplifiers, frequency multipliers, mixers and filters. In combination with the DDS and PLLs above, a wideband frequency synthesizer has been implemented, with its output frequency range of 5~9GHz and the minimum frequency step 1 KHz. The output power is 0 dBm, the typical phase noise value is-90dBc/Hz@10KHz, and the spur level is typically lower than-50 dBc.