The Design Of The X L-band Frequency Synthesizer

As the key technique that apply in electronic equipments, a high performance frequency synthesizer is absolutely necessary that ensure electronic equipments such as communication systems,weapon guidance,radar to achieve high performance. It can provide the Lo and carrier signal for the equipment.By the development of electronic communication technology, higher requirements have been presented on various targets of frequency synthesizer such as phase noise, frequency-hopping and Stepped-Frequency. Low phase noise and high spurious rejection suppression are the points of the wideband frequency synthesizer, and it is important to research and development the technology of low noise and spurious suppression of the wideband frequency synthesizer.The article studies the operating principle, design, fabrication, adjustment and test as well as the experiment of the X frequency synthesizer has been introduced in detail in this report. The basic design principle of the frequency synthesizer is as follows: A reference source signal of 12 MHz is generated by a temperature compensated crystal oscillator(TCXO); then the signal is transmitted into the phase locked loop processor circuit. By using the FPGA in the MCU setting up an appropriate frequency dividing ratio, the signal is output by the phase detecting after it is low-pass filtered through the loop, and then drives the desired frequency of VCO output. The VCO output coupling of one path is transmitted back to the phase locked loop processor as the phase-detection input after it is amplified and separated; the output of the other path is power divided and amplified then the desired three-path signal can be obtained. The external control code is decoded and transmitted into the FPGA in the MCU for the frequency hopping control.The specifications of the frequency synthesizer are:The local frequency: 962MHz~1213MHzFrequency step: 1MHzFrequency accuracy: 5×-610(normal frequency)Output power: Main path: 31.5dBm±1.5dBm, the first sub-path: 10dBm±1.2dB, the second sub-path: 10dBm±1.2dB SFDR of RF signal: ≤-60 dBc Output phase noise: ≤-80dBc@1kHz, ≤-85dBc@10kHz...