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设计了一种由直接数字频率合成(DDS)、倍频链构成的三次变频直接频率合成方案,实现了低相噪捷变频高分辨率毫米波雷达频率合成器设计。利用直接频率合成器的倍频输出取代传统三次变频毫米波频率源的锁相环(PLL),同时提供线性调频(LFM)信号,优化DDS和变频方案的频率配置关系。利用FPGA电路进行高速控制,较好地解决了毫米波频率合成器各技术指标之间的矛盾。实测结果表明,采用该方案的毫米波频率合成器在本振跳频带宽为160 MHz时,线性调频频率分辨率可达0.931 Hz,最大频率转换时间小于2μs,最大杂散低于-60 dBc,相位噪声优于-90 dBc/Hz。
A three-frequency direct conversion frequency synthesizer composed of direct digital frequency synthesizer (DDS) and frequency multiplier chains was designed and a low-phase-noise agile frequency conversion high-resolution millimeter-wave radar frequency synthesizer was designed. The frequency conversion of the DDS and frequency conversion scheme is optimized by replacing the PLL of the traditional three-frequency millimeter-wave frequency source with the frequency-doubling output of the direct frequency synthesizer and providing a linear frequency modulation (LFM) signal. The use of FPGA circuit for high-speed control, a better solution to the millimeter-wave frequency synthesizer between the technical indicators of the conflict. The measured results show that the millimeter-wave frequency synthesizer with the proposed scheme achieves a frequency resolution of 0.931 Hz, a maximum frequency conversion time of less than 2 μs and a maximum spurious below -60 dBc at a local oscillator frequency of 160 MHz. The phase noise is better than -90 dBc / Hz.