L波段双模式宽带数字Chirp设计

Design of L-band Dual-mode Wide-band Digital Chirp

介绍了能同时实现直接频率合成(DDFS)及直接波形存储(DDWS)两种方式的宽带数字Chirp信号产生器的研制工作.数字Chirp采用了数模转换率达到1 Gsps的16位DAC,在8倍过采样率下,可输出基带最高频率达110 MHz.通过正交调制,带宽可达220 MHz.正交调制器的载频泄露小于-49 dBc,镜像频率抑制-41 dBc,在500～1 500 MHz频带内的最大杂散为-25 dBc.文中对比了直接频率合成与波形存储两种体制的性能及资源使用情况,并给出两种模式的测试和实验结果.

This paper introduces the design of wide - band digital chirp signal generator, which can realize both functions of the direct frequency synthesis （DDFS） and the direct digital wave synthesis （DDWS）. It us- es a two-channel high-speed DAC with speed up to 1 Gsps, which allows to generate I and Q baseband signal with the maximum bandwidth up to 110 MHz at the 8 times over-sampling rate. So the maximum signal bandwidth after I/Q modulation can be as large as 220 MHz, while the LO feedthrough spur is suppressed to less than -49 dBc, the unwanted image frequency is less than -41 dBc in amplitude, and the maximum spur in 500-- 1 500 MHz is - 25 dBc. , We also compare the performance and resource occupation of DDFS and DDWS, and present the experimental results.