应用于移动通信的DDS频率合成器

The DDS Frequency Synthesizer for Mobile Communication

随着数字技术的发展 ,近十几年来 ,直接数字频率合成 ( DDS)技术发展很快 ,已发展成为主要的频率合成技术之一。现代许多频率合成器在设计中采用了 DDS和 PLL的混合式频率合成技术 ,可以将 DDS的高分辨率及快速转换时间特性与 PLL的输出功率高、寄生噪声和杂散低的特点有机地结合起来。文中研究了应用于正交频分复用 ( OFDM)通信系统的 DDS+ PPL混合式频率合成器设计 ,给出了系统方案、电路实现及测试结果 ,输出信号功率为 -5 d Bm,带内相位噪声可以达到 -76d Bc/Hz@1 k Hz,频率分辨率为 1 Hz,跳频速度可以达到 1 0 4 跳 /秒的数量级 ,实验表明其性能指标满足 OFDM通信系统的要求。

With the digital technology in recent years, Direct Digital Synthesis (DDS) technology had got development rapidly and been one of dominant frequency synthesis techniques. The hybrid frequency synthesis technique of DDS and PLL is employed in modern frequency synthesizer design widely, which combines higher resolution, fast switching time of DDS and higher output power, lower parasitic noise and spurious of PLL. This paper researches a hybrid frequency synthesizer for OFDM communication system based on DDS and PLL technology. The system scheme, circuit design and test results are presented. The output power was -5 dBm, phase noise in band reached -76 dBc/Hz@1kHz,frequency resolution was 1Hz and hopping speed was 10~4time/second. The experiment results show the performance meets the requirement of OFDM system.