一种2～4 GHz宽带接收机的小型化前端设计

摘要

针对2～4 GHz的超宽频带，提出了一种宽带接收机的前端设计方法，其中包括射频信道设计、频率合成器的设计以及基带电路设计。鉴于小型化的设计思想，射频前端采用零中频接收机的架构，使用 LTCC 滤波器实现噪声系数优于8 dB，输出三阶截断点优于27 dBm（低噪声模式下）。频率合成器采用集成VCO的锁相环芯片 ADF4351，实现单边带相位噪声优于－110 dBc／Hz＠200 kHz。基带电路采用正交解调器 ADL5380和12位双通道 AD 转换器AD9238，可实现带宽为20 MHz的I／Q双路同时解调。通过FPGA或DSP 处理，可广泛用于便携式小型化的监测接收机或通信接收机。%For ultra⁃wideband of 2~4 GHz,a method of wideband receiver front⁃end design is proposed,which includes RF channel design,frequency synthesizer design and baseband circuit design.Given the small size of the design,the RF front⁃end adopts a zero⁃IF receiver architecture,uses LTCC filters to realize a noise figure of better than 8 dB,and achieves an output of third⁃order intercept point better than 27 dBm (low⁃noise mode).The frequency synthesizer adopts a VCO integrated PLL chip ADF4351,realizing a SSB phase noise better than ⁃110 dBc/Hz @ 200 kHz,and the scanning speed is better than 40 GHz/s.The baseband circuit uses an ADL5380 quadrature demodulator and a 12⁃bit dual⁃channel AD converter AD9238, which achieves 20 MHz⁃bandwidth simultaneous I/Q dual demodulation.By FPGA or DSP processing,it can be widely used in portable miniaturized monitoring receivers or communications receivers.