摘要
论证了宽带无线接收机宜采用上边注入、固定中频的二次正交混频低中频结构.文中推导出单双正交与双双正交这两种二次正交混频结构中分别存在4种镜像抑制比及这4种镜像抑制比与其结构中的幅度失配ΔA或相位失配Δθ之间的定量关系.两种结构的性能比较表明,宽带无线接收机射频前端更适合采用单双正交结构.为提高系统的镜像抑制性能,射频前端在单双正交结构的基础上添加两个模块:射频滤波器与第2次混频之前的多相滤波器.最后,给出了整个射频前端系统的镜像抑制性能关系式,并给出一个设计实例(DRM接收机射频前端).MATLAB仿真结果表明,本射频前端结构具有良好的镜像抑制性能(当-10°≤Δθ≤10,°-0.1≤ΔA≤0.1时,4个镜像抑制比IRR≥61.16 dB),结合低中频结构固有的便于高集成度,支持多通信标准,且可避免寄生低频噪声影响等特点,使之成为实现宽带无线接收机的理想结构之一.
A high-side injection, fixed intermediate frequency （IF）, double-quadrature-downconversion and low-IF structure is proposed for wideband receivers. Four image rejection ratios （IRR）, and relationship between IRRs and the amplitude errors △A or phase errors △θ of two kinds of double quadrature receiver structures （ single-double and double-double quadrature quadrature conversion is more structures） are derived. Comparison of these two structures shows that single-double suitable for wideband receivers. To improve IRRs of the system, two modules, RF filter and polyphase filter before the second downconversion, are added to the single-double quadrature structure. The quantitative IRRs performance of the total RF-end and a design example, DRM receiver RF-end, are given. Simulation results show that this RF-end structure has good IRR performance （ when -10°≤△θ≤10°,-0.1≤△A≤0.1, IRRs≥61.16 dB）. This is an ideal structure for widehand radio receivers, combining the inherent characteristics of a low-IF structure such as suitability for high integrality, ability of supporting multi-standard communication, and immunity to parasitical low frequency noise.
出处
《应用科学学报》
CAS
CSCD
北大核心
2008年第2期155-161,共7页
Journal of Applied Sciences
关键词
宽带接收机
射频前端
二次变频
正交混频
镜像抑制比
wideband receiver, RF front-end, dual-conversion, quadrature downconvert, image rejection ratio（IRR）
