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噪声系数是描述混频器性能的主要指标,而混频器噪声系数主要由混频二极管、混频电路及主要频率终端来决定。目前,一般采用镜频回收电路来降低噪声系数。12GHz 镜频回收混频器是低噪声混频器,它由正交场混频器和立体平面滤波器所构成。与一般正交场混频器相比,噪声系数改善1dB 以上。由于正交场混频器已经成熟,而镜频回收效果主要取决于滤波器性能的优劣,因此,设计制作滤波器是本研制工作的重点。根据本文提供的工程设计曲线设计的滤波器,理论、实际一致性好。该滤波器带内插损小(0.5dB 以内),带外抑制度高,兼备了波导滤波器和微带滤波器的优点。且结构简单,成本低。本文叙述镜频回收原理、方案、电路及其工作状态,着重介绍立体平面滤波器的原理与设计。
The noise figure is the main index to describe the performance of the mixer. The noise figure of the mixer is mainly determined by the mixing diode, mixer circuit and the main frequency terminal. Currently, the general recovery of the circuit using the mirror to reduce the noise figure. The 12GHz video recovery mixer is a low noise mixer that consists of an orthogonal field mixer and a stereo planar filter. Compared with the normal orthogonal field mixer, the noise figure improved more than 1dB. As the orthogonal field mixer has matured, and the recovery effect depends mainly on the performance of the filter, the design and manufacture of filters is the focus of this work. According to the engineering design curve provided in this paper, the filter theory, the actual consistency is good. The filter with small insertion loss (less than 0.5dB), out of band suppression, both the waveguide filter and microstrip filter advantages. The structure is simple and the cost is low. This article describes the principle of mirror recovery, programs, circuits and their working conditions, focusing on the principle and design of three-dimensional planar filter.