引言用来改善外差式接收机前端噪声系数的低噪声砷化镓■效应放大器,当使其正反馈时就产生振荡。■效应放大器不仅放大输入信号,而且也产生本振信号,所以可以省去本地振荡器。因此,可以设计出一个成本低和功耗小的、适用于微波集成电路外差式接收机用的前端。因为振荡器和放大器共用一只■效应放大器,故有相互调制存在,对噪声系数和传输特性会有影响。这个外差式接收机前端,由于使用了在正反馈环路中的混频器的饱和特性(这个环路对于本地信号的振荡是必要的),在■效应放大器的线性段能达到稳定振荡。因为 Introduction Low noise gallium arsenide effect amplifiers used to improve the front-end noise figure of heterodyne receivers oscillate when they are fed back. ■ The effect amplifier not only amplifies the input signal, but also generates the local oscillator signal, so the local oscillator can be omitted. Therefore, a low-cost and low-power front-end for a microwave integrated circuit heterodyne receiver can be designed. Because the oscillator and amplifier share a ■ effect amplifier, there is a mutual modulation, the noise figure and transmission characteristics will have an impact. This heterodyne receiver front end stabilizes oscillations in the linear section of the ■ effect amplifier due to the saturation characteristics of the mixer in the positive feedback loop, which is necessary for local signal oscillations. because