UC知道通信专业英语翻译 急！（3）
来源：百度知道 编辑：UC知道 时间：2024/05/17 00:43:38
通信专业英语，感谢高手帮忙！ Basic RF building blocks
2. Oscillators
Oscillators generate a reference signal at a particular frequency．In some oscillators, referred to as VCOs for voltage controlled oscillators, the frequency of the output varies proportionally to some input signal. Compared to mixers, oscillators seem quite simple. That is an illusion.
Oscillators are generally used in RF circuits to generate the LO signal for mixers. The noise performance of the mixer is strongly affected by noise on the LO signal. The LO is always passed through a limiter, which is generally built into the mixer, to make the mixer less sensitive to small variations in the amplitude of the LO. However, the mixer is still sensitive to variations in the phase of the LO. Thus, it is important to minimize the phase produced by the oscillator.
Nonlinear oscillators naturally produce high levels of phase noise. To see why, consider the trajectory of an oscillator’s stable periodic orbit
2. Oscillators
Oscillators generate a reference signal at a particular frequency．In some oscillators, referred to as VCOs for voltage controlled oscillators, the frequency of the output varies proportionally to some input signal. Compared to mixers, oscillators seem quite simple. That is an illusion.
Oscillators are generally used in RF circuits to generate the LO signal for mixers. The noise performance of the mixer is strongly affected by noise on the LO signal. The LO is always passed through a limiter, which is generally built into the mixer, to make the mixer less sensitive to small variations in the amplitude of the LO. However, the mixer is still sensitive to variations in the phase of the LO. Thus, it is important to minimize the phase produced by the oscillator.
Nonlinear oscillators naturally produce high levels of phase noise. To see why, consider the trajectory of an oscillator’s stable periodic orbit
2 . 振荡器
振荡器在特殊频率下产生标准参照信号。某些振荡器，称作电压控制振荡器，其输出频率与某些输入信号成比例地改变。语混频器比较，振荡器似呼很简单；这是个错觉。一般，振荡器在射频电路里被用来为混频器产生LO信号。按混频器的噪声特性，噪声对LO 信号有很强地影响。一般，Lo 信号总是通过装在混频器里的限制器，使混频器对LO波幅的微小变化不那么敏感；但是，混频器对LO相位的变化仍然敏感。因此，重要的是使振荡器产生的相位最小。非线性振荡器自然产生高水平的相位噪声。为了知道为什么，考虑在一个状态空间里，振荡器的稳定周期的运行轨道是个弹道曲线；此外，在考虑，以脉冲 mu(t)=delta(t)表示对振荡器的干扰；则振荡器的响应按照下式的摄振弹道曲线表示：v(t)+ DeltaV(t),如图3 ； 式中，v(t)表示摄振T周期的解，而DeltaV(t)为响应。
把摄振响应分解为波幅和相位变化，则vn(t)+delta vn(t)( 照抄公式）；式中 vn(t) 表示振荡器的噪声输出电压； a(t) - 波幅变化；phi(t)--相位变化；f0=1/T 为震荡频率。