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RF Circuit Design, 2nd Edition by Richard Chi-Hsi Li

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Chapter 12: Main Parameters and System Analysis in RF Circuit Design

12.1 Introduction

With the exceptions of the oscillator or the VCO (voltage-controlled oscillator), the main task of RF circuit design is to ensure good power transport or power manipulation in most electronic products or systems, such as wireless communication systems, navigation systems, and electronic control systems. Consequently, the main parameters to be seriously concerned with in RF circuit design are as follows:

1. Power gain

In RF circuit design, it is very often necessary to intensify a weak signal to an appropriate power level when the signal is passed over an RF block. In other words, the designed RF block must have enough power gain. For instance, in the receiver of a communication system, the signal sensed by the antenna is a very weak carrier modulated with the desired digital data or other signals. The demodulator will be able to detect the desired signal from the carrier only if the power of the weak carrier is intensified to reach or exceed a “conceivable” level. The “conceivable” level depends on the incoming noise power, the type of demodulator, and so on. In a transmitter, the power of the modulated signal must be intensified to become a strong signal so that it can be transmitted by the antenna and then propagated to the receiver, which is located a long distance from the transmitter.

It should be noted that power gain is not equal to voltage gain. It is well known that power is equal to ...

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