TABLE OF CONTENTS In this chapter, a phase measurement method and a zero crossing method will be discussed. These methods are relatively simple, but they can operate only under limited conditions. If the input contains only one sinusoidal wave, these methods can provide very accurate frequency measurement. Theoretically, these methods can detect the existence of simultaneous signals. The phase measurement approach uses analog in-phase and quadrature ( I- Q) channels as the front end. If the I- Q channels are perfectly balanced, the phase measurement method can measure the frequencies of two input signals. The zero crossing method can measure the frequencies of multiple input signals. However, when multiple signals are present, the frequency accuracy measured by both these two methods will suffer compared with one input signal. Some of these methods need more investigation to determine their performances.
If the input signal is frequency modulated (FM), these methods can find the instantaneous frequency of the signal. In other words, the frequency versus time can be obtained. Such information is difficult to obtain from the Fourier transform. If the signal modulation is phase shift keying (PSK), the phase-sensitive methods can detect phase reversal in the signal. Therefore, it can detect the chip rate (or the clock frequency) of the PSK These capabilities are also limited to a single signal. If there are simultaneous signals, these methods may generate erroneous information.
The instantaneous frequency measurement (IFM) receiver, an analog receiver discussed in Chapter 2, measures the phase between...
