TABLE OF CONTENTS The correlation receiver was shown to be the optimum receiver for baseband signals in Chapter 2. The development of the optimal receiver for coherent bandpass signals now follows a similar path and also results in the correlation receiver. The optimum threshold ? opt and probability of bit error P b for symmetrical and asymmetrical bandpass signals is found to be the same as that for baseband signals. Although these analytical results are somewhat reassuring, the SystemVue simulation of the modulation and demodulation of the bandpass signals with the resulting BER measurement provides an insight into the process and a verification of the expected performance.
Demodulation of bandpass digital communication systems can be accomplished either coherently, where the receiver internally produces a reference signal of the same frequency and phase as the input signal, or noncoherently, where the receiver does not use a reference signal, but employs either differential encoding of the information or even simpler means. The optimum coherent receiver for bandpass signals can be shown to be the matched filter, with an impulse response that is given for baseband signals by Equation 2.20 in Chapter 2 [Stern04].
The optimum receiver for bandpass signals can be implemented as a correlation receiver for either symmetrical or asymmetrical signals. The bit time is T b and symmetrical signals are defined by Equation 3.1.
| (3.1) |  |
On the CD The bandpass signal s 1( t) represents...
