数字相位调制：8.9 PSK调制电路原理及应用

8.9 PSK modulation circuit is a type of digital phase modulation where the phase of the carrier signal is controlled by a digital baseband signal, causing the phase of the carrier signal to change. Binary phase shift keying (PSK) uses two different phases of the same carrier to represent digital signals. PSK systems have better noise resistance and higher bandwidth utilization compared to amplitude shift keying (ASK) and frequency shift keying (FSK), making them widely used in medium to high-speed digital communications. Absolute phase modulation and relative phase modulation are two common types of digital phase modulation used in PSK systems. Absolute phase modulation (also known as CPSK) and relative phase modulation (DPSK) are often referred to as 2CPSK and 2DPSK for binary signals. In absolute phase modulation (CPSK), different phases of the carrier signal are used to directly transmit digital information. For binary CPSK, "0" is represented by a phase of π and "1" is represented by a phase of 0. The mathematical expression of a 2CPSK signal is shown in equation (8.9.1), where θ0 represents the initial phase of the carrier signal. The controlled carrier signal changes between 0 and π phases as shown in Figure 8.9.1, with (a) representing the digital baseband signal S(t) (also known as absolute code) and (b) representing the carrier signal. Overall, PSK modulation circuits are essential in digital communications for efficiently transmitting data over medium to high-speed channels with improved noise resistance and bandwidth utilization.