V4561983-0100 ALSOTOM 电路板控制卡模块

V4561983-0100 ALSOTOM 电路板控制卡模块

有时这被称为四相PSK，4-PSK，或4-（同QuadratureAmplitudeModulation）正交幅度调制。(虽然QPSK和4-QAM的根本概念不同，但产生的调制无线电波完全相同。)QPSK在星座图上用了四个点，围绕一个圆等距分布。通过四个相位，QPSK可以对每个符号进行两位编码，如图所示格雷编码为了最小化比特误码率(BER)——有时被误认为是BPSK的两倍。

数学分析表明，与BPSK系统相比，QPSK可用于使数据速率加倍，同时保持相同的 带宽的信号，或者保持BPSK的数据速率但是将所需带宽减半。在后一种情况下，QPSK的误码率为完全一样作为BPSK的BER当考虑或描述QPSK时，持有不同的观点是一种常见的困惑。传输的载波可以经历多次相位变化。

假设无线电通信信道是由诸如联邦通信委员会给定规定的(最大)带宽，QPSK相对于BPSK的优势变得明显:在相同的误码率下，QPSK在给定的带宽内传输的数据速率是BPSK的两倍。付出的工程代价是QPSK的****机和接收机比BPSK的更复杂。然而，随着现代电子学技术，在成本上的惩罚是非常温和的。与BPSK一样，在接收端存在相位模糊问题差分编码实践中经常使用QPSK。 

V4561983-0100 ALSOTOM 电路板控制卡模块

PSK, sometimes referred to as the four phase 4 wpa2-psk, 4 - (with QuadratureAmplitudeModulation) or quadrature amplitude modulation (am). (Although the fundamental concepts of QPSK and 4-QAM differ, the modulated radio waves produced are exactly the same.) QPSK uses four points on the constellation chart, equidistant around a circle. With four phases, QPSK can encode each symbol in two bits, as shown in the figure for Gray encoding to minimize the bit error rate (BER) - sometimes mistaken for twice that of BPSK.

Mathematical analysis shows that compared to BPSK systems, QPSK can be used to double the data rate while maintaining the signal with the same bandwidth, or to maintain the data rate of BPSK but halve the required bandwidth. In the latter case, the bit error rate of QPSK is exactly the same as BER of BPSK. It is a common confusion to hold different views when considering or describing QPSK. The transmitted carrier can undergo multiple phase changes.

Assuming that radio communication channels are set by (maximum) bandwidths such as those prescribed by the Federal Communications Commission, the advantage of QPSK over BPSK becomes apparent: for the same bit error rate, QPSK transmits twice the data rate of BPSK over a given bandwidth. The engineering cost is that the QPSK's **** machine and receiver are more complex than the BPSK's. However, with modern electronics technology, the penalty in cost is very mild. Like BPSK, QPSK is often used in differential coding practices because of phase ambiguity at the receiver end.