平方环 meaning in English

quadratic loop

There are many ways of modulating signal about bpsk such as castas loop , square loop , etc . usually the carrier wave is put forward firstly , then the purified carrier wave is used to demodulate the output data ( all these things are usually completed in the same loop ) . these methods have their strong points but at same times , it is difficult to design and achieve these ways
有关bpsk调制信号的解调方法很多，例如castas环，平方环等，这些方法一般都是先提取载波，然后用提纯的载波去解调出传输的数据(大都在同一个环路内完成) ，这些方法的优点是显而易见的，但是在某些条件下，这些方法的设计和实现却很困难。