在单片机中锁相环功能（The function of phase-locked loop in single-chip microcomputer）.doc

在单片机中锁相环功能（The function of phase-locked loop in single-chip microcomputer） A phase-locked loop refers to a circuit or module which is used in a receiver of communication and its function is to receive The signal is processed and the phase information of a clock is extracted from it. Or, for acceptance The signal, which is a copy of a clock signal, makes the two signals synchronised from some point of view ( Or, coherent. The dummy clock signal is relative to the received signal due to the lock case (that is, after the capture) The clock signal has a certain difference, so it is very figuratively called a phase-locking device. In general, the three components of the phase-locked loop and the corresponding operation mechanism are: Phase 1 phase detector: the amplitude of the clock signal output of the phase-locked device and the clock in the receiving signal; 2 adjustable/FM clock generator: used to adjust the phase-locking device according to the signal output from the phase detector The frequency or phase of the internal clock output signal makes the phase-locked device complete the above fixed phase difference function; 3 loop filter: used to filter and smooth the output signal of the phase detector. In most cases, it is a low pass Filters are used to filter out the effects of data changes and other destabilizing factors on the entire module. As can be seen from the above, there are roughly the following block diagrams: ┌ -- -- - ┐ ┌ -- -- - ┐ ┌ -- -- -- - ┐ - - ┤ phase discriminator ├ - - - ┤ loop filter ├ - - - ┤ controlled clock generator ├ - ┬ - - └ -- ┬ -- ┘ └ -- -- - ┘ └ -- -- -- -- ┘ │ Write left └ -- -- -- -- -- -- -- -- -- -- -- -- -- ┘ Visible, is a negative feedback Loop structure, so it is commonly referred to as the phase-locked Loop (PLL: Phase Locking Loop) There are many types of phase-locking rings, which can be numeric or simulated or mixed, and can be used to recover the carrier It can also be used to restore the baseband signal clock Phase-locke