Phase error detector for a quadrature amplitude modulated (QAM) receiver
View Patent ↗The invention relates to a phase error detector which generates a phase correction signal in such a manner that the phase characteristic curve thereof does not have any undesired zero positions and comprises a finite steepness in the angular area around the engaging point. The inventive phase error detector (PFD) calculates the phase correction signal (S) according to the detected decision domain in accordance with a number of predetermined calculating methods. The phase error detector (PFD) attains such an allocation between the decision domains of the complex QAM single state plane and the individual calculating methods such that the static phase characteristic curve thereof does not have any additional zero positions apart from the engaging point.
1. A phase error detector for generating a phase correction signal to correct a phase difference between a reference frequency of a voltage-controlled oscillator and a carrier frequency of a received signal which is received by a quadrature-amplitude modulated (QAM) receiver, the phase correction signal having a zero-crossing locking point, the received signal having in-phase components and quadrature components in a plurality of decision regions, the phase error detector comprising a signal receiver, a signal generator, and a processor for processing a plurality of different algorithms; and the phase error detector being operative for successively executing the algorithms in an order, for each of the plurality of decision regions, until the phase correction signal having no additional zero-crossing locking points is generated, wherein the plurality of different algorithms being stored in the phase error detector, and being arranged in the order as below:
S 1 =FQ f ( ZI )− FI f ( ZO )
S 2=±2 FO f ( ZI )
S 3=±2 FI f ( ZO )
S 4=±2 ZI ZO
S 5=0
in which S 1 , S 2 , S 3 , S 4 , S 5 are different phase correction signals, in which ZI and ZO are the in-phase and quadrature components of the received signal, in which FI and FO are offsets of ZI and ZQ, in which f(ZI)=ZI or sign (ZI), and f(ZO)=ZO or sign (ZO).
2. The phase error detector of claim 1 , wherein the phase error detector is operative for executing different ones of the plurality of algorithms for all of the plurality of decision regions.