PI/4 SHIFT QPSK MODULATOR AND COMMUNICATION EQUIPMENT USING IT

摘要

PURPOSE: To reduce the storage capacity of ROM to a half by distributing an arithmetic result into the signals of two systems, which are mutually orthogonal, and code-inverting the signals of the two systems or substituting them for previously set points only when they are designated in accordance with phase information. ;CONSTITUTION: Response data are previously stored and set in RQM 21 so that impulse response data is to be read when an output signal 111 is inputted as '1', and response data corresponding to input cos 45° when it is inputted as '0'. When an output signal 112 is inputted to a code inversion circuit 22 as '1', response data from ROM 21 is controlled to become negative. When an output signal Q12 is inputted to a code inversion circuit 24 as '1', response data from ROM 21 is inverse-controlled so that it is to become negative. When an output signal 113 is inputted to an output circuit 23 as '1', a value from a previous order is substituted for '0'. When an output signal Q13 is inputted to an output circuit 25 as '1', the value from the previous order is controlled so that it becomes '0' in the same way.;COPYRIGHT: (C)1995,JPO