Cdma base station modulator for digital cellular mobile communication

Abstract

A base station modulator for the digital cellular mobile communication system achieves reduced hardware complexity in a base band QPSK modulating circuit by applying the Multilevel Logic Operation (MLO) which is extended from the conventional binary exclusive-OR operation, to the conventional Base Station Modulator (BSM). The base station modulator includes a plurality of spreaders 621 for QPSK spreading of a voice data stream. These spreaders 621 employ binary-multilevel Logic (MLO) gates instead of multiple binary exclusive-OR gates. The binary-multilevel Logic gate includes a subtractor 510 and a selector 520. The subtractor has one input (-) to which multilevel logic values are applied and one input (+) to which a maximum logic level of the multilevel logic values is applied. The selector has one input to which the multilevel logic values are applied, one input to which the output signal of the subtractor 510 is applied, and one control input to which the binary logic value is applied. If the binary logic value is zero (0), the selector 520 selects and outputs the multilevel logic values, and if the binary logic value is one (1), the selector 520 selects and outputs the output signal from the subtractor 510.