| 摘要 |
PURPOSE:To reduce the power consumption of a mobile radio equipment and to make it compact and light in weight by preventing the amplitude of a modulated signal from passing the point of '0', in a modulating system for the spread spectrum transmitter receiver. CONSTITUTION:The outputs of gates 62 and 63 are inputted to a signal point arranging circuit 68, and the modulated signal is arranged while making logic levels 0 and 1 correspondent to amplitude levels +1 and -1. The modulated signal passes through low-pass filters 69 and 610, afterwards, an orthogonal carrier provided from a carrier signal generator 614 by frequency mixers 611 and 613 and an in-phase carrier provided by passing this orthogonal carrier through a 90 deg. phase shifter 612 are multiplied, added and synthesized by an adder 615, and a quatery phase shift keyed (QPSK) spread spectrum transmission waves are provided. In this case, since the provided QPSK wave is equipped with prescribed inhibited phase transition, it does not pass the point of amplitude '0' and the amplitude fluctuation of the modulated wave is small. Therefore, the signal level of a power amplifier in the final step of the modulator can be enlarged, and power efficiency can be improved. |
