Data transmitting machine and receiver of extensionable frequency spectrum communication system using pilot frequency channels

Abstract

An improved spread spectrum communication system includes a transmitter and a receiver utilizing a pilot channel for the transmission of pure rather than modulated PN codes for code acquisition or tracking purposes with a lower bit error rate. The pilot signal is used to obtain initial system synchronization and phase tracking of the transmitted spread spectrum signal. At the transmitter side, a Walsh code generator, a Walsh modulator, a first PN code generator, a first band spreader, a second band spreader, finite impulse response filters, digital-analog converters, low-pass filters, an intermediate frequency mixer, a carrier mixer, a band-pass filter are used to transmit a spread spectrum signal. At the receiver side, a corresponding band-pass filter, a carrier mixer, an intermediate-frequency mixer, low-pass filters, analog-digital converters, a second PN code generator, an I channel despreader, a Q channel despreader, a PN code synchronization controller, a Walsh code generator, a first Walsh demodulator, a second Walsh demodulator, accumulator & dump circuits, a combiner, and a data decider are used to demodulate a received spread spectrum signal

Description

[0001] This application is a divisional application of the patent application with the application date of November 22, 1995, the application number 95118184.x, and the title "Data Transmitter and Receiver of Spread Spectrum Communication System Using Pilot Channel". technical field [0002] The present invention relates to spread spectrum communication systems, and more particularly to data transmitters and receivers for spread spectrum communication systems using pilot channels. Background technique [0003] figure 1 is a block diagram showing the configuration of a transmitter in a spread spectrum communication system employing a conventional differential phase shift keying (DPSK) modulation method. The DPSK encoder 102 differentially modulates the input baseband data. Band extender 104 band-extends the differentially modulated data by multiplying the data by a PN code output from PN (Pseudo Noise) code generator 103 . The output of the band extender 104 passes through ...

AI Technical Summary

Problems solved by technology

However, in the above-mentioned DPSK modulation spread spectrum communication system, 1-bit error during demodulation can cause 2-bit error, which leads to system performance degradation

Another problem is that it is difficult to adjust the synchronization of the PN code in the receiving part, because in fact the modulated PN code signal is not the pure PN code being transmitted

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