DEVELOPMENT OF HIGHLY-RELIABLE SPREAD-SPECTRUM WIRELESS MODEM

办公自动化、工厂自动化、安防控制系统、计算机通信、远程控制等领域对无线局域网的需求不断增加。扩频通信系统以其多址、抗干扰、低截获概率、安全、防检测等优良性能成为无线局域网中最具发展前景的通信系统。由于在SS系统中，使用快速PN码将消息的传输带宽扩展到远远超过信息带宽的范围，因此可以获得S/N恢复，即所谓的过程增益。扩频导致发送端和接收端PN码的关联和同步困难。使用表面声波（SAW）器件，如卷积器或相关器，SS系统可以简单而紧凑地实现，因为同步和相关可以异步进行。本工作的目的是：(1)利用一位研究人员开发的高效SAW卷积器开发一种新型紧凑型异步SS调制解调器；(2)开发一种基于aln /Al_2O_3组合的基本单片解调器。在这项工作中，为了提高使用SAW卷积器的异步SS调制解调器的性能，我们提出，设计和评估了(1)DBM解调方法，(2)时间窗检测方法和(3)基带误差校正方法。在此基础上，我们设计并实现了基于声波卷积器的2.4GHz全双工异步SS调制解调器。我们在远程控制、无线数字语音通信和无线手持终端等新型SS调制解调器方面取得了进展。我们成功地沉积了2英寸直径的外延AlN薄膜。al_2o_3衬底的MOCVD。AlN具有高SAW速度（5910m/s）、中等力学耦合系数（1%）和零温度延迟系数的特性。在al_2o_3衬底上设计并制作了SAW相关器和SAW延迟线。我们已经演示了直接检测2.4GHz SS信号到基带数据。采用声波卷积和相关器的SS无线调制解调器在无线局域网中具有很大的应用潜力。少

The demand for wireless LAN for office automation, factory automation, security control system, computer communication, telecontrol, etc. has continued to increase. Spread spectrum (SS) communication system is the most promising for the wireless LAN, because of its excellent performance known as multiple access, anti-jamming, low probability of intercept, security and anti-detecting. Since the transmission bandwidth of a message in the SS system is spread far in excess of the information bandwidth using a fast PN code, S/N recovery so called process gain can be obtained. Spreading the spectrum causes the difficulty in correlating and synchronizing the PN codes between transmitter and a receiver. Using SAW (Surface Acoustic Wave) devices such as a convolver or correlator, the SS system can be implemented simply and compactly because the synchronization and correlation can be carried out asynchronously.The purpose of this work is (1) to develop a new compact asynchronous SS modems using … More a highly efficient SAW convolver, which has been developed by one of the investigators, and (2) to develop a fundamental one-chip demodulator on the basis ofAlN/Al_2O_3 combination.2.4 GHz band has been recently approved for SS communication in Japan as well as in USA.In this work, in order to improve the performance of the asynchronous SS modem using the SAW convolver, we have proposed, designed and evaluated (1) a DBM demodulation method, (2) a time window detection method, and (3) a base band error correction method. On the basis of these results, we have designed and implemented 2.4GHz full-duplex asynchronous SS modem using the SAW convolver. We progress toward the new SS modems for telecontrol, wireless digital voice communication and wireless handy terminals, etc.We have successfully deposited on epitaxial AlN films on 2-in.-diam. alpha-Al_2O_3 substrate by MOCVD.AlN features the high SAW velocity (5910m/s), moderate mechanical coupling coefficient (1%) and zero-temperature-coefficient-of-delay characteristics. The SAW correlator and SAW delay line on a AlN/alpha-Al_2O_3 substrate were designed and fabricated. We have demonstrated direct detection of 2.4GHz SS signal to base band data.The SS wireless modem using the SAW convolver and correlator has a great potential for wireless LAN. Less