Fine Tuning of Data Rate Enhances Performance of a Chirp Spread Spectrum System

Operating a fast reliable chirp spread spectrum data transmission system, a tradeoff between interference reduction capability, multipath resistance and data rate have to be made. Transmitting overlapping chirp signals yields interference from the cross correlation terms if binary orthogonal keying is transmitted. By the example of a system for application in the 2.45 GHz ISM band with data rates of 2 to 20 MBps, the necessity of the proper choice of the data rate is shown. Shifting the data rate, due to the large interval of overlap, constructive and destructive interference appears periodically. This of course endangers to overdrive the amplifiers. On the other hand the interferences influence the envelopes to detect in linear mode too. So, if the data rate is chosen well, good performance even for high clock rates can be achieved with a low cost system. For the relation of data rate and system's performance, simulations and preliminary experimental results are shown.