Research On Detection And Modulation For The Extended Distance Chirp Ultra-Wideband System

Due to the low interception, high transmission efficiency and high flexibility in spectrum design, the extended distance Chirp Ultra wideband(Chirp-UWB) system has broad application prospects in many wireless communication domains. With the extension of communication distance, Chirp-UWB communication system will be faced with much more complicated problems: 1)larger signal dynamic range will lead more time to capture delay information for receiving signal; 2)intricate transmission environment will need multi-rate communication to improve transmission capacity. Therefore, this paper aims at transmission technology of extended distance Chirp-UWB system in-depth research.This research is supported by the National Science and Technology Major Projects—Application and Demonstration of Extended Distance UWB, which aims at detection and modulation of Extended Distance Chirp-UWB system in-depth research. First, in order to reduce the time of capture delay information, a signal detection method based on false-real peak is proposed; second, in order to solve the low efficiency problem of Chirp-BOK modulation, an UWB wireless communication system model based on Chirp-BOK-DQPSK modulation is proposed, third, aiming at the extended distance communication need multi-rate communication to improve transmission capacity, an UWB multi-rate communication system model based on Chirp-MBOK modulation is proposed; finally, An extended distance Chirp-UWB signal generation scheme based on CORDIC algorithm is proposed. The main content is listed as follows:1 A signal detection method based on false-real peak is proposed. Through analyzing the phenomenon of false peak and real peak on the spectrum domain after active spectrum compression of receiving signal, we found that either false peak or real peak was detected, we could estimate the delay information of received signal, which would help to reduce the receiver sampling rate for the ADC. We also discovered false peak and real peak have symmetry characteristics on spectrum domain, when Chirp-UWB signal have the same time delay or ahead of local signal, which would reduce signal average capture time. The paper also proposed threshold crossing/maximum selection capture criterion which is based on false-real peak signal detection method, effectively improving the signal detection performance.2 An UWB wireless communication system model based on Chirp-BOK-DQPSK modulation is proposed. The system utilizes the features that the Chirp signal real part and image part, Up-Chirp and Down-Chirp both have favorable autocorrelation and cross-correlation characteristics, and realizes the transmission function that one symbol carries three message bits. The simulation results show that the system can efficiently improve the transmission rate with some reduction of the BER performance.3 An UWB multi-rate communication system model based on Chirp-MBOK modulation is proposed. Based on the steady code rate of Chirp-UWB and determinate Chirp signal spread spectrum gain, the variable mixed gain can be obtained by adjusting the factor of variable orthogonal spread spectrum sequence. And then the multi-rate communication of system can be realized. The simulation results show that, under the same information rate, the performance of Chirp-BPSK-UWB system BER is better than Chirp-MBOK-UWB system, however, the receiver of Chirp-MBOK-UWB system have lower requirement, more simple structure and higher feasibility.4 An extended distance Chirp-UWB signal generation scheme based on CORDIC algorithm combined with orthogonal modulation and frequency multiplication is proposed. The scheme uses CORDIC algorithm to generate digital baseband Chirp signal, and then though orthogonal modulation and frequency multiplication to expand the signal bandwidth, which satisfies UWB communication requirement. Compared with look-up table method to generate digital baseband Chirp signal, the scheme consumes a little more logic units, but saving much storage resource. Especially, when system needs high frequency precision, CORDIC algorithm scheme is a good choice.Finally, based on the research of the above problems, Chirp-UWB signal generation module, the false-real peak signal detection module and Chirp-MBOK modulation and demodulation module were designed and realized. Through debugging on the FPGA, experimentation results show rationality of the analysis of the paper.