| Ultra-wideband (UWB) has become a suitable candidate for high-data rate, short range communications. Chirp UWB system applies chirp spread spectrum technology to UWB wireless communication system. Chirp UWB system has various merits; meanwhile there are some remaining problems to be solved such as high complexity of hardware implementation, energy dispersion caused by multi-path channel with huge taps and high sensitivity to time offset. This dissertation focuses on signal detection scheme.In the traditional time delay estimation scheme, we ignore the non stationary of chirp signal, now we study the delay estimation scheme suit for chirp signal. We make time delay a frequency parameter of a sin function. Then we estimate the frequency of the sin function. At last we compare the performance of these time delay estimation schemes.Chirp UWB has two modulation schemes: binary orthogonal keying (BOK) and direct modulation (DM). DM allows many possible modulation methods to be employed. Differential Phase Shift Keying (DPSK) is a suitable method. Auto Correlation Demodulation (ACD) simplifies the implement because it doesn't need channel estimation scheme and chirp match filter in the receiver. But the performance is poor, because both chirp dispread reference and phase reference are dirty with noise. So that we propose two improved ACD detection structure. The first one is multiple-symbol joint detector and it is based on Maximum-Likelihood (ML) decision. The upper bound of the BER is given. The second is feed backed structure. The simulation shows that the BER performance of two proposed ACD schemes outperform the original ACD scheme with only a slight increase in complexity, and they can achieve similar BER performance.The UWB channel impulse response (CIR) contains a large number of resolvable multipath components, especially in indoor environments. However, making good use of these signal components is not straight-forward. Firstly, we study the Rake receiver in Chirp UWB system, Huge taps of rake receiver make the implementation quite impossible for power limited equipment. Then we consider a signal focusing technique: time reversal which can shift part of receiver complexity burden to the transmitter side. To simplify implementation of the channel estimator and time reversal filter, reduce-bit quantization is considered. At last, we derive the BER performance formula of SISO and MISO system, and evaluate performance lose caused by reduce-bit quantization. |
