Application Of Delta - Sigma Modulator In Concurrent Dual - Band Transmitter

With the wideband and multi-band radio system applications becoming more widely,the non-contiguous spectrum aggregation technology has been more and more important. In the transmitter systems the modulator is an indispensible part.Besides,Delta-Sigma Modulator has some prominent advantage, which can achieve high resolution data conversion and signal-to-noise ratio. And it can reduce noise within the signal band to achieve good noise shaping effect by oversampling and noise shaping technology. However, the modulators applied to single-band transmitters with narrow bandwidth can not achieve non-contiguous spectrum aggregation, which will not meet the application of wideband and multi-band radio transmitter systems. Therefore, researching a proper modulator used in wideband and multi-band radio transceivers systems is very important.For broadband and multi-band system application,firstly,the thesis analyzes a kind of modulators applied to single-band transmitters.By selecting parameters and determining the structure of modulators,we get the noise transfer function.Then we employ MATLAB/Simulink to mode and simulate the single band modulator.The results show that two large noise attenuation bands.The one is the band occupied by the signal itself and another one is idle band away from the signal (ie noise frequency notch).Then,the thesis designs a Delta-Sigma Modulator applied in concurrent dual-band transmitters.Due to the different carrier frequencies,we discuss three conditions.Then we use the carrier frequencies to plan the position of noise frequency notches of the two modulators. Based on the two notches we get the noise transfer function and depending on the function we determine the type of Low-pass or Band-pass modulators.By simulation of the two modulator,the results show that calculating the noise frequency notch can math another needed the frequency. Two different signals can be concurrently transmitted without interference and achieve non-contiguous spectrum aggregation.Besides, the type of two-way modulators is the same type or hybrid types of LPDSM and BPDSM.Finally,the thesis analyzes the non-idealities of each module effecting on the performance of the modulators.By simulation non-ideal module,then compared with ideal module,the performance has decreased, but the non-ideal modulator can be applied to concurrent dual-band transmitter systems.