Development And Analysis Of Radio Frequency Modulation Channels For Modulated Wideband Converter And Research On Calibration Methods

The modulated wideband converter(MWC)which can deal with the problem of blind sub-Nyquist sampling of multiband signals is an architecture of Analog to Information Conversion(AIC)based on Compressed Sensing(CS).The MWC system is consist of mixing,filtering,sampling in low speed and algorithm reconstruction,which means the hardware in modulated channel only has power splitter,mixers and low-pass filters.So the physical structure is simple to implement.Although numerical simulations of the sub-Nyquist algorithms proved to be very successful,actual implementation of the off-the-shelf devices with a lot of non-ideal factors has a huge influence on recontruction signal,especially in radio frequency system.This dissertation focuses on the design of radio frequency modulation channels,the analysis of the influence of devices' non-ideal characteristics on MWC system,the research of calibration methods and the prove for the spectrum sensing of multiband signals.The details are as follows:1.The research on the theory of MWC system and the choice of modulation channels' paramaters.The specific function of mixing,filtering and sampling in MWC system is firstly analysed in this dissertation.Then the expansion principle of physical channels is introduced.And the process of reconstruction and the consitions to perfect recover are investigated and pointed out.Finally,the design criteria of radio frequency modulation channels for MWC system is confirmed according to the parameters of multiband signal needed to be tested.2.The overall scheme of modulation channels is designed according to the design criteria.The device model of power splitter,mixer,lowpass filter and amplifier is chosen and their non-ideal characteristics are investigated,such as the standing wave and insertion loss of power splitter,the standing wave,conversion loss and isolation of mixer,the standing wave and frequency response characteristic of lowpass filter,etc.And the plan of test platform is designed which includes signal source,adio frequency modulation channels,sampling module and high-speed pseudo-random sequence generator.3.The non-ideal characteristic models of physical modulation channels are simplified depending on the hardware and the effect of them on MWC system is studied in theory.Thus the compensating method of non-ideal lowpass filter is proposed to deal with the non-ideal frequency response characteristic of lowpass filter compared to ideal filter.The calibration method based on sine wave excitation signal is applied to obtain the real sensing matrix.The method of successive phase shift correction in expanding MWC system is proposed to relax this limitation,which is that the phase of excitation signal in acquiring the sensing matrix must be known.Finally,the validity and feasibility of these methods is demonstrated by numerical simulation of the non-ideal factors models.4.The radio frequency modulation channels for MWC system and test platform are built.The sub-Nyquist sampling of multiband signal and the non-ideal factors of devices are experimented in this platform.The results show that these modulation channels can accomplish the compressive sampling of multiband signal modulated by Quadrature Phase Shift Keyin with a total sampling speed of 400MSa/s,whose Nyquist frequency is up to 2GHz and the carrier frequency is unknown.And the location and the width of the multiband signal's spectrums is recovered in a high probability with these calibration methods.The harmful effect of non-ideal factors of devices on MWC system is demonstrated by experiments.This paper summarizes the reasons,influence and calibration methods of non-ideal factors of devices in MWC system in the last.