| Monobit receiver has played an important role in the field of electronic reconnaissance since worked out.The advantages of the monobit receive include wide instantaneous bandwidth,fast response speed,simple structure,small size,low power consumption,and simple data processing,which make it meet the most requirements of the modern electronic reconnaissance.Moreover,the existing monobit receiver has been able to realize the direct sampling of radio frequency(RF)signals within the frequency band of 0.4～18 GHz,which is an important advantage that other contemporary receivers cannot achieve.However,the instantaneous dynamic range(IDR)of the monobit receiver is low,which makes it unable to process two simultaneous signals with large amplitude difference.In addition,with the increase of the sampling rate of the monobit receiver,the traditional monobit frequency measurement technology has been unable to meet the demand of accurate frequency measurement for the monobit receiver which has high-speed sampling.Therefore,in order to improve the two-signal instantaneous dynamic range and frequency measurement accuracy of the ultra-wide-band(UWB)monobit receiver,the characteristics of monobit signal,monobit frequency measurement technology,and the related digital design methods are studied in this paper.Firstly,in order to improve the two-signal instantaneous dynamic range of monobit receivers,this paper focuses on the study and analysis of the amplitude relationship among the harmonic components,intermodulation components,and fundamental components in two-tone monobit signals in detail.The research in this paper elucidates the primary cause why the two-signal instantaneous dynamic range of the traditional monobit receivers is only 5 dB.Meanwhile,this paper proposes that the efficient method to improve the two-signal instantaneous dynamic range of monobit receiver is to accurately identify or suppress the third harmonics of the stronger signal,so that the instantaneous dynamic range can be increased to 10 dB.If the fifth harmonic of the stronger signal can be further suppressed,the two-signal instantaneous dynamic range can be increased to 12 dB.However,when the power ratio of the two input signals is greater than 12 dB,the power of the intermodulation product produced by 1-bit quantization almost equals that of the weaker signal,so that it is difficult to accurately detect the weaker signal by the current technical means.As a result,it is proposed in this paper that the maximum instantaneous dynamic range of the monobit(1-bit)receiver should be 12 dB under current technology.Based on the above analysis: 1)The distribution characteristics of third harmonics in 1-bit signals of different frequencies are analyzed and studied in detail to deduce the frequency ranges which do not contain three harmonics,so that a kind of monobit frequency measurement without third harmonics technology is proposed.This technology can increase the two-signal instantaneous dynamic range from 5 dB to 10 dB while maintaining the original advantages of traditional monobit receivers.2)In order to further suppress the high-order harmonics in 1-bit signals and overcome the defects of the existing compensation matrix(CM)technology which can only be used under the premise of known signal frequencies,an adaptive compensation matrix technology is proposed in this paper.In the case of unknown signal frequency,the proposed technology can accurately suppress the high order harmonics of 1-bit signal in the frequency domain through the generated compensation matrix obtained by decimation in time domain,so that the two-signal instantaneous dynamic range of the monobit receiver can be effectively improved,which has high value of theoretical research and engineering application.By applying this technology in the monobit frequency measurement without third harmonics technology,the instantaneous dynamic range of the monobit receiver can be further increased to 12 dB.Secondly,in order to improve frequency measurement accuracy of UWB monobit receiver,the digital channelization technology based on STFT(short-time Fourier transform)is studied and popularized.Aiming at solving the problems of the low frequency resolution and serious energy leakage between adjacent channels from the STFT channelization technology,a high-efficient joint time-frequency detection technology is proposed,which can effectively improve the frequency resolution,reduce false alarms and missing detection caused by channel energy leakage,while keeping the good time resolution of STFT channelization system.Thus,the processing and resolution capability of STFT channelization system for simultaneous multiple signals can be improved.During researching the STFT channelization technology,a kind of special design method of reconfigurable STFT channelization is also put forward in this paper.This method can adjust the bandwidth of sub-channel by changing the window function and the overlap rate of sampling window without changing the original design structure of channelization,which can solve the problem of signal crossing channel to a certain extent.On basis of the above study,in order to make UWB monobit receiver get both better two-signal instantaneous dynamic range and frequency measurement accuracy,a kind of monobit digital channelization frequency measurement technology is proposed,which is achieved by combining the adaptive compensation matrix technology with the joint time-frequency detection technology and through analyzing the relationship between the intermodulation components and the fundamental components.The proposed technology can increase the two-signal instantaneous dynamic range of UWB monobit receiver to 11 dB meanwhile improving the frequency measurement accuracy of it.In addition,in order to give full play to the advantages of high-speed sampling and simple data of monobit receivers,a kind of efficient monobit digital channelization design method is worked out.Based on this method,a kind of a high-efficient monobit dynamic channelization frequency measurement technology is also proposed in this paper.The presented design method of monobit channelization can completely remove the multiplication operation required in the traditional channelization and generate the required intermediate frequency correctly,which greatly reduces the realization difficulty and resource consumption of monobit channelization.The proposed monobit dynamic channelization frequency measurement technology can give full play to the advantages of ultra-wide instantaneous bandwidth(0.4～18 GHz)and fine time resolution(20/3 ns)of the 38.4-GSPS(gigabit sampling per second)monobit receiver,while making it have excellent frequency measurement accuracy(≤0.1465 MHz)and the potential ability to intercept simultaneous multiple signals.It is worth mentioning that the technology related to the design of monobit receiver from the point of engineering application is studied in this paper.Among them,as a supplement and extension of Rife frequency estimation algorithm,the Rife estimation formula for Hamming window is deduced.Meanwhile,aiming at the problem that Rife algorithm is sensitive to noise,a kind of evaluation criterion is established and used to define the applicative range of input SNR and confidence interval of Rife estimation algorithm,which provides a certain reference for the engineering application of Rife estimation method;An efficient design method of fully parallel SRFFT(Split-radix Fast Fourier Transform)based on FPGA is proposed in this paper,where an assistant design flow diagram is also created.The difficulty of engineering design of SRFFT can be greatly reduced by using the proposed method in combination with the assistant design flow diagram,which also improves the software design efficiency of SRFFT within 512points;The relation between false alarm probability and threshold of monobit receiver is given quantitatively for the first time under FFT with different length,which provides a basis for the threshold design of monobit frequency measuring system.Finally,a 38.4-GSPS monobit receiver,which is independently designed,is used to verify the key technologies proposed in this paper.The test results show that the proposed technologies have high efficiency and stable performance,and can effectively improve the two-signal instantaneous dynamic range and frequency measurement accuracy of the traditional monobit receiver. |
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