A Chirp-Transform Based Broadband And Low Power Consumption Spectrum Analyzer

In the development of space exploration,deep space exploration of planets and small objects including asteroids and comets is an important direction.Using millimeter wave terahertz spectrometers for atmospheric,ejecta,volatiles,and surface composition and state detection is an important means of detection.For deep space exploration,traditional real-time spectral analysis techniques based on high-speed sampling and digital Fourier transform have great limitations due to the stringent requirements in the field of deep-space detection such as volume,mass,power consumption,and radiation.With the development of surface acoustic wave filter,the Chrip transform spectrum analysis technology based on the high time-bandwidth-product surface acoustic wave pulse compression signal processor has advantages in terms of volume,power consumption,quality,and anti-irradiation.It provides a new solution for the back-end spectrum analysis of deep space exploration.For deep space exploration needs,the main research purpose of this paper is to study the spectrum analysis technology based on the Chrip transform,carry out the system design and system simulation of the spectrum analyzer using high time-bandwidth-product surface acoustic wave pulse compression signal processor,and build the experimental system to perform design verification and realize spectral analysis functions.Firstly,we analyse the principle of the Chrip Fourier transform in detail.The Fourier transform of a signal can be obtained by first multiplying with a Chrip signal and then convolving with another Chirp signal.The key to Chirp signal generation is the SAW filter(also known as SAW pulse compression signal processor).The main research purpose of this paper is to analyze the spectrum analysis technology based on the Chrip transform in detail,use the high-time-bandwidth surface acoustic wave pulse compression signal processor to carry out scheme design and system simulation,and finally set up the verification system to perform spectrum analysis of the input signal.In several common structures of surface acoustic wave dispersion filters,surface acoustic wave with reflection grating array type pulse compression signal processors use different widths of grooves to reflect sound waves of different frequencies,so that the length of paths traveled by sound waves of different frequencies are different.The acoustic and electrical conversion realizes the different dispersion delay time of the different frequency electrical signals.This reflective grating array acoustic surface pulse compression signal processor has the characteristics of strong real-time signal processing ability,high reliability,small size,and good radiation resistance.It is the preferred choice for the deep space detection spectrum analyzer.During the design of the system,if we want to reach 100% work efficiency,we need two symmetrical branches to work with the radio frequency switch.In this paper,we choose a 4000 time-bandwidth product surface acoustic wave compression line,which bandwidth is 400 MHz and dispersion time is 10 us,to design a single branch system.the whole system is simulated and analyzed.The compression line without window can be used to obtain higher frequency resolution but high sidelobe levels.Sidelobe level can be compressed after the window is added,but the frequency resolution is reduced by about 1.4 times.The AD9914 was used as a widening line to generate a 800 MHz bandwidth and 20 us dispersion time Chrip signal.The entire spectrum analyzer system is built with Mini-Circuits' amplifiers and mixer modules.The real-time analysis bandwidth of the entire system is 400 MHz with a resolution of 100 k Hz.Power consumption is about 3.5W,Greatly better than spectral analysis technology based on high-speed digital sampling.The test results show that the Chrip transform spectrum analysis technology based on the high time-bandwidth-product surface acoustic wave pulse compression signal processor can meet the spectrum analysis requirements.And with the development of higher time-bandwidth-product surface acoustic wave filters,the spectral analysis technology based on the Chrip transform can achieve a real-time processing bandwidth of 1 GHz or even higher.