Microsatellite navigation system design based on 21-centimetre spectral line

This paper introduces the principle of microsatellite navigation based on 21-centimeter spectral line emission and the instrumental design of the on-board navigation receiver. The essence of this idea is to measure the Doppler frequency shift received by the spacecraft with respect to the 21cm spectral line source. From the analysis of the Doppler frequency shift, the relative velocity between the source and the observer can be derived. The velocity integral can estimate the position, which can be enhanced with a Kalman filter. The similar processes in the three dimensions enable the prediction of the satellite's position in the space, if no less than three 21-centimeter spectral line sources are simultaneously observed. Also, this paper proposes the front-end design of the navigation receiver for microsatellite navigation. A receiver design with 37 basic modules aligned in hexagon is proposed, and each module consists in a micro-patch antenna, a two-stage low noise amplifier, a phase shifter and a mixer. The numerical simulation showed that the system performance in the hexagon alignment can implement the beam scanning from -45 degree to 45 degree using 6 bits and provide a system gain of 31.7dB.