Compatible Meteorological Sounding Receiver Developed

This paper presents a new type compatible FM receiver designed for 1680 MHz band radio sondes (GTS1 and Vaisala's RS-80) which are widely used in the meteorology monitoring. The structure of the sonde and the signal characteristics is analyzed, according to which a new method of signal scanning and tracking is proposed. A prototype receiver is realized and the measurement results are up to the expectation.In order to realize the required specification and the compatibility of the two kind of radio sondes, some critical problems have to be solved which include:1. Thoroughly analyzing the construction of the sondes. The format of the data packet, the modulation type, the RF oscillation block and the directivity pattern of the antenna are carefully researched, based on which the receiver's specification are decided;2. According to the RF signal characteristics, the frequency discriminator is implemented by Gilbert multiplier cell and the signal scanning and tracking is accomplished though an Frac-N PLL block;3. Design of the low noise amplifier, the gain, noise figure and input third order intercept point are of critical importance to the total system's performance. Theoretic analysis and practical design details are presented.4. Using software temperature compensation technique to reduce the variation of RSSI output caused by temperature, which can improve the sensitivity of the receiver.5. Based on the received signal strength indictor and the amplitude of the demodulated signal, an algorithm for signal finding and tracking is realized with software temperature compensation technology.