.pcm / Fm Re-entry Adaptive Equalization In The Telemetry System

The Pulse Code Modulation/Frequency Modulation (PCM/FM) is widely used in most Reentry Remote Sensing (RRS) system at the present time in our country. When transmitting signal is below 500 Kbps, increasing the system power can reduce the bit error rate (BER) for the signal suffering only flat fading. But when the bit rate is above 1 Mbps, the signal suffers frequency select fading, which causes the serious intersymbol interference (ISI). Increasing the system power can't reduce the BER. We can reduce the ISI and noise by elaborately designing transmitting filter and the receiving filter when the channel is known and unaltered. However, the factual channel is time-varying and not known entirely. So the ISI is always existent. An adaptive filter is needed to equalize the channel fading before sample-decision detector in the receiver. According to the channel model and a short time between the missile outs from the black area and touchdowns, we research a simple, flexible and fast adaptive equalizer and the dsp realization. It equalizes the channel and reduces the system BER to satisfy the urgent test task requirements.The main content and contribution in this dissertation are as follows:1. The RRS wireless channel characteristic and the two-path model are described and a simulation model of the PCM/FM RSS system is introduced.2. Introduced the adaptive equalization technique into the RSS system.3. Comparing several adaptive equalizers and using the combined DFE/MLSE equalizer based on predicted signal to compensate the RSS channel. Simulation results suggest that the DFE/MLSE is greater than DFE and LE in performance and is simpler than MLSE-VA in complexity.4. Using the TS203 of ADI's TigerSHARC series DSP to realize the DFE/MLSE.5. Designed an experimental circuit board and realized the validating of the equalization system.