Baseband Design And Implementation Of A DSP Based Digital SSB Receiver

Shortwave communication has been widely used in various regions such as government and military communications. As the rapid development of new technologies, shortwave communication is enterring a brand new digital shortwave era. Recently, researchers have focused on fading antagonizing and constructing a stable data link on unstable shortwave channel.The paper focuses on the baseband part of a SSB communication system. The system which works in burst mode can adaptively select frequency and modulation. An adaptive sweep algorithm based on FTSK and DSSS(ADSS-FTSK) is proposed to capture the frequency and modulation on the receiver side. Simulations and tests show that the algorithm is more robust compared to traditional PSK based DSSS in a shortwave fading channel. An united synchronization capture and demodulate algorithm(USCD) which uses barker code as capture assistantance is proposed to transmit under a deeply fading channel. Compared to ordinary demodulate algorithm, USCD can reduce BER up to 50%. PSK modulation is used when the channel is flat and corresponding PLLs are designed and implemented. A new bit synchronization algorithm based on statistic and intelligent CLK recovery is proposed. Equalization is used to estimate and compensate the inter-symbol-interference. The whole system is implemented on DSP platform and tests show that the system is steady and all parameters have achieved or exceeded the project's requirement.