The Research Of Digital Voice Encrypting And The Aplication In Marine VHF

VHF devices take an very important part in wireless marine communications. They mainly use analog signals. And now, marine wireless telephone use open voice communication., so it can not provide safe and secret communication in some special conditions, such as in the fish culture secret communication. Digital voice encrypting have more advantage than analog voice encrypting, such as having low interference, high performance of voice encrypting, and high quality of voice and so on. So using digital speech encrypting is a good selection to solve those problems.This paper , we use embed technique, digital speech compression t technique, digital encrypting technique, GMSK technique, micro-electronics technique ,and design one scheme of a digital speech encrypting terminal system .Because VHF voice channel is a narrow band (25KHz), so in the system we design hardware circuit based on AMBE speech compression to realize low digital speech code rates. We use GMSK modem to complete data transmission in the wireless channel .The whole system is in the control of digital processor (TMS320VC5402). Our design includes:1) Audio frequency collection , amplifying and the design of interface circuit.2) We use voice codec AMBE-2000 based AMBE algorithm, and achieve low voice code rate with high voice quality.3) We designed the high speed hardware circuit of DSP, and ensured the DSP working well.4) We programmed on the DSP and realized to functions: the data exchange between DSP' McBSP and AMBE-2000;the communication of DSP and GMSK MODEM;digital voice frame processing;DES algorithm.We design and. realize the digital speech encrypting terminal system finally.