M.Sc. Tezi Görüntüleme | |||||||||||||||||||||
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Summary: In order to prevent the unwanted eavesdropping to the communications over the analog handheld two-way radios, a low cost, small voice encryption unit with easyintegration capability through the radio microphone and speaker jacks has been designed. Before the design phase, subjects like analog handheld two-way radio, two-way radiocommunication, modulation types and cryptology have been studied. C programming language and dspic microprocessor is used in the design. Hardware with embeddedsoftware was used in the design approach. Before the audio signal is sent to the microphone input of the transmitting radio,signals are digitized, encrypted and converted back in to the analog signal by the Digital Encryption unit.On the receiving end, the encrypted analog audio signal levels are adjusted through an equalizer in order to attain the appropriate logic–1 and logic–0 signal levels. Theadjusted signals are digitized, decrypted and converted back in to the analog audio signal by the Digital Encryption unit.The developed Digital Encryption unit has been tested in the laboratory environment as well as with the PMR handheld two-way radios in the UHF band and successful resultshas been achieved. Key Words: Two Way Radio, Analog Two Way Radio, Two Way Radio Communication, Half-Duplex, Push-to-Talk (PTT), Secure Communication, MSK, Crypto, Digital Crypto, Encryption, Audio Encryption. |