M.Sc. Tezi Görüntüleme

Student: Sibel Arslan
Supervisor: Assoc. Prof. Dr. İsmail Hakkı ÇAVDAR
Department: Elektrik-Elektronik Müh.
Institution: Graduate School of Natural and Applied Sciences
University: Karadeniz Technical University, Turkey
Title of the Thesis: Digital Encryption on the Analog Handheld Two-Way Radios
Level: M.Sc.
Acceptance Date: 19/10/2009
Number of Pages: 69
Registration Number: i2101

      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 easy

      integration capability through the radio microphone and speaker jacks has been designed.

Before the design phase, subjects like analog handheld two-way radio, two-way radio

      communication, modulation types and cryptology have been studied. C programming

language and dspic microprocessor is used in the design. Hardware with embedded

      software 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. The

      adjusted 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 results

      has 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.