An intermediate frequency modulator using direct digital synthesis techniques for Japanese Personal Handy Phone (PHP) and Digital European Cordless Telecommunications (DECT)

Transmitters for Japanese Personal Handy Phone (PHP) and Digital European Cordless Telephone (DECT) often use analog I-Q modulators. This paper presents a direct digital synthesis technique suitable for both PHP and DECT applications. Because of the Time-Division-Duplex (TDD) structure of PHP and DECT, transmitter intermediate frequency (IF) signals can be generated at the same frequency as the receiver´s IF´s. This permits sharing of certain IF filters and reduces transceiver size and weight. A frequency plan that minimizes the digital processing required for the generation of a modulated intermediate frequency carrier is presented. Measured transmitter performance for the PHP is provided. Finally, the complete transmitter is presented as part of a set of integrated circuits for the PHP and DECT