An antenna configuration includes a rod antenna and a helical antenna that are independently operable. The helical antenna is composed of a helical coil installed within an antenna housing mounted on a main body of a communication device. A feeding connector is electrically coupled to a bottom portion of the helical coil to thereby connect the helical antenna to a circuit of the communication device. The rod antenna is composed of a rod functioning as a conductive metal core wire. The rod is surrounded by the helical coil and the feeding connector and is extendable from and retractable into the main body of the communication device. When the rod is retracted into the main body, the helical coil operates as the exclusive radiating element and operation of the rod antenna is disabled. When the rod is extended from the main body, the rod electrically short-circuits and disables operation of the helical coil, and thereby operates as the exclusive radiating element.

A transmitting/receiving signal processing circuit incorporates a frequency discrimination demodulator and a frequency synthesis local oscillator having a heterodyne phase locked loop for high speed switching. The transmitting/receiving signal processing circuit is used in a digital cordless communication device and has a transmitter for converting a signal input through a speaker and transmitting the converted signal as a radio wave via an antenna. A receiver converts a signal received by the antenna and then transmits the converted signal to a user in a time division communication system using a single frequency channel for transmission and reception according to constant time periods. A frequency synthesizer is also provided and includes a first phase lock loop for synthesizing a reference frequency for channel conversion; a switching stage providing a local oscillation signal from the receiver as a heterodyning source in a receiving mode, and providing a signal multiplied by the reference frequency as the heterodyning source in a transmission mode; and a second phase locked loop connected between the first phase locked loop and the receiver, for receiving the heterodyning source and generating transmitting/receiving frequencies in the transmission/receiving modes, respectively.