Abstract: A TDD digital radio communication system includes a local oscillator for generating a local oscillation frequency being N times the transmission intermediate frequency and a frequency divider for dividing the local oscillation frequency by N. The frequency divider is enabled in the transmission mode to generate the transmission intermediate frequency and is disabled in the reception mode to completely stop generating the transmission intermediate frequency, so as to prevent interference with the reception intermediate frequency.

Abstract: A radio receiver, and a method therefore, for efficiently suppressing attenuation properties of a low frequency signal, in an analog frequency modulation type radio communication system. The radio receiver includes a first down-converter for mixing a modulated, high-frequency signal received by the radio receiver and a predetermined local oscillating signal to generate an intermediate frequency signal. A modulator modulates the predetermined local oscillating signal by an aural signal transmitted from the transmitter and generates a mixing signal for down-mixing the electrical signal representative of modulated, high-frequency signal. The mixed signal is then applied to the first down-converter. A second down-converter down-converts, in frequency, the intermediate frequency signal generated from the first down-converter into a baseband signal to generate the down-converted signal.

Abstract: A radio signal processing apparatus of a portable telephone which can share a first transmit/receive mode such as a digital/analog (D/A) compatible mode and second transmit/receive mode such as a personal communication service (PCS) mode.

Abstract: A transceiver signal processor for a digital cordless communication apparatus adopts a heterodyning loop in order to improve the transmitting circuit and power efficiency. The transceiver signal processor adopts an orthogonal demodulation method for a first intermediate frequency, thereby allowing a single reference loop. Since the reference loop itself need not be switched, a frequency drift problem is fundamentally removed.

Abstract: 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.

Abstract: 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.