Abstract: An antenna device corresponds to a plurality of radio communications systems and frequency bands, can simultaneously carry out a reception and a transmission of different radio communications systems, and is capable of using antenna diversity by a simple construction. An antenna device comprises a first antenna matching with first, second, and third frequency bands, a second antenna matching with the third frequency band, a diplexer and the like. For signals of the first frequency band, a high-frequency switch circuit connects a transmitter or a receiver to the diplexer by switching. For signals of the second frequency band, an additional high-frequency switch connects a receiver or a transmitter to the diplexer by switching. For signals of the third frequency band, the additional high-frequency switch circuit and a further additional high-frequency switch circuit connect the second antenna or diplexer to a transmitter/receiver by switching.

Abstract: An object of the present invention is to provide an antenna device which corresponds to a plurality of radio communications systems and frequency bands, which can simultaneously carry out a reception and a transmission of different radio communications systems, and which is capable of using antenna diversity by a simple construction. An antenna device comprises a first antenna (1) matching with first, second, and third frequency bands, a second antenna (2) matching with the third frequency band, a diplexer (3) and the like. For signals of the first frequency band, a high-frequency switch circuit (4) connects a transmitter (8) or a receiver (7) to the diplexer (3) by switching. For signals of the second frequency band, the high-frequency switch (5) connects a receiver (9) or a transmitter (10) to the diplexer (3) by switching.

Abstract: A phase comparator (106) compares a phase of the output signal of the quadrature modulator (104) with the phase of the signal obtained by frequency-converting the output signal of a first VCO (101) via the second VCO (102) and the first mixer (108). A PLL modulator includes a low-pass filter (107) filters a component below a predetermined frequency of the output signal of the phase comparator (106) and supplying the resulting signal to the frequency control terminal of the first VCO (101). The output signal (TS1) of the first VCO (101) is a modulated signal conforming to a modulation system having a constant envelope waveform, while the output signal of the quadrature modulator (104) is input to the first band-pass filter (110) and the output signal (TS2) of the first band-pass filter is a modulated signal conforming to a modulation system accompanied by an amplitude component as information.

Abstract: A phase comparator (106) compares a phase of the output signal of the quadrature modulator (104) with the phase of the signal obtained by frequency-converting the output signal of a first VCO (101) via the second VCO (102) and the first mixer (108). A PLL modulator includes a low-pass filter (107) filters a component below a predetermined frequency of the output signal of the phase comparator (106) and supplying the resulting signal to the frequency control terminal of the first VCO (101). The output signal (TS1) of the first VCO (101) is a modulated signal conforming to a modulation system having a constant envelope waveform, while the output signal of the quadrature modulator (104) is input to the first band-pass filter (110) and the output signal (TS2) of the first band-pass filter is a modulated signal conforming to a modulation system accompanied by an amplitude component as information.