Abstract: A transmission output detecting circuit for use in a radio transmitter-receiver of a TDD communication system having a TDD switch for connecting a transmission system to an antenna system in a transmitting period and for connecting a reception system to the antenna system in a receiving period; comprising a detection means for detecting transmission output on the basis of leakage power of the TDD switch in the transmitting period. The transmission output can be detected with low power consumption without making the transmission power branch out.

Abstract: A multiband mobile unit communication apparatus is disclosed which comprises: an antenna for receiving L FRQ bands of M radio wave SIGs modulated by N modulating methods, M>L, M>N, N≧L; a frequency synthesizer for generating a LO SIG; an IF SIG generation CKT for generating M IF SIGs using the LO SIG, the FRQ synthesizer generating the LO SIG such that the M IF SIGs have the same intermediate FRQ; a SW CKT for selectively outputting N IF SIGs modulated by the N modulating methods respectively out of the M IF SIGs; N filters for filtering outputs of N IF SIGs from the SW CKT and outputting N filtered IF SIGs respectively; a SW responsive to a SW CONT signal for selectively outputting one of the N filtered IF SIGs; and a quadrature demodulator for quadrature-demodulating one of N filtered IF SIGs and outputting baseband SIG. Different frequency bands of received signals are converted into IF SIGs having the same intermediate frequency.

Abstract: In a high frequency power amplifier reduction of current consumption at the time of power down and an improvement in distortion of linearly modulated wave at the time of generation of its maximum output are automatically effected at the same time. Part of the high frequency output of a pre-stage amplifier is derived by a directional coupler inserted in the input part of a post-stage amplifier to be superposed through a DC voltage generator circuit on a gate bias voltage applied to the gate terminal of an FET in the post-stage amplifier, so that the gate bias voltage can be automatically controlled to its optimum value according to the output level required for the power amplifier.

Abstract: A control circuit for a transmission output is used in a TDMA system radio transmitter or the like and can control a transmission output burst wave stably with high accuracy over a wide range. There is provided a closed loop system in which part of the transmission output is taken out and detected to be compared with a reference voltage to control a power amplifier and an open loop system for controlling a drive amplifier connected to an input of the power amplifier, so that a wide range operation of the transmission output and multi-stage control are attained by combining controls of both the loops.

Abstract: In a radio transmitter, a part of an output of a transmission output amplifying circuit is supplied to a variable attenuating circuit and an output of the variable attenuating circuit is supplied to a detecting circuit. An output of the detecting circuit and a reference voltage are compared and a control voltage is given to the transmission power amplifying circuit in accordance with the result of the comparison, thereby controlling the transmission output. By controlling the attenuation amount of the variable attenuating circuit, the transmission output can be controlled over a wide dynamic range with a high reproducing fidelity.

Abstract: A coaxial dielectric resonator for VHF-UHF band comprises a generally cylindrical dielectric body having a thick portion, a thin portion and a stepped portion interposed between the thick and thin portion. The outer and inner surfaces of the dielectric body are respectively covered by outer and inner conductors. Thus the resonator can be regarded as a series circuit of two lines having different impedance from each other. The axial length of the thick and thin portions may be changed so as to change electrical characteristics. With the provision of thick and thin dielectric portions, the spurious resonance frequencies may be set to values other than integral multiples of the fundamental resonance frequency. The stepped portion may be rounded or replaced with a tapered portion so that impedance gradually changes at the stepped or tapered portion from the thick portion to the thin portion or vice versa.

Abstract: A coaxial resonator comprising an outer conductor with closed and open ends, an inner conductor concentrically disposed in the outer conductor to establish a short circuit at the closed end and an open circuit at the open end, and a dielectric member mounted in the open circuit between the outer and inner conductors. An electrode is connected to the open circuit end of the inner conductor with a spacing from the dielectric member. A conductive plate, having a smaller surface area than that of the electrode but larger than the transverse cross-sectional area of the inner conductor, is provided between the dielectric member and the electrode. The dimensions of the conductive plate is appropriately chosen to accommodate frequency variations which might occur as a result of a connection with an external circuit.