Abstract: In a cellular telephone provided with a receiving circuit of a direct conversion type, a passive low-pass filter is arranged between a mixer for an I-channel and a base band circuit for removing interference waves of or above a channel next to a channel neighboring to the I-channel, and another passive low-pass filter is arranged between a mixer for a Q-channel and the base band circuit for removing interference waves of or above a channel next to a channel neighboring to the Q-channel. Since the low-pass filters for removing the interference waves of or above the channel next to the neighboring channel are of a differential type, the circuit scale can be small, and the power consumption is small. Since the interference waves are removed by the passive low-pass filters and the active low-pass filters, only the desired channel can be reliably received.

Abstract: A level of a base band signal at an input side of a variable gain amplification circuit is detected by a logarithmic amplifier having a wide input voltage range at a start of an operation, a control unit then performs a coarse feedforward control on a gain of the variable gain amplifier based on the detected level and finds a level of an output of an A/D converter by a mean square deriving circuit and inputs the resulting signal to the control unit. Then the control unit performs a fine feedback control on the variable gain amplifier based on the detected level.

Abstract: In the portable telephone of the present invention, a transmission power upper limit value (STEPLIM) in accordance with temperature (T) is found (S1, S2), whether the transmission power set value (STEPn) of the next slot exceeds the upper limit (STEPLIM) or not is determined (S3, S4), and when it does not exceed, a control signal value (Vc) in accordance with the transmission power set value (STEPn) is applied to a variable gain block (11, 13) (S5, S7). When it exceeds the upper limit, a control signal value (Vc) in accordance with the transmission power upper limit value (STEPLIM) is applied to the variable gain block (11, 13) (S6, S7).

Abstract: In a mobile phone according to the invention, a sum of a power control amount (&Dgr;P) instructed by a base station and a sending power (Px) detected by a sending power detecting portion (15) obtained to calculate a sending power (Px′) for a next slot (S1-S3), it is determined whether the sending power (Px′) is equal to or lower than a maximum sending power (Pmax) or not (S4), a power control is performed in accordance with an instruction of the base station when a relationship of (Px′≦Pmax) is present (S5), a value X satisfying (Px′−X≦Pmax) is calculated when the relationship of (Px′≦Pmax) is not present (S6), and the sending power is changed by (&Dgr;P−X) (S7).

Abstract: A wireless terminal device includes a transmitting circuit, an isolator, a band pass filter, a switch, a transmitting antenna, a receiving circuit, a band pass filter, a switch, a receiving antenna, a high-pass filter, a low-pass filter and an input/output port. A transmission wave of a frequency is conveyed from the transmitting circuit to the input/output port via the isolator, the band pass filter and the low pass filter, and further to a vehicle antenna. Here, the transmission wave in the direction towards the receiving circuit is blocked by the high-pass filter. On the other hand, a reception wave of a frequency is conveyed from the vehicle antenna to the input/output port, and to the receiving circuit via the high-pass filter and the band pass filter. Here, the reception wave in the direction towards the transmitting circuit is blocked by the low-pass filter.

Abstract: A level of a base band signal at an input side of a variable gain amplification circuit is detected by a logarithmic amplifier having a wide input voltage range at a start of an operation, a control unit then performs a coarse feedforward control on a gain of the variable gain amplifier based on the detected level and finds a level of an output of an A/D converter by a mean square deriving circuit and inputs the resulting signal to the control unit. Then the control unit performs a fine feedback control on the variable gain amplifier based on the detected level.

Abstract: A level of a base band signal at an input side of a variable gain amplification circuit is detected by a logarithmic amplifier having a wide input voltage range at a start of an operation, a control unit then performs a coarse feedforward control on a gain of the variable gain amplifier based on the detected level and finds a level of an output of an A/D converter by a mean square deriving circuit and inputs the resulting signal to the control unit. Then the control unit performs a fine feedback control on the variable gain amplifier based on the detected level.

Abstract: In the portable telephone of the present invention, a transmission power upper limit value (STEPLIM in accordance with temperature (T) is found (S1, S2), whether the transmission power set value (STEPn) of the next slot exceeds the upper limit (STEPLIM) or not is determined (S3, S4), and when it does not exceed, a control signal value (Vc) in accordance with the transmission power set value (STEPn) is applied to a variable gain block (11, 13) (S5, S7). When it exceeds the upper limit, a control signal value (Vc) in accordance with the transmission power upper limit value (STEPLIM) is applied to the variable gain block (11, 13) (S6, S7).

Abstract: In a cellular telephone having a receiving circuit of a direct conversion type using an even harmonic orthogonal mixer, high-pass filters for removing a DC offset component are arranged before and after a variable gain amplifier in a base band circuit. The DC offset component occurred in the even harmonic orthogonal mixer is always constant, and the DC offset component occurred in the variable gain amplifier frequently varies so that a cutoff frequency of the front high-pass filter is set to be lower than a cutoff frequency of the rear high-pass filter, and the frequencies are set to achieve a fast transition response.

Abstract: At the onset of an operation, a level of a base band signal at an input side of a variable gain amplifying circuit is detected by a logarithmic amplifier having a wide dynamic range, and, a control unit controls a gain of a low-noise amplifier in a previous step of a low-pass filter based on the detected level and also controls a gain of variable gain amplifier, whereby saturation at an analog base band portion is prevented even when the level of the input signal is high.