Abstract: A PLL circuit (11) is provided with an oscillator for reception at a frequency band (A), and an oscillator for reception at a frequency band (B). A PLL circuit (12) is provided with an oscillator for reception at the frequency band (B), and an oscillator for reception at the frequency band (A). In the case of searching at the frequency band (A), the PLL circuit (11) and the PLL circuit (12) are oscillated at different frequencies within the frequency band (A) at the same time. After locking the PLL circuit (11), output from the PLL circuit (11) is inputted to a mixer (15) and an intensity of a receiving signal is measured, then, a signal to be inputted to the mixer (15) is switched to an output from the PLL circuit (12) and an intensity of a receiving signal is measured.

Abstract: An apparatus for switching a matching circuit in a mobile communication terminal includes a PIN diode connected in parallel to an RF signal input and output line to be turned on and off to connect and disconnect an impedance matching-element to the RF signal input and output line in accordance with a frequency band switching-signal, and a bias circuit for generating a bias voltage applied to the PIN diode in accordance with the frequency band switching-signal, thereby shifting an amplitude of an RF signal to a positive side at an off-time of the PIN diode.

Abstract: An apparatus for switching a matching circuit in a mobile communication terminal includes a PIN diode connected in parallel to an RF signal input and output line to be turned on and off to connect and disconnect an impedance matching-element to the RF signal input and output line in accordance with a frequency band switching-signal, and a bias circuit for generating a bias voltage applied to the PIN diode in accordance with the frequency band switching-signal, thereby shifting an amplitude of an RF signal to a positive side at an off-time of the PIN diode.

Abstract: A phase noise reduction system of a frequency synthesizer for obtaining an arbitrary frequency oscillation by locking a reference oscillation frequency of a reference oscillator to an oscillation frequency of a voltage controlled oscillator has a variable frequency divider for voltage controlled oscillator which divides an oscillation frequency of the voltage controlled oscillator, a variable frequency divider for reference oscillator which divides a reference oscillation frequency of the reference oscillator, and a lock detection section which initially sets a common small number of frequency division to the variable frequency divider for voltage controlled oscillator and the variable frequency divider for reference oscillator, respectively, subsequently detects locking of frequency, and switches the setting of number of frequency division from the small number of frequency division to a larger number of frequency division.

Abstract: An object of the present invention is to allow the miniaturization of a mobile communication equipment and the reduction of consumption power, and to improve the electrical characteristics of a final stage amplifier. An inputted RF signal is amplified to a specified transmission output by a final stage amplifier, the output power and a reflected wave generated by mismatching between an output impedance of the final stage amplifier and a load impedance connected to an output side of the final stage amplifier are detected by a directional coupler. Two switches are selectively switched in a time division manner, a DC voltage corresponding to the reflected wave is selected, a comparator compares a threshold voltage with the DC voltage, a switch is switched by an output of the comparator outputted in accordance with the comparison, and gate voltages are selectively applied to the final stage amplifier.

Abstract: An object of the present invention is to allow the miniaturization of a mobile communication equipment and the reduction of consumption power, and to improve the electrical characteristics of a final stage amplifier. An inputted RF signal is amplified to a specified transmission output by a final stage amplifier, the output power and a reflected wave generated by mismatching between an output impedance of the final stage amplifier and a load impedance connected to an output side of the final stage amplifier are detected by a directional coupler. Two switches are selectively switched in a time division manner, a DC voltage corresponding to the reflected wave is selected, a comparator compares a threshold voltage with the DC voltage, a switch is switched by an output of the comparator outputted in accordance with the comparison, and gate voltages are selectively applied to the final stage amplifier.

Abstract: A transmission power control circuit includes a plurality of antennas, a plurality of reference voltages provided for the plurality of antennas, respectively, and an amplifier section for amplifying a transmission signal to produce a transmission output signal. A first switch selects one of the plurality of antennas in response to a switch control signal such that the transmission output signal is outputted from the selected antenna. A detecting unit detects a detection voltage for the transmission output signal. A second switch selects one of the plurality of reference voltages in response to the switch control signal. An error correction circuit controls the amplifier section based on the detection voltage and the selected reference voltage such that the transmission output signal has a predetermined power level.

Abstract: In a portable electronic equipment usable with both primary and secondary batteries, discrimination between primary and secondary batteries is carried out utilizing a difference in discharge characteristics between the primary and secondary batteries. Specifically, a previously acquired battery voltage is compared with a battery voltage after a given period of time, and whether the battery is a primary battery or a secondary battery is determined based on the voltage difference. Charging operation is controlled based on the discrimination results, enabling the secondary battery to be more surely charged.

Abstract: An electrical charging device for preventing an erroneous electrical charging of a non-rechargeable battery includes a battery cell voltage sensing circuit and a switch control circuit for controlling an electrical charging in response to a presence or a non-presence of a battery cell voltage detected by this circuit. When a battery case houses one type of primary batteries, the switch control circuit prevents electrical charging when the voltage is detected, but permits electrical charging when the voltage is not detected. For another type of primary battery, the switch control circuit prevents electrical charging when the voltage is detected and it prevents electrical charging when the voltage is not detected.

Abstract: A transmission level control circuit includes a negative feedback control loop and a level setting controller. A first amplifier amplifies an input signal by a variable amplification factor to produce a first signal. A second amplifier receives the first signal and produces a second signal according to a control signal such that the first signal is amplified when the control signal is in a first state and the first signal is attenuated when the control signal is in a second state. An output signal produced by a third amplifier amplifying the second signal is monitored by a detector which detects an output level of the output signal. A controller performs the negative feedback control when the control signal is in the first state, and performs the level setting control such that the variable amplification factor is set so as to set the output level at a relatively lower level when the control signal is in the second state.