Abstract: It is a theme of the present invention to provide a diversity receiving device capable of reducing a power consumption to the utmost extent while keeping a predetermined received quality without measurement of an electric field strength and a fading pitch. A decision about whether or not the diversity reception is executed is made by sensing a received quality. Also, a diversity gain is reduced by a predetermined value by controlling the diversity gain in the diversity reception, then a receiving operation of a predetermined branch or a branch whose received quality is low is stopped when the received quality at that time is in excess of a previously set value, and then a supply of power to all circuit or a partial circuit of the branch whose receiving operation is stopped is shut down. Accordingly, a power consumption can be reduced to the utmost extent while keeping a predetermined received quality.

Abstract: It is a theme of the present invention to provide a diversity receiving device and a receiving scheme switching method, capable of attaining a power saving by executing a switching between a diversity reception and a single reception with high accuracy.

Abstract: An object of the invention is to provide a diversity receiver and a reception system switching method capable of controlling diversity reception start and stop according to the switch condition responsive to person's liking and the use environment. An input section (109) allows the user to select and specify any of a diversity reception mode using two reception channels at all times, a single reception mode using a single reception channel at all times, or an automatic control reception mode for switching between the diversity reception and the single reception in response to the reception state of each mode, and a control section (107) determines a switching determination condition used in the automatic control reception mode according to mode selection information of other two modes.

Abstract: It is a theme of the present invention to provide a diversity receiving device and a diversity receiving method capable of making a diversity start not to cause receiving errors and also improving a sensitivity. There is a difference in a jamming wave level that is allowed to get the same received quality between the diversity reception and the single branch reception, so that a gain improving effect equivalent to a diversity gain is expected by the diversity reception in contrast to the single branch reception. Therefore, a dynamic range of the jamming wave from a transmitting portion (105) of a second radio system in a radio terminal is set smaller in expectation of the improving effect of such jamming wave resistance, and then a transmission control signal (S117) is acquired from a transmission signal controlling portion (106). Thus, the diversity reception is started before a start of transmission, and diversity control is applied adaptively without deterioration of the received quality.

Abstract: It is a theme of the present invention to provide a diversity receiving device capable of reducing a power consumption to the utmost extent while keeping a predetermined received quality without measurement of an electric field strength and a fading pitch. A decision about whether or not the diversity reception is executed is made by sensing a received quality. Also, a diversity gain is reduced by a predetermined value by controlling the diversity gain in the diversity reception, then a receiving operation of a predetermined branch or a branch whose received quality is low is stopped when the received quality at that time is in excess of a previously set value, and then a supply of power to all circuit or a partial circuit of the branch whose receiving operation is stopped is shut down. Accordingly, a power consumption can be reduced to the utmost extent while keeping a predetermined received quality.

Abstract: It is a theme of the present invention to provide a diversity receiving device and a receiving scheme switching method, capable of attaining a power saving by executing a switching between a diversity reception and a single reception with high accuracy.

Abstract: A subject of the present invention is to provide a receiver and a communication terminal that are adapted appropriately for a plurality of communication systems.

Abstract: A direct conversion receiver includes a local oscillator for generating a first local oscillator signal having a variable frequency. A 90° phase shifter operates for shifting a phase of the first local oscillator signal by 90° to convert the first local oscillator signal into a second local oscillator signal. A first mixer operates for mixing a received RF signal and the first local oscillator signal. A second mixer operates for mixing the received RF signal and the second local oscillator signal. A first low pass filter processes an output signal of the first mixer. The first low pass filter has a controllable cutoff frequency. A second low pass filter processes an output signal of the second mixer. The second low pass filter has a controllable cutoff frequency. A demodulator recovers an information signal represented by the received RF signal from output signals of the first and second low pass filters.

Abstract: A direct conversion receiver includes a local oscillator for generating a first local oscillator signal having a variable frequency. A 90° phase shifter operates for shifting a phase of the first local oscillator signal by 90° to convert the first local oscillator signal into a second local oscillator signal. A first mixer operates for mixing a received RF signal and the first local oscillator signal. A second mixer operates for mixing the received RF signal and the second local oscillator signal. A first low pass filter processes an output signal of the first mixer. The first low pass filter has a controllable cutoff frequency. A second low pass filter processes an output signal of the second mixer. The second low pass filter has a controllable cutoff frequency. A demodulator recovers an information signal represented by the received RF signal from output signals of the first and second low pass filters.

Abstract: A direct conversion receiver includes a local oscillator for generating a first local oscillator signal having a variable frequency. A 90° phase shifter operates for shifting a phase of the first local oscillator signal by 90° to convert the first local oscillator signal into a second local oscillator signal. A first mixer operates for mixing a received RF signal and the first local oscillator signal. A second mixer operates for mixing the received RF signal and the second local oscillator signal. A first low pass filter processes an output signal of the first mixer. The first low pass filter has a controllable cutoff frequency. A second low pass filter processes an output signal of the second mixer. The second low pass filter has a controllable cutoff frequency. A demodulator recovers an information signal represented by the received RF signal from output signals of the first and second low pass filters.

Abstract: A direct conversion receiver has: an I-low-pass filter 9 which has cut-off frequency switching device, switches over the cut-off frequency in accordance with the transmission rate, and eliminates high-frequency components from a modulated signal mixed with a first local signal; a Q-low-pass filter 10 which eliminates high-frequency components from a modulated signal mixed with the first local signal phase-shifted by 90 degrees; transmission rate detecting device 13 for detecting transmission rate information from transmission data detected by transmission data detecting device 12; and I- and Q-low-pass filter cut-off frequency controlling device 15 and 16 for generating I- and Q-control signals which control the cut-off frequency switching device, from the detected transmission rate. The cut-off frequencies of the low-pass filters are switched over in accordance with the transmission rate of reception.

Abstract: In a receiver for effecting an intermittent reception operation, a reception unit including an antenna, a radio frequency amplifier, a local oscillator and a mixer, a received signal processing circuit for starting signal processing of a received signal from the reception unit after the passage of a predetermined time, a reception field level detection unit for detecting the level of the received signal and an automatic gain control unit for controlling the level of the received signal within the predetermined time and holding the controlled level after the passage of the predetermined time, are disposed in a plurality of stages.

Abstract: An apparatus using a battery as a power source requires a battery having an extended life time. A burden upon a battery can be reduced by operating the inner circuit at a low voltage and current. The present invention aims at providing a compact and low power consuming apparatus. A battery used as a power source drives a circuit for a low voltage circuit system and a switching circuit which switches power supply when the battery voltage becomes a preset voltage. A circuit for a high voltage circuit is directly driven by the battery when the battery voltage is high, and the circuit is powered from the output (for example, 1.5 volts) of a step-up circuit when the battery voltage is low. Switching of power sources is made in such a manner, resulting in low power consumption. Extension of life time of battery, and reduction in size of battery and apparatus can be achieved.

Abstract: A direct conversion receiver for providing a direct conversion of a radio frequency signal having a carrier frequency comprises a local oscillator for substantially equal frequency to the carrier, and a semiconductor integrated circuit mounting mixers and amplifiers for amplifying inputs to the mixer. The amplifiers amplify the local oscillation signals and/or radio frequency signal inputted from the outside of the semiconductor integrated circuit and supply the amplified signals to the mixers. The mixers mix these inputted signals and output the mixed signals to the outside of the semiconductor integrated circuit. By thus forming the receiver, radiation of the local oscillation signals to outside of the receiver and leakage inside thereof can be suppressed.

Abstract: A data receiving system comprising an I base-band signal and a Q base-band signal which are used in a quadrature demodulation operation. Zero-crossing points of respective base-band signals are detected and a control signal is generated in response to each zero-crossing point. A phase-shift switching circuit alternately selects either the I base-band signal or the Q base-band signal in response to the control signal to generate an I/Q base-band signal. And, a demodulation operation is executed on the basis of the I/Q signal.

Abstract: The center frequency of each of the analog filters with different selectivities each other installed in an automatic adjusting circuit is automatically adjusted in accordance with a bias input signal which is generated by the phases detectors respectively associated with the analog filters in accordance with a frequency difference, so as to be equal to the reference frequency of an input signal applied to the two analog filters. The bias input signal is fed to an analog filter to be controlled, which is formed on the same chip as that of the above two filters. A coarse adjustment is based on the output signal of the phase detector associated with the analog filter with a low selectivity. A fine adjustment is based on the output signal of the phase detector associated with the analog filter with a high selectivity.