Abstract: A tuner includes an input terminal operable to receive a high-frequency signal including a first high-frequency signal and a second high-frequency signal. The second high-frequency signal has a level larger than that of the first signal. The tuner further includes a first filter having an input port coupled to the input terminal for allowing a signal having the first frequency to pass therethrough and for attenuating a signal having the second frequency, a high-frequency amplifier coupled to an output port of the first filter, a second filter having an input port coupled to an output of the high-frequency amplifier for allowing a signal having the first frequency to pass therethrough and for attenuating the signal having the second frequency, a local oscillator, and a mixer for mixing the output of the high-frequency amplifier with an output of the local oscillator.

Abstract: A digital signal transceiver includes a frequency modulator for outputting a high-frequency signal frequency-modulated with a digital signal input thereto, a power amplifier, an antenna terminal, and an antenna switch. The antenna switch includes a first branch port for receiving a signal output from the power amplifier, a common port connected to the antenna terminal, said common port being connected to the first branch port in the transmitting mode, and a second branch port connected to the common port in the receiving mode. The transceiver further includes a filter having an input port thereof connected to the second branch port of the antenna switch, a high-frequency amplifier having an input port thereof connected to an output port of the filter, and a mixer for mixing a signal output from the high-frequency amplifier with the signal output from the frequency modulator.

Abstract: A mobile device has a TV function that displays radio wave receiving quality information and allows an available channel to be easily selected. The mobile device has an antenna, a tuner unit connected to the antenna, a baseband processing unit connected to an output unit of the tuner unit, a display unit to which an output of the baseband processing unit is supplied, and a control unit connected to them. The mobile device supplies station selection data from the control unit sequentially scans TV broadcast waves with tuner the unit, acquires information of radio wave receiving quality of each of TV broadcast waves received at that time, and arranges and displays a plurality of pieces of information of the radio wave receiving quality on the display unit. Thus, search for an available channel is not required.

Abstract: A digital signal transceiver includes a frequency modulator for outputting a high-frequency signal frequency-modulated with a digital signal input thereto, a power amplifier, an antenna terminal, and an antenna switch. The antenna switch includes a first branch port for receiving a signal output from the power amplifier, a common port connected to the antenna terminal, said common port being connected to the first branch port in the transmitting mode, and a second branch port connected to the common port in the receiving mode. The transceiver further includes a filter having an input port thereof connected to the second branch port of the antenna switch, a high-frequency amplifier having an input port thereof connected to an output port of the filter, and a mixer for mixing a signal output from the high-frequency amplifier with the signal output from the frequency modulator.