ANTENNA MATCHING UNIT AND HIGH-FREQUENCY RECEIVING UNIT INCLUDING THE SAME
An antenna matching unit includes an antenna matching device to which a first high-frequency signal and a second high-frequency signal with a frequency higher than that of the first high-frequency signal are input; an active element to which an output signal from the antenna matching device is connected; and an output terminal to which an output from the active element is connected. The antenna matching device includes a signal line placed between the input and output; a series-connected element composed of a capacitor and inductor connected between the signal line and the ground; a capacitor connected in parallel with the inductor; and a control terminal for changing the capacitance value of the capacitor. The parallel resonance frequency between the inductor and capacitor is set to the frequency of the second high-frequency signal to reduce matching loss between the antenna and the tuner unit.
1 . An antenna matching unit receiving a first high-frequency signal having a first band width; and a second high-frequency signal with a frequency higher than that of the first high-frequency signal, having a second band width smaller than the first band width, by means of an antenna with a length of one-quarter or less a wavelength of the high-frequency signal, comprising:
an input terminal to which the high-frequency signal from the antenna is input;
an antenna matching device connected to the input terminal and minimizing matching loss;
an active element to which an output signal from the antenna matching device is connected and to which the high-frequency signal is input; and
an output terminal from which an output from the active element is connected,
wherein the antenna matching device includes:
a signal line placed between the input terminal and the output terminal;
a series-connected element including a first capacitor and a first inductor, both connected between the signal line and the ground;
a second capacitor connected in parallel with the first inductor; and
a control terminal for changing a capacitance value of the first capacitor, and
wherein a parallel resonance frequency between the first inductor and the second capacitor is set to a frequency of the second high-frequency signal, and a capacitance value of the first capacitor is changed to reduce matching loss in the first high-frequency signal.
2 . The antenna matching unit of claim 1 , wherein a capacitance value of the first capacitor can be continuously changed according to a control voltage from the control terminal.
3 . The antenna matching unit of claim 1 , further comprising a plurality of series-connected elements each including a capacitor and a switch, wherein a capacitance value of the first capacitor is selected by controlling the switch according to a control voltage from the control terminal.
4 . The antenna matching unit of claim 1 , wherein an optimum control voltage is preliminarily provided according to an arrangement mode of the antenna and a casing surrounding the antenna, and the antenna matching device is controlled according to the control voltage.
5 . The antenna matching unit of claim 1 , wherein an element for converting impedance is inserted serially to the signal line of the antenna matching device to minimize matching loss in the second high-frequency signal.
6 . The antenna matching unit of claim 1 ,
wherein the first high-frequency signal is a UHF TV broadcasting signal, and
wherein the second high-frequency signal is a GPS signal.
7 . A high-frequency receiving unit to which an input from the antenna matching unit of claim 1 is connected, comprising:
a distribution filter to which an output from the antenna matching unit is connected and that separates into the first high-frequency signal and the second high-frequency signal and outputs them,
wherein the antenna matching unit and the distribution filter are mounted on a same board, and
wherein at least one of the antenna matching device, the antenna matching unit, and the distribution filter is shielded.
8 . A high-frequency receiving unit to which an output from the antenna matching unit of claim 1 is connected, comprising:
a distribution filter separating into the first high-frequency signal and the second high-frequency signal and outputting them;
a first receiving circuit to which the first high-frequency signal output from the distribution filter is fed; and
a second receiving circuit to which the second high-frequency signal output from the distribution filter is fed.