Antenna switching circuit and communication system using the same
First Claim
1. A communication system comprising:
- an antenna;
a reception circuit receiving a signal received at the antenna;
a transmission circuit sending a transmission signal to be transmitted to the antenna;
a switch circuit provided between the antenna and the transmission circuit; and
a filter circuit provided between the switch circuit and the transmission circuit;
wherein the filter circuit reflects a signal component having a predetermined high frequency band in the transmission signal toward the switch circuit.
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Accused Products
Abstract
An antenna switching circuit and communication system capable of reducing a high-order harmonic component radiated from the antenna used for transmission and reception. A fundamental wave passes through a signal transmission line between an antenna switch and a transmitting circuit, a filter circuit is connected for reflecting the high-order harmonic component, the high-order harmonic component generated due to linear distortion of the antenna switch is propagated toward the antenna and the transmitting circuit, the high-order harmonic component is reflected at a node of the filter circuit, and the reflected signal is propagated toward the antenna through the antenna switch. By suitably controlling a reflection characteristic of the filter circuit and a line of the signal transmission line, the high-order harmonic components on the transmission line are cancelled out and the high-order harmonic component from the antenna can be decreased.
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Citations
16 Claims
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1. A communication system comprising:
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an antenna;
a reception circuit receiving a signal received at the antenna;
a transmission circuit sending a transmission signal to be transmitted to the antenna;
a switch circuit provided between the antenna and the transmission circuit; and
a filter circuit provided between the switch circuit and the transmission circuit;
wherein the filter circuit reflects a signal component having a predetermined high frequency band in the transmission signal toward the switch circuit. - View Dependent Claims (2, 3, 4)
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5. A communication system comprising:
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an antenna;
a reception circuit receiving a signal received at the antenna;
a transmission circuit sending a transmission signal to be transmitted to the antenna;
a switch circuit provided between the antenna and the transmission circuit;
a filter circuit provided among the switch circuit, the transmission circuit and the reception circuit, said filter circuit passing a fundamental wave component in the transmission signal and reflecting a signal component having a predetermined high frequency band in the transmission signal toward said switch circuit. - View Dependent Claims (6, 7, 8)
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9. An antenna switching circuit for enabling a transmitting circuit and a receiving circuit to share a single antenna and for switching the antenna to the transmitting circuit at the time of transmission or the receiving circuit at the time of transmission or reception, comprising:
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an antenna switch connecting the antenna to the transmitting circuit at the time of transmission and connecting the antenna to the receiving circuit at the time of reception, and a filter circuit which is connected to at least a signal transmission line between the antenna switch and the transmitting circuit and reflects back a signal of a predetermined high frequency band propagated through the signal transmission line toward said antenna switch. - View Dependent Claims (10)
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11. A communication system for transmission and reception sharing a single antenna, comprising:
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a transmitting circuit for transmitting a high frequency signal by using the antenna;
a receiving circuit for receiving a radio signal by the antenna;
an antenna switch for connecting the antenna to the transmitting circuit at the time of transmission and the antenna to the receiving circuit at the time of reception; and
a filter circuit which is connected to at least a signal transmission line between the antenna switch and the transmission circuit and reflects back a signal of a predetermined high frequency band propagated through the signal transmission line;
wherein a high-order harmonic component generated in the antenna switch corresponding to a transmission signal output by the transmitting circuit is propagated toward both the antenna and the transmitting circuit, and wherein the filter circuit reflects back the high-order harmonic component propagated toward the transmitting circuit and causes the reflected signal to be propagated toward the antenna through the antenna switch. - View Dependent Claims (12, 13, 14, 15, 16)
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Specification