IP Library › Granted Patent US 8,063,718
Granted Patent B2
US 8,063,718 · App. 12/686,303 · Granted Nov 22, 2011

Duplexer, communication module, and communication device

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Quick Facts
Patent No.
US 8,063,718
App. No.
12/686,303
Filed
Jan 12, 2010
Granted
Nov 22, 2011
Kind
B2
Art Unit
2817
USPC
333/133
Abstract

A duplexer of the present invention includes a reception filter ( 3 ) for passing signals in a predetermined frequency band and attenuates signals in the other frequency bands among reception signals input to an antenna port, and a transmission filter ( 4 ) for passing signals in a predetermined frequency band and attenuates signals in the other frequency bands among transmission signals input from the outside and outputting them to the antenna port. The duplexer further includes a conversion circuit ( 22 ) provided with a single-ended input terminal connected to the antenna port and balanced output terminals. The reception filter ( 3 ) is provided with a balanced input terminal connected to the output terminal of the conversion circuit ( 22 ) and a balanced output terminal for outputting the filtered reception signal. Thus, a balance-output-type duplexer that is connectable to a balance-input-type LNA and is free from loss and degradation in power-handling capability, a communication module and a communication device can be realized.

Claims (23)

1. A duplexer, comprising:

a single antenna port;

a reception filter that passes a signal in a reception frequency band and attenuates a signal in a transmission frequency band among signals input to the antenna port; and

a transmission filter that passes a signal in a transmission frequency band and attenuates a signal in a reception frequency band among signals input from an outside and outputs the filtered signal to the antenna port,

the duplexer further comprising a first conversion circuit provided with a single input terminal connected to the antenna port and balanced output terminals,

wherein the reception filter includes balanced input terminals connected to the balanced output terminals of the first conversion circuit and balanced output terminals for outputting filtered reception signals, and

the first conversion circuit is formed of lumped constant elements and has a function of performing phase matching between the reception filter and the transmission filter.

2. A communication module, comprising the duplexer according to claim 1 .

3. A communication device, comprising the communication module according to claim 2 .

4. The duplexer according to claim 1 , wherein the reception filter is formed of a double-mode surface acoustic wave filter.

5. The duplexer according to claim 1 , wherein at least a part of the reception filter is formed of a balanced ladder filter.

6. The duplexer according to claim 1 , wherein the reception filter is formed of two single-ended ladder filters.

7. The duplexer according to claim 1 , wherein at least a part of the reception filter is formed of a balanced lattice filter.

8. The duplexer according to claim 1 , wherein the transmission filter is formed of a single-ended filter.

9. The duplexer according to claim 1 ,

wherein the transmission filter is formed of a balanced filter, and the duplexer further comprises a second conversion circuit,

wherein the second conversion circuit includes balanced input terminals connected to the transmission filter and a single output terminal connected to the antenna port, and converts balanced signals input to the balanced input terminals into a single signal.

10. The duplexer according to claim 9 , wherein the transmission filter is formed of a balanced ladder filter or two single-ended ladder filters.

11. The duplexer according to claim 9 , wherein the transmission filter is formed of a double-mode surface acoustic wave filter.

12. The duplexer according to claim 1 , wherein the first conversion circuit with the phase matching function is formed on a same substrate.

13. The duplexer according to claim 1 , wherein each of the first conversion circuit with the phase matching function is formed partially or entirely on a substrate of a transmission filter element or a reception filter element.

14. The duplexer according to claim 1 , wherein the reception filter or the transmission filter includes a plurality of filter elements, and

the filter elements are composed of any one of a surface acoustic wave filter, a boundary wave filter, or a film bulk acoustic resonator filter.