Radio Frequency Filter

• US 20110140803A1
• Filed: 11/02/2010
• Published: 06/16/2011
• Est. Priority Date: 11/02/2009
• Status: Active Grant

• Current Assignee: KMW Incorporated
• Original Assignee: KMW Incorporated
• Inventors: PARK, Nam-Shin, KIM, Duk-Yong
• Granted Patent: US 8,749,321 B2
• Time in Patent Office: Days
• US Class Current: 333/110
• CPC Class Codes: H01P 1/20 Frequency-selective devices, e.g. filters
• CPC Class Codes: H01P 1/203 Strip line filters
• CPC Class Codes: H03H 11/36 Networks for connecting several sources or loads, working on the same frequency band, to a common load or source phase shifters providing two or more output signals H03H11/22
• CPC Class Codes: H03H 7/0138 Electrical filters or coupling circuits
• CPC Class Codes: H03H 7/46 Networks for connecting several sources or loads, working on different frequencies or frequency bands, to a common load or source for use in multiplex transmission systems H04J1/00
• CPC Class Codes: H03H 7/48 Networks for connecting several sources or loads, working on the same frequency or frequency band, to a common load or source phase shifters providing two or more output signals H03H7/21
• CPC Class Codes: H04B 1/58 Hybrid arrangements, i.e. arrangements for transition from single-path two-direction transmission to single-direction transmission on each of two paths or vice versa

Abstract

A Radio Frequency (RF) filter configured by combining a hybrid coupler with a general filter, for having different characteristics from original characteristics of a general filter is provided, in which a coupler receives an input signal through a first port, divides the input signal, outputs the divided signals through second and third ports, combines signals received through the second and third ports according to phases of the signals, and outputs the combined signal through the first port or as an output signal of the RF filter through a fourth port, and a first filter unit has a first port connected to the second port of the coupler and a second port connected to the third port of the coupler, for having a predetermined frequency filtering characteristic.

Claims

1. A Radio Frequency (RF) filter comprising:

a coupler for receiving an input signal through a first port, dividing the input signal, outputting the divided signals through second and third ports, combining signals received through the second and third ports according to phases of the signals, and outputting the combined signal through the first port or as an output signal of the RF filter through a fourth port; and

a first filter unit having a first port connected to the second port of the coupler and a second port connected to the third port of the coupler, for having a predetermined frequency filtering characteristic.

2. The RF filter of claim 1, wherein if the RF filter requires a Band Pass Filter (BPF) characteristic on the whole, the first filter unit includes a Band Rejection Filter (BRF), if the RF filter requires a BRF characteristic on the whole, the first filter unit includes a BPF, if the RF filter requires a High Pass Filter (HPF) characteristic on the whole, the first filter unit includes a Low Pass Filter (LPF), and if the RF filter requires an LPF characteristic on the whole, the first filter unit includes an HPF.

3. The RF filter of claim 1, further comprising first and second switch units for dynamically establishing a signal path according to an external switching control signal so that input and output ports of the RF filter are connected to the first filter unit directly or indirectly via the coupler, a signal passes only though the coupler, or a signal bypasses the first filter unit and the coupler.

4. The RF filter of claim 3, wherein each of the first and second switch units has a combination of single on/off switches or a combination of a Double Pole Double Throw (DPDT) switch and single on/off switches.

5. The RF filter of claim 1, further comprising a second filter unit connected to the fourth port of the coupler, for outputting an output signal of the RF filter.

6. The RF filter of claim 5, wherein each of the first and second filter units includes a BPF having a predetermined number of stages.

7. The RF filter of any of claim 1, wherein the coupler is a hybrid coupler.

8. The RF filter of any of claim 1, wherein the coupler is a magic T, further comprising a phase shifter provided on a path between the second port of the coupler and the first port of the first filter unit or between the third port of the coupler and the second port of the first filter unit, for shifting a phase of a passed signal by 90 degrees.

9. The RF filter of claim 1, wherein the first filter unit comprises:

a first filter having one end connected to the first port of the first filter unit and the other end that is opened;

a second filter having one end connected to the second port of the first filter unit; and

a phase shifter having one end connected to the other end of the second filter and the other end that is opened.

10. The RF filter of claim 9, wherein if the RF filter requires a BPF characteristic on the whole, the first and second filters of the first filter are BRFs, if the RF filter requires a BRF characteristic on the whole, the first and second filters of the first filter unit are BPFs, if the RF filter requires an HPF characteristic on the whole, the first and second filters of the first filter unit are LPFs, and if the RF filter requires an LPF characteristic on the whole, the first and second filters of the first filter unit are HPFs.

11. The RF filter of claim 9, further comprising first and second switch units for dynamically establishing a signal path according to an external switching control signal so that input and output ports of the RF filter are connected to the first filter unit directly or indirectly via the coupler, a signal passes only though the coupler, or a signal bypasses the first filter unit and the coupler.

12. The RF filter of claim 11, wherein each of the first and second switch units has a combination of single on/off switches or a combination of a Double Pole Double Throw (DPDT) switch and single on/off switches.

13. The RF filter of claim 9, further comprising a second filter unit connected to the fourth port of the coupler, for outputting an output signal of the RF filter.

14. The RF filter of claim 9, wherein the coupler is a hybrid coupler.

15. The RF filter of claim 9, wherein the coupler is a magic T, further comprising a phase shifter provided on a path between the second port of the coupler and the first port of the first filter unit or between the third port of the coupler and the second port of the first filter unit for shifting a phase of a passed signal by 90 degrees.