Radio frequency filter

• US 8,749,321 B2
• Filed: 11/02/2010
• Issued: 06/10/2014
• Est. Priority Date: 11/02/2009
• Status: Active Grant

• Current Assignee: KMW Incorporated
• Original Assignee: KMW Incorporated
• Inventors: Kim, Duk-Yong, Park, Nam-Shin
• Primary Examiner(s): Lee, Benny
• Assistant Examiner(s): STEVENS, GERALD D
• Application Number:
  US12/917,917
• Publication Number:
  US 20110140803A1
• Time in Patent Office: 1,316 Days
• Field of Search: 333117-120, 333/123, 333/167, 333202-207
• US Class Current: 333/202
• 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 configured to receive an input signal through a first port of the coupler, to divide the input signal, to output divided signals through second and third ports of the coupler, to combine signals received through the second and third ports of the coupler according to phases of the signals, and to output the combined signal through the first port of the coupler or as an output signal of the RF filter through a fourth port of the coupler;

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

a second filter unit connected to the fourth port of the coupler for outputting the output signal of the RF filter;

wherein the first filter unit consists of one filter element, the first port of the first filter unit is an input port of the filter element and the second port of the first filter unit is an output port of the filter element, and the first and second filter units have different predetermined numbers of stages.

2. The RF filter of claim 1, wherein the filter element is one of a Band Rejection Filter (BRF), a Band Pass Filter (BPF), a Lower Pass Filter (LPF), and a High Pass Filter (HPF), wherein if the RF filter requires a BPF characteristic on the whole, the filter element is the BRF, if the RF filter requires a BRF characteristic on the whole, the filter element is the BPF, if the RF filter requires a HPF characteristic on the whole, the filter element is the LPF, and if the RF filter requires an LPF characteristic on the whole, the filter element is the HPF.

3. The RF filter of claim 1, wherein each of the first and second filter units includes a BPF.

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