Integrated filter balun

• US 6,542,055 B1
• Filed: 10/31/2000
• Issued: 04/01/2003
• Est. Priority Date: 10/31/2000
• Status: Expired due to Term

• Current Assignee: Avago Technologies International Sales Pte Limited (Broadcom, Inc.)
• Original Assignee: Agilent Technologies, Inc.
• Inventors: Larson, John D III, Frank, Michael L.
• Primary Examiner(s): Pascal, Robert
• Assistant Examiner(s): TAKAOKA, DEAN O
• Application Number:
  US09/704,201
• Time in Patent Office: 882 Days
• Field of Search: 333/187, 333/189, 333/190, 310/320
• US Class Current: 333/189
• CPC Class Codes: H03H 9/0095 using bulk acoustic wave devices

Abstract

In one embodiment, an N-stage ladder circuit is serially connected to a bridge (lattice circuit. The N-stage ladder circuit receives differential inputs, e.g. mixers, while the bridge lattice circuit outputs a singled end output, e.g. amplifier. In another embodiment, a bridge lattice circuit is serially connected to an N-stage ladder circuit. The bridge lattice circuit receives a single ended load while the N-stage ladder circuit provides a differential output. Film bulk acoustic resonators are used in the combination ladder and lattice structure for both embodiments to provide the necessary band-pass functionality as well as make the necessary transition from differential to single ended load.

Claims

1. A circuit comprising:

a N-stage differential ladder filter having at least two inputs and an output, and

a bridge circuit, receiving the output of the N-stage differential ladder filter, having an output a bridge lattice circuit serially coupled to the differential ladder filter, comprising a plurality of resonators serially coupled together in a ring configuration at resonant frequencies alternating between a first and a second resonant frequency;

wherein the N-stage differential ladder filter and the bridge circuit include film bulk acoustic resonators.

2. A circuit of claim 1, wherein a first stage of the differential ladder filter includes a first resonator at a first resonant frequency, the first resonator coupled between the at least two inputs.

3. A circuit of claim 2, wherein the first stage further comprises a second and a third resonator each at a second resonant frequency, the second resonator coupled to a first one of the at least two inputs and coupled in parallel with the first resonator, the third resonator coupled to a second one of the at least two inputs and coupled in parallel with the fist resonator.

4. A circuit of claim 3, wherein subsequent stages of the differential ladder filter are configured substantially the same as the first stage.

5. A filter comprising:

a differential ladder filter having a plurality of stages and having two inputs and two outputs, each stage including two rail sections and one rung section, each rail section including a resonator at a first resonant frequency, each rung section including a resonator at a second resonant frequency; and

a bridge lattice circuit serially coupled to the differential ladder filter, the bridge lattice circuit comprising a plurality of resonators serially coupled together in a ring configuration at resonant frequencies alternating between the first and the second resonant frequency.

6. The filter of claim 5, wherein the resonators in the differential ladder filter and the bridge lattice circuit are film bulk acoustic resonators.