# US 2014/0197905 A1 · Low-loss tunable radio frequency filter

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- Number: US 2014/0197905 A1
- Document ID: US20140197905A1
- Status: Published application
- Kind: A1
- Application number: 14/214,249
- Filed: 2014-03-14
- Published: 2014-07-17
- Earliest claimed: 2006-11-17
- Assignees: Resonant Inc.
- Applicants: Resonant LLC
- Inventors: Genichi Tsuzuki; Balam A. Willemsen
- Web page: https://patentgrep.com/patent/US20140197905A1

## CPC

- H03H 9/465: {in combination with other electronic elements}
- G06F 30/30: Circuit design
- G06F 30/36: Circuit design at the analogue level
- G06F 30/367: Design verification, e.g. using simulation, simulation program with integrated circuit emphasis [SPICE], direct methods or relaxation methods
- G06F 30/392: Floor-planning or layout, e.g. partitioning or placement
- G06F 30/394: Routing (G06F30/396 takes precedence)
- H01P 1/20: Frequency-selective devices, e.g. filters
- H01P 1/20336: {Comb or interdigital filters}
- H03H 3/00: Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators
- H03H 7/0153: {Electrical filters; Controlling thereof}
- H03H 7/0161: {Bandpass filters (H03H7/12 takes precedence)}
- H03H 7/06: including resistors (H03H7/075, H03H7/09, H03H7/12, H03H7/13 take precedence)
- H03H 7/075: Ladder networks, e.g. electric wave filters
- H03H 7/12: Bandpass or bandstop filters with adjustable bandwidth and fixed centre frequency (H03H7/09 takes precedence)
- H03H 7/1791: {Combined LC in shunt or branch path}
- H03H 9/171: {implemented with thin-film techniques, i.e. of the film bulk acoustic resonator [FBAR] type}
- H03H 9/46: Filters (multiple-port electromechanical filters H03H9/70)
- H03H 9/462: {Microelectro-mechanical filters}
- H03H 9/542: {including passive elements (H03H9/545 takes precedence)}
- H03H 9/64: using surface acoustic waves
- H03H 9/6406: {Filters characterised by a particular frequency characteristic}
- G06F 2111/06: Multi-objective optimisation, e.g. Pareto optimisation using simulated annealing [SA], ant colony algorithms or genetic algorithms [GA]
- G06F 2111/10: Numerical modelling
- G06F 2111/20: Configuration CAD, e.g. designing by assembling or positioning modules selected from libraries of predesigned modules
- G06F 2119/10: Noise analysis or noise optimisation
- H03H 7/1758: {Series LC in shunt or branch path (H03H7/1791 takes precedence)}
- H03H 7/54: Modifications of networks to reduce influence of variations of temperature
- H03H 2007/013: {Notch or bandstop filters}
- H03H 2009/02204: {operating on an additional circuit element, e.g. applying a tuning DC voltage to a passive circuit element connected to the resonator}
- H03H 2210/012: Centre frequency; Cut-off frequency
- H03H 2210/025: Capacitor
- H03H 2210/033: Continuous
- Y10T 29/49018: with other electrical component
- H03H: IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS (waveguides, resonators, lines or other devices of the waveguide type H01P)
- G06F: ELECTRIC DIGITAL DATA PROCESSING (computer systems based on specific computational models G06N)
- H01P: WAVEGUIDES; RESONATORS, LINES, OR OTHER DEVICES OF THE WAVEGUIDE TYPE (operating at optical frequencies G02B)
- Y10T: TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION

## Abstract

An RF filter comprises a signal transmission path having an input and an output, a plurality of resonant elements disposed along the signal transmission path between the input and the output, and a plurality of non-resonant elements coupling the resonant elements together to form a stop band having a plurality of transmission zeroes corresponding to respective frequencies of the resonant elements, and at least one sub-band between the transmission zeroes. The non-resonant elements comprise at least one variable non-resonant element for selectively introducing at least one reflection zero within the stop band to create a pass band in a selected one of the sub-band(s). The RF filter further comprises an electrical controller configured for receiving an operating temperature, and adjusting the variable non-resonant element(s) based on the received operating temperature, thereby selectively moving the reflection zero(es) along the stop band to move the pass band within the selected sub-band.

## Claims

### Claim 1

A radio frequency (RF) filter, comprising:
a signal transmission path having an input and an output;
a plurality of resonant elements disposed along the signal transmission path between the input and the output;
a plurality of non-resonant elements coupling the resonant elements together to form a stop band having a plurality of transmission zeroes corresponding to respective frequencies of the resonant elements, and at least one sub-band between the transmission zeroes, wherein the non-resonant elements comprise at least one variable non-resonant element for selectively introducing at least one reflection zero within the stop band to create a pass band in a selected one of the at least one sub-bands; and
an electrical controller configured for receiving an operating temperature, and adjusting the at least one variable non-resonant element based on the received operating temperature, thereby selectively moving the at least one reflection zero along the stop band to move the pass band within the selected sub-band.

### Claim 2 (depends on 1)

The RF filter of claim 1, further comprising a temperature sensor configured for measuring the operating temperature, wherein the electrical controller is configured for receiving the measured operating temperature from the temperature sensor.

### Claim 3 (depends on 1)

The RF filter of claim 1, further comprising memory storing a look up table containing a plurality of reference operating temperatures and a plurality of sets of adjustment settings respectively corresponding to the different operating temperatures, wherein the electrical controller is configured for comparing the measured operating temperature to the plurality of reference operating temperatures in the look-up table, selecting the set of adjustment settings corresponding to the reference operating temperature closest to the measured operating temperature, and adjusting the at least one variable non-resonant element in accordance with the set of adjustment settings.

### Claim 4 (depends on 1)

The RF filter of claim 1, wherein the at least one variable non-resonant element is adjusted by adjusting a reactance of each of the at least one variable non-resonant element.

### Claim 5 (depends on 1)

The RF filter of claim 1, wherein the electrical controller is configured for adjusting the at least one variable non-resonant element to selectively introduce the at least one reflection zero within the stop band to create the pass band in the one sub-band.

### Claim 6 (depends on 5)

The RF filter of claim 5, wherein each of the at least one non-resonant element has a plurality of capacitors coupled in parallel to each other to form a capacitive circuit and at least one switch coupled to at least one of the capacitors, wherein the electrical controller is configured for varying the reactance of the respective non-resonant element by operating the at least one switch to selectively include or exclude at least one capacitor from the capacitive circuit to vary the capacitance of the capacitive circuit, thereby selectively moving the reflection zero within the stop band to move the pass band in the selected sub-band.

### Claim 7 (depends on 1)

The RF filter of claim 1, wherein the at least one sub-band comprises a plurality of sub-bands.

### Claim 8 (depends on 7)

The RF filter of claim 7, wherein the at least one variable non-resonant element is for displacing the at least one reflection zero along the stop band to create the pass band within selected ones of the sub-bands.

### Claim 9 (depends on 8)

The RF filter of claim 8, wherein the at least one variable non-resonant element is for displacing at least another reflection zero within the stop band to create another pass band within another one of the sub-bands.

### Claim 10 (depends on 7)

The RF filter of claim 7, wherein the pass band has substantially different bandwidths within the selected sub-bands.

### Claim 11 (depends on 1)

The RF filter of claim 1, wherein the at least one reflection zero comprises a plurality of reflection zeroes.

### Claim 12 (depends on 1)

The RF filter of claim 1, wherein the at least one variable non-resonant element comprises a plurality of variable non-resonant elements.

### Claim 13 (depends on 1)

The RF filter of claim 1, wherein the electrical controller is configured for adjusting the at least one variable non-resonant element, thereby selectively moving the at least one reflection zero along the stop band to return the pass band back to a nominal as-designed location within a frequency range.

### Claim 14 (depends on 13)

The RF filter of claim 13, wherein the electrical controller is configured for adjusting at least one of the resonant elements based on the received operating temperature, thereby selectively moving the transmission zero corresponding to each frequency of the at least one resonant element along the stop band to return the pass band back to the nominal as-designed location within the frequency range.

### Claim 15 (depends on 1)

The RF filter of claim 1, wherein the at least one variable non-resonant element has an adjustable reactance.

### Claim 16 (depends on 1)

The RF filter of claim 1, wherein the at least one variable non-resonant element comprises at least one of a variable capacitor, a loss-loss switch, a varactor, and a switched capacitor.

### Claim 17 (depends on 1)

The RF filter of claim 1, wherein each of the resonant elements comprises a thin-film lumped element structure.

### Claim 18 (depends on 17)

The RF filter of claim 17, wherein the thin-film lumped element structure comprises a high temperature superconductor (HTS).