# US 2021/0344319 A1 · Interdigitated rf filter

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- Number: US 2021/0344319 A1
- Document ID: US20210344319A1
- Status: Published application
- Kind: A1
- Application number: 16/863,083
- Filed: 2020-04-30
- Published: 2021-11-04
- Earliest claimed: 2020-04-30
- Assignees: pSemi Corporation
- Applicants: pSemi Corporation
- Inventors: Michael P. GAYNOR
- Web page: https://patentgrep.com/patent/US20210344319A1

## CPC

- H03H 7/0161: {Bandpass filters (H03H7/12 takes precedence)}
- H10W 44/20: at high-frequency [HF] or radio frequency [RF]
- H03H 7/17: {Structural details of sub-circuits of frequency selective networks}
- H03H 9/02228: {Guided bulk acoustic wave devices or Lamb wave devices having interdigital transducers situated in parallel planes on either side of a piezoelectric layer}
- H10W 44/501: {Inductive arrangements (H10W44/20 takes precedence)}
- H10W 44/601: {Capacitive arrangements (H10W44/20 takes precedence)}
- H01G 4/012: Form of non-self-supporting electrodes
- H01G 4/33: Thin- or thick-film capacitors {(thin- or thick-film circuits; capacitors without a potential-jump or surface barrier specially adapted for integrated circuits, details thereof, multistep manufacturing processes therefor)}
- H03H 2001/0014: {Capacitor filters, i.e. capacitors whose parasitic inductance is of relevance to consider it as filter}
- H03H 2001/0085: {Multilayer, e.g. LTCC, HTCC, green sheets}
- H10D 1/714: {having horizontal extensions}
- H03H: IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS (waveguides, resonators, lines or other devices of the waveguide type H01P)
- H10W: GENERIC PACKAGES, INTERCONNECTIONS, CONNECTORS OR OTHER CONSTRUCTIONAL DETAILS OF DEVICES COVERED BY CLASS H10
- H01G: CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE (selection of specified materials as dielectric H01B3/00; capacitors having potential barriers H10D1/62, H10K10/10)
- H10D: INORGANIC ELECTRIC SEMICONDUCTOR DEVICES

## Abstract

An interdigitated RF filter. The interdigitated RF filter includes input fingers connected to an input node and output fingers connected to an output node where at least one input finger is connected the output node or at least one output finger is connected to the input node. The described interdigitated RF filter can be implemented in various configurations such as series, shunt, ladder or a combination thereof.

## Claims

### Claim 1

A radio frequency (RF) interdigitated filter comprising:
a plurality of input fingers connected to an input node;
a plurality of output fingers connected to an output node, and
input connections between at least two of the input fingers, and output connections between at least two of the output fingers;
wherein at least one output finger is connected to the input node, and/or at least one input finger is connected to the output node, and wherein the plurality of input fingers and the plurality of output fingers are made from a first metal layer, and the input connections and the output connections are made from a second metal layer.

### Claim 2 (depends on 1)

The RF interdigitated filter of claim 1, wherein the plurality of input fingers and the plurality of output fingers are made from a first metal layer.

### Claim 3 (depends on 1)

The RF interdigitated filter of claim 1, wherein the at least one output finger and the at least one input finger are respectively a bottom output finger and a bottom input finger or a top output finger and a top input finger.

### Claim at position 4

4-5. (canceled)

### Claim 6 (depends on 1)

The RF interdigitated filter of claim 1, wherein a spacing of at least a pair of adjacent input and output fingers is different from a spacing of the other pairs of adjacent input and output fingers.

### Claim 7 (depends on 1)

The RF interdigitated filter of claim 1, wherein all pairs of adjacent input and output fingers have a same spacing.

### Claim 8 (depends on 1)

The RF interdigitated filter of claim 1, wherein each pair of adjacent input and output fingers has a spacing that is different from a spacing of any one of other adjacent input and output fingers.

### Claim 9 (depends on 1)

The RF interdigitated filter of claim 1, wherein proceeding from an end or two ends of the RF interdigitated filter to a middle of the RF interdigitated filter, spacings of consecutive pairs of adjacent input and output fingers follow a non-increasing or a non-decreasing function.

### Claim 10

A radio frequency (RF) interdigitated filter comprising:
a plurality of input fingers connected to an input node; and
a plurality of output fingers connected to an output node,
wherein at least one output finger is connected to the input node, and/or at least one input finger is connected to the output node, the RF interdigitated filter being implemented in a shunt configuration wherein either the input node or output node is connected to ground.

### Claim 11 (depends on 1)

An RF circuit comprising two or more of the RF interdigitated filters of claim 1 implemented in a multi-resonator filter structure with a) series resonators, b) parallel resonators, c) ladder configuration of resonators or a combination thereof.

### Claim 12 (depends on 1)

The RF interdigitated filter of claim 1 implemented as part of an RF circuit with other passive components.

### Claim 13

A radio frequency (RF) interdigitated filter comprising:
a plurality of input fingers connected to an input node; and
a plurality of output fingers connected to an output node,
wherein at least one output finger is connected to the input node, and/or at least one input finger is connected to the output node, the RF interdigitated filter being implemented as part of a digitally tunable capacitor (DTC) or digitally tunable inductor (DTL).

### Claim 14 (depends on 1)

The RF interdigitated filter of claim 1 implemented as part of one of a i) low pass, ii) band pass, or c) high pass filter.

### Claim 15 (depends on 1)

The RF interdigitated filter of claim 1 implemented in a balanced configuration.

### Claim 16 (depends on 1)

The RF interdigitated filter of claim 1, wherein a finger of the plurality of input fingers or the plurality of output fingers has a length different from lengths of other fingers of the plurality of input fingers and the plurality of output fingers.

### Claim 17 (depends on 16)

The RF interdigitated filter of claim 16 having a rectangular cross section.

### Claim 18 (depends on 16)

The RF interdigitated filter of claim 16, having a non-rectangular cross section.

### Claim 19 (depends on 18)

The RF interdigitated filter of claim 18, wherein the non-rectangular cross section has a shape bulging in a middle or on a side of the non-rectangular cross section.

### Claim 20

A method of filtering a signal comprising:
providing, between an input node and an output node, an electronic structure by interleaving a plurality of input fingers connected to the input node with a plurality of output fingers connected with the output node;
connecting at least one output finger to the input node or at least one input finger the output node;
applying the signal at the input node, thereby filtering the signal to generate a filtered signal at the output node; and
connecting two or more of the input fingers together and connecting two or more of the output fingers together,
wherein the plurality of input fingers and the plurality of output fingers are made from a first metal layer, and the connecting of the two or more input fingers together and the connecting of the two or more output fingers together are performed using a second metal layer.

### Claim 21

(canceled)

### Claim 22 (depends on 20)

The method of claim 20, wherein the at least one output finger and the at least one input finger are respectively a bottom output finger and a bottom input finger or a top output finger and a top input finger.

### Claim at position 22

23-24. (canceled)

### Claim 25 (depends on 20)

The method of claim 20, wherein the filtering is one of a) low-pass b) band-pass, or c) high-pass filtering.

### Claim 26

A radio frequency (RF) interdigitated filter implemented in an integrated circuit including a silicon substrate, the RF interdigitated filter comprising:
a plurality of input fingers connected to an input node; and
a plurality of output fingers connected to an output node,
wherein the plurality of input fingers and the plurality of output fingers are made from one or more metal layers of the integrated circuit on the silicon substrate; and
wherein at least one output finger is connected to the input node, and/or at least one input finger is connected to the output node.

### Claim 27 (depends on 26)

The RF interdigitated filter implemented in an integrated circuit of claim 26, wherein the integrated circuit is a monolithic integrated circuit.