Tunable bandpass filter

Patent metadata

Field	Value
Publication number	US-2018205367-A1
Application number	US-201715406338-A
Country	US
Kind code	A1
Filing date	Jan 13, 2017
Priority date	Jan 13, 2017
Publication date	Jul 19, 2018
Grant date	—

Abstract

A single-chip tunable bandpass filter is provided having a bandpass filter circuit with all tuning components for the bandpass filter circuit formed on the single-chip to provide a programmed center frequency for the tunable bandpass filter. The bandpass filter circuit may include, but is not limited to, a plurality of serially coupled singe stage biquad filter circuits coupled to an input formed on the single-chip and configured to provide a bandpass filtered output signal to an output formed on the single-chip. The bandpass filtered output may be provided by an output buffer formed on the single-chip. The single-chip includes at least one tuning input to receive data for tuning stored in a data register formed on the single-chip. The data register provides control bits to the tuning components that include a programmable resistor responsive to the control bits to vary the programmable resistor to adjust programmed center frequency.

First claim

What is claimed is:

1 . A single-chip tunable bandpass filter, comprising:
a bandpass filter circuit formed on the single-chip, the bandpass filter circuit coupled to an input formed on the single-chip and configured to provide a bandpass filtered output signal to an output formed on the single-chip; all tuning components for the bandpass filter circuit formed on the single-chip; and at least one tuning input formed on the single-chip and coupled to the all tuning components for tuning the bandpass filter circuit to a programmed center frequency; wherein, no tuning components are external to the single-chip for tuning the bandpass filter circuit to the programmed center frequency.

2 . The single-chip tunable bandpass filter of claim 1 , wherein the bandpass filter circuit comprises a biquad bandpass filter circuit formed on the single-chip via a biCMOS process.

3 . The single-chip tunable bandpass filter of claim 1 , further comprising an output buffer between the tunable bandpass filter circuit and the output formed on the single-chip.

4 . The single-chip tunable bandpass filter of claim 1 , wherein the all tuning components comprises a programmable resistor circuit coupled to the at least one tuning input.

5 . The single-chip tunable bandpass filter of claim 4 , further comprising a data register formed on the single-chip positioned between the at least one tuning input and the programmable resistor circuit to provide tuning data to select the programmed center frequency.

6 . The single-chip tunable bandpass filter of claim 5 , further comprising a serial programming interface formed on the single-chip between the at least one tuning input and the data register and configured to convert a serial data stream into the tuning data stored in the data register to program the programmable resistor circuit to select the programed center frequency.

7 . The single-chip tunable bandpass filter of claim 4 , wherein the all tuning components further comprises a voltage variable capacitor coupled to the at least one tuning input.

8 . The single-chip tunable bandpass filter of claim 7 , wherein the at least one tuning input includes a voltage input coupled to the voltage variable capacitor to select the programmed center frequency.

9 . The single-chip tunable bandpass filter of claim 1 , wherein the input and output formed on the single-chip further comprise a differential input and a differential output, respectively, matched to fifty ohms.

10 . The single-chip tunable bandpass filter of claim 4 , wherein the bandpass filter circuit comprises a third-order biquad bandpass filter circuit or a fifth-order biquad bandpass filter circuit.

11 . A single-chip tunable bandpass filter, comprising:
a plurality of single stage biquad bandpass filter circuits serially coupled on the single-chip, the bandpass filter circuit coupled to a differential input formed on the single-chip and configured to provide a bandpass filtered differential output signal; an output buffer configured on the single-chip to provide the bandpass filtered differential output signal to a differential output formed on the single-chip; all tuning components for the each of the plurality of single stage biquad bandpass filter circuits formed on the single-chip; and a tuning input formed on the single-chip and coupled to a data register providing tuning data to each of the plurality of single stage biquad bandpass filter circuits for adjusting the all tuning components for tuning the bandpass filter circuit to a programmed center frequency; wherein, no tuning components are external to the single-chip for tuning the bandpass filter circuit to the programmed center frequency.

12 . The single-chip tunable bandpass filter of claim 11 , wherein the plurality of single stage biquad bandpass filter circuits comprises three serially coupled single stage biquad bandpass filter circuits forming a third order bandpass filter.

13 . The single-chip tunable bandpass filter of claim 11 , wherein the plurality of single stage biquad bandpass filter circuits comprises five serially coupled single stage biquad bandpass filter circuits forming a fifth order bandpass filter.

14 . The single-chip tunable bandpass filter of claim 11 , further comprising a serial programming interface formed on the single-chip between the at least one tuning input and the data register and configured to convert a serial data stream into the tuning data stored in the data register to program a programmable resistor circuit to select the programed center frequency.

15 . The single-chip tunable bandpass filter of claim 14 , wherein the tuning data comprises four control bits for each of the plurality of single stage biquad bandpass filter circuits providing sixteen states for the programmed center frequency.

16 . The single-chip tunable bandpass filter of claim 11 , wherein the all tuning components further comprises a voltage variable capacitor coupled to a voltage input position on the single-chip.

17 . The single-chip tunable bandpass filter of claim 16 , wherein the voltage input is coupled to a voltage variable capacitor to adjust the programmed center frequency.

18 . The single-chip tunable bandpass filter of claim 11 , wherein the differential input and differential output formed on the single-chip are matched to fifty ohms.

19 . A method of programming a center frequency of a single-chip tunable bandpass filter having all tuning components located on the single-chip, comprising:
receiving a serial data stream at a serial programming interface; converting the serial data stream to tuning data and storing the tuning data in a data register; and providing control bits from the data register to each of a plurality of serially coupled single stage biquad bandpass filter circuits to vary a programmable resistor located on the single-chip within each of the serially coupled single stage biquad bandpass filter circuits thereby adjusting the center frequency of the single-chip tunable bandpass filter.

20 . The method of claim 19 , wherein four control bits are provided to each of a plurality of serially coupled single stage biquad bandpass filter circuits providing sixteen programming states for the programmed center frequency of the single-chip tunable bandpass filter.

Assignees

• Gm Global Tech Operations Llc

Inventors

• Sovero Emilio A
• Kang Jongchan
• Ahmed Mohiuddin
• Li James Chingwei
• Baringer Cynthia D
• Kuan Yen-Cheng
• Talty Timothy J

Classifications

• H03J3/185 Primary

  with varactors, i.e. voltage variable reactive diodes · CPC title

• H03H11/1256 Primary

  Tow-Thomas biquad · CPC title

• H03H2210/012

  Centre frequency; Cut-off frequency · CPC title

• H03H2210/028

  Resistor · CPC title

• H03J2200/33

  Tuning of filter by controlling transconductance · CPC title