Low-cost receiver using integrated inductors

• US 9,479,199 B2
• Filed: 11/02/2015
• Issued: 10/25/2016
• Est. Priority Date: 01/03/2012
• Status: Active Grant

• Current Assignee: Silicon Laboratories Incorporated
• Original Assignee: Silicon Laboratories Incorporated
• Inventors: Koroglu, Mustafa H., Su, Yu
• Primary Examiner(s): Le, Lana N
• Application Number:
  US14/930,139
• Publication Number:
  US 20160056845A1
• Time in Patent Office: 358 Days
• Field of Search: None
• US Class Current: 1/1
• CPC Class Codes: H03F 1/565 using inductive elements
• CPC Class Codes: H03F 2200/171 A filter circuit coupled to the output of an amplifier
• CPC Class Codes: H03F 2200/294 the amplifier being a low noise amplifier [LNA]
• CPC Class Codes: H03F 2200/451 the amplifier being a radio frequency amplifier
• CPC Class Codes: H03F 3/19 with semiconductor devices only
• CPC Class Codes: H03F 3/193 with field-effect devices H03F3/195 takes precedence
• CPC Class Codes: H03H 11/1291 Current or voltage controlled filters
• CPC Class Codes: H03H 2210/025 Capacitor
• CPC Class Codes: H03H 2210/033 Continuous
• CPC Class Codes: H03H 7/0169 Intermediate frequency filters
• CPC Class Codes: H03H 7/09 Filters comprising mutual inductance
• 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: H03J 2200/32 Tuning of tracking filter
• CPC Class Codes: H03J 3/10 Circuit arrangements for fine tuning, e.g. bandspreading
• CPC Class Codes: H04B 1/005 adapting radio receivers, transmitters andtransceivers for operation on two or more bands, i.e. frequency ranges
• CPC Class Codes: H04B 1/16 Circuits
• CPC Class Codes: H04B 1/1638 Special circuits to enhance selectivity of receivers not otherwise provided for resonant circuits H03H
• CPC Class Codes: H04B 1/18 Input circuits, e.g. for coupling to an antenna or a transmission line coupling networks between antennas or lines and receivers independent of the nature of the receiver H03H

Abstract

A receiver includes a first amplifier having an input for receiving a radio frequency (RF) signal, and an output for providing an amplified RF signal, a switch section for selectively switching the RF signal onto one of a plurality of nodes, and a filter section comprising a plurality of filters coupled to respective ones of the plurality of nodes. A first filter of the plurality of filters comprises a first variable capacitor coupled in parallel with an inductance leg between a corresponding one of the plurality of nodes and a power supply voltage terminal, wherein the first variable capacitor has a capacitance that varies in response to a tuning signal, and the inductance leg comprises a first inductor in series with an effective resistance, wherein the effective resistance has a value related to an upper cutoff frequency to be tuned by the first filter.

Claims

1. A receiver comprising:

a first amplifier having an input for receiving a radio frequency (RF) signal, and an output for providing an amplified RF signal;

a switch section for selectively switching the RF signal onto a selected one of a plurality of nodes; and

a filter section comprising a plurality of filters coupled to respective ones of the plurality of nodes,

wherein a first filter of the plurality of filters comprises a first variable capacitor coupled in parallel with an inductance leg between a corresponding one of the plurality of nodes and a power supply voltage terminal, wherein the first variable capacitor has a capacitance that varies in response to a tuning signal, and the inductance leg comprises a first inductor in series with an effective resistance, wherein the effective resistance has a value related to an upper cutoff frequency to be tuned by the first filter.

2. The receiver of claim 1, further comprising:

a resistor having a first terminal coupled to the output of the first amplifier, and a second terminal coupled to a first terminal of the inductor, wherein the effective resistance of the inductance leg is equal to a resistance of the resistor plus a parasitic resistance of the inductor.

3. The receiver of claim 1, wherein the first variable capacitor comprises:

a fixed capacitor having a first terminal coupled to the output of the first amplifier, and a second terminal coupled to the power supply voltage terminal;

a binary capacitor having a first terminal coupled to the output of the first amplifier, a second terminal coupled to the power supply voltage terminal, and a control terminal for receiving a binary coded signal; and

a thermometer capacitor having a first terminal coupled to the output of the first amplifier, a second terminal coupled to the power supply voltage terminal, and a control terminal for receiving a thermometer coded signal.

4. The receiver of claim 1, further comprising:

a second amplifier having an input coupled to the output of the first amplifier, and first and second outputs forming a differential signal pair;

a second variable capacitor having a first terminal coupled to the first output of the second amplifier, and a second terminal coupled to the second output of the second amplifier, and a tuning input terminal; and

a second inductor having a first terminal having a first terminal coupled to the first output of the second amplifier, and a second terminal coupled to the second output of the second amplifier.

5. The receiver of claim 1, wherein the plurality of filters comprises:

a second filter having an input selectively coupled to the output of the first amplifier through the switch section for attenuating components of the output of the first amplifier below the upper cutoff frequency of the first filter and above an upper cutoff frequency of the second filter; and

a third filter having an input selectively coupled to the output of the first amplifier through the switch section for attenuating components of the output of the first amplifier below the upper cutoff frequency of the second filter.

6. The receiver of claim 5, wherein the upper cutoff frequency of the first filter is approximately equal to 190 megahertz (MHz).

7. The receiver of claim 6, wherein the third filter comprises:

a third variable capacitor including a first terminal coupled to the output of the first amplifier, and a second terminal coupled to a second power supply voltage terminal; and

a transformer including a primary winding having a first terminal coupled to the first terminal of the third variable capacitor and a second terminal coupled to a third power supply voltage terminal, and a secondary winding having a first terminal and a second terminal for providing a differential filtered radio frequency signal thereto.

8. The receiver of claim 7, wherein the upper cutoff frequency of the second filter is approximately equal to 470 MHz.

9. The receiver of claim 1, wherein the RF signal comprises a television signal.

10. The receiver of claim 9, wherein the switch section selectively switches the RF signal onto a selected one of the plurality of nodes in response to a desired channel.

11. A method comprising:

receiving a radio frequency (RF) input signal;

amplifying the RF input signal to form an amplified RF input signal;

selectively switching the amplified RF input signal to one of a plurality of nodes;

filtering the amplified RF signal using a selected one of a plurality of filters coupled to respective ones of the plurality of nodes; and

in response to switching the amplified RF signal onto a first of the plurality of nodes, filtering the amplified RF input signal using a first filter of the plurality of filters, wherein the first filter comprises a first variable capacitor coupled in parallel with an inductance leg between a corresponding one of the plurality of nodes and a power supply voltage terminal, wherein the first variable capacitor has a capacitance that varies in response to a tuning signal, and the inductance leg comprising a first inductor in series with an effective resistance, wherein the effective resistance has a value related to an upper cutoff frequency to be tuned by the first filter.

12. The method of claim 11, further comprising selectively switching the amplified RF input signal to one of the plurality of nodes corresponding to a desired frequency band.

13. The method of claim 12 further comprising:

selectively switching the amplified RF signal onto a second node coupled to a second filter, wherein the second filter attenuates components of the amplified RF signal below the upper cutoff frequency of the first filter and above an upper cutoff frequency of the second filter; and

selectively switching the amplified RF signal onto a third node coupled to a third filter, wherein the third filter attenuates components of the amplified RF signal below the upper cutoff frequency of the second filter.

14. The method of claim 13, wherein receiving the RF signal further comprises receiving a television signal.

15. The method of claim 14, wherein selectively switching the amplified RF input signal to one of the plurality of nodes comprises selectively switching the amplified RF input signal to one of the plurality of nodes in response to a desired channel.

16. The method of claim 11, further comprising:

forming the effective resistance by coupling a resistor in series with the first inductor, wherein the effective resistance of the inductance leg is equal to a resistance of the resistor plus a parasitic resistance of the inductor.

17. The method of claim 11, further comprising forming the first variable capacitor with a parallel combination of:

a fixed capacitor;

a binary capacitor having a control terminal for receiving a binary coded signal; and

a thermometer capacitor having a control terminal for receiving a thermometer coded signal.

18. The method of claim 11, wherein filtering the amplified RF input signal using the first filter of the plurality of filters further comprises:

further amplifying the amplified signal; and

further filtering the further amplified signal using a second variable capacitor in parallel with a second inductor.

19. The method of claim 18, further comprising forming the second variable capacitor with a parallel combination of:

a fixed capacitor;

a binary capacitor having a control terminal for receiving a binary coded signal; and

a thermometer capacitor having a control terminal for receiving a thermometer coded signal.

20. The method of claim 18, wherein:

the further amplifying the amplified signal comprises further amplifying the amplified signal to provide the further amplified signal as a differential signal; and

the further filtering comprises differentially filtering the differential signal using the second variable capacitor in parallel with the second inductor.