Low-cost receiver using integrated inductors

• US 9,209,838 B2
• Filed: 02/02/2015
• Issued: 12/08/2015
• 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:
  US14/612,232
• Publication Number:
  US 20150147991A1
• Time in Patent Office: 309 Days
• Field of Search: 455130-355
• 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 an RF signal, and an output for providing an amplified RF signal, a switch section that selectively switches the amplified 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. 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. The first variable capacitor has a capacitance that varies in response to a tuning signal. The inductance leg includes 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 signal, and an output;

a first filter having an input coupled to the output of the first amplifier, a tuning input, and an output, for substantially passing frequencies below a variable cutoff frequency, the variable cutoff frequency being less than an upper frequency threshold of the first filter;

a second filter having an input coupled to the output of the first amplifier, a tuning input, and an output, for substantially passing frequencies within a band above a lower threshold frequency of the second filter and below an upper threshold frequency of the second filter;

wherein the first filter comprises;

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

an inductance leg having a first terminal coupled to the output of the first amplifier, and a second terminal coupled to the power supply voltage terminal, the inductance leg including a first inductor and having an effective resistance in series with the inductor, 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 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 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 each of the upper frequency threshold of the first filter and the lower frequency threshold of the second filter is approximately equal to 190 megahertz (MHz).

6. The receiver of claim 1, further comprising:

a third filter having an input coupled to the output of the first amplifier, a tuning input, and an output, for substantially passing frequencies within a band above a lower threshold frequency of the third filter.

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 each of the upper frequency threshold of the second filter and the lower frequency threshold of the third filter is approximately equal to 470 MHz.