Low noise, low distortion, muxable Gilbert mixer signal processing system and method with AGC functionality

• US 6,931,083 B1
• Filed: 05/26/2000
• Issued: 08/16/2005
• Est. Priority Date: 05/26/2000
• Status: Expired due to Term

• Current Assignee: Microelectronics Technology Inc (MTI Laboratory Inc)
• Original Assignee: TelASIC Communications, Inc. (MTI Laboratory Inc)
• Inventors: Duong, Clifford N., Devendorf, Don C., Linder, Lloyd F.
• Primary Examiner(s): Chin, Stephen
• Assistant Examiner(s): ODOM, CURTIS B
• Application Number:
  US09/579,596
• Time in Patent Office: 1,908 Days
• Field of Search: 375/316, 375/219, 375/345, 375/298, 375/340, 375/130, 375/341, 455/73, 455/291, 455/553.1, 455/321, 327/113
• US Class Current: 375/345
• CPC Class Codes: H03D 7/1425 with transistors
• CPC Class Codes: H03D 7/1433 using bipolar transistors H03D7/145 takes precedence
• CPC Class Codes: H03D 7/1458 Double balanced arrangements, i.e. where both input signals are differential
• CPC Class Codes: H03D 7/1491 Arrangements to linearise a transconductance stage of a mixer arrangement

Abstract

A signal processing system and method. The inventive system includes a first circuit for distributing an input signal between two or more channels in a current mode of operation. A second circuit is disposed in each of the channels for processing the input signal and providing an output signal in response thereto. A third circuit is provided to combine the signals output by the processing circuit. A fourth circuit is included for controlling the first and the third circuits. In a specific illustrative embodiment, the system further includes a radio frequency stage for downconverting a received signal and providing the input signal in response thereto. In the specific embodiment, the first circuit includes a mixing circuit. The mixing circuit includes Gilbert cells and circuitry for providing automatic gain control for each of the channels individually. The Gilbert cells and the automatic gain control circuitry are driven by a transconductance amplifier and therefore operate in a current mode. Differential digital automatic gain control signals are provided in response to a channel select signal from a digital control circuit. The inventive circuit provides multiple IF channels which may be filtered individually. The invention thereby provides wide band operation in a simple, single stage implementation that consumes little power. Further, the current mode thereof is effective in the reduction of insertion loss.

Claims

1. A signal processing system comprising:

means for receiving an incoming radio frequency signal;

means for narrowing the received incoming signal to a limited frequency band;

means for amplifying the narrowed incoming signal;

means for rejecting an image of the narrowed incoming signal to output an input signal;

means for distributing the input signal to one of two or more channels;

means disposed in each of said channels for processing the distributed signal and providing an output signal in response thereto, wherein only one of said processing means is active at a time; and

means for combining the signals output by two or more said processing means,

wherein said distribution means further includes means for providing automatic gain control for each of said channels.

2. The invention of claim 1 wherein said means for providing automatic gain control operates in a current mode.

3. The invention of claim 1 wherein said means for providing automatic gain control includes a digital automatic gain control circuit.

4. A signal processing system comprising:

means for receiving an incoming radio frequency signal;

means for narrowing the received incoming signal to a limited frequency band;

means for amplifying the narrowed incoming signal;

means for rejecting an image of the narrowed incoming signal to output an input signal;

means for distributing the input signal to one of two or more channels;

means disposed in each of said channels for processing the distributed signal and providing an output signal in response thereto, wherein only one of said processing means is active at a time; and

means for combining the signals output by two or more said processing means,

wherein said distribution means includes a mixing circuit, and

wherein said mixing circuit further includes means for selectively providing differential digital automatic gain control signals in response to a channel select signal.

5. A signal processing system comprising:

means for receiving an incoming radio frequency signal;

means for narrowing the received incoming signal to a limited frequency band;

means for amplifying the narrowed incoming signal;

means for rejecting an image of the narrowed incoming signal to output an input signal;

means for distributing the input signal to one of two or more channels;

means disposed in each of said channels for processing the distributed signal and providing an output signal in response thereto, wherein only one of said processing means is active at a time; and

means for combining the signals output by two or more said processing means,

wherein said distribution means includes a mixing circuit, and

wherein said mixing circuit includes at least one Gilbert cell.

6. A signal processing system comprising:

means for receiving an incoming radio frequency signal;

means for narrowing the received incoming signal to a limited frequency band;

means for amplifying the narrowed incoming signal;

means for rejecting an image of the narrowed incoming signal to output an input signal;

means for distributing the input signal to one of two or more channels;

means disposed in each of said channels for processing the distributed signal and providing an output signal in response thereto, wherein only one of said processing means is active at a time; and

means for combining the signals output by two or more said processing means,

wherein said distribution means includes a mixing circuit, and

wherein said mixing circuit includes a transconductance amplifier.

7. The invention of claim 6 wherein said mixing circuit includes an automatic gain control circuit.

8. A receiver comprising:

a radio frequency stage for downconverting a received signal and providing said input signal in response thereto;

a distributor for distributing said input signal to one of two or more channels, said distributor including a mixing circuit having;

a Gilbert cell for each channel,

an automatic gain control circuit for each channel in communication with a respective one of said Gilbert cells, and

a transconductance amplifier in communication with said automatic gain control circuits;

a filter disposed in each of said channel for processing said distributed signals and outputting the processed signals; and

a combining circuit for combining the signals output by said processing means.

9. A signal processing circuit comprising:

a receiver for receiving an incoming signal;

a pre select filter connected to the receiver for filtering the received incoming signal;

a low noise amplifier connected to the pre select filter for amplifying the filtered incoming signal;

an image rejection filter connected to the low noise amplifier for rejecting predetermined images of the amplified incoming signal to thereby output an incoming signal;

a distributor connected to the image rejection filter for distributing the input signal to one of at least two channels in a current mode of operation, wherein each of said at least two channels include a Gilbert cell;

an intermediate-frequency filter disposed in each of said two channels for processing said input signal and providing an output signal in response thereto, wherein only one of said intermediate-frequency filters is active at a time; and

a multiplexer connected to the outputs of each intermediate-frequency filter for combining the signals output by each of said intermediate-frequency filter.

10. A receiver comprising:

a radio frequency stage for downconverting a received signal and providing said input signal in response thereto;

a distributor for distributing said input signal to one of at least two channels in a current mode of operation, said distributor including a mixing circuit having;

a Gilbert cell for each channel,

an automatic gain control circuit for each channel operatively coupled with a respective one of said Gilbert cells, and

a transconductance amplifier operatively coupled with said automatic gain control circuits; and

a filters disposed in each of said channels for processing said input signal and providing an output signal in response thereto.