Mixer noise reduction technique
First Claim
1. A mixer circuit comprising:
- a gain stage configured to receive a first signal and a bias current, and in accordance therewith, produce an output signal, the gain stage receiving the bias current on a common node;
a bias circuit having an input configured to receive a second signal and an output coupled to the common node to provide the bias current to the gain stage, the bias current comprising bias current frequency components; and
a frequency dependent current shunt circuit coupled between the common node and a reference voltage, wherein a first portion of the bias current frequency components within a first frequency range are coupled to the reference voltage by the shunt circuit, and a second portion of the bias current frequency components within a second frequency range are coupled to the reference voltage by the shunt circuit, the first portion being larger than the second portion, wherein the second frequency range is higher than the first frequency range.
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Abstract
In accordance with the present invention a mixer circuit noise reduction technique is provided. The mixer circuit of the present invention includes a gain stage for receiving a first signal and producing an output signal. The mixer circuit also includes a bias circuit coupled to the gain stage through a common node for providing a bias current to the gain stage, the bias circuit having an input for receiving a second signal, and in accordance therewith, varying the bias current. Additionally, the mixer circuit includes a frequency dependent current shunt circuit coupled between the common node and a reference voltage, wherein a first portion of the bias current frequency components within a first frequency range are coupled to the reference voltage by the shunt circuit, and a second portion of the bias current frequency components within a second frequency range are coupled to the reference voltage by the shunt circuit, the first portion being larger than the second portion. As a result, the noise in the mixer circuit is reduced while the gain is enhanced.
65 Citations
26 Claims
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1. A mixer circuit comprising:
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a gain stage configured to receive a first signal and a bias current, and in accordance therewith, produce an output signal, the gain stage receiving the bias current on a common node;
a bias circuit having an input configured to receive a second signal and an output coupled to the common node to provide the bias current to the gain stage, the bias current comprising bias current frequency components; and
a frequency dependent current shunt circuit coupled between the common node and a reference voltage, wherein a first portion of the bias current frequency components within a first frequency range are coupled to the reference voltage by the shunt circuit, and a second portion of the bias current frequency components within a second frequency range are coupled to the reference voltage by the shunt circuit, the first portion being larger than the second portion, wherein the second frequency range is higher than the first frequency range. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
a first transistor having a control input and first and second outputs, the control input coupled to receive a first component of the differential signal;
a second transistor having a control input and first and second outputs, the control input coupled to receive a second component of the differential signal; and
a load coupled to the first output of the first transistor and to the first output of the second transistor, wherein the second output of the first transistor and the second output of the second transistor are coupled together and to the common node.
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13. The mixer circuit of claim 12 wherein the first and second transistors are NMOS transistors.
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14. The mixer circuit of claim 12 wherein the load comprises a first resistor coupled between the first output of the first transistor and a supply voltage and a second resistor coupled between the first output of the second transistor and the supply voltage.
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15. The mixer circuit of claim 1 wherein the reference voltage is a supply voltage.
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16. A mixer circuit comprising:
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first and second transistors configured to receive a differential input signal, the first and second transistors coupled to a common node to receive a bias current;
a third transistor having a bias output coupled to the common node, the third transistor coupled to receive an RF signal and generate a bias current at the bias output; and
an inductor having a first terminal coupled to the common node and a second terminal coupled to a supply voltage;
wherein the bias current comprises bias frequency components, and a frequency dependent current shunt circuit couples a first portion of the bias current frequency components within a first frequency range to the supply voltage, and couples a second portion of the bias current frequency components within a second frequency range to the supply voltage, the first portion being larger than the second portion. - View Dependent Claims (17, 18, 19, 20, 21, 22)
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23. A method of reducing noise in a mixer comprising:
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receiving a first signal in a gain stage;
receiving a second signal in a bias circuit, the second signal having a first frequency;
generating a bias current in response to the second signal, the bias current having bias current frequency components including a frequency component at the first frequency;
shunting a first portion of the bias current frequency components within a first frequency range to a reference voltage and a second portion of the bias current frequency components within a second frequency range higher than the first frequency range to the reference voltage, the first frequency being in the second frequency range and the first portion being larger than the second portion; and
coupling the bias current to the gain stage to produce a mixer output. - View Dependent Claims (24, 25, 26)
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Specification