Low noise mixer circuit with improved gain
First Claim
1. A mixer circuit comprising:
- a gain stage coupled to receive a first signal on a first input and a modulated bias current on a common node, and in accordance therewith, produce an output signal, the gain stage having a first current;
a current shunt circuit coupled between the common node and a reference voltage, the current shunt circuit providing a second current from the reference voltage to the common node, wherein the first current and the second current are coupled to the common node; and
a bias circuit to generate the modulated bias current, the bias circuit having an input coupled to receive a second signal, and in accordance therewith, generate the modulated bias current, and an output coupled to the common node to provide the modulated bias current to the gain stage.
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Abstract
A mixer circuit of the present invention includes a gain stage configured to receive a first signal and a modulated bias current, and in accordance therewith, produce an output signal, the gain stage generating a first current and receiving the modulated bias current from a bias circuit on a common node. The bias circuit includes an input configured to receive a second signal, and in accordance therewith, generate the modulated bias current. The mixer circuit also includes a current shunt circuit for generating a second current. The first current, the second current, and the modulated bias current are coupled to the common node. In one embodiment, the first signal is approximately a square wave, and the frequency of the first signal is one-third the frequency of the second signal.
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Citations
24 Claims
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1. A mixer circuit comprising:
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a gain stage coupled to receive a first signal on a first input and a modulated bias current on a common node, and in accordance therewith, produce an output signal, the gain stage having a first current;
a current shunt circuit coupled between the common node and a reference voltage, the current shunt circuit providing a second current from the reference voltage to the common node, wherein the first current and the second current are coupled to the common node; and
a bias circuit to generate the modulated bias current, the bias circuit having an input coupled to receive a second signal, and in accordance therewith, generate the modulated bias current, and an output coupled to the common node to provide the modulated bias current to the gain stage. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18)
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19. A method of mixing signals in a mixer circuit comprising:
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generating a first current in a differential stage;
generating a second current in a shunt circuit coupled between the common node and a reference voltage, the second current provided from the reference voltage to the common node;
coupling the first current and the second current through a common node to generate a bias current in a bias circuit;
receiving an RF signal in the bias circuit;
receiving a second signal in the differential stage; and
generating a mixer output in accordance with the RF signal and the second signal. - View Dependent Claims (20, 21, 22, 23, 24)
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Specification