Switched capacitor mixer circuit to attain high gain and linearity in radio frequency receivers
AssigneeTexas Instruments Incorporated
InventorMrinal Das
Life of this patent
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Abstract
By implementing the sampling process at an AC ground node, rather than at a signal side, and adding a gated transistor (610 and 620) in the signal path, the present invention reduces the interdependency between gain and linearity in a switched capacitor mixer circuit, supplies higher power without sacrificing area and simplifies the implementation of the RF switch. Charge boosting circuitry (630) allows a reduction in the effective size of a series switch (610 and 620) that follows a transconductance element (115).
Claims19
A switched capacitor mixer circuit, comprising:
- a transconductance element having an input tied to a supply voltage node and an output coupled to a first node, said output further coupled to a second node;
- a first capacitor tied to said first node;
- a second capacitor tied to said second node;
- a first switch coupled to said first capacitor, said first switch further tied to an AC ground node;
- a second switch coupled to said second capacitor, said second switch further tied to said AC ground node;
- a third switch tied to said first node, said third switch further tied to a first output node;
- and
- a fourth switch tied to said second node, said fourth switch further tied to a second output node.
A mixer circuit, comprising:
- a first input for receiving a radio frequency signal;
- a second input for receiving an oscillator frequency signal;
- an AC ground node;
- and
- a sampling circuit coupled to said first and second inputs and said AC ground node and responsive to said oscillator frequency for sampling said radio frequency signal at said AC ground node to create a sampled signal.
A method for mixing a radio frequency signal, the method comprising:
- receiving a radio frequency signal;
- receiving an oscillator frequency signal;
- and
- sampling said radio frequency signal at an AC ground node in response to said oscillator frequency signal to create a sampled signal.
A system for mixing a radio frequency signal, the system comprising:
- an amplifier stage for receiving and amplifying a radio frequency signal;
- a mixer stage having an AC ground node, said mixer stage coupled to said amplifier stage for receiving said amplified radio frequency signal from said amplifier stage;
- and
- said mixer stage having an input for receiving an oscillator frequency signal, said mixer stage including sampling circuitry coupled to said mixer input and said AC ground node and responsive to said oscillator frequency signal for sampling said amplified radio frequency signal at said AC ground node to create a sampled signal.
Dependencies are inferred from the claim text.