Harmonic suppression mixer and tuner
First Claim
1. A harmonic suppression mixer, for use in selecting a narrowband signal from a wideband signal, with a radio frequency (RF) input to accept the wideband signal, a local oscillator (LO) input for determining the nanowband signal selection, and complex in-phase (I) and quadrature (Q) outputs comprising:
- a plurality of switching mixers each with an RF input, an LO input, and an output;
each switching mixer driven by the RF input signal;
a plurality of I gain stages, one I gain stage coupled to each switching mixer output;
a plurality of Q gain stages, one Q gain stage coupled to each switching mixer output;
each I gain stage output coupled to a first summing node to produce the I output; and
each Q gain stage output coupled to a second summing node to produce the Q output;
whereby the I and Q outputs include the selected narrowband signal.
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Abstract
A harmonic suppression mixer for down converting an RF signal to a complex I and Q baseband signal that uses a plurality of switching mixers each with a gain stage to produce a sinusoidal weighted sum of the mixer outputs. Odd harmonics output by each switching mixer is suppressed in the composite signal. A low skew local oscillator (LO) clock generator creates multiple LO phases and drives the mixers. The mixer can be used in low noise direct conversion RF tuners. The mixer is configurable by programming gain stage coefficient values to achieve a variable number of effective mixers used in combination. At low tuning frequencies, all available mixers are programmed with unique coefficients and driven by different LO clock phases to achieve maximum harmonic suppression. At high tuning frequencies, some mixers are paralleled and duplicate coefficients are programmed or mixers are disabled to reduce the number of effective mixers.
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Citations
19 Claims
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1. A harmonic suppression mixer, for use in selecting a narrowband signal from a wideband signal, with a radio frequency (RF) input to accept the wideband signal, a local oscillator (LO) input for determining the nanowband signal selection, and complex in-phase (I) and quadrature (Q) outputs comprising:
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a plurality of switching mixers each with an RF input, an LO input, and an output; each switching mixer driven by the RF input signal; a plurality of I gain stages, one I gain stage coupled to each switching mixer output; a plurality of Q gain stages, one Q gain stage coupled to each switching mixer output; each I gain stage output coupled to a first summing node to produce the I output; and each Q gain stage output coupled to a second summing node to produce the Q output; whereby the I and Q outputs include the selected narrowband signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 12)
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10. A harmonic suppression mixer for down converting an RF signal input to an IF signal output comprising:
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a plurality of switching mixers driven by the RF signal, each mixer having an input, an LO input and an output, and means for programming the mixer gain; a summer for summing the plurality of mixer outputs to form the IF signal output; and an LO generator for generating a plurality of LO signals, wherein each LO signal has a predetermined phase relative to each other LO signal, the LO signals connected to drive the LO input of the mixers.
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11. A method of tuning a narrowband signal from a wideband radio frequency (RF) signal comprising:
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receiving the wideband RF signal; downconverting the RF signal to a lower frequency signal using harmonic suppression mixing by driving a plurality of mixers with a plurality of local oscillator (LO) signals and with the RF signal; applying gain to each mixer signal; summing the outputs of the mixers to produce the lower frequency signal wherein each mixer signal contributes to a composite waveform; and filtering the lower frequency signal to restrict the bandwidth of the signal. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19)
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Specification