Direct conversion receiver
First Claim
1. A direct conversion receiver comprising:
- a pair of mixers which convert a receive signal frequency to a baseband frequency; and
a baseband frequency signal processing block including a pair of first amplifiers and a pair of first filters, following said mixers, wherein said baseband frequency signal processing block further includes a pair of negative feedback circuits with an adjustable feedback factor, each negative feedback circuit including a second filter of low-pass type.
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Accused Products
Abstract
In a direct conversion receiver, to cancel a DC offset generated in the baseband processing block, negative feedback arrangements comprising a gain control amplifier and a low-pass filter are respectively attached to the I and Q signal branches of the baseband block following mixer outputs. The gain control amplifier in each negative feedback circuit is gain adjusted so that the product G-B of the gain G of a primary gain control amplifier and its own gain B will be constant and thereby the DC offset is cancelled. This DC offset cancellation can be applied in a continuous receiving system with no intermittent time during a receiving operation. Capacitance elements located off-chip can be reduced to those to be used only in the low-pass filters in the negative feedback circuits, whereas many off-chip capacitance elements have been required to be inserted between each stage of gain control amplifiers in conventional baseband chains.
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Citations
20 Claims
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1. A direct conversion receiver comprising:
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a pair of mixers which convert a receive signal frequency to a baseband frequency; and
a baseband frequency signal processing block including a pair of first amplifiers and a pair of first filters, following said mixers, wherein said baseband frequency signal processing block further includes a pair of negative feedback circuits with an adjustable feedback factor, each negative feedback circuit including a second filter of low-pass type. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20)
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Specification