Image reject filtering in a direct sampling mixer

A technology of image suppression and mixer, which is applied in the direction of improving frequency converters, networks using time-varying components, switched capacitor networks, etc., to achieve the effect of reducing chip area and cost, and reducing dynamic range requirements

Inactive Publication Date: 2007-10-24
TEXAS INSTR INC
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

This type of switched capacitor network suffers from the same power dissipation and cost issues as other switched capacitor networks, in large part because it relies on the use of operational amplifiers

Method used

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  • Image reject filtering in a direct sampling mixer
  • Image reject filtering in a direct sampling mixer
  • Image reject filtering in a direct sampling mixer

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Embodiment Construction

[0023] In general, preferred embodiments of the present invention provide bandpass and image rejection filtering in direct sampling mixers of IF or RF systems. This is achieved by using rotating capacitors in the in-phase I and quadrature Q branches of the system denoted by I+, I-, Q+, Q- respectively. The exchange of information in the branches of the I and Q channels enables the implementation of the complex filter. It should be appreciated that the preferred embodiment of the invention can be practiced without the use of operational amplifiers.

[0024] Referring first to Figure 1, the method of the present invention is depicted in a block diagram where it can be seen that the switched capacitor C between the I and Q channels of the circuit R The rotation of causes the sharing of charges in the four paths I+, I-, Q+, Q-, resulting in a direct sampling and complex filtering configuration 10 . It can be seen that the shown preferred embodiment of the filter 10 has four sub-...

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PUM

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Abstract

Disclosed are methods, circuits and systems for image reject filtering in a multi-tap direct sampling mixer (MTDSM) of an IF or RF system. Disclosed is the use of rotating capacitors among the in-phase and quadrature branches of a signal processing system. The exchange of information among the branches of the I and Q channels is used in the implementation of a complex filter. Rotation of a switched capacitor CR between the I and Q channels of the circuit causes a sharing of the charge among the four paths, I+, I-, Q+, Q-, resulting in a direct sampling and a complex filtering arrangement (10). The preferred embodiment of the filter (10) shown can be seen to have four sub-circuits (12, 14, 16, 18), which may be understood as single-pole IIR filters. Embodiments using cascaded multiple stages of the complex filter to provide higher order complex filters are also disclosed.

Description

technical field [0001] The present invention relates to signal processing circuits and methods. More particularly, the present invention relates to methods and circuits for image rejection filtering in direct sampling mixers. Background technique [0002] Integrated radio transmitters and receivers have become increasingly popular. Efforts to provide intermediate frequency (IF) and radio frequency (RF) devices integrated on a single chip face many challenges. A particular problem is the need to eliminate or suppress image signals by providing bandpass filtering in transceiver devices designed for portable wireless applications. These applications require low power consumption, small silicon area, few external components and highly integrated single chip. [0003] Quadrature signaling schemes are known. Quadrature signaling incorporates the technique of processing the input in terms of an in-phase signal component (I) and a quadrature (Q) signal component using a carrier ...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H04B1/69H03D7/18H03H19/00H04B1/16H04B1/28
CPCH03H2007/0192H03H19/004H03D7/18
Inventor 胡拉姆·穆罕默德罗伯特·B·斯塔谢夫斯基迪尔克·莱波尔德
Owner TEXAS INSTR INC
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