A Low IF Receiver with High Image Rejection Ratio

Abstract

The invention discloses a low and medium frequency receiver with a high image rejection ratio. The basic structure of the low and medium frequency receiver comprises an antenna, a low noise amplifier, a frequency synthesizer, a frequency mixer and a filter. The special structure of the low and medium frequency receiver is that an amplitude phase correction circuit is respectively connected to I and Q branches of the quadrature local oscillator signal output of the frequency synthesizer, each of the amplitude phase correction circuits is formed by two groups of CMOS amplifiers which are used for an amplitude-adjusting programmable cascade structure and a group of RC network load which is used for changing phase and is provided with a programmable capacitor array, the positive electrode and the negative electrode of any branch are connected to a group of CMOS amplifiers through a field effect transistor, and nodes between two groups of CMOS amplifiers corresponding to positive and negative electrode connection and the RC network load are outputted positive and negative electrodes after amplitude phase calibration. The low and medium frequency receiver in the scheme is applied, two branch signals are matched through amplitude and phase calibration, the image rejection ratio in the low and medium frequency receiver is raised, and the performance of the receiver is improved further.

Description

technical field [0001] The invention relates to a signal receiver, in particular to a low-intermediate frequency receiver which is favorable for high integration, low in cost and superior in image rejection ratio, and belongs to the field of communication receiver devices. Background technique [0002] Due to objective requirements and market competition, the receiver is required to have the characteristics of low power consumption, high integration, small size, and low price under the premise of maintaining high performance. Under the current highly mature digital-to-analog, analog-to-digital converter technology and digital technology, the performance of the receiver is mainly determined by its RF front-end, so the system structure adopted by the RF front-end has a very important impact on its performance. [0003] For the receiver, there are mainly three structures, superheterodyne receiver, zero-IF receiver and low-IF receiver. Specifically, superheterodyne receivers ge...

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Problems solved by technology

[0005] Considering that the above-mentioned low-IF receiver is insufficient in actual application, the purpose of the present invention is to propose a low-IF receiver with a high image rejection ratio to solve the problem that the performance of the receiver is seriously interfered by the image signal

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