Radio frequency automatic gain control amplifier

Abstract

The invention discloses a radio frequency automatic gain control amplifier. The radio frequency automatic gain control amplifier comprises a radio frequency receiving unit, a radio frequency amplifier control unit and an intermediate frequency amplifier, wherein the radio frequency receiving unit is composed of an adjustable low noise amplifier (LNA), a programmable gain amplifier (PGA), a down-conversion frequency mixer and a low-pass filter; the radio frequency amplifier control unit comprises a signal strength detector, a DAC (digital-to-analog converter), a comparator and a decoder; the signal strength detector is used for detecting the strength of an intermediate frequency signal; a comparator circuit is used for comparing an output signal of the signal strength detector with a fixed comparing level output from the DAC so as to output a comparison result; the decoder is used for inputting the comparison result into a gain control digital module and outputting a digital control signal so as to carry out the feedback control to the signal at the front end of the radio frequency, so that the gains of the LNA and the PGA are controlled, the signal to noise ratio of a receiving system is increased, and the requirements on dynamic ranges and high linearity of an input signal are met. The automatic gain control amplifier can be used in various radio frequency receiving chips flexibly, and particularly is applicable to radio frequency front-end circuit which has a wider input range of a radio frequency signal.

Description

Contents of the invention [0001] The invention belongs to the technical field of radio frequency communication, and relates to a radio frequency automatic gain control adjustment circuit mode, in particular to a radio frequency automatic gain control amplifier, which adopts a different gain adjustment mode than the traditional one, and is suitable for a radio frequency receiver receiving signals with a large dynamic range. Background technique [0002] In recent years, with the continuous emergence of new technologies in the field of information technology and the continuous progress of technology, the input signal range of various receiver systems has changed greatly compared with the original ones. Interference is becoming more and more serious. For applications with weak input and large interference, the receiver needs to provide a large input range and dynamic range. [0003] As we all know, when different RF signals work at the same time, interference signals from other...

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Problems solved by technology

[0005] There are many disadvantages in the prior art controllable gain amplifier: first, the traditional control method adopts the scheme of controlling the intermediate frequency adjustable gain amplifier, which can only be suitable for the situation where the dynamic range of the input signal is small, and is not suitable for applications with large dynamic range input conditions

Second, the traditional design does not consider that the RF gain can be adjusted. The actual problem is that when the input signal is large, it is easy to saturate the RF part, and the intermediate frequency control alone cannot meet the existing design requirements.

Third, the traditional control method is mainly based on the requirement of reducing the noise figure of the system to set the front-end gain as a fixed size. However, the fixed RF front-end cannot meet the high linearity requirements, and the fixed gain will worsen the signal-to-noise ratio of the RF receiver system, which will eventually affect the system performance.

[0009] The present invention will abandon the problem that the traditional structure cannot deal with the saturation of the radio frequency amplifier due to too large input signal, and proposes a radio frequency automatic gain control amplifier. The signal is amplified, while the front end provides low noise, the excessive signal is reduced, and the linearity of the system is improved, the circuit overhead and power consumption are reduced, the performance of the system is improved, and the sensitivity of the RF receiver is improved, and the power of the device can also be reduced. Consumption and volume, saving cost

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