A Low Noise Amplifier in a Radio Frequency Front End

Abstract

The invention discloses a low noise amplifier in a radio frequency front-end. The low noise amplifier comprises an amplification transistor and a common-gate transistor which are cascaded, wherein a filer is connected between the drain and the source of the common-gate transistor. The filter is arranged in the lower noise amplifier, belongs to an on chip filter, and has the beneficial effects of small size and low cost. The filter comprises an n-channel filter and an inverting amplifier which are cascaded, and is used for filtering and suppressing a block signal. The n-channel filter is controlled by using an n-phase local oscillator signal; and a switching tube is inevitably mismatched, so that the local oscillator signal is inevitably leaked to the source of the common-gate transistor namely the drain of the amplification transistor. The amplification transistor adopts a common-source connection mode, and signal strength of the local oscillator signal leaked to the antenna end is reduced by reverse isolation from the drain to the grid. Or the amplification transistor adopts a common-gate connection mode, and signal strength of the local oscillator signal leaked to the antenna end is reduced by reverse isolation from the drain to the source.

Description

technical field [0001] The present application relates to a radio frequency front-end circuit, in particular to a low noise amplifier (LNA) therein. Background technique [0002] A transceiver (transceiver) includes a transmitter (transmitter) and a receiver (receiver). The RF front end of the receiver usually refers to the circuit from the antenna to the mixer, including the mixer. The CMOS RF transceiver system used for 2G, 3G, 4G and other mobile communications includes multiple sets of transmitters and receivers. The high-power transmission signals generated by the transmitter will be coupled to the receiver in various ways, so that the receiver will face saturation. risk. At the same time, the signal received by the antenna is often accompanied by a high-power blocking signal, which will also saturate the receiver. In order to improve the receiver's suppression effect on blocking signals, some existing receiver radio frequency front-end solutions have been proposed. ...

AI Technical Summary

Problems solved by technology

The disadvantage of this solution is: due to the error in the manufacturing process, the sizes of the four switching tubes will not be completely equal, resulting in a mismatch between the four switching tubes

This causes the four-phase local oscillator signal to be coupled to the antenna and transmitted. The strength of the local oscillator signal transmitted by the antenna is too large, exceeding the upper limit of the spectrum specification, so it does not meet the spectrum specification.

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