A receiver and an agc control system capable of reducing noise figure and increasing isolation

Abstract

The invention discloses an AGC control system capable of reducing a noise coefficient and increasing isolation. An automatic gain control circuit comprises two radio frequency switches and a low noise amplifier; the low noise amplifier is connected between the two radio frequency switches; an output end of a coupling circuit is connected with an input end of a detection circuit, and the output end of the detection circuit is connected with the input end of a controller; the output end of the controller is separately connected with control ends of the two radio frequency switches and the low noise amplifier for judging whether a DC voltage signal is greater than a preset signal threshold, if so, controlling the two radio frequency switches to directly connect a receiving end with the coupling circuit and controlling the low noise amplifier to close; and otherwise, controlling the two radio frequency switches to connect the receiving end with the coupling circuit through the low noise amplifier. The AGC control system disclosed by the invention can avoid saturation distortion of the low noise amplifier in the case of large signals and can also reduce the influence of insertion loss to the overall noise coefficient of a receiver in the case of small signals. The invention further discloses a receiver comprising the above-mentioned system.

Description

technical field [0001] The invention relates to the technical field of automatic gain control, in particular to an AGC control system capable of reducing noise figure and increasing isolation. The invention also relates to a receiver. Background technique [0002] During the process of receiving signals, due to the uncertain location of the transmitter and the influence of surrounding environmental factors, the signal level at the receiving end will change in a wide range (as small as below the sensitivity level and as large as +10dBm). When the signal is large, in order to avoid saturation distortion of the low-noise amplifier (LNA) in the RF front-end, and to ensure that the subsequent RF link is always in a linear state, an automatic gain control circuit is usually designed in the front-end of the low-noise amplifier. [0003] see figure 1 and figure 2 as shown, figure 1 It is a structural schematic diagram of an existing receiver automatic gain system; figure 2 It...

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Problems solved by technology

exist figure 2 Among them, the AGC control circuit is designed at the back end of the low-noise amplifier. In the case of small signals, it can be known from the cascaded noise figure formula that the insertion loss of the two RF switches will not deteriorate the overall noise figure of the receiver, and the sensitivity of the receiver It will not affect, but in the case of large signal, the AGC control circuit cannot protect the low noise amplifier, and it is easy to cause saturation and distortion of the low noise amplifier, or even damage

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