Three-stage automatic gain control device and its control method

Abstract

The invention provides a three-level automatic gain control device. The three-level automatic gain control device comprises a variable gain amplifier, an analog / digital converter and a feedback circuit, wherein the feedback circuit comprises a lookup table module, a threshold estimation module, a threshold error module, a gain step updating module, a gain counter and a digital / analog converter; the gain step updating module is used for comparing a threshold error with a three-level threshold value to obtain the gain step of a next update period; when the threshold error is smaller, the gain step is smaller; and the gain step is obtained through arithmetic shift. According to the three-level automatic gain control device, the three-level threshold value is adopted; processing at three levels is performed according to the threshold error to obtain the gain step of the next update period; and rapid adjustment and stable adjustment of a gain are realized. A reference threshold value is set to be 33 percent of the update period, so that optimal signal-to-noise ratio loss can be reached, and the device is suitable for processing data with a low signal-to-noise ratio. The device is suitable for all analog / digital converters with 2 bits and over. The invention further provides a three-level automatic gain control method.

Description

technical field [0001] The invention belongs to the technical field of digital communication circuits, and relates to a digital automatic gain control circuit, in particular to a three-stage automatic gain control device and a control method applied to a spread spectrum communication system. Background technique [0002] Digital integrated circuits are more and more widely used due to their superior data processing speed, good anti-noise ability, relatively small area and low power consumption. Therefore, in large-scale data processing, analog signals are usually used for data acquisition and conversion. It is a digital signal, after a series of processing, it is converted into an analog signal output. [0003] The function of the analog / digital converter is to realize the conversion from analog signal to digital signal. With the improvement of data processing precision, the analog / digital converter requires more bit width to meet the precision requirement. Due to factors ...

AI Technical Summary

Problems solved by technology

The way of lookup table reduces the computational complexity of the circuit and improves the speed of the circuit, but on the other hand, the calculation data of the lookup table method has its functional limitations. First, the data in the lookup table cannot cover all situations, such as In the automatic gain control device 2, if the look-up table 28 is a look-up table arranged by decreasing the input signal level by 0.25dB, it is not easy to obtain a suitable gain control signal when the signal change accuracy is less than 0.25dB. Secondly, for a larger dynamic range signal, the size of its lookup table must lead to a large circuit size

Images