Programmable/adjustable active electric resistance-capacitance wave filter and radio communication system

Abstract

A programmable / adjustable active low-pass filter for analog circuits, wherein a controllable shunt device is implemented by utilizing the linearity of field effect transistors. A linear analysis of the transfer function of the filter circuit shows that the cut-off frequency of the filter can be changed by determining the equivalent small-signal current through the controllable shunt device. Therefore, when the cut-off frequency is shifted due to changes in the circuit process or environmental parameters (such as temperature), the filter allows the user to continuously fine-tune the cut-off frequency by controlling the controllable shunt device to make the cut-off frequency can still maintain the original frequency value. In addition, different applications require different cutoff frequencies, the present invention also provides a method that can greatly change the cutoff frequency, and the cutoff frequency can be adjusted to the desired frequency value according to different application conditions, so that the same filter circuit Can be widely used for various purposes.

Description

technical field [0001] The invention relates to an analog filter circuit, in particular to a resistor-capacitor filter and a wireless communication system capable of fine-tuning and changing the cut-off frequency and gain of an active filter. Background technique [0002] A filter is a common and important unit in a signal processing system. Its function is to eliminate unwanted frequency band signals to retain or amplify required frequency band signals. In the advanced integrated circuit manufacturing process, it is a common trend to integrate the filter into the chip, especially in the communication market. With the continuous evolution and progress of the communication system, the signal processing circuit not only requires high-standard performance on the one hand, but also on the other hand. , it is often required to be able to switch and process signals of two systems in the same circuit at the same time; for example, the second / third generation (2nd / 3rd Generation) mo...

AI Technical Summary

Problems solved by technology

In this way, the number of components on the circuit will increase, the control efficiency will decrease, and it will also cause problems in the design of the integrated circuit.

In addition, the cutoff frequency of this filter can only be adjusted within a fixed range, so the application range is limited

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