Research And Design Of A Tunable High-Q Fourth-order Gm-C Bandpass Filter

In recent years,with the advancement of technology,the infrared remote control technology develops rapidly,and it has been applied in various fields.The most common one is the infrared audio receiving system.The design of the band-pass filter is particularly important in the infrared audio receiving system.It can effectively filter the interference of the outside ambient light and reduce the influence of the power supply ripple on the circuit,ensuring that the circuit can work normally in the environment affected by noise.The infrared audio receiving system usually needs to satisfy the requirement that both carrier frequencies can be used.When using the traditional implementation method,two filters are generally needed,which increases the overall area of the system.So,An integrated active filter that can be switched at two frequencies was designed in this article.The filter can be enriched the filter functions and reduced the overall system area.Firstly,this article describes the research background and significance of the subject and the current status of the filter research;then outlines the different types of filters and the reasons for choosing Gm-C filters;then learns the design of Gm-C filters Based on the synthesis principle,the double-two-level combination method was finally selected for the synthesis of the fourth-order Gm-C filter;then three typical linearizing operational transconductance amplifier was analyzed,a source negative feedback linear transconductance op amp with a common mode feedback circuit is designed;and the center frequency of the filter will change because of the influence of corner,temperature,etc.,comparing the advantages and disadvantages of two kinds of the tuning circuit architecture,a frequency tuning circuit based on a charge pump phase-locked loop was selected and designed.Due to the high Q value of the filter,the Q value tuning circuit based on the least mean square was studied and improved.Finally,based on the 0.25?m CMOS process,the filter structure proposed in this paper uses Cadence for circuit design,and uses Hspice software for circuit simulation.The simulation results are obtained by Hspice software and the data is sorted by Origin software.The simulation results show that the linear range of the OTA in this filter is 1V,the bandwidth of the filter is about 220 KHz,the center frequency can be switched between2.3MHz and 3.2MHz.Frequency tuning accuracy and Q value tuning accuracy are about 1%and 3.5%,respectively.