Filter and quality factor compensation method thereof

Abstract

The invention discloses a filter and a quality factor compensation method thereof. The filter comprises a first filter circuit, a second filter circuit, a third filter circuit, an input circuit and an output circuit. The first filter circuit and the second filter circuit are connected in series. The third filter circuit is in parallel connection with the first filter circuit and the second circuit. The input circuit is connected with the first filter circuit and the third filter circuit. The output circuit is connected with the second filter circuit and the third filter circuit. The advantages and beneficial effects are that through compensation of a quality factor Q value of the filter, the relatively ideal filtering characteristics can be maintained when the operational amplifier performance of the filter is not good. Therefore, the Q value of the filter is compensated, the gain bandwidth product of an operational amplifier needs not to be increased, the area of a resistor is avoided, the power consumption is reduced, and the filter is simple in structure and high in controllability.

Description

technical field [0001] The invention relates to the field of electronic information, in particular to a filter and a quality factor compensation method thereof. Background technique [0002] Filters are important in RF receiver chips. Its main function is to filter out out-of-band interference and suppress image signals. In low-IF receivers, IF complex filters are often used to simultaneously achieve filtering and image suppression. However, the existing IF complex filters have a relatively high center frequency and a relatively large bandwidth. At this time, the limited gain-bandwidth product of the operational amplifier will cause the filter characteristics to deviate from their ideal state, making the quality factor Q value larger. The larger the quality factor Q value, the lower the cutoff frequency and bandwidth will be, and there will be a relatively high gain overshoot near the cutoff frequency, which will destroy the flatness of the passband, such as image 3 shown....

AI Technical Summary

Problems solved by technology

However, the existing intermediate frequency complex filter has a relatively high center frequency and a relatively large bandwidth. At this time, the limited gain-bandwidth product of the operational amplifier will cause the filter characteristics to deviate from its ideal state, making the quality factor Q value larger

The larger the quality factor Q value, the lower the cutoff frequency and bandwidth will be, and there will be a relatively high gain overshoot near the cutoff frequency, which will destroy the flatness of the passband, such as image 3 shown

If you increase the gain-bandwidth product of the operational amplifier, it will consume a lot of power, and the cost is relatively high

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