Mode-mixing low-pass filter with cut-off frequency self-correction

Abstract

The invention relates to a mode-mixing low-pass filter with cut-off frequency self-correction. The mode-mixing low-pass filter with the cut-off frequency self-correction comprises a mode-mixing low-pass filter, an annular oscillator and a frequency tuning module. The mode-mixing low-pass filter is formed by cascading two active RC double second-order filers; the annular oscillator comprises a NOR gate, a first inverter, a second inverter, resistors R5 and R6, and a adjustable capacitor array Ct; and the frequency tuning module comprises a first frequency counter, a second frequency counter, a comparator and an accumulator. According to the technical scheme provided by the invention, a full-difference four-order low-pass filter based on mixed application of filter response models obtains good in-band flatness while reaching a high-stop-band attenuation degree; the annular oscillator can realize an oscillation frequency adjustable function while eliminating metastable state points of the oscillator; and the frequency tuning module, through real-time monitoring and rapid automatic correction of the cut-off frequency of the filter, greatly inhibits the influences exerted by such fluctuations as the process, voltage, temperature and the like on the frequency response accuracy of the filter.

Description

technical field [0001] The invention relates to the field of filters, in particular to a mixed-mode low-pass filter with cut-off frequency self-correction. Background technique [0002] In recent years, due to the rapid development of wireless communication systems, the scope of use has gradually expanded, making radio frequency circuits widely used in radio transmission, space satellites and geological exploration. Among them, the low-pass filter is one of the most basic baseband signal processing modules in radio frequency technology. In a wireless communication system, it is necessary to use a low-pass filter to extract useful spectrum signals, select a suitable channel, suppress interference and filter out harmonic components. Whether it can accurately and quickly complete the filtering task will have a significant impact on the performance of the entire radio frequency system. influences. However, in the traditional filter design, different filter response models have...

AI Technical Summary

Problems solved by technology

However, in the traditional filter design, different filter response models have different characteristics. The Butterworth low-pass filter with the best passband flatness has a slow attenuation in the stop band, while the Chebyshev low-pass filter that can quickly meet the attenuation requirement is low. There is a large passband ripple in the pass filter

Images