A Mixed-Mode Low-Pass Filter with Self-Correcting Cutoff Frequency

Abstract

The invention relates to a mixed-mode low-pass filter with cut-off frequency self-correction, comprising a mixed-mode low-pass filter, a ring oscillator and a frequency tuning module; the mixed-mode low-pass filter consists of a two-stage active RC biquad filter Cascade composition; the ring oscillator includes a NOR gate, the first and second inverters, resistors R5, R6 and an adjustable capacitor array Ct, and the frequency tuning module includes the first and second frequency counters, a comparator and an accumulator. In the above technical solution, the fully differential fourth-order low-pass filter based on the hybrid filter response model can achieve good in-band flatness while achieving high stop-band attenuation; the ring oscillator can eliminate the vibration of the metastable point of the oscillator. At the same time, the adjustable oscillation frequency function is realized; the frequency tuning module monitors and quickly automatically corrects the filter cut-off frequency in real time, and greatly suppresses the influence of fluctuations in process, voltage, and temperature on the accuracy of the filter's frequency response.

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

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