Vol. 94

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2021-09-14

Negative Group Delay Prototype Filter Based on Cascaded Second Order Stages Implemented with Sallen-Key Topology

By Miodrag Kandic and Greg E. Bridges
Progress In Electromagnetics Research B, Vol. 94, 1-18, 2021
doi:10.2528/PIERB21071209

Abstract

A Negative Group Delay (NGD) filter prototype design based on cascaded identical 2nd-order baseband stages is presented. The prototype design achieves an NGD-bandwidth product that in the upper asymptotic limit for a distributed design is a function of out-of-band gain in decibels raised to the power 3/4. This is an improvement of previous cascaded first-order designs that have an NGD-bandwidth functional dependency of out-of-band gain in decibels to the power of 1/2. The bandwidth is taken as the 3 dB amplitude response bandwidth. The corresponding NGD design upshifted to a non-zero center frequency, i.e. a Band-Stop Filter (BSF) design, is shown to be possible to implement with Sallen-Key topology, and an example is presented for a 500 MHz center frequency and a 100 MHz (20%) 3 dB bandwidth. The filter shows a 4.05 ns negative group delay with a 1.28 ns in-band variation and a 3-dB amplitude response over the bandwidth of 100 MHz, achieving an NGD-bandwidth product of 0.405. An in-band distortion metric is presented, which can be evaluated for any specified time-domain input waveform. It is shown that the bandwidth, order of filter and desired distortion for a particular input waveform are interrelated. Therefore, the proposed in-band distortion metric constitutes another trade-off quantity to be checked for any type of NGD design.

Citation


Miodrag Kandic and Greg E. Bridges, "Negative Group Delay Prototype Filter Based on Cascaded Second Order Stages Implemented with Sallen-Key Topology," Progress In Electromagnetics Research B, Vol. 94, 1-18, 2021.
doi:10.2528/PIERB21071209
http://jpier.org/PIERB/pier.php?paper=21071209

References