M-derived filter

M-derived filter

Force-System Resultants and Equilibrium

Published in Richard C. Dorf, The Engineering Handbook, 2018

The advantage of the m-derived filter is that it gives rise to infinite attenuation at a selectable frequency, ω0, just beyond cutoff, ωC. This singularity gives rise to a more rapid attenuation in the stopband than can be obtained using constant- k filters. Equation 111.18 relates the cutoff frequency to the infinite attenuation frequency. m=1-ωC2ω∞2

VHF high-power tunable low-pass filter based on nested coupled helical inductor

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Journal Information

Published in International Journal of Electronics, 2021

Zhengwei Huang, Yong Cheng, Yuanjian Liu

The circuit principle of the proposed VHF tunable low-pass filter based on a set of nested coupled spiral inductors in section 2.1 is shown in Figure 1(c), which includes a set of nested coupled helical inductors and a variable capacitor. A set of nested coupled helical inductors can be considered as two coupling inductors of the homonymous terminal. According to the decoupling theory of coupled inductance T-type circuit (William et al., 2011), the proposed circuit can be equivalent to a third-order low-pass filter with a transmission zero, as shown in Figure 1(d), in which M represents the mutual inductance of L1 and L2. By changing the value of capacitor Cp, the cut-off frequency and transmission zero of the low-pass filter can be adjusted. According to the design theory of m-derived filter based on the image parameter method (David, 2011), the m-derived filter is composed of m-derived T-shaped low-pass filter sections to provide the desired cut-off frequency and attenuation characteristics. The following equation can be obtained:

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Force-System Resultants and Equilibrium

VHF high-power tunable low-pass filter based on nested coupled helical inductor