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Active RC Filters Without Inductors

IP.com Disclosure Number: IPCOM000078079D
Original Publication Date: 1972-Nov-01
Included in the Prior Art Database: 2005-Feb-25
Document File: 2 page(s) / 49K

Publishing Venue

IBM

Related People

Sierra, HM: AUTHOR

Abstract

An active RC filter is designed without any inductor and with only one amplifier by mathematical analysis and synthesis. The filter may be implemented as a phase-compensating, all-pass filter; or as a pulse slimming filter, such as used in the readback channel of a digital recording apparatus.

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Active RC Filters Without Inductors

An active RC filter is designed without any inductor and with only one amplifier by mathematical analysis and synthesis. The filter may be implemented as a phase-compensating, all-pass filter; or as a pulse slimming filter, such as used in the readback channel of a digital recording apparatus.

Fig. 1 shows the pole-zero configuration of a second order phase-compensating function. The transfer function for this configuration is:
H(s) = s/2/ - 2 Xi Omega(o) s + Omega(o)/2/ over s/2/ + 2 Xi Omega(o) s + Omega(o)/2/ where s = frequency

Xi = Damping factor (or ratio)

Omega(o) = -3 db cutoff frequency.

The equation is normalized by making Omega(o) = 1, realizing a configuration as in Fig. 2.

Similarly, Fig. 3 illustrates the poles and zeros of the partial transfer function for a pulse-slimming filter, defined as:

(Image Omitted)

The pole-zero configuration of Fig. 3 is very convenient for synthesis purposes. The total transfer function H(s) can be constructed by connecting in tandem, as needed, several of the pole-zero configurations shown in Fig. 3.

For example, for a compression factor K = 1.5, the filter network shown in Fig. 4 is obtained, where w = width, at the base, of the incoming

Gaussian pulse in seconds

r = resistance level in ohms.

The filters use no inductors and may be readily integrated. For the pulse- slimming filter, there is no attenuation of the incoming signal.

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