FIGURE OF MERIT
An important consideration for an equalizer design involves the change in the signal to noise ratio (SNR) introduced by the equalizer. Here the SNR is defined as the peak signal to the rms noise voltage. The figure of merit (FM) of the filter is the ratio of the input to the output SNR expressed in dB. The computation was done numerically with the input signal being Lorentz, the output signal being Van der Maas and the noise power spectral density was taken directly from a disc. The FM as a function of the ratio TM/PW50 is shown in Fig. 3 where TM is onehalf the distance between the zero slope points on the Van der Maas (VDM) time function.
Fig. 3. Figure of merit
FILTER DESIGN EXAMPLE
An equalizer to remove intersymbol interference in the time derivative of the slimmed output is now designed to illustrate the ideas discussed thus far. The input signal has a PW50 of about 110 ns and the output VDM frequency function has a cutoff frequency of 12.36 MHz. Initially, the pole locations of the filter were adjusted to equalize the group delay to 10 MHz. This resulted in a time function error (deviation from a constant) of 1.5 ns. Then the zeros were adjusted to minimize the magnitude error. A SPICE analysis of the equalizer showing the input and the output are shown in Fig. 4.
Fig. 4. Spice simulation of example design
CONCLUSIONS
During the process of developing this design approach, it became clear that a more appropriate approach would be to specify the objective function in the time domain. This would completely circumvent the need for having precise information about the group delay, for example. Only a modest change is required to change the procedure described here into a time domain design.

ACKNOWLEDGMENTS
Special thanks go to Mr. Don Huber and Dr. Maung Gyi for their significant contributions, and to Mr. Frank Sordello for his support.
REFERENCES
[1] H.M. Sierra, "Increased Magnetic Recording Readback Resolution by Means of a Linear Passive Network", IBM Journal, Jan. 1963.
[2] D.E. Vakman, Sophisticated Signals and the Uncertainly Principle in Radar, SpringerVerlag New York Inc., 1968.
[3] J.C. Mallinson and C.W. Steele, 'Theory of Linear Superposition in Tape Recording', IEEE Transactions on Magnetics, Vol. MAG5, No. 4, Dec. 1969.
[4] B.K. Middleton and P.L. Wisley, 'Pulse Superposition and High Density Recording', IEEE Transactions On Magnetics, Vol. MAG14, No. 5, Sept. 1978.
[5] PROSE, Inc., Palos Verdes Estates, CA 90274.
[6] T. Fujisawa, 'Realizability Theorem for Midseries or Midshunt Lowpass Ladders Without Mutual Induction', IRE TransactionCircuit Theory, Dec. 1955.
[7] A.V. Oppenheim and R.W. Schafer, Digital Signal Processing, Prentice Hall, Inc., 1975, p 21.
[8] Korn and Korn, Malhemafical Handbook for Scientist and Engineers, McGraw Hill, 1968, pp 134136.
[9] W.C. Percival, Thermionic Valve Circuits, British Patent 460562, July 1935.
[10] E.L. Ginrton, W.A. Hewlett, J.H. Jasberg and J.D. Noe, Distributed Amplification, Proc IRE, vol 36, pp 956969, Aug. 1948.
[11] P.H. Rodgers and L.H. Enloe, Transistor Distributed Amplifier, U.S Signal Corps Contract DA36039 SC75021, March 1958.
[12] J.M. Pettit and M.M. McWhorter, Electronic Amplifier Circuits, McGraw Hill, 1961, pp 147163.
[13] G.C. Temes and J.W. LaPatra, Introduction to Circuit Synthesis and Design, McGraw Hill, 1977, pp 157159.
Manuscript received March 23, 1981. Paper 378 presented at the 1981 INTERMAG Conference, Grenoble, France, May 1215. The authors are with the Recording Technology Center, Memorex Corporation, Santa Clara, California 95052.
This Pulse Slimming is another increased productivity example do to using Calculus (level) programming.
visit http://fortranCalculus.info for MatchnFreq app.
to reproduce the results discussed in this article.
