Delay and optimum amplitude equalizers for a readback circuit

DETAILED DESCRIPTION The above mentioned limitations of equalizer circuits, made in accordance with the forced amplitude spectrum output shaping, are overcome by the provision of a new and improved readback circuit.
This readback circuit includes a transducer circuit for detecting data recorded on the magnetic medium and an optimum equalizer circuit connected to the output of the transducer circuit.
The optimum equalizer circuit produces a data representative signal having symmetrical, equal amplitude pulses of limited pulse widths and a signal to noise ratio greater than the signal to noise ratio of the input read signal produced by the transducer circuit.
The transducer circuit operates in a conventional manner to detect the magnetic transitions recorded on the storage medium and to produce a voltage signal of varying amplitudes.
However, since the transducer typically has a nonlinear phase delay which will produce a read signal of asymmetrical shape, a capacitor-conductor lattice network, which is a well known circuit for a delay equalizer, is provided to compensate for the nonlinear phase delay.
The optimum equalizer circuit is made in accordance to a final transfer function produced as a result of a mathematical convolution of two frequency domain transfer functions.
The first transfer function is based on the theory of a matched filter.
If the optimum equalizer embodied only matched filter theory, such equalizer would operate to change the read signal produced by the transducer circuit into a signal which has pulses having maximum signal to noise ratio.
The first transfer function is specifically derived with inputs comprising a known input data signal, which in this case is assumed to be pulses having Lorentzian waveshapes, and a colored noise input signal.
The second transfer function is based on the theory of a window function which in the preferred embodiment of the optimum equalizer circuit is a Papoulis window function.
If the optimum equalizer embodied only window function theory, such equalizer would operate to produce a signal with limited pulse widths