Dc bias servomethod and apparatus for magnetic recording heads

Claim 3

The method of claim 1 further including the step of setting the static direct current bias of the record head to a select level about which it is varied in response to the error signal.

Claim 4

The method of claim 1 in which the error signal is generated by: a. generating a reference signal of a frequency twice the fundamental frequency of the playback signal; and b. comparing the phases of the reference signal and the sensed second harmonic frequency signal of the playback signal to generate the error signal having a direct current component responsive to the relative phase relationship of the reference signal frequency and second harmonic signal frequency.

Claim 5

The method of claim 3 in which the reference signal is generated by: a. sensing the fundamental frequency of the playback signal; and b. doubling the fundamental frequency to provide the reference signal.

Claim 6

The method of claim 1 further including the steps of: a. energizing a record head of the record head assembly with a record signal of a selected frequency to effect recording the record signal on a magnetic record medium; and b. immediately reproducing the record signal from the magnetic record medium to provide the playback signal.

Claim 7

The method of claim 5 for controlling the direct current bias on each of a plurality of record heads forming the record head assembly in which one of the record heads is energized to effect recording of the record signal, and the direct current bias on all of the record heads of the record assembly is varied in response to the error signal.

Claim 8

A direct current bias servosystem for the magnetic head assembly of a magnetic recording system comprising in combination: means for generating a signal of a select frequency and applying said signal to the energizing coil of a record head for recording on a magnetic medium; reproducing means for reproducing the recorded signal to provide a playback signal from said medium; means for detecting the content of a second harmonic frequency signal of the playback signal; means for comparing the detected second harmonic frequency signal to a reference signal to provide a direct current error signal representative of the content of the detected second harmonic frequency signal; and means for varyinG the degree of direct current bias of the record head responsive to the direct current error signal.

Claim 9

A direct current bias servosystem for the magnetic head assembly of a magnetic recording system comprising in combination: means for generating a signal of a select frequency and applying said signal to the energizing coil of a record head for recording on a magnetic medium; reproducing means for reproducing the recorded signal to provide a playback signal from said medium; means for detecting the content of a second harmonic frequency signal of the playback signal; means for comparing the detected second harmonic frequency signal to a reference signal to provide a direct current error signal representative of the content of the detected second harmonic frequency signal; and means for varyinG the degree of direct current bias of the record head responsive to the direct current error signal.

Claim 10

The system of claim 7 in which the means for detecting the second harmonic content includes a filter designed to pass the second harmonic frequency component of the playback signal; and further comprising a frequency doubler means receiving the playback signal and providing the reference signal at twice the fundamental frequency of the playback signal; and in which the comparator means provides a direct current error signal of a polarity representative of the phase relationship of the reference signal and the component and having an amplitude representative of the content of the second harmonic component.

Claim 11

The system of claim 8 further including means for setting the static direct current bias level of said record head.

Claim 12

The system of Claim 9 in which the head assembly includes a plurality of individual heads and further including means for varying the degree of direct current bias on a multiple of said heads responsive to said error signal.