Datatape Incorporated

Robert D Andersen

A data signal channel, such as a record/reproduce channel of a magnetic tape recorder, is automatically calibrated by means of multiple control signals which are applied to the channel simultaneously. The disclosed technique is fast, accurate, and effective in automatically calibrating a multispeed, multichannel, magnetic tape recorder in an optimum amount of time. A channel to be calibrated is stimulated with a complex wave-form having harmonic content at frequencies where reproduce amplifier equalization controls are effective. The channel response is measured and analyzed into the desired frequency components. A set of error values are determined by calculating the difference between the measured response values and known target response values at the desired frequencies. If the set of error values are not within allowable error limits, new control values are calculated from multiple control equations. The new control values are generated and sent to adjust the equalization controls. The process is reiterated until the calculated errors are within allowable limits for each of the desired frequency components.

Autocalibration of a data signal channel through simultaneous control

Disclosed is a fast closure method for use in the calibration of a data signal channel, such as the record/reproduce channel of a magnetic tape recorder. The method results in fewer iterations of a calibration procedure which reduces the difference between a measured channel response and a target channel response to bring the channel response within acceptable response limits. According to the method, the control value is originally set at mid range and the channel response measured. If the channel response is too low, the control value is set at 75%, and if the response is too high, the control value is set at 25%. The channel response is measured again and from the last two measured channel responses a transfer slope is calculated. A projected control value is determined from this slope based on the desired response of the channel.

Fast closure method for a data signal channel

A resistor has a resistance which is precisely controlled by means of a voltage control circuit. The controlled resistor is a radiation sensitive device which is optically coupled to a source of radiation connected to the output of an operational amplifier. A control circuit applies a controllable (preferably programmable) voltage, functionally related to a desired resistance of the controlled resistor, to the input of the operational amplifier. Also connected to the input of the operational amplifier is a feedback radiation sensitive resistor, which is also optically coupled to the radiation source. Preferably, the controlled radiation sensitive resistor and the feedback radiation sensitive resistor have substantially identical resistance characteristics. A compensation circuit is electrically connected between the input and output of the operational amplifier. The compensation circuit substantially eliminates cyclical variations in the resistance of the controlled resistor caused by a response lag between the radiation source control and the radiation sensitive resistors.

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West Covina, CA, United States of America

Robert D Andersen