A Magnetically Scanned Magnetic Tape Transducer

A new digital magnetic tape transducer intended to provide megabit per second data transfer speeds with moderate tape speed is described. This magnetic tape transducer contains no moving parts, but records on the tape along transverse tracks. Sweep of the effective or operative area of the transducer across the tape is accomplished by selectively controlling the permeability of one of the magnetic members. A large portion of this transducer is fabricated from thin magnetic films deposited upon glass substrates. The performance of the transducer is determined to a large extent by the magnetic switching characteristics of one of these thin films. The magnetic properties required of these films are derived in terms of the desired frequency response. The impulse response is calculated partially taking into account the nonlinearity of the tape but neglecting demagnetization effects. As an aid to making design choices, the frequency response of the transducer is computed from the impulse response. The magnetic parameters, the dimensions of the transducer and tape, and the speed of the sweep across the tape are chosen to obtain a frequency response of about 4 Mc/s. The experimentally obserrved pulse response using prerecorded tape compares favorably with the predicted impulse response. However, considerable playback noise which is probably associated with the thin magnetic films has been observed. It appears that an extensive material development would be required before this transducer could be utilized.