A multitrack multiplexed fixed recording head

Abstract

As the demand for high data rate (up to 1 GUS) , high density (down to 1 pm2hit) tape recorder Increases, the main investigation trend is an improvement of the well known helical scan concept. The disadvantages of this technology are also well known : sophisticated mechanics, head to tape contact and wear problems. We have investigated a new -roach based on fixed inductive write and magnetwptic readout components. The recader mechanics Is then made much more simple, and the complexity is turned towards the integrated magnetic components (they have to record and reproduce hundreds of tracks In parallel).Due to the very large number of parallel tracks needed. the write head cannot be made of a stack of individual integrated gaps (large head wiring surface, magnetic Interferences between adjacent poles, unmanageable number of electrical connections...). It has then been chosen to multiplex the gaps, everyone being at the crossing of a conducting column and row. as shown in figure I. The multiplexed writing is made possible thanks to the highly non linear behavior of the magnetic tape. As long as the sum of the cdumn (used for the gap selection) and row (used for the data presentation) currents does not reach the crltical value (enough to produce a fdd in the gap at least equal to the coercive field of the tape), the corresponding gap does not write on the media. Figure 2 gives a view of an isolated gap into the matrix head structure. This head is made ot an hybrid technology, mixture of conventional ferrite processing (for the bottom part of the structure), and thin film (for the magnetic poles in contact with the tape). As the gaps are located on a flat surface (a few mrnz), a planar technology has been developed with the gaps spead out on the surface of the wafer. v A two beam interference method, using a monochromatic light has been used to characterize the contact with the best possible resolution, the tape being static or running. The interference pattern takes place between the tape and a dummy glass head where the protuberant magnetic pde shape of the multitrack head has been reproduced. It allows : -the assessment of the temporal and spatial contact homogeneity 0-7803-0637 -6/92 $3.00 @ 1992 IEEE -the optimization of the pressure pad nature and position -the dust behavior visualization -the measurement of the effedive spacing -the lnvsstigstlon d the W d n g &ation wnh thO appplied 7 On the pad. Technoloavit has been shown that a temporal and spatial h o~e o o u r doso oompct can be achieved betweem a moving magnetk t a p and a largeactive area head. l h e h m d t o t a p e~s p a d n g is strongly correlated to the tape roughness (measured by atomic force microscopy) and does not vary slgniflcantly with the applied pressure (typically around 2.104 Pa). SLMalSignal recorded with the matrlx head has been compared to a n a l recorded with a conventional MIG single track head. The output levels, measured with a common helical scan readout system, are canparable. as shown in Figure 3. ConclusionA new technology o...