Transducing data using high frequency ferroelectric read demodulation

Abstract

Apparatus and method for transducing data from a ferroelectric data storage medium using high frequency read modulation. In accordance with some embodiments, a ferroelectric data transducer has a write electrode, a doped semiconductor layer with a source, a drain and a channel therebetween, and an insulating layer disposed between the channel and the write electrode. A write circuit applies a time varying write signal at a first frequency to the write electrode to write a corresponding sequence of data bits to an adjacent ferroelectric data storage medium. A read circuit reads the sequence of data bits from the data storage medium by applying a time varying read signal at a higher, second frequency to the write electrode and detecting changes in electrical resistance of the channel.

1 . Apparatus comprising:
 a ferroelectric data transducer comprising a write electrode, a doped semiconductor layer having a source, a drain and a channel therebetween, and an insulating layer disposed between the channel and the write electrode;   a write circuit adapted to apply a time varying write signal at a first frequency to the write electrode to write a corresponding sequence of data bits to an adjacent ferroelectric data storage medium; and   a read circuit adapted to read the sequence of data bits from the data storage medium by applying a time varying read signal at a higher, second frequency to the write electrode and detecting changes in electrical resistance of the channel.   
     
     
         2 . The apparatus of  claim 1 , in which the read circuit passes a steady state current through the channel from the source to drain during the application of the time varying read signal to the write electrode and detects the sequence of data bits responsive to changes in resistance of the channel imparted to the channel by respective electric fields from the storage medium. 
     
     
         3 . The apparatus of  claim 1 , in which the data transducer further comprises a main body having a substantially rectilinear shape, the body having an air bearing surface (ABS) on a first side of the body in facing relation to the storage medium, the data transducer mounted to a second side of the body orthogonal to the first side, the ABS supporting the write electrode in non-contacting relation to the storage medium during application of the time varying write signal. 
     
     
         4 . The apparatus of  claim 1 , in which the read circuit comprises a modulation circuit, a detector circuit and a demodulation circuit, the detector circuit incorporated into the data transducer and the modulation and demodulation circuits coupled to the data transducer. 
     
     
         5 . The apparatus of  claim 4 , in which the modulation circuit applies the time varying read signal to the write electrode, the detection circuit amplifies a channel signal responsive to application of current through the channel from the drain to the source, and the demodulation circuit applies filtering to the amplified channel signal from the detection circuit. 
     
     
         6 . The apparatus of  claim 1 , in which a detection portion of the read circuit is disposed within the data transducer. 
     
     
         7 . The apparatus of  claim 1 , further comprising said ferroelectric data storage medium, the storage medium comprising a substrate, a ferroelectric layer and an electrode layer disposed between the substrate and the ferroelectric layer, the sequence of data bits written in the form of a plurality of electric field domains polarized in respective first or second directions, respectively. 
     
     
         8 . The apparatus of  claim 7 , in which the sequence of data bits is detected responsive to the plurality of electric field domains imparting a change in electrical resistance to the channel. 
     
     
         9 . The apparatus of  claim 1 , in which the read circuit applies low pass filtering and direct current (DC) offset compensation to a read signal from the channel to demodulate the sequence of data bits written to the storage medium. 
     
     
         10 . An apparatus comprising:
 a ferroelectric data storage medium having a ferroelectric layer adapted to store data in the form of a plurality of electric field domains;   a ferroelectric data transducer adapted to be supported adjacent the medium via an air bearing surface (ABS), the data transducer comprising a channel region and a write electrode; and   a data read/write circuit adapted to write data to the medium by applying a time varying write signal to the write electrode at a first frequency, and to read data from the medium by applying a time varying read signal to the write electrode at a second, higher frequency and detecting changes in resistance of the channel region.   
     
     
         11 . The apparatus of  claim 10 , in which the data transducer further comprises a layer of semiconductor material with spaced apart doped regions to form respective source and drain regions on opposing sides of the channel region, and an insulating layer disposed between the channel region and the write electrode to provide a field effect transistor (FET) structure. 
     
     
         12 . The apparatus of  claim 10 , in which the read/write circuit passes a steady state current through the channel during the application of the time varying read signal to the write electrode and detects a sequence of data bits from the medium responsive to changes in resistance of the channel imparted to the channel by the plurality of electric field domains. 
     
     
         13 . The apparatus of  claim 10 , in which a detection portion of the read/write circuit is disposed within the data transducer. 
     
     
         14 . The apparatus of  claim 13 , in which the detection portion amplifies a signal indicative of changes in electrical resistance of the channel, and in which the read/write circuit further comprises a demodulation portion which applies low pass filtering and direct current (DC) offset compensation to the amplified signal from the detection portion. 
     
     
         15 . A method comprising:
 supporting a ferroelectric data transducer comprising a write electrode and a channel region adjacent a ferroelectric data storage medium having a ferroelectric layer;   writing data to the medium responsive to application of a time varying write signal at a first frequency to the write electrode to generate a plurality of electric field domains in the ferroelectric layer; and   reading data from the medium responsive to application of a time varying read signal at a second, higher frequency to the write electrode to generate a sequence of bits from the medium responsive to changes in electrical resistance of the channel region imparted by the plurality of electric field domains.   
     
     
         16 . The method of  claim 15 , in which the writing of data to the medium comprises applying a voltage above a selected threshold level to the write electrode to write a first data state to the medium and applying a voltage below the selected threshold level to the write electrode to write a second, different data state to the medium. 
     
     
         17 . The method of  claim 15 , in which the reading of data from the medium comprises passing a steady state current through the channel from a drain region to a source region during the application of the time varying read signal to the write electrode and detecting the sequence of data bits from said current as modulated by the time varying read signal and the plurality of electric field domains. 
     
     
         18 . The method of  claim 15 , in which the reading of data from the medium comprises obtaining a signal indicative of changes in the resistance of the channel region, amplifying the signal to generate an amplified signal, and applying low pass filtering to the amplified signal to generate a filtered signal. 
     
     
         19 . The method of  claim 15 , in which the reading of data from the medium is carried out by a read circuit, a detection portion of which being disposed within the data transducer. 
     
     
         20 . The method of  claim 15 , in which the data storage medium is characterized as a rotatable disc, in which the data transducer is supported by a moveable actuator, and in which the supporting of the data transducer comprises rotating the rotatable disc at a selected rotational velocity and positioning the data transducer adjacent the rotatable disc over a selected track using the actuator.