Abstract: A hard disk drive system (10) includes a read head (21) for reading information from a rotating magnetic disk (12). The read head outputs a servo burst signal in response to servo information (59) on the disk. An analog-to-digital converter (33) is provided to oversample the servo burst signal during each of a plurality of successive time intervals, in order to obtain a plurality of samples for each such time interval. An accumulator (74) is provided to sum the samples for each time interval, in order to obtain for each time interval a respective accumulation value that represents an integration of the burst signal for that time interval. A filtering circuit (86) is provided to determine a burst value for the servo burst signal, by applying a filtering function to a set of the accumulation values. The filtering function may involve determining a median accumulation value from the set of accumulation values, or determining a mean of the accumulation values in the set.

Abstract: A discrete time servo demodulation technique incorporated within a sampled amplitude read channel to demodulate embedded servo field information stored on a magnetic medium. The servo field information is transduced by a read head into an analog signal, and converted to a sequence of sample values in the read channel. The demodulation technique is responsive to the sample values and includes a discrete time peak detector for detecting servo data, and a discrete time servo burst amplitude detector for measuring the amplitude of servo bursts. Peaks are detected in the analog read signal by sensing a change of slope from the sequence of sample values. The peaks are qualified by polarity in that a peak is detected only if its polarity is opposite in sign from the previous peak. The servo burst amplitudes are measured by interpolating, rectifying, and accumulating the sequence of sample values corresponding to the servo bursts.

Abstract: There is provided in an embodiment according the present invention, a signal processing device comprising detecting means for detecting a predetermined frequency component of the input signal; modulating means for modulating the input signal and supplying the modulated signal to a recording device; and switching means for supplying, in a first state, the output of the modulating means to the detecting means, and for supplying, in a second state, a reproduced signal to the detecting means from a reproducing device. With the aforementioned construction, the detection circuit that detects a predetermined frequency component included in the modulated digital signal can be used during recording as well as during signal reproduction, which greatly contributes to reducing the size and cost of the recording/reproducing device.

Abstract: Disclosed is a method of demodulating a position signal in a magnetic disk device for reading servo burst signals, which have been recorded in a servo area of a magnetic disk, by a head, and outputting a position signal, which indicates a deviation from a reference position on a track, using the servo burst signals that have been read.

Abstract: A data recording device such as a hard disk apparatus has an orthogonal coding circuit and a modulation circuit. The orthogonal coding circuit encodes recording data to be recorded to adjacent two tracks as two orthogonal code streams which are included in an Hadamard matrix. The modulation circuit outputs recording signals, which are obtained by modulating the code streams using the NRZI system, to a magnetic head. Reproduction signals read out from a magnetic disk by the magnetic head are decoded as recording data based upon given decoding rules according to the two code streams.

Abstract: The device is to be used with a parallel architecture partial response maximum likelihood (PRML) reading apparatus comprising a variable-gain input amplifier, a low-pass analog filter, a transversal continuous-time analog filter and two distinct and parallel processing channels interposed between the transversal analog filter and an RLL-NRZ decoder. The two processing channels comprise respective analog-digital converters and respective Viterbi detectors and operate according to sampling sequences that alternate with one another. The device for processing the servo signals comprises a rectifier connected to the outputs of the analog-digital converters and an integrator.

Abstract: A pulse-width modulation signal generator having a pre-phase converter which includes N pre-delay circuits connected in cascade, and N main phase converters each of which includes M main delay circuits, where N and M are natural numbers greater than one, and N>M. The output of each of the N pre-phase circuits is supplied to one of the N main phase converters to generate phase converted clock signals used for generating a pulse-width modulation signal.

Abstract: A Viterbi decoding circuit for decoding an input signal is provided. The circuit contains a detector, a first converter, a Viterbi decoder, a second converter, and a selector. The input signal is grouped into a current and subsequent input signal group. The detector detects negative peak data values and positive peak data values from the current input signal group. The first converter converts the positive and negative peak data in a reverse direction to produce reverse positive and negative peak data, respectively. The Viterbi-decoder decodes the reverse positive and negative peak data with respect to a predetermined number of initial states and generates current reverse decoded data groups which respectively correspond to a plurality of channels and respectively correspond to the initial states. In addition, the Viterbi decoder generates a control signal based on a state of initial decoded data corresponding to the subsequent input signal group.

Abstract: A demodulator for a pulse width modulated signal comprises a counter arranged to count in one direction when the PWM signal is "high" and in the opposite direction when the PWM signal is "low" to arrive at a count representative of a duty cycle. As a result, a value representative of the duty ratio of the PWM signal can be obtained from the up/down counter. In a further embodiment, the up/down counter is clocked by the output of a frequency multiplier, the output of the frequency multiplier having a frequency determined by the pulse width modulated signal frequency multiplied by a predetermined factor. The value of the duty ratio of the PWM signal can then be found regardless of the frequency of the PWM signal.

Abstract: A magnetic disk drive data storage disk defines recording tracks divided into data sectors by narrow servo spokes. A data sector lying between servo spokes is recorded with user data encoded in accordance with a code having a predetermined distance and user data code rate. Each servo spoke of the recording area has at least one servo information field encoded in a wide bi-phase code pattern. The disk drive further includes a synchronous sampling data detection channel having a data transducer head positioned by a servo-controlled actuator over the recording track, a preamplifier for receiving electrical analog signals magnetically induced by the data transducer head from flux transitions present in at least the servo information field, a digital sampler for synchronously sampling the electrical analog signals to produce digital samples, and wide bi-phase decoding circuitry coupled to receive digital samples from the synchronous sampling data detection channel for decoding the wide bi-phase code pattern.

Abstract: A magnetic data recording apparatus magnetically records various items of data on a film in accordance with a feed of the film by a PPM Pulse Position Modulation (PPM) recording method. The apparatus includes a PPM signal converting circuit for converting the data to be recorded into a PPM signal and outputting the PPM signal, a magnetic head and a head driving circuit for driving the magnetic head on the PPM signal outputted from the PPM signal converting circuit. The apparatus further includes a data quantity calculating circuit for calculating a quantity of the data to be recorded during a feed of the film. The PPM signal converting circuit determines a change-of-signal position of the PPM signal within one period on the data quantity calculated by the data quantity calculating circuit.

Abstract: Information is divided into first blocks each having m bits, and n bit or bits in each of S different states are added to a head of each of the first blocks to change the first block into S second blocks each having m+n bits, where m and n denote predetermined natural numbers and S denotes a predetermined natural number equal to or smaller than 2.sup.n. Each of the S second blocks is pre-coded into S pre-coded information blocks respectively. One of the S pre-coded information blocks is selected as a modulation-resultant information signal in response to error signals related to the S pre-coded information blocks respectively. The modulation-resultant information signal has q different notch frequencies. The S pre-coded information blocks are converted into S amplitude signals representing amplitude values respectively. A set of q first waveform signals and a set of q second waveform signals are generated. The q first waveform signals represent waveforms related to the q notch frequencies respectively.

Abstract: A storage system for storing information on a magnetic media is embodied within a conversion device. The system is operable to store data within a bit cell by receiving data from a controller board (14), which data is generated by a Central Processing Unit (CPU) (52). This data is convened from an ordinary Modified Frequency Modulation (MFM) format received on a bus (32) and then convened to a Super High Density (SHD) data format. In the SHD format, a counter is provided for counting down from an initial starting time corresponding to a reference pulse (102) to an end count value corresponding to the value of a data word. The time between the reference pulse and the end of count value constitutes the length of time from the beginning of the bit cell to the position in the bit cell at which a data pulse is recorded. During a decode operation, i.e.

Abstract: In a magnetic recording reproducing apparatus, a detecting and decoding circuit comprising:a first integrator having an input for receiving a pulse position modulated (PPM) encoded signal reproduced from magnetic media, and having an output;a second integrator having an input coupled to said output of said first integrator and having an output;a first comparator having a noninverting input connected to the output of said first comparator, an inverting input connected to ground, and an output;a reset pulse circuit having an input connected to the output of said first comparator and an output connected to a reset terminal of said second integrator;a second comparator having a noninverting input connected to the output of said second integrator, an inverting input connected to ground, and an output; anda D flip-flop, having a data input connected to the output of said second comparator, a clock input connected to the output of said reset pulse circuit, and an output which outputs a decoded data signal of said re

Abstract: A playback/recording modulating-demodulating device, having a voltage-controlled oscillator (VCO), a voltage-current inverter (VCI), a band-pass filter, an amplitude limiter, and a phase-locked loop. In playback mode, the playback input signal is applied to the band-pass filter, the phase-locked loop is activated, and the VCI is set to produce a reference signal which controls the band-pass filter to tune the playback input signal. The tuned playback signal is applied to the amplitude limiter which produces an amplitude-limited signal which is applied to the phase-locked loop to produce a demodulated playback output signal. In record mode, the phase-locked loop is deactivated, the VCO produces a signal having a frequency which varies according to the voltage of a record input signal, and the VCI outputs a current control signal, having an output current related to the voltage of the record input signal, which is applied to the band-pass filter to control its bandwidth.

Abstract: An apparatus and method for demodulating an amplitude modulated read signal generated by a magnetic head of a hard disk drive. The apparatus includes a pair of serially connected track and hold circuits that receive the read signal. The track or hold state of each circuit is controlled by a phase lock loop circuit which also receives the read signal. The first track and hold circuit initially tracks the read signal to a peak value. The circuit then switches to a hold state and provides a constant output signal that corresponds to the peak voltage of the read signal. While the first track and hold circuit is in the hold state, the second track and hold circuit is in a tracking state. The second track and hold circuit tracks the output of the first circuit. Because the output of the first circuit is a constant value, the second circuit also provides a constant output signal in the tracking state.

Abstract: A disk apparatus for reproducing pulse width modulation (PWM) data from a disk is disclosed. A first sync pattern detector compares data DTLE with a first sync pattern. A second sync pattern detector compares data DTTE with a second sync pattern. A first signal generator stops the detecting operation of the first detector when the first detector has detected the first sync pattern from the data DTLE. A second signal generator stops the detecting operation of the second detector when the second detector has detected the second sync pattern from the data DTTE. A first time check circuit restarts the detecting operation of the first detector when the first sync pattern has been detected first and the second sync pattern is not detected within a predetermined period of time. A second time check circuit restarts the detecting operation of the second detector when the second sync pattern has been detected first and the first sync pattern is not detected within a predetermined period of time.

Abstract: A camera comprises a photographic information output circuit section, a CPU, a PPM signal conversion circuit section, a drive section for a plurality of magnetic heads, and a film feeding section. The CPU converts several parallel data items which are output from the photographic information output circuit section into a single serial data item and outputs it to the PPM signal conversion circuit section provided separately from the CPU. The PPM signal conversion circuit section converts this single serial data item into several PPM signals, and then supplies the PPM signals to the magnetic head drive section.

Abstract: A method and apparatus for recording and reading magnetic tape that contains audio signals and data that is related to the audio signals. In the preferred embodiment, the audio signals are music, and the related data are lyrics to the music displayed in real time to the music as it is being played. The lyrics are modulated onto an ultrasonic carrier signal and mixed with the audio signal on one track of the tape. The tape may be played on a conventional tape recorder without having interference from the recorded data at ultrasonic frequencies. In a suitably equipped tape player, the mixed signal is read and filtered to generate a high pass filtered signal and a bandpass filtered signal. The bandpass filtered signal filters out frequencies outside the range of human hearing to generate an audio signal. The high pass filtered signal is demodulated by the carrier frequency to reconstruct the lyrics.

Abstract: A signal processing system comprises inputs for an analog audio signal and a digital data signal. The digital data signal is modulated to an analog data signal in an inaudible frequency band. Filters are used to ensure that the audio signal is restricted to audible frequencies and that the analog data signal is restricted to inaudible frequencies. The two analog signals are then combined into a composite analog signal. The composite signal is stored on a medium such as a compact disc. Filters are used to extract and separate the two analog signals from the composite signal stored on the medium. The analog data signal is demodulated to retrieve the original digital data signal.

Abstract: During a write revolution of a storage medium, a transition is written on the storage medium while servoing on another transition previously recorded on the storage medium. During that write revolution, a position error signal corresponding to the position error of the transducer relative to the previously recorded transition is determined. That position error signal is then stored, during the write revolution, to be used in computing a reference track value associated with the transition being written to correct for the position error. Additionally, a product servo-pattern is written, which includes an embodying of the position error therein.

Abstract: A modulation circuit for a digital signal recorder includes first and second high-pass filters for removing the direct current component in the output of the coded I and Q channels and for converting a 4-levels signal into a 7-levels signal. Additionally, a carrier signal generator for generating a carrier signal, a modulator for performing quadrature amplitude and phase modulations on the outputs of first and second high-pass filters using the carrier signal, a pilot signal generator for generating a pilot signal and combining the pilot signal with the output of modulator and for outputting the result for transmission or recording are also provided.

Abstract: A multiplexed data stream is formed by encoding a first input signal at a variable bit rate to form a first encoded data signal which is temporarily stored in a first storage device, encoding a second input signal at a constant bit rate to form a second encoded data signal which is temporarily stored in a second storage device, and using a multiplexing circuit to multiplex the first and second encoded data signals respectively stored in the first and second storage devices to form the desired multiplexed data stream. Transfer of the first encoded data signal from the first storage device to the multiplexing circuit is controlled on the basis of a quantity of the first encoded data signal that is present in the first storage device. When none of the first encoded data signal is present in the first storage device, transfer of the first encoded data signal to the multiplexing circuit is temporarily halted.

Abstract: An improved helical scan type video taperecorder for reproducing a high quality video signal with no distortions, and thereby eliminating a sag distortion is provided by applying a continuous reproduced video signal prepared by inserting FM signals reproduced by a pair of rotary heads into no-signal field intervals of a FM signal reproduced by a single rotary head, only the FM signal from which is used for displaying, to a clamp circuit.

Abstract: A camera includes a photographic information output circuit section, a CPU, a PPM signal conversion circuit section, a drive section for a plurality of magnetic heads, and a film feeding section. The CPU converts several parallel data items which are output from the photographic information output circuit section into a single serial data item and outputs it to the PPM signal conversion circuit section, which then converts this single serial data item thus output from the CPU into several PPM signals, and then the PPM signal conversion circuit section supplies the PPM signals to the magnetic head drive section.

Abstract: A demodulator circuit receives an input signal read from a track of a magnetic medium and generates a control signal to maintain alignment of a read-write head with the track. The demodulator circuit includes at least one transistor. The at least one transistor has an electrode switchable between first and second voltage sources. The electrode is coupled to the second voltage source to block processing of the input signal. The electrode is coupled to the first voltage source to process the input signal. The at least one transistor provides an effective resistance when coupled to the first voltage source that is dependent on the voltage level of the first voltage source. The at least one transistor half-wave rectifies the input signal when the electrode is coupled to the first voltage source.

Abstract: A recording and/or reproducing apparatus divides long bit-length data into upper bit data and lower bit data, and records both data along with discriminating data in a manner that the upper-bit data and the lower-bit data are allocated and recorded, on an alternating basis, onto the scan start side areas and the scan end side areas of a plurality of pairs of recording tracks, in order to obtain more high-quality digital audio signal to be recorded and reproduced.

Abstract: A digital signal magnetic recording/reproducing apparatus subjects a digital signal to a digital amplitude phase shift keying and records and reproduces the modulated signal thus obtained on a magnetic recording medium. Use of the digital amplitude phase shift keying technique makes it possible to remove the direct-current component in the recording signals, and to improve the utilization efficiency of the recording frequency band, thus making high density recording possible. In addition, since a plurality of modulated signals are frequency-multiplexed and recorded, almost the entire frequency band recordable on a magnetic recording medium can be utilized, resulting in an increase in recording density. Further in addition, a pilot signal produced by frequency-converting a carrier is frequency-multiplexed with a modulated signal and recorded and reproduced and the carrier is reproduced from the reproduced pilot signal, so that a redundant part for reproducing the carrier is not necessary.

Abstract: A video tape recorder for recording and/or reproducing a stereo frequency-modulated audio signal by a pair of carrier signals of an indispensable first carrier signal and an additional second carrier signal is comprised of a circuit for demodulating the second carrier signal to provide a demodulated output, and a comparator for comparing an amplitude of the demodulated output with a predetermined value. When the amplitude of the demodulated output is below the predetermined value, it is determined that the second carrier signal exists.

Abstract: A positive direction current source is connected to a magnetic head coil via a multiplier and a switching device, and a negative direction current source is connected to the magnetic head coil via the switching device. The output current of the positive direction current source is controlled to a level appropriate for generating a magnetic field forming a magnet-optical recording mark based on the amplitude of an information signal by the multiplier. The switching device is turned on/off by a carrier signal. As a result, a magnetic head driving signal can be obtained having the positive direction current value modulated based on the amplitude of the information signal.

Abstract: A recorder system provides simultaneous data information and track following servo information from a buried servo layer disposed under a data recording layer in a magnetic medium, using the same transducer for simultaneously reading the servo and data information while writing data. The signals representing data are shaped to provide a wide gap around zero frequency (DC) for inclusion of servo information in the gap, and as a result, segregated data and servo information is read by the recorder through use of filtering techniques.

Abstract: In a demodulation circuit for demodulating a pulse position modulation (PPM) signal, and a camera having the demodulation circuit, a change in PPM signal is counted by an up/down counter which is switched between count-up and count-down modes every time the PPM signal changes. When a carry signal is output from the counter, the carry signal is latched, and the PPM signal is demodulated into binary data on the basis of the presence/absence of the carry signal in the count-up mode and the carry signal in the count-down mode.

Abstract: In transmission or recording of a digital signal by means of digital amplitude and phase modulation, particularly recording into and reproducing the same from the a magnetic recording medium, a digital amplitude/phase modulated signal to be demodulated is commonly affected by the non-linear amplitude characteristics and the effects of unwanted jitter and envelope variation. As the result, the error rate of decoded data will be increased. For compensation, the Viterbi decoding technique is employed with the use of a weighted distance value calculated by multiplying an Euclidean distance between the signal point of a reproduction signal and the datum point of each code by a positive weighting factor which is determined smaller when the code datum point is located further from the origin point of a coordinate system. Accordingly, the weighted distance of each reproduction signal point from its corresponding datum point can approximately be uniform thus ensuring less error decoding in general.

Abstract: An apparatus for demodulating and decoding a multi-level amplitude modulation signal used to convey digital data, such as a QAM signal, having amplitude modulated carrier components differing in phase. The apparatus derives demodulated data values from that signal, and derives from average values of sets of these data values a set of compensated reference point data respectively corresponding to signal reference points of the multi-level modulation signal which are expressible as a symbol constellation in the I-Q plane. The compensated reference point data are used to obtain correct digital code values from the demodulated data, even if there is considerable distortion of the multi-level amplitude modulated signal, as is the case for such a signal when recorded and reproduced from a magnetic recording medium.

Abstract: The present invention relates to a method and device for recording the low frequency band of an audio signal on an amplitude modulated carrier above the highest frequency component of the audio signal. The carrier frequency is at least 19 kHz and is recorded at an adequate level above the noise floor typically about 10 to 30 dB below peak level. The audio signal with the low frequency band optionally attenuated or omitted is directly recorded in the normal audio region on the same track with the corresponding AM carrier. During playback the amplitude modulated carrier is recovered using a highpass or bandpass filter, demodulated and the low frequency signals mixed with the audio. When applied to audio tape reproduction, the present invention improves bass response as compared to direct recording alone. High quality low noise tape and narrow bandwidth of the AM signal allows audio reproduction with high signal to noise ratio.

Abstract: A slew rate converter is provided in a video signal recording circuit for limiting a signal having a high frequency and a high amplitude so as to avoid an over-modulation when the signal is reproduced. The high frequency and high amplitude component exceeding a pre-determined amplitude is detected and applied to the slew rate converter for reducing its slew rate so that the signal component having the high frequency and high amplitude is suppressed.

Abstract: A demodulator system demodulates position information signals provided by a transducer in response to position information. The position information is read from a quadrature field and a normal field on a disk in a data storage system. A rectifier rectifies the position information signals to provide rectified position signals. An integrating capacitor integrates the rectified position signals to produce position error signals representative of trasducer position.

Abstract: An RF modulator comprising an FM modulator supplied with an audio signal, and AM modulator supplied with the FM modulator output and a video signal, an oscillator for generating a sound subcarrier signal, and an oscillator for generating a main carrier signal. Each of the oscillators consists of a VCO with a PLL circuit, and the entire components are composed of a single IC chip so as to be formed into a compact miniature structure. A modified RF modulator includes a PLL circuit for varying the oscillation frequency of a VCO by a variable frequency divider, and a modulation circuit supplied with a modulating signal and the oscillation output of the VCO. The division ratio (integer) of the variable frequency divider is continuously varied, and the reference frequency of a reference oscillator is set to be less than a predetermined channel interval frequency, thereby reducing the frequency error in the modulated signal output.

Abstract: An apparatus for producing a frequency-multiplex signal on the basis of a plurality of signals so as to record the produced frequency-multiplex signal on a recording medium, second signal having a frequency lower than that of the first signal. The apparatus includes a multiplying circuit for multiplying the frequency of the second signal by 2 and an amplitude-modulator for multiplying the first signal by the output signal of the multiplying circuit. Also included in the apparatus is an adder for adding the second signal to the output signal of the amplitude-modulator, the output signal of the adder being recorded as the frequency-multiplexing signal on the recording medium.

Abstract: A digital signal magnetic recording/reproducing apparatus converts a digital signal into a multi-value digital signal, followed by recording/reproducing the quadrature biphase modulated multi-value quadrature amplitude modulated signal. By using a multi-value quadrature amplitude modulation, a direct current component in the recorded signal can be eliminated, and the utilization efficiency of the recording frequency band of the digital signal magnetic recording/reproducing apparatus can be improved. Also, with respect to the amplitude non-linear characteristic which occurs in the magnetic recording/reproducing process, by providing a compensating circuit during the mapping before recording or after reproducing and demodulating, the deterioration of the S/N ratio of the reproduced and demodulated signal can be reduced to decrease the errors in the decoded data.

Abstract: A data signal is modulated by an exclusive-OR operation applied to a carrier signal and a data signal to be recorded. Demodulation is similarly performed by an exclusive-OR operation applied to the carrier signal and signal indicative of read data. This makes it possible to construct the modulating/demodulating circuit in the form of a digital circuit.

Abstract: An optical disk is provided with a dedicated track area for recording optical conditions for read and write operations. The apparatus includes different types of demodulating circuits for allowing any type of demodulation to be adopted. After parameters, recorded on the dedicatad track area through phase encoding demodulation, are read out, the demodulating circuit compatible with the modulation type adopted in recording the data is selected for demodulation of the data.

Abstract: A video system includes a VCR coupled to the output of a summation circuit that has two inputs. The first input is supplied from an active splitter and the second from a UHF modulator/upconverter which has its input connected to the active splitter through a decoder/converter. The output of the summation circuit is coupled through a passive splitter to the VCR and the VCR is connected to the TV receiver in normal fashion. The arrangement permits full use of the VCR capabilities.

Abstract: An amplitude modulator having first and second differential amplifiers which are commonly supplied with an amplitude modulated carrier signal and a third differential amplifier which is connected to the emitter current path of the first differential amplifier, wherein the third differential amplifier is supplied with a video signal for modulation through a limiter and a current value of a current source connected to the third differential amplifier is adjusted to thereby adjust a modulation degree of an amplitude modulated video signal derived from the first and second differential amplifiers so that a white level of an input video signal can be positively prevented from being deteriorated.

Abstract: An information signal recording medium has a spiral track on which an information signal is recorded. The information signal includes picture element data which correspond to one field, and is time-sequentially recorded on the spiral track in terms of the picture element data which correspond to one field. The picture element data which correspond to one field are made up of a plurality of picture element data of a first field and a plurality of picture element data of a second field, among picture element data which are obtained by subjecting an analog video signal to a digital pulse modulation, where the analog video signal corresponds to one frame made up of the first and second fields. A reproducing apparatus is designed to reproduce the second field in a sequence different from a sequence with which the recorded picture element data are reproduced from the information recording medium in the first field.

Abstract: In an orthogonal phase modulation method the first and second carriers perpendicular to each other are PM modulated by one of the two color signals or of the two luminance signals, at least one of the four signals consisting of two PM signals, the first and the second carriers are inverted or phase-shifted per 1 horizontal scanning period in such a way that these two PM signals will become phase-shifted by 180 degrees relative to each other per one horizontal scanning period by the time these two PM signals reach their inputs, and these PM signals phase-shifted by 180 degrees relative to each other are multiplexed for inputs in said input means. In a demodulation method, PM signals multiplexed by the PM modulation method are delayed by 1 horizontal scanning period and separated into two PM signals by addition and subtraction before and after the delay, and then the thus separated respective PM signals are PM demodulated by phase-shifting the phase reference signals similarly as in the modulation method.

Abstract: A PCM signal demodulating circuit in which a PCM signal corresponding to a code representative of a first sample value obtained by sampling an analog signal with a first sampling frequency is processed to obtain the first sample value, thereby to calculate a pseudo sample value equivalent to a second sample value obtained by sampling the analog signal at a second sampling frequency higher than the first sampling frequency. This is accomplished by passing the PCM signal through a digital filter, a digital-to-analog converter, and a low-pass filter connected in cascade.

Abstract: A magnetic recording head apparatus includes: a magnetic head body opposing a travelling magnetic tape; a tuning circuit having the head body as a variable inductance element; a high-frequency signal source for generating a high-frequency signal; and a detector connected to the tuning circuit. The inductance of the head body is changed in accordance with a change in the magnetic signal field applied from the magnetic tape. The high-frequency signal is amplitude-modulated in accordance with the high-frequency signal. A peak or envelope waveform of the modulated high-frequency signal is detected by a detector, thereby obtaining a reproduced information signal.

Abstract: An FM demodulating circuit demodulates a frequency-modulated signal of a predetermined channel of frequency-modulated signals of respectively different channels, where the frequency-modulated signals are obtained by frequency-modulating carriers of respectively different frequencies by information signals of respectively different channels and transmitting the frequency-modulated signals in a mutually multiplexed state. The FM demodulating circuit has a demodulated output characteristic such that a frequency at which a differential value describing the slope of a demodulated output characteristic curve becomes maximum, is substantially equal to a center frequency of the frequency-modulated signal of the above predetermined channel, and a frequency at which the differential value becomes minimum is equal to a center frequency of a frequency-modulated signal of a channel other than the above predetermined channel.

Abstract: A method for recording high frequency signals representing data with simultaneous readout of low frequency information, such as servo information prerecorded on a magnetic disk, comprises the step of modulating with the data a carrier signal having a repetition frequency displaced significantly from the baseband of the data. The nonlinearity of the recording channel converts the modulated signal spectrum into the low frequency baseband so that the data is magnetically recorded while the low frequency prerecorded information is read out.