Abstract: At least three heads are mounted on a rotary drum. Between the first and third heads which are located in close proximity to each other and have different azimuth angles, a minute height difference is formed in the rotation shaft direction of the rotary drum. Signals of a plurality of data rates are recorded and reproduced by using the first and second heads or the first and third heads. Two heads having the same azimuth angle are disposed on the rotary drum so as to be opposed each other at a central angle of 180.degree.. In search speed reproduction, search data are reproduced by the two heads. Tracks are divided in the unit of plural tracks so as to form track sets. Search data areas of each track set are disposed at a position of each track which is separated from the edge of a tape by a predetermined distance. In search speed reproduction, the phases of the tracks and the heads are controlled, and all effective data of the search data areas are reproduced by plural scans of the heads.

Abstract: A magnetic recording and reproducing apparatus includes: a recorder for recording information signals so as to form tracks obliquely on a magnetic tape, and for recording pilot signals so that the frequency may differ between different modes such as SP and LP; a reproducing head for reproducing recorded information; an error detecting circuit for comparing the level difference of pilot signals recorded in both tracks adjacent to the track to be scanned by there producing head and for outputting a tracking error signal; and a controller for controlling the feed of the magnetic tape so that the tracking error signal may be balanced. Preferably, in the LP mode, a pilot signal of a higher frequency than that used in the SP mode is recorded. In a tracking error detector for a magnetic recording and reproducing apparatus for detecting the pilot signal, the reproduced signals are sampled at a frequency at a common multiple of each pilot frequency, a pilot signal is detected, and a tracking error signal is output.

Abstract: In a magnetic recording and reproducing apparatus, a recording current setting circuit sets a recording current to be larger by 1 dB or more than a recording current which maximizes a reproduced signal level in correspondence to the shortest recording wavelength in digital signals to be recorded. Recording is performed with a magnetic head onto a metal powder tape including a magnetic layer of thickness having a 0.2 .mu.m or less. Thus, an overwrite characteristic can be obtained which are generally similar to that of a metal evaporation tape. Further, on reproduction, either an output from a equalizer circuit for a metal evaporation tape or an output from another equalizer circuit for a metal powder tape is selected by a switch circuit according to an output of a tape type detection circuit, and loop control gain of a tracking control circuit is changed according to the detected tape type. Thus, both metal powder tapes and metal evaporation tapes can be used.

Abstract: A timing recovering apparatus comprises an equalizer for equalizing a digital data signal subjected to interleaved NRZI such that the digital data signal has partial response (1, 0, -1), two comparators for comparing the equalized data signal with two different reference levels, two phase comparing portions for detecting phase difference between the outputs of the comparators and a reproduced clock signal separately, an adder for summing the outputs of the phase comparators, and a VCO for generating the reproduce clock signal in accordance with the output of the adder. This timing recovering apparatus performs phase comparing with two different phase comparators and PLL control is performed on the sum of the outputs of the two different phase comparators, so that the clock signal is not affected by data pattern of the data signal.

Abstract: A delay circuit is provided with an npn type of transistor of which a base is connected to an input terminal, a first constant current source through which a constant current flows from an emitter of the transistor to ground, a first capacitor arranged between the emitter of the transistor and an electric source terminal, a second capacitor C.sub.22 arranged between a collector of the transistor and an output terminal, a first resistor arranged between the emitter of the transistor and the output terminal, a second resistor arranged between the collector of the transistor and the electric source terminal. The constant current of the constant current source is changeable, and an emitter resistance of the transistor is changed depending on the constant current. Therefore, an analog signal applied to the input terminal is changeably delayed by coaction of the resistors, the capacitors and the emitter resistance adjusted by changing the constant current of the constant current source.

Abstract: A magnetic recording and reproducing apparatus for recording and reproducing a video digital signal suitable to a narrowed track pitch having two magnetic heads with the same azimuth angle arranged with an overlapped area to reproduce the same track, and a tracking servo executing phase control such that a center of a reproducing track is brought to a center of the overlapped area of the two magnetic heads. Reproduced signals of the two magnetic heads are compared so that the reproduced output of the magnetic head having a good on-track condition is always selected to improve a tracking margin without increasing crosstalk disturbance from adjacent track.

Abstract: Disclosed is a tracking error detection system in a digital magnetic recording/reproducing apparatus for recording/reproducing a digital signal, in which a digital signal recorded by means of a magnetic head having an azimuth is reproduced to thereby produce a reproduction clock signal and the phase or period of the reproduction clock signal is measured to thereby detect a tracking error. Since the tracking error can be known every time the phase or period of the reproduction clock signal is measured, it is possible to detect the tracking error including the linearity of a recording track and it is possible to improve the accuracy in tracking error detection. Further, since no pilot signal or the like is frequency-multiplexed on a low frequency, the recording digital is not affected.

Abstract: A tracking error detecting circuit in which tracking error detecting pilot signals having different frequencies are added to a main signal every track and recorded onto a magnetic recording medium, and upon reproduction, reproduction output levels of the pilot signals reproduced as crosstalks from both of adjacent tracks are compared, and a tracking error is detected. n signals having the same frequencies as those of the pilot signals and whose phases are different are generated and multiplied to the reproduction signal. Unnecessary components are eliminated by n LPFs (Lowpass filters). The amplitude values of the reproduced pilot signals are vector separated and detected. Further, the vector separated amplitude values are vector synthesized and detected. Therefore, by multiplying the signals having the same frequencies as those of the pilot signals, the synchronous detection is performed.

Abstract: By transforming a duobinary signal, a value of -1 cannot appear again after a value of zero following -1 as shown in a string of -1.fwdarw.0.fwdarw.-1 and a value of 1 cannot appear again after a value of zero following 1 as shown in a string of 1.fwdarw.0.fwdarw.1. Narrow-band transmission is made possible by the fact that the direct current (DC) component of a duobinary signal can be eliminated and reproducible original information can be recorded by discriminating its even level as a one (1) and its odd level as zero (0). Since the DC component can be eliminated, electromagnetic conversion systems are subjected to less distortion, leading to a reduction in the probability of coding errors.

Abstract: A digital signal magnetic recording and playback apparatus which is applicable to digital video signals, utilizes quadrature amplitude modulation to produce a recording signal from a digital input signal with a carrier frequency being employed which is less than or equal to than the frequency of a recording system clock signal that is synchronized with the successive data values of the digital input signal. Carrier bursts are periodically inserted into the recording signal with a fixed period, through data inserted by a burst data insertion circuit and the carrier and clock signal are arranged to periodically coincide in phase, with the aforementioned period. The carrier frequency is made equal to the clock frequency multiplied by a factor (n/m), where n and m are integers and n<m. During playback, time information obtained from the bursts is used to mutually phase-relate recovered clock and carrier signals.

Abstract: A digital signal magnetic recording/reproducing apparatus modulates a digital signal with a carrier and performs recording/reproducing of the modulated signal. The carrier frequency is made equal to the clock frequency multiplied by a factor (N/M), where N and M are integers. The carrier and clock are reproduced using only one phase locked loop. When the carrier-modulated signal is recorded/reproduced using a magnetic recording medium, the phase of the modulated signal is shifted relative to the phase of the carrier. Shifting the clock phase before using the clock for decoding the demodulated signal prevents a degradation of error rate. By periodically inserting a clock phase reference signal in the recording signal, accuracy of adjustment of clock phase is improved.

Abstract: A digital signal magnetic recording/reproducing apparatus converts a digital signal into multi-value digital signals and performs recording/reproducing of a multi-value quadrature amplitude-modulated signal. By using the multi-value quadrature amplitude modulation, it is possible to remove the DC component in the recording signal and improve the utilization efficiency of the recording frequency band. Further, using a system to memorize the frequency characteristic of the magnetic recording/reproducing unit and effect Viterbi decoding regarding the intersymbol interference caused by the frequency as a convolutional coding, it is possible to detect the level without necessitating frequency equalization. Accordingly, there arises no deterioration of the S/N ratio by frequency equalization. Furthermore, by providing an encoder for error control coding by increasing the number of multi-values and a corresponding decoder, the error rate can be improved against the deterioration of the S/N ratio.

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 digital signal magnetic recording/reproducing apparatus converts a digital signal into a multi-value quadrature amplitude modulated signal, and records and reproduces the multi-value quadrature amplitude modulated signal. By using the multi-value quadrture amplitude modulation, any DC component in the recording signal is removed and utilization efficiency of the recording frequency band can be improved. By bias recording of the multi-value quadrature amplitude modulated signal, non-linearity of the electromagnetic of conversion system is reduced, and deterioration of SN ratio due to distortion is improved.

Abstract: A video signal reproduction apparatus for reproducing a composite color video signal from a recording medium. A signal reproduced from the recording medium is divided into a frequency-modulated (FM) signal and a low-band-converted signal by filters. The FM signal is demodulated by a demodulater into a luminance signal. A first conversion circuit produces from the low-band-converted signal a chrominance signal without a phase jitter component. A second conversion circuit produces from the low-band-converted signal a high-band component of luminance signal with a same phase jitter component as that of the luminance signal obtained from the demodulator. The luminance signal from the demodulator, the high-band component of luminance signal and the chrominance signal are mixed to obtain the composite color video signal.

Abstract: An FM signal demodulator has a phase shifter including transversal filters for producing from a FM video signal two FM video signals which are different in phase by 90.degree. from each other, and a demodulator for detecting phase information of the FM video signal, wherein the carrier frequency is at least quadrupled prior to demodulation so as to suppress components of the FM video signal not to be included in the demodulated video signal.