JPH081735B2 - Digital signal recording / reproducing device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital signal recording / reproducing apparatus for recording / reproducing digital data using 4-phase phase modulation / demodulation or offset 4-phase phase modulation / demodulation technology.

2. Description of the Related Art In recent years, methods such as 8 mm VTR, rotary head digital audio tape recorder (hereinafter referred to as R-DAT), which perform predetermined modulation on digital audio data and record using a rotary head have been used.

In the R-DAT, it is necessary to stabilize the data clock reproduction within the preamble period for the reproduced data reproduced in bursts as shown in FIG. Since the data clock reproduction generally uses the inverted edge of the reproduction for the phase comparison information of the PLL, a pattern having many inverted edges such as 1010 is used as the amble pattern (the data pattern before NRZI modulation is all 1).

The above-mentioned R-DAT will be described below with reference to the drawings.

FIG. 3 shows the structure of the R-DAT. In FIG. 3, 301 is an input terminal for digital data, 302 is an 8-10 converter, 303 is a selector, 304 is an NRZI converter, 305 is a recording amplifier, 306 is a changeover switch, 307 is a magnetic head, 308 is a reproduction amplifier. , 309 is an equalizer, 310 is a data clock regenerator, 311 is an NRZ converter, 312 is a 10-8 converter, 313 is a digital data output terminal, and 314 is a data clock output terminal.

The operation of the R-DAT configured as described above will be described below.

First, the digital data input to the input terminal 301 at a predetermined timing is subjected to 8-10 conversion by the 8-10 converter 302, and the selector 303 selects the B input (all 1 pattern) at the timing of the preamble period described above. And output. In the data period, the output of the 8-10 converter 302 is selected and output. The output of the selector 303 is the NRZI converter 3
It is NRZI converted by 04 and recorded on the magnetic tape through the recording amplifier 305, the switch 306 and the magnetic head 307.

At the time of reproduction, the data recorded on the magnetic tape is input to the data clock regenerator 310 via the magnetic head 307, the switch 306, the reproduction amplifier 305, and the equalizer 309 to stabilize its operation within the above-mentioned preamble period, and the reproduction data is reproduced. , Output the reproduction data clock. The NRZ converter 311 performs NRZ conversion by the reproduced data and the reproduced data clock, and the 10-8 converter 312 10-8 converts the output of the NRZ converter 311 and outputs the result to the digital data output terminal 313.

Here, since the all 1 pattern is used for the amble pattern, it is converted to (1,0,1,0,1,0 ...) After NRZI conversion, and since there is an inverted edge at each bit boundary, good data clock reproduction is possible. It is possible.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention However, a band limitation condition is imposed on the digital signal recording / reproducing apparatus for some reason, and a four-phase phase modulation (hereinafter QPSK) or an offset four-phase phase modulation (hereinafter O-QPSK) is used as a modulation method. ) Is used to reproduce only a predetermined band by using a band-pass filter at the time of reproduction and QPSK or O-QPSK demodulation is considered. Here, the carrier frequency _c in QPSK or O-QPSK modulation, the sampling frequency _s of the modulated digital data, and the bandpass width of the bandpass filter are _c ±
_{It is designated as B} (Fig. 4a). All 1 amble pattern
If it is a pattern, the spread of the bandwidth after modulation is (Fig. 4c) In such a case, if such a reproduced waveform is extracted by the bandpass filter and subjected to QPSK or O-QPSK demodulation, good QPSK or O due to group delay near the cutoff point of the bandpass filter, phase distortion, etc. -QPSK demodulation cannot be performed. Also, when trying to improve the QPSK or O-QPSK demodulation, if the amble pattern is selected to be all 0 (all 1 or all 0 pattern after NRZI conversion), the spectrum after modulation will be as shown in Fig. 4b, which is good. Although demodulation is performed, there is a problem that the data clock cannot be reproduced because there is no inverted edge of the bit boundary in the reproduced data after demodulation.

In view of the above problems, the present invention provides a digital signal recording / reproducing apparatus which has a good QPSK or O-QPSK demodulation and an amble pattern with a good data clock reproduction of the demodulated reproduction data.

Means for Solving the Problems In order to solve the above problems, a digital signal recording / reproducing apparatus of the present invention has a selector for inputting a data pattern to be recorded and a fixed symbol pattern and switching output at a predetermined timing, and a selector output. Serial-parallel converter that converts the data into 2-bit parallel data, and the first and second NR that performs NRZI conversion of each 2-bit output of the serial-parallel converter
The output of the ZI converter and the first and second NRZI converters are modulated by carrier waves with different phases by 90 ° and added together to perform 4-phase phase modulation or offset 4-phase phase modulation, and the output of the modulator is amplified. And a recording device that supplies the output of the recording amplifier to a pair of magnetic heads on a rotating cylinder via a rotary transformer to record on a magnetic tape, and at the time of reproduction,
A regenerative amplifier that receives and amplifies the signal reproduced from the magnetic head, an equalizer that equalizes a predetermined waveform to the output of the regenerative amplifier, and an equalizer output that is input and passes a predetermined bandwidth centered on the carrier frequency. A bandpass filter and a demodulator that receives the output of the bandpass filter as input and demodulates a four-phase phase-modulated signal or an offset four-phase phase-modulated signal, and is synchronously detected by two regenerated carriers whose phases are different by 90 °. And a reproducing device including a first and a second NRZ converters that respectively perform NRZ conversion of the two outputs and a parallel-to-serial converter that receives the outputs of the first and the second NRZ converters as an input and performs parallel-to-serial conversion. It is configured to have.

Operation The present invention has the above fixed configuration to provide a fixed symbol pattern in which there is one 1 in each of the odd-numbered bit and the even-numbered bit in the fixed symbol pattern and all the remaining bits are 0. , QPSK or O-QPSK
It is possible to realize recording / reproduction of a digital signal having an amble pattern that is well demodulated and has good demodulation clock reproduction.

Embodiments A digital signal recording / reproducing apparatus of the present invention will be described below with reference to the drawings.

FIG. 1 shows a digital signal recording / reproducing apparatus according to an embodiment of the present invention. In FIG. 1, 101 is a digital data input terminal, 102 is a selector for inputting a data pattern to be recorded and a fixed symbol pattern and switching and outputting at a predetermined timing, 103 is a 2-bit output of the selector 102.
Serial-to-parallel converter that converts to parallel data
Reference numerals 104 and 105 denote first and second NRZI converters that perform NRZI conversion on 2-bit outputs of the serial-parallel converter 103, and 107 and 108, respectively.
Modulates the outputs of the first and second NRZI converters 104 and 105 with carrier waves having different 90 ° phases from the first 90 ° phase shifter 106, respectively.
Phase-phase modulation or offset 4-phase phase-modulation first and second balanced modulators, 109 is an adder that adds the outputs of the first and second balanced modulators, and 110 is a record that amplifies the output of the adder 109 An amplifier, 111 is a changeover switch for switching and supplying the output of the recording amplifier to a pair of magnetic heads 112 on a rotary cylinder via a rotary transformer, and 113 is a magnetic head when reproducing a signal recorded on a magnetic tape. A reproduction amplifier for amplifying the signal reproduced by 112, an equalizer 114 for equalizing a predetermined waveform to the output of the reproduction amplifier 113, 115
Is a bandpass filter which receives the output of the equalizer 114 and passes a predetermined bandwidth centered on the carrier frequency, and 116 and 117 which receive the output of the bandpass filter 115.
The first and second synchronous detectors for demodulating the phase / phase modulation signal or the offset 4-phase phase modulation signal, 119 is a carrier regeneration circuit, and 120 and 121 are the phases from the second 90 ° phase shifter 118.
° First and second level detectors that detect the levels of two outputs that are synchronously detected by two different reproduction carriers, 12
2 is a data clock recovery circuit, and 123 and 124 are first and second NRs that perform NRZ conversion on the outputs of the first and second level detectors 120 and 121, respectively.
A Z converter, 125 is a parallel-serial converter that inputs the outputs of the first and second NRZ converters 123 and 124 and performs parallel-serial conversion, 126 is a digital data output terminal, and 127 is a reproduction data clock output terminal. Note that D _a and D _b are the first and second N, respectively.
The outputs of the RZI converters 104 and 105, D _a ′ and D _b ′, are the outputs of the first and second level detectors 120 and 121, respectively.

The operation of the digital signal recording / reproducing apparatus configured as described above will be described below with reference to FIG.

First, the digital data input at a predetermined timing from the digital data input terminal 101 is input to the selector 102, and the selector 102, during the preamble period,
Input B is selected and output. In the data period, the digital data is output. Here, the fixed symbol pattern (amble pattern) input to the input B is an 8-bit repeating pattern such as (11000000). The output of the selector 102 is output by the serial-parallel converter 103 to, for example, odd-numbered bits to I and even-numbered bits to Q. Output of serial-parallel converter 103
I and Q are input to the first and second NRZI converters 104 and 105, respectively.
NRZI converted. In the first balanced modulator 107, the first 90
° The carrier phase-shifted by 90 ° by the phase shifter 106 is
Balanced modulation is performed by the output of the RZI converter 104. Second balanced modulator
108 carries out balanced modulation of the carrier _c with the output of the second NRZI converter 105. The outputs of the first and second balanced modulators 107 and 108 are
It is mixed by the adder 109 and is recorded on the magnetic tape through the recording amplifier 110, the changeover switch 111 and the magnetic head 112.

At the time of reproduction, the data recorded on the magnetic tape is supplied to the equalizer 114 via the magnetic head 112, the changeover switch 111, and the reproduction amplifier 113, and predetermined waveform equalization is performed.
The bandpass filter 115 passes only a predetermined bandwidth _c ± _B centered on the frequency _c during the output of the equalizer 114. In the first synchronous detector 116, the output of the carrier regenerator 119 that oscillates the same reproduction carrier frequency as _c
The 90 ° phase shifter 118 performs a 90 ° phase shift to perform synchronous detection. The second synchronous detector 117 performs synchronous detection by the output of the carrier regenerator 119. The outputs of the first and second synchronous detectors 116 and 117 are given to the carrier regenerator 119 as phase error information. The first and second synchronous detectors 116 and 117 are also input to the first and second level detectors 120 and 121, waveform-shaped, and output as two different demodulation axis signals D _a ′ and D _b ′. D _b ′ is input to the data clock recovery circuit 122 and D
inversion edge of _b 'as the phase information, the data clock recovery. The D _a ′ and D _b ′ are respectively input to the first and second NRZ conversion circuits 123 and 124 and NRZ converted, and the respective outputs are parallel-serial converted by the parallel / serial converter 126 and output to the digital data output terminal 126. To be done.

Here, during the amble period, a fixed symbol pattern (11
000000) is recorded by QPSK or O-QPSK modulation, so the spread of the bandwidth after modulation is as shown in Fig. 4d.
The band does not spread to the cutoff point of the bandpass filter 115, and a good demodulated signal can be obtained. At the output D _b ′ of the second level detector 121, four demodulated signals of D _b ′ = ± D _a , ± D _b are conceivable depending on the lock phase of the reproduction carrier, but in the fixed symbol pattern (11000000). Since "1" exists in each of odd-numbered bits and even-numbered bits, inversion points exist in Da and Db four times each, and an inversion edge can be detected without fail.

This enables good carrier reproduction and data clock reproduction at the same time during the preamble period.

EFFECTS OF THE INVENTION As described above, according to the present invention, a fixed symbol pattern is fixed such that there is one "1" in each of the odd-numbered bit and the even-numbered bit, and all the remaining bits are "0". By inserting the symbol pattern, it is possible to realize a digital signal recording / reproducing apparatus in which the carrier reproduction and the data clock reproduction are well drawn in during the preamble period.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of a digital signal recording / reproducing apparatus according to an embodiment of the present invention, FIG. 2 is a timing chart for recording / reproducing digital data, and FIG. 3 is a conventional digital signal recording apparatus. Fig. 4 shows the frequency characteristics of the bandpass filter, all 1, all 0,110000
It is a characteristic view which shows the frequency spectrum when 00 pattern is QPSK and O-QPSK modulated. 101: Digital data input terminal, 102: Selector, 103: Serial / parallel converter, 104: First NR
ZI converter, 105 ... second NRZI converter, 106 ... first 90
° Phase shifter, 107 ... first balanced modulator, 108 ... second balanced modulator, 109 ... adder, 110 ... recording amplifier, 111 ...
... Changeover switch, 112 ... Magnetic head, 113 ... Regenerative amplifier, 114 ... Equalizer, 115 ... Bandpass filter, 116 ... First synchronous detector, 117 ... Second synchronous detector, 118 ... … Second 90 ° phase shifter, 119 …… Carrier regeneration circuit, 120 …… First level detector, 121 …… Second level detector, 122 …… Data clock regeneration circuit, 123 …… First
NRZ converter, 124 ... second NRZ converter, 125 ... parallel-serial converter, 126 ... reproduction digital data output terminal, 127 ... reproduction digital data clock output terminal.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tadashi Yoshino 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Inventor Susumu Yamaguchi 1006 Kadoma, Kadoma City Osaka Prefecture 72) Inventor, Hitoshi Kozen, 1006, Kadoma, Kadoma, Osaka Prefecture, Matsushita Electric Industrial Co., Ltd. (72) Inventor, Tetsuo Ishiwata, 1006, Kadoma, Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (1)

[Claims] 1. A selector for inputting a data pattern to be recorded and a fixed symbol pattern to switch and output at a predetermined timing, a serial-parallel converter for converting the selector output into 2-bit parallel data, and a serial-parallel converter. NRZI conversion of each 2-bit output 1st, 2nd
Of the NRZI converter, a modulator for modulating the outputs of the first and second NRZI converters with carrier waves having different phases by 90 °, adding them, and performing 4-phase phase modulation or offset 4-phase phase modulation; and A recording amplifier for amplifying the output, a recording device for supplying the output of the recording amplifier to a pair of magnetic heads on a rotating cylinder through a rotary transformer and recording on a magnetic tape, and a signal reproduced by the magnetic head during reproduction. A regenerative amplifier that amplifies the output of the regenerative amplifier, equalizes the output of the regenerative amplifier with a predetermined waveform, and a bandpass filter that receives the output of the equalizer as an input and passes a predetermined bandwidth centered on the carrier frequency. A demodulator that receives the output of the bandpass filter and demodulates a 4-phase phase-modulated signal or an offset 4-phase phase-modulated signal, and a phase of the demodulator First and second NRZ converters for respectively NRZ-converting two outputs synchronously detected by two reproduced carrier waves different by 90 °, and parallel-serial conversion using the outputs of the first and second NRZ converters as inputs. And a reproducing device comprising a parallel-to-serial converter for executing, and the fixed symbol pattern is fixed such that there is one 1 for each of the odd-numbered bit and the even-numbered bit and all 0s for the remaining bits. A digital signal recording / reproducing apparatus having a symbol pattern.