JPS5869145A - Analog-to-digital and digital-to-analog converter for broad band signal - Google Patents

Abstract

PURPOSE:To record and reproduce a broad band signal in an excellent way, by dividing an input signal into high and low luminance frequency components, converting the high luminance component to a low frequency, applying both components A/D conversion for storage, reading out the components through band compression, and reproducing them after applying D/A conversion and executing magnetic recording. CONSTITUTION:A broad band input signal Y applied to an input terminal 101 is applied to an A/D conversion section 110 and the signal is separated into a low luminance frequency component YL and a high luminance frequency component YH at an LPF111. The signal YH is frequency-converted 116 into a low frequency component YHL, the signals YL and YHL are A/D-converted 113, 118 and recorded 120 respectively. The signals are read out in a half speed of writing, band-compressed and D/A-converted 130 and recorded on a magnetic tape 145. A reproducing signal is picked up from the tape 145, and amplified, fed to a limiter, demodulated digitized and written in a memory, and then read out as twice speed as writing, D/A-converted to synthesize the low and high frequency components.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an A/D-D/A conversion device for transmitting wideband signals via a digital signal transmission system.

Conventionally, various signal processing such as signal delay processing, band compression, and expansion processing have been performed using digital signal transmission systems such as digital memories. When transmitting a signal via the digital signal transmission system, an analog-to-digital (A, /D) converter that converts the input analog signal into a digital signal and supplies it to the transmission system; A/D-D consists of a digital-to-analog (D/A) converter that converts the digital signal output through the converter into an analog signal.
/A converter is used. By the way, in general, A/D
As the operating frequency of a converter becomes higher, the S/N deteriorates, so it is difficult to faithfully convert a high frequency signal into a digital signal. Furthermore, there are limits to the amount of data and transmission speed that can be transmitted in a digital signal transmission system, and it is not possible to directly A/D convert and digitally transmit a wideband signal that includes high frequency signal components.

By the way, a normal video tape recorder has a bandwidth of only about 8 MHz, which is necessary for recording and reproducing general video signals.

A wideband video signal whose bandwidth has been expanded to about 20 MHz for high-resolution image reproduction cannot be directly recorded and reproduced, and it is necessary to perform band compression processing on the wideband video signal before recording. However, if we try to apply band compression processing to a video signal with a bandwidth of 20 MHz using a digital signal transmission system, an A/D converter with a bandwidth of 40 MHz and an operating clock frequency of about 100 MHz is required. A/D converters that have been put to practical use cannot handle the above-mentioned wideband video signals. Note that the limits of high-speed A/D converters for video signals that have been put into practical use so far are those with a bandwidth of about 20 MHz' and an operating clock frequency of about 39 MHz.

Therefore, in view of the above problems, the present invention divides a wideband input signal into a high frequency signal component and a low frequency signal component, and converts the high frequency signal component into a low frequency converted signal. The low frequency signal component and the low frequency converted signal component are converted into analog/digital (A
l1) An A/D converter that converts and supplies the digital signal transmission system to a digital signal transmission system, and converts each digital signal component outputted through the digital signal transmission system into digital/analog (D
/A) converting and reproducing a low frequency signal component and a low frequency converted signal component, frequency converting the low frequency converted signal component to reproduce a high frequency signal component, and converting the low frequency converted signal component to reproduce a high frequency signal component; and a D/A converter that synthesizes signals and outputs high-frequency components.
The present invention provides an Al1-D/A converter with a novel configuration that enables signal processing of wideband input signals using a digital signal transmission system.

Hereinafter, the present invention will be described in detail with reference to the drawings showing one embodiment.

The embodiment shown in FIG. 1 is a delay device that digitizes a wideband signal, writes it into a digital memory, and gives an arbitrary amount of delay to the wideband signal by varying the reading time of the stored contents of the digital memory. This is an apparatus to which the present invention is applied.

In this embodiment, a wideband input signal, for example, a luminance signal YIN of a high resolution video signal, which is supplied to the A/D conversion block 10 through a signal input terminal 1, is processed by a low pass filter 11, a first analog delay circuit 14 and a signal subtracter 1.
5, the band is divided into a high-band luminance signal component Yl (and a low-band luminance signal component YL. That is, for example, the second (g
Input luminance signal Yen of wideband bandwidth FB as shown in 4A
The signal subtractor 15 extracts the low frequency signal component YL shown in FIG. and the low frequency signal component YL.

The low-band luminance signal component YL is then supplied to the first A/D converter 13 via the second analog delay circuit 12, digitized by the A/D converter 13, and stored in the memory block 20. is written into the first digital memory 21 of. Further, the high frequency luminance signal component Yn is converted by the first frequency converter 16 so that its center frequency fh is changed to the low frequency H
After frequency conversion, the signal is digitized by the second A/D converter 18 and written into the second digital memory 21 of the newt block 20.

Here, the first frequency converter 16 is supplied with a local oscillation signal having a frequency fj from a local oscillator (not shown), converts the frequency of the high-frequency luminance signal component YH using the local oscillator signal, and converts the frequency of the high-frequency luminance signal component YH, Of the waveband components YHL and YHH, the lower sideband YHL shown by the solid line in the second figure is supplied to the A/D converter 18 via the bandpass filter 17. The A/D converters 13, 18 and the digital memories 21, 22 operate based on a first clock signal CKl from a clock generator (not shown).

Furthermore, the second analog delay circuit 12 includes each of the A
/D converter 13.18 and digital memory 21.22
In order to synchronize the operation timing, a delay amount is given to the low-band luminance signal component YL.

Then, in the memo reblock 20, the data of the low frequency luminance signal component YL written in the first digital memory 21 and the data of the low frequency converted luminance signal component YHL written in the second digital memory 22 is read out according to a second clock signal CK2 from a clock generator (not shown). Each data read from this memory block 20 is supplied to a D/A conversion block 30, and each data
/A converters 31 and 34 convert the signals into analogs. The delayed low-frequency luminance signal YL', which is obtained through the first D/A converter 31 and shown in FIG.
After attenuation components and the like of the clock signal are removed, the clock signal is supplied to the signal adder/synthesizer 38 via the third analog delay circuit 33. Further, a delayed low-frequency conversion luminance signal component Y as shown in FIG. 2F obtained via the second D/A converter 34
HL is supplied to a second frequency converter 36 via a low-pass filter 35. This second frequency converter 36 is supplied with the local oscillation signal of frequency fj that is supplied to the first frequency converter 16, and by this local oscillation signal, the delayed low-frequency converted luminance signal component YHL The center frequency fhL is converted to the original frequency fh degrees and the signal o' is passed through the bandpass filter 19 to the signal adder/synthesizer 38.
supply to.

The signal addition synthesizer 38 adds and synthesizes the delayed low-range luminance signal component 'YL' and the delayed high-range luminance signal component YH', thereby producing an output luminance having a delay amount with respect to the input luminance signal YIN. Outputs the signal YOUT. here,
The amount of delay given to the output luminance signal Y OUT is as follows:
Since it depends on the storage time of each data in 12, it can be arbitrarily set depending on the read time of each data.

In the embodiment configured as described above, each A/D converter 13, 18 of the A/D conversion block 10 divides a wideband signal, that is, an input luminance signal YrN into a low band luminance signal component YL and a high band luminance signal component. Since A/D conversion is performed for YH, the operating bandwidth may be narrow. In addition, a second A that takes charge of A/D conversion of the high-frequency luminance signal component Yo
The /D converter 18 performs A/D conversion on the signal component Yn+ obtained by converting the high frequency luminance signal component YH to a low frequency. Therefore, when directly A/D converting the high frequency luminance signal component YH, In comparison, the operating frequency can be lowered, and a conventional A/D converter can perform an A/D conversion operation that satisfies the sampling theorem.

As is clear from the description of the above embodiments, when a wideband signal is digitized and signal processed, the wideband signal is divided into bands in an A/D conversion block, and its high frequency components are converted to a low frequency. By performing A/D conversion on the A/Ilq converter, the operating frequency range of the A/Ilq converter can be narrowed and the operating frequency can also be lowered. As for the transmission system, its operating frequency range is narrow,
Moreover, the operating frequency may also be low. Then, the digital signal processed by the signal transmission system is converted into an analog signal by the D/A conversion block, and high frequency conversion corresponding to the low frequency conversion is performed, and then signal synthesis is performed in an analog manner. By doing so, the wideband signal can be normally reproduced.

Next, the embodiment shown in FIGS. 3 and 4 uses the A/D-D/A converter according to the present invention based on the above-mentioned operating principle to record and reproduce wideband video signals. This is a high-resolution video tape recorder.

FIG. 3 is a block diagram showing a recording system circuit of a video tape recorder, in which a high-resolution video signal (luminance signal) is supplied to an A/D conversion block 110 through an input terminal 101. is converted into a digital signal and written into the memory 120. In the A/D conversion block 110, the low-frequency luminance signal component YL(n) of the luminance flY(nl) is extracted by the low-pass filter 111, and the low-frequency luminance signal component YL(n) in the luminance flY(nl) is extracted by the first A/D converter 113. "L(n) is digitized, and the signal subtracter 115 subtracts and synthesizes the low-range luminance signal component YL(n) with respect to the luminance signal Y(n), thereby obtaining the high-range luminance signal component Yl((n). ), the high frequency luminance signal component Y)(n) is subjected to low frequency conversion by the frequency converter 116, and the low frequency converted luminance signal component YHL(n) obtained via the band pass filter 174 is In other words, the A/D conversion block 110 converts the luminance signal Y(n) into a low-range luminance signal component YL(n) and a high-frequency luminance signal component YH. In addition to dividing the band into (n),
After converting the center frequency of the high-range luminance signal component Yn (J7) to a low-range frequency, each signal component YL(n) is generated.

Perform A/D conversion of YHL(n). In addition, the above A/
“Each analog delay circuit 1 in the D conversion block 110
12.114 is each signal component Yqn), Yr(L(
It works to adjust the time lag of n).

The luminance signal digitized by the A/D conversion block 110 is written into the memory 20, and is read out from the memory 20 at the writing speed, thereby performing band compression processing. Here, if each luminance signal for the horizontal period is denoted by Y, (n=j, 2°...), then the fifth
The luminance signal Y(n) shown in FIG.
n) and are written in the memory 20 as shown in FIG. 5B. Then, the data is read out from the memory 20 via the switch circuit 125 at the signal and writing speed as shown in FIG. 5C. Reading from the memory 20 via the switch circuit 125 is performed by the D/A converters 131A, 1310° 134A, 134, respectively.
It is converted into an analog by B. Note that each D/A converter 13
The leakage components of the clock signals at 1A, 131B, 134A, and 134B are filtered through a low-pass filter 32A, respectively.
, 132B.

135A and 135B. Then, each low-pass converted luminance signal component YHL(2n-1), YHL(2
n) is subjected to high frequency conversion processing corresponding to the low frequency conversion in the A/D conversion block 110 by frequency converters 136A and 136B, respectively. Here, in this embodiment, band compression processing is performed at a read speed of - from the memory 20, so each of the frequency converters 136A.

The frequency of the local oscillation signal supplied to the A/D conversion block 110 is also set to i of the frequency fj of the local oscillation signal supplied to the frequency converter 116 of the A/D conversion block 110.

That is, a local oscillator signal with a frequency of fJ outputted from the reference oscillator 150 is frequency-downgraded by a 7-frequency downgrader 151, phase-matched via a phase shifter 152, and then supplied to each frequency converter 136A, 136B. ing.

Furthermore, each high frequency luminance signal component YH (2n-1
), Y)+(2n) is the band pass filter 37
A and 137B are supplied to signal adders 138A and 138B, and corresponding low-band luminance signal components YL (2n-1) and Yr are supplied to signal adders 138A and 138B.

(2n) is added and synthesized. Note that the signal adder 13
8A and 138B, each low frequency luminance signal component YL (2n-
1) , Yr, (2n) is the analog delay circuit 133
A and 133B, and time alignment is performed with each high-frequency luminance signal component Yo (2n-1) and Yo (2n).

Then, from each of the signal adders 138A and 138B,
As shown in FIG. 5, two-channel signals Y(2n-1) and Y(2n) are obtained by sequentially distributing and arranging the signal Yn obtained by performing band compression processing on the input luminance signal Yn. These two-channel signals Y(2n-1) and Y(2,) are F
The M modulators 141A and 141B convert the signals into FM signals, and the signals are sent to each magnetic head 143 via recording amplifiers 142A and 142B.
A and 143B, and magnetically recorded on the magnetic tape 145.

Next, Figure 4 is a block diagram showing the reproduction system circuit. Yes, magnetic tape 141 each magnetic helad 243A.

The two-channel FM signal reproduced by 243B is
From the regenerative amplifiers 244A and 244B to the amplitude limiter 245A
, 245B to FM demodulators 246A and 246B for demodulation. The above FM demodulators 246A, 246B
As shown in FIG. 6A, the demodulated output signal from
2n), so the A/D converters 247A and 2
Bandwidth expansion processing is performed by digitizing the data at 47B and writing it into the memory 250, and reading from the memory 250 at twice the writing speed. Then, the band-expanded two-channel signals Y(2n-1) and Y(2,) read from the memory 250 are sent to the switch circuit 26.
0 to the D/A converter 2 alternately as shown in FIG. 6B.
70 and converted into an analog signal by the D/A converter 270 as shown in FIG.
get. In addition, each of the above A/D converters 247A, 2478
1 memory 250, based on the reproduction synchronization signal contained in the demodulated output signals from the FM demodulators 246A and 246B and the reference synchronization signal from a reference signal generator (not shown).
It operates using a clock signal generated by a clock signal generator 280.

In a video tape recorder constructed by applying the present invention as in this embodiment, a wideband luminance signal Yn is subjected to digital signal processing (in this embodiment, band compression processing), magnetically recorded, and then recorded and reproduced. can be done faithfully. In the A/D conversion block, the wideband luminance signal is band-divided and converted into low frequency signals before being digitized, so that the A/D conversion operation can be performed using a low-speed lock signal. In addition, the above A
The memory for performing signal processing on the data digitized by the /D conversion block can also be operated using a low-speed clock signal. In the digital signal processing in the reproducing circuit, the band-compressed luminance signal is further arranged into two-channel signals and recorded in the recording circuit, so the operating clock frequency thereof is also low. That is, the entire video tape recorder can perform signal processing digitally at a slow clock frequency.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of a wideband signal delay device constructed by applying the present invention. FIG. 2 is a frequency distribution diagram for explaining the operation of the above embodiment. 3 to 6 are drawings showing an embodiment of a video tape recorder configured to apply the present invention, FIG. 3 is a block diagram showing the configuration of a recording system circuit, and FIG. 4 is a reproduction system circuit. FIG. 5 is a time chart for explaining the operation of the recording system circuit, and FIG. 6 is a time chart for explaining the operation of the reproduction system circuit. 1.101... Wideband input signal YIN, Y(-)
Input terminal 10.110...A/D conversion block 1i
, iii...Low pass filter 13.1 for band division
13... A/D converter 15.115... Signal subtracter for band division 16.11
6... Frequency converter 20.120 for low frequency conversion
...Memory block for digital signal processing 21.22...Digital memory 30.130.
...D/A conversion block 31.34.131A, 131
B, 134A. 134B・・・・・・D/A converter 36.136
A, 136B... Frequency converter 38 for high frequency conversion. 138A, 138B... Signal adder Patent applicant Sony Corporation representative Patent attorney Kodo Koike 1) Sakae Mura -

Claims (1)

[Claims] Band-dividing a wideband input signal into a high frequency signal component and a low frequency signal component, frequency converting the high frequency signal component to a low frequency conversion signal component, and converting the high frequency signal component to a low frequency conversion signal component. An A/D converter converts the signal component into analog/digital (A/D) and supplies it to the digital signal transmission system.
The D conversion unit converts each digital signal component outputted through the digital signal transmission system into digital and analog (
D/A) converting and reproducing a low frequency signal component and a low frequency converted signal component, and frequency converting the low frequency converted signal component to reproduce a high frequency signal component, A/D for wideband signals, consisting of a D/A converter that synthesizes and outputs the high-frequency components and the high-frequency components.
”-D/A conversion device.