JPS58154670A - Display device of level - Google Patents

Abstract

PURPOSE:To obtain a highly accurate level displaying device having a highly dynamic range which is suitable for a PCM recording and reproducing device e.g. by directly converting a digital data into a digital signal indicating the logarithm of said data value and then converting the digital signal into an analog signal to dispay the digital data as analog value. CONSTITUTION:The output terminal of an ADC15 is connected to the input terminal of a record processing circuit 16 and also connected to the contact of a switch S0. The output terminal of a reproducing circuit 18 is connected to the input terminal of a DAC19 and also connected to the terminal of the switch S0. The movable contact of the switch S0 is connected to the input terminal of a logarithmic converter 31. The output part of the logarithmic converter 31 is connected to the input part of a DAC32. The output terminal of the DAC32 is connected to the input terminal of a separating circuit 33. A pair of output terminals of the separating circuit 33 are connected to a pair of input terminals of a display device 36 correspondingly through amplifiers 34, 35 and then time constant circuits each of which consists of a capacitor and a resistor.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a level display device suitable for, for example, a PCM recording/playback device that converts an audio analog signal into a digital signal for recording and playback.

[Technical background of the invention]

Recently, PCM technology has been used to convert i1 audio analog signals into digital signals for recording and playback.
Recording/playback devices and digital audio discs (DAD)
), so-called digital audio equipment such as DAD f rake that plays back audio is actively being developed. With such digital audio equipment, it has become possible to easily record and reproduce high quality audio analog signals.

For example, a conventional PCM recording and playback equipment company is configured as shown in Fig. 1, and a low-pass filter (hereinafter referred to as L
An analog-to-digital converter (hereinafter referred to as AD) with a multiplex circuit via a Sansol hold circuit (hereinafter referred to as SA) 13.14
1501 pairs of input terminals (referred to as C). The ADC 15 multiplexes the two-channel audio analog signal, converts it into a digital signal (digital data), and supplies it to the recording processing circuit 16.

The recording processing circuit 16 adds an error detection code to this digital signal.
It performs various signal processing such as adding an error correction code, etc., and superimposes these signals on, for example, a television signal so that it can be recorded on a recording and reproducing device 11, which is a video tape recorder.

This recording/reproducing device records a good signal from the recording/reproducing device N16 and supplies the good signal in a reproducing state to the reproducing processing circuit 18. The reproduction processing circuit 18 performs reproduction processing to restore the original digital data from this signal, and supplies it to, for example, a digital-to-analog converter (hereinafter referred to as DAC) Ja having a demultiplexer. DACJ # converts the digital data into the original left and right audio analog signals, and correspondingly outputs them to the output terminal (0UTL) via LPF j O, 211.
) - (OUT 凰).

The level display of a PCM recording and reproducing apparatus having such a recording system and a reproducing system is performed by converting the output signal of each LPF 10. Logarithmic conversion is performed via logarithmic amplifier circuits x4 and 2g via xs.

Each of these two logarithmically converted analog signals is supplied to a display 26 for displaying the level of two channels through corresponding time constant circuits each consisting of a resistor and a capacitor. Thereby, the display 26 can monitor the analog signal level in the recording state and the playback state by changing the switch (8).

[Problems with background technology]

However, the full-wave rectifier circuit XX described above.

23. Logarithmic amplifier circuit 24. For example, the level display device configured by the display device 26, etc. is a full-wave rectifier circuit x
Due to the initial characteristics (non-linearity, temperature characteristics) of the closing diodes constituting the i, 2s, high accuracy and high dynamic range cannot be obtained.

[Purpose of the invention]

This invention was made in view of the above points, and for example, P.
It is an object of the present invention to provide a level display device suitable for a CM recording/playback device and having high accuracy and a high dynamic range.

[Summary of the invention]

This invention is characterized by directly converting digital data into a digital signal by taking the logarithm of its value, and converting this digital signal into an analog signal, thereby displaying the value of the digital data in analog form. shall be.

[Embodiments of the invention]

An embodiment of the present invention will be described in detail below with reference to the drawings.

FIG. 2 shows an embodiment of a level display device according to the present invention applied to a PCM recording/playback device serving as a digital signal processing device. Components that are the same as those in FIG. 1 are designated by the same reference numerals and their explanations will be omitted.

That is, the output terminal of the DCJ i is connected to the input terminal Km of the recording processing circuit 16 and the a contact Km of the switch (86). The output end of the reproduction processing circuit 11 is connected to the 0 input end of the DACJ and also to the b terminal of the switch S. The movable section of the switch S is connected to an input terminal of a logarithmic converter 31, which will be described later.

The output of the logarithmic converter 3 is connected to the input of DACJJ. The output terminal of this DACJ X is connected to the input terminal of the separation circuit 33. This separation circuit 3
3, for example, a pair of output terminals correspond to amplifiers 34, 38.
The input terminals are respectively connected to input terminals of a pair of display devices 3601 via corresponding time constant circuits such as capacitors and resistors.

The logarithmic conversion circuit 3 is, for example, a series-parallel transfer unit as shown in FIG.
II, read-only memory (hereinafter referred to as ROM) M
It is composed of L. A serial digital signal (digital data) supplied to the terminal It is serial-parallel converted by the serial-parallel converter VP.

For example, in the case shown in the figure, these 12-bit signals are processed by the exclusive OR circuits EXl to EX, and when the indicated value is positive, the lower 11 bits are directly stored in the ROM (M
When the value supplied to the address input section of (1-) is negative, the most significant bit level is detected, the 10's complement is taken, and the lower 11 bits are supplied to the ROM (ML). This is K
Otherwise, the absolute value of the above digital data will be taken.

On the other hand, [M(MA) is configured to output, for example, a 5-bit logarithmic value corresponding to the above-mentioned 12-bit digital data from the output section at. As a result, the digital data supplied to the input terminal It is logarithmically converted and outputted from the output section OL. In addition, as shown above, when the 12-pit signal is negative, the 1's complement is used as the absolute value because the error is negligible even when compared with the 2's complement. .

The separation circuit 12 is constructed using a so-called demultiplexer.
are configured, and each of the ADC1j and DAC1#! In response to the synchronizing signal of the multiplexer and demultiplexer section, the D/CSXO output signal is transmitted to each of the amplifiers 34.
It is divided into 35 parts and 9 parts.

The display 36 is configured to display, for example, the DC level (effective value to peak value) supplied to the pair of input terminals separately in analog quantities.

That is, in the level display device configured as described above and applied to a PCM recording/playback device, the level of each analog signal supplied to the input terminals INL, IN, and the output terminals 0UTL, 0UTL, and 0UTL are changed by changing the switch S, respectively. 0UT
It is possible to selectively monitor each analog signal level output from i+.

In this case, unlike the conventional example shown in Figure 1, the level display is performed after directly logarithmically converting the digital data in an f-notal manner. It is possible to remove spurious causes of a difference of 1, such as 醇, and it is possible to display levels with extremely high accuracy. In addition, since it is not affected by the dynamic range of the logarithmic amplifier circuit, a high dynamic range is guaranteed in the level display. still,
Amplifiers 34 and 35 are for buffer amplification.

Although the above explanation applies the level display device according to the invention of the present application to a PCM recording/playback device, it is a hot topic that it can also be applied to devices using PCM technology such as a DAD player. As described above, since the level display device according to the present invention can obtain high accuracy, it can be applied to measuring instruments having a digital signal processing section, for example, by using a display device having a recorder. .

Further, in the above embodiment, the logarithmic converter is configured using a ROM, but it can also be realized by a combinational circuit based on the well-known logic r-).

It goes without saying that various other modifications and applications are possible without departing from the gist of the invention.

〔Effect of the invention〕

As described above, according to the present invention, for example, pcy, a
It is possible to provide an excellent level display device that is suitable for sound reproduction devices and has high precision and a high dynamic range.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the configuration of a conventional level display device, FIG. 2 is a diagram showing the configuration of an embodiment of the level display device according to the present invention, and FIG. 3 is a diagram showing the logarithmic converter of the device in FIG. FIG. 3 is a circuit diagram showing a configuration example. 31... Logarithmic converter, 32... DAC, JJ...
Separation circuit, 34.35...Amplifier, 36...Display device, S/P...Series-parallel converter, ■1 + EXI
r... EX u...Exclusive OR circuit, Mt...RO
M applicant's representative Patent attorney Takehiko Suzue Figure 1 Figure 2

Claims (1)

[Claims] A first means for extracting digital data from a digital signal processing device and deriving a digital signal obtained by converting the digital data value into a logarithm; and a second means for converting the digital signal obtained by the first means into an analog signal. And this second
a third displaying the analog signal level obtained by the means of
A level display device comprising: means.