JPS6138920B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a spectrum display device that can monitor a multi-channel signal in which part of each frequency band the input signal of a plurality of channels reaches its maximum level with a simple circuit configuration. The present invention aims to provide a spectrum display device.

For example, in an audio stereo tape deck, a VU meter and a spectrum display panel are installed to display the signal level of the input signal and at the same time display its frequency distribution to confirm at what frequency excessiveness is occurring. This is done by lowering the level of the problematic spectral portion and adjusting the recording level correctly for each frequency to achieve good recording without distortion. A method of installing only one spectrum display board and using it to monitor the input level of multi-channel stereo signals is to detect the signal of only the channel with a large input signal among the multi-channels at the entire band level. This can be displayed as a spectrum, but in reality, the input level (level of all bands) and the level of each frequency band may not match, and the signal level of the channel with the smaller input signal among the multiple channels may be excessive. It may become. In this way, simply detecting the input signal at the entire band level and displaying the spectrum of the signal of the channel with the higher level will cause the display of the spectral level to be omitted, making it impossible to accurately monitor the recording level for each frequency. do not have.

Therefore, in the patent application "Spectrum display device for multi-channel signals" dated July 10, 1971, the present applicant compared the levels of each frequency band and displayed the maximum level of each frequency as one spectrum. We proposed a device that displays the spectrum level on a panel to prevent omissions in the display of the spectrum level.

However, this method divides the L channel and R channel signals into respective frequency bands, rectifies and smoothes them, compares the signals in the same frequency band, and extracts the signal with the higher level. Since the circuit is configured to supply signals to the display drive circuit, a rectifying and smoothing circuit must be provided individually for each frequency band of each channel, which poses the problem that the circuit cannot be configured easily and compactly. Ta. In this case, if each rectifying and smoothing circuit is provided with a switch or the like for switching between a circuit for performing average value integration and a circuit for performing peak value integration, the circuit becomes even more complex.

The present invention solves the above problems, and each embodiment thereof will be described below with reference to the drawings.

FIG. 1 shows a block system diagram of a first embodiment of a spectrum display device according to the present invention. In the same figure, the input audio signal of the L channel inputted from the input terminal 1a is amplified and impedance-converted by the buffer amplifier 2a, and has frequency characteristics a ₁ -a with center frequencies f ₁ -f _o as shown in FIG. _{The signal} is supplied to filters 3a-1 to 3a-n having a frequency band of 0, and is divided into n frequency bands whose spectra are displayed on a display panel 10, which will be described later. Filters 3a-1 to 3a-
The signals divided into frequency bands by n are supplied to double-wave rectifier circuits 4a-1 to 4a-n following the filters 3a-1 to 3a-n, respectively, and are double-wave rectified into absolute values.

The above signal processing is performed in exactly the same way for the R channel signal input from the input terminal 1b.
That is, the signal amplified by the buffer amplifier 2b is divided by filters 3b-1 to 3b-n, and double-wave rectified by double-wave rectifier circuits 4b-1 to 4b-n, respectively.

Double wave rectifier circuits 4a-1 to 4a-n, 4b-1,
The L channel signal and the R channel signal, which have been double-wave rectified by 4b-n, are supplied to comparison circuits 5-1 to 5-n provided for each frequency band and compared. The signal from the other channel is extracted without changing its value.
That is, in the specific circuit of comparison circuits 5-1 to 5-n shown in FIG. 3, the signals of the respective channels input to the input terminals 15 and 16 are supplied to the non-inverting input terminals of the amplifiers _A1 and _A2 . For example, if the double-wave rectified signal of the L channel is larger than that of the R channel, the level of the inverting input terminal of amplifier _A2 will be higher than the level of its non-inverting input terminal, so its output will be connected to the negative power supply. The level is approximately equal to the voltage, and the diode _D2 is reverse biased, so that the R channel signal that has entered the input terminal 16 is not taken out, and only the L channel signal that has entered the input terminal 15 is passed through the diode _D1 as it is. output terminal 1 at the level of
Taken from 7. The signals taken out from each output terminal of the comparator circuits 5-1 to 5-n are connected to an operational amplifier A ₃ , a diode D 3 , and a diode D ₃ as shown in FIG.
The signal is supplied to smoothing circuits 6-1 to 6-n, which are configured with FETQ ₁ and the like and capable of high-speed response peak value integration, and is smoothed, and then supplied to the multiplexer 7.

As shown in FIG. 4, the multiplexer 7 is composed of C-MOS integrated circuit analog switch circuits 7-1 to 7-n corresponding to the smoothing circuits 6-1 to 6-n, respectively, and an inverting buffer amplifier 20. The signal fed to multiplexer 7 is sent to decoder 1
The n-ary decoded signals d _{1 to d o as} shown in FIG. . The logarithmic amplifier 8 is, as shown in FIG.
It consists of an amplifier _A4 and a transistor _Q2 connected between its input and output, and the input voltage is V _I
It is configured to output an output voltage V _OUT of K·log V _IN when the voltage is _N. The n serial signals from the multiplexer 7 supplied to the logarithmic amplifier 8 are logarithmically compressed here, and the level axis (Y axis) drive circuit 9
supplied to

The level axis drive circuit 9 has a number of comparators (not shown) corresponding to the number of levels provided on the level axis of the display panel 10, and each comparator has one input terminal connected to the power supply voltage. Comparison reference voltages of different magnitudes divided by respective resistors are applied. The n series signals supplied to the level axis drive circuit 9 are supplied to a comparator and compared with each comparison reference voltage, and if the input voltage is greater than the comparison reference voltage in each comparator, the drive output from that comparator is The level axis display circuit of the display panel 10 (not shown)
supplied to

On the other hand, the n-ary decoded signal d ₁ from the decoder 12
~d _o is supplied to a frequency axis (X-axis) drive circuit 11 to become a drive signal, and is supplied to a frequency axis display circuit (not shown) of the display panel 10. The display panel 10 is
A signal extracted corresponding to each level from the level axis drive circuit 9 and a time division signal extracted corresponding to each frequency band from the frequency axis drive circuit 11 are supplied to the spectrum display element d. to display the frequency distribution of the input audio signal. in this case,
Since the comparator circuits 5-1 to 5-n take out the maximum level signal of the channel with the larger level among the L channel signal and the R channel signal, the spectrum display element d selects the maximum level signal of the channel with the larger level. The maximum level for each frequency band of one channel is displayed, so that even if an excessive spectral component occurs in either channel, it can be easily read, and the display of the spectral level will not be omitted.

As described above, according to this embodiment, after both channel signals are subjected to double-wave rectification, their respective levels are compared, and the signal with the higher level is smoothed to form a serial signal, so that the smoothing circuits 6-1 to 6-1. 6-n only needs to be provided for one channel system, and there is no need to provide it for both channels as in the previously proposed device, and the circuit can be configured easily, compactly, and inexpensively. .

Furthermore, since the signal from the multiplexer 7 is logarithmically compressed and displayed in the logarithmic amplifier 8, the dynamics of each frequency band can be greatly increased.
Easy to check level. In this case, since the signals of each channel are compared and then logarithmically compressed, only one logarithmic amplifier is required compared to, for example, a case where a logarithmic amplifier is used as a preamplifier, and the circuit can be configured more easily. However, the compression circuit may be an inverse logarithmic conversion circuit or the like in addition to a logarithmic amplifier.

In addition, the double wave rectifier circuits 4a-1 to 4a-n, 4b
-1 to 4b-n are configured so that a negative polarity signal is taken out, the comparator circuits 5-1 to 5-n are the sixth
diodes D ₁ , D ₂ connected in the opposite direction to the diodes shown in FIG. 3 and a resistor R ₁ to prevent reaching the overscale level, as shown in the figure.
A circuit composed of R ₂ is used.

Moreover, the smoothing circuits 6-1 to 6-n shown in FIG.
When the switch 17 is connected to the contact 17a, the peak value can be integrated like a peak meter, and when the switch 17 is connected to the contact 17b, the average value can be integrated like a VU meter. The smoothing circuit shown in FIG. 1 may also be used, and the apparatus of the present invention can be configured with fewer switches.

FIG. 7 shows a block system diagram of a second embodiment of the device of the present invention, in which the same components as in FIG. 1 are given the same numbers and their explanations will be omitted. Filter 3a-1
The signals divided into each frequency band by ~3a-n, 3b-1 ~3b-n are passed through diode circuits 14a-
1 to 14a-n, 14b-1 to 14b-n, and is half-wave rectified, and the signal of the channel with the larger absolute value in the same frequency band is sent as it is to each connection point of the diode circuit. It is taken out and supplied to smoothing circuits 6-1 to 6-n, where it is smoothed. The signals smoothed by the smoothing circuits 6-1 to 6-n are directly supplied to the level axis drive circuit 9 via the multiplexer 7, and are then supplied together with the frequency axis drive circuit 11 to the display panel 10 to provide the signals of the first embodiment. It is displayed on the display panel 10 by the same operation as the above.

In this way, according to this embodiment, the diode circuits 14a-1 to 14a-n, 14b-1 to 14b-
In addition to half-wave rectifying the signals of both channels at n, the signals of the channel with the higher level in the same frequency band are taken out as they are, essentially like a comparison circuit, so there is no need for a comparison circuit, and the first
The circuit can be configured more simply than that of the embodiment. Also, filters 3a-1 to 3a-n, 3b-1
By connecting one or two stages of multiple feedback type active band filters using operational amplifiers A ₅ and A ₆ in series to ~3b-n, a sufficiently low output impedance can be obtained, and the output voltage is DC. The components are extracted without being superimposed. Therefore, the diode circuits 14a-1 to 14a-n,1
4b-1 to 14b-n and smoothing circuits 6-1 to 6-n
There is no need for a buffer amplifier (amplifiers A ₁ and A ₂ in FIGS. 3 and 6 in the first embodiment) for driving the heavily loaded smoothing circuits 6-1 to 6-n. From this point of view, the circuit can be easily constructed.

Note that in the second embodiment, the diode circuit 1
4a-1 to 14a-n, 14b-1 to 14b-n
Since half-wave rectification is carried out at , it is not possible to compare the level of the entire signal period compared to the device which performs double-wave rectification as in the first embodiment. However, if it is used for the purpose of displaying the average value of the signal, There are virtually no problems.

Further, although the above embodiment can display the spectral level of a stereo 2-channel input signal, the number of channels is not limited to the above embodiment, and the invention can be similarly applied to multi-channel signals of 3 channels or more. In this case, the comparator circuit includes amplifiers A ₁ to A _o and diodes, as shown in FIG.
D ₁ to D _o may be connected in parallel as appropriate.

Furthermore, filters 3a-1 to 3a-n, 3b-1
A full-band filter including all of the frequency characteristics _a1 to _ao of ~3b-n is used, and the filter 3a-3b-n is installed on the display panel 10.
In addition to the spectrum display by 1 to 3a-n and 3b-1 to 3b-n, the whole band level by the whole band filter may be displayed.

Furthermore, the amplifiers A ₁ and A ₂ in the comparator circuits 5-1 to 5-n may be operational amplifiers such as those in the above embodiments, or
A comparator type amplifier with an open output may also be used; in this case, diodes D ₁ and D ₂ are not required, and the circuit can be easily configured.

As described above, the spectrum display device according to the present invention divides the input signal of one channel into different frequency bands, divides the input signals of multiple channels into the same frequency band, and displays each of the divided signals. The signal obtained by rectifying the signal is compared in level in the same frequency band for each different channel of the plurality of channels, the signal of the channel with the higher level is extracted, and the signal is smoothed to obtain the signal of the plurality of frequencies. Since each band is displayed on one spectrum display panel, it is possible to monitor which part of each frequency band the input signals of multiple channels reach their maximum level. Unlike detecting at the entire band level and displaying the spectrum of the signal of the channel with the higher level, the display of the spectrum level will not be omitted, and the recording level of each frequency band can be monitored correctly, eliminating distortion. After rectifying each channel signal, the levels of each channel are compared, and the signal with the higher level is smoothed and supplied to the display panel. After that, it is only necessary to provide one system for each frequency, and there is no need to provide one for each channel as in the device previously proposed by the applicant, so the circuit can be constructed easily, compactly, and inexpensively. In particular, when the smoothing means is equipped with a switch or the like for switching between a circuit for performing average value integration and a circuit for performing peak value integration,
The device can be configured with fewer switches, etc., and is further provided with a signal conversion means for time-divisionally converting the signal from the smoothing means into a serial signal and compressing the serial signal, so the device is equipped with a compression circuit for each channel. It is possible to obtain a large dynamic range of display level with a simple circuit configuration compared to the above, and furthermore, the circuit for rectification and comparison described above can be used to separate the outputs of the dividing means from each different channel into the same frequency band. Since the configuration is made up of multiple diodes that rectify the signals in the channel and take out the signal of the channel with the higher level in the same frequency band, there is no need for a comparison circuit, and the circuit can be easily configured. Because it is configured with an active filter,
A sufficiently low output impedance can be obtained,
There is no need for a buffer amplifier between the diode and the smoothing means to drive the heavily loaded smoothing means, and from this point of view as well, the present invention has the advantage that the circuit can be easily constructed.

[Brief explanation of the drawing]

1 and 2 are a block diagram of a first embodiment of the spectrum display device according to the present invention and a frequency characteristic diagram of a filter circuit of the device, and FIG. A specific circuit diagram of the smoothing circuit, Fig. 4 is a specific circuit diagram of the multiplexer and logarithmic amplifier of the device shown in Fig. 1, and Fig. 5 D ₁
~D _o is an output signal waveform diagram of the decoder of the device shown in FIG. 1, FIG. 6 is a specific circuit diagram of another embodiment of the comparison circuit and smoothing circuit of the device shown in FIG. 1, and FIGS. Fig. 8 is a block system diagram of the second embodiment of the device of the present invention, and a specific circuit diagram of the filter circuit, smoothing circuit, and multiplexer of the device, and Fig. 9 shows the device of the present invention as a device for displaying input signals of m channels. FIG. 2 is a specific circuit diagram of a comparison circuit when applied to. 1a, 1b...input terminals, 3a-1 to 3a-
n, 3b-1 to 3b-n...filter circuit, 4a
-1 to 4a-n, 4b-1 to 4b-n...Double wave rectifier circuit, 5-1 to 5-n...Comparison circuit, 6-1 to
6-n...Smoothing circuit, 7...Multiplexer, 8
... Logarithmic amplifier, 10 ... Display panel, 12 ... Decoder, 14a-1 to 14a-n, 14b-1 to 1
4b-n...Diode circuit, _A1 to _A6 ...Amplifier.

Claims (1)

[Claims] 1. The input signal of one channel is divided into different frequency bands, the input signals of multiple channels are divided into the same frequency band, and each of the divided signals is rectified. The signal is compared in level in the same frequency band for each different channel of the plurality of channels, the signal of the channel with the higher level is extracted, and the signal is smoothed to obtain one spectrum for each of the plurality of frequency bands. A spectrum display device configured to display information on a display panel. 2. A plurality of frequency band dividing means that divides the input signal of one channel into different frequency bands and divides the input signals of multiple channels into the same frequency band, and double-wave rectification of each signal from the dividing means. a rectifying means for comparing the levels of the rectified signals in different channels of the plurality of channels in the same frequency band and extracting the signal of the channel having the higher level; and the comparing means and a spectrum display element having a plurality of frequency bands each corresponding to the frequency band of the signal from the frequency band dividing means and displaying the level of the frequency band divided signal as a spectrum. 1. A spectrum display device comprising a display panel to which an output voltage from a smoothing means is applied and displays a level corresponding to the voltage. 3. A plurality of frequency band dividing means that divides the input signal of one channel into different frequency bands and divides the input signals of multiple channels into the same frequency band, and double-wave rectification of each signal from the dividing means. a rectifying means for comparing the levels of the rectified signals in different channels of the plurality of channels in the same frequency band and extracting the signal of the channel having the higher level; and the comparing means a smoothing means for smoothing the signal from the smoothing means, a signal conversion means for time-divisionally converting the signal from the smoothing means into a serial signal and compressing the serial signal, and a signal converting means for smoothing the signal from the frequency band dividing means, respectively. a display panel provided with a spectrum display element having a plurality of corresponding frequency bands and displaying a spectrum of the level of the frequency band divided signal, to which an output voltage from the signal converting means is applied, and displaying a level corresponding to the voltage; A spectral display device characterized by: 4 A plurality of frequency band dividing means for dividing an input signal of one channel into different frequency bands and dividing input signals of a plurality of channels into the same frequency bands, and dividing the output of each of the dividing means into the plurality of channels. a plurality of diodes for rectifying each of the different channels in the same frequency band and extracting the signal of the channel having a higher level in the same frequency band; and smoothing means for smoothing the signals from the plurality of diodes. , a spectrum display panel element having a plurality of frequency bands each corresponding to the frequency band of the signal from the frequency band dividing means and displaying the level of the frequency band divided signal in a spectrum is provided, and the output voltage from the smoothing means is applied. 1. A spectral display device comprising: a display board that displays a level corresponding to the voltage. 5. The spectrum display device according to claim 4, wherein each of the plurality of frequency band dividing means is constituted by an active band filter.