JPH10253671A - Measuring apparatus for signal spectrum - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a measuring apparatus which shortens the time required for measuring all passage frequencies without lowering its measuring accuracy. SOLUTION: Two sets of band-pass filter circuits BPF 11A, 11B and peak hold circuits P/H 12A, 12B are installed, and the frequency of the operating clock of the first band-pass filter circuit 11A is set at a frequency which is 0.3 times the frequency of the operating clock of the second band-pass filter circuit 11B. Three passage frequencies are set for both band-pass filter circuits 11A, 11B, and the relationship between frequencies f1 to f3 of one out of the circuits is set to be fn≈10<n-1> .f1 (where n=1 to 3). The relationship regarding the frequencies of the other is set in the same manner.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a signal spectrum measuring apparatus using a band pass filter circuit capable of obtaining frequency spectrum components of a plurality of pass bands in a time-division manner, and more particularly to a measuring apparatus for measuring the measuring time. The present invention relates to a technology that pursues both shortening and higher measurement accuracy.

[0002]

2. Description of the Related Art For example, there is a spectrum measuring and displaying apparatus as an apparatus for detecting and displaying individual signal levels of a plurality of discrete frequencies of an audio signal. As shown in FIG. 21, an input audio signal is taken into a switched-capacitor band-pass filter circuit 1 whose passing frequency is controlled so as to be switched at high speed in a cyclic manner. The peak value of the passing frequency signal is sequentially detected and held, converted into a digital signal by the control unit 3, and the liquid crystal display device 5 is driven by the display driver 4,
The frequency spectrum of the audio signal is displayed there. Here, the band-pass filter circuit 1, the peak hold circuit 2, and the control unit 3 constitute a signal spectrum measuring device 6.

[0005] The switched capacitor type band pass filter circuit 1 is configured as shown in FIG. OP
Reference numeral 1 denotes an operational amplifier that functions as an integrator, and any one of n feedback capacitors C11 to C1n is selectively connected between its output terminal and an inverting input terminal.
The selection of this capacitor is determined by n pairs of analog switches X1
This is performed by turning on one of a pair of switches among 1, X12,..., X1n under the control of the switch signals M1 to Mn. These capacitors C11 to C1n
Determines the integration constant.

[0004] OP2 is a similar operational amplifier, and any one of n feedback capacitors C21 to C2n is selectively connected between its output terminal and an inverted input terminal. The selection of the capacitor is performed by turning on one of the n pairs of analog switches X21, X22,..., X2n under the control of the switch signals M1 to Mn. Again, capacitor C
An integration constant is determined by 21 to C2n.

A circuit including analog switches S1 to S4 and a capacitor Cb, a circuit including analog switches S5 to S8 and a capacitor C3, and analog switches XS9 to S
14 and capacitors Ca and Ci constitute a switched capacitor circuit, respectively.
2 functions as an equivalent resistance. The clock φ1 is an odd-numbered switch among the switches S1 to S14 (S1, S3, S5, S7, S9, S11,
S13), and the clock φ2 is set to the even-numbered switches (S2, S4, S6, S8, S10, S12, S14).
Drive.

As shown in FIG. 25, these clocks φ1 and φ2 are two-phase clocks having the same frequency and inverted in phase with each other.
The frequency is set to a frequency of 100 Hz to 100 KHz, and the duty is set such that when one of them is active ("H" turns on the switch), the other is completely inactive ("L" turns off the switch). . That is, the clocks φ1 and φ2 do not become active at the same time.

In this bandpass filter circuit 1, FIG.
As shown in FIG. 6, when n switch signals M1 to Mn are input and only the switch signal M1 is active for a certain period, the capacitors C11 and C21 are selectively connected at the same time, and then only the switch signal M2 is active. , The capacitors C12 and C22 are selectively connected at the same time,..., And then the capacitors C1n and C2n
Are selectively connected at the same time, and then only the switch signal M1 is activated, so that the capacitors C11 and C2
1 are selectively connected at the same time, the integration capacitors are switched sequentially and cyclically, and the integration constants of the operational amplifiers OP1 and OP2 are switched n times per cycle, whereby n passages are performed. The frequency is switched.

That is, a band-pass filter circuit in which n pass bands are set in a time division manner in a unit time is realized. The center frequency fo of the pass band of the band-pass filter circuit 1 is determined by the following equation (1). fc is the frequency of the operation clocks φ1 and φ2. fo = (fc / 2π) · {(Ca · Cb) / (C1n · C2n)} 1/2 ···· (1)

FIG. 23 is a diagram showing a circuit configuration of the peak hold circuit 2, in which an operational amplifier OP3 and a pMOS transistor MP1 connected to its output side, resistors R1, R2,
It comprises a holding capacitor Cp, a reset nMOS transistor MN1, and an operational amplifier OP4 functioning as a voltage follower. The combination of the operational amplifier OP3 and the transistor MP1 also constitutes a voltage follower.

In the peak hold circuit 2, a transistor is activated by a reset signal RST (see FIG. 26) generated at the timing of switching the pass band (switching timing of the switch signals M1 to Mn) of the bandpass filter circuit 1 shown in FIG. By temporarily turning on MN1, the electric charge of the capacitor Cp accumulated so far is discharged. Thereafter, the output signal of the band-pass filter circuit 1 is input to the inverting input terminal (IN) of the operational amplifier PO3.
Rises, the output voltage decreases in accordance with the voltage, the conduction degree of the transistor MP1 increases, and the charge to the capacitor Cp is accelerated, so that the inverting input terminal is connected to the capacitor Cp. , A voltage corresponding to the voltage applied to is generated. And the capacitor C
When the voltage level of p becomes higher than the level of the voltage applied to its inverting input terminal, the output voltage of the operational amplifier OP3 changes in a direction to increase, so that the conductivity of the transistor MP1 decreases and the charging current to the capacitor Cp decreases. Is reduced. Thus, the capacitor Cp is charged with the voltage corresponding to the peak value of the voltage input to the inverting input terminal, and is held until reset. Resistance R1,
R2 is for preventing overshoot of the charging current to the capacitor Cp.

FIG. 24 is a block diagram showing the internal configuration of the control unit 3. An A / D converter 301 converts a peak hold signal output from the peak hold circuit 2 into a digital signal. A control unit 302 includes a microcomputer. The control unit 302 takes in the digital signal obtained by the A / D converter 301 and converts the digital signal into data for display, and the switch signal M1 for the band-pass filter circuit 1 described above. , Mn, the operation clocks φ1, φ2, the reset signal RST of the peak hold circuit 2, and the like.

[0012]

As described above, in the conventional switched-capacitor bandpass filter circuit 1, the number n of passing frequencies is determined by the operational amplifiers OP1 and OP1.
The number is determined by the number of capacitors connected to 2, for example, in the case of 5 bands, n = 5. In the operational amplifier OP1, five capacitors C11 to C15 are cyclically switched, and in the operational amplifier OP2, five capacitors C21 to C21 are switched. C25 is cyclically switched.

In order to detect the signal level of the passing frequency by the band-pass filter circuit 1, a measurement period of at least one cycle of the signal of the frequency is required. Become. Moreover, as the number of passing frequencies measured by one device increases, the number of capacitors switched and connected to the operational amplifiers OP1 and OP2 increases accordingly, and the measurement time (cycle) for measuring signals of all passing frequencies increases Is considerably longer.

For example, as shown in FIG. 27, the measurement time when measuring the signal levels of five (n = 5) passing frequencies with one measuring device (provided that the measurement time of each frequency is the same) ) Is T, twice as many as 10 (n = 10)
In order to measure the signal level of the passing frequency, it is necessary to double the signal measurement time to 2T. For this reason, the measurement cycle becomes longer, and the spectrum of each pass frequency is displayed sequentially instead of being displayed simultaneously, and the spectrum display becomes unnatural. However, if this measurement time is shortened, there arises a problem that a low-frequency signal cannot be accurately measured.

The present invention has been made in view of the above points, and an object of the present invention is to shorten the time required for measuring all frequencies even when the number of passing frequencies whose signal levels are to be measured is increased. An object of the present invention is to provide a signal spectrum measuring device capable of performing accurate measurement even in a low frequency range.

[0016]

According to a first aspect of the present invention, there is provided a switched capacitor type band pass filter circuit for sequentially switching three pass bands cyclically and outputting frequency signals of the respective pass bands in a time division manner. A peak-and-hold circuit for detecting a peak value of a frequency signal in each pass band of the band-pass filter circuit and sequentially and cyclically holding the peak value, wherein a combination of the band-pass filter circuit and the peak-hold circuit is provided. Are provided with the same circuit constant configuration, the same signal is input to the two band-pass filter circuits, and the frequency of the operation clock of one band-pass filter circuit is changed to the frequency of the operation clock of the other band-pass filter circuit. It was configured to be about 0.3 times, and the signals obtained from the two peak hold circuits were used as spectrum signals.

According to a second aspect of the present invention, in the first aspect, when three pass frequencies of the other band-pass filter circuit, which are sequentially and cyclically switched, are defined as f1 to f3, the relationship between the frequencies f1 to f3 is represented by fn. ≒ 10 ^{n− 1} · f1 (where n = 1 to 3).

According to a third aspect of the present invention, there is provided a switched-capacitor band-pass filter circuit for sequentially switching four pass bands cyclically and outputting frequency signals of the respective pass bands in a time-division manner, and the band-pass filter circuit. In the signal spectrum measuring device having a peak hold circuit that detects a peak value of the frequency signal of each pass band and sequentially and cyclically holds the peak value, a set of the band pass filter circuit and the peak hold circuit has the same circuit constant. The same signal is input to both band-pass filter circuits, and the frequency of the operation clock of one band-pass filter circuit is set to about 0.4 times the frequency of the operation clock of the other band-pass filter circuit. The signals obtained from the two peak hold circuits are configured to be spectrum signals.

In a fourth aspect based on the third aspect, when four pass frequencies of the other band-pass filter circuit, which are sequentially and cyclically switched, are defined as f1 to f4, the relationship between the frequencies f1 to f4 is represented by fn. ≒ 5 ^{n− 1} · f1 (where n = 1 to 4).

According to a fifth aspect of the present invention, there is provided a switched-capacitor band-pass filter circuit for sequentially and cyclically switching five pass bands and outputting frequency signals of the respective pass bands in a time-division manner, and the band-pass filter circuit. In the signal spectrum measuring device having a peak hold circuit that detects a peak value of the frequency signal of each pass band and sequentially and cyclically holds the peak value, a set of the band pass filter circuit and the peak hold circuit has the same circuit constant. The same signal is input to both band-pass filter circuits, and the frequency of the operation clock of one band-pass filter circuit is set to about 0.5 times the frequency of the operation clock of the other band-pass filter circuit. The signals obtained from the two peak hold circuits are configured to be spectrum signals.

According to a sixth aspect of the present invention, in the fifth aspect, when five pass frequencies of the other band-pass filter circuit, which are sequentially and cyclically switched, are defined as f1 to f5, the relationship between the frequencies f1 to f5 is represented by fn. ≒ 4 ^{n− 1} · f1 (where n = 1 to 5).

According to a seventh aspect of the present invention, there is provided a switched-capacitor band-pass filter circuit for sequentially and cyclically switching six pass bands and outputting a frequency signal of each pass band in a time-division manner, and the band-pass filter circuit. In the signal spectrum measuring device having a peak hold circuit that detects a peak value of the frequency signal of each pass band and sequentially and cyclically holds the peak value, a set of the band pass filter circuit and the peak hold circuit has the same circuit constant. The same signal is input to both band-pass filter circuits, and the frequency of the operation clock of one band-pass filter circuit is set to about 0.6 times the frequency of the operation clock of the other band-pass filter circuit. The signals obtained from the two peak hold circuits are configured to be spectrum signals.

In an eighth aspect based on the seventh aspect, when six pass frequencies of the other band-pass filter circuit, which are sequentially and cyclically switched, are defined as f1 to f6, the relationship between the frequencies f1 to f6 is represented by fn. ≒ 3 ^{n− 1} · f1 (where n = 1 to 6).

A ninth invention is a switched-capacitor band-pass filter circuit for sequentially switching seven pass-bands cyclically and outputting frequency signals of the respective pass-bands in a time-division manner, and the band-pass filter circuit In the signal spectrum measuring device having a peak hold circuit that detects a peak value of the frequency signal of each pass band and sequentially and cyclically holds the peak value, a set of the band pass filter circuit and the peak hold circuit has the same circuit constant. And the same signal is input to both band-pass filter circuits, and the frequency of the operation clock of one band-pass filter circuit is set to about ２ times the frequency of the operation clock of the other band-pass filter circuit. The signals obtained from the two peak hold circuits are configured to be spectrum signals.

According to a tenth aspect, in the ninth aspect, when seven pass frequencies of the other band-pass filter circuit, which are sequentially and cyclically switched, are defined as f1 to f7, the relationship between the frequencies f1 to f7 is represented by fn. ≒ (5/2) ^{n− 1} · f1 (where n = 1 to 7).

[0026]

BEST MODE FOR CARRYING OUT THE INVENTION

[First Embodiment] First, a switched capacitor type bandpass filter circuit 1 as shown in FIG.
When the frequency fc of the operation clocks φ1 and φ2 is changed, the pass frequency selected there changes in proportion to the clock frequency fc. Also, the operational amplifiers OP1,
When the capacitance value of the feedback capacitor connected to OP2 is constant, if the clock frequency fc becomes, for example, １ ／, the passing frequency also becomes １ ／. The present embodiment utilizes this.

FIG. 1 is a diagram showing a configuration of a signal spectrum measuring apparatus according to the first embodiment. 11A indicates that the frequency switching number is 3 (that is, the switch signal in FIG.
1 to M3), a switched capacitor type band-pass filter circuit, 12A is a peak hold circuit (the same configuration as that shown in FIG. 23), and these constitute a first measurement circuit 10A. Similarly, 11B is a switched-capacitor band-pass filter circuit having a frequency switching number of 3 (switch signals are M1 'to M3'), the same configuration and the same circuit constants as the above-described band-pass filter circuit 11A, and 12B. Is the peak hold circuit 1 described above.
This is a peak hold circuit having the same configuration and the same circuit constant as 2A, and these constitute a second measurement circuit 10B. The same audio signal is input to both of the measurement circuits 10A and 10B, and the output signal is output to the control unit 13. Display signals output from the control unit 13 are displayed on six liquid crystal display devices for frequency spectrum (not shown) via display drivers (not shown).

The switch signals M1 to M3 for the bandpass filter circuit 11A and the switch signals M1 'to M3' for the bandpass filter circuit 11B are shown in FIG.
(The timing relationship is not the same). The frequency of the operation clocks φ1 and φ2 of the bandpass filter circuit 11A is fc, and the frequency of the operation clocks φ1 ′ and φ2 ′ of the bandpass filter circuit 11B is 0.3fc. Further, the reset signal RST of the peak hold circuit 12A and the reset signal RST ′ of the peak hold circuit 12B have a phase relationship shifted as shown in FIG.

In this embodiment, each measuring device 10A,
Assuming that the number of passing frequencies in 10B is 3, in the first measuring device 10A, the frequency f1 is set in the switch signal M1, the frequency f2 is set in the switch signal M2, and the frequency f3 is set in the switch signal M3. These frequencies f1 to f3 are set so that fn ≒ 10 ^{n− 1} · f1 (where n = 1 to 3) (2).

In the second measuring device 10B, the frequency f1 'is set by the switch signal M1', the frequency f2 'is set by the switch signal M2', and the frequency f3 'is set by the switch signal M3'.

Here, as described above, the frequency fc of the operation clocks φ1 and φ2 of the bandpass filter circuit 11A is set.
On the other hand, since the frequency of the operation clocks φ1 ′ and φ2 ′ of the bandpass filter circuit 11B is 0.3fc, the bandpass filter circuit
The pass frequency fn of A and the pass frequency fn 'of the band-pass filter circuit 11B set by the switch signal Mn' have the following relationship. fn '= 0.3fn (where n = 1 to 3) (3)

From the above, if the pass frequency f1 of the first measuring device 10A is set to f1 = 100 Hz, from the above-mentioned equation (2), as shown in FIG.
3 = 10 KHz, and accordingly, from equation (3), the pass frequency of the second measuring device 10B is f1 ′ = 30 Hz,
f2 '= 300 Hz and f3' = 3 KHz. The relationship between the respective pass frequencies is f1 ′ <f1 <f2 ′ <f
2 <f3 ′ <f3, and these are arranged at substantially equal intervals (logarithms) on the frequency axis.

As described above, in the present embodiment, the number of pass frequencies measured in one cycle in each of the measuring devices 10A and 10B is set to 3, and these are measured in parallel. Therefore, the number of all pass frequencies is doubled. In spite of the above, as shown in FIG. 3, the measurement time of one cycle can be substantially set within the measurement time of three pass frequencies.

In the first embodiment, the switch signals M1 'to M3' for the switch signals M1 to M3 are provided.
, The reset signal RS for the reset signal RST
Since the phases of T ′ are shifted by π, the total measurement time is 1.17T.
M3, the common reset signal RST is sent to both measuring devices 10A,
10B, the two measuring devices 10A and 10B output two spectral signals at the same timing, so that the total measuring time becomes T. In this case, the control unit 13 may shift the spectrum signals temporally from each other to be display signals.

As described above, all the acquired frequency spectrum data can be displayed within the measurement time of one cycle of one of the band-pass filter circuits, so that the display is prevented from becoming unnatural. can do. Further, since it is not necessary to shorten the measurement time of one pass frequency, the measurement accuracy particularly in a low frequency range does not decrease.

[Second Embodiment] FIG. 5 is a diagram showing a configuration of a signal spectrum measuring apparatus according to a second embodiment. 21A is a switched-capacitor band-pass filter circuit whose frequency switching number is 4 (that is, the switch signals are M1 to M4 in FIG. 22), 22A is a peak hold circuit (the same configuration as that shown in FIG. 23), These constitute a first measurement circuit 20A. Similarly, 21B is a switched-capacitor band-pass filter circuit having a frequency switching number of 4 (switch signals are M1 'to M4'), the same configuration and the same circuit constants as the above-described band-pass filter circuit 21A, and 22B. Is a peak hold circuit having the same configuration and the same circuit constant as the above-described peak hold circuit 22A, and these constitute a second measurement circuit 20B. The same audio signal is input to both of the measurement circuits 20A and 20B, and the output signal is output to the control unit 23. The display signal output from the control unit 23 is displayed on eight frequency spectrum liquid crystal display devices (not shown) via a display driver (not shown).

The switch signals M1 to M4 for the bandpass filter circuit 21A and the switch signals M1 'to M4' for the bandpass filter circuit 21B are shown in FIG.
(The timing relationship is not the same). The frequency of the operation clocks φ1 and φ2 of the bandpass filter circuit 21A is fc, and the frequency of the operation clocks φ1 ′ and φ2 ′ of the bandpass filter circuit 21B is 0.4fc. Further, the reset signal RST of the peak hold circuit 22A and the reset signal RST ′ of the peak hold circuit 22B have a phase relationship shifted as shown in FIG.

In this embodiment, each measuring device 20A,
Assuming that the number of passing frequencies in 20B is 4, in the first measuring device 20A, the frequency f1 of the switch signal M1, the frequency f2 of the switch signal M2, the frequency f3 of the switch signal M3, the frequency f4 of the switch signal M4, These frequencies f1 to f4 are set so that fn ≒ 5 ^{n− 1} · f1 (where n = 1 to 4) (4).

In the second measuring device 20B, the frequency f1 'of the switch signal M1', the frequency f2 'of the switch signal M2', the frequency f3 'of the switch signal M3', and the frequency f4 'of the switch signal M4'. , Respectively.

Here, as described above, the frequency fc of the operation clocks φ1 and φ2 of the band-pass filter circuit 21A is used.
In contrast, since the frequency of the operation clocks φ1 ′ and φ2 ′ of the bandpass filter circuit 21B is 0.4 fc, the bandpass filter circuit 21B set by the switch signal Mn
The pass frequency fn of A and the pass frequency fn 'of the band-pass filter circuit 21B set by the switch signal Mn' have the following relationship. fn '= 0.4fn (where n = 1 to 4) (5)

From the above, if the pass frequency f1 of the first measuring device 20A is set to f1 = 100 Hz, as shown in FIG.
f3 = 2.5 KHz, f4 = 12.5 KHz, and accordingly, from Expression (5), the passing frequencies of the second measuring device 20B are f1 ′ = 40 Hz, f2 ′ = 200 Hz, f
3 ′ = 1 KHz and f4 ′ = 5 KHz. The relationship between the passing frequencies is f1 ′ <f1 <f2 ′ <f2 <f
3 ′ <f3 <f4 ′ <f4, and these are arranged at substantially equal intervals (logarithms) on the frequency axis.

As described above, in the present embodiment, the number of passing frequencies measured in one cycle in each of the measuring devices 20A and 20B is set to 4 and measured in parallel, so that the number of all passing frequencies is doubled. 7, the measurement time of one cycle can be substantially set within the measurement time of the pass frequency of 4, as shown in FIG.

In the second embodiment, the switch signals M1 'to M4' for the switch signals M1 to M4 are provided.
, The reset signal RS for the reset signal RST
Since the phases of T ′ are shifted by π, the total measurement time is 1.13T.
M4, the common reset signal RST is applied to both measuring devices 20A,
20B, the two measurement devices 20A and 20B output two spectrum signals at the same timing, so that the total measurement time becomes T. In this case, in the control unit 23, the spectrum signals may be shifted from each other with respect to time and used as display signals.

As described above, also in the second embodiment, the display of all the fetched frequency spectrum data can be performed within the measurement time of approximately one cycle of one of the band-pass filter circuits. The display can be prevented from becoming unnatural. Also,
Since it is not necessary to reduce the measurement time of one pass frequency, the measurement accuracy especially in a low frequency range does not decrease.

[Third Embodiment] FIG. 9 is a diagram showing a configuration of a signal spectrum measuring apparatus according to a third embodiment. 31A is a switched-capacitor band-pass filter circuit having five switching frequencies (that is, the switching signals are M1 to M5 in FIG. 22), and 32A is a peak hold circuit (same configuration as that shown in FIG. 23). These form a first measurement circuit 30A.
Similarly, 31B is a switched-capacitor band-pass filter circuit having the same number and the same circuit constant as the above-described band-pass filter circuit 31A, having the number of switching of the pass frequency is 5 (the switch signal is M1 'to M5'). 32B is a peak hold circuit having the same configuration and the same circuit constant as the above-described peak hold circuit 32A.
Of the measuring circuit 30B. The same audio signal is input to both of the measuring circuits 30A and 30B.
The output signal is output to the control unit 33. The display signal output from the control unit 33 is displayed on ten liquid crystal display devices (not shown) for displaying a frequency spectrum via a display driver (not shown).

The switch signals M1 to M5 for the bandpass filter circuit 31A and the switch signals M1 'to M5' for the bandpass filter circuit 31B are shown in FIG.
There is a phase relationship as shown in FIG. The frequency of the operation clocks φ1 and φ2 of the bandpass filter circuit 31A is fc, and the frequency of the operation clocks φ1 ′ and φ2 ′ of the bandpass filter circuit 31B is 0.5fc. Further, the reset signal RST of the peak hold circuit 32A and the reset signal RST ′ of the peak hold circuit 32B have a phase relationship shifted as shown in FIG.

In this embodiment, each measuring device 30A,
Assuming that the number of passing frequencies in 30B is 5, in the first measuring device 30A, the frequency f1 of the switch signal M1, the frequency f2 of the switch signal M2, the frequency f3 of the switch signal M3, the frequency f4 of the switch signal M4, The frequency f5 is set by the switch signal M5, and these frequencies f1 to f5 are set so that fn ≒ 4n ^{− 1} · f1 (where n = 1 to 5) (6) Set.

In the second measuring device 30B, the frequency f1 'of the switch signal M1', the frequency f2 'of the switch signal M2', the frequency f3 'of the switch signal M3', and the frequency f4 'of the switch signal M4' are obtained. , Switch signal M5 '
And the frequency f5 ′ is set respectively.

Here, as described above, the frequencies fc of the operation clocks φ1 and φ2 of the band-pass filter circuit 31A are set.
In contrast, since the frequency of the operation clocks φ1 ′ and φ2 ′ of the band-pass filter circuit 31B is 0.5 fc, the band-puffer filter circuit 3 set by the switch signal Mn
1A and the pass frequency fn 'of the band-puffer filter circuit 31B set by the switch signal Mn'.
Has the following relationship. fn '= 0.5fn (where n = 1 to 5) (7)

From the above, if the pass frequency f1 of the first measuring device 30A is set to f1 = 63 Hz, as shown in FIG. 12, f2 = 250 Hz as shown in FIG.
f3 = 1 KHz, f4 = 4 KHz, and f5 = 16 KHz. Accordingly, from the equation (7), the second measuring device 30
The passing frequency of B is f1 '= 31.5 Hz, f2' = 12
5Hz, f3 '= 500Hz, f4' = 2KHz, f
5 ′ = 8 KHz. The relationship between the passing frequencies is f1 ′ <f1 <f2 ′ <f2 <f3 ′ <f3 <f
4 ′ <f4 <f5 ′ <f5, and these are arranged at substantially equal intervals (logarithms) on the frequency axis.

As described above, in the present embodiment, the number of pass frequencies measured in one cycle in each of the measuring devices 30A and 30B is set to 5 and the pass frequencies are measured in parallel. In spite of the doubling of 10, the measurement time of one cycle can be substantially set within the measurement time of five pass frequencies, as shown in FIG.

In the third embodiment, the switch signals M1 'to M5' for the switch signals M1 to M5 are used.
, The reset signal RS for the reset signal RST
Since the phases of T ′ are shifted by π, the total measurement time is 1.1T, but the common switch signals M1 to M
5. The common reset signal RST is applied to both measuring devices 30A, 3
0B, and the two measuring devices 30A and 30B output two spectral signals at the same timing, the total measuring time becomes T. In this case, in the control unit 33, the spectrum signals may be temporally shifted from each other to be display signals.

As described above, also in the third embodiment, the display of all the fetched frequency spectrum data can be performed within the measurement time of approximately one cycle of one of the band-pass filter circuits. The display can be prevented from becoming unnatural. Also,
Since it is not necessary to reduce the measurement time of one pass frequency, the measurement accuracy especially in a low frequency range does not decrease.

[Fourth Embodiment] FIG. 13 is a diagram showing a configuration of a signal spectrum measuring apparatus according to a fourth embodiment. Reference numeral 41A denotes a switched-capacitor band-pass filter circuit having six switching frequencies (that is, switch signals M1 to M6 in FIG. 22), and reference numeral 42A denotes a peak hold circuit (the same configuration as that shown in FIG. 22). These form a first measurement circuit 40A.
Similarly, 41B is a switched-capacitor band-pass filter circuit having the same frequency and the same circuit constant as the above-described band-pass filter circuit 41A, having the same number of switching of the passing frequency as 6 (switch signals are M1 'to M6'). Reference numeral 42B denotes a peak hold circuit having the same configuration and the same circuit constant as the above-described peak hold circuit 42A.
Of the measurement circuit 40B. The same audio signal is input to both of the measurement circuits 40A and 40B,
The output signal is output to the control unit 43. The display signal output from the control unit 43 is displayed on 12 liquid crystal display devices (not shown) for displaying a frequency spectrum via a display driver (not shown).

The switch signals M1 to M6 for the bandpass filter circuit 41A and the switch signals M1 'to M6' for the bandpass filter circuit 41B are shown in FIG.
4 (the timing relationship is not the same). The frequency of the operation clocks φ1 and φ2 of the bandpass filter circuit 41A is fc, and the frequency of the operation clocks φ1 ′ and φ2 ′ of the bandpass filter circuit 41B is 0.6fc. Further, the reset signal RST of the peak hold circuit 42A and the reset signal RST 'of the peak hold circuit 42B have a phase relationship shifted as shown in FIG.

In this embodiment, each measuring device 40A,
Assuming that the number of passing frequencies in 40B is 6, in the first measuring device 40A, the frequency f1 is the switch signal M1, the frequency f2 is the switch signal M2, the frequency f3 is the switch signal M3, and the frequency f4 is the switch signal M4. The frequency f5 is set by the switch signal M5, and the frequency f6 is set by the switch signal M6.
1 to f6 are set so that fn ≒ 3 ^{n− 1} · f1 (where n = 1 to 6) (8).

In the second measuring device 40B, the frequency f1 'of the switch signal M1', the frequency f2 'of the switch signal M2', the frequency f3 'of the switch signal M3', and the frequency f4 'of the switch signal M4'. , Switch signal M5 '
And the frequency f5 'with the switch signal M6'.
Are set respectively.

Here, as described above, the frequency fc of the operation clocks φ1 and φ2 of the band-pass filter circuit 41A is set.
On the other hand, since the frequency of the operation clocks φ1 ′ and φ2 ′ of the bandpass filter circuit 41B is 0.6 fc, the bandpass filter circuit 41 set by the switch signal Mn
The pass frequency fn of A and the pass frequency fn 'of the band-pass filter circuit 41B set by the switch signal Mn' have the following relationship. fn ′ = 0.6fn (where n = 1 to 6) (9)

From the above, if the pass frequency f1 of the first measuring device 40A is set to f1 = 63 Hz, as shown in FIG. 15, f2 = 189 Hz, as shown in FIG.
f3 = 567 Hz, f4 = 1.7 KHz, f5 = 5.1
KHz, f6 = 16.3 KHz, and accordingly, from equation (9), the pass frequency f1 ′ of the second measuring device 40B is obtained.
= 38Hz, f2 '= 113Hz, f3' = 340H
z, f4 '= 1 KHz, f5' = 3 KHz, f6 '= 1
It becomes 0 KHz. The relationship between the respective pass frequencies is f
1 ′ <f1 <f2 ′ <f2 <f3 ′ <f3 <f4 ′ <f
4 <f5 ′ <f5 <f6 ′ <f6, and these are arranged at substantially equal intervals (logarithms) on the frequency axis.

As described above, in the present embodiment, the number of pass frequencies measured in one cycle in each of the measuring devices 40A and 40B is set to 6, and these are measured in parallel. Despite doubling to 12, as shown in FIG. 14, the measurement time of one cycle can be substantially set within the measurement time of six pass frequencies.

In the fourth embodiment, the switch signals M1 'to M6' for the switch signals M1 to M6 are provided.
, The reset signal RS for the reset signal RST
Since the phases of T ′ are shifted by π, the total measurement time is 1.08T.
M6, the common reset signal RST is sent to both measuring devices 40A,
The total measurement time is T when the two measurement devices 40A and 40B output two spectrum signals at the same timing. In this case, in the control unit 43, the spectrum signals may be shifted from each other with respect to time and used as display signals.

As described above, also in the fourth embodiment, the display of all the fetched frequency spectrum data can be performed within the measurement time of approximately one cycle of one of the band-pass filter circuits. The display can be prevented from becoming unnatural. Also,
Since it is not necessary to reduce the measurement time of one pass frequency, the measurement accuracy especially in a low frequency range does not decrease.

[Fifth Embodiment] FIG. 17 is a diagram showing a configuration of a signal spectrum measuring apparatus according to a fifth embodiment. Reference numeral 51A denotes a switched-capacitor band-pass filter circuit in which the number of switching of the passing frequency is 7 (that is, the switch signals are M1 to M7 in FIG. 22), and 52A denotes a peak hold circuit (the same configuration as that shown in FIG. 23). These form a first measurement circuit 50A.
Similarly, 51B is a switched-capacitor type band-pass filter circuit having the same frequency and the same circuit constant as the above-described band-pass filter circuit 51A, having the same number of switching frequencies of 7 (switch signals are M1 'to M7'). 52B is a peak hold circuit having the same configuration and the same circuit constant as the above-mentioned peak hold circuit 52A.
Of the measurement circuit 50B. The same audio signal is input to both of the measuring circuits 50A and 50B.
The output signal is output to the control unit 53. The display signal output from the control unit 53 is displayed on 14 liquid crystal display devices (not shown) for displaying a frequency spectrum via a display driver (not shown).

Switch signals M1 to M7 for bandpass filter circuit 51A and bandpass filter circuit 51B
Have a phase relationship (timing relationship that is not the same) as shown in FIG. The frequency of the operation clocks φ1 and φ2 of the bandpass filter circuit 51A is fc,
The frequency of the 1B operation clocks φ1 ′ and φ2 ′ is (2 /
3) fc. Further, the reset signal RST of the peak hold circuit 52A and the reset signal RST 'of the peak hold circuit 52B have a phase relationship shifted as shown in FIG.

In this embodiment, each measuring device 50A,
Assuming that the number of passing frequencies in 50B is 7, in the first measuring device 50A, the frequency f1 is the switch signal M1, the frequency f2 is the switch signal M2, the frequency f3 is the switch signal M3, and the frequency f4 is the switch signal M4. The frequency f5 is set by the switch signal M5, the frequency f6 is set by the switch signal M6, and the frequency f7 is set by the switch signal M7, so that these bands f1 to f7 are set as fn ≒ (2/5) ^{n- 1.} · F1 (where n = 1 to 7) ··· (10)

In the second measuring device 50B, the frequency f1 'is generated by the switch signal M1', the frequency f2 'is generated by the switch signal M2', the frequency f3 'is generated by the switch signal M3', and the frequency f4 'is generated by the switch signal M4'. , Switch signal M5 '
And the frequency f5 'with the switch signal M6'.
However, the frequency f7 'is set by the switch signal M7'.

Here, as described above, the frequency fc of the operation clocks φ1 and φ2 of the band-pass filter circuit 51A is set.
On the other hand, since the frequencies of the operation clocks φ1 ′ and φ2 ′ of the bandpass filter circuit 51B are (２) fc, the pass frequency fn of the bandpass filter circuit 51A set by the switch signal Mn and the switch signal Mn ', The pass frequency f of the band-pass filter circuit 51B
n 'has the following relationship. fn '= (2/3) fn (where n = 1 to 7) (11)

From the above, if the pass frequency f1 of the first measuring device 50A is set to f1 = 63 Hz, from the above equation (10), as shown in FIG. 20, f2 = 160H
z, f3 = 400 Hz, f4 = 1 KHz, f5 = 2.5
KHz, f6 = 6.3 KHz, f7 = 16 KHz, and accordingly, from the equation (11), the second measuring device 50
The passing frequency of B is f1 '= 42 Hz, f2' = 105H
z, f3 '= 270 Hz, f4' = 670 Hz, f5 '
= 1.65 KHz, f6 ′ = 4.2 KHz, f7 ′ = 1
0.7 KHz. And the relationship between each pass frequency is
f1 ′ <f1 <f2 ′ <f2 <f3 ′ <f3 <f4 ′ <
f4 <f5 '<f5 <f6'<f6<f7'<f7, and these are arranged at substantially equal intervals (logarithms) on the frequency axis.

As described above, in the present embodiment, the number of pass frequencies measured in one cycle in each of the measuring devices 50A and 50B is set to 7, and the pass frequencies are measured in parallel. Despite doubling to 14, as shown in FIG. 19, the measurement time of one cycle can be substantially set within the measurement time of seven pass frequencies.

In the fifth embodiment, the switch signals M1 'to M7' for the switch signals M1 to M7 are used.
, The reset signal RS for the reset signal RST
Since the phases of T ′ are shifted by π, the total measurement time is 1.07T.
M7, the common reset signal RST is applied to both measuring devices 50A,
When the signal is supplied to the measuring device 50B and the two measuring devices 50A and 50B output two spectral signals at the same timing, the total measuring time becomes T. In this case, in the control unit 53, the spectrum signals may be shifted from each other with respect to time to be display signals.

As described above, also in the fifth embodiment, the display of all the fetched frequency spectrum data can be performed within the measurement time of approximately one cycle of one of the band-pass filter circuits. The display can be prevented from becoming unnatural. Also,
Since it is not necessary to reduce the measurement time of one pass frequency, the measurement accuracy especially in a low frequency range does not decrease.

[Other Embodiments] The first embodiment described above
In the fifth to fifth embodiments, one type of frequency setting has been described. However, if the frequency f1 initially determined is set a little higher, all the passing frequencies are shifted to the higher frequency side, and if the frequency f1 is set lower, the lower frequency is set. Since the frequency shifts to the frequency side, the distribution of a plurality of passing frequencies can be balanced by appropriately setting the frequency f1.

When two sets of a band pass filter circuit and a peak hold circuit are configured, one set is set as a master and the other set as a slave, and a switch signal, a reset signal, an operation clock, and the like are generated on the master side. A circuit may be provided to supply a switch signal or a reset signal having the same or shifted phase from the master side to the slave side, and to supply an operation clock whose frequency is adjusted.

[0074]

As described above, according to the present invention, it is possible to obtain spectrum data of a large number of passing frequency signals in a short time, and to display the spectrum data naturally. At this time, the measurement accuracy of the low-pass frequency does not decrease.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a spectrum measuring device according to a first embodiment of the present invention.

FIG. 2 is a waveform diagram of a switch signal and a reset signal of the spectrum measuring apparatus according to the embodiment.

FIG. 3 is an explanatory diagram of distribution of successive switching frequencies of the spectrum measuring device of the embodiment.

FIG. 4 is an explanatory diagram of spectrum frequency distribution of the spectrum measuring apparatus of the embodiment.

FIG. 5 is a block diagram illustrating a configuration of a spectrum measurement device according to a second embodiment of the present invention.

FIG. 6 is a waveform chart of a switch signal and a reset signal of the spectrum measuring apparatus of the embodiment.

FIG. 7 is an explanatory diagram of distribution of successive switching frequencies of the spectrum measuring apparatus of the embodiment.

FIG. 8 is an explanatory diagram of spectrum frequency distribution of the spectrum measuring apparatus according to the embodiment.

FIG. 9 is a block diagram illustrating a configuration of a spectrum measuring apparatus according to a third embodiment of the present invention.

FIG. 10 is a waveform chart of a switch signal and a reset signal of the spectrum measuring apparatus of the embodiment.

FIG. 11 is an explanatory diagram of distribution of successive switching frequencies of the spectrum measuring apparatus according to the embodiment.

FIG. 12 is an explanatory diagram of spectrum frequency distribution of the spectrum measuring apparatus of the embodiment.

FIG. 13 is a block diagram illustrating a configuration of a spectrum measuring apparatus according to a fourth embodiment of the present invention.

FIG. 14 is a waveform chart of a switch signal and a reset signal of the spectrum measuring apparatus of the embodiment.

FIG. 15 is an explanatory diagram of distribution of successive switching frequencies of the spectrum measuring apparatus according to the embodiment.

FIG. 16 is an explanatory diagram of distribution of spectrum frequencies of the spectrum measuring apparatus according to the embodiment.

FIG. 17 is a block diagram illustrating a configuration of a spectrum measuring apparatus according to a fifth embodiment of the present invention.

FIG. 18 is a waveform chart of a switch signal and a reset signal of the spectrum measuring apparatus of the embodiment.

FIG. 19 is an explanatory diagram of distribution of successive switching frequencies of the spectrum measuring device of the embodiment.

FIG. 20 is an explanatory diagram of distribution of spectrum frequencies of the spectrum measuring apparatus of the embodiment.

FIG. 21 is a block diagram showing a configuration of a conventional spectrum measuring device.

FIG. 22 is a circuit diagram of a switched capacitor type bandpass filter circuit.

FIG. 23 is a circuit diagram of a peak hold circuit.

FIG. 24 is a block diagram illustrating a configuration of a control unit.

FIG. 25 is a waveform diagram of an operation clock.

FIG. 26 is a waveform diagram of a switch signal and a reset signal of a conventional spectrum measuring device.

FIG. 27 is an explanatory diagram of a switching frequency of a conventional spectrum measuring device.

Claims (10)

[Claims] 1. A switched-capacitor band-pass filter circuit for sequentially and cyclically switching three pass bands and outputting frequency signals of the respective pass bands in a time-division manner, and each pass band of the band-pass filter circuit And a peak hold circuit for sequentially and cyclically detecting and holding the peak value of the frequency signal of the frequency spectrum signal, wherein two sets of the band-pass filter circuit and the peak hold circuit are provided with the same circuit constant configuration. Then, the same signal is input to both the band-pass filter circuits, and the frequency of the operation clock of one band-pass filter circuit is set to about 0.
3. A signal spectrum measuring apparatus, wherein the signal is tripled and a signal obtained from the two peak hold circuits is used as a spectrum signal. 2. When three pass frequencies f1 to f3 of the other band-pass filter circuit which are sequentially and cyclically switched are defined as f1 to f3, the relationship between the frequencies f1 to f3 is represented by fn ≒ 10 ^{n− 1} · f1 (where, 2. The signal spectrum measuring apparatus according to claim 1, wherein n = 1 to 3). 3. A switched-capacitor bandpass filter circuit for sequentially and cyclically switching four passbands and outputting a frequency signal of each passband in a time-division manner, and each passband of the bandpass filter circuit. And a peak hold circuit for sequentially and cyclically detecting and holding the peak value of the frequency signal of the frequency spectrum signal. Then, the same signal is input to both the band-pass filter circuits, and the frequency of the operation clock of one band-pass filter circuit is set to about 0.
A signal spectrum measuring apparatus, wherein the signal is quadrupled, and a signal obtained from the two peak hold circuits is a spectrum signal. 4. When the four pass frequencies of the other band-pass filter circuit, which are sequentially and cyclically switched, are defined as f1 to f4, the relationship between the frequencies f1 to f4 is expressed as fn ≒ 5 ^{n− 1} · f1 (where, 4. The signal spectrum measuring apparatus according to claim 3, wherein n = 1 to 4). 5. A switched-capacitor bandpass filter circuit for sequentially switching five passbands cyclically and outputting frequency signals of the respective passbands in a time-division manner, and each passband of the bandpass filter circuit. And a peak hold circuit for sequentially and cyclically detecting and holding the peak value of the frequency signal of the frequency spectrum signal. Then, the same signal is input to both band-pass filter circuits, and the frequency of the operation clock of one band-pass filter circuit is set to about 0.
5. A signal spectrum measuring apparatus, wherein the signal is obtained by multiplying by 5 and a signal obtained from the two peak hold circuits is used as a spectrum signal. 6. When five pass frequencies f1 to f5 of the other bandpass filter circuit which are sequentially and cyclically switched are defined as f1 to f5, the relationship between the frequencies f1 to f5 is represented by fn ≒ 4 ^{n− 1} · f1 (where, The signal spectrum measuring apparatus according to claim 5, wherein n = 1 to 5). 7. A switched-capacitor band-pass filter circuit for sequentially switching six pass-bands cyclically and outputting frequency signals of the respective pass-bands in a time-division manner, and each pass-band of the band-pass filter circuit And a peak hold circuit for sequentially and cyclically detecting and holding the peak value of the frequency signal of the frequency spectrum signal, wherein two sets of the band-pass filter circuit and the peak hold circuit are provided with the same circuit constant configuration. Then, the same signal is input to both the band-pass filter circuits, and the frequency of the operation clock of one band-pass filter circuit is set to about 0.
A signal spectrum measuring apparatus, wherein the signal is obtained by a factor of 6, and the signals obtained from the two peak hold circuits are used as spectrum signals. 8. When six pass frequencies of the other band-pass filter circuit, which are sequentially and cyclically switched, are defined as f1 to f6, the relationship between the frequencies f1 to f6 is represented by fn ≒ 3 ^{n− 1} · f1 (where, The signal spectrum measuring apparatus according to claim 7, wherein n = 1 to 6). 9. A switched-capacitor band-pass filter circuit for sequentially and cyclically switching seven pass bands and time-divisionally outputting frequency signals of the respective pass bands, and each pass band of the band-pass filter circuit. And a peak hold circuit for sequentially and cyclically detecting and holding the peak value of the frequency signal of the frequency spectrum signal, wherein two sets of the band-pass filter circuit and the peak hold circuit are provided with the same circuit constant configuration. Then, the same signal is input to the two band-pass filter circuits, and the frequency of the operation clock of one of the band-pass filter circuits is set to about ／ of the frequency of the operation clock of the other band-pass filter circuit.
3. A signal spectrum measuring apparatus, wherein the signal is tripled and a signal obtained from the two peak hold circuits is used as a spectrum signal. 10. When the seven pass frequencies of the other band-pass filter circuit, which are sequentially and cyclically switched, are defined as f1 to f7, the relationship between the frequencies f1 to f7 is expressed as fn ≒ (5/2) ^{n− 1.} The signal spectrum measuring apparatus according to claim 9, wherein f1 (where n = 1 to 7) is set.