KR830000245B1 - Frequency characteristic regulator - Google Patents

Abstract

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Description

Frequency characteristic regulator

1 is a display diagram of an example of a conventional frequency characteristic adjusting device.

2 is an exemplary view showing a device of the present invention.

3 is a display diagram of a frequency band of an input signal divided by the apparatus of the present invention.

4 and 5 illustrate changes in the sum total characteristic of the low range with respect to the change in gain.

6 is a frequency characteristic diagram of gain on the low frequency side of the apparatus of the present invention.

7 is a frequency characteristic diagram of gain on the high frequency side of the present invention.

8 is a diagram showing an example of frequency characteristics of gain of the device of the present invention.

The present invention relates to a frequency characteristic adjusting apparatus such as an audio amplifier.

The frequency characteristic adjusting device is, for example, a device having a variable frequency characteristic in order to make the bass and treble louder or smaller as desired.

The conventional frequency characteristic adjusting device uses a variable resistor to realize this variable frequency characteristic, and FIG. 1 shows an example of the conventional frequency characteristic adjusting device, in which (1) denotes an input terminal, (2) Is an output terminal, (3) is an amplifier, and the output terminal of the amplifier 3 is connected with a resistor and a capacitor for obtaining desired frequency characteristics. Among them, (4) and (5) are variable resistors for varying the frequency characteristics, and the frequency characteristics are changed by operating the variable resistors 4 and 5.

However, such a conventional frequency characteristic adjusting device is inconvenient for remote operation.

That is, in order to enable remote operation in the apparatus of FIG. 1, the variable resistors (4) and (5) are separated from the apparatus main body, and the operation part is placed in front of the hand so that the variable resistors (4) and (5) and the apparatus main body are connected to the transmission line. It must be configured to connect via In this case, since the frequency-adjusted signal flows through the transmission line, the transmission line must be shielded to prevent noise or induction, and therefore, there is a problem that extra capacity or inductance is applied and sufficient performance is not obtained. Audio equipment is often used for stereo (two channels), so the transmission line requires one set again.

Therefore, such a conventional turn circuit is extremely unreasonable when trying to operate remotely.

This invention is made in view of this point, and it aims at providing the frequency characteristic adjustment apparatus suitable for remote operation, and also suitable for an integrated circuit. That is, the present invention provides a filter circuit for filtering a predetermined frequency band of the input signal, and amplifies the output signal of the filter circuit and the input and output signals of the filter circuit differently with an amplifier so that the output of the two amplifiers can be added and captured. At the same time, at least one of the electric amplifiers is a variable gain amplifier, and the filter circuit for supplying the signal to the variable gain amplifier has a variable impedance means so that the cutoff frequency is variable. The present invention provides a frequency characteristic adjusting apparatus which changes the frequency characteristic of the electric addition output arbitrarily and symmetrically with respect to the change of the gain by changing the gain into an arbitrary change by changing it in a predetermined relationship.

Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 2 shows an embodiment of the present invention, and the input signal applied to the input terminal 21 is the first variable gain amplifier (hereinafter referred to as VCA) 22. It is applied to the non-inverting input terminal, and this first VCA 22 constitutes a feedback amplifier in which the inverting input terminal and the output terminal are commonly connected. A first capacitor C ₁ 23 is connected between the output terminal and ground. It is. The output of the first VCA 22 is supplied to the non-inverting input terminal of the second VCA 24. Similarly, since the second VCA 24 constitutes a feedback amplifier in which the inverting input terminal and the output terminal are commonly connected, a second capacitor C ₂ 25 is connected between the output terminal and the ground.

On the other hand, the voltage between the non-inverting input terminal and the output terminal of the first VCA 22 is applied between the non-inverting input terminal and the inverting input terminal of the third VCA 26, and also with the non-inverting input terminal of the second VCA 24. The voltage between the output terminals is applied between the non-inverting input terminal and the inverting input terminal of the fourth VCA 27. The voltage between the output terminal of the second VCA 24 and the ground is applied between the non-inverting input terminal and the inverting input terminal of the fifth VCA 28.

The outputs of the third to fifth VCAs 26 to 28 are guided to the adder 29 and added to each other, and are guided to the output terminal 30. Further, the first to fifth VCAs 22, 24 and 26 to 28 are, for example, voltage input-current output types, and the input impedance and the output impedance are sufficiently high with each other.

Next, the operation of this circuit will be described. First, the circuit of the first VCA 22 and the first capacitor 23 is equivalently represented by the first low pass filter as indicated by (31) in FIG. (LPF).

Waenya when the output (V ₁₎ to the frequency of the input (V ₁₎ of the VCA 22, capacitor 23 is the output of VCA 22 in the lower frequencies of a frequency below the conduction corresponds to the other gain 22 However, if the frequency of the input Vi becomes high and the capacitor 23 conducts, the output terminal of the VCA 22 becomes the ground potential, so that the output V ₁ becomes zero. Therefore, LPF is equivalently constituted.

In this case, the signal between the input and output of the LPF (U _i -V ₁₎ is a high-pass such as the one represented by the equivalent to a third-degree (32) since it is a car that the reduced component from the input signal (V _i) It is equivalent to the output of the filter HPF.

Therefore, the third VCA 26 to which the secondary voltage is applied is the VCA for HPF output.

If the above relationship is expressed using a relational expression, the input V _i (S) of the VCA 22, the output U ₁ (S) and the gain of the VCA 22 are set to g _m1 .

Becomes

On the other hand, the second LPF is configured similarly to the second VCA 24 and the second capacitor 25.

Therefore, assuming that the time constant is set so that the cutoff frequency of the second LPF here is lower than the cutoff frequency of the first LPF, the characteristic shown in (33) of FIG. 3 is obtained.

Thus, the difference between the input U ₁ and the output U ₂ is equivalent to the output of the band pass filter BPF as indicated by 34 in FIG. That is, since the output of the second LPF is a lower frequency component than the output of the first LPF, the difference of the output of the second LPF from the output of the first LPF is equivalent to the output of the BPF. Therefore, the secondary voltage is applied. The fourth VCA 27 to be used is a VCA for BPF output.

If the above relation is represented by the same relation, the output of VCA (24) is U ₂ (S) and the gain of VCA is g _m2 .

Becomes

In addition, since the voltage between the output terminal of the second VCA 24 and the ground is the output U ₂ of the second LPF, the frequency characteristic thereof is as shown in FIG. Therefore, it is expressed by the relational expression (2).

Therefore, the electric fifth VAC 28 to which this voltage is applied is a VCA for LPF output.

Here, the outputs of the third to fifth VCAs 26 to 28 are supplied to and added to the adder 29 as described above. In this case, the summation output i ₀ (S) is expressed by the formulas (2), (3) and (4) if the gains of VCA (26) to (28) are g _m3 , g _m4 and g _m5 , respectively.

i ₀ = g _m3 {U _i (S) -U ₁ (S)} + g _m4 {U ₁ (S) -U ₂ (S)} + g _m5 {U ₂ (S)}. … … (5)

Becomes

Therefore, the gain G (S) = _iD (S / V _i (S) from the input terminal 21 to the output terminal 30 is expressed by the equations (5) and (2), (3) and (4).

Becomes

As can be seen from this equation (6), it can be seen that the frequency characteristics of the gain G (S) can be arbitrarily set by adjusting the gains g _m3 to g _m5 of the respective VCAs 26 to 28. That is, for example, the gain G (S) when the gain of each VCA 26 to 28 is set to g _m3 = g _m4 = g _m5 becomes G (S) = g _m3 and becomes constant with respect to frequency.

That is, the frequency characteristic is exactly flat. If the gain g _m3 of the third VCA 26 is increased, the high range is emphasized. If the gain g _m4 of the fourth VCA 27 is increased, the mid range is emphasized, and the gain g _m5 of the fifth VCA 28 is increased. If we increase, we can see that the low range is emphasized.

In this manner, according to the present invention, arbitrary frequency characteristics can be obtained by changing the gains g _m3 to g _m5 of the third to fifth VCAs.

However, when only the gains g _m3 to g _m5 of the third to fifth VCAs are changed as described above, when the gains are increased and lowered as described below, the characteristics are asymmetric and applied to an acoustic tone circuit. It may not be desirable in some cases.

In other words, for example, when C _{1 <} C ₂ , the low frequency range is considered,

Cool with

Therefore, the absolute value of the gain at low frequencies

Becomes

Here, if g _m2 and g _m4 are constant and g _m5 is changed to change the low frequency characteristic, and the gain g _m5 as shown in FIG. 4 is increased, the frequency characteristic of the output of the VCA 28 is (33). If the gain g _m5 is reduced while the total characteristic becomes (41), the frequency characteristic of the output of the VCA 28 becomes (33 ") and the total characteristic becomes (42). In other words, the frequency characteristics 41 and 42 become asymmetrical.

However, by according to the same time changing the gain g _m2 of the VCA (24) a second time to change the gain g _m5 of claim 5 VCA (28) in this invention up because changing the filter cut-off frequency, the frequency characteristic symmetrically Able to know.

In other words, when the gain g _m5 of the fifth VCA 28 is made large, the gain g _m2 of the second VCA 24 is made smaller, and as shown in the frequency characteristic 51 of FIG. To lower it.

In this case, the sum characteristic is equal to (52). On the other hand, when the gain g _m5 of the fifth VCA 28 is reduced, the gain gm ₂ of the second VCA 24 is increased to increase the frequency characteristic of FIG. Increase the cutoff frequency of the LPF as indicated in 53). Then, the frequency characteristic of the sum becomes as (54) and can be symmetrical with the frequency characteristic (52).

Specifically, g _m2 in Equation (8)

Shall be.

In this case, if g _m4 is changed to 1 (constant) and β is constant (ie, g _m5 is changed), the expression (8)

only

Becomes

Therefore, the relationship between the absolute value of this gain and the frequency is shown in FIG. This figure shows the characteristics of the low frequency side, that is, the pars control, and as can be seen from the figure, if the relationship between g _m4 , g _m5 , and g _m2 is defined, the frequency characteristic is symmetrical with respect to the change of α (ie g _m5 ) It can be seen that the tone-circuit has optimal characteristics.

β의 관계가 성립할 때 제7도로 α표시한 것과 같이 β(즉 g_m3)의 변화에 대하여 대칭의 주파수 특성을 얻을 수가 있어 고역의 톤-회로로서는 최적의 특성을 갖고 있다. 더욱 통상의 톤-회로로써는 저역과 고역, 공히 조정한 경우가 많으므로 그 경우의 이득의 주파수 특성의 예를 제8도로 표시한다.On the high side, the same result holds, for example, α = g _m3 / g _m4 , g _m1 =

When the relationship of β is established, as shown by α in FIG. 7, symmetrical frequency characteristics can be obtained with respect to the change of β (i.e., g _m3 ). As a more common tone-circuit is often adjusted in the low and high ranges, an example of the frequency characteristics of the gain in that case is shown in FIG.

As described above, according to the present invention, the frequency characteristics can be arbitrarily changed by appropriately controlling the gains g _m3 to g _m5 of the VCAs 26 to 28, and again, the gains g of the first and second VCAs 22 and 24. according to _m1, Sikkim the gain g _{m1, m2} g changed simultaneously with the change in the g ~ g _{m5 m7,} because by changing the g _m2 it possible to change the cut-off frequencies of the LPF, obtains a frequency characteristic of symmetry. Further, the gain control of the VCA can be performed by controlling the DC control voltage without mentioning it.

Therefore, according to the frequency characteristic adjusting apparatus of the present invention, when performing remote operation, sufficient performance can be obtained by simply installing the operation unit in front of the hand and connecting the VCA to the transmission line.

That is, in the conventional frequency characteristic adjusting apparatus, since the signal for controlling the frequency characteristic flows through the variable resistor and the transmission line to which the circuit main body is connected, the transmission line has to be shielded. Since the gain of the VCA is changed by DC control voltage instead of direct adjustment, there is no need to shield the transmission line to prevent noise or induction since the signal whose frequency characteristic is controlled does not flow through the transmission line.

In addition, in the circuit of the present invention, when the circuit is directly integrated, the necessary external connection points having different input / output ends with fewer pins since the connection points 31 and 32 of the capacitors 23 and 25 have very small capacities.

This indicates that the present invention is particularly suitable for integrated circuitry.

As mentioned above, although one Example of FIG. 2 was demonstrated, this invention is not limited to this Example.

That is, in the above embodiment, the case where the control is divided into three bands of frequency has been described, but the control may be divided into two bands.

In this case, the output of the first LPF (first VCA 22) and the fifth except the VCA 24 capacitor 25 and the fourth VCA 27 constituting the second LPF in FIG. The input of the VCA 28 may be connected. It is also possible to divide and control the frequency band into four or more. In this case, the amplifier which amplifies the signal between LPF and input / output may be connected in multiple stages.

As described above, the amplifier for amplifying the signal between the LPF input and output and the output of the LPF may not necessarily be a VCA, and at least one amplifier corresponding to a band in which the frequency characteristic needs to be variably controlled may be VCA.

In that case, the cutoff frequency of the LPF supplying the signal to the VCA is configured to change at the same time as the gain of the VCA changes.

In another embodiment, the case where LPF is used as the filter network is shown, but the same effect can be obtained even with HPF.

Claims (1)

A filter circuit (25, 24) having a capacitor (25) and a variable impedance means (24) and whose cutoff frequency is adjusted by varying the impedance value of the electrically variable impedance means (24) and the filter circuit (25, 24). And a second amplifier 27 for amplifying the difference signal between the input and output of the signal, and an adding means 29 for adding the output of the second amplifier 27 and the output of the electrical first amplifier 28. At least one of the first and second amplifiers 28 and 27 is a variable gain amplifier, the gain of which is adjusted by the gain control signal, and at the same time as the gain adjustment, the impedance value of the electrically variable impedance means 24. The frequency characteristic adjusting device is changed so that the cutoff frequencies of the electric filter circuits (25) and (24) are adjusted.

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