JP3371390B2 - Active band attenuation filter, integrated circuit and signal processing device - Google Patents

Description

Detailed Description of the Invention

[0001]

[Table of Contents] The present invention will be described in the following order. Industrial applications Conventional technology (Fig. 7) Problems to be Solved by the Invention (FIGS. 8 and 9) Means for solving the problem (FIG. 2) Action (Fig. 2) Example (FIGS. 1 to 6) The invention's effect

[0002]

BACKGROUND OF THE INVENTION The present invention relates to an active band attenuation filter,
The present invention relates to an integrated circuit and a signal processing device, and can be applied to, for example, a television receiver which processes a color subcarrier.

[0003]

2. Description of the Related Art Conventionally, a television receiver receives a video signal (color subcarrier) in which a Y signal having luminance information and a C signal having color information are mixed. Therefore, when handling the Y signal, it is necessary to separate the C signal.
The simplest method of separating the C signal is to attenuate the carrier wave of the C signal, 3.58 [MHz], with a trap filter. There are generally the following two methods for adjusting the cutoff frequency to a certain frequency band without adjustment by automatic adjustment of the trap filter.

That is, as shown in FIG. 7, the transversal filter 1 has an integrated circuit structure. First, an automatic adjustment loop 2 for automatically adjusting the cutoff frequency is provided on a dummy delay line (indicated by DL in the drawing) 3. It has been assembled. In the transversal filter 1, a plurality of delay lines 4 to 9 which are the same as the dummy delay line 3 are connected in cascade, and the video signal S1 is applied to this.

The transversal filter 1 includes delayed video signals S3 to S5 and S from a plurality of delay lines 4 to 9.
7 is taken out and combined with the video signal S1 to obtain the amplifier 10
Give to. As a result, the transversal filter 1
The video signal S8 attenuated at a certain frequency (here, 3.58 [MHz]) can be output from the amplifier 10.

By the way, the dummy delay line is 3.58
The phase becomes 90 ° at [MHz], that is, (1 / 3.579545 [MH
z)) x (90/360) = 70 [nsec]. The automatic adjustment loop 2 supplies a burst signal (3.58 [MHz]) S9 which is a reference of the phase of the carrier wave of the C signal to a voltage controlled oscillator (hereinafter referred to as VCO (Voltage Controlled Oscill)).
ator)) 11 and the oscillation frequency of the VCO 11 is given to
Lock to 3.58 [MHz]. The VCO 11 outputs the oscillation output S10 to the dummy delay line 3 and the phase comparator 12
To output.

The phase comparator 12 outputs an error signal S12 obtained by multiplying the delay signal S11 having a phase of 90 ° output from the delay line 3 and the oscillation output S10 to the amplifying low-pass filter 13 to output a DC voltage component. S13 is output to the voltage-current conversion circuit 14. The voltage-current conversion circuit 14 negatively feeds back the current S14 corresponding to the error signal S12 to the delay lines 3 to 9 and maintains the phase of the delay signal S11 at 90 °.

[0008]

However, in the above-mentioned transversal filter 1, since a plurality of delay lines are required, the number of elements becomes large as a whole (this increases the chip area and increases the cost). There was a problem. When the number of elements increases as a whole, when a plurality of delay lines are formed side by side on a substrate, the number of delay lines having a large mutual distance increases. The delay lines having a large mutual distance have a large irregularity in their characteristics.

Therefore, the irregularity of the relative characteristics of the respective delay lines with respect to the dummy delay line 3 in the automatic adjustment loop 2 also becomes large. Therefore, there is a problem that the delay amount of each delay line is non-uniform, and the deviation of the cut-off frequency for each product of the transversal filter 1 is large even though the delay amount is automatically adjusted.

On the other hand, in order to avoid an increase in the number of elements as a whole, the following configuration can be considered. That is, as shown in FIG. 8, the trap filter circuit 16 has an integrated circuit configuration and outputs the oscillation output S10 of the VCO 11 locked at 3.58 [MHz] to the phase shift circuit 17 to have a phase difference of 90 °. Two output signals S16 and S17 are generated from the oscillation output S10.

The trap filter circuit 16 outputs an output signal S
16 and S17 are respectively bandpass filters (in the figure,
18) (indicated by BPF) and the phase comparator 12 to form an automatic adjustment loop 19. This automatic adjustment loop 1
The same bandpass filter 20 as the bandpass filter 18 in FIG. 9 is configured, and the current S14 is commonly negatively fed back to this and the bandpass filter 18 to subtract the output of the bandpass filter 20 from the original signal. Therefore, a trap filter can be constructed.

That is, the amplifier 21 has a band pass signal S1 obtained by applying the video signal S1 to the band pass filter 20.
9 is applied to the inverting input terminal, and the video signal S1 is applied to the non-inverting input terminal. As a result, the original video signal S
The amplifier 21 outputs the output S20 in which the gain of 1 is attenuated to "the gain of the bandpass filter 20" (here, the Y signal in which the carrier of the C signal (3.58 [MHz]) is attenuated from the video signal S1). A trap filter is constructed. Incidentally, the Y signal S20 is switched by the switch 22 to the video signal S1 as necessary and output.

With this configuration, the trap filter can be constructed with a small number of elements. However, in the trap filter circuit 16 described above, it is actually necessary to increase the Q of the bandpass filter in order to obtain a desired attenuation characteristic as a trap. The higher the Q, the higher the element sensitivity. Therefore, the bandpass filter 18 in the automatic adjustment loop 19 is
However, if even a small amount of non-uniformity of characteristics occurs between the bandpass filter 20 and the bandpass filter 20 that constitutes the trap, there is a problem that the deviation of the cutoff frequency for each product increases.

As described above, the gain of the 1-bandpass filter 20 is equal to the attenuation amount, so that the gain of the bandpass filter 20 becomes the maximum value on the frequency characteristic curve, for example, 0 [dB] at the cutoff frequency. Whether or not it will be important. That is, when the position on the characteristic curve at the cutoff frequency has already exceeded the maximum value or is slightly before, the gain of the bandpass filter 20 decreases and the amount of attenuation as a trap decreases.

This means that the non-uniformity of the gains of the bandpass filters 18 and 20 directly appears as a lack of attenuation. This non-uniformity of gain increases as Q increases. Therefore, there is a drawback that it is not easy to obtain a desired damping characteristic. On the other hand, in the frequency range where the signal is not attenuated by the trap, the original signal and the signal passing through the bandpass filter 20 are mixed with a phase difference. Due to this mixture, there is a drawback that the image quality is deteriorated.

By the way, as shown in FIG. 9, the transversal filter 1 and the trap filter circuit 1 described above are used.
In the frequency characteristic of No. 6, the cutoff frequency has the maximum value of the attenuation amount. Therefore, if the frequency deviates from the cutoff frequency even a little, the amount of attenuation sharply decreases. Therefore, when adjusting the cut-off frequency is not adjusted, it is necessary to minimize the variation factor.

The present invention has been made in consideration of the above points, is not adjusted, the attenuated frequency and the attenuation amount are not affected by the unevenness of the gain characteristics of the elements, and the signals having the phase difference are not mixed. The present invention is intended to propose an active band attenuation filter, an integrated circuit and a signal processing device capable of attenuating an attenuated frequency of an input signal with a small number of elements and outputting the attenuated frequency.

[0018]

In order to solve the above problems, the present invention generates a control signal based on the result of comparison between the phase of a bandpass output signal of an active bandpass filter means and the phase of a reference signal, A phase lock loop that controls the frequency of the bandpass output signal according to the control signal to synchronize the phase of the bandpass output signal with the phase of the reference signal, and the frequency of the bandpass output signal among the frequencies of the input signal given the input signal. And an active band attenuating filter means for outputting a band attenuating output signal in which the same frequency is attenuated in response to a control signal, the active band pass filter means includes a differential voltage signal to the first transconductance. A first transconductance amplifier that converts and outputs a proportional charge / discharge current signal, and a differential voltage signal to a second transconductance A band-pass output signal obtained from the second transconductance amplifier is negatively fed back to the first and second transconductance amplifiers by cascading the second transconductance amplifier which outputs the converted charge / discharge current signal. And adjusting the first and second transconductances in response to the control signal to control the frequency of the bandpass output signal, the active band attenuation filter means providing a differential voltage signal proportional to the first transconductance. A third transconductance amplifier that converts and outputs a discharge current signal and a fourth transconductance amplifier that converts and outputs a difference voltage signal into a charging / discharging current signal proportional to the second transconductance are connected in cascade. The band attenuation output signal obtained from the fourth transconductance amplifier by negative feedback to the third and fourth transconductance amplifiers, and Controlling the first transconductance and the frequency attenuating adjusted to according to the second transconductance and the control signal of the fourth transconductance amplifier of the transconductance amplifier.

Also, in the present invention, a control signal is generated based on the result of comparison between the phase of the bandpass output signal of the active bandpass filter means and the phase of the reference signal, and the frequency of the bandpass output signal is set in accordance with the control signal. Control to synchronize the phase of the bandpass output signal with the phase of the reference signal, and the input signal is applied to attenuate the frequency of the input signal that is the same as the frequency of the bandpass output signal according to the control signal. And an active band attenuating filter means for outputting a band attenuated output signal, the active band attenuating filter being formed on a substrate, wherein the active band pass filter means is arranged to provide a differential voltage signal proportional to the first transconductance. A first transconductance amplifier that converts and outputs a charge / discharge current signal and a differential voltage signal that is proportional to the second transconductance The second transconductance amplifier and a band pass output signal obtained from the second transconductance amplifier connected in cascade for converting the discharge current signal negatively fed back to the first and second transconductance amplifiers,
And, the first and second transconductances are adjusted according to the control signal to control the frequency of the bandpass output signal, and the active band attenuation filter means controls the differential voltage signal to charge and discharge current proportional to the first transconductance. A third transconductance amplifier that converts and outputs the signal and a fourth transconductance amplifier that converts and outputs the difference voltage signal into a charge / discharge current signal that is proportional to the second transconductance are connected in cascade. The band attenuation output signal obtained from the fourth transconductance amplifier is negatively fed back to the third and fourth transconductance amplifiers, and the first transconductance of the third transconductance amplifier and the second transconductance amplifier of the fourth transconductance amplifier are And the mutual conductance of is adjusted according to the control signal to control the frequency of attenuation.

Further, in the present invention, when the frequency of a predetermined band of the input signal is attenuated and processed, the control signal is based on the result of comparison between the phase of the band pass output signal of the active band pass filter means and the phase of the reference signal. To control the frequency of the bandpass output signal according to the control signal to synchronize the phase of the bandpass output signal with the phase of the reference signal, and the bandpass of the frequency of the input signal given the input signal. A band-attenuated output signal from an integrated circuit in which an active band attenuating filter having an active band attenuating filter means for outputting a band attenuated output signal in which the same frequency as the frequency of the output signal is attenuated according to a control signal is formed on a substrate. In the signal processing device for obtaining a band-attenuated output signal, the active bandpass filter means is provided for comparing the differential voltage signal to the first transconductance. A first transconductance amplifier that converts and outputs the charge / discharge current signal and a second transconductance amplifier that converts and outputs the difference voltage signal into a charge / discharge current signal proportional to the second transconductance. The band-pass output signal obtained by connecting the second transconductance amplifier is negatively fed back to the first and second transconductance amplifiers, and the first and second transconductances are adjusted according to the control signal. The active band attenuation filter means controls the frequency of the pass-through output signal, and the active band attenuation filter means converts the differential voltage signal into a charging / discharging current signal proportional to the first transconductance and outputs the third transconductance amplifier, and the differential voltage signal. A fourth transconductance amplifier, which converts and outputs a charge / discharge current signal proportional to the second transconductance, is connected in series to form a fourth transconductance amplifier. Negative feedback band attenuation output signal obtained from the transconductance amplifier to the third and fourth transconductance amplifier, and a first transconductance and the fourth third transconductance amplifier
And a second transconductance of the transconductance amplifier is adjusted according to the control signal to control the frequency of attenuation.

[0021]

The first and second transconductance amplifiers, which are cascade-connected and negatively feed back the output, constitute active bandpass filter means in the phase lock loop, and the cascade-connected first and second negative-feedback outputs are provided. By configuring the active band attenuating filter means with the same third and fourth transconductance amplifiers as the above-mentioned transconductance amplifier, there is no adjustment, and the attenuated frequency and the attenuation amount are not affected by the unevenness of the gain characteristics of the elements. , Signals with phase difference do not mix,
The attenuated frequency of the input signal can be attenuated and output with a small number of elements.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings.

In FIG. 1, reference numeral 24 indicates a signal processing device as a whole, for example, a television receiver, which receives an input signal,
For example, the video signal S1 is supplied to the luminance signal processing circuit 25 and the color signal processing circuit 26, and the luminance signal S22 and the color signal S23 are output to the mixing circuit 27, respectively. Mixing circuit 27
Supplies a three-primary-color signal S24 obtained by mixing and demodulating the luminance signal S22 and the chrominance signal S23 to a three-primary-color amplifier circuit (shown by RGB in the figure) 28. The three-primary-color amplifier circuit 28 supplies the three-primary-color signal S25 obtained by power-amplifying the three-primary-color signal S24 to the color cathode ray tube 29 to display an image on the screen.

The luminance signal processing circuit 25 has an integrated circuit structure formed on the semiconductor substrate together with the color signal processing circuit 26, and an active band attenuation filter, for example, a trap filter circuit 30 is arranged at the input stage. Luminance signal processing circuit 25
Supplies the video signal S1 to the trap filter circuit 30,
A carrier (3.58 [MHz]) of the C signal is attenuated to obtain a band-attenuated output signal, for example, a Y signal. Subsequently, the luminance signal processing circuit 25 processes the Y signal to obtain the luminance signal S22.

As shown in FIG. 2, the trap filter circuit 30 is provided with a phase lock loop, for example, an automatic adjustment loop 31, in place of the automatic adjustment loop 19 of the trap filter circuit 16. The automatic adjustment loop 31 is provided with active band pass filter means, for example, a band pass filter 32, instead of the band pass filter 18 of the automatic adjustment loop 19.

Further, the trap filter circuit 30 is provided with active band attenuation filter means, for example, a trap circuit 33, in place of the band pass filter 20 and the amplifier 21 of the trap filter circuit 16. The trap filter circuit 30 supplies the video signal S1 to the trap circuit 33, attenuates the carrier wave (3.58 [MHz]) of the C signal, and outputs the Y signal S21. The Y signal S21 corresponds to the switch 22.
Then, the video signal S1 is switched and output as needed.

The bandpass filter 32 and the trap circuit 33 are commonly provided with the comparison result of the phase comparator 12, for example, a control signal corresponding to the error signal S12, for example, the current S14, from the voltage-current conversion circuit 14 of the automatic adjustment loop 31. Are controlled simultaneously so that the cutoff frequency becomes constant.

The trap filter circuit 30 inputs the oscillation output S10 of the VCO 11 of 3.58 [MHz] locked to the burst signal S9 to the phase shift circuit 17. The phase shift circuit 17 generates a reference signal, for example, the output signal S16 and a second reference signal, for example, an output signal S17, having a phase difference of 90 ° with the output signal S16, and automatically outputs one output signal S16 as an automatic adjustment loop. It outputs to the phase comparator 12 of 31. In addition, the phase shift circuit 17 outputs the other output signal S17.
Is applied to the bandpass filter 32 of the automatic adjustment loop 31, and the bandpass filter 32 outputs a bandpass output signal, for example, the output signal S18 to the phase comparator 12.

The phase comparator 12 includes a bandpass filter 3
The output signal S18 of 2 has a phase difference of 90 with respect to the output signal S16.
The error signal S12 is output so that the predetermined DC voltage is obtained only when the input is made in °. Bandpass filter 32
The cut-off frequency is set to 3.58 [MHz]. At this frequency, output signal S17 and output signal S
The phase difference with 18 is 0 °.

As shown in FIG. 3, the bandpass filter 3
2 is configured by a transconductance amplifier, a so-called gm amplifier, which converts a difference voltage signal obtained from two input terminals into a charge / discharge current signal proportional to the mutual conductance and outputs the charge / discharge current signal. That is, the bandpass filter 32 is g
A reference voltage is applied to the non-inverting input terminal of the m-amplifier 36, and an output signal S18 is applied to the inverting input terminal for negative feedback control. The gm amplifier 36 converts the difference voltage signal between the reference voltage and the output signal S18 into a charging / discharging current S31 multiplied by the mutual conductance gm1 and outputs it to the gm amplifier 37.

The gm amplifier 37 is supplied with the charging / discharging current S31 at the non-inverting input terminal and the output signal S17 via the first capacitor of the capacitance C1 and the output signal S18 at the inverting input terminal for negative feedback. Controlled. Further, the gm amplifier 37 converts the voltage difference between the charging / discharging current S31 and the output signal S17 and the output signal S18 into a charging / discharging current S32 obtained by multiplying the mutual conductance gm2 and outputs the charging / discharging current S31 to one end of the second capacitor of the capacitance C2 and the buffer amplifier 38. Output. The buffer amplifier 38 is supplied with the potential of the one end of the second capacitor and outputs the output signal S18. Incidentally, the other end of the second capacitor is grounded.

As shown in FIG. 4, the trap circuit 33 is
The video signal S1 is applied to the non-inverting input terminal of the gm amplifier 39, and the Y signal S21 is applied to the inverting input terminal to perform negative feedback control. The gm amplifier 39 has a video signal S1 and a Y signal S21.
It is converted into a charging / discharging current S33 obtained by multiplying the mutual conductance gm1 by the difference voltage between and and output to the gm amplifier 40 and one end of the third capacitor of the capacity C1. Incidentally, the other end of the third capacitor is grounded.

In the gm amplifier 40, the non-inverting input terminal is supplied with the potential of one end of the third capacitor, and the inverting input terminal is supplied with the Y signal S21 to be subjected to negative feedback control. Also g
The m-amplifier 40 converts the difference voltage between the potential at the one end of the third capacitor and the Y signal S21 into a charging / discharging current S34 multiplied by the mutual conductance gm2 and outputs the charging / discharging current S34 to the buffer amplifier 41. The buffer amplifier 41 is supplied with the charging / discharging current S34 and the video signal S1 via the fourth capacitor having the capacity C2, and outputs the Y signal S21.

The gm amplifiers 36, 37, 39 and 40 are
The resistance value component r1 (that is, gm1 = 1 / r1) that appears to be the mutual conductance gm1 and the resistance value component r2 (that is, gm2 = 1 / r2) that appears to be the mutual conductance gm1 become the current S14 that is commonly provided by the voltage-current conversion circuit 14. It is adjusted at the same time. As a result, the charging / discharging current S31 to
By controlling S34, the band-pass filter 32 and the trap circuit 33 are subjected to negative feedback control so that the cutoff frequencies become constant at the same time.

In the above configuration, the transfer functions F _{BPF of the} bandpass filter 32 and the trap circuit 33, respectively.
And F _TRAP , where S is the complex angular frequency,

[Equation 1] And the following equation,

[Equation 2] Becomes

Therefore, the cutoff frequencies fc and Q of the bandpass filter 32 and the trap circuit 33 are both given by

[Equation 3] And the following equation,

[Equation 4] Becomes

That is, the bandpass filter 32 and the trap circuit 33 having the same cutoff frequency and the same Q have the same capacitance and the same transconductance gm.
It can be seen that this can be achieved by simply changing the connection method using an amplifier. With such a configuration, the trap filter circuit 30 without adjustment can be realized with a small number of elements, which is advantageous in cost.

Further, since the number of elements is small, the band pass filter 32 and the trap circuit 33 can be formed adjacent to each other on the semiconductor substrate when forming an integrated circuit. As a result, the relative characteristics of both are aligned. Further, the bandpass filter 32 can be constructed with the minimum necessary Q for the trap circuit 33. This makes the Q higher than necessary
It is possible to prevent the sensitivity from being excessively increased by setting to, and the deviation of the cutoff frequency for each product from increasing due to the influence of the relative irregularity of the characteristics. Further, the prevention effect is further increased by the relative characteristics of the two being aligned.

Further, all the video signals S1 are trap circuits 3
By passing only 3 signals, a signal with a phase difference becomes Y signal S
21 can be prevented from being mixed. Further, since all the video signals S1 pass through only the trap circuit 33, even if the gain characteristics of the bandpass filter 32 are not uniform, the attenuation amount of the trap circuit 33 is not affected at all.

According to the above construction, the automatic adjustment loop 3 is formed by the gm amplifiers 37 and 38 which are connected in cascade and negatively feed back the output.
The bandpass filter 32 in 1 is configured, and the trap circuit 33 is configured by the same gm amplifiers 39 and 40 as the gm amplifiers 37 and 38 that are cascade-connected and negatively feed back the output. The attenuation frequency and the attenuation amount are not affected by the unevenness of the gain characteristics of the elements, signals with a phase difference are not mixed, and the attenuated frequency of the input signal can be attenuated and output with a small number of elements.

In the above embodiment, the trap filter circuit 30 is arranged at the input stage of the luminance signal processing circuit 25 of the television receiver, but the present invention is not limited to this, and for example, a video tape recorder, A signal processing device for arranging in a luminance signal processing circuit of an arbitrary video reproducing device such as a video disk reproducing device or a video memory reproducing device, or for processing by attenuating a frequency of a predetermined band of a reproduced signal reproduced from an arbitrary recording medium. It can also be widely applied to. Also in this case, the same effect as described above can be obtained.

For example, as shown in FIG. 5, the video tape recorder 43 applies the video signal S1 supplied from an external video reproducing device to the trap filter 30 and outputs the Y signal S21.
And output it to the bandpass filter 44 to output C
The signal S26 is supplied to the color signal processing stage 45 for processing. The reproduction signal S27 read by the reproduction head 46 is supplied to the color signal processing stage 45. The color signal processing stage 45 amplifies the reproduction signal S27 by the head amplifier 47, and reproduces the reproduction signal S27.
28 to the comb filter 48.

The comb filter 48 separates the reproduced signal S28 into a Y signal S29 and a C signal S30 and supplies them to a luminance signal processing circuit 49 and a color signal processing circuit 50, respectively. Here, as shown in FIG. 6, by further arranging the trap filter 30 in the luminance signal processing circuit 49, the separation accuracy of the Y signal may be improved. As a result, the image quality can be further improved, and the comb filter 48 can be replaced with one having a simple structure.

In the above embodiment, the case where the video signal is processed by locking the burst signal S9 to the VCO 11 as the reference signal has been described, but the present invention is not limited to this, and the frequency of the target receiving station is not limited to this. The present invention can be widely applied to attenuating noises before and after, for example, attenuating a certain frequency band of an arbitrary input signal and outputting. In this case V
The frequency of the reference signal locked by the CO may be arbitrarily adjusted or arbitrarily generated.

[0045]

As described above, according to the present invention, the active bandpass filter means in the phase lock loop is constituted by the first and second transconductance amplifiers which are cascade-connected to negatively feed back the output, and are cascade-connected. And a third transconductance amplifier identical to the first and second transconductance amplifiers that negatively feed back the output.
By configuring the active band attenuation filter means with the fourth transconductance amplifier, there is no adjustment, the attenuated frequency and the attenuation amount are not affected by the unevenness of the gain characteristics of the elements, and signals having a phase difference are mixed. In addition, it is possible to realize an active band attenuation filter, an integrated circuit and a signal processing device capable of attenuating an attenuated frequency of an input signal with a small number of elements and outputting the attenuated frequency.

[Brief description of drawings]

FIG. 1 is a block diagram showing a television receiver according to an embodiment of an active band attenuation filter, an integrated circuit and a signal processing device according to the present invention.

FIG. 2 is a connection diagram for explaining a trap filter circuit according to an embodiment.

FIG. 3 is a connection diagram showing a configuration of a bandpass filter according to an embodiment.

FIG. 4 is a connection diagram showing a configuration of a trap circuit according to an embodiment.

FIG. 5 is a connection diagram showing a video tape recorder according to another embodiment.

FIG. 6 is a connection diagram showing a case where a luminance signal and a color signal are separated by a comb filter and then a luminance signal is further applied to the trap filter.

FIG. 7 is a connection diagram for explaining a transversal filter.

FIG. 8 is a connection diagram for explaining a conventional trap filter.

FIG. 9 is a characteristic curve diagram showing characteristics of traps.

[Explanation of symbols]

1 ... Transversal filter, 2 ... Automatic adjustment loop, 3 ... Dummy delay line, 4-9 ... Delay line, 10, 21 ... Amplifier, 11 ... VCO, 1
2 ... Phase comparator, 13 ... Amplification low-pass filter, 1
4 ... Voltage-current conversion circuit, 15 ... Phase shift circuit, 1
6 ... Trap filter circuit, 17 ... Phase shift circuit, 18, 44 ... Band pass filter, 19, 31 ...
… Automatic adjustment loop, 20… Band pass filter, 22
...... Switch, 24 …… Television receiver, 25,
49 ... Luminance signal processing circuit, 26, 50 ... Color signal processing circuit, 27 ... Mixing circuit, 28 ... 3 primary color amplification circuit, 2
9 ... Color cathode ray tube, 30 ... Trap filter circuit, 32 ... Band pass filter, 33 ... Trap circuit, 36, 37, 39, 40 ... Gm amplifier, 38, 4
1 ... Buffer amplifier, 43 ... Video tape recorder, 45 ... Color signal processing stage, 46 ... Playback head, 47
...... Head amplifier, 48 …… Comb filter.

Continuation of front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) H03H 11/04 H04N 9/64

Claims (9)

(57) [Claims] 1. A control signal is generated based on a result of comparison between a phase of a bandpass output signal of an active bandpass filter means and a phase of a reference signal, and a frequency of the bandpass output signal is controlled according to the control signal. Then, a phase lock loop for synchronizing the phase of the band-pass output signal with the phase of the reference signal, and the same frequency as the frequency of the band-pass output signal among the frequencies of the input signal is given to the control signal. An active band attenuating filter means for outputting an attenuated band attenuating output signal, wherein the active band pass filter means converts the differential voltage signal into a charging / discharging current signal proportional to the first transconductance. A first transconductance amplifier that converts and outputs the differential voltage signal into a charge / discharge current signal that is proportional to the second transconductance. A second transconductance amplifier that outputs the converted band is cascade-connected to negatively feed back the bandpass output signal obtained from the second transconductance amplifier to the first and second transconductance amplifiers, and Adjusting the first and second transconductances in response to the control signal to control the frequency of the bandpass output signal, the active band attenuation filter means proportionally converting the differential voltage signal to the first transconductance. A third transconductance amplifier that converts and outputs the charge / discharge current signal and a fourth transconductance amplifier that converts and outputs the difference voltage signal into a charge / discharge current signal proportional to the second transconductance are cascaded. The band-attenuated output signal obtained from the fourth transconductance amplifier by connecting is increased by the third and fourth transconductance. A negative feedback to the amplifier, and adjusting the first transconductance of the third transconductance amplifier and the second transconductance of the fourth transconductance amplifier in accordance with the control signal to adjust the attenuation frequency. An active band attenuating filter characterized by controlling. 2. The first transconductance amplifier is supplied with a reference potential at a non-inverting input end thereof, and the second transconductance amplifier is connected to the reference signal via a first capacitance at a non-inverting input end thereof. A second reference signal having the same frequency and a different phase is applied, a ground potential is applied to the output terminal through the second capacitor, and the third transconductance amplifier is applied with the input signal to the non-inverting input terminal. In the fourth transconductance amplifier, a ground potential is applied to a non-inverting input terminal through a third capacitor that is the same as the first capacitor, and an output terminal has a fourth potential that is the same as the second capacitor. 2. The active band attenuating filter according to claim 1, wherein the input signal is provided via the capacitance of the. 3. A control signal is generated based on the result of comparison between the phase of the bandpass output signal of the active bandpass filter means and the phase of the reference signal, and the frequency of the bandpass output signal is controlled according to the control signal. Then, a phase lock loop for synchronizing the phase of the band-pass output signal with the phase of the reference signal, and the same frequency as the frequency of the band-pass output signal among the frequencies of the input signal is given to the control signal. And an active band attenuating filter means for outputting an attenuated band attenuating output signal, the integrated circuit having an active band attenuating filter formed on a substrate. A first transconductance amplifier for converting and outputting a charge / discharge current signal proportional to the conductance, and a differential voltage signal for the second transconductance. And a second transconductance amplifier for converting into a charge / discharge current signal proportional to and outputting the same, the bandpass output signal obtained from the second transconductance amplifier is connected to the first and second transconductances. Negatively feeding back to an amplifier and adjusting the first and second transconductances in response to the control signal to control the frequency of the bandpass output signal, the active band attenuating filter means comprising: A third transconductance amplifier for converting and outputting a charge / discharge current signal proportional to the first mutual conductance; and a third for converting and outputting the difference voltage signal into a charge / discharge current signal proportional to the second mutual conductance. No. 4 transconductance amplifier is connected in cascade to obtain the band-attenuated output signal obtained from the fourth transconductance amplifier. Negatively feeding back to the fourth transconductance amplifier, and adjusting the first transconductance of the third transconductance amplifier and the second transconductance of the fourth transconductance amplifier according to the control signal. An integrated circuit characterized by controlling the frequency to be attenuated. 4. The first transconductance amplifier has a non-inverting input terminal supplied with a reference potential, and the second transconductance amplifier has a non-inverting input terminal connected to the reference signal via a first capacitor. A second reference signal having the same frequency and a different phase is applied, a ground potential is applied to the output terminal through the second capacitor, and the third transconductance amplifier is applied with the input signal to the non-inverting input terminal. In the fourth transconductance amplifier, a ground potential is applied to a non-inverting input terminal through a third capacitor that is the same as the first capacitor, and an output terminal has a fourth potential that is the same as the second capacitor. 4. The integrated circuit according to claim 3, wherein the input signal is supplied via the capacitance of the. 5. When attenuating a frequency of a predetermined band of an input signal for processing, a control signal is generated based on a result of comparison between a phase of a bandpass output signal of an active bandpass filter means and a phase of a reference signal, A phase lock loop for controlling the frequency of the band-pass output signal according to the control signal to synchronize the phase of the band-pass output signal with the phase of the reference signal, and the frequency of the input signal given the input signal. From an integrated circuit in which an active band attenuating filter having an active band attenuating filter means for outputting a band attenuating output signal in which the same frequency as the frequency of the band pass output signal is attenuated according to the control signal is formed on a substrate, In the signal processing device for obtaining the band-attenuated output signal and processing the band-attenuated output signal, the active band-pass filter means outputs the differential voltage signal to the first band-pass filter. A first transconductance amplifier that converts and outputs a charging / discharging current signal proportional to mutual conductance, and a second transconductance that converts and outputs a difference voltage signal into a charging / discharging current signal proportional to a second transconductance. The band pass output signal obtained from the second transconductance amplifier by cascade connection with an amplifier is negatively fed back to the first and second transconductance amplifiers, and the first and second transconductances are The frequency of the bandpass output signal is controlled by adjusting according to a control signal, and the active band attenuation filter means converts the differential voltage signal into a charge / discharge current signal proportional to the first transconductance and outputs the charge / discharge current signal. A third transconductance amplifier and the differential voltage signal converted into a charge / discharge current signal proportional to the second transconductance And a fourth transconductance amplifier that operates in a cascade connection to negatively feed back the band-attenuated output signal obtained from the fourth transconductance amplifier to the third and fourth transconductance amplifiers. A signal processing device, characterized in that the first transconductance of a transconductance amplifier and the second transconductance of a fourth transconductance amplifier are adjusted according to the control signal to control the frequency of the attenuation. 6. The first transconductance amplifier is supplied with a reference potential at a non-inverting input terminal thereof, and the second transconductance amplifier is connected to the reference signal via a first capacitor at a non-inverting input terminal thereof. A second reference signal having the same frequency and a different phase is applied, a ground potential is applied to the output terminal through the second capacitor, and the third transconductance amplifier is applied with the input signal to the non-inverting input terminal. In the fourth transconductance amplifier, a ground potential is applied to a non-inverting input terminal through a third capacitor that is the same as the first capacitor, and an output terminal has a fourth potential that is the same as the second capacitor. 6. The signal processing device according to claim 5, wherein the input signal is given through the capacitance of. 7. The signal processing device according to claim 5, wherein the signal processing device is a video signal processing device that processes a video signal. 8. The signal processing device according to claim 7, wherein the video signal processing device is a video reproducing device for reproducing the video signal from a recording medium. 9. The video signal processing device is a television receiver.
The signal processing device according to.