JP3232744B2 - Video signal processing circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video signal processing circuit, and more particularly to an improvement in an automatic filter adjustment circuit and a frequency conversion circuit.

[0002]

2. Description of the Related Art FIG. 4 is a block diagram showing an example of a conventional automatic filter adjusting circuit. In FIG. 4, 1 is a reference oscillator, 2 is a 90 ° phase shifter, 3 is a reference BPF including a second-order band-pass filter (hereinafter, referred to as BPF),
Reference numeral 4 denotes a multiplier, 5 denotes a low-pass filter (hereinafter, referred to as LPF), and 6 denotes a voltage / current (hereinafter, abbreviated as V / I) converter.

In such a configuration, the reference oscillator 1
Generates a reference signal S _B having a frequency serving as a reference for automatic adjustment, and outputs the signal to the 90 ° phase shifter 2. In the 90 ° phase shifter 2, from the input reference signal S _B, 2 kinds of signals S _B0 and S _B90 phases 0 ° and 90 ° are obtained.

A signal S _B0 having a phase of 0 ° is a reference BP
Input to F3. In this case, the phase at the frequency f ₀ is 0
°. The output signal of the reference BPF 3 is input to one input terminal of the multiplier 4. To the other input terminal of the multiplier 4, a 90 ° phase signal S _B90 output from the 90 ° phase shifter 2 is input. The multiplier 4 performs a phase comparison between the two by multiplying the two input signals, and outputs the resulting phase error to the LPF 5.

In the LPF 5, a high-order component of the input phase error is cut, and a signal from which the high-order component is cut is V
The signal is input to the / I converter 6 and converted from voltage to current.
The current I ₆ from the V / I converter ₆ is equal to the reference BPF
3 is fed back to the reference BP with respect to the reference signal S _B
The output phase of F3 is controlled so as to be 90 °. That is, the frequency f _{0 of the} reference BPF ₃ is equal to the reference signal S
_This means that it has been adjusted to the same accuracy as _B.

A video signal processing circuit is provided with a frequency conversion circuit. In a conventional frequency conversion circuit, frequency conversion is performed using only a multiplier.

[0007]

However, in the above-mentioned conventional automatic filter adjusting circuit, the reference oscillator 1, 90 °
It comprises a phase shifter 2, a reference BPF 3, a multiplier (phase comparator) 4, an LPF 5, and a V / I converter 6.
Since the circuit is configured as an independent block for other functions on the same IC, there has been a problem that the number of elements and power consumption increase.

Further, in the above-described conventional frequency conversion circuit, since only the multiplier is used, there is a problem that a so-called side band leak occurs.

The present invention has been made in view of the above circumstances, and has as its object to reduce the number of elements, reduce power consumption, and provide a video signal capable of performing frequency conversion without causing sideband leakage. It is to provide a processing circuit.

[0010]

In order to achieve the above object, the present invention provides an oscillator for generating a reference signal of a predetermined frequency and a 90 ° shifter for generating a signal obtained by shifting the phase of the reference signal by the oscillator by 90 °. A video signal processing unit for processing a video signal using a reference signal from the oscillator and a signal from the 90 ° phase shifter, and a non-shifted signal in the 90 ° phase shifter of the video signal processing unit. A reference filter to which one of the shift signals is input, and an output signal of the reference filter and the 90 °
A phase comparator for performing a phase comparison with the other signal of the phase shifter, and a filter automatic adjustment unit that feeds back a comparison result of the phase comparator to the reference filter and holds a reference frequency of the reference filter at a predetermined frequency. And so on.

[0011]

According to the present invention, an oscillator for generating a reference signal having a predetermined frequency and a signal for generating four signals having a phase difference of 90 ° from each other by shifting the phase of the reference signal by the oscillator.
A video signal processing unit for processing a video signal using a reference signal from an oscillator and a signal from a 90 ° phase shifter; and four video signal processing units using the 90 ° phase shifter. A reference filter to which one of the two signals having a phase difference of 90 ° among the signals is input, and a phase comparison for comparing the output signal of the reference filter with the other signal of the 90 ° phase shifter A filter automatic adjustment unit that feeds back the comparison result of the phase comparator to the reference filter to maintain the reference frequency of the reference filter at a predetermined frequency, and a video signal processing unit that includes a 90 ° phase shifter. A first multiplier and a second multiplier for multiplying two of the two signals having a phase difference of 180 ° with each other, an output of the first multiplier, and the second multiplier And to have a frequency converting unit and an adder for adding the output.

[0013]

According to the present invention, a reference signal of a predetermined frequency serving as a reference is generated by the oscillator of the video signal processing section and output to the video signal processing system and the 90 ° phase shifter. 90
° In the phase shifter, the phase is 0 ° and 90 ° from the input reference signal.
Are obtained and output to the filter automatic adjustment unit and the video signal processing system. In the video signal processing system, predetermined signal processing is performed based on the reference signal and the signal subjected to the phase shift operation. In the filter automatic adjustment unit, one of the two signals having the input phases of 0 ° and 90 ° is input to the reference filter.
The output signal of the reference filter is input to one input terminal of the phase comparator. The other signal output from the 90 ° phase shifter is input to the other input terminal of the phase comparator.
The phase comparator compares the phases of two input signals,
The resulting phase error is fed back to the reference filter. Thereby, the frequency of the reference filter is adjusted to the same accuracy as that of the reference signal.

According to the present invention, in the frequency converter,
The reference signal is input to the first phase shifter and the phase difference is 90 °
Are generated and output to the first and second multipliers, respectively. Further, the converted signal is input to the second phase shifter to generate two signals having a phase difference of 90 °, which are output to the first and second multipliers, respectively. The first multiplier multiplies one signal generated by the first phase shifter and one signal generated by the second phase shifter,
The result is output to the adder. Similarly, in the second multiplier, the other signal generated by the first phase shifter is multiplied by the other signal generated by the second phase shifter, and the result is output to the adder. You. The adder adds the output of the first multiplier and the output of the second multiplier, and outputs a signal without unnecessary sidebands.

According to the present invention, a reference signal of a predetermined frequency serving as a reference is generated by the oscillator of the video signal processing section and output to the video signal processing system and the 90 ° phase shifter. In a 90 ° phase shifter, the phase is shifted by 90 from the input reference signal.
And four types of signals are output to the video signal processing system, and two signals having a phase difference of 90 ° are output to the filter automatic adjustment unit from among the four signals. 180 ° phase difference between the four signals
Are output to the frequency conversion unit as a pair. In the video signal processing system, predetermined signal processing is performed based on the reference signal and the signal subjected to the phase shift operation. In the filter automatic adjustment unit, one of the two signals having a phase difference of 90 ° is input to the reference filter. The output signal of the reference filter is input to one input terminal of the phase comparator. The other signal output from the 90 ° phase shifter is input to the other input terminal of the phase comparator. In the phase comparator, two input signals are compared in phase, and the resulting phase error is fed back to the reference filter. Thereby, the frequency of the reference filter is adjusted to the same accuracy as that of the reference signal. In the frequency conversion unit, the phase difference between the two is 18
Two signals of 0 ° are input to the first and second multipliers as a set, respectively, and the two signals input by each multiplier are multiplied by each other, and the result is output to the adder. In the adder, the output of the first multiplier and the output of the second multiplier are added, and a signal having no unnecessary sideband is output.

[0016]

FIG. 1 is a block diagram showing an embodiment of an automatic filter adjusting circuit in a video signal processing circuit according to the present invention. In FIG. 1, reference numeral 10 denotes a video signal processing unit, and reference numeral 20 denotes an automatic filter adjustment unit.

The video signal processing section 10 is provided in a video signal processing IC and has a variable frequency reference oscillator (VXO) composed of a crystal oscillator used for so-called chroma signal processing.
11 and the phase of 90
And a 90 ° phase shifter 12 for generating a shifted signal. The video signal processing unit 10 includes a reference oscillator 1
Reference signal of a frequency f _SC generated by 1 (e.g., color subcarrier) by using the S _B, the reference signal S signal S _B90 with _B of the phase is shifted 90 ° in the 90 ° phase shifter 12 chroma Perform signal processing. Further, the phase shifter 12 outputs signals S _B0 and S _{B90 of} which the phase shift is 0 ° and 90 ° to the filter automatic adjustment unit 20.

The automatic filter adjuster 20 determines that the phase output from the 90 ° phase shifter 12 of the video signal processor 10 is 0 °.
BPF 21 to which the signal S _B0 is input, the output signal of the reference BPF 21 and the video signal processing unit 1
0, the phase shift output from the 90 ° phase shifter 12 is 90.
A multiplier 22 as ° phase comparator for multiplying the signal S _B90 of the LPF23 to cut the high-order component from the output signal of the multiplier 22, the current to convert the voltage level of the output signal of the LPF23 current I ₂₄ reference BPF21
And a V / I converter 24 for feeding back to the V.I.

Next, the operation of the above configuration will be described. A reference signal S _B having a frequency f _{SC serving as} a reference is generated by a reference oscillator 11 of the video signal processing unit 10 and output to a chroma processing system and a 90 ° phase shifter 12 (not shown). 90
The ° phase shifter 12, the input reference signal S _B, the phase is 0 °
And two signals S _B0 and S _B90 of 90 ° are obtained, and the filter automatic adjustment unit 20 and the signal S _B90 are output to a chroma processing system (not shown). In the chroma signal processing system,
Predetermined signal processing is performed based on signals S _B0 and S _B90 .

On the other hand, the signal S _B0 having a phase of 0 ° input to the automatic filter adjusting unit 20 is input to the reference BPF 21. In this case, the phase at the frequency f ₀ is 0 °. The output signal of the reference BPF 21 is input to one input terminal of the multiplier 22. The other input terminal of the multiplier 22 has a phase of 90 ° output from the 90 ° phase shifter 12.
Signal S _B90 of is inputted. The multiplier 22 performs a phase comparison between the two by multiplying the two input signals.
The resulting phase error is output to LPF 23.

In the LPF 23, the input higher-order component of the phase error is cut, and the signal from which the higher-order component has been cut is input to the V / I converter 24, where it is converted from voltage to current. Current I ₂₄ by V / I converter 6 is fed back to the reference BPF 21, the output phase of the reference BPF3 is controlled to be 90 ° to the reference signal S _B. That is, the frequency f ₀ of the reference BPF becomes to being adjusted to the same precision and the reference signal S _B.

As described above, according to this embodiment,
High-precision reference oscillator (VXO) already provided in the video signal processing IC and functioning as a chroma signal processing system
The phase shifter 11 and the 90 ° phase shifter 12 are shared by an automatic filter adjustment circuit. Therefore, when configuring the filter automatic adjustment circuit, conventionally, the reference oscillator, 90 °
Phase shifter, reference BPF, multiplier (phase comparator),
In contrast to a circuit composed of an LPF and a V / I converter, which is configured as an independent block for other functions on the same IC, in this circuit, a reference oscillator and a 90 ° phase shifter are provided as independent blocks. Since it does not need to be configured as a block, the number of elements and power consumption can be reduced, and a high-performance circuit can be realized.

[0023] In the present embodiment has been described an example in which the reference filter BP F, it is needless to say not limited thereto. Further, even if the reference filter configured as shown in FIG. 1 is applied as a chroma emphasis BPF having the strictest standard in an 8 mm video signal processing format, for example, the standard filter is sufficiently satisfied and the f of other filters is satisfied. ₀ can also be managed with high precision.

FIG. 2 is a diagram showing a basic configuration of a frequency conversion circuit in a video signal processing circuit according to the present invention. In FIG. 2, reference numeral 30 denotes a frequency converter, which is a first 90 ° phase shifter 31, a second 90 ° phase shifter 32, a first multiplier 33,
It comprises a second multiplier 34 and an adder 35.

The first 90 ° phase shifter 31 receives an input reference signal, for example, cos (ω ₁ t), and has a phase difference of 9
Obtain the two signals cos (ω ₁ t) and ± sin (ω ₁ t) at 0 °,
Output to the first and second multipliers 33 and 34, respectively. The second 90 ° phase shifter 32 receives the input converted signal, for example, cos (ω ₂ t), and has a phase difference of 90 °.
Obtain two signals cos (ω ₂ t) and ± sin (ω ₂ t), and outputs the first and second multipliers 33 and 34, respectively. The first multiplier 33 outputs an output signal of the first 90 ° phase shifter 31.
cos (ω ₁ t) and the output signal cos (ω ₁ ) of the second 90 ° phase shifter 32
₂ t) and the result [cos (ω ₂ t) · cos (ω ₁ t)]
Is output to the adder 35. The second multiplier 34 outputs the output signal sin (ω ₁ t) of the _first 90 ° phase shifter 31 and the second 90 °
The output signal of the phase shifter 32 is multiplied by sin (ω ₂ t), and the result [± sin (ω ₂ t) · sin (ω ₁ t)] is output to the adder 35. The adder 35 adds the output of the first multiplier 33 and the output of the second multiplier 34, and outputs the result as an output signal of the frequency conversion unit 30.

The operation result of the adder 35 is as shown by the following equation. cos (ω ₂ t) · cos (ω ₁ t) ± sin (ω ₂ t) · sin (ω ₁ t) = cos (ω ₂ ± ω ₁ ) t ... (1) That is, the frequency conversion circuit of FIG. The output signal has no unnecessary sidebands. Therefore, side band leak does not occur.

In this frequency conversion circuit, a first 90 ° phase shifter 31 and a second 90 ° phase shifter 32 are connected to a video signal processing IC similarly to the automatic filter adjustment circuit described above.
And a high-precision reference oscillator (VXO) 11 functioning as a chroma signal processing system and a 90 ° phase shifter 12 may be used in place of and shared with each other.

FIG. 3 shows a high-precision reference oscillator (VXO) functioning as a chroma signal processing system of the video signal processing unit 10.
FIG. 2 is a circuit diagram showing an example of a configuration of a video signal processing circuit sharing an 11 and 90 ° phase shifter 12 and having both an automatic filter adjustment circuit and a frequency conversion circuit.

As shown in FIG. 3, a reference oscillator 11 in the present circuit comprises a 90 ° phase shifter 111, limiters 112, 1
13, attenuator 114, adder 115 and resistance element R
_{1 to} R ₄ , switches SW ₁ and SW ₂ , a voltage source V ₁ , a current source i, and the like. A reference signal set to a predetermined frequency is supplied to a changeover switch 13, a limiter 14, and a sixth-order signal. The signal is output as a sine wave to the chroma signal processing system (not shown) through the LPF 15 as F _SC , and is input to the 90 ° phase shifter 12 via the capacitor C ₁ .

The 90 ° phase shifter 12 includes amplifiers 121 to 12
3, the limiter 124 and 125, the resistance element R ₅ to R _8, are composed of the capacitor C _2, C ₃ and a voltage source V _2, by delaying the phase of the input reference signal limiter 1
24 outputs two signals having phases of 90 ° and 270 °, and a limiter 125 outputs phases of 0 ° and 18 °.
Two signals of 0 ° are output. Each limiter 124, 1
The four signals having different phases by 90 ° output from 25 are output to a chroma signal processing system (not shown).
A signal having a phase of 90 ° is input to the multiplier 22 of the automatic filter adjustment unit 20 via the capacitor C _4, and a signal having a phase of 0 ° is input to the reference BPF 21. Further, the phase output from the limiter 124 is 90 ° and 270 °.
The signal of ° is input to the second multiplier 34 of the frequency conversion unit 30, and the signals having the phases of 0 ° and 180 ° output from the limiter 125 are input to the first multiplier 33 of the frequency conversion unit.

It should be noted that two signals whose phases differ by 90 ° are input.
When the force is applied, the operation of the filter automatic adjustment unit 20 is as shown in FIG.
Since it is the same as the case, the description is omitted here. Ma
In addition, the first and second multipliers 33,
34 is divided by a frequency divider (not shown) with a predetermined frequency division ratio.
The obtained signal is input via the LPF 36. First and
And the operation results of the second multipliers 33 and 34 are output by an adder 35.
The signals are added and input to the carrier BPF 37. This cap
The rear BPF 37 has a voltage V /
The feedback current from the I-converter 24 is supplied,
Wave number f ₀Is adjusted to the same accuracy as the reference signal. Cap
The output of rear BPF 37 is not shown as signal CAR OUT.
Output to the processing circuit.

According to the video signal processing circuit shown in FIG. 3, a high-precision VXO and a 90 ° phase shifter conventionally mounted on a video signal processing IC and used for chroma signal processing can be automatically adjusted by a filter automatic adjustment circuit and a frequency conversion circuit. Since it is configured to be shared by circuits, it is possible to reduce the number of elements, reduce power consumption, realize a high-performance circuit, and use it for chroma signal processing when chroma carrier conversion is so-called SSB method. Since an accurate output signal of a 90 ° phase shifter is used, an accurate conversion circuit can be realized.

[0033]

As described above, according to the present invention,
The number of elements and power consumption can be reduced. Also,
When the chroma carrier conversion is performed by the SSB method, an accurate conversion circuit can be realized by also using the 90 ° phase shifter of the signal processing system.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing an embodiment of an automatic filter adjustment circuit in a video signal processing circuit according to the present invention.

FIG. 2 is a diagram showing a basic configuration of a frequency conversion circuit according to the present invention.

FIG. 3 is a circuit diagram showing a configuration example of a video signal processing circuit including both a filter automatic adjustment circuit and a frequency conversion circuit according to the present invention.

FIG. 4 is a configuration diagram of a conventional automatic filter adjustment circuit.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Video signal processing part 11 ... Reference oscillator (VXO) 12 ... 90 degree phase shifter 20 ... Filter automatic adjustment part 21 ... Reference BPF 22 ... Multiplier 23 ... LPF 24 ... V / I converter 30 ... Frequency conversion circuit 31 ... First 90-degree phase shifter 32 ... Second 90-degree phase shifter 33 ... First multiplier 34 ... Second multiplier 35 ... Adder

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-5-30475 (JP, A) JP-A-4-61508 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H03H 11/04 H04N 9/45

Claims (2)

(57) [Claims] 1. An oscillator for generating a reference signal of a predetermined frequency, and a 90 ° phase shifter for generating a signal obtained by shifting the phase of the reference signal by 90 ° by the oscillator, wherein the reference signal and the 90 ° phase shift by the oscillator are provided. Signal processing unit for processing a video signal using a signal from a shifter; a reference filter to which one of the non-shifted signal and the shifted signal in the 90 ° phase shifter of the video signal processing unit is input; A phase comparator for performing a phase comparison between the output signal of the reference filter and the other signal of the 90 ° phase shifter. The comparison result of the phase comparator is fed back to the reference filter to set the reference frequency of the reference filter. A video signal processing circuit comprising: a filter automatic adjustment unit that maintains a predetermined frequency. 2. An oscillator comprising: an oscillator for generating a reference signal having a predetermined frequency; and a 90 ° phase shifter for shifting the phase of the reference signal by the oscillator to generate four signals having a phase difference of 90 °. A video signal processing unit that processes a video signal using the reference signal and the 90 ° phase shifter, and a phase difference between the four signals of the 90 ° phase shifter of the video signal processing unit is 90 A reference filter to which one of the two signals is input, and a phase comparator for comparing the output signal of the reference filter with the other signal of the 90 ° phase shifter. A filter automatic adjustment unit that feeds back the comparison result to the reference filter and maintains the reference frequency of the reference filter at a predetermined frequency; A first multiplier and a second multiplier for multiplying two signals having a phase difference of 180 ° among signals, an output of the first multiplier and an output of the second multiplier A video signal processing circuit comprising: a frequency conversion unit including an adder that adds