JPS59175287A - Automatic gain adjusting circuit - Google Patents

Abstract

PURPOSE:To automate the optimum adjusting function in terms of circuit by changing an RFAGC voltage in a vertical blanking period to change the gain and controlling the RFAGC operation in response to a noise signal generated in the occasion. CONSTITUTION:When a pulse signal (d) is applied during the vetical blanking period, an output voltage of the RFAGC circuit 6 lowers the gain of an RF circuit to a prescribed value or over. In this case, a signal during the period of the pulse signal (d) among detected and demodulated television receiving signals is extracted by a signal extracting circuit 12. This signal is a noise signal, which is converted into a DC voltage by a circuit 11 and given to an RFAGC circuit operation setting circuit 10 of the next stage as a control voltage. The RFAGC circuit operation setting circuit 10 moves the setting point of the RFAGC operation to the optimum point based on the supplied control voltage.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an self-help gain adjustment circuit (AGC circuit), and particularly to a voltage 1I41 adjustment in a high frequency automatic gain adjustment circuit of a television signal receiver.

In a television signal receiver, an RF stage (high frequency amplification stage) and an IF stage (intermediate frequency amplification stage) are normally installed in sequence at the antenna terminal, and an AGC circuit is applied to each stage to adjust the contrast depending on the level of the received radio waves. The video signal output is always kept constant to realize an optimal reception state. Such RF stage and IF
The AGC circuit provided in each stage is provided with an adjustment function (volume control) in order to obtain an optimum operating condition. The AGC adjustment function in the IF stage tends to be removed in recent television signal receivers, but the AGC adjustment function in the RF stage! The adjustment function remains, and this RFA
Adjustment of the GC circuit is one of the important functions that determines the performance of a television [No. 8 reception], and no RFAGC circuit that can be put into practical use with a circuit configuration that eliminates this adjustment has yet to be proposed.

First, FIG. 1 shows an outline of a conventional television signal receiver. The radio waves received by the antenna 1 are transmitted through an R1F circuit (also called a tuner circuit, which includes a heterodyne function)2. , I
The F circuit (intermediate frequency amplification stage) 3 then passes through the DET circuit (also called a demodulation circuit or a detection circuit, and may also include a video amplification function) 4 for sequential processing, and further for video processing/amplification/output. The signal is applied to the CRT 9 via the circuit 8 and displayed as an image and sound.

In the above television signal processing circuit, the IF circuit 3
An IFAGC circuit 5 or an RFAGC circuit 6 is connected to each of the RF circuits 2 and 2, and the gain in each amplifier circuit is controlled in order to always perform optimal reception operations. In particular, the RFAGC circuit 6 is provided with an RFAGC circuit operation setting circuit 7 for setting the AGC operation.

This RFAGC @ path wJ (\ setting circuit 7 is normally configured (R) by a volume control that sets the DC potential,
The DC potential is set so that the RFAGC circuit 6 operates under correct operating characteristics.

Figure 2 shows an RFAGC using FET as an RF amplifier.
The diagram does not show the relationship between the signal input and RF A G Cu voltage in circuit 6, and the shaded area where the signal input and RFA GC voltage are very low is a noise area that deteriorates the S/N of the receiver, and the signal input and RF A G C voltage The shaded area on the side where both are high is the cross-modulation saturation area that deteriorates the amplification monotonicity, and operation within either shaded area is not preferable, and the correct operating characteristic is the RFA sandwiched between both shaded areas.
The operation setting circuit 7 sets the RFAGC voltage in response to the signal input.
Used to determine within the set area. How the set point of the operating characteristics of the RF△GC circuit is kept within the setting FJI 14 determines the performance of the receiver, but in conventional receivers, the set point is usually set manually, Due to its difficulty, it had the disadvantage of pretending to be a very advanced 21-year-old, and the set points were not necessarily very dynamic.

Therefore, the main object of the present invention is to provide an RFAGC circuit that automates the edge adjustment and arching function.

The above-mentioned and other objects and objectives of the present invention will become clear from the following description with reference to the drawings.

To summarize this invention, the R of the television signal receiver is
The gain of the RFAGC voltage in the FAGC circuit is lowered to a predetermined level or more during a certain period of the vertical blanking period that does not affect the image on the screen. The noise signal generated in the reduced gain portion of the television signal demodulated by the RFAGC voltage with reduced gain is extracted, the extracted noise signal is converted into a DC voltage, and the RFAGC signal is generated using this DC voltage. It is something to control.

FIG. 3 is a block diagram of a television signal receiver according to one illustrative example of the present invention. Functional parts that are the same as those of the conventional device shown in FIG. 1 are designated by the same reference numerals. In the figure, antenna 1
The received radio waves are supplied to the CRT 9 via the RF circuit 2, IF circuit 3, DET circuit 4, and video/amplification/output circuit 8, and the video and audio are output. Here, the RF circuit 2 includes an RFAGC circuit 6, and the IF circuit 3 includes:
(2) The FAGC circuit 5 is connected and voltages for each AGC are provided. In particular, the RFAG'C circuit 6 has an AG
An RFAGC circuit excitation eye setting circuit 10 for automatically controlling CW till is connected, and is controlled based on the signal given from the operation setting circuit 10. , a signal extraction circuit 12 is connected via a circuit 11 including detection processing and integration functions.

The signal sampling circuit 12 is supplied with the demodulated signal @9 output from the DET circuit 4 or the video signal @b taken out from the video processing output circuit 8, and is also provided with a signal generated by a pulse generation circuit (not shown). A pulse signal @C with a vertical synchronization time interval of g, which sets a period within the vertical hoisting period, is applied, and a noise signal is extracted from the demodulated signal. The extracted noise signal is converted into a DC voltage by a waveform shaping circuit 11 including a waveform, amplification, detection, and integration circuit, and is applied to the operation setting circuit 10 as a control signal.

The operation setting circuit 10 is supplied with a pulse signal d (which does not necessarily have to match the pulse signal C) at a vertical synchronization time interval similarly generated by a pulse generation circuit, and is supplied with a sub-control from the circuit 11. In the layer where there is no voltage and the pulse signal d is not input, the output voltage of the RFAGe circuit 6 is within the noise region of FIG. 2.
The circuit 10 is designed to be close to A+, and is designed so that when the pulse signal d is applied, the output voltage of the RFAGC circuit 6 shifts roughly in the direction of decreasing the gain of the RF circuit 2. There is.

Next, the operation of the AGC control circuit consisting of the above-mentioned negative side will be explained together with the RFAGC voltage shown in FIG. 4 and the control voltages of each circuit not shown in FIG. 5.

First, m production setting circuit 10. Control from the processing circuit 11 (!l
In state 1, where the voltage is not applied and the pulse signal d is not input manually, the output voltage of the RFAG'C circuit 6 is set near point A1 within the noise region, and following this state, the pulse signal d is When applied, the output voltage of the RFAGC circuit 6 moves in a direction that roughly reduces the gain of the RF circuit 2. Note that the degree of this gain reduction is appropriately determined at the time of specific design of the circuit.

If the RFAGC output voltage with correct operating characteristics is represented by B'o in FIG. is in the direction of decreasing the RF gain, and with the vertical i pulse signal, the RF gain decreases as shown by B2, and these two voltages cause the RF gain to decrease.
GC, voltage is given. Note that the solid line in FIG. 4 does not indicate the #pJ relationship between the actual voltage and the human power signal when ideal operation is performed.

RF A whose output voltage level is single-layered as described above.
The television reception signal that has been detected and demodulated using the G C voltage has no noise at the input end of the signal extraction path 12 only during the pulse period t corresponding to the pulse signal C, as shown in FIG. The output signal is formed as a signal with an output power of δ. The noise generated during this pulse period is normally a biological noise with a 1 to 2 MH2 component.

In the IT number sampling circuit 12, a vertical pulse signal C for signal sampling is used to set the interval )υJ in the vertical 9M line period in advance.
is given, so from the input signal mentioned above, the fifth
A noise signal is extracted as shown in FIG. The noise signal 0 extracted from the circuit 11 is processed by the waveform shaping circuit 11 for amplification, detection, integration and, if necessary, direct current i & 1.
The width is processed and converted to DC voltage, and the control t! The voltage is applied to the next stage RFAGC operation setting circuit 10 as a voltage. The RFAGC circuit operation setting circuit 10 moves the RFAGC operation set point from A in the noise region in FIG. 2 to AO in the RFAGC setting region during correct operation based on the supplied control voltage. The degree after this is T
It is determined by the loop gain of the oII control circuit system.

By extracting the signal using the pulse signal and forming the control voltage as described above, the RFAGC voltage still exists in the noise region during the vertical pulse period, but
In other periods, the RFAGC is correct beyond the noise region.
wJIP#: can be done in the aR fixed range.

Incidentally, il) vertical pulse +911! The noise remaining in J does not appear on the screen at all because it is during the retrace period, and even for vertical 1σJ rotational excitation, the noise is located in the input section f! Since it is removed in the branch circuit, there is no shadow at all.

The R F, 'A G C self wJ setting excitation explained in the above example can be used for non-continuous AM (or F M ) signals such as television signals, and can also be used for () & in the vertical retrace period.
It is also possible to perform the same operation by using the horizontal retrace period instead of the horizontal retrace period. However, in the case of the same horizontal retrace period, it is desirable to remove mW of noise on the horizontal synchronization signal so as not to adversely affect the operation of the horizontal synchronization circuit. .

As described above, according to the present invention, it is possible to eliminate the adjustment function of the RFAGC circuit in the television signal processing circuit, and it is possible to automate the process by eliminating the hassle of manual adjustment. Further, variations in RFA'ac operation between channels in a television signal receiver can be reduced, and images can be stabilized. Furthermore, in the design of the tuner, vA'ii! Since the function is performed as a circuit, the degree of freedom in designing the noise figure gain between channels and bands increases, and the design
can do.

[Brief explanation of the drawing]

FIG. 1 is a diagram of a conventional television signal receiver blower. FIG. 2 is an explanatory diagram of the operating range showing the relationship between the input signal and the RF AGC voltage. FIG. 3 is a block diagram showing one embodiment of the present invention. FIG. 4 shows the RFAGCM pressure relationship 1! for explaining the operation of the same embodiment. il relationship diagram. , FIG. 5 is an explanatory diagram of main part control voltage generation for explaining the operation of this embodiment. In the figure, 2 is the RF circuit, 3 is the IF circuit, and 4 is 11.
)ET circuit 1.6 is RFAGC circuit, 10 is RFA G
C operation determination circuit, 11 is filtering, amplification, @valve circuit, C2
is A5@ sampling circuit. Representative Shin Kuzuno - (1 other person)
Figure 3 d c 2nd closed = Procedural amendment with minimal merit (method) 1. Indication of the case Japanese Patent Application No. 58-50876 2. Name of the invention Automatic gain vJ4 rectification circuit 3. Person making the amendment Representative Kata Yuhito Part 4, Agent 5, Date of amendment order June 28, 1988, 6 Figures 4 and 5 of the drawings to be amended, Figure 7, and contents of the amendment in Figures 4 and 5 as attached. Above Figure 4 Figure 5 Procedural Amendment (Voluntary initiative) Commissioner of the Japan Patent Office 1, Indication of the case, Japanese Patent Application No. 68-50876 2, Name of the invention Automatic gain adjustment circuit 3, To Hitoshi Katayama, representative of the person making the amendment. 5. Detailed description of the invention column and drawing υ of the specification to be amended, content of the amendment (1) Description - "Displayed as images and audio" in the second and third lines of page 3 is changed to the following: The sentence is corrected to .It is displayed as an image.In addition, in this Figure 1,
The audio circuit portion is omitted and not shown. (2) Page 5, lines 13 to 14 of the specification] "Video and audio" is corrected to "video." (3) “Signal 9” on page 6, line 5 of the specification - signal ■”
Correct to. (4) "Video signal b" on page 6, line 6 of the specification is corrected to "video signal ■." (5) "One voltage single power signal" in lines 5 and 6 of page 8 of the specification is corrected to "voltage one hour." (6) On page 9, line 6 of the specification, "after this" 3 is corrected to "this movement." (7) [Correct pulse signal bJ to "pulse signal C" on page 9, line 8 of the specification. (8) "Number gain" on page 10, lines 15 and 16 of the specification is corrected to "number, gain." (9) Figure 5 of the drawings is as attached. Figure 5 above

Claims (1)

[Scope of Claims] Means for providing a timing signal for setting a fixed period consisting of a vertical retrace period of a television signal, means for extracting noise occurring during the timing period in the demodulated television signal, and means for extracting the noise generated during the timing period in the demodulated television signal. An automatic gain adjustment comprising: means for converting the output signal of the extraction means into a DC voltage; and a circuit that sets a high frequency automatic gain adjustment circuit and supplies it to the high frequency automatic gain adjustment circuit based on the output of the conversion means. circuit.