JPH08330985A - Signal receiver - Google Patents

Abstract

PURPOSE: To provide the signal receiver which receives a signal in accordance with circumstances by the gain distribution according with the noise different by circumstances. CONSTITUTION: A radio wave to be received is received by an antenna 1 and is subjected to RF amplification and frequency conversion by a tuner 2 and is subjected to IF amplification by a video intermediate frequency amplification part 3, and the noise included in the signal detected by a video detection part 4 is detected by a noise level detection part 7. It is compared with a prescribed value by a microcontroller 8, and the comparison result is written in a memory 9. When a desired wave will be received, the comparison result of this desired wave is read out from the memory 9 and is given to an AGC adjustment part 5d, and an RF-AGC voltage adapted to the desired wave is obtained and is given to the tuner 2. An IF-AGC voltage is obtained in the same manner and is given to the video intermediate frequency amplification part 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a signal receiving device, and more particularly to a signal receiving device for receiving a television signal.

[0002]

2. Description of the Related Art FIG. 9 is a block diagram of a conventional signal receiving apparatus for receiving a television signal. In the figure, reference numeral 1 denotes an antenna which receives a television radio wave and forms a television signal. The television signal is received by the antenna 1, the signal desired to be received by the tuner 2 is selectively high-frequency amplified and converted into a video intermediate frequency signal, amplified by the video intermediate frequency amplification unit 3, and detected by the video detection unit 4. The resulting image signal is amplified by the image amplifying section 5, color signal processing is performed by the image processing section 6a, and displayed on the display section 6b.

When the electric field strength of the radio wave received by the antenna 1 fluctuates strongly, the video signal also fluctuates and the contrast of the screen changes. Therefore, a signal indicating the electric field strength is generated from the video signal and used for gain control in high frequency amplification and intermediate frequency amplification. The amplified video signal is given from the video amplification section 5 to the AGC detection section 5a, detected, and amplified by the AGC amplification section 5b to become an AGC voltage for controlling the amplification gain. This AGC voltage is low (or high) when the antenna input level is high (or low), and is given to the tuner 2 as the RF-AGC voltage that controls the high-frequency amplification gain of the tuner 2 by the AGC adjustment unit 5c, and also the video intermediate frequency amplification. The IF-AGC voltage for controlling the gain is given to the video intermediate frequency amplifier 3. Video intermediate frequency amplification unit 3, video detection unit 4, video amplification unit 5, AGC detection unit 5a, AGC amplification unit 5b, and AGC adjustment unit 5c
Is composed mainly of ICs.

FIG. 10 is a graph showing the gain distribution between the tuner 2 and the video intermediate frequency amplifier 3 in the signal receiving apparatus of FIG. In the figure, the solid line indicates the high frequency amplification gain of the tuner 2.
(Hereinafter referred to as RF gain), and the broken line indicates the video intermediate frequency amplification gain (hereinafter referred to as IF gain) of the video intermediate frequency amplification unit 3. When the electric field strength is a weak electric field, the reception level of the antenna 1 is low, and the RF gain and the IF gain are both maximum.
When the reception level of the antenna 1 becomes slightly higher than A (dB), the RF gain remains at the maximum and the IF gain is reduced. That is, the IF gain decreases from the maximum constant state, and the bending point α at which the broken line bends is set to the point where the antenna reception level is A (dB). When the electric field strength is a strong electric field, the reception level of the antenna 1 is B (dB) or more, and the RF gain is decreased and the IF gain is not decreased so much and is kept substantially constant. That is, the antenna reception level is B (dB) at the bending point β'where the IF gain is almost constant and the broken line is further bent, and at the bending point β where the RF gain is maximum and constant and the solid line is bent. Set to a certain point. The signal receiving device installed in an environment where the electric field strength is normal is set so that the antenna reception level B at the bending point β is about 60 dB.

When the antenna reception level is higher than B '(dB), the IF gain shown by the two-dot chain line and the RF gain shown by the one-dot chain line shows the case where the gain of the tuner 2 is set to be lowered in an environment with little noise. Show. These settings are performed by receiving a predetermined channel in a factory that manufactures the signal receiving device. Therefore, the inflection points α, β (or β ') that determine the RF gain and the IF gain are preset as the antenna reception levels A, B. That is, the gain distribution for each electric field strength of the television radio wave received by the signal receiving device is preset.

FIG. 11 is a circuit diagram of a main part of the AGC adjusting section 5c.
In the figure, 50 is a constant current source, and one end of the constant current source 50 is grounded. A fixed resistor 51 and a variable resistor 52 are connected in series between the power supply voltage and ground, and the connection point 50a of both resistors is npn.
The transistor 53 is connected to the base and the collector of the transistor 53 is connected to the power supply voltage. AGC voltage from AGC amplifier 5b 5d
2 and the base of an npn-type transistor 54, the collector of which transistor 54d determines the high frequency gain.
Connected to 1 and supplied with operating power. The emitters of both transistors 53 and 54 and the other end of the constant current source 50 are connected. Both transistors 53 and 54 have the same characteristics and operate as an emitter-coupled differential amplifier.

The circuit 5d1 for defining the high frequency gain generates an RF-AGC voltage, and the circuit 5d2 for defining the video intermediate frequency gain is IF-
Generate AGC voltage. The AGC adjustment unit 5c is an IC, but the variable resistor 52 is externally attached.

Next, the operation of the AGC adjusting section 5c will be described. When the antenna input level is low and the AGC voltage is high, the transistor 54 is in a fully on state, its collector current is large, and the circuit 5d1 that determines the high frequency gain outputs the RF-AGC voltage that maximizes the tuner gain. Intermediate frequency gain determining circuit 5d2 increases video intermediate frequency gain
Outputs IF-AGC voltage. When the antenna input level is high and the IF-AGC voltage is low, the current flowing through the transistor 54 decreases, and the circuit 5d1 that determines the high frequency gain outputs the RF-AGC voltage that reduces the tuner gain, and the circuit that determines the video intermediate frequency gain. 5d2 is IF-AG that lowers the image intermediate frequency gain
Outputs C voltage. That is, since the level input to the video intermediate frequency amplifying section 3 becomes substantially constant due to the decrease in the tuner gain, there is little room for gain adjustment in the intermediate frequency amplifying section 3.

When the value of the variable resistor 52 becomes large, the base voltage of the transistor 53 rises and the gain of the tuner 2 falls.
The SN ratio deteriorates. If the value of the variable resistor 52 becomes small,
The base voltage of the transistor 53 decreases, the gain of the tuner 2 increases, and the SN ratio is improved. Connection point 50a of both resistors 51 and 52
Is called RF delay point.

FIG. 12 is a graph showing the relationship between the voltage at the RF delay point 50a and the noise level. In the figure, the broken line is a graph showing the relationship between the voltage at the RF delay point 50a and the noise level in the signal receiving apparatus installed in an environment where the electric field strength is normal. RF delay point 50
When the voltage of a is lower than the maximum value, the noise level does not increase while the voltage is high, but the noise level gradually increases as the voltage decreases. When the voltage of the RF delay point 50a is v ₁ , the noise level is n _O
The displayed image is good. Further, when the voltage at the RF delay point 50a is lowered to a voltage v ₂ at which reception is impossible, the noise level suddenly increases and the noise level becomes n.
_It becomes _{L and the} SN ratio deteriorates rapidly. And the displayed image is disturbed. Here, n _L > n _O. This level difference n _L
-N _O is a noise margin, and v ₁ -v ₂ is a voltage value corresponding to the noise margin.

The solid line in FIG. 12 shows the relationship between the voltage at the RF delay point 50a and the noise level when this signal receiving device is installed in a noisy environment. When the voltage at the RF delay point 50a is v ₁ ′, the noise level becomes n _O and the displayed image is good. Further, when the voltage at the RF delay point 50a is lowered to a voltage v ₂ ′ at which the reception can still be expected, the noise suddenly increases, the noise level becomes n _L , and the displayed image is disturbed. Here, v ₁ > v ₂ ′> v ₁ ′. Further, if the voltage at the RF delay point 50a is raised too high, the electric field strength is sufficient and the RF gain is large, so that cross-modulation symptoms such as beat interference are exhibited.

[0012]

The conventional signal receiving apparatus is constructed as described above, and the factory adjusts the RF gain and the IF gain to unique values for each electric field strength. Therefore, since the gain distribution for each electric field strength of the high frequency amplification section and the video intermediate frequency amplification section of the tuner is fixedly set,
That setting is not necessarily appropriate in all environments receiving the signal. For example, when the noise is large in a weak electric field, the SN ratio is insufficient, and when the adjacent wave is also a strong electric field, there is a problem that beat interference occurs. The present invention has been made to solve such a problem, and by setting a gain distribution according to noise in an environment in which a signal receiving device is installed, a good receiving function can be achieved even in different receiving environments. It is an object of the present invention to provide a signal receiving device that exerts its effect.

[0013]

A signal receiving device according to a first aspect of the present invention converts a frequency of a signal amplified by the first amplifier circuit that selectively amplifies a signal desired to be received. A circuit, a second amplifier circuit for amplifying the signal of the frequency converted by the circuit, a detection circuit for detecting the signal amplified by the second amplifier circuit, and the first circuit according to the intensity of the signal detected by the detection circuit. In a signal receiving device provided with a gain adjusting circuit for adjusting the amplification gains of the first and second amplifying circuits, noise detecting means for detecting noise contained in the signal detected by the detecting circuit, and the noise detecting means for detecting the noise. It is characterized by further comprising: comparing means for comparing the noise level with a predetermined value; and correcting means for correcting the adjustment of the gain adjusting circuit according to the result of comparison by the comparing means.

The signal receiving device according to the second aspect of the invention is characterized in that, when the noise level is higher than a predetermined value, the correcting means corrects the amplification gain of the first amplifier circuit to be large.

A signal receiving device according to a third aspect of the present invention is characterized by including storage means for storing the result of comparison by the comparison means.

A signal receiving apparatus according to a fourth aspect of the present invention is characterized by including means for changing the contents stored in the storage means.

[0017]

In the first aspect of the invention, the noise detecting means selectively amplifies the signal desired to be received by the first amplifier circuit, converts the frequency, amplifies the signal by the second amplifier circuit, and detects the noise contained in the detected signal. The comparing means compares the level of the noise detected by the noise detecting means with a predetermined value, and the correcting means detects the gain of the first amplifying circuit and the second level according to the result of the comparison by the comparing means.
Correct the gain adjustment of the amplifier circuit. Therefore, the gain is distributed according to the noise level.

In the second aspect of the invention, when the noise level is higher than the predetermined value, the changing means corrects the amplification gain of the first amplifier circuit to be large.

In the third invention, the storage means stores the result of comparison by the comparison means. Therefore, the gain distribution is corrected according to the noise level based on the stored contents of the storage means.

In the fourth aspect of the invention, since the stored contents of the storage means can be changed, the stored contents can be manually changed according to the noise level.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below with reference to the drawings showing the embodiments thereof. FIG. 1 is a block diagram of a signal receiving apparatus according to the first embodiment. In the figure, reference numeral 1 denotes an antenna which receives a television radio wave and forms a television signal. The television signal is received by the antenna 1 and the signal desired to be received by the tuner 2 is selectively high-frequency amplified.
(This is the first amplification circuit) Converted to the video intermediate frequency signal, amplified by the video intermediate frequency amplification section 3 (this is the second amplification circuit), and detected by the video detection section 4 (this is the detection circuit The image signal becomes an image signal, is amplified by the image amplification unit 5, is subjected to color signal processing by the image processing unit 6a, and is displayed on the display unit 6b.

When the electric field strength of the radio wave received by the antenna 1 fluctuates strongly, the video signal also fluctuates and the contrast of the screen changes. Therefore, a signal indicating the electric field strength is generated from the video signal and used for gain control in high frequency amplification and intermediate frequency amplification. The amplified video signal is given from the video amplification section 5 to the AGC detection section 5a, detected, and amplified by the AGC amplification section 5b to become an AGC voltage for controlling the amplification gain. This AGC voltage is low (or high) when the antenna input level is high (or low), and is given to the tuner 2 as the RF-AGC voltage that controls the high frequency amplification gain of the tuner 2 by the AGC adjustment unit 5d, and also the video intermediate frequency amplification. The IF-AGC voltage for controlling the gain is given to the video intermediate frequency amplifier 3. Video intermediate frequency amplification unit 3, video detection unit 4, video amplification unit 5, AGC detection unit 5a, AGC amplification unit 5b, and AGC adjustment unit 5d
Is composed mainly of ICs. Further, the detected video signal is given from the video detection unit 4 to the noise level detection unit 7.

FIG. 2 is a block diagram of the noise level detecting section 7. The video signal detected in the figure is given to the SYNC separator 71 and the noise extraction circuit 73. The detected video signal is separated by a SYNC separator 71 into a horizontal synchronizing signal portion, and a waveform shaping circuit 72 shapes the pulse into a pulse indicating the start time point and the end time point of the horizontal sync signal, and a noise extraction circuit 73.
The noise included in the horizontal sync signal is extracted at, the peak of the noise is detected by the peak detection circuit 74, and the integration circuit 75
Is integrated and detected as a noise level. This is noise detection means.

Returning to FIG. 1, description will be made. In this way, the noise level detecting section 7 detects the noise level included in the horizontal synchronizing signal and gives it to the microcontroller 8. The microcontroller 8 stores a noise limit value n _L for ensuring good reception. Then, in order to perform appropriate gain distribution, the digital values obtained by A / D conversion by the A / D converter 8a having the built-in noise level given by the noise level detection unit 7 for all channels desired to be received and Delay point data v, which is a natural number, is determined based on the stored noise limit value n _L and is written in the memory 9.

FIG. 3 is a flowchart showing a procedure in which the microcontroller 8 determines the delay point data based on the noise level. First, the channel number CH to be received is set to 1 (S1), the delay point data v is set to its maximum value v _max (S2), the television signal of the set CH is received (S3), and there is sensitivity. It is determined whether or not (S4),
If there is a feeling, this is compared with the noise limit value n _L for ensuring good reception, and it is determined whether the received noise exceeds n _L (S5). This is the comparison means. NO
In case of, subtract 1 from v to make a new v (S6), step
_Move to S3, and if YES, add v _marg to v and create new v
(S7). Here, v _marg is a value corresponding to a noise margin and is for receiving a desired wave while maintaining a good SN ratio. Next, write a new v into the memory 9 (S
8) Add 1 to CH to make a new CH (S9), and judge whether the new CH exceeds 62 (S10). If NO, step
Move to S2, and if YES, end the procedure. Then, if there is no sense in step S4, the process proceeds to step S9.

This procedure is executed when the signal receiving device is installed. That is, the delay point data is gradually decreased from v _max to decrease the gain. Therefore, the high frequency gain of the tuner 2 is lowered to some extent, the noise peculiar to the installation location of the signal receiving device causes the SN ratio to deteriorate rapidly, and the detected noise level exceeds the noise limit value n _L. A value obtained by adding a voltage margin to the delay point data at this time, that is, a voltage value of the RF delay point for good reception is stored in the memory. This is done for all receivable channels. Therefore, in the environment in which the signal receiving device is installed or relocated, the gain distribution according to noise is set each time, and the SN ratios of all receivable channels can have a predetermined noise margin.

When receiving a television signal desired to be received, the microcontroller 8 reads the delay point data corresponding to the television signal from the memory 9 and uses the D / A converter 8b having a value inversely proportional to the value.
D / A converted into analog DC voltage, which is applied to AGC adjustment section 5d. That is, the delay point data is large and the analog DC voltage is small in a place where the noise environment is bad. This is the correction means.

FIG. 4 is a circuit diagram of a main part of the AGC adjusting section 5d.
In the figure, 50 is a constant current source, and one end of the constant current source 50 is grounded. Two fixed resistors 51 between the power supply voltage and ground
a, 52a are connected in series, and the connection point of both resistors 51a, 52a
50a is an RF delay point, to which a direct current voltage, which is delay point data from the microcontroller 8, is applied and is also connected to the base of the npn type transistor 53. The collector of the transistor 53 is connected to the power supply voltage. The AGC voltage from the AGC amplifier 5b is connected to the circuit 5d2 that determines the video intermediate frequency gain and the base of the npn-type transistor 54, and the collector of that transistor is connected to the circuit 5d1 that determines the high frequency gain and is supplied with operating power. . The emitters of both transistors 53 and 54 and the other end of the constant current source 50 are connected. The two transistors 53 and 54 have the same characteristics and operate as an emitter-coupled differential amplifier. The circuit 5d1 that determines the high frequency gain is RF
-A circuit that generates the AGC voltage and determines the video intermediate frequency gain 5d
2 produces the IF-AGC voltage. Next, the operation of the AGC adjustment section 5d will be described.

When the antenna input level is low and the AGC voltage is high, the transistor 54 is in a completely ON state,
The collector current is large, and the circuit that determines the high frequency gain is 5d.
1 outputs the RF-AGC voltage that maximizes the tuner gain,
The circuit 5d2 for determining the video intermediate frequency gain outputs the IF-AGC voltage for increasing the video intermediate frequency gain. When the antenna input level becomes high and the IF-AGC voltage is low, the transistor 54
The current flowing therethrough decreases, and the circuit 5d1 that determines the high frequency gain outputs the RF-AGC voltage that reduces the tuner gain, and the circuit 5d2 that determines the video intermediate frequency gain outputs the IF-AGC voltage that reduces the video intermediate frequency gain. That is, since the level input to the video intermediate frequency amplifying section 3 becomes substantially constant due to the decrease in the tuner gain, there is little room for gain adjustment in the intermediate frequency amplifying section 3. When a television signal is received in a place where the noise environment is bad, since the DC voltage as the delay point data is small, the base voltage of the transistor 53 is small, the gain of the tuner 2 is increased, and the SN ratio is improved. Delay point data is microcontroller 8
Can be set automatically as well as manually.

FIG. 5 is a schematic diagram of an operation panel for manually changing the delay point data in the signal receiving device of FIG. In the figure, 11 is a display for displaying a channel number to be received or delay point data of the channel number, and a button for designating a channel number to be displayed on the display is a channel designation button 12
In addition, it is composed of two buttons for designating the tenth place and the first place, and when the channel designation button is operated, a desired channel number is displayed on the display 11.

The data setting button 13 consists of two buttons, + and-, and when the + (or-) button is operated, the delay point data displayed on the display 11 is incremented (or decremented) by one. .
When the memory button 14 is operated with the channel number displayed on the display 11, the displayed channel number disappears and the delay point data corresponding to that channel number is read from the memory 9 (see Fig. 1). And is displayed on the display 11.

When the memory button 14 is operated while the delay point data is being displayed on the display 11, the displayed delay point data is stored in the memory 9
The data that has been written to and is displayed will be lost. Display by operating these buttons 12, 13, 14
The microcontroller 8 performs display on the memory 11 and reading / writing on the memory 9.

Next, an algorithm for changing the delay point data by operating the operation buttons on the operation panel will be described. FIG. 6 is an algorithm showing a procedure for changing the delay point data. First, operate the channel specification button 12 to specify which channel the delay point data to be changed is displayed and display the channel number on the display 11 (S1), and operate the memory button 14 to display the channel number. Display the delay point data v of
It is displayed on 11 (S2) and it is judged whether or not the RF gain is increased (S2).
3) If YES, increment v by the data setting button 13 to v + 1 (S4), display v + 1 on the display 11 (S5), and determine whether to further change the RF gain (S4).
6), If NO, operate the memory button 14 to display
The delay point data displayed in 11 is stored in the memory 9
Write to (S7), end the procedure, and if YES, step
Move to S3. If NO in step S3, it is determined whether or not the RF gain is reduced (S8). If NO, the process proceeds to step S3, and if YES, decrements v with the data setting button 13 to v-1. (S9), v-1 is displayed on the display 11 (S10), and the process proceeds to step S6.

Since the delay point data can be changed by operating the operation button in this way, for example, when the interference from the adjacent channel is strong, the RF gain can be lowered to reduce the interference. That is, since the delay point data automatically set by the machine can be changed manually, the gain distribution can be set more finely in the environment where the signal receiving device is installed. Therefore, the service person can change the delay point data only for the disturbed channel.

FIG. 7 is a block diagram of a signal receiving apparatus according to the second embodiment. When the television signal desired to be received is received, the microcontroller 8 reads out the delay point data corresponding to the television signal from the memory 9, and gives the delay point data and the clock to the AGC adjusting section 5e. The AGC adjustment unit 5e changes the AGC voltage from
RF-AGC voltage is generated and given to the tuner 2.
IF-AGC voltage is generated from the voltage and the video intermediate frequency amplifier 3
Give to. Since other configurations are similar to those of the signal receiving apparatus shown in FIG. 1, the same parts are designated by the same reference numerals and the description thereof will be omitted.

FIG. 8 is a circuit diagram of an essential part of the AGC adjusting section 5e shown in FIG. In the figure, 55 is a D / A converter, which converts the delay point data given from the microcontroller 8 into an analog DC voltage by D / A-converting it based on a given clock. RF, the connection point
Give to delay point 50a. Since other configurations are the same as those in FIG. 4, the same parts are designated by the same reference numerals and the description thereof will be omitted. With this configuration, the D / A converter 55
The path of the analog DC voltage to the RF delay point 50a is shortened, and the influence of noise from this peripheral circuit on this path is reduced. Therefore, the SN ratio of all receivable channels can have a larger predetermined noise margin.

[0037]

As described above, according to the first invention,
The noise contained in the received signal is compared with a predetermined value, and the gain distribution is corrected according to the comparison result.
It has an excellent effect of maintaining good SN ratio, no beat interference, and good reception function.

According to the second aspect of the present invention, when the noise level is higher than the predetermined value, the amplification gain of the first amplifier circuit becomes large, so that the high frequency gain becomes large and the SN ratio is improved, so that good reception is achieved. It has an excellent effect of exerting its function.

According to the third aspect of the invention, since the storage means for storing the result of comparing the noise level with the predetermined value is provided,
When the noise environment changes, the stored contents are updated in accordance with the environment, so that an excellent effect of always exhibiting a good reception function is achieved.

According to the fourth aspect of the present invention, since the stored contents can be manually operated and changed, the gain distribution can be finely corrected according to the change of the receiving environment.

[Brief description of drawings]

FIG. 1 is a block diagram of a signal receiving device according to a first embodiment.

FIG. 2 is a block diagram of a noise level detection unit in FIG.

3 is a flow chart showing a procedure in which the microcontroller of FIG. 1 defines delay point data.

FIG. 4 is a circuit diagram of a main part of the AGC adjusting unit in FIG.

5 is a schematic diagram of an operation panel for manually changing the delay point data in the signal receiving device of FIG.

FIG. 6 is an algorithm showing a procedure for changing the delay point data by operating the operation panel of FIG.

FIG. 7 is a block diagram of a signal receiving device according to a second embodiment.

FIG. 8 is a circuit diagram of a main part of the AGC adjusting unit of FIG.

FIG. 9 is a block diagram of a conventional signal receiving device.

10 is a graph showing gain distribution of the signal reception device of FIG.

11 is a circuit diagram of a main part of the AGC adjusting unit in FIG.

12 is a graph showing the relationship between the voltage at the RF delay point of FIG. 10 and the noise level.

[Explanation of symbols]

2 tuner, 3 video intermediate frequency amplifier, 5c, 5d, 5e AG
C adjuster, 7 noise level detector, 8 microcontroller, 9 memory, 50a RF delay point.

Claims (4)

[Claims] 1. A first amplifier circuit for selectively amplifying a signal desired to be received, a circuit for converting a frequency of a signal amplified by the first amplifier circuit, and a signal of a frequency converted by the circuit. A second amplifier circuit, a detection circuit for detecting the signal amplified by the second amplifier circuit, and a gain adjustment for adjusting the amplification gain of the first and second amplifier circuits according to the intensity of the signal detected by the detection circuit. A signal receiving device including a circuit; a noise detecting unit that detects noise included in the signal detected by the detecting circuit; a comparing unit that compares the noise level detected by the noise detecting unit with a predetermined value; A signal receiving apparatus comprising: a correction unit that corrects the adjustment of the gain adjustment circuit according to the result of comparison by the comparison unit. 2. The signal receiving apparatus according to claim 1, wherein when the noise level is higher than a predetermined value, the correction means corrects the amplification gain of the first amplifier circuit to be large. 3. The signal receiving apparatus according to claim 1, further comprising a storage unit that stores the result of comparison by the comparison unit. 4. The signal receiving apparatus according to claim 3, further comprising means for changing the contents stored in the storage means.