JP2002217763A - Input level display method, input level display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a display error of input level indication caused by a difference from reception frequencies. SOLUTION: A mapping function is generated by correcting an AGC(automatic gain control) value of a signal with a prescribed frequency or over at which the AGC value is largely changed depending on a characteristic of a high frequency circuit block by a prescribed value and stored in a memory 16. When a reception frequency at input level indication exceeds the prescribed frequency, after the AGC value is corrected by the prescribed value, the indication level of the input signal is calculated by the mapping function.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an input level display method for displaying, for example, a signal level input from an antenna, and a display device therefor.

[0002]

2. Description of the Related Art Broadcasting satellite (BS)
Parabolic antennas are used as satellite antennas in receivers that receive radio waves from e) and communications satellites (CS). Since such a parabolic antenna has a sharp antenna directivity, when installing the antenna, it is necessary to adjust the azimuth and the elevation angle so that the parabolic portion is properly directed to the satellite. For this reason, an ordinary satellite broadcast receiving apparatus is provided with an input level display function for quantifying and displaying the intensity of radio waves from satellite broadcasts as a guide when adjusting the azimuth and elevation of a parabolic antenna. I have.

Various input level display methods have been proposed in the past, and one of them is RF input from an antenna.
AGC for controlling the signal level to be constant
(Automatic Gain Control) circuit. In a receiving apparatus for displaying an input level using an AGC circuit, an AGC circuit is used in accordance with an RF signal level in a specific reception channel (reception frequency) and the RF signal level.
The control voltage output from the circuit (hereinafter referred to as “AGC
A mapping function created from the relationship with “voltage”) is stored in a memory or the like in advance. When the input level is displayed, for example, because the user performs antenna adjustment, the input level is determined based on the AGC voltage corresponding to the actually input RF signal level and the mapping function stored in the memory or the like. The signal level was calculated and displayed on the screen.

[0004]

By the way, as a receiving channel for displaying the input level in the above-described receiving apparatus, a frequency near the center of a frequency band that can be received by the receiving apparatus is usually selected. ing. For this reason, the conventional mapping function is created from the relationship between the input level in the same reception channel and the AGC voltage, and takes into consideration the characteristics of the RF circuit unit at this specific reception frequency. That is, the input level in a specific reception channel can be displayed almost accurately.

However, in recent years, satellite broadcasting (BS / C
The frequency band used in S) differs depending on each country such as the United States, Europe, and Japan. Further, the frequency band used differs depending on the satellite broadcasting company that provides the satellite broadcasting. For example, in the United States, 950 MHz to 1
There are satellite broadcasting companies that use the 450 MHz frequency band, and in Japan, 1060 MHz to 1520 MHz.
Also, there are satellite broadcasting companies using the frequency band of 1042 MHz to 1322 MHz. For this reason, when the user performs antenna adjustment, it may be considered that a specific reception channel for which a mapping function has been created in advance cannot be selected. Then, the user cannot select a specific reception channel, and in a different reception channel,
When the input level is displayed, there is a drawback that an incorrect input level is displayed because the characteristics of the RF circuit section are different. In particular, as the frequency of the receiving channel increases, the change in the characteristics of the RF circuit unit increases, and this tendency becomes remarkable.

Therefore, the present invention has been made in view of such a point, and an input level display method capable of reducing a display error even when an input level is displayed at a frequency other than a specific reception frequency. And a display device thereof.

[0007]

In order to achieve the above object, according to the present invention, there is provided an AGC circuit according to an AGC voltage for controlling an input signal to a predetermined level.
As an input level display method for displaying an input level based on a C value, a predetermined frequency threshold value data and an AGC value of a signal having a frequency exceeding the frequency threshold value data are corrected by a predetermined value. After storing the generated mapping function data, when the frequency of the input signal exceeds the frequency threshold, the display level value is corrected by the correction value obtained by correcting the input AGC value by a predetermined value and the mapping function data. After the calculation, the display level value is displayed as the input level value.

According to a second aspect of the present invention, there is provided an input level display device for displaying an input level based on an AGC value corresponding to an AGC voltage for controlling an input signal to a predetermined level. AGC according to
AGC voltage generating means for generating a voltage, predetermined frequency threshold data, and a signal having a frequency exceeding this frequency threshold data are mapped to a mapping function data generated by correcting the AGC value by a predetermined value. When the stored memory means and the frequency of the input signal exceed the frequency threshold value, a correction value obtained by correcting the input AGC value by a predetermined value, and a display level of the input signal by the mapping function data. A control unit for calculating the value and a display unit for displaying the display level value calculated by the control unit as an input level value are provided.

According to the first and second aspects of the present invention, A
For a signal having a variation in GC value that is equal to or greater than a predetermined frequency threshold value, the AGC value is corrected by the predetermined value to create a mapping function and stored in the storage means. When the frequency of the input signal to be inputted exceeds the frequency threshold value, the display level value of the input signal is calculated by a correction value obtained by correcting the AGC value by a predetermined value and the mapping function. The display error of the display level is reduced.

According to a third aspect of the present invention, an input level display method for displaying an input level based on an AGC value corresponding to an AGC voltage for controlling an input signal to a predetermined level is created for each frequency range. The plurality of mapping function data is stored, the display level value of the input signal is calculated using the mapping function data corresponding to the frequency range of the input signal to be input, and the display level value is displayed as the input level value. .

According to a fourth aspect of the present invention, there is provided an input level display device for displaying an input level based on an AGC value corresponding to an AGC voltage for controlling an input signal to a predetermined level. AGC according to
AGC voltage generation means for generating a voltage, storage means for storing a plurality of mapping function data created for each frequency range, and display level of an input signal using mapping function data corresponding to a frequency range of an input signal to be input Control means for calculating the value and display means for displaying the display level value calculated by the control means as an input level value are provided.

According to the present invention, mapping function data is created for each predetermined frequency range and stored in the storage means. Then, by calculating the display level value of the input signal using mapping function data corresponding to the frequency band of the input signal to be input, a display error of the display level is reduced.

[0013]

Embodiments of the present invention will be described below. FIG. 1 is a diagram showing a configuration of a high-frequency circuit block of a receiving apparatus corresponding to digital satellite broadcasting (BS or CS) according to the present embodiment. In this FIG.
The broadcast radio wave received by the parabolic antenna 1 is converted by the converter 2 into the first 1 GHz band (L band), for example.
After being converted to an intermediate frequency (IF) signal, the RF amplifier 3
Is input to The first I amplified in the RF amplifier 3
The F signal is supplied to an auto gain control (AG
Attenuation is controlled by an attenuator (attenuator ATT) 4 whose attenuation is controlled by a control voltage (AGC voltage) of a C: Automatic Gain Control (C) circuit 10 and then input to a mixer 6.

Although not shown, the local oscillator 5 is, for example, a voltage-controlled oscillator (VCO).
illator), a PLL (Phase Locked Loop) circuit, a crystal oscillator, etc., and outputs a frequency corresponding to the selected channel based on a reference signal output from the crystal oscillator and tuning data from the microcomputer 15. To be.

The mixer 6 extracts a baseband signal BB from the first IF signal by mixing (mixing) the first IF signal input from the attenuator 4 and the output of the local oscillator 5. The baseband signal BB extracted by the mixer 6 is input to the amplifier 7. The amplifier 7 is an amplifier whose gain can be controlled by the AGC voltage from the AGC circuit 10. The baseband signal BB controlled to a constant level in the amplifier 7 is input to the quadrature detector 8. The quadrature detector 8 converts the input baseband signal BB into an I signal and a Q signal. Then, after the I signal and the Q signal are digitally converted in the A / D converter 9, the signals are supplied to a digital demodulator at a subsequent stage (not shown).

The I and Q signals digitally converted by the A / D converter 9 are also branched and input to an AGC circuit 10 surrounded by a broken line. The AGC circuit 10
It comprises a C detector 11, a loop filter 12, a pulse width modulator (PWM) 13, and a low-pass filter (LPF) 14, and controls the attenuation of the attenuator 4 and the gain of the amplifier 7 so that the baseband signal BB is at a constant level. AGC voltage for controlling the AGC voltage is generated.

The AGC detector 11 detects peak values of the input I signal and Q signal. The peak values of the I signal and the Q signal detected by the AGC detector 11 are
2 and supplied to the PWM 13. PWM
Reference numeral 13 denotes a ΔΣ type pulse width modulator, for example, which generates a pulse wave subjected to pulse width modulation in accordance with a signal level input via the loop filter 12. PWM1
The pulse wave generated in 3 is fed back to the attenuator 4 and the amplifier 7 as an AGC voltage through an LPF 14 for removing a high-frequency component. The PWM 13 supplies value data (hereinafter, referred to as “AGC value data”) corresponding to a pulse width generated according to an input signal level to the microcomputer 15 via a bus line such as an I2C bus.

The microcomputer 15 has a memory 16
And controls the entire receiving apparatus based on various data stored in the receiving apparatus. When the input level is displayed, the data of the selected channel or the AG from the PWM 13 is displayed.
Based on the C value data, the mapping function data stored in the memory 16, and the like, an input level value for display to be displayed on a display (not shown) is calculated. Then, it generates on-screen data for displaying the calculation result as a numerical value and outputting it to the display control circuit 17. The display control circuit 17 performs display control for displaying a required display screen on the screen of the display device based on the input on-screen data.

In the receiving apparatus according to the present embodiment having the above-described configuration, the microcomputer 15 operates based on the mapping function created as described later.
Processing for calculating an input level, which will be described later, is executed.

Hereinafter, a method of creating a mapping function of the receiving apparatus according to the present embodiment and a processing operation executed by the microcomputer 15 based on the mapping function will be described. Hits the,
First, the background that led to the present invention will be described with reference to FIG.

FIG. 2 is a diagram showing an example of the relationship between the antenna input level and the AGC value in the receiving apparatus according to the present embodiment. As shown in FIG. 2, as the antenna input level decreases, the PGC of the AGC circuit 10 increases.
It can be seen that the AGC value output from the WM 13 increases as a whole, and that the AGC value increases as the frequency increases (increases) even at the same antenna input level. In particular, when the antenna input level is small, it can be seen that the tendency is remarkable.

As described above, as the reception frequency increases, the first I
This is because the characteristics of the RF circuit block change such that the gain of the amplifier 7 for amplifying the F signal becomes difficult to obtain, and the AGC voltage for controlling the gain of the amplifier 7 increases.

For this reason, the antenna input level at a specific reception channel (reception frequency) and the AG
If the mapping function is created from the relationship with the C value, the input level displayed on the display will be an erroneous level when antenna adjustment is performed using a reception channel other than the specific reception channel. In other words, since the conventional mapping function merely considers the characteristics of the RF circuit block at a specific reception frequency, the display of the antenna input level may be incorrect except at the specific reception frequency. turn into.

Therefore, in the present embodiment, the mapping function is obtained as follows. First, a method of obtaining a mapping function according to the first embodiment will be described with reference to FIGS.

FIG. 3 is a diagram showing an example of a procedure for creating a mapping function according to the first embodiment. The receiving apparatus according to the present embodiment uses the AGC circuit
Since the input level is displayed based on the value, the AGC value increases as the reception frequency increases, as shown in FIG. In particular, when the reception frequency becomes higher than a certain reception frequency, the rate of change in the AGC value increases due to the characteristics of the RF circuit block such as the amplifier 7. Therefore, first, as a procedure 1, the frequency threshold value fagc is determined from the relationship between the reception frequency and the AGC value. As a method of determining the frequency threshold, for example, while changing the reception frequency and the input power in the receiving apparatus, A
Assuming that the measurement result as shown in FIG. 4 is obtained when the GC value is measured, the rate of change of the AGC value greatly differs between the case where the reception frequency is 2150 MHz and the case where the reception frequency is lower than 2150 MHz. You can see that there is. Therefore,
In this case, for example, 2000 MHz is set to the frequency threshold fa.
gc.

Next, in step S2, for the AGC value at the reception frequency higher than the frequency threshold value fagc determined in step S1, the entire AGC value is shifted by a predetermined value X, so that the AGC value at the other reception frequency is changed.
The difference from the value should be small. For example, when the frequency threshold value fagc is set to 2000 MHz, the AGC value at 2150 MHz shown in FIG. Value.

After reducing the variation of the AGC value due to the reception frequency in this way, the procedure proceeds to step S3 where the AG
An approximate curve that minimizes the deviation of the C value is obtained.
Then, as step S4, a mapping function is created using the approximate curve obtained in step S3. That is, using this approximate curve, one mapping function for calculating the input level for display from the AGC value is created.

The data such as the mapping function data, the frequency threshold value fagc, and the predetermined value X created in this way are stored in the memory 16 of the receiving device in advance at the time of factory shipment.

The applicants also measured the variation of the AGC value due to the individual difference of the receiving device. FIG. 5 shows the measurement results. The measurement results shown in FIG. 5 are obtained by measuring AGC values when input power is changed at a specific reception frequency (for example, 950 MHz) in a plurality of reception devices. As can be seen from FIG. 5, it was found that there was almost no variation in the AGC value due to individual differences of the receiving devices. Therefore, when creating a mapping function by the above-described creation procedure, it is not necessary to consider variations due to individual differences of receiving apparatuses.

Next, the processing operation when the receiving apparatus according to the present embodiment, which stores the mapping function data and the like created as shown in FIG. explain. The processing operation illustrated in FIG. 6 is performed by the microcomputer 15 based on operation information obtained by performing a required operation on a remote commander (not shown) or an operation unit of the apparatus main body by a user, for example. Things.

In this case, the microcomputer 15
In step F1, it is determined whether or not the reception frequency of the currently selected channel is equal to or higher than the frequency threshold value fagc stored in the memory 16. Needless to say, the microcomputer 15 knows the current channel selection.

Here, when the reception frequency is equal to the frequency threshold fa,
If it is determined that the value is equal to or larger than gc, the microcomputer 15 proceeds to the process of step F2. In step F2, a correction value obtained by correcting the AGC value input from the PWM 13 by a predetermined value X stored in the memory 16 is represented by A
Let it be a GC value. That is, when the mapping function data is created at the factory, A
Since the GC value is subtracted by the predetermined value X, if it is determined that the reception frequency is equal to or higher than the frequency threshold value fagc, the correction is performed by subtracting the predetermined value X from the input AGC value in step f2. Let the value be the AGC value.

In the following step F3, an input level value for display is calculated based on the AGC value obtained in step F2 and the mapping function stored in the memory 16.

On the other hand, when it is determined in step F1 that the reception frequency is equal to or lower than the frequency threshold value fagc, the process proceeds to step F3 without performing the processing in step F2. Then, in step F3, the antenna input level value for display is calculated based on the AGC value actually input from the PWM 13 and the mapping function data stored in the memory 16. Then, on-screen data for displaying the input level value calculated in this way is created.

As described above, in the receiving apparatus of the present embodiment,
For a reception frequency exceeding the frequency threshold value fagc at which the difference in the AGC value increases due to the characteristics of the RF circuit block of the reception device, the input AGC value is again corrected by the predetermined value X, and then displayed by the mapping function. Is calculated. With this configuration, for a reception frequency exceeding the frequency threshold value fagc, the AGC value input from the AGC circuit is corrected by the predetermined value X, so that the input level display based on the mapping function data is performed. Is performed, the display error can be reduced. Further, for the reception frequency within the frequency threshold value fagc, the input level is displayed based on the mapping function data created by using the approximate curve, so that the display error can be reduced. That is, according to the receiving device of the present embodiment,
Even when the input level is displayed at a plurality of different reception frequencies, the display error can be reduced.

FIG. 7 shows an example of a measurement result obtained by measuring the reception frequency and the display error of the antenna level in the receiving apparatus according to the present embodiment. In FIG. 7, the conventional receiving apparatus shown for comparison with the receiving apparatus of this embodiment has a mapping function created and stored at a receiving frequency (1550 MHz). According to the measurement results shown in FIG. 7, the display error of the conventional receiver is increased when the reception frequency is 2000 MHz or higher, for example, whereas the reception frequency of the reception apparatus of the present embodiment is 2000 MHz or higher. It can be seen that the display error is small even when

Next, a method of obtaining a mapping function according to the second embodiment will be described with reference to FIG. FIG. 8 is a diagram showing an example of a procedure for creating a mapping function according to the second embodiment. In this case, first, in step S1
As 1, the frequency range farea is determined in consideration of the variation of the AGC value at the reception frequency. For example, in the case shown in FIG. 4, it is conceivable that one frequency range farea from 1350 MHz to 2000 MHz is set as one frequency range farea. Next, in step S12, an approximate curve that minimizes the deviation of the AGC value input from the PWM 13 for each frequency range farea determined in step S11 is determined. Then, in step S13, a mapping function is created using the approximate curve for each frequency range farea obtained in step S12. So in this case,
A mapping function for calculating an input level for display from an input AGC value is created for each frequency range farea.

Then, the plurality of mapping functions and the frequency range farea created in this way are stored in the memory 16 of the receiving device in advance at the time of factory shipment or the like.

Next, FIG. 9 shows a processing operation in the case where the receiving apparatus according to the present embodiment in which the mapping function data and the like created as shown in FIG.
This will be described with reference to the flowchart shown in FIG. Note that the processing operation shown in FIG. 9 is also executed by the microcomputer 15.

In this case, first, the microcomputer 15
Determines in step F11 which frequency range farea stored in the memory 16 is the reception frequency of the currently selected channel. In the subsequent step F12, the AGC value actually input from the PWM 13 and the frequency range f corresponding to the reception frequency are set.
The antenna input level for display is calculated based on the mapping function of the area.

That is, in such a receiving apparatus, the antenna input level for display is calculated using the mapping function data corresponding to the receiving frequency. Also in this case, it is possible to reduce a display error when the input level is displayed at a plurality of different reception frequencies.

In the above-described embodiment, a case has been described as an example in which a display error generated at a high reception frequency is corrected. However, for example, a display error generated at a low reception frequency may be corrected. Of course it is possible.

In this embodiment, the case where the present invention is applied to a receiver for satellite broadcasting has been described as an example. However, this is merely an example, and the present invention is applied to, for example, an output from an AGC circuit. The present invention can be applied to various electronic devices that can display an input level based on an AGC value.

[0044]

As described above, according to the first and second aspects of the present invention, for a signal exceeding a predetermined frequency threshold at which the AGC value changes due to the characteristics of the high-frequency circuit,
A mapping function created by correcting the AGC value by a predetermined value is stored in the storage unit. When the frequency of the input signal exceeds a predetermined frequency threshold,
After correcting the AGC value by a predetermined value, by calculating the display level value of the input signal by the mapping function, even when the input level is displayed at a plurality of input frequencies,
The display error can be reduced.

According to the third and fourth aspects of the present invention, a mapping function is created for each predetermined frequency range and stored in the storage means. Then, the display level value of the input signal is calculated using a mapping function corresponding to the frequency band of the input signal to be input. With this configuration, when the display level value of the input signal is calculated by the mapping function, the mapping function corresponding to the frequency of the input signal can be used. Display errors can be reduced.

Further, the present invention has an advantage that the present invention can be realized without increasing the cost because only a part of the software need be changed without any change in hardware.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of an RF circuit block of a receiving device according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating an example of a relationship between an antenna input level and an AGC value in the receiving device according to the present embodiment.

FIG. 3 is a diagram illustrating an example of a procedure for creating a mapping function according to the first embodiment;

FIG. 4 is a diagram showing a measurement result when an AGC value is measured while changing input power.

FIG. 5 is a diagram illustrating a measurement result when a variation in an AGC value due to an individual difference of an AGC circuit is measured.

FIG. 6 is a flowchart showing a processing operation when an input level is displayed using the mapping function created in FIG. 3;

FIG. 7 is a diagram showing a relationship between an antenna level and a display error.

FIG. 8 is a diagram illustrating an example of a procedure for creating a mapping function according to the second embodiment;

FIG. 9 is a flowchart showing a processing operation when displaying an input level using the mapping function created in FIG. 8;

[Explanation of symbols]

1 parabolic antenna, 2 converters, 3 amplifiers,
4 Attenuator (ATT), 5 local oscillator, 6
Mixer, 7 amplifier, 8 quadrature detector, 9 A / D converter, 10 AGC circuit, 11 AGC detector, 12 loop filter, 13 PWM, 14 LPF, 15 microcomputer, 16 memory, 17 display control circuit

Claims (4)

[Claims] 1. An input level display method for displaying an input level based on an AGC value corresponding to an AGC voltage for controlling an input signal to be at a predetermined level, comprising: predetermined frequency threshold data; For signals whose frequency exceeds the value data,
After storing mapping function data generated by correcting the C value by a predetermined value, when the frequency of the input signal exceeds the frequency threshold, the input AGC value is corrected by the predetermined value. A display level value is calculated based on the value and the mapping function data, and the display level value is displayed as an input level value. 2. An AGC voltage generator for generating an AGC voltage corresponding to an input signal level as an input level display device for displaying an input level based on an AGC value corresponding to an AGC voltage controlling an input signal to a predetermined level. Generating means, predetermined frequency threshold data, and a signal having a frequency exceeding the frequency threshold data,
Storage means for storing mapping function data created by correcting the C value by a predetermined value; and when the frequency of the input signal exceeds the frequency threshold, the input AGC value is stored in the predetermined value. Control means for calculating a display level value of the input signal based on the correction value corrected by the value, and the mapping function data; and display means for displaying the display level value calculated by the control means as an input level value. An input level display device, characterized in that: 3. An input level display method for displaying an input level based on an AGC value corresponding to an AGC voltage for controlling an input signal to be at a predetermined level stores a plurality of mapping function data created for each frequency range. And calculating a display level value of the input signal using the mapping function data corresponding to a frequency range of the input signal to be input, and displaying the display level value as an input level value. Method. 4. An AGC voltage generator for generating an AGC voltage corresponding to an input signal level as an input level display device for displaying an input level based on an AGC value corresponding to an AGC voltage controlling an input signal to be at a predetermined level. Generating means, storage means for storing a plurality of mapping function data created for each frequency range, and calculating the display level value of the input signal using the mapping function data corresponding to the frequency range of the input signal to be input An input level display device comprising: control means; and display means for displaying the display level value calculated by the control means as an input level value.