JP3134412B2 - Antenna level measuring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an antenna level measuring device, and more particularly to an antenna level measuring device suitable for a satellite broadcast receiving system.

[0002]

2. Description of the Related Art A satellite broadcasting receiving system including a receiving antenna for satellite broadcasting, a tuner, and the like may be capable of displaying a reception level of a signal received by an antenna in order to receive satellite broadcasting more effectively. is there. This measures the reception level of the signal received by the antenna using the AGC level of the tuner.

[0003]

As described above, when an attempt is made to measure the reception level of a signal received by an antenna using the AGC level of the tuner, the frequency of the noise generated by the antenna converter and the frequency of the gain of the tuner are measured. There is a problem that the AGC value may change depending on the characteristics.

[0004] The following method is known as a method for determining the signal reception level at the antenna. For example, a method of simply subtracting the noise level corresponding to each channel from the reception level of the radio wave of each channel of satellite broadcasting, calculating the noise level by equal division, and calculating the noise level equally divided from the reception level of the radio wave of each channel This is a method of subtracting, or a method of subtracting a predetermined noise level. Hereinafter, description will be made with reference to FIGS. 7 and 8.

In FIGS. 7 and 8, the horizontal axis represents frequency, and the vertical axis represents signal or noise level. 7 and 8, f3, f7, f1
Reference numerals 1 and f15 represent the frequencies of the third channel of satellite broadcasting (hereinafter simply referred to as CH), 7CH, 11CH, and 15CH, respectively. Further, LB3, LB7, LB11, LB15
Represents reception levels at antennas of 3CH, 7CH, 11CH, and 15CH, respectively. Further, LNa to LNc are:
It shows the characteristics of noise generated in the antenna converter.

As shown in FIGS. 7 and 8, 3CH,
Since the radio waves of the 7CH and 11CH are transmitted from the broadcasting satellite at substantially the same level, the reception levels LBi are also substantially the same. On the other hand, only for the 15CH, the radio wave is transmitted from the broadcast satellite at a slightly lower level, so that the reception level LBi is slightly lower.

First, a method of simply subtracting a noise level corresponding to each channel from a reception level of a signal of each channel will be described with reference to FIG.

The characteristic of the noise level generated by the antenna converter is denoted by LNa in FIG. 7, and the noise levels corresponding to each channel are denoted by LNa3, LNa7, LNa11, and LNa15.
As shown in FIG. 7, the reception level of the signal of each channel is [LB3-LNa3], [LB7-LNa3].
7], [LB11-LNa11], and [LB15-LNa15].

[0009] Although the reception levels of the 3CH to 11CH signals are originally the same, they vary from channel to channel due to noise, resulting in a level difference. That is, as shown in FIG. 7, the reception level of the signal in each channel is [LB3-LNa3], [LB7
-LNa7], [LB11-LNa11], [LB15-LNa1
5].

Next, a method of subtracting equally divided levels will be described with reference to FIG. FIG. 8 shows signals or noise levels of 3CH, 7CH, 11CH, and 15CH of satellite broadcasting as in FIG. Also, LNa
Represents the characteristic of noise generated in the antenna converter as in FIG.

In FIG. 8, when the maximum level of noise is NOmax and the minimum level of noise is NOmin,
The range of the noise level is represented as [NOmax-NOmin].
Assuming that the number of broadcastable channels is m (currently m = 16), the noise level per channel is [(NOmax−
NOmin) / m].

Assuming that the target channel number is n, the noise level LNO in each channel
i is represented by the following equation. LNOi = [((NOmax-NOmin). (Mn)) / m]

For example, as shown in FIG. 8, the reception level of the satellite broadcast radio wave in each channel is [LB3-
LNO3], [LB7-LNO7], [LB11-LNO11],
[LB15-LNO15].

In the case of the method of subtracting the equally divided levels, as in the method shown in FIG. 7, that is, the method of simply subtracting the noise level corresponding to each channel from the radio wave reception level, Although the reception levels of CH3, CH7, and CH11 are originally the same, they change for each channel due to noise, resulting in a level difference.

Next, a method of subtracting a predetermined noise level will be described. In this method, the maximum noise level NOmax shown in FIG. 8 is set as a predetermined noise level, and the maximum noise level NOmax is subtracted from the reception level of the signal of each channel. That is, [LB3-NOmax], [LB7-NOmax]
max], [LB11-NOmax], [LB15-NOmax] and the like.

However, in the case of the method of subtracting a predetermined noise level, even if there is a sufficient reception level to display an image, if the maximum noise level NOmax is subtracted, the video signal displayed on the display screen is reduced. May be displayed as "0".

For example, the reception level of 15CH shown in FIG. 8 is lower than the reception levels of the other channels, but is a level that can display images on the display sufficiently.

However, since the reception level of 15CH shown in FIG. 8 is slightly lower than the maximum level NOmax of the noise, the level of the video signal of 15CH is changed to the maximum level NOmax.
Is subtracted, "0" indicating that display of an image is impossible is displayed on the screen.

Accordingly, it is an object of the present invention to provide an antenna level measuring apparatus which can display the reception level of an antenna even in the case of a weak electric field and can display the relative level between the reception levels of the signals of each channel. is there.

[0020]

In the antenna level measuring apparatus according to the present invention, means for comparing the level of the signal received by the antenna with the level of the noise, and the level of the signal is determined based on the comparison result. If the level is lower than the noise level, the level of the carrier noise is displayed.
When the signal level is higher than the noise level, a predetermined value is subtracted from the signal level to display the signal.

[0021]

The level of a signal received by the antenna is compared with the level of noise. If the reception level of the signal is lower than the noise level, for example, the highest level of the noise based on the comparison result, the level of the carrier against the noise is obtained and displayed.

On the other hand, when the signal reception level is higher than the noise level, a predetermined level, for example, the maximum noise level is subtracted from the signal reception level and displayed.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS. In this embodiment, an example is described in which the antenna level measuring device is applied to a satellite broadcast receiving system.

FIG. 1 shows a block diagram of an antenna level measuring device. In the configuration of FIG. 1, a satellite broadcast signal received by a BS antenna (hereinafter simply referred to as an antenna) 1 is supplied to a converter 2.

In the converter 2, the frequency of the satellite broadcast signal is converted into a first intermediate frequency signal. Then, the first intermediate frequency signal is supplied to the tuner 3.

In the tuner 3, a signal of a desired channel is selected and demodulated based on channel selection data supplied from the CPU 15 described later. By the demodulation, a video signal, an audio signal, and the like are obtained.

That is, the first intermediate frequency signal supplied from the converter 2 is amplified, and based on the above-mentioned channel selection data,
A desired channel is selected from the first intermediate frequency signal,
It is converted to a second intermediate frequency signal. Then, the converted second intermediate frequency signal is amplified, and the video signal, the audio signal, and the like are demodulated by the FM demodulation circuit. The demodulated video signal is supplied to a video signal processing circuit 4, and the audio signal is supplied to an audio signal processing circuit (not shown).

In the video signal processing circuit 4, the demodulated video signal is subjected to processes such as de-emphasis, energy diffusion signal removal, and video amplification. Then, the processed video signal is supplied to the adder 5.

Further, from the video signal processing circuit 4, the demodulated video signal is supplied to the signal level judgment circuit 6, and is supplied to the tuner 3 as an AGC control signal. Then, from the video signal processing circuit 4, a noise component obtained by selecting a predetermined channel is supplied to the noise level determination circuit 7.

The signal level determination circuit 6 determines the reception level of the signal at the antenna 1 based on the video signal supplied from the video signal processing circuit 4, and forms a signal representing the reception level. The signal indicating the reception level is supplied to a comparator 8 and a level operation circuit 9.

In the noise level determination circuit 7, the level of the noise supplied from the video signal processing circuit 4 is obtained, and a signal representing the level of the noise is formed. The signal representing the noise level is supplied to a comparator 8 and a level operation circuit 9.

The comparator 8 compares the signal reception level at the antenna 1 with the noise level. A signal representing the result of the comparison is supplied to the level operation circuit 9.

The level calculation circuit 9 performs a predetermined calculation based on the result of comparison between the signal reception level at the antenna 1 and the noise level. The signal reception level and the noise level will be described below with reference to FIGS.

FIGS. 2 to 4 show an example in which at least one of the signal reception levels at the antenna 1 is lower than the maximum noise level. FIG.
In this case, the case where all the reception levels of the signals received by the control unit are higher than the highest level of the noise is shown.

In FIGS. 2 to 5, the horizontal axis represents frequency, and the vertical axis represents signal or noise level. Further, f3, f7, f11, and f15 are the third channels of satellite broadcasting (hereinafter simply abbreviated as CH), 7 respectively.
The frequencies of CH, 11CH and 15CH are shown. Furthermore, LB
3, LB7, LB11, and LB15 are 3CH, 7CH, 11
The reception levels of the antennas 1 for CH and 15CH are shown.

As apparent from FIGS. 2 to 5, 3CH,
Since the radio waves of the 7CH and 11CH are transmitted from the broadcasting satellite at substantially the same level, the reception levels LBi are also substantially the same. On the other hand, only for the 15CH, the radio wave is transmitted from the broadcast satellite at a slightly lower level, so that the reception level LBi is slightly lower.

The noise level can be obtained by measuring the noise level of several off-channels, for example, BS0CH where broadcast waves are not transmitted.

In FIGS. 2 to 5, LN represents the characteristics of noise generated in the antenna converter. In this noise characteristic, the highest level of noise is NOmax, and the lowest level of noise is NOmin.

[1] When the signal reception level at the antenna 1 is lower than the maximum noise level FIG. 2 shows the case where all the signal reception levels at the antenna 1 are lower than the maximum noise level NOmax. FIG. 3 shows a case where only the reception level of CH 15 is lower than the maximum noise level NOmax among the signals received by the antenna 1.

As shown in FIGS. 2 and 3, when the reception level of the signal received by the antenna 1 is lower than the maximum noise level NOmax, the carrier noise level, that is, the so-called C / N level becomes higher. Desired.

Hereinafter, a method of obtaining the C / N level will be described with reference to FIG. In FIG. 4, the range of the noise level is represented as [NOmax-NOmin]. If the number of broadcastable channels is m (currently m = 16), the noise level per channel is [(NOmax−NOmin) /
m].

Assuming that the target channel number is n, the noise level LNOi in each channel is represented by the following equation (1). The noise level LNOi represented by the equation [1] is an offset level subtracted from the reception level of each channel.

LNOi = [((NOmax−NOmin) · (mn)) / m] (1)

Therefore, if the noise level LNOi of each channel is expressed by the formula [1] for 3CH, for example, the following is obtained. LNO3 = [((NOmax-NOmin). (16-3)) / 16]

Based on the above equation [1], the C / N level CNi of the satellite broadcast radio wave in each channel can be expressed as follows. CN3 = [LB3-LNO3] CN7 = [LB7-LNO7] CN11 = [LB11-LNO11] CN15 = [LB15-LNO15]

As a result, it is possible to display the reception level at the antenna 1 to the limit level at which the satellite broadcast image can be reproduced.

In the level operation circuit 9, a control signal for displaying the reception level is formed based on the C / N level CNi obtained by the above equation [1]. The control signal is supplied to the CPU 15.

That is, when [CNi> 0], the C / N level CN
A control signal for displaying i is supplied to the CPU 15,
When [CNi ≦ 0], a control signal for displaying “0” is supplied to the CPU 15.

[2] When All Reception Levels of Signals Received by Antenna 1 Are Higher than Maximum Noise Level NOmax FIG. 5 shows that all reception levels of signals received by antenna 1 are higher than the maximum noise level. It is a figure which shows the case where it is higher than NOmax.

In the case shown in FIG. 5, the antenna 1
A predetermined noise level is subtracted from the reception level LBi of the signal received at step (1) to obtain an absolute value.

Hereinafter, description will be made with reference to FIG. In FIG. 5, the reception level LBi of the signal received by the antenna 1 is shown.
Is greater than the highest level of noise NOmax,
The absolute value SNOi of the difference between the signal reception level LBi in each channel and the maximum noise level NOmax is obtained.

The absolute value SNOi is expressed by the following equation (2). In forming the absolute value SNOi, the absolute value SNOi is not limited to the maximum noise level NOmax, but another level, for example, an average value can be used.

SNOi = | LBi-NOmax | ... [2]

Therefore, as shown in FIG. 5, the reception level of the satellite broadcast video signal is [SNO3 = LB3-NOmax
], [SNO7 = LB7-NOmax], [SNO11 = LB11]
-NOmax], [SNO15 = LB15-NOmax].

When the absolute value SNOi is obtained by the above equation (2), the relative reception level of the video signal of each channel is displayed as it is in a range exceeding the maximum noise level NOmax. You.

Then, in the level calculation circuit 9, a control signal for displaying the reception level is formed based on the absolute value SNOi obtained by the above equation (2). The control signal is supplied to the CPU 15.

In the CPU 15, a signal for performing a predetermined display on the screen, for example, a character code is formed based on the control signal supplied from the level operation circuit 9. The signal is supplied to the character generator 10. The tuning data is supplied from the CPU 15 to the tuner 3.

In the character generator 10, the CPU
Data for displaying characters (hereinafter, referred to as character display data) is formed on the basis of the signal supplied from 15. The character display data is supplied to the adder 5.

In the adder 5, the above-mentioned video signal processing circuit 4
The above-mentioned character display data is added to the video signal supplied from, and a new video signal is formed. This video signal is supplied to the CRT display 12.

On the CRT display 12, for example, a display on the screen as shown in FIG. 6 is made. In the figure, in the area AR1 in the upper right column of the screen indicated by 21, the channel number [= n] of the currently received satellite broadcast is shown.

In the center area AR2 of the screen 21, the current reception level and the maximum reception level of the satellite broadcast 3CH signal received by the antenna 1 are indicated by numerals. For example, in the case of the C / N level CNi [= 0] as described above, the reception level “0” is displayed in the area AR2.

Further, the reception level of the currently receiving channel is displayed as a bar in the central area AR3 of the screen 21. For example, in the figure, the more the bar is displayed in the direction of arrow A, the stronger the reception level at the antenna 1 becomes. When the bar is displayed in the direction opposite to the arrow A, the reception level at the antenna 1 becomes lower. become weak.

In this embodiment, the signal level determination circuit 6
Noise level determination circuit 7, comparator 8, level operation circuit 9
It is also possible to realize the function of each circuit block such as in software.

According to this embodiment, the satellite broadcast signal received by the antenna 1 and the noise are compared in level by the comparator 8, and the reception level LBi of at least one signal is
If the noise level is lower than the maximum noise level NOmax, the offset level is subtracted, the C / N level CNi is obtained and displayed, and all the reception levels LBi of the signal received by the antenna 1 are equal to the noise maximum level. When the level is higher than the level NOmax, the maximum level NOmax of the noise is subtracted, and the absolute value SNOi is obtained and displayed. Therefore, even in the case of a weak electric field, the reception level LBi of the signal at the antenna 1 can be displayed.
When all the reception levels of the signal received by the antenna 1 are equal to or higher than the maximum noise level NOmax, the relative level between the signal reception levels can be displayed.

[0065]

According to the antenna level measuring apparatus of the present invention, the level of a signal received by an antenna is compared with the level of noise, and when the level of the signal is lower than the level of noise, for example, the maximum level of noise. Is obtained by subtracting the offset level from the signal level and calculating and displaying the C / N level. If the signal level is higher than the noise level, a predetermined level is subtracted from the signal level, and the absolute value is calculated. Since it is obtained and displayed, there is an effect that the reception level of the signal at the antenna can be displayed even in the case of a weak electric field, and when all the reception levels of the signal received by the antenna are above a predetermined noise level. Has an effect that a relative level between signal reception levels can be displayed.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention.

FIG. 2 is a diagram illustrating a relationship between a signal reception level and a noise level.

FIG. 3 is a diagram illustrating a relationship between a signal reception level and a noise level.

FIG. 4 is a diagram illustrating calculation of a C / N level.

FIG. 5 is a diagram illustrating a relationship between a signal reception level and a noise level.

FIG. 6 is a diagram illustrating display on a tube surface.

FIG. 7 is an explanatory diagram used to explain a conventional example.

FIG. 8 is an explanatory diagram used to explain a conventional example.

[Explanation of symbols]

 Reference Signs List 1 antenna 3 tuner 4 video signal processing circuit 5 adder 6 signal level judgment circuit 7 noise level judgment circuit 8 comparator 9 level calculation circuit 10 character generator 12 CRT display 15 CPU CNi C / N level LBi reception level SNOi absolute value LNOi noise Level LNa3 noise level

Claims (1)

(57) [Claims] 1. The level of a signal received by an antenna;
Means for comparing the noise level with the noise level, based on the result of the comparison, when the signal level is lower than the noise level, a level for the carrier noise is displayed; Means for subtracting a predetermined value from the signal level when the level is higher than the signal level and displaying the result.