JPH06130106A - Cn ratio measuring device for receiving antenna - Google Patents

Abstract

PURPOSE:To provide the title device easily and accurately measuring the CN ratio of the receiving signal of an arbitrary channel by simple constitution. CONSTITUTION:In a device measuring the signal level of the predetermined channel in a receiving signal by mixing the receiving signal from a receiving antenna and the oscillation signal from a variable oscillation circuit 18 to convert them to an intermediate frequency signal and detecting the intermediate frequency signal to detect the detection voltage thereof, a control circuit 40 measures the absolute levels P(fD), P(fU) of the frequency components in frequencies (lower side; fD, upper side; fU) separated up and down from the channel group alotted to a satellite. When the frequency of a selected channel is nearer to fU than fD, p(fU) is set to the noise level of the frequency of the channel and, in the reverse case, P(fD) is set to the noise level of the frequency of the channel to operate the CN ratio of the selected channel.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is a CN for a receiving antenna for measuring the CN ratio (carrier signal to noise ratio) of the receiving signal of an arbitrary channel among the receiving signals inputted from the receiving antenna.
The present invention relates to a ratio measuring device.

[0002]

2. Description of the Related Art Conventionally, when measuring a CN ratio of a received signal output from a receiving antenna, a signal level measuring device is used to first receive the signal input from a receiving antenna set in a predetermined direction. The absolute level (signal level) of the received signal in the desired channel is measured from the signals, and then the direction of this receiving antenna is adjusted to find the direction in which the absolute level of the input signal from the receiving antenna is the lowest. By searching for the ratio of this minimum level to the above-mentioned signal level, the CN of the received signal on the desired channel can be obtained.
I was looking for a ratio.

That is, the noise level of the converter of the receiving antenna is measured by changing the direction of the receiving antenna, and the CN ratio is obtained by assuming this as the noise level in the received signal.

[0004]

However, when the CN ratio is obtained using the signal level measuring device as described above, the direction of the receiving antenna is always adjusted to minimize the absolute level of the input signal. In order to measure the CN ratio, it is necessary to measure the noise level that is the basis for calculating the CN ratio, and this work cannot be performed unless the channel for which the CN ratio is measured is changed. In the end, there is a problem that it takes a lot of time and trouble to measure the CN ratio.

The present invention has been made in view of the above problems, and provides a CN ratio measuring device for a receiving antenna, which has a simple structure and can easily and accurately measure the CN ratio of a received signal of an arbitrary channel. The purpose is to provide.

[0006]

That is, the present invention as set forth in claim 1 made in order to solve the above problems,
As illustrated in (A), a CN ratio measuring device for a reception antenna, which measures a CN ratio of a reception signal of an arbitrary channel among reception signals input from the reception antenna, is provided. From the channel selection means for selecting a received signal of a predetermined channel from the inside, signal level detection means for detecting the absolute level of the selected received signal, and the highest frequency of the channel group to which the selected received signal belongs First noise level detecting means for detecting an absolute level of a frequency component higher by a predetermined frequency, second noise level detecting means for detecting an absolute level of a frequency component lower by a predetermined frequency than the lowest frequency of the channel group, and Compares the judgment frequency preset between the highest frequency and the lowest frequency of the channel group with the frequency of the received signal selected above. On the basis of the comparison means and the result of the comparison performed by the comparison means, when the frequency of the selected reception signal is higher than the determination frequency, the absolute level detected by the first noise level detection means and the signal The CN ratio of the selected received signal is calculated from the absolute level of the received signal detected by the level detection means, and conversely, when the frequency of the selected received signal is smaller than the determination frequency, CN ratio calculation means for calculating the CN ratio of the selected reception signal from the absolute level detected by the second noise level detection means and the absolute level of the reception signal detected by the signal level detection means. The gist is a CN ratio measuring device for a receiving antenna.

Further, the present invention according to claim 2 is based on FIG.
As illustrated in (B), a CN ratio measuring device for a reception antenna, which measures a CN ratio of a reception signal of an arbitrary channel among reception signals input from the reception antenna, is provided. From the channel selection means for selecting a received signal of a predetermined channel from the inside, signal level detection means for detecting the absolute level of the selected received signal, and the highest frequency of the channel group to which the selected received signal belongs A first noise level detecting means for detecting an absolute level of a frequency component higher by a predetermined frequency, and a second noise level detecting means for detecting an absolute level of a frequency component lower by a predetermined frequency than the lowest frequency of the channel group; Second
Noise level calculating means for calculating the absolute level of noise at the frequency of the selected received signal by proportional calculation from the absolute level detected by the noise level detecting means and the absolute level detected by the first noise level detecting means. And a CN ratio calculation means for calculating a CN ratio of the selected reception signal from the absolute level of noise calculated by the noise level calculation means and the absolute level of the reception signal detected by the signal level detection means. The gist is a CN ratio measuring device for a receiving antenna, which is characterized by being provided.

[0008]

In the CN ratio measuring device for a receiving antenna according to claim 1 configured as described above, the tuning means selects a reception signal of a predetermined channel from the reception signals input from the reception antenna. Then, the signal level detecting means detects the absolute level of the selected reception signal. And
The first noise level detecting means detects the absolute level of a frequency component higher by a predetermined frequency than the highest frequency of the channel group to which the selected received signal belongs, and the second noise level detecting means also detects this channel group. The absolute level of the frequency component lower by a predetermined frequency than the lowest frequency is detected.

Then, the comparison means compares the judgment frequency preset between the highest frequency and the lowest frequency of the channel group with the frequency of the selected reception signal, and the CN ratio calculation means When the frequency of the selected received signal is higher than the determination frequency based on the result of the comparison performed by the comparison means, the absolute level detected by the first noise level detection means and the signal level detection means The CN ratio of the selected received signal is calculated from the absolute level of the received signal detected by, and conversely, when the frequency of the selected received signal is smaller than the determination frequency, the second The CN ratio of the selected reception signal is calculated from the absolute level detected by the noise level detection means and the absolute level of the reception signal detected by the signal level detection means.

That is, in the CN ratio measuring apparatus for a receiving antenna according to the first aspect, the absolute level detected by the first noise level detecting means or the second noise level detecting means is determined in the received signal selected. In order to obtain the CN ratio as the noise level, it is not necessary to adjust the direction of the receiving antenna and search for the direction in which the absolute level of the input signal is the lowest, as in the conventional CN ratio measuring device described above. The CN ratio of the receiving antenna can be measured.

Further, as the noise level of the received signal, when the frequency of the selected received signal is higher than the judgment frequency, the absolute level detected by the first noise level detecting means is used, and conversely, When the frequency of the received signal received is smaller than the decision frequency, the absolute level detected by the second noise level detecting means is used, so that the CN ratio of the receiving antenna can be accurately measured. .

Here, the noise level in the received signal input from the receiving antenna is affected to a large extent by the in-band deviation caused by the receiving antenna itself and the frequency characteristic of the cable, and therefore depends on the frequency of the receiving signal to be selected. It will be slightly different. Therefore, in order to measure the CN ratio of the selected received signal more accurately, in the CN ratio measuring device for a receiving antenna according to claim 2, the tuning unit is arranged so that the received signal input from the receiving antenna is The reception signal of a predetermined channel is selected from the inside, and the signal level detecting means detects the absolute level of the selected reception signal. Then, the first noise level detection means detects the absolute level of the frequency component higher by a predetermined frequency than the highest frequency of the channel group to which the selected received signal belongs, and the second noise level detection means also detects this absolute level. The absolute level of the frequency component lower than the lowest frequency of the channel group by a predetermined frequency is detected.

Then, the noise level calculating means calculates the absolute level detected by the first noise level detecting means and the second level.
From the absolute level detected by the noise level detection means of,
The absolute level of noise at the frequency of the selected received signal is calculated by proportional calculation, and the CN ratio calculation means calculates the absolute level of noise calculated by the noise level calculation means and the received signal detected by the signal level detection means. The CN ratio of the selected reception signal is calculated by comparing with the absolute level.

That is, C for the receiving antenna according to claim 2
In the N ratio measuring device, the noise level at the frequency of the selected reception signal is calculated by proportional calculation from the absolute level detected by the first noise level detecting means and the absolute level detected by the second noise level detecting means. Since it is set in this way, it is possible to minimize the effects of in-band deviation due to the receiving antenna itself and the frequency characteristics of the cable,
The CN ratio can be measured more accurately.

[0015]

Embodiments to which the present invention is applied will be described below with reference to the drawings. First, FIG. 2 shows a satellite signal reception parabolic antenna that receives radio waves transmitted from artificial satellites (broadcast satellites, communication satellites), converts them into reception signals of a predetermined frequency (1 GHz band in this embodiment), and outputs the signals. Schematic showing the overall configuration of a signal level measuring device 10 for inputting a received signal from a (reception antenna), selecting a received signal of an arbitrary channel from this received signal, and measuring the absolute level, CN ratio, etc. of the received signal. It is a block diagram.

As shown in the figure, the signal level measuring apparatus 10 of this embodiment has an RF amplifier circuit 14 for amplifying a received signal (950 to 1880 MHz) from a receiving antenna input from an input terminal 12, and this amplified signal. Variable attenuator 16 for attenuating the received signal level, and 1352.78-228
From a known variable oscillation circuit 18 including a local oscillator 18a, a PLL circuit 18b, and a frequency divider 18c capable of changing the oscillation frequency between 2.78 MHz, an output signal from the variable oscillation circuit 18, and a variable attenuator 16. The received signal of a specific channel in the received signal is mixed with the received signal of
Only the mixer 20 that converts the signal into the Hz band (intermediate frequency 402.78 MHz) and the received signal (intermediate frequency 402.78 MHz, bandwidth ± 5 MHz) of the 400 MHz band from the output signal from the mixer 20 are passed. Band-pass filter (hereinafter simply referred to as BPF)
21, an IF amplifier circuit 22 that amplifies the output signal from the BPF 21, a variable attenuator 24 that attenuates the amplified received signal level, a detection circuit 28 that detects the output signal from the variable attenuator 24, and a detection circuit An A / D converter (hereinafter, simply referred to as an ADC) 30 for converting the detection voltage output from the circuit 28 into a digital signal, a power switch, a predetermined satellite of a reception signal to be measured such as a level and a CN ratio, and a channel thereof. An operation unit 32 provided with a setting switch for setting and a mode changeover switch for switching each measurement mode, an input circuit 34 for converting an instruction from the operation unit 32 into an electric signal, a liquid crystal panel, etc. A well-known microcomputer including a display unit 36 including a display circuit 38 for driving the display unit 36, a CPU, a ROM, a RAM, and the like. It is composed of an input circuit 34
Based on the instruction input from the
A control circuit 40 that performs N ratio measurement control and the like and displays the measurement result on the display unit 36.

In the signal level measuring apparatus 10 of the present embodiment configured as described above, the control circuit 40 executes a tuning routine (not shown), so that the frequency of the received signal of the designated channel (hereinafter, simply A pulse signal corresponding to the channel frequency) is output to the PLL circuit 18b to adjust the oscillation frequency of the variable oscillation circuit 18,
The channel selection is performed so that the reception signal corresponding to this designated channel is output from 21.

The output signal output from the BPF 21 is amplified by the IF amplification circuit 22, and then detected by the detection circuit 2.
The detected voltage is converted into a digital signal by the ADC 30 and input to the control circuit 40.
Then, the control circuit 40 measures the absolute level of the received signal by executing a level measurement routine (not shown).

When the control circuit 40 executes the level measurement routine, if the level of the input signal exceeds the measurement range in the control circuit 40, first,
The attenuation amount of the variable attenuator 24 is increased, and when the attenuation amount is still insufficient, the attenuation amount of the variable attenuator 16 is adjusted to be increased. Conversely, when the signal level is less than the measurement range, first, Decrease the amount of attenuation of the variable attenuator 16,
If the amount of attenuation is still large, the amount of attenuation of the variable attenuator 24 is reduced so that each of the variable attenuators 16 and 24 is controlled so that optimum level measurement is always possible.

Further, in the ROM in the control circuit 40, a plurality of artificial satellite names {in this embodiment, broadcasting satellite BS, communication satellite JCSAT of Japan Communication Satellite Co., Ltd., and Space Communication Co., Ltd.
Communication satellite super bird}, and channel frequency of all channels transmitted from these artificial satellites, and information necessary for measuring the level, CN ratio, etc. are stored in advance.

Then, the signal level measuring apparatus 1 of this embodiment
0 indicates the input terminal 12 and the receiving antenna 4 as shown in FIG.
It is used by connecting the output terminal 42 of No. 1 with the coaxial cable 44. Hereinafter, the signal level measuring device 1
The CN ratio measurement control processing as the first embodiment, which is executed by the control circuit 40 within 0, will be described with reference to FIGS. 4 and 5. The CN ratio measurement control process is started by turning on the power switch of the operation unit 32 while the CN ratio measurement mode is set by the mode changeover switch of the operation unit 32.

As shown in FIG. 4, when the CN ratio measurement control process is started, first, at step 110, the operation unit 32 is started.
The satellite name for which the CN ratio measurement is set is read from the input circuit 34, and the channel frequencies of all channels assigned to this satellite name are read from the ROM.

Hereinafter, the case where the broadcasting satellite BS is set at this time will be described as an example with reference to FIG. still,
As shown in FIG. 5, the channels assigned to the broadcasting satellite BS are a total of 8 channels from 1 channel to 15 channels. After such satellite name reading processing is performed, in step 120, the channel frequency fch1 of channel 1 and the channel frequency fch of channel 3 assigned to the broadcasting satellite BS.
3 (XMHz: 38.36 MHz), a frequency lower than the channel frequency fch1 of one channel by X MHz (hereinafter referred to as lower virtual channel frequency fD) is calculated, and the frequency component of the lower virtual channel frequency fD is calculated. A process as a second noise level detecting unit that measures an absolute level (hereinafter, referred to as a lower virtual noise level P (fD)) is executed.

The lower virtual noise level P (fD)
For the measurement of the lower virtual channel frequency fD, the lower virtual channel frequency fD is set from the BPF 21 by setting the channel selection frequency to the lower virtual channel frequency fD as in the case of selecting the normal channel.
Is performed by measuring the absolute level of the frequency component obtained from the digital signal output from the ADC 30.

Thus, the lower virtual noise level P (f
After measuring D), in the following step 130, the channel frequency of 15 channels is calculated from the difference (YMHz: 38.36 MHz) between the channel frequency fch15 of 15 channels and the channel frequency fch13 of 13 channels assigned to the broadcasting satellite BS. A frequency higher than fch15 by Y MHz (hereinafter referred to as upper virtual channel frequency fU) is calculated, and similarly to step 120,
The absolute level of the frequency component at the upper virtual channel frequency fU (hereinafter, upper virtual noise level P (fU)
That is, the processing as the first noise level detecting means for measuring

In this embodiment, fD = 101
It is 1.12 MHz and fU = 1356.36 MHz.
Then, in the following step 140, the channel number of the received signal which is the target of the CN ratio measurement set by the operation unit 32 is read from the input circuit 34, the channel frequency fch corresponding to this channel number is selected, and the following step 150 , The absolute level of the received signal at the selected channel frequency fch (hereinafter, signal level P (f
ch)) is executed as a signal level detecting means.

In the next step 160, a frequency preset between the channel frequency fch1 of channel 1 and the channel frequency fch15 of channel 15 (hereinafter, referred to as a decision frequency fI) and the selected channel frequency fch are set. When the channel frequency fch is higher than the determination frequency fI (for example, when channel 11 is selected), the process proceeds to step 170 as it is, and at step 170, The CN ratio of the reception signal at the selected channel frequency fch is calculated by subtracting the upper virtual noise level P (fU) from the signal level P (fch).

Then, in step 190, the calculated CN ratio is displayed on the display unit 36 via the display circuit 38. On the other hand, in step 160, the channel frequency fc
When h is smaller than the determination frequency fI (for example, when channel 5 is selected), the process proceeds to step 180, and at step 180, the signal level P (fch) is changed to the lower virtual noise level P (fD). Is calculated to calculate the CN ratio of the received signal at the selected channel frequency fch. Then, the process proceeds to step 190,
In step 190, the calculated CN ratio is displayed on the display unit 36.

In this way, when the CN ratio is displayed in step 190, it is determined in step 200 whether or not an end instruction has been given from the operation unit 32, and the end instruction has been given. If it is, the CN ratio measurement process is ended as it is, and conversely, if the end instruction is not given,
Returning to step 140, the CN ratio of the received signal of the next channel to be selected is measured.

As described above, in the signal level measuring apparatus 10 of the present embodiment, steps 170 and 180 serve as CN ratio calculating means, and when the selected channel frequency fch is higher than the judgment frequency fI, the upper side. The virtual noise level P (fU) is set to the channel frequency fch.
On the contrary, when the selected channel frequency fch is smaller than the determination frequency fI, the lower virtual noise level P (fD) is regarded as the noise level of the channel frequency fch, and the CN ratio is Calculate Therefore, according to the signal level measuring device 10 of the present embodiment, it becomes possible to measure the CN ratio of the receiving antenna very easily and accurately.

By the way, the noise level in the received signal input from the receiving antenna 41 is affected to some extent by the in-band deviation caused by the receiving antenna 41 itself and the frequency characteristic of the coaxial cable 44, and therefore the channel frequency to be selected. Will vary slightly depending on

Then, the signal level measuring apparatus of the second embodiment, which can more accurately measure the CN ratio of the received signal at the selected channel frequency, will be described below. The signal level measuring device of this embodiment has exactly the same configuration as the signal level measuring device 10 described above. And
Since only the CN ratio measurement control process executed by the control circuit 40 is different, only this CN ratio measurement control process will be described below with reference to FIG.

The CN ratio measurement control process in this embodiment is also started at the same time when the power is turned on by the power switch of the operation unit 32, and the processes of steps 210 to 250 are performed in steps 110 to 150 of the first embodiment.
It is exactly the same as the processing up to.

Therefore, the processing after step 260 will be described here. In step 260, from the upper virtual noise level P (fU) and the lower virtual noise level P (fD) measured in step 220 and step 230, the channel frequency fch selected by proportional calculation is calculated as follows. The noise level P (f) is calculated.

[0035]

[Equation 1]

Then, in the following step 270, the noise level P (f) calculated in step 260 is subtracted from the signal level P (fch) measured in step 250 to calculate the CN ratio, and then to step 280. Then, the calculated CN ratio is displayed on the display unit 36.

In this way, when the CN ratio is displayed in step 280, it is determined in step 290 whether or not an end instruction has been given from the operation unit 32, and the end instruction has been given. If it is, the CN ratio measurement process is ended as it is, and conversely, if the end instruction is not given,
Returning to step 240, the CN ratio measurement of the reception signal of the next set channel is performed.

As described above, in the signal level measuring apparatus 10 of the present embodiment, step 260 serves as the noise level calculating means and the selected channel frequency fc.
The noise level P (f) at h is calculated by proportional calculation, and at step 270, the CN ratio of the received signal at the selected channel frequency fch is calculated by the CN ratio calculation means.

Therefore, the signal level measuring apparatus 1 of this embodiment
According to 0, the CN ratio of the receiving antenna can be measured very easily, and the influence of the in-band deviation caused by the receiving antenna 41 itself and the frequency characteristic of the coaxial cable 44 can be minimized. It becomes possible to obtain more accurate measurement results.

[0040]

As described above, in the CN ratio measuring apparatus for a receiving antenna according to the first aspect, when the frequency of the selected reception signal is higher than the preset judgment frequency, the reception signal is received. The noise level is the absolute level of the frequency component that is higher than the highest frequency of the channel group to which the signal belongs by a predetermined frequency, and conversely, if the frequency of the selected received signal is lower than the above-mentioned judgment frequency, The CN level of the selected received signal is measured with the absolute level of the frequency component lower by a predetermined frequency as the noise level.

Therefore, according to the CN ratio measuring apparatus for the receiving antenna of the first aspect, the direction of the receiving antenna is measured in order to measure the noise level of the selected received signal like the conventional CN ratio measuring apparatus. There is no need to adjust
It is possible to easily and accurately measure the CN ratio of the reception signal of an arbitrary channel input from the reception antenna.

Further, the receiving antenna C according to claim 2
In the N-ratio measuring device, the noise level at the frequency of the selected reception signal is compared with the absolute level of the frequency component higher by a predetermined frequency than the highest frequency of the channel group,
The absolute level of the frequency component lower than the lowest frequency of the channel group by a predetermined frequency is used to perform a proportional calculation, and this value is used to measure the CN ratio of the selected reception signal.

Therefore, according to the CN ratio measuring apparatus for the receiving antenna of the second aspect, the received signal selected by the receiving antenna can be minimized while minimizing the influence of the in-band deviation caused by the receiving antenna itself and the frequency characteristic of the cable. The noise level of the receiving antenna C according to claim 1 can be calculated.
Similar to the N-ratio measuring device, the CN ratio of the received signal of the arbitrary channel can be easily measured, and more accurate measurement result can be obtained.

[Brief description of drawings]

FIG. 1 is a block diagram illustrating a configuration of the present invention.

FIG. 2 is a schematic configuration diagram showing an overall configuration of a signal level measuring device 10 according to an embodiment.

FIG. 3 is an explanatory diagram illustrating a usage state of the signal level measuring device 10 according to the embodiment.

FIG. 4 is a flowchart showing a CN ratio measurement control process as a first embodiment, which is executed by a control circuit 40 in the signal level measuring device 10.

FIG. 5 is an explanatory diagram illustrating a channel group assigned to a broadcasting satellite BS.

FIG. 6 is a flowchart showing a CN ratio measurement control process as a second embodiment, which is executed by the control circuit 40 in the signal level measuring device 10.

[Explanation of symbols]

10 ... CN ratio measuring device 12 ... Input terminal 14
... RF amplification circuit 16, 24 ... Variable attenuator 18 ... Variable oscillation circuit 18
a ... local oscillator 18b ... PLL circuit 18c ... frequency divider 20
… Mixer 21… Band pass filter 22… IF amplification circuit 28
Detecting circuit 32 Operating unit 34 Input circuit 36
Display unit 38 Display circuit 40 Control circuit

Claims (2)

[Claims] 1. A CN ratio measuring device for a reception antenna, which measures a CN ratio of a reception signal of an arbitrary channel among reception signals input from the reception antenna, wherein a CN ratio measuring device for a reception signal input from the reception antenna is predetermined. Channel selection means for selecting the received signal of the channel, signal level detection means for detecting the absolute level of the selected received signal, and a predetermined frequency from the highest frequency of the channel group to which the selected received signal belongs A first noise level detecting means for detecting an absolute level of a high frequency component; a second noise level detecting means for detecting an absolute level of a frequency component lower by a predetermined frequency than the lowest frequency of the channel group; A comparison hand that compares the judgment frequency preset between the highest frequency and the lowest frequency with the frequency of the received signal selected above. And based on the result of the comparison performed by the comparison means, when the frequency of the selected received signal is higher than the determination frequency, the absolute level detected by the first noise level detection means and the signal level detection The CN ratio of the selected received signal is calculated from the absolute level of the received signal detected by the means, and conversely, when the frequency of the selected received signal is smaller than the determination frequency, the second And a CN ratio calculating means for calculating the CN ratio of the selected received signal from the absolute level detected by the noise level detecting means and the absolute level of the received signal detected by the signal level detecting means. Characteristic CN ratio measuring device for receiving antenna. 2. A CN ratio measuring device for a reception antenna, which measures a CN ratio of a reception signal of an arbitrary channel among reception signals input from the reception antenna, wherein the CN ratio measuring device is a predetermined one among the reception signals input from the reception antenna. Channel selection means for selecting the received signal of the channel, signal level detection means for detecting the absolute level of the selected received signal, and a predetermined frequency from the highest frequency of the channel group to which the selected received signal belongs A first noise level detecting means for detecting an absolute level of a high frequency component; a second noise level detecting means for detecting an absolute level of a frequency component lower by a predetermined frequency than the lowest frequency of the channel group; The received signal selected according to the absolute level detected by the noise level detecting means and the absolute level detected by the first noise level detecting means. Noise level calculation means for calculating the absolute level of noise at a frequency by proportional calculation, and the channel selected from the absolute level of noise calculated by the noise level calculation means and the absolute level of the received signal detected by the signal level detection means. A CN ratio measuring device for a receiving antenna, comprising: a CN ratio calculating means for calculating a CN ratio of the received signal.