JPH077930B2 - Signal level measuring device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention selects a signal of a predetermined channel from an input signal including a large number of signals such as a received signal output from a receiving antenna and measures an absolute level of the signal. The present invention relates to a signal level measuring device.

[0002]

2. Description of the Related Art Conventionally, a device of this type has been used, for example, from a TV antenna, a broadcasting satellite (BS) or a communication satellite (CS) which receives a VHF or UHF band television broadcasting radio wave transmitted from a ground station. It is used to measure the absolute level of the received signal output from various receiving antennas such as satellite antennas that receive the transmitted radio waves for each channel signal, and adjust the direction of the receiving antenna and check the level of the receiving system. Has been done.

Further, this type of device is constructed so that it can output not only the absolute level of the received signal but also a reference signal of a specific frequency modulated by a predetermined video signal, and this reference signal is received. There is also an apparatus in which the level of the receiving system can be easily checked from the displayed image by demodulating the reference signal and displaying the image on a television receiver or the like connected to the terminal side.

[0004]

However, in the conventional signal level measuring apparatus capable of outputting the reference signal as described above, the level for measuring the absolute level of the signal of the predetermined channel selected from the input signals. Since the measurement system and the signal output system for generating the reference signal and outputting it to the outside are independently configured, there is a problem that the device configuration becomes complicated.

Further, as described above, in order to accurately check the level of the receiving system using the reference signal, it is necessary to make the frequency of the reference signal correspond to a signal that can be transmitted by the receiving system. That is, for example, if the receiving system is a system that transmits the BS signal output from the receiving antenna, a reference signal near the maximum frequency of the BS signal is required, and the receiving system outputs the CS signal from the receiving antenna.
In the case of a system that transmits a signal, a reference signal near the maximum frequency of the CS signal is required. However, since the conventional signal level measuring device is designed to generate only one type of reference signal, there is a problem that it is not possible to perform an optimum level check corresponding to the type of receiving system and its transmission frequency. It was

The present invention has been made in view of the above problems, and in the signal level measuring device capable of outputting the reference signal as described above, the structure thereof is simplified and the frequency of the reference signal can be changed. The purpose is to

[0007]

SUMMARY OF THE INVENTION The present invention, which has been made to achieve the above object, provides an oscillator whose oscillation frequency can be controlled by a control voltage, an oscillation signal from the oscillator, and an external signal, as shown in FIG. A frequency conversion means for mixing a signal of a predetermined channel included in the input signal into a predetermined measurement frequency and a signal converted into the measurement frequency by the frequency conversion means from the outside. Tuning control means for controlling the oscillation frequency of the oscillator by adjusting the control voltage so as to obtain a signal of a selected channel, and measurement for measuring the absolute level of the signal converted to the measurement frequency by the frequency conversion means. And a signal level measuring device having means for outputting a reference signal to the outside from the measuring mode for measuring the signal level. When the operation mode of the device is switched from the measurement mode to the output mode by the operation mode switching means for switching to the mode, the output of the oscillator is connected to the external output terminal instead of the frequency conversion means. Then, when the oscillation signal from the oscillator is output from the external output terminal as the reference signal and the operation mode switching unit also switches the operation mode of the device from the measurement mode to the output mode. In place of the tuning control means, output frequency control means for applying a control voltage to the oscillator to control the oscillation frequency of the oscillator to an output frequency designated from the outside, and the output frequency control means includes the oscillator. And a video signal superimposing means for superimposing a predetermined video signal on the control voltage applied to It is a symptom.

[0008]

In the signal level measuring device of the present invention constructed as described above, the tuning control means controls the oscillation frequency of the oscillator when the operation mode is the measurement mode for measuring the signal level. Then, using the output of the oscillator, the frequency conversion means converts the signal of the externally designated channel of the input signal into the measurement frequency. Then, the signal converted into the measurement frequency by the frequency converting means is input to the measuring means, and the measuring means measures the absolute level of the signal.

On the other hand, when the operation mode switching unit switches the operation mode from the measurement mode to the output mode for outputting the reference signal to the outside, the oscillation output switching unit replaces the output of the oscillator with the frequency conversion unit and outputs the external output terminal. By connecting to the output signal from the external output terminal as a reference signal from the oscillator, the output frequency control means, in place of the tuning control means, the oscillation frequency of the oscillator to the output frequency specified from the outside. A control voltage for controlling is applied to the oscillator, and the video signal superimposing means superimposes the video signal on the control voltage applied to the oscillator by the output frequency controlling means.

That is, in the signal level measuring device of the present invention, when the operation mode is the measurement mode, a desired channel is designated from the outside, and the signal of the designated desired channel is automatically selected from the input signals. And the absolute level of that signal is measured. Also, if the operation mode is the output mode, by specifying the frequency that you want to output as the reference signal externally, the reference signal of the specified frequency is output from the oscillator used for channel selection when measuring the signal level. It is output to the outside through the terminal. When the oscillator generates the reference signal, the video signal is superimposed on the control voltage for controlling the oscillation frequency of the oscillator. Therefore, the reference signal is a signal in which the carrier wave of the specified frequency is FM-modulated by the video signal, If this signal is demodulated, it can be displayed as an image on a television receiver or the like.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. First, FIG. 2 is a schematic configuration diagram of a signal level measuring apparatus of an embodiment to which the present invention is applied. In addition, the signal level measuring apparatus of the present embodiment is a broadcasting satellite (BS) or a communication satellite (C
S) to receive the transmitted radio wave, and the predetermined frequency band (1GHz
This is a level measuring device for satellite signals, which measures the output level of a received signal from a satellite dish receiving parabolic antenna (receiving antenna), which is converted into a received signal (BS signal, CS signal) of a band) and output.

As shown in FIG. 2, 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 the receiving antenna input to the input terminal 12, and an external input. The oscillator 16 whose oscillation frequency can be changed between 1352.78 and 2282.78 MHz by the control voltage to be generated, and the oscillation signal output from the oscillator 16 are input via the changeover switch SW1 and the amplifier A1. And the reception signal output from the RF amplifier circuit 14 are mixed, and the signal of the specific channel in the reception signal is in the 400 MHz band (center frequency 402.
(78 MHz) intermediate frequency signal mixer 18 as a frequency conversion means, IF amplifier circuit 20 for amplifying the output signal from the mixer 18, IF amplifier circuit 20 from among the signals amplified by the mixer 18 Only the reception signal of the specific channel converted into the intermediate frequency signal is passed, the center frequency is 402.78 MHz, and the bandwidth is ± 5, for example.
A so-called tuning circuit including a bandpass filter (hereinafter, simply referred to as BPF) 22 of MHz is provided.

In addition to such a tuning circuit, the signal level measuring device 10 includes a detection circuit 24 for detecting a reception signal of a specific channel that has passed through the BPF 22, and a detection voltage VD output from the detection circuit 24 as a digital signal. A / D converter 26 for converting into a frequency, a frequency divider 28 for controlling the oscillation frequency of the oscillator 16 to a designated predetermined frequency, and a PL
When an oscillation signal from the L circuit 30 and the oscillator 16 is input through the changeover switch SW1, an amplifier A2 that amplifies the oscillation signal and outputs it as a reference signal to the outside, an external output terminal 32, and a reference from the external output terminal 32 When the signal is output to the outside, the video signal generating circuit 34 that superimposes the video signal for the crosshatch display on the control voltage for controlling the oscillation frequency that the PLL circuit 30 applies to the oscillator 16, the measurement result of the signal level, and the related signal. A display unit 36 for displaying the operating state of the apparatus, an operating unit 38 for the user to set an operating mode, specify a received signal to be level-measured, set a frequency of a reference signal, etc. From the input circuit 38a, and drive control of the changeover switch SW1, the PLL circuit 30, the video signal generating circuit 34, etc. according to the content of the instruction. Rutotomoni, the control circuit 40 to be displayed on the display unit 36 via the display circuit 36a the measurement results of the operating state or signal level, etc. are provided.

Next, the control circuit 40 uses the CPUs 40a, R
It is configured by a well-known microcomputer including an OM 40b, a RAM 40c and the like. And the control circuit 4
When the operation mode of the device is set to the measurement mode for measuring the level (absolute level) of the received signal by the operation of the operation unit 38, first, the switch 0
W1 is switched to the side for inputting the oscillation signal of the oscillator 16 to the mixer 18 (the side shown in FIG. 2), and then the type of satellite and the channel selected by the user via the operation unit 38 are read, A frequency for converting the received signal of the selected channel by the mixer 18 into the intermediate frequency signal by the mixer 18 by outputting the PLL data corresponding to the read type of satellite and the selected channel to the PLL circuit 30. Then, the tuning process as the tuning control means is executed by the procedure of oscillating.

As a result of this tuning process, the center frequency f of the reception signal of the above-mentioned designated channel selected from the oscillator 16 is generated.
The center frequency fo of the intermediate frequency signal fo (= 402.78M
Hz) is added to output a signal of frequency fx (= fIN + fo), the mixer 18 converts the received signal of the selected channel into an intermediate frequency signal, and the A / D converter 26
The detection voltage VD of the received signal is converted into digital data.

For this reason, when the control circuit 40 executes the channel selection processing in the above-described procedure, this time, the digital data is read from the A / D converter 26, and the signal level (absolute absolute) of the channel selected from the read digital data. The signal level measuring process as the measuring means is executed by a procedure of calculating (level), and then the signal level displaying process of displaying the calculation result on the display unit 36 is executed.

Therefore, in the signal level measuring apparatus of the present embodiment, the output terminal of the receiving antenna is connected to the input terminal 12, the operating section 38 is operated to set the measurement mode as the operation mode, and the receiving antenna transmits. When the type of satellite that receives radio waves and the channel whose level you want to measure are specified, the received signal of the specified channel is automatically selected and the absolute level of that signal is measured.
6 will be displayed.

On the other hand, the user operates the operation unit 38 functioning as the operation mode switching means to switch the operation mode to the output mode in which the reference signal is output from the external output terminal 32, and the frequency of the reference signal is designated. Then, the control circuit 40 executes the reference signal output process shown in FIG.

That is, as shown in FIG. 3, in this reference signal output process, first, at step 110, the frequency of the reference signal designated by the user is read, and at step 120, the read frequency is corresponded to. P
By outputting the LL data to the PLL circuit 30, processing as output frequency control means for causing the oscillator 16 to oscillate at a specified frequency is executed.

Then, in the following step 130, a process as an oscillation output switching means for switching the changeover switch SW1 to the side for inputting the oscillation signal of the oscillator 16 to the external output terminal 32 (the side opposite to that in FIG. 2) is executed, Continued Step 14
By driving the video signal generation circuit 34 at 0,
The PLL circuit 30 performs a process as a video signal superimposing unit that superimposes the video signal on the control voltage applied to the oscillator 16, and then ends the process once.

In this embodiment, as the frequency of the reference signal, the maximum frequency of the BS signal frequency band (1318 MHz) and the maximum frequency of the broadcasting frequency band used for CATV of the CS signal (1758) are preset. .25 MH
z), and three kinds of frequencies of the maximum frequency (1860 MHz) of the frequency band for special communication in the CS signal are set, and when the user specifies the frequency of the reference signal, these are set. A desired frequency is selected from the three frequencies.

As described above, in the signal level measuring apparatus of this embodiment, when the operation mode is switched from the measurement mode to the output mode and the frequency of the reference signal is selected and designated, the reference signal of the designated frequency is selected. It is output to the outside from the oscillator 16 forming the circuit via the external output terminal 32. When the oscillator 16 generates the reference signal, the video signal for the crosshatch display is superimposed on the control voltage of the oscillator 16 by the operation of the video signal generation circuit 34. Therefore, the reference signal is the carrier wave of the specified frequency. Is FM-modulated by the video signal.

Therefore, as shown in FIG. 4, for example, a satellite signal mixer 52 for mixing BS signals and CS signals, BS signals and CS signals output from the satellite signal mixer 52, a VHF antenna 54, and a UHF antenna 56 are provided. The amplifier device (so-called booster) 58 which amplifies and outputs the received terrestrial broadcast signal (VU signal) respectively, the distributor 60 which distributes the output signal from the amplifier device 58, and the distributor 60. In a receiving system including a branching device 62 for relaying or terminating, which supplies each distributed signal to each terminal, a BS is installed before a receiving antenna for receiving satellite signals is installed.
Alternatively, the signal level measuring device 1 is connected to the signal line for inputting the CS signal.
Input the reference signal from 0, and on the terminal side of the system, CS
If the BS tuner 64 demodulates the reference signal and inputs it to the television receiver 66, a crosshatch image can be displayed on the television receiver 66. From this display image, the receiving system can receive the receiving antenna from the receiving antenna. It is possible to check whether or not the output received signal is transmitted.

Further, for example, when there is another signal level measuring device 10 of this embodiment, the signal level measuring device 10 is connected to the terminal side of the system as shown by the dotted line in FIG. If the level is measured, the level of the receiving system can be accurately checked.

Furthermore, in the signal level measuring apparatus 10 of the present embodiment, the frequency of the reference signal is the maximum frequency of the frequency band of the BS signal, the maximum frequency of the frequency band for broadcasting used for CATV in the CS signal, And a maximum frequency including a frequency band for special communication of CS signals, the receiving system shown in FIG.
If the system also covers the frequency band for special communication of CS signals, when inputting the reference signal to the signal line for BS signal input, set that frequency to the maximum frequency of the frequency band of BS signals, When the reference signal is input to the signal line for inputting the CS signal, by setting the frequency to the maximum frequency including the frequency band for special communication of the CS signal, the receiving system is checked for each signal. be able to.

As described above, in the signal level measuring apparatus of this embodiment, not only the reference signal can be generated but also its frequency can be changed. , The oscillator 16 used for tuning at the time of level measurement is also used.
By superimposing the video signal on the reference voltage of 1, the FM-modulated reference signal is generated by the video signal, so that the device configuration can be simplified and the cost can be reduced as compared with the conventional device. become.

Here, in the signal level measuring apparatus of the above embodiment, the frequency of the reference signal can be switched in three steps, but the frequency of the reference signal can be easily adjusted by adjusting the control voltage applied to the oscillator 16. Therefore, the frequency of the reference signal can be set to an arbitrary frequency.

In the above embodiment, the signal level of the BS and CS signals is measured. However, the present invention is a signal level measuring device for measuring the level of VHF and UHF band television signals (VU signals). It goes without saying that the present invention can also be applied to a measuring device that measures a signal level in another frequency band.

In this case, the VU signal generated by the signal level measuring device is an FM-modulated signal. However, if an FM demodulator is provided in front of the television receiver, an image can be displayed on the receiver. Become.

[0030]

As described above in detail, in the signal level measuring device of the present invention, the absolute level of the input signal can be measured for each desired channel and the reference signal for the level check of the receiving system can be output. Moreover, the frequency of the reference signal can be changed. Therefore, the level check of the receiving system can be performed corresponding to the transmission signal of the system, and the accuracy of the level check can be improved. Further, for the generation of the reference signal, an oscillator used for channel selection at the time of measuring the signal level is also used, and by superimposing the video signal on the reference voltage of the oscillator, the reference signal FM-modulated by the video signal is generated. Since it is generated, the device configuration can be simplified and the cost can be reduced as compared with the conventional device.

[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 a configuration of a signal level measuring device according to an embodiment.

FIG. 3 is a flowchart showing a reference signal output process executed by a control circuit.

FIG. 4 is an explanatory diagram illustrating a connection state of a signal level measuring device and a check method thereof when a level check of an actual receiving system is performed using a reference signal.

[Explanation of symbols]

10 ... Signal level measuring device 12 ... Input terminal 14
... RF amplification circuit 16 ... Oscillator 18 ... Mixer 20 ... IF amplification circuit 22 ... BPF (bandpass filter) 24 ... Detection circuit 26 ... A / D converter 28 ... Divider 30 ... PLL
Circuit 32 ... External output terminal 34 ... Video signal generation circuit 3
6 ... Display unit 38 ... Operation unit 40 ... Control circuit SW1 ... Changeover switch

Claims (1)

[Claims] 1. An oscillator whose oscillation frequency can be controlled by a control voltage, and an oscillation signal from the oscillator and an input signal from the outside are mixed so that a signal of a predetermined channel included in the input signal has a predetermined measurement frequency. And a frequency conversion means for converting the frequency into a measurement frequency by the frequency conversion means to control the oscillation frequency of the oscillator by adjusting the control voltage so as to be a signal of a channel designated from the outside. In a signal level measuring device comprising tuning control means and measuring means for measuring the absolute level of the signal converted to the measurement frequency by the frequency converting means, the operation mode of the device is measured and the signal level is measured. Operation mode switching means for switching from the measurement mode to the output mode for outputting the reference signal to the outside, and the device by the operation mode switching means. When the operation mode of is switched from the measurement mode to the output mode,
The output of the oscillator is connected to the external output terminal instead of the frequency converting means, and the oscillation output switching means for outputting the oscillation signal from the oscillator as the reference signal from the external output terminal, and also by the operation mode switching means. When the operation mode of the device is switched from the measurement mode to the output mode, a control voltage for controlling the oscillation frequency of the oscillator to an output frequency designated from the outside is used instead of the tuning control means. And a video signal superimposing means for superimposing a predetermined video signal on the control voltage applied to the oscillator by the output frequency controlling means.