JPH0140061Y2 - - Google Patents

Description

[Detailed description of the invention] This invention relates to a level measuring device used when installing or inspecting a dual conversion type microwave receiving device such as a satellite broadcast receiving device. To provide a level measuring device which is simple and can easily measure the levels of a plurality of signals.

Embodiments of the present application will be described below with reference to the drawings.

FIG. 1 is a diagram showing level measurement of a satellite broadcast receiving device. Reference numeral 1 denotes a parabolic antenna, which receives, for example, satellite broadcasting from a broadcasting satellite in the 3.7 to 4.2 GHz band. Reference numeral 2 denotes an antenna base, which allows the azimuth and elevation angle of the parabolic antenna 1 to be adjusted. 3 is a first converter, which is a low-noise converter commonly called LNC, which converts the satellite broadcast signal into a signal at a first conversion frequency, for example, a 1.2 GHz band, and sends it to a subsequent stage. 4 is a horn opening and is an input end of the first converter 3. 5 indicates an output terminal of the first converter 3. 6 is the first
Output measurement terminal provided on converter 3,
A signal (hereinafter referred to as the first output measurement signal) whose level is always weakened at a constant rate compared to the output of the output terminal 5 is outputted, and a level measuring device 18 to be described later is connected to the first output measurement signal. It is used to measure the output level of converter 3. As is well known, a level measuring device 1 is connected to the output measuring terminal 6.
Even if 8 is connected or removed, the output of output terminal 5 is not affected. A second converter 7 converts the signal from the first converter 3 into a signal at a second conversion frequency, for example, a 70 MHz band, and sends the signal to a subsequent stage. Reference numeral 8 indicates an input terminal of the second converter 7, and reference numeral 9 indicates an output terminal. 10 is an output measurement terminal provided in the second converter 7, and as in the case of the first converter 3, a signal (hereinafter referred to as the second output) whose level is always weakened at a constant rate than the output of the output terminal 9 is used. A signal (referred to as a measurement signal) is output. The connection and removal of the level measuring device 18 is the same as that of the output measuring terminal 6 of the first converter 3.
A receiver 11 selects a specific station from among the signals from the second converter 7 and converts the selected signal into a signal in a frequency band and modulation format that can be received by a general television receiver. 12 and 13 indicate an input terminal and an output terminal of the receiver 11, respectively.
14 indicates a television receiver. Reference numerals 15, 16, and 17 are transmission lines connecting each device, and coaxial cables are used, for example. As described above, a reception method using two converters, the first converter 3 and the second converter 7, is called a dual conversion method. Next, 18 is a level measuring device, which is used for both measuring the output of the first converter 3 and the output of the second converter 7. This configuration will be detailed later. 19 is an input terminal of the level measuring device 18. Reference numeral 20 denotes a connection line connecting the input terminal 19 and each output measurement terminal, and a coaxial cable of a fixed length is used.

Level measurement during installation of the satellite broadcast receiving apparatus with the above configuration will be explained. First, as shown in FIG. 1, the level measuring device 18 is connected to the output measuring terminal 10 of the second converter 7 using the connecting wire 20.
Next, the base 2 is adjusted so that the level of the signal input to the level measuring device 18 is maximized (so that the level indication on the display device 31, which will be described later, becomes maximum), and the azimuth and elevation angle of the antenna 1 are adjusted. Make rough adjustments. Furthermore, the level measuring device 18 is connected to the output measuring terminal 6 of the first converter 3, and the base 2 is adjusted again so that the level of the signal input to the level measuring device 18 is maximized. This involves fine-tuning the azimuth and elevation angles. The former is a level measurement in the 70MHz band.
The latter is a level measurement in the 1.2 GHz band, and can be easily measured with a single measuring device 18.

Next, to explain level measurement at the time of inspection in the event of a failure of the satellite broadcast receiving device, first, the level measuring device 18 is connected to the output measuring terminal 6 of the first converter 3, and it is checked whether a specified level is being output. If the specified level of 1.2 GHz output is not obtained at this time, it means that the direction or orientation of the antenna 1 has moved, or that the first converter 3 has malfunctioned. If there is no problem with the output of the first converter 3, then connect the level measuring device 18 to the output measurement terminal 10 of the second converter 7 and check whether the specified 70MHz band signal is being output. . If an output at a specified level is not obtained at this time, it is due to a break in the transmission line 15 or a failure in the second converter 7. If there is no problem with the output of the second converter 7, there is a failure in the transmission line 16, receiver 11, or the like.

Next, FIG. 2 shows a block circuit diagram of the level measuring device. 1 for those corresponding to Figure 1.
They are shown with the same reference numerals as in the figure. 21 is an amplifier circuit, which converts the first conversion frequency of the 1.2GHz band.
Amplify the output measurement signal. 22 is a band pass filter that passes the second output measurement signal in the 70 MHz band, which is the second conversion frequency, and blocks other signals. 23 is a level adjustment circuit that adjusts the level of the first output measurement signal that appears at point A when measuring the output of the first converter 3, and the second output that appears at point A when measuring the output of the second converter 7. The level of the measurement signal is adjusted in advance so that it is almost the same as the level of the signal for measurement, so that there is no need to switch the level range each time when measuring the level of each converter. This is to avoid the need to widen the dynamic range of the various components up to 31, and is made up of, for example, an attenuation circuit. Note that the first output measurement signal,
If the second output measurement signals are set at the same level and applied to the input terminals 19, and the level difference between those signals appearing at point A is recorded in advance as a calibration value on the display device 31, which will be described later, the first and second The level of both output measurement signals can be measured.

24 is a local oscillation circuit. The oscillation frequency of this local oscillation circuit is determined by the oscillation frequency of each of these two frequencies, regardless of which wave signal selectively enters the mixer 25 among the two waves of the first conversion frequency and the second conversion frequency. It is set so that one signal can pass through one bandpass filter 26 provided at the next stage of the mixer 25 and reach the display device 31, respectively. Therefore, the first conversion frequency, the second conversion frequency and the mixer The oscillation frequency is set in consideration of the mutual relationship between the frequency of the signal output from the bandpass filter 25 and the center frequency of the passband determined by the bandpass filter 26.

In the present invention, the frequency of the second output measurement signal (second conversion frequency) is subtracted from the frequency of the first output measurement signal (first conversion frequency), and the halved value is the oscillation frequency. and set it to oscillate.

In this embodiment, the first conversion frequency is 1200MHz, so subtracting the second conversion frequency of 70MHz from these results in 1130MHz, and half of this is 565MHz. Therefore, from the local oscillation circuit 24, this 565MHz
Let's make it oscillate.

Next, the mixer 25 uses the oscillation signal of the local oscillation circuit 24 to convert the frequency of the output measurement signal sent from the input terminal 19 side. In this example, the first conversion frequency is 1200MHz, so
By (+) and (-) of 1200MHz and 565MHz,
Two types of signals are output: 635MHz and 1765MHz.

In addition, in the case of the second conversion frequency, this is 70MHz, so depending on the (+) and (-) between 70MHz and 565MHz, there are two types: 635MHz (the same value as the first conversion frequency above) and 495MHz. signal is output.

As described above, the mixer 25 outputs three types of signals with different frequencies.

Reference numeral 26 denotes a band pass filter which allows only one type of common frequency among the output measurement signals frequency-converted by the mixer 25 to pass through, and blocks the other two types of frequencies that are not common.

Therefore, in this embodiment, the bandpass filter 26
635MHz, which is half of the sum of the first conversion frequency (1200MHz) and the second conversion frequency (70MHz), so that the center frequency of the passband matches the above 635MHz.
, and the passband width is set to, for example, 20MHz.

Reference numeral 27 denotes an attenuation circuit, which is used for switching the level range of the display device 31, which will be described later. 28 is an amplifier circuit,
In this example, a 635MHz signal is amplified. 29 indicates a detection circuit. 30 is a DC amplifier, and 31 is a display device for displaying the level.

Level measuring device 1 when measuring the level using the level measuring device 18 having the above configuration as shown in FIG.
The operation of 8 will be explained using FIG.

First, to measure the output of the first converter 3, the input terminal 19 of the level measuring device 18 and the output measuring terminal 6 are connected using the connecting line 20. The first output measurement signal of 1.2 GHz applied to the input terminal 19 is amplified by the amplifier circuit 21 and frequency converted by the mixer 25 to become two types of signals of 635 MHz and 1765 MHz. Among these signals, the 635MHz signal passes through the bandpass filter 26 and is sent to the amplifier circuit 28.
The DC current is amplified by the DC amplifier, and detected by the detection circuit 29 to become a DC current having an amplitude corresponding to the output level of the first converter 3. The DC current is amplified by the gain of the DC amplifier and reaches the display device 31. Therefore, the output level of the first output measurement signal at the first converter 3 is displayed on the display device 31, and as a result, the signal output level of the first converter 3 can be known.

Next, to measure the output of the second converter 7, the input terminal 19 of the level measuring device 18 is connected to the output measuring terminal 10. The level of the 70MHz second output measurement signal applied to the input terminal 19 is:
The level is higher than the level of the first output measurement signal by the conversion gain of the second converter 7. This signal is level-adjusted by a level adjustment circuit 23, passed through a bandpass filter 22, and frequency-converted by a mixer 25.

Here, two types of signals, 495 MHz and 635 MHz, are output, of which only the 635 MHz signal passes through the bandpass filter 26.

Thereafter, in the same manner as in the case of measuring the level of the first converter 3, the output level of the second output measurement signal at the second converter 7 is measured on the display device 31.

As described above, in the present application, the frequency of the output of each device is different, for example, a dual conversion receiving device using two converters, a first converter and a second converter. Even in such a case, if the level measuring device according to the present invention is used, a single level measuring device can be used, and the level can be easily measured without having to switch the frequency range every time.

Furthermore, since the local oscillation circuit only needs to oscillate at one frequency, it is possible to provide an inexpensive level measuring device with a simple configuration.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention; FIG. 1 is a diagram showing level measurement of a satellite broadcasting receiver, and FIG. 2 is a block circuit diagram of the level measuring device. 3...First converter, 5...Output terminal, 6
...Output measurement terminal, 7...Second converter,
9... Output terminal, 10... Output measurement terminal, 18
... Level measuring device, 19 ... Input terminal, 24 ...
Local oscillation circuit, 25...mixer, 26...band pass filter, 29...detection circuit, 31...display device.

Claims (1)

[Scope of utility model registration request] An input terminal for selectively receiving a signal at the first conversion frequency and a signal at the second conversion frequency, and a signal having a frequency equal to half the difference in frequency between the first conversion frequency and the second conversion frequency. When the signal of the first conversion frequency and the signal of the second conversion frequency selectively enter the local oscillation circuit that oscillates the signal, these signals and the signal from the local oscillation circuit are mixed to generate two types of each a mixer configured to send out the signal to the next stage; a bandpass filter configured to pass only one type of signal common to each of the two types of signals outputted from the mixer; A level measuring device consisting of a display device that displays the level value of the signal passing through it.