JPH0454401B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an antenna direction adjustment device that can be used when installing an antenna for receiving SHF satellite television broadcasts.

Conventional configurations and their problems Satellite television broadcasting is about to be put into practical use, but such a system requires a high-gain receiving antenna device because the radio waves from the satellite are weak. Such a satellite broadcast receiving antenna device has a sharp directivity, and it is very difficult to set the antenna device so that the direction of the antenna matches the arrival direction of radio waves.

By the way, broadcast radio waves transmitted from one satellite are internationally assigned frequency bands and have a plurality of channels.

However, in practice, the radio wave output level, number of channels, and broadcast frequency of a satellite vary to some extent. Under such radio wave conditions, in order to better receive radio waves from the satellite broadcasting the desired program,
In order to adjust the direction of the antenna toward the desired satellite, the antenna should be adjusted so that it can capture the radio waves with the maximum reception level from among the radio waves arriving from the same direction. In other words, the installation of the antenna is usually
After determining the approximate direction and temporarily fixing the antenna, adjustments are made.
It is rare that a desired broadcasting satellite exists and radio waves from adjacent broadcasting satellites are also received.

One method of adjusting the direction of a conventional antenna device is as shown in FIG.
The strength of the incoming radio waves is measured between the cable 7 that connects the outdoor antenna device consisting of the antenna 2 and microwave device 3 placed indoors, and the indoor receiving device 5 and television receiver 6 placed indoors. An antenna direction adjustment device 8 for display is connected, and the direction of the antenna 2 is adjusted and fixed in the direction where the intensity of radio waves is maximized.

FIG. 2 is a block diagram showing the structure of an example of an antenna direction adjusting device conventionally used in such cases. The satellite radio waves in the 12 GHz band received by the antenna 2 are transmitted to the first antenna in the 1 GHz band by the microwave device 3.
The frequency of the signal is converted into an intermediate frequency band and applied to the input terminal 9 of the antenna direction adjuster. The first intermediate frequency band signal supplied to the input terminal 9 is sent to the mixer 10
is fed to one input of The other input of the mixer 10 is supplied with the oscillation output of a voltage variable local oscillator 12 whose oscillation frequency is variably controlled periodically by the oscillation output from the sweep oscillator 11, and these two inputs are mixed. , a signal in the first intermediate frequency band is converted to a signal in the second intermediate frequency band. The oscillation output of the sweep oscillator 11 is a sawtooth wave with a constant period, and when this oscillation output is at a predetermined DC level, the voltage variable local oscillator 12 operates and oscillates.
A conversion from the intermediate frequency to a second intermediate frequency is performed.

Therefore, the output of the mixer 10 is a second intermediate frequency signal obtained by frequency-converting the first intermediate frequency input signal corresponding to a certain predetermined level. Second
The output signal of the mixer 10, which has been converted to an intermediate frequency of guided by. Furthermore, the detector 16 is configured so that the output of the detector 16 always has a constant detection output level.
and the output of the reference voltage source 17, the comparator 18
and correct the detection output level. The output of comparator 18 is supplied to DC amplifier 19 and amplified.

Note that the comparator 18 and the DC amplifier 19 constitute an AGC feedback loop. At the terminal 20, a signal amplified by the DC amplifier 19 and indicating the strength of the received signal appears. This detection signal is an impulse whose magnitude corresponds to the magnitude of the signal strength each time the input signal is converted to the second intermediate frequency in the oscillation period of the sweep oscillator. In order to display the maximum impulse size of this detection signal on the meter, the detection signal is input to the maximum voltage holding circuit 21, where the maximum level is held, and the meter drive circuit 22 is operated according to this holding level. , drives the display device 23.

However, in such a conventional device, when the microwave device 3 has no gain deviation with respect to the signal within the first intermediate frequency band, as shown in FIG. 7a, the maximum voltage holding circuit 21 The input signal of , that is, _the signal at the terminal 20 is as shown in _FIG .
The voltage e′ ₁ (=e ₁ +e _o ), which is the sum of the noise voltage e _o
3. In this case, when the noise is uniformly distributed regardless of the frequency, if the microwave device 3 has no gain deviation with respect to the signal within the first intermediate frequency band, the channel of the signal with the maximum level is You can choose. however,
If the microwave device 3 has a gain deviation with respect to a signal within the first intermediate frequency band, for example, if the frequency characteristic of the gain is as shown in FIG. Since the distributed noise component is detected to be larger at frequencies where the gain is high, the input signal of the mixer 10 is as shown in FIG. 8a.
The signal ₁ received by antenna 2 as shown in
In ₂ , although ₂ has a smaller signal strength than ₁ , due to the frequency deviation, the noise component e _o is superimposed on the high-gain frequency signal ₂ , so the component e ₁ is higher than the high-frequency signal ₁ . The detection output of the maximum voltage is larger for the signal of frequency ₂ , as shown in FIG. 8b. Therefore _{, the maximum voltage held in the maximum voltage holding circuit 21 is the voltage e' 2 ( = e 2} +
e _o ) is displayed as the maximum level, and the channel of the signal with frequency ₂ is selected as the channel with the maximum input signal level for that satellite broadcast. Therefore, when adjusting the antenna in the direction of the maximum level by looking at the display on the display device, the display level when the antenna is correctly pointing in the direction of the satellite and the display level when it is not pointing in the direction of the satellite. The difference is so small that it is difficult to align the antenna in the correct direction.

Furthermore, in a microwave device having the frequency characteristic of gain as shown in Figure 5a, if there is no signal at the frequency corresponding to the maximum gain, for example, there is no signal at frequency ₂ , and the noise level is lower than the maximum level. When the voltage level of the sum of the signal and noise at frequency ₁ becomes small, the maximum voltage holding circuit 21 assumes that the noise component is the voltage signal with the maximum level.
will be held. Therefore, weak radio waves are no longer detected. As a result, it has the disadvantage that the original function of the antenna direction adjustment device, which adjusts the antenna direction using weak radio waves, does not work.

OBJECT OF THE INVENTION The present invention eliminates the conventional drawbacks as mentioned above,
It is an object of the present invention to provide an antenna direction adjustment device that can satisfactorily adjust the antenna direction even in a microwave device in which the gain differs depending on the frequency.

Structure of the Invention The present invention includes a mixer that receives a signal in a first intermediate frequency signal band as an input signal, and a mixer that converts the signal in the first intermediate frequency signal band to a second intermediate frequency. A voltage variable frequency local oscillator supplies the oscillation output to the mixer, and a triangular wave with a constant period is output to the tuning voltage application terminal of the voltage variable frequency local oscillator so that an output for frequency conversion can be obtained from the voltage variable frequency local oscillator. a second intermediate frequency amplifier that amplifies the output signal of the mixer; a detection circuit that detects the detected output of the output signal of the second intermediate frequency amplifier; and a DC component that reproduces the detected output. A regeneration circuit, a maximum voltage holding circuit that holds the maximum voltage of the detection signal from which the DC component is regenerated, and a display device that displays the magnitude of the input signal by displaying the held voltage. It is characterized by the ability to measure the magnitude of input signals without being affected by differences in the gain of microwave devices, and to correctly adjust the antenna in the direction of the satellite.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. In FIG. 3, a terminal 25 is an input terminal connected to a microwave device 3 having the frequency characteristics shown in FIG. Enter. Mixer 26 is voltage variable frequency local oscillator 3
0 constitutes a tuning circuit, and the tuning voltage applied to the voltage variable frequency local oscillator 30 is applied to the sweep oscillator 2 which generates a low frequency triangular wave (sawtooth wave).
The voltage variable frequency local oscillator 3 is swept with a period T ₁ by the output signal (sawtooth signal) from 9.
The oscillation frequency of 0 is changed with a period T ₁ . terminal 2
Reference numeral 7 denotes a terminal connected to the indoor device 5 by a cable 7, and serves as a power supply terminal for operating the microwave device via the power supply and the chain yoke 28 for operating the antenna direction adjuster.

The voltage variable frequency oscillator 30 has an oscillation frequency band that can tune and sweep the entire first intermediate frequency band to the second intermediate frequency, and the oscillation output of the voltage variable frequency oscillator 30 and the first intermediate frequency signal are combined. An output occurs when the difference between
A signal with a waveform as shown in FIG. b is extracted.

The signal converted to the second intermediate frequency passes through the variable gain amplifier 31 , the bandpass filter 32 , and the second intermediate frequency amplifier 33 and is guided to the level detector 34 . Here, in order to keep the output of the level detector 34 constant, a reference voltage generator 35 and a comparator 36 are used.
and a DC amplifier 37 constitute an AGC circuit, and the gain of the variable gain amplifier 31 is changed according to the input signal level. At this time, a voltage corresponding to the input signal level is generated at the control terminal 38 of the variable gain amplifier 31.

The gain of the variable gain amplifier 31 is controlled by the output voltage of the DC amplifier 37.
The bandpass filter 32 has a gain characteristic such that the gain becomes smaller as the control input voltage from the mixer 26 increases, and the bandpass filter 32 amplifies the second intermediate frequency signal output from the mixer 26, and the bandpass filter 32 has a center frequency at the second intermediate frequency.
It has filter characteristics of 402.7MHz and 1 channel bandwidth.

FIG. 4 shows the output waveform of the sweep signal generator 29 and the voltage waveform generated at the control terminal 38.

Here, it is shown that when the voltage of the sweep signal generator 29 is a, the input signal is converted to the second intermediate frequency and is expressed as an impulse signal at the control terminal 38.

The output signal of the terminal 38 which detected the magnitude of the input signal is sent to the DC component regeneration circuit 39 and the maximum voltage (amplitude)
It is led to a holding circuit 40, a meter driving circuit 41, and a display device 42, and displays the maximum value of the input signal.
The process of obtaining the voltage at the terminal 38 is the same as the conventional one, but the voltage generated here will be explained in more detail.

Based on the principle of AGC operation, the voltage generated at the terminal 38 is proportional to the magnitude of the signal from the bandpass filter 32 output from the mixer 26. At this time, as mentioned above, if there is a signal, a voltage proportional to the signal is generated, but when there is no signal, the bandwidth of the bandpass filter 32 is set to B, and the gain from the antenna to the mixer 26 is set to G. , if the equivalent noise temperature of the receiver is T, then the signal level P _io is P _io =GKTB (where K is Boltzmann's constant).

That is, if the gain of the second intermediate frequency amplifier 33 is sufficient, the terminal 38 is measuring the noise level when no signal is input as the second intermediate frequency.

Also, the frequency characteristics of the gain of the microwave device are
In the case of FIG. 5a, the mixer 26 has input signals at frequency ₁ with a low gain and frequency ₂ with a high gain.
The output signal of the terminal 38 is as shown in FIG. 9a.
The waveform shown in FIG. 9b is generated. At this time, when only the signal component is extracted using the generally known DC component regeneration circuit 39 using the noise level as the reference voltage level, a signal waveform as shown in FIG. 9c is output, and the maximum voltage is maintained. Maximum voltage e ₁ on circuit 40
is maintained, and the signal with the maximum signal level can be displayed on the display device 42 via the display drive circuit 41. As a DC component regeneration circuit, a circuit with a configuration as shown in Fig. 10 is common.
As shown in FIG. 1 of Japanese Patent Application No. 55-5552 as a conventional example, a DC component regeneration circuit is known that allows input signals to pass signals having a predetermined level or higher and signals having a predetermined frequency or higher.

In FIG. 10, for example, when the waveform shown in FIG. 9b is applied to the input terminal 51, the low frequency component is blocked by the capacitor 52, and a diode is connected in parallel with the first resistor 54 of the CR circuit consisting of the capacitor 52 and resistor 54. 53 is connected, so when there is no signal, that is, there is no signal of frequency ₁ or frequency ₂ ,
Diode 53 becomes conductive and the output voltage at terminal 55 is fixed at a predetermined voltage level of power supply 56. frequency
₁ , when a signal of frequency ₂ is input, the diode 53 becomes non-conductive, and the capacitor 52 and resistor 54
The CR circuit operates as a simple high-pass filter circuit with a bias voltage, and corresponds to signals of frequency ₁ and frequency ₂ as shown in FIG. Voltage
e ₁ and e ₂ are obtained.

As can be understood from Fig. 5b, the conventional antenna direction adjuster uses _two signals with a small antenna input signal level, but with this device, the influence of the gain difference is small and the signal level is constant. The loudest signal will be used.

By the way, by changing the antenna direction,
In areas where satellite television broadcasts from multiple geostationary satellites can be received, the maximum strength radio wave size is automatically displayed to confirm which geostationary satellite the antenna is facing when adjusting the antenna direction. The means may be difficult to use in the above embodiments.

FIG. 6 shows another embodiment of the present invention, which is equipped with means for checking the frequency of radio waves sent from a satellite. Its basic configuration is the same as that of the embodiment shown in FIG. By switching from to manual side M, it has a function of measuring the input signal level at the input frequency selected by the tuning voltage generator 46.

When adjusting the antenna direction, first set the changeover switches 43, 44, and 45 to the automatic side A, and when the input signal reaches the maximum, switch to the manual side M, and turn the selection voltage generator 46 on. The antenna direction adjustment is completed by checking whether the indicated value on the display device 42 reaches the maximum at the preset voltage position, that is, whether there is an input signal.

Effects of the Invention As described above, according to the present invention, the noise level of the receiver can be removed by regenerating the DC component and the magnitude of the input signal can be displayed on the display device, and the magnitude of the gain of the microwave device can be adjusted. Regardless of
The direction of the antenna can be adjusted to point correctly in the direction of the incoming radio waves.

[Brief explanation of the drawing]

FIG. 1 is a front view showing how the antenna direction adjustment device is used, FIG. 2 is a block diagram of a conventional antenna direction adjustment device, and FIG. 3 is a block diagram of an antenna direction adjustment device according to an embodiment of the present invention.
4 and 5 are voltage waveform diagrams for explaining the operation of the present invention, FIG. 6 is a block diagram showing an antenna direction adjustment device according to another embodiment of the present invention, and FIG. 7 is a diagram showing the antenna direction in a conventional example. A waveform diagram when a signal from a microwave device with no difference in gain due to frequency is input to the adjustment device. Fig. 8 is a signal waveform diagram in a conventional example when the gain of the microwave device has frequency characteristics. Fig. 9 10 is a signal waveform diagram of the antenna direction adjustment device according to the present invention when the gain of the microwave device has frequency characteristics, and FIG. 10 is a basic configuration circuit diagram of the DC component regeneration device. 2...Antenna, 3...Microwave device, 5...
...Indoor receiving device, 6...Television receiver, 1
0,26...Mixer, 13,31...Variable gain amplifier, 14,32...Band pass filter, 15,
33... Second intermediate amplifier, 16, 34... Level detector, 12, 30... Voltage variable frequency local oscillator, 11, 29... Sweep oscillator, 21, 40...
Maximum voltage holding circuit, 23, 42...Display device, 3
9... DC component regeneration circuit, 43, 44, 45... Changeover switch, 46... Tuning voltage generator.

Claims (1)

[Claims] 1 A mixer that receives a signal in a first intermediate frequency signal band as an input signal, and supplies an oscillation output to the mixer so that the mixer converts the signal in the first intermediate frequency signal band to a second intermediate frequency. a sweep oscillator that outputs a triangular wave of a constant period so that an output for frequency conversion is obtained from the voltage variable frequency local oscillator to a tuning voltage application terminal of the voltage variable frequency local oscillator; a second intermediate frequency amplifier that amplifies the output signal of the device;
a detection circuit that detects the detection output of the output signal of the second intermediate frequency amplifier; a DC component regeneration circuit that regenerates the detection output; and a maximum voltage holding circuit that maintains the maximum voltage of the DC component regenerated detection signal. and a display device that displays the magnitude of the input signal by displaying its holding voltage.