JPS6277787A - Satellite broadcast receiver polarizer control circuit - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a polarizer control circuit for a satellite broadcasting receiver that receives a plurality of television signals having different planes of polarization transmitted from a satellite.

2. Description of the Related Art Traditionally, satellite broadcasting (television signals) in the 4 GHz band (C band) in the United States and other countries have consisted of two types of signals with vertical and horizontal polarization planes. For example, when a television signal of 24 channels (3.72 to 4.1 sGHz) is emitted from one satellite, odd-numbered channels are sent with vertical polarization planes and even-numbered channels with horizontal polarization planes. (There are also satellites with opposite polarization planes.) Each channel has an occupied band of 40 MHz and a CH space of 20 MHz, and the polarization plane is switched to prevent interference. A polarizer installed at the focal point of the receiving antenna.
The configuration is such that a signal with either a vertical or horizontal polarization plane is extracted and transmitted to a low noise converter (LNB) provided after the polarizer. FIG. 3 shows the configuration of the above-mentioned satellite broadcasting receiver.

In Figure 3, 1 is an antenna, 2 is a polarizer, and 3 is an LN.
B, 4a, 4b are LNB3. At the pole of the polarizer 2, along the pole 4b, the signal cable and the power to the polarizer 3,
Control Shinkyuden iA line 5 is installed. 6 is antenna 1
The elevation angle and direction of antenna 1 (towards the east or west)
There is no way to say that it can change. 7 is a satellite broadcasting receiver, which consists of the following components. 8 is 2nd
A tuner, also called a mixer, with a center frequency of 3.72 to 4.18 (rHz t7) at L N B 3.
The 4 waves are converted into 24 waves of 970 to 1430 MH2, and the tuner 8 is tuned to one of the waves. The output of the tuner 8 is an IF frequency of 510 MH2, and the band r1 is, for example, 2
There is 5MHz. 9 is a video intermediate frequency amplification circuit (hereinafter referred to as IF
circuit), and a band 1 IfI filter (B, P, F
'). 10 is a wideband FM detection circuit, for example, PLL detection is used. An audio detection circuit 11 performs FM detection on the audio carrier wave being output from the 11-digit FM detection circuit 1o, and the output of this audio detection circuit 11 is sent to an audio signal processing circuit 13.
The signal is converted into an appropriate level and frequency characteristic and outputted, and the output of the audio signal processing circuit 13 is also supplied to the RF converter 14.

On the other hand, the video signal processing circuit 12 removes the high-frequency components of 4.2 MHz or higher and the energy diffusion signal, outputs it at an appropriate level, and sends the video signal to the RF converter 14 for video signal processing. provides the output of

15 is an automatic polarization control circuit that changes the plane of polarization and stops it at the optimum point.

An example of the automatic polarization control circuit 16 is shown in FIG.

First, let N channel be the desired wave. The signal being sent (
)l-1), N, (N+1) spectra are IF
When thinking in terms of belts, it is assumed that they are at the same level, as in Figure 5.

In this case, the center of the (N-1) channel is 490MH2
, (N+1) channel center is assumed to be 530MH2. When the plane of polarization of the polarizer 2 is between vertical and horizontal, when the signal passes through a bandpass filter as shown in Figure 6B, the output of the IF circuit 9 will be as shown in Figure 6C. . Assuming that the N channel signal is vertically polarized, when the plane of polarization of the polarizer 20 becomes vertical, the signal of the adjacent channel drops by about 15 dB, as shown by the dotted line in FIG. (The polarizer separation degree is 1
5dB) Therefore, when passing through a bandpass filter,
The spectrum will be as shown in Figure 5.

In the above explanation, the spectrum is illustrated assuming that the FM frequency shift of a normal television signal is about 10 MHz on average. The same applies to the following countries. On the other hand, the relationship between the polarization plane of the polarizer 2 and the output of the MGO detection circuit 16 in FIG. 3 is shown by the solid line in FIG. AGC detection circuit 1
6 generates a DC voltage proportional to the output of the IF circuit 9, controls the gain of the tuner 80, and controls the gain of the IF circuit 9.
Keep force and output constant. That is, the IF circuit 9 has MU G(3
Do not apply. Therefore, when the polarization plane becomes vertical and the signal amplitude becomes maximum, the output of the AGO detection circuit 16 becomes maximum. That is, from the reference point 0 degrees, the polarization plane is 146 degrees or more in the horizontal direction, from the point beyond the polarization plane of the polarizer 2 (Polar 6--globe in the case of a rotor), that is, from ST in Fig. 7. Assume that the polarization plane is changed horizontally (-45 degrees), 0 degrees, and vertically (+45 degrees), and that one sweep of the polarization plane ends at a point further beyond the vertical, that is, at END in Figure 7. , in an ideal operating state, changes as shown by the solid line in Figure 7. Similarly, the relationship between the polarization plane angle and the output of the AGC detection circuit 16 when receiving a horizontally polarized signal is the seventh
This is the dotted line in the figure. Figure 7: In an ideal situation, the relationship between the dotted line and the solid line for a person is obtained.
Figure, Figure 7 describes with people. Assuming that the desired wave is channel N, when channel N is specified, the output of the three-man power NOR gate 21 becomes a low level, and the flip-flop 2o
is set, its Q output becomes high level, and the sweep voltage generation circuit 19 generates a sawtooth wave voltage or a triangular wave.

On the other hand, the output of the three-man power NOR gate 21 is transmitted to the peak hold circuit 17, and the held voltage is discharged. As the output voltage of the sweep voltage generation circuit 19 changes, the plane of polarization of the polarizer 2 changes.

When using polarizer 2 (7V), which is called a ferro feed, the sweep voltage is amplified and used. The rotation angle of the waveform is determined by the pulse generator 22.
supply to Now consider the d-polar rotor. From ST in Figure 7 A, change the angle θ゜ plane, and at +45 degrees, A(1,C
Assuming that the voltage reaches the maximum value, this peak voltage Pv is held at its peak by the peak hold circuit 17. When the sweep voltage 1E reaches IID, it changes again to ST or C] in the same way. At this time, the level comparator 18 detects that the AGC detection circuit 1
Compare the output of 6 and the output of peak hold circuit 17 [7,
When they match, a negative pulse is output and the flip-flop 20
Reset. The Q output of the flip-flop 2o becomes low level, the sweep voltage of the sweep Ichikawa generation circuit 19 is no longer generated, and the D output that rotates the rotor of the polarizer becomes
G power is also no longer supplied from the DC voltage supply circuit 23. (The DC voltage supply circuit 23 is
(provides DC power to 2 only during high level) Therefore, the polarization plane of the polar rotor stops at the optimum position of +45 degrees. Next, consider a case where the desired wave is 4 to 51 iB weaker than the adjacent CH. (Such a situation actually occurs in America.) When the plane of polarization of the polarizer is between horizontal and vertical, or when there is no polarizer 2, the output of tuner 8 is the 6th It becomes a spectrum like a diagram. At this time, if the polarization plane in the state 677 is horizontal and now vertical, the output of the tuner 8 will be as shown in Figure 6, when the polarization plane of the polarizer does not start to change, Even after passing through the filter, the spectrum will be as shown in Figure 6. In such a state, when the plane of polarization starts to change from ST, <PH' becomes a peak as shown by the dashed line in Figure 7B, and becomes higher than Pv', or pv+ becomes higher than PI('). Even if it is high, it may reach a peak before the normal Pv.In this case, the output of the tuner 8 will be as shown in FIG. 6G.

When the influence of adjacent waves is small, the optimum plane of polarization is determined by the solid line or broken line in FIG. 7B in the same way as in the case of FIG. 7A. It also operates as described above when the power is turned on and when the sweep 9/＼- start is instructed manually.

The so-called terrestrial interference is 500MH2.

If it is around 520MHz, the P in Figure 7 will change due to its influence.
The AGO voltage becomes maximum at points other than H2Pv, making it impossible to set the optimum polarization plane.

Problems to be Solved by the Invention However, the above-described configuration has the problem that the following malfunctions often occur due to the strength of radio waves, interference waves, etc.

(1) Malfunction due to the influence of adjacent channel signals.

(2) Malfunction due to input difference between adjacent channel and desired signal.

(3) Malfunction due to terrestrial interference.

SUMMARY OF THE INVENTION In view of the above-mentioned problems, it is an object of the present invention to provide a polarizer control circuit for a satellite broadcasting receiver that does not cause the above-mentioned errors.

Means for Solving the Problems The present invention solves the above-mentioned problems, and includes a polarization plane control circuit that sets a polarizer that selects a polarization plane to an optimal state, and a polarization plane control circuit that controls the polarization plane. A circuit for determining the state of the polarization plane of the polarizer that supplies a control signal indicating that the 10'-p polarization plane of the device is in the optimum state is provided, and the circuit is inserted after the bandpass filter in the video signal intermediate frequency amplification stage. The output of the ground interference removal filter is input to the state determining circuit.

Operation The present invention utilizes the attenuation characteristics of the terrestrial interference removal filter with the above-described configuration to eliminate the effects of terrestrial interference and adjacent channel signal components, and to accurately set the plane of polarization.

EXAMPLE An example of the present invention will be described below with reference to the drawings. FIG. 1 shows a circuit block diagram of a polarizer control circuit of a satellite broadcasting receiver in one embodiment of the present invention. In FIG. 1, the same parts as in FIGS. 3 and 4 are given the same numbers.

In addition, the same part of the operation as the conventional example in the figure can be achieved by directly connecting the output of the sweep voltage generation circuit 19 to the pulse generator 22.
Since this is the same as the conventional example, a description of the operation of each part other than the sweep voltage generating circuit 19 will be omitted.

11. In the United States, the center frequency f of the satellite broadcasting carrier is within the band of 3.70 to 4.20 GHz. against, ±10
Terrestrial radio waves exist at a distance of MHz and may be stronger than the TV signal. Therefore, the AGCj voltage is affected, causing errors in polarization plane settings and beats appearing on the screen, so terrestrial interference removal is necessary. It is well known that a filter (hereinafter referred to as TI filter) is used. In Fig. 1, 29 is a TI filter, and its characteristics are shown in Fig. 2B.
It has a passband shown in . In the case of a trap that removes only terrestrial interference, it is possible to consider a trap that only attenuates by 10 dB at 520M and 500M in Figure 2B, and does not attenuate the rest.
It is assumed that the outside of 520 MH2 (that is, ±10 MHz away from the center frequency of 510 MHz of the desired wave IF) is also attenuated as shown in the figure. When the channel designation circuit 31 is operated to designate N channel, the tuner 8
Since it is tuned to the channel, considering the frequency F band, the spectrum of the desired wave and the adjacent wave will be as shown in Fig. 2G.

However, it is assumed that the desired wave is sdB weaker than the adjacent wave, the plane of polarization of the received wave before the N channel is specified is horizontal, and the N channel is vertically polarized. The vertical and horizontal separation of the polarizer 2 is assumed to be 15 dB. In this state, when the output of the three-power NOR gate 21 becomes negative due to the pulse from the channel estimation circuit 31, the solitub flop 20 is sent, and the Q output of the flip-flop 20 becomes high level, the voltage supply circuit 23 outputs the polarized signal. Vessel 2
I) C power is supplied to the sweep voltage generation circuit 19
The sweep is started from the voltage at which the polarization plane of the polarizer 2 has the phase ST in FIG. The Q output of the flip-flop 2o is transmitted to the peak hold circuit 17, which discharges the peak hold voltage and sets the output of the OR gate 24 to a high level.
Via the protective resistor 25, the base of the switching transistor (hereinafter referred to as a transistor) 26 becomes high level, the transistor 26 becomes conductive, and the high frequency switching relay 27 is activated.
Current flows through the coil 27L, and the terminals a-c of the contact 278
A short circuit occurs between the two. The characteristics of the bandpass filter of circuit 9 are
Assuming that the solid line in the figure shows the transmission characteristics from the tuner 8 to the I2 circuit 9, the characteristics of the TI filter 29 shown in FIG. Even with the spectrum shown in Figure 2C, the output of the I2 circuit 9 will be as shown in the second diagram, with the peak P being closer to the peak P1 of the desired wave. , P2 are attenuated by 16 dB. When a separation degree of 1 csclB of the polarizer 2 is added to this and the plane of polarization is set correctly, Pl becomes a level 30 dB higher than Po and P2. , it goes without saying that if the desired wave and the adjacent wave are at the same level at the input of the tuner 8, Pl will be at a level β5 dB higher than Po and P2. In other words, when changing the plane of polarization, even if the desired wave is 5 dB weaker than the adjacent wave, the I2 circuit 9
In the output waste vector, P is P. , P2 is at least 15 dB higher than P2, so even if AGC detection is performed and the voltage peak point is considered to be the correct plane of polarization, almost no error will occur. That is, a curve of a solid line (a broken line if the N channel is horizontally polarized) in FIG. 7 is obtained. Even if the polarization planes match when you specify the N channel, if you sweep, the output of the IF circuit 9 will be in the state shown in Figure 2 (the state in Figure 2 C is the output of tuner 8). However, since the adjacency does not become any stronger, the peak of the MuGC voltage is correctly detected and held.

Next, the polarization plane memory, which is another feature of the present invention, will be described. Operate the AC on/off circuit 34 to turn on the power.
NI, and when the antenna switching circuit 30 is operated to change the angle of the antenna, the polarization plane control circuit 36
Clear sweep voltage memories 36 and 37. Next, when the desired wave (N channel) is specified, the sweep voltage generation circuit 19 generates a sweep voltage as described in IF. At this time, since the sweep voltage memories 36 and 37 are cleared, the sweep voltage generation circuit 19 The output is output as is, and the pulse width for controlling the polarizer is changed by the pulse generator 22. At this time, the peak P of the spectrum of the desired wave at the output of the sweep voltage generation circuit 9.

is the nearest adjacent wave peak P. , P, it is still higher than 15 dB even if it approaches, so the solid line curve of FIG. 7 is obtained. Next, when the sweep of the sweep voltage generating circuit 19 starts from ST in FIG. Stop. Sweep voltage at this time is sweep memory voltage 3
6. It is sufficient to perform sweep voltage HAD conversion and store it in memory as a digital value. Note that the pulse width of the pulse generator 22 at this time may be stored as a digital value. Next, when the X channel is specified, if the X channel is also vertically polarized, the voltage in the sweep voltage memory 36 is read from the polarization plane control circuit 35, transmitted to the pulse generator 22, the pulse width is directly specified, and the polarization is 1-1 After the minimum time (shorter than the sweep time) required to set the polarization plane, a signal is sent from the polarization plane control circuit 35 to the level comparator 18, and the level comparator 18 forces the A matching pulse is output and the flip-flop 2o is reset. At this time, the plane of polarization can be accurately set regardless of the strength of the input signal or the presence or absence of interference. If the X channel is a horizontally polarized wave, the sweep voltage memo +)37KId and nothing need be stored, so the polarization plane control circuit 35 transmits the output of the sweep voltage generation circuit 19 to the pulse generator 22 as it is. Therefore, the characteristic shown by the broken line in Figure 7 is obtained, the peak voltage P)I is held in the peak hold circuit 17, and in the second sweep, the output of the level comparator 18 becomes a low level at the PH point. , flip-flop 2
0 is reset, and the sweep voltage at this time is stored in the sweep voltage memory 37. That is, the polarization plane control circuit 35 has a flip-flop, a launch memory, a write/read control p-thick to the sweep voltage memory 38 and 37, and an AND O
Consists of R gate, sweep voltage memory 36.37
It has a function to check whether data is written to or not. ! , the polarization plane control circuit 36 can also be replaced with a microprocessor. Now, sweep voltage memo! , 136 and 136, and 136.37, when a channel is specified by the channel designation circuit 31, the polarization plane of that channel (determined by the type of satellite) is stored.

That is, the polarization plane control circuit 35 determines whether P)I or Pv (determined by the orientation of the antenna) is vertical or horizontal, and the voltage value corresponding to P)I or Pv stored in the sweep voltage memory 36 or 37 (sweep is not performed). The pulse generator 22
The probe of the polarizer 2 is rotated to set the plane of polarization vertically or horizontally. Therefore, the period during which the Q output of the flip-flop 20 is at a high level is shorter than when the sweep voltage generation circuit 19 is swept, and the period during which the relay 27 operates and the contact 27S is short-circuited between terminals a and a is also shorter. .

Now, when the polarization plane is set correctly, terrestrial interference (TI)
If the disturbance) is greater than a certain value, the TI disturbance detection circuit 28 detects the TI disturbance, the output of the TI disturbance detection circuit 28 becomes high level, the transistor 26 becomes conductive, the relay 27 operates, and the contact 278 becomes the terminal. Even if a short circuit occurs between a and c and the image quality deteriorates to some extent, the video signal in the pass band indicated by the broken line in Figure 2 is automatically displayed on the CRT.

Furthermore, even if the output of the TI interference detection circuit 28 does not reach a high level, the TI switch of the manual start switch 33 can operate the relay 27.

If the memory value in the sweep voltage memory 36.37 is inappropriate, when the manual start switch 33 is operated, the polarization plane control circuit 36 performs the same operation as when changing the antenna, and clears the sweep voltage memory 36.37. ,on the other hand,
The flip-flop 20 and the sweep voltage generating circuit 19 perform the sweep operation and control that provide characteristics similar to those shown in FIG. 7, as in the case described above.

Effects of the Invention As described above, the present invention can achieve the following excellent effects.

(1) Eliminate terrestrial interference and remove the influence of adjacent signals,
Polarization plane can be set.

(2) When storing the voltage or pulse width for setting the plane of polarization, once the voltage or pulse width is stored correctly, the memory value can be used, so there is no need to narrow the IF band.

(3) The TI interference removal filter and the adjacent signal removal filter can be used together.

(4) Except when the polarization is fixed, the IF band can be selected from a sufficiently wide range, so there is no deterioration in image quality.

[Brief explanation of drawings]

Fig. 1 is a block diagram of a polarizer control circuit of a satellite broadcasting receiver according to an embodiment of the present invention, Fig. 2 is a characteristic diagram of the TI filter, and Fig. 3 is a block diagram of a receiving system of a satellite broadcasting receiver. , Fig. 4 is a block diagram of a conventional AGC voltage peak hold circuit, Figs. 5 and 6 are spectral characteristic diagrams for explaining the same operation, and Fig. 7 is the relationship between AGC voltage and polarization plane angle. FIG. 2... Polarizer, 16... AGO detection circuit, 17...
... Peak hold circuit, 18- Level comparator, 19 ... Swive voltage generation circuit, 20- Flip-flop, 21 ... 3-manual NOR gate, 22...
Pulse generator, 23...DC voltage supply circuit, 24
・・3-manpower OR gate, 26 ・・Protection resistance, 26
...Switching transistor, 27-...Relay, 29 T-filter, 35...Polarization plane control circuit, 36.37-...Sweep voltage memo Name of agent Patent attorney Toshio Nakao and one other person匡天5 promotion ward atsu faction] Q θNノ
() Fig. 5 47θ 42θ 51ρ J3t)
66; DMHz Fig. 7 Fig. 6

Claims (2)

[Claims] (1) A polarization plane control circuit configured to receive a plurality of television signals having two types of polarization planes sent from a satellite, and setting a polarizer that selects the polarization plane to an optimal state;
a state determination circuit for determining the state of the polarization plane for supplying a control signal indicating that the polarization plane of the polarizer is in the optimum state to the polarization plane control circuit; A polarizer control circuit for a satellite broadcasting receiver, characterized in that the output of a terrestrial interference removal filter inserted after a filter is input to the state determination circuit. (2) As the input to the video signal detector, use the output of the terrestrial interference removal filter only when the terrestrial interference is strong, and use the output of the bandpass filter without going through the terrestrial interference removal filter when the terrestrial interference is weak. Claim 1, characterized in that the device includes a switching circuit configured to be used as is, and the output of the terrestrial interference removal filter is used as an input to the state determination circuit regardless of the setting of the switching circuit. Polarizer control circuit for satellite broadcast receiver.