JPH06224601A - Circuit for switching polarity of polarizer - Google Patents

Abstract

PURPOSE:To adopt the simple circuit configuration so as to eliminate the need for employing expensive components. CONSTITUTION:A differential amplifier section 3 and a constant current controller section 4 including a buffer 5 and a driver section 6 are operated entirely by bipolar power supply voltages +B, -B. The differential amplifier section 3 generates bipolar DC voltages in response to a voltage level of a skew signal SKEW and the drive of transistors(TRs) 24, 25 of complementary SEPP configuration is controlled by the voltages. Thus, the polarity of a current lowing to a polarizer coil is inverted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polariser polarity switching circuit, and more particularly to a polariser polarity switching circuit required for polarization mode switching.

[0002]

2. Description of the Related Art Polarity switching will be described with reference to FIGS. Circularly polarized radio waves are transmitted from broadcasting satellites (hereinafter simply referred to as BS satellites), and horizontally or vertically polarized radio waves are transmitted from communication satellites (hereinafter simply referred to as CS satellites). As shown in FIG.
Radio waves from the BS satellites or CS satellites are received by the parabolic antenna 51 and reflected, and then LNB (Low Nois
e Brockdown converter).

FIG. 3 shows an electromagnetic horn section 53 called a feed horn provided at the front end of the LNB 52 for CS satellite broadcasting, and a polarizer provided following the electromagnetic horn section 53. The so-called waveguide section 54 is shown. A resistor, a dielectric, and the like are provided inside the waveguide section 54, and a polarizer coil 55 is wound around the outside of the waveguide section 54. The terminals 55a and 55b are terminals for supplying a current to the polarizer coil 55.

The electric wave reflected by the parabolic antenna 51 is guided to the waveguide section 54 via the electromagnetic horn section 53. In the waveguide 54, unnecessary polarization components from the above-mentioned radio waves are generated by the resistor, the dielectric, and the polarizer coil 55.
, And only the desired polarization component is extracted and supplied to the subsequent converter.

In the waveguide portion 54, the electromagnetic horn portion 53
It has the function of separating the vertically polarized wave and the horizontally polarized wave of the signal introduced via the. The mainstream is called the magnetic polarizer and is of the type shown in FIG. A magnetic field is applied by the polarizer coil 55, and the direction of the magnetic field is changed by changing the direction of the current flowing through the polarizer coil 55.
Thereby, the vertically polarized wave and the horizontally polarized wave are selected.

A circuit of a current control circuit 61 for supplying a current to the above-mentioned polarizer coil 55 and switching the polarity is shown in FIG. The current control circuit 61 is a skew signal supplied from a microcomputer (not shown).
An amplifier 62 for controlling the current level of SKEW, a constant current controller unit 63 that incorporates a driver unit 64 to make the output a constant current, and a polarity switching circuit 65 that supplies a current to the above-mentioned polarizer coil 55 and switches the polarity. It consists of

In FIG. 4, the skew terminal of the microcomputer (not shown) is connected to the non-inverting input terminal of the operational amplifier 69 via the terminal 67 and the resistor 68. The output terminal of the operational amplifier 69 is connected to the non-inverting input terminal of the operational amplifier 73, and is fed back to the inverting input terminal via the resistors 70 and 71. The other end of the resistor 71 is grounded via the resistor 72. The operational amplifier 69 and the resistors 68, 70, 71 and 72 form an amplifier 62 as a non-inverting amplifier circuit.

As the operational amplifier 73, one for one power supply is used, and one power supply terminal of the operational amplifier 73 is
A power supply line 74 having a power supply voltage + B is connected. The other power supply terminal of the operational amplifier 73 is grounded.
The non-inverting input terminal of the operational amplifier 73 is the operational amplifier 6 described above.
9 is connected to one output terminal of the resistor 70, and the inverting input terminal is fed back with the potential of the emitter of the transistor 76 described later. Operational amplifier 73
The output terminal of is connected to the gate of the FET 75.

The operational amplifier 73, the FET 75, the transistor 76, the resistor 77 and the like constitute a constant current circuit. FE
One of the electrodes of T75, for example, the drain is connected to the power supply line 74 via the resistor 77. In addition, FET7
The source of 5 is connected to the base of the transistor 76. The collector of the transistor 76 is connected to the power supply line 74 via the resistor 77, the base is connected to the source of the FET 75, and the emitter is connected to the inverting input terminal of the operational amplifier 73 and the terminal 78d of the relay 78.

The FET 75 controls the temperature fluctuation of the transistor 76. That is, this control is realized by converting the power supply voltage + B into a current by the resistor 77, shunting the current into the FET 75 and the transistor 76, and then merging them again and outputting them from the emitter of the transistor 76. The transistor 76
The emitter potential of is fed back to the inverting input terminal of the operational amplifier 73, so that the emitter voltage is controlled to be a constant voltage.

The terminal 78a of the relay 78 is connected to the terminal 78g of the relay 78 and the connection terminal 79b of the polarizer coil 55. The terminal 78b of the relay 78 is connected to the emitter of the transistor 76. The terminal 78c of the relay 78 is connected to the terminal 78e of the relay 78 and the connection terminal 79a of the polarizer coil 55.

A coil 80 is connected between the terminals 78d and 78h of the relay 78. The terminal 78d is connected to the power supply line 74 on the cathode side of the diode 81. The terminal 78h is connected to the anode side of the diode 81 and the collector of the transistor 82.

The terminal 78g of the relay 78 is connected to the terminal 78a of the relay 78 and the connection terminal 79b of the polarizer coil 55. The terminal 78f of the relay 78 is grounded. The terminal 78e of the relay 78 is connected to the terminal 78c of the relay 78 and the connection terminal 79a of the polarizer coil 55.

The diode 81 is a diode for absorbing a back electromotive voltage, and the collector of a transistor 82 is connected to the anode side of the diode 81. The emitter of the transistor 82 is grounded, and the base side is connected to the terminal 85 via the resistor 84.

From the skew terminal (0.
The skew signal SKEW of 5 to 4.5 V is supplied. The skew signal SKEW is supplied to the non-inverting input terminal of the operational amplifier 69 via the resistor 68. The skew signal SKEW is amplified by the amplifier 62 with a predetermined amplification degree, and the output voltage is supplied to the non-inverting input terminal of the operational amplifier 73 of the constant current controller 63.

The operational amplifier 73 has a polarizer coil 55.
The control operation is performed to supply a constant current to the.
The operational amplifier 73 is fed back (-) with the output potential of the operational amplifier 69 supplied to the (+) input terminal.
It operates to eliminate the level difference with the emitter potential of the transistor 76 supplied to the input terminal.

The driver section 64, that is, the transistor 76.
A constant current is taken out from the emitter of, and the constant current is supplied to the terminal 78b of the relay 78. Further, the emitter voltage of the transistor 76 is supplied to the inverting input terminal of the operational amplifier 73.

On the other hand, a polarity switching signal is sent from a microcomputer (not shown) to the transistor 8 via the terminal 85 and the resistor 84.
2 base. When the polarity switching signal is at the high level, the base current flows through the resistor 84, and the base current flows from the base to the ground via the emitter.

At this time, since the current path from the collector of the transistor 82 to the ground is formed from the power supply line 74 through the terminal 78d of the relay 78, the coil 80b, and the terminal 78h, the coil 80 is excited.

Therefore, the relay 78 has terminals 78b and 78.
Since c, 78f and 78g are connected, the current supplied from the emitter of the transistor 76 is at terminals 78c and 79g.
It is supplied to the polarizer coil 55 via a. At the same time, the current from the polarizer coil 55 is applied to the terminal 79b,
It reaches the ground through 78g and 78f.

On the other hand, when the polarity switching signal is at the low level, the coil 80 is not excited, so that the relay 78 is connected to the terminals 78a and 78b, 78e and 78f. Therefore, the current supplied from the emitter of the transistor 76 is supplied to the polarizer coil 55 via the terminals 78b, 78a, 79b. At the same time, the current from the polarizer coil 55 reaches the ground via the terminals 79a, 78e and 78f.

In this way, the polarity switching signal supplied from the microcomputer controls the on / off of the transistor 82, thereby switching the connection state of the relay 78 and switching the polarity of the current supplied to the polarizer coil 55. ing. The diode 81 is a diode for absorbing a back electromotive voltage, and is for absorbing a back electromotive voltage generated when the coil 80 is switched between excitation and non-excitation.

[0023]

In the above-mentioned prior art, when the constant current is supplied to the polarizer coil 55 and the polarity of the constant current is switched, the skew signal SKEW and the polarity switching signal supplied from the microcomputer are used. However, there is a problem in that the circuit configuration is not simple.

When switching the polarity of the constant current,
Since a single power supply voltage is used, there is a problem that an expensive small relay 78 must be used.
Since the relay 78 occupies a large weight in terms of cost, there is a problem that it is difficult to significantly reduce the cost as long as the relay 78 is used.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a polarizer polarity switching circuit which has a simple circuit configuration and which does not require the use of expensive parts. To do.

[0026]

In order to solve the above-mentioned problems, the present invention was binarized in a polarizer polarity switching circuit for switching the polarity of a current flowing through a polarizer coil for switching the polarization of a broadcast signal. The step voltage is converted into a positive or negative polarity voltage and a complementary push-pull circuit means which operates based on the positive or negative polarity voltage.

[0027]

The step voltage of the binarized control signal is converted into a positive or negative polarity voltage. Then, the complementary push-pull circuit means is operated by the voltage. The current formed by the complementary push-pull circuit means flows through the polarizer coil. Therefore, the polarity of the current flowing through the polarizer coil is switched according to the polarity of the voltage.

[0028]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described below with reference to FIG. In the following one embodiment, only the circuit configuration for supplying a constant current to the polarizer coil is different, and the configurations and operations of the electromagnetic horn section, the waveguide section, the polarizer coil, etc. are the same as those of the prior art, and thus duplicated. The description will be omitted.

In the configuration of FIG. 1, a circuit of a current control circuit 1 for supplying a current to a polarizer coil (not shown) and switching the polarity is shown in FIG. The current control circuit 1 includes a differential amplifier section 3 for outputting a signal corresponding to the voltage level of a skew signal SKEW supplied from a microcomputer (not shown), a buffer 5 and a driver section 6, and makes the output a constant current. And a constant current controller unit 4 that operates.

In FIG. 1, a skew terminal of a microcomputer (not shown) is an operational amplifier 12 via a terminal 10 and a resistor 11.
Connected to the non-inverting input terminal of. The output terminal of the operational amplifier 12 is connected to the non-inverting input terminal of the operational amplifier 20, and is fed back to the non-inverting input terminal via the resistor 13. On the other hand, the power supply line 47 on the power supply voltage + B side is connected to one power supply terminal of the operational amplifier 12, and the power supply line 48 on the power supply voltage −B side is connected to the other power supply terminal of the operational amplifier 12.

The above-mentioned power supply line 47 includes resistors 14, 15
Is grounded through. The midpoint of the resistors 14 and 15 is connected to one end of the resistor 16. The other end of the resistor 16 is connected to the inverting input terminal of the operational amplifier 12 and is grounded via the resistor 17.

A power supply line 47 on the power supply voltage + B side is connected to one power supply terminal of the operational amplifier 20, and a power supply line 48 on the power supply voltage −B side is connected to the other power supply terminal of the operational amplifier 20. Has been done. The non-inverting input terminal of the operational amplifier 20 is connected to the output terminal of the above-described operational amplifier 12, and the inverting input terminal is fed back with the common emitter potential of the transistors 24 and 25 described later. The output terminal of the operational amplifier 20 is the buffer 5
Is connected to the non-inverting input terminal of the operational amplifier 21.

A power supply line 47 on the power supply voltage + B side is connected to one power supply terminal of the operational amplifier 21, and a power supply line 48 on the power supply voltage -B side is connected to the other power supply terminal of the operational amplifier 21. Has been done. The output terminal of the operational amplifier 21 is fed back to and connected to the inverting input terminal to form a voltage follower. The output terminal of the operational amplifier 21 is the diode 2
It is connected to the anode side of 2 and the cathode side of the diode 23.

The cathode side of the diode 22 is connected to the base of the transistor 24. The transistor 24
Is connected to the power supply line 47 on the power supply voltage + B side via the resistor 27, and the emitter of the transistor 24 is connected to the emitter of the transistor 25, the inverting input terminal of the operational amplifier 20, the connection terminal 27a to the polarizer coil, and the like. ing.

The anode side of the diode 23 is connected to the base of the transistor 25. The transistor 25
Is connected to the power supply line 48 on the power supply voltage −B side via the resistor 26, and the emitter of the transistor 25 is connected to the emitter of the transistor 24, the inverting input terminal of the operational amplifier 20, the connection terminal 27a to the polarizer coil, and the like. Has been done.

The transistors 24 and 25 have a complementary single-ended push-pull configuration, the common emitter potential is fed back to the inverting input terminal of the operational amplifier 20 described above, and the current from the common emitter of the transistors 24 and 25 is also supplied. Is the connection terminal 27
It is supplied to the polarizer coil via a. The connection terminal 27b to the polarizer coil is grounded.

By feeding back the common emitter potential described above to the inverting input terminal of the operational amplifier 20, the common emitter potential is controlled to be a constant voltage.

From the skew terminal of the microcomputer (not shown),
A / D converted and corresponds to the step of the microcomputer (0.5 ~
The skew signal SKEW of 4.5 V) is supplied. Here, when the center voltage (skew 0 level, DC 2.5 V) is set, the output of the differential amplifier unit 12, that is, the voltage level at the point A in the figure, becomes DC 0 V, so that the differential amplifier unit 13 outputs. A constant is selected.

As a result, skew (+100, DC + 4.5V)
In the case of, the potential at point A VA (= + 4.5V), skew (-10
0, DC + 0.5V), potential A at point A (= -4.5V)
Becomes The potential VA at the point A is the constant current controller unit 4
Is applied to the non-inverting input terminal of the operational amplifier 20.

The operational amplifier 20 performs a control operation for supplying a constant current to the polarizer coil. The operational amplifier 20 determines the level difference between the output potential of the differential amplifier section 12 supplied to the (+) input terminal and the common emitter potential of the transistors 24 and 25 which is fed back and supplied to the (−) input terminal. It works to solve it. The output potential of the operational amplifier 20 is supplied to the driver unit 6 via the buffer 5.

In the driver section 6, the potential supplied from the buffer 5 is applied to the bases of the transistors 24 and 25 via the diodes 22 and 23. The potential supplied from the buffer 5 is at a high level on the (+) side, for example (+4.
5) In the case of V, the transistor 24 is turned on and the current supplied from the emitter is supplied to the polarizer coil through the connection terminal 27a. At this time, the current supplied from the polarizer coil via the connection terminal 27b reaches the ground.

The emitter potential is fed back to the inverting input terminal of the operational amplifier 20 of the constant current controller section 4. As a result, a constant voltage is applied between the connection terminals 27a and 27b, and a constant current flows through the polarizer coil that is the load. The polarity of the polarizer coil in this state is the first polarity.

The potential supplied from the buffer 5 is (-)
At the high level on the side, for example, (-4.5) V, the transistor 25 is turned on. In this case, the current supplied from the polarizer coil through the connection terminal 27a flows from the emitter to the collector and the power supply voltage -B through the resistor 26. A current is supplied from the ground to the polarizer coil through the connection terminal 27b. Further, the emitter potential is fed back to the inverting input terminal of the operational amplifier 20 of the constant current controller unit 4.

As a result, a constant voltage is applied between the connection terminals 27a and 27b, and a constant current flows through the polarizer coil, which is a load. The polarity of the polarizer coil in this state is the second polarity, which is opposite to the first polarity described above. The impedance of the polarizer coil is 7
Since it is 5Ω, the current can be controlled up to ± 60mA.

In this embodiment, a constant current controller section 4 including a differential amplifier section 3, a buffer 5 and a driver section 6.
Are operated with positive and negative power source voltages + B and -B. Further, the differential amplifier section 3 forms a DC potential of positive and negative polarities according to the voltage level of the skew signal SKEW,
When the output of the operational amplifier 20 is set to the high level on the (+) side, the transistor 24 is turned on, and the current supplied from the emitter side is supplied to the polarizer coil via the connection terminal 27a. At this time, the connection terminal 27b is connected. The current supplied from the polarizer coil via the terminal reaches the ground. Further, when the output of the operational amplifier 20 is set to the high level on the (−) side, the transistor 25 is turned on, and the current supplied from the polarizer coil through the connection terminal 27a passes from the emitter through the collector and the resistor 26. Power supply voltage-B
And the current is supplied to the polarizer coil from the ground through the connection terminal 27b. As a result, the polarity of the current flowing through the polarizer coil is reversed.

Therefore, the circuit structure can be simplified. Also,
Since positive and negative polarities of the power supply voltage are used, it is not necessary to use an expensive small relay, and the cost can be reduced. Also, since the polarity can be switched only by the skew signal SKEW, one output port of the microcomputer can be saved.

[0047]

According to the present invention, there is an effect that the circuit configuration can be simplified. Further, there is an effect that cost reduction can be realized without using expensive parts such as a small relay.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention.

FIG. 2 is a prior art diagram showing a BS broadcast receiving system.

FIG. 3 is a prior art diagram showing an arrangement of polarizer coils.

FIG. 4 is a circuit diagram showing an example of a conventional technique.

[Explanation of symbols]

 1, 61 Current control circuit 3 Differential amplifier section 6 Driver section 55 Polarizer coil SKEW Skew signal

Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location H04N 7/20 7251-5C

Claims (1)

[Claims] 1. A polarizer polarity switching circuit for switching the polarity of a current flowing through a polarizer coil for switching the polarization of a broadcast signal, converting a binarized step voltage into a voltage of either positive or negative polarity. And a complementary push-pull circuit which operates on the basis of the positive and negative polarities of the voltage.