JP2004072445A - Antenna feeder circuit for medium wave broadcasting - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an antenna feeder circuit for medium wave broadcasting which has a simple configuration, facilitates impedance matching, and has excellent lightning resistance. <P>SOLUTION: A high frequency transformer having the lightning resistance improved is connected to an impedance matching circuit connected between a broadcaster for medium wave broadcasting and an antenna, and the primary coil of the high frequency transformer is connected to the impedance matching circuit. The secondary coil of the high frequency transformer is connected to the antenna via a series coil for canceling the imaginary term component of antenna impedance, and impedance conversion is efficiently performed by the high frequency transformer, and a ball gap is inserted to an antenna base part against lightning surge exceeding expectations. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a feeder circuit for an antenna of a medium-wave broadcasting device, and more particularly to a feeder circuit for a medium-wave broadcast antenna, which is easy to adjust and match, has little deterioration in SWR in a transmission band, and is effective in protecting against lightning surge. is there.
[0002]
[Prior art]
FIG. 1 shows an example of a medium-wave broadcasting antenna feed circuit having a lightning-resistant function according to the prior art. In the figure, 1 is an antenna, 2 is a ball gap connected as an arrester to protect the broadcaster by short-circuiting the excessive voltage induced at the time of lightning to ground, and 3 is to prevent an excessive voltage from being induced in the antenna 1. A lightning-resistant coil for grounding DC and flowing a low-frequency component including a DC component of lightning energy (lightning surge) to the ground; 4 is a DC for preventing a DC component contained in lightning surge from being transferred to a broadcasting machine. It is a cut capacitor. The ball gap 2, the lightning protection coil 3 and the DC cut capacitor 4 constitute a lightning protection circuit. Reference numeral 5 denotes a matching coil for converting the antenna impedance into a value within a range that can be adjusted by the impedance matching circuit 6. The impedance matching circuit 6 matches the antenna impedance with the output impedance of the medium-wave broadcasting broadcast 7. It is a circuit of a coil and a capacitor. As described above, in the related art, a method of matching the output impedance of the broadcaster to the antenna impedance by using a series-parallel coil and a capacitor frequently has been used.
[0003]
[Problems to be solved by the invention]
In the matching circuit manufactured by the conventional technology, the lightning surge may destroy the DC cut capacitor, the lightning-resistant coil and the matching coil, and the broadcasting may be interrupted. Therefore, it is necessary to provide each component with a sufficient withstand voltage characteristic, which has been a factor of increasing the size and complexity of the circuit.
[0004]
The antenna impedance viewed from the feed side is generally represented by Z = R + jX, where R is the radiation resistance of the antenna, X is the radiation reactance. Since the real term is low and the imaginary term of the radiance reactance tends to be high, in this case, the matching condition is very critical in the impedance matching method according to the related art, and it may be difficult to adjust within a short broadcast pause time. Was. In particular, small-scale radio stations installed on the top of a mountain cannot increase the height of the terrestrial antenna and the area of the earth network cannot be reduced, so the antenna must be grounded or folded back. Absent. In such an antenna, the reactance component often has a large negative value in a high frequency band for a medium wave.
[0005]
Furthermore, when the real term of the antenna impedance is low, a large current needs to flow to supply the required power to the antenna. However, since the imaginary term of the antenna is high, a high voltage is applied to the antenna base and the feed circuit. In order to cause such a problem, it is necessary to use a component having a very high withstand voltage, so that the matching device has been increased in size.
[0006]
Also, when the real term of the antenna impedance is low, the SWR in the transmission band is degraded each time it passes through each element of the matching circuit, and the protection circuit of the broadcaster operates by the high frequency component of the broadcaster input program. Broadcasts were sometimes interrupted.
Therefore, an object of the present invention is to provide a medium-wave broadcasting antenna having a small number of elements used in a matching circuit, a simple configuration, easy adjustment of impedance matching, and excellent lightning resistance with extremely little deterioration of SWR in a transmission band. An object of the present invention is to provide a power supply circuit.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, an invention according to claim 1 of the present invention is a medium wave broadcasting antenna feed circuit connected between an antenna and an impedance matching circuit for a medium wave broadcaster, wherein the impedance matching circuit A high-frequency transformer having a primary coil connected to a circuit and a series circuit connected to a secondary coil of the high-frequency transformer for canceling a reactance component of antenna impedance are provided.
[0008]
The invention according to claim 2 is the invention according to claim 1, wherein the high-frequency transformer has a primary coil wound around a ring-type ferrite core evenly so that a leakage magnetic flux is minimized, and a secondary coil is formed of a ring. It is characterized by a lightning-resistant structure penetrating the center.
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.
[0010]
FIG. 2 is a block diagram showing an embodiment of an antenna feed circuit for medium-wave broadcasting according to the present invention, where 10 is an antenna, and 11 is inserted in anticipation of safety in order to discharge a lightning surge exceeding expected. The ball gap 12 is a series coil connected in series to the antenna 10 to cancel the imaginary component of the antenna impedance which generally shows a high tendency, and 13 is an impedance value within a range where the antenna impedance can be adjusted by the matching circuit 14. This is a matching high-frequency transformer for conversion, and the series coil 12 and the high-frequency transformer 13 constitute a medium-wave band transformer power supply unit. Reference numeral 14 denotes a broadcaster for medium-wave broadcasting, and reference numeral 15 denotes an impedance matching circuit for finely adjusting the antenna impedance to the output impedance of the broadcaster 14.
[0011]
According to the present invention, unlike the matching method using the conventional series-parallel reactance, first, the imaginary term component of the antenna 10 is canceled by the series coil 12, and the antenna impedance is adjusted by the high frequency transformer 13 within the range that can be adjusted by the matching circuit 15. , And then the impedance is matched by the matching circuit 15. The high-frequency transformer 13 sets the ratio of the number of turns of the primary coil connected to the matching circuit 15 to the number of turns of the secondary coil connected to the antenna 10 via the series coil 12 as n: 1, and It significantly reduces current and voltage relative to the secondary. As a result, the voltage and current ratings of the components used in the impedance matching circuit 15 can be kept low. In addition, since the impedance is converted to an optimum value by the high-frequency transformer 13, deterioration of the SWR in the transmission band is minimized, and a simple configuration of the matching circuit is sufficient.
[0012]
As shown in FIG. 3, the high-frequency transformer 13 minimizes the transmission loss of the transformer and uniformly winds the primary coil 21 around the ring-shaped ferrite core 20 having good high-frequency characteristics according to the required number of turns. By turning, the secondary coil 22 has a structure penetrating the center of the ring of the ferrite core 20, and the primary coil 21 and the secondary coil 22 are sufficiently separated from each other to improve the high voltage withstand voltage.
The high-frequency transformer is not limited to the above-mentioned cultivation, but may be used that has good transmission characteristics in the medium-wave frequency band, a large attenuation in other frequency bands, and a large withstand voltage and withstand current. is there.
[0013]
According to the antenna feed circuit according to the present invention, the antenna 10 can be grounded DC by the series coil 12 and the secondary coil of the high-frequency transformer 13 to fix the DC potential. The coil can be omitted. Since the current capacity of the secondary coil of the high-frequency transformer for impedance conversion 13 is very large due to the structure shown in FIG. 3, in order to maintain sufficient strength against a large current due to a lightning surge. It is sufficient that only the coil 12 inserted in series with the antenna 10 has a strong structure.
[0014]
【The invention's effect】
According to the present invention, since the antenna is DC grounded and the DC potential is fixed, the lightning protection coil required in the conventional circuit becomes unnecessary. In addition, since the current capacity of the secondary coil of the high-frequency transformer for impedance conversion is extremely large, it is only necessary to make the series coil for canceling the imaginary component of the imaginary component of the antenna impedance connected to this secondary coil a strong structure. Sufficient strength against a large current caused by the Further, even with a high voltage due to a lightning surge, a sufficient distance can be secured between the primary and secondary coils of the high-frequency transformer, so that sufficient withstand voltage characteristics can be secured.
[0015]
Further, in the past, when power was supplied to an antenna having a low effective height, it was very difficult to perform matching adjustment, and there was a problem that a large current and a high voltage generated a circuit element, and the like. Step up the antenna impedance to the optimum value with a series coil connected to the secondary side of the transformer.Since the configuration is simple, and the current and voltage on the primary side of the transformer are significantly reduced, the danger of discharge in the matching circuit is significantly improved. In addition, since the voltage and current ratings of the components used can be low, the entire power supply circuit can be extremely reduced in size.
[0016]
Conventionally, when power is supplied to an antenna with a low real number term, the matching circuit degrades the SWR within the transmission band, and the protection circuit of the broadcaster operates due to the high-frequency component of the broadcaster input program, and the broadcast is interrupted. there was, but according to the present invention, since the impedance transformer is converted in proportion to the turns ratio n ^2, deterioration of the transmission band SWR is significantly improved. Further, even in the matching circuit for fine-tuning the impedance, the impedance is converted to the optimum value, so that the deterioration of the SWR in the transmission band is minimized. As a result, the stability of the broadcast is significantly improved.
[Brief description of the drawings]
FIG. 1 is a configuration diagram showing an example of a conventional medium-wave broadcasting antenna feeding circuit.
FIG. 2 is a configuration diagram showing one embodiment of a medium-wave broadcasting antenna feed circuit according to the present invention.
FIG. 3 is a configuration diagram of a high-frequency transformer.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Antenna 11 Ball gap 12 Series coil 13 High frequency transformer 14 Broadcasting machine 15 Impedance matching circuit 20 Ring type ferrite core 21 Primary coil 22 Secondary coil

Claims (2)

A medium-wave broadcasting antenna feeding circuit connected between an impedance matching circuit and an antenna for a medium-wave broadcasting machine,
A high-frequency transformer having a primary coil connected to the impedance matching circuit,
A series circuit connected to a secondary coil of the high-frequency transformer and for canceling a reactance component of an antenna impedance;
A medium-wave broadcasting antenna feeding circuit, comprising: 2. The medium wave according to claim 1, wherein the high-frequency transformer has a lightning-resistant structure in which a primary coil is evenly wound around a ring-type ferrite core and a secondary coil passes through the center of the ring. Broadcast antenna feed circuit.

Images