JP3621468B2 - Multi-frequency tuned loop antenna device - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a loop antenna apparatus mainly used in broadcasting / communication in a long and medium wave band, and more particularly to a multi-frequency tuning loop antenna apparatus capable of tuning to a plurality of frequencies.
[0002]
[Prior art]
In a conventional loop antenna apparatus used in the field of broadcasting and communication in the long and medium wave band, a loop antenna having a predetermined length is connected to a tuning circuit, and tuning is performed including the impedance of the loop antenna itself at a resonance frequency. A configuration is used. In such a configuration, since the circuit condition interferes due to the interaction between the loop antenna and the tuning circuit, the resonance frequency changes, and the frequency that can be tuned is limited. I can only receive waves. Even if it is possible to tune to multiple frequencies using a variable capacitance type capacitor with a wide variable range or a switching type circuit element, these are not intended for simultaneous reception of multiple frequencies. Absent.
[0003]
A device using a coaxial cable as a loop antenna is known in Japanese Patent Application Laid-Open No. 56-27509. However, these antennas are simply looped as a loop antenna and the inner conductor is used as an antenna. Thus, a shielded loop antenna that is balanced or unbalanced is configured to stabilize the impedance characteristic. Accordingly, as long as such a shielded loop antenna also has the conventional configuration as described above, only one or two waves can be received for reception.
[0004]
[Problems to be solved by the invention]
For this reason, when multi-frequency reception is performed simultaneously using a conventional loop antenna apparatus, it is necessary to install a plurality of similar antenna apparatuses according to a large number of frequencies and synthesize their outputs.
However, in order to install a plurality of antenna devices, there are problems such as requiring a wide installation place and complicated installation work, and a lot of expenses are involved in the manufacture and installation of antenna devices and synthesis devices. There is a problem that it takes.
[0005]
The present invention has been made paying attention to the above-mentioned problems, and a multi-frequency tuning loop antenna apparatus capable of performing stable multi-frequency tuning with a single loop antenna apparatus and reducing costs. The purpose is to provide.
[0006]
[Means for Solving the Problems]
For this reason, in the present invention, in a loop antenna device using a loop antenna having a relatively short circuit length with respect to the wavelength of the radio wave in the use band, loop antenna means in which a coaxial cable is formed in a loop shape with the circuit length, Ri formed by connecting a series resonant circuit having a resonant frequency in parallel a plurality, and a multi-frequency tuning means in the form of a plurality of two-terminal reactive circuit network tunable collectively frequency, the number of primary winding 2 A first high frequency transformer having a winding ratio larger than the number of secondary windings, the loop antenna means being connected to the primary winding, and the multi-frequency tuning means being connected to the secondary winding. The loop antenna means and the multi-frequency tuning means are coupled to each other via the first high-frequency transformer, thereby the loop antenna means with respect to the impedance of the multi-frequency tuning means. Impedance was equivalently a low impedance configuration.
[0007]
In addition, a second high frequency transformer is connected in series to a loop antenna circuit including the loop antenna means and the first high frequency transformer, and a tuning signal is taken out from an output terminal connected to the second high frequency transformer.
Alternatively, a tertiary winding is provided in the first high-frequency transformer, and a tuning signal is taken out from an output terminal connected to the tertiary winding.
[0008]
[Action]
In such a configuration, the antenna function of the loop antenna means constituted by the coaxial cable and the tuning function of the multi-frequency tuning means are electromagnetically coupled by the first high-frequency transformer. By properly selecting the electromagnetic coupling conditions, the influence of the circuit constants of the loop antenna means on the multi-frequency tuning means can be reduced, so even if the conditions of the loop antenna circuit change slightly, The tuning means functions as a multi-frequency collective tuning circuit that resonates at a plurality of frequencies while maintaining a high Q shape with little change in the tuning frequency. When the target wave having the set tuning frequency is received, an induced voltage is generated in the loop antenna means, and the current flowing through the series resonant circuit is maximized by the resonance action in the series resonant circuit located on the load side. Therefore, the loop antenna means and the multi-frequency tuning means have circuit constants suitable for respective circuit conditions by the first high-frequency transformer coupled by a winding ratio in which the number of primary windings is larger than the number of secondary windings. Equivalent impedances are presented to each other, and multi-frequency collective reception tuning is stably performed for the entire antenna device at a frequency substantially equal to the predetermined frequency set by the multi-frequency tuning means.
[0009]
Further, when the tuning output is taken out, the second high-frequency transformer is connected to the loop antenna circuit, and the tuning output is taken out from the output terminal via electromagnetic coupling, so that the multi-frequency tuning type loop antenna device and the external device are connected. Matching can be easily performed, the influence of the load-side circuit connected to the output terminal on the tuning function of the multi-frequency tuning loop antenna apparatus is reduced, and the target wave is matched with the circuit condition on the load side. The maximum tuning signal output power is extracted.
[0010]
Alternatively, the first high-frequency transformer is provided with a tertiary winding, loop antenna means and multi-frequency tuning means are connected to the primary and secondary windings, and both means are electromagnetically coupled, and further tuned. Even in the configuration in which the output terminal is connected to the tertiary winding to directly extract the output from the transformer, the multi-frequency collective tuning function can be satisfactorily extracted as described above.
[0011]
【Example】
Embodiments of the present invention will be described below with reference to the drawings.
In FIG. 1 showing the circuit configuration of the first embodiment of the present invention, a loop antenna 1 as a loop antenna means includes a hard coaxial cable 2 having weather resistance and antenna terminals 3 provided at both ends of the coaxial cable 2. 4. The coaxial cable 2 is formed in, for example, a triple loop shape, and has a form that does not impair the band characteristics with a relatively short circuit length with respect to the wavelength of the radio wave in the use band. That is, the stray capacitance and the parasitic capacitance are reduced so that the self-resonance frequency of the loop portion is out of the use band. The coaxial cable 2 is made of, for example, a relatively large-diameter coaxial cable used in CATV or the like (such as P3-412 manufactured by ComScope Co.) as a sheath conductor, and copper. Good practical performance was obtained by using a hard and light coaxial cable having a coated aluminum wire as a core wire conductor and having little secular change. The antenna terminals 3 and 4 include terminals 3A and 4A connected to the core wire of the coaxial cable 2 and terminals 3B and 4B connected to the outer conductor of the coaxial cable 2, respectively. In the circuit configuration of FIG. 1, the terminal 3A is connected to terminal 4B via the transformer T ₁ to be described later, by being connected to the terminals 4A the terminal 3B through the transformer T ₂ which will be described later, and the core wire of the coaxial cable 2 The jacket conductor is connected in series. That is, the connection method is similar to the so-called bifilar winding, in which the number of turns of the loop is two turns with one winding of the coaxial cable 2. Of course, the bifilar winding is not connected in series. If necessary, one turn of the coaxial cable 2 makes one turn as shown in FIGS. 2 (a) and 2 (b) (the core wire and the outer conductor are connected in parallel). It is also possible to use a connection method in which the impedance of the loop antenna circuit portion is further lowered (for example, by using only an outer conductor). These connection methods can be appropriately selected according to circuit conditions. The number of turns of the loop of the coaxial cable 2 can be applied to other than the above.
[0012]
The multi-frequency tuning circuit 5 which is a multi-frequency tuning means includes coils L ₁ , L ₂ . . . L _n , variable capacitors C ₁ , C ₂ . . . Constituted by a C _n. In order to tune with the target wave of n waves having different frequencies, the coil L ₁ and the variable capacitor C ₁ are connected in series, and the coils L ₂ . . . L _n and variable capacitors C ₂ . . . C _n are connected in series to form n series resonant circuits, and the series resonant circuits are connected in parallel. In each series resonance circuit, the constants of the coil and the capacitor are determined so that the resonance frequency matches the frequency of the target wave, and fine adjustment is performed by changing the capacitance value of each variable capacitor. Here, it is preferable that the so-called high-Q tuning circuit is configured by using a coil and a capacitor constituting the multi-frequency tuning circuit using components having a small resistance and loss.
[0013]
The transformer T ₁ of the a first high-frequency transformer, a primary winding and secondary winding are tightly coupled through a ferrite core, and a primary winding number N ₁ Number secondary winding A two-winding high-frequency transformer having a winding ratio larger than N ₂ is used. The terminal of the primary side winding of the transformer T ₁ is connected to the antenna terminals 3 A and 4 B, and the terminal of the secondary side winding is connected in parallel to each series resonance circuit of the multi-frequency tuning circuit 5. As for the number of turns N ₁ and N ₂ of the primary side and secondary side windings, a satisfactory result is obtained when the turn ratio is about N ₁ : N ₂ = 2: 1. Actually, in the experimental result in the long and medium wave frequency band, for example, the material of the ferrite core is a material having an operating frequency of 0.2 MHz or less and an initial permeability of about 3300, N ₁ = 20 turns, N ₂ = 10. As a turn, the loop antenna 1 and the multi-frequency tuning circuit 5 were combined to obtain a good practical performance. The material of the ferrite core and the number of turns N ₁ and N ₂ can be applied other than the above.
[0014]
The transformer T ₂ of the the second high-frequency transformer is connected by two winding high-frequency transformer for taking out an output from the loop antenna circuit including the loop antenna 1, the terminal of the primary winding, in this example the antenna terminal 3B, 4A and The terminal of the secondary winding is connected to the output terminal 6. Matching the impedance of the impedance and are not shown load output side of the loop antenna circuit via the transformer T ₂ are taken. Regarding the turns n ₁ and n ₂ of the primary side and secondary side windings, in the actual experimental results, the turn ratio is n ₁ : n ₂ = 1 in consideration of the impedance transformation ratio and band in the transformer T _2. By setting it to about 2-3, it was matched with the coaxial cable on the output side not shown, and good results were obtained. Of course, the turn ratio n ₁ : n ₂ is set appropriately depending on the circuit conditions on the load side. For example, in the case where the secondary side winding of the transformer T ₂ is immediately connected to the high impedance input amplifier as the load side, it is possible to increase n ₂ and obtain a large voltage gain. You can also.
[0015]
In the case of FIG. 2 (a), the transformer T ₂ are the primary winding of the transformer T ₂ in series as shown in FIG loop antenna circuit is connected. In the case of FIG. 2 (b), the terminal 3A of the core conductor of the coaxial cable, the transformer _{T 2} is connected to 4A.
Tuning box 7 the antenna terminals 3 and 4 and the output terminal 6 is fixed, the multi-frequency tuning circuit 5, a waterproof-type tuning box for housing the transformer T ₁ and transformer T _2.
[0016]
The structure of the antenna device using the above circuit is shown in FIG.
In the figure, a loop antenna 1 formed by bending a hard and lightweight coaxial cable 2 and having no special support frame is fixed to a stainless steel loop antenna mounting plate 8 with U bolts 9A. A tuning box 7 is fixed to the mounting plate 8, and a connector 11 is connected to an output terminal 6 fixed to the tuning box 7 via an output cable 10. Further, the attachment plate 8 is attached to a columnar object or the like not shown by a U bolt 9B. The tuning box 7, the mounting plate 8, and the U bolts 9A and 9B are not limited to the above, and other materials and shapes are applicable.
[0017]
Next, the operation of the first embodiment will be described.
First, due to the electromagnetic coupling of the transformer T _1, it will be described tuning function as an antenna of the device.
A primary side of the antenna function of the loop antenna 1, the multi-frequency tuning function of the tuning circuit 5 on the secondary side, influence each other through the electromagnetic coupling of the transformer T _1. At that time, the turns ratio of the transformer T ₁ in the condition, if constituting a transformer T ₁ at a proper number of turns, in the interaction with the loop antenna circuit and the multi-frequency tuning circuit 5 including the loop antenna 1, the primary side Even if the conditions of the loop antenna circuit change slightly, the multi-frequency tuning circuit 5 on the secondary side has a small change in the tuning frequency and multi-frequency collective tuning that resonates at a plurality of frequencies while maintaining a high Q shape. It functions stably as a circuit. When a target wave having a predetermined tuning frequency set by the multi-frequency tuning circuit 5 is received, an induced voltage is generated in the loop antenna 1, and the resonance action of the series resonance circuit located on the load side causes a resonance frequency at the tuning frequency. The reactance is zero and the flowing current is maximum.
[0018]
The stable tuning function of these characteristic multi-frequency tuning circuits will be further described in detail with reference to the drawings.
In FIG. 4 for explaining the tuning function of the series resonance type multi-frequency tuning circuit, FIG. 4 (a) shows two terminals in which the horizontal axis represents frequency f (or angular frequency ω) and the vertical axis represents reactance X. It is a graph of the frequency vs. reactance characteristic of the reactance network. Solid lines Xs ₁ , Xs ₂ , and Xs _{3 in} FIG. 4A are examples of characteristics of a two-terminal reactance network (that is, a series resonance type multi-frequency tuning circuit) formed by connecting three series resonance circuits in parallel. It is. Series resonance occurs at the frequency _{fs 1, fs 2, fs 3} reactance X becomes zero, when this is supplied a signal from the constant voltage source as in the circuit of FIG. _{4 (b), fs 1,} fs 2, fs _{In the} signal having the frequency of _3, the reactance of the two-terminal reactance network serving as a load becomes zero, and the maximum current flows.
[0019]
Here, as in the circuit of FIG. 4 (c), the circuit of the voltage source side, the impedance having a reactance characteristic shown by the solid line X _A shown in FIG. 4 (a) (i.e., the impedance having a loop antenna circuit Or the inductance of the loop winding) actually exists in series, the series resonance frequency is such that X _A + Xs ₁ = 0, X _A + Xs ₂ = 0, X _A + Xs ₃ = 0 The frequencies fs ₁ ′, fs ₂ ′, and fs ₃ ′ are shifted to.
[0020]
In such a case, it is desirable to make the impedance of the loop antenna circuit as low as possible, but there are certain restrictions. That is, in order to obtain as much power as possible in the loop antenna as much as possible, a method such as a large area loop winding or a large number of windings to increase the induced voltage is a practical loop antenna element. In the manufacture of. In this manner, inevitably increasing the value of inductance i.e. X _A. Therefore, as described above, the impedance (in fact, inductance of the loop winding) represented by X _A is viewed from the multi-frequency tuning circuit side of the object, to a value equivalent to a low impedance, through the transformer tightly coupled with impedance transformer action as a circuit configuration as shown in FIG. 4 (d), by combining the multi-frequency tuning circuit voltage source (loop antenna circuit) due to series resonant circuit, the influence degree of X _a It was made to reduce. In addition, it is necessary to be careful so that the impedance exhibited by the loop antenna circuit does not have complex characteristics (self-resonance characteristics) by reducing the stray capacitance and parasitic capacitance existing in the loop antenna circuit portion. .
[0021]
In this way, by adopting the circuit configuration shown in FIG. 4D, when the transformer turns ratio is 1: N, the impedance transformation ratio is 1: N ² , so that N 1 is 1 or less ( By making the number of primary side windings larger than the number of secondary side windings, it is possible to reduce the equivalent impedance when the primary side is viewed from the secondary side. For example, if the winding ratio between the number of primary windings and the number of secondary windings is 2: 1, the impedance transformation ratio is 4: 1 and the equivalent impedance is 1/4. The solid line impedance X _A shown is N ² times (for example, 1/4) as shown by the broken line, and is equivalently low, and the equivalent impedance is X _A ′. This acts on the series resonance circuit, and the series resonance frequency is the frequency at which X _A '+ Xs ₁ = 0, X _A ' + Xs ₂ = 0, X _A '+ Xs ₃ = 0, that is, fs ₁ , fs ₂ , frequency fs ₁ closer to _{fs 3 '', fs 2 '} ', become fs ₃ '', resulting in the degree of influence _{X a} is reduced.
[0022]
In the description using FIG. 4 described above, in order to explain reactance characteristics, the resistance of the circuit is omitted.
Next, the function of extracting the tuning output from this apparatus will be described.
When the output is taken out from the current flowing through the loop antenna circuit including the loop antenna 1, the multi-frequency tuning circuit 5 is coupled to the loop antenna circuit, and the internal impedance including the resistance of the loop antenna circuit including its equivalent impedance is included. The output must be extracted using a circuit matched to the above. By the structure for taking out an output from the output terminal 6 via the electromagnetic coupling of the transformer T ₂ which is configured with a compatible turns ratio circuit conditions for performing this alignment are connected in series to the loop antenna circuit, an output terminal 6 It is possible to reduce the influence of the load-side circuit connected to the tuned function of the multi-frequency tuned loop antenna device and to efficiently extract the tuning signal output in conformity with the load-side circuit conditions. In other words, when the output is transmitted by a coaxial cable, the circuit condition is usually low impedance, and when it is directly connected to the amplifier, the circuit condition is usually high impedance. Thus, it can be taken out efficiently.
[0023]
As described above, according to the first embodiment, the loop antenna circuit (primary circuit) and the multi-frequency tuning circuit 5 (secondary circuit) of the transformer T ₁ which is conditioned electromagnetic coupling comprising a loop antenna 1 Thus, the resonance frequency change caused by the mutual circuit conditions is made small, and the antenna device as a whole is stably and collectively changed to multi-frequency at a frequency substantially equal to a predetermined frequency set in each series resonance circuit. Tuning can be taken. Therefore, the number of antenna devices installed when receiving a plurality of target waves can be reduced. In addition, by using a rigid and lightweight coaxial cable to form a loop antenna with few support points, it can be assembled easily and inexpensively, and weather resistance is improved.
[0024]
Furthermore, the tuning signal by taking out from the output terminal 6 via the transformer T _2, it is possible to load side to reduce the effect on the antenna side, it is possible to take a more stable multi-frequency tuning.
Further, as shown in FIG. 1, the outer conductor and the core conductor of the coaxial cable 2 constituting the loop antenna 1 are connected in series to form a so-called bifilar winding connection method. Twice the number of turns, the induced voltage in the loop antenna 1 can be doubled, and the degree of freedom of configuration increases. Further, a loop antenna may be connected as shown in FIG. 2, and it is preferable to select an appropriate one depending on a use band and circuit conditions.
[0025]
Next, the circuit configuration of the second embodiment of the present invention will be described with reference to FIG. However, the same reference numerals are given to components having the same functions, and the description thereof is omitted.
In the figure, portions different from the first embodiment, in place of the transformer T ₁ and transformer T _2, using a 3-winding high-frequency transformer T. The primary side and secondary side windings of the transformer T are connected to the loop antenna 1 and the multi-frequency tuning circuit 5 as in the first embodiment, and the output terminal 6 is connected to the tertiary side winding. Further, the antenna terminals 3B and 4A are short-circuited, and the core wire of the coaxial cable 2 and the jacket conductor are connected in series. In addition, the connection method using the core conductor and the outer conductor in parallel as shown in FIGS. 2A and 2B, or using only the outer conductor, without using the bifilar winding connection as in this example. It is good also as a structure of 1 turn per winding. Similarly to the transformer T ₁ of the first embodiment, the transformer T has the same function of electromagnetically coupling the loop antenna 1 and the multi-frequency tuning circuit 5 as in the first embodiment in the number of turns N ₁ and N ₂ . there is, furthermore, is obtained by adding the tertiary winding in turns N ₃ for taking out directly tuned output from the transformer T. In an example of an experiment using a circuit as shown in FIG. 5, good results were obtained when the turns ratio of the transformer T was about N ₁ : N ₂ : N ₃ = 4: 2: 1, but it matched with the impedance on the load output side. The winding ratio is preferably determined by taking In the configuration using this transformer T, the multi-frequency tuning function of the present apparatus can be satisfactorily taken out as in the first embodiment, and in addition, the number of components is reduced, so that the size and cost can be reduced.
[0026]
However, the structure of the antenna device using the circuit of the second embodiment is the same as that of FIG. 3, and the operation thereof is the same as that of the first embodiment, so that the description thereof is omitted.
In the above description of the embodiment, the apparatus mainly used in the long and medium wave band has been described. However, in the present invention, the loop antenna has a relatively short circuit length compared to the wavelength even in the short wave and ultra short wave band. Needless to say, this is applicable.
[0027]
The above-described series resonant circuit type multi-frequency tuning circuit is a parallel resonant circuit type multi-frequency circuit in which a plurality of parallel resonant circuits having tuning characteristics that are dual in accordance with duality in electrical circuit theory are connected in series. A tuning circuit can also be applied. In this case, the winding ratio is such that the number of secondary windings of the first high-frequency transformer is larger than the number of primary windings. The basic configuration in this case is shown in FIG.
[0028]
Further, the transformer T ₁ and transformer T ₂ in the first embodiment, and the primary side, secondary side winding, or tertiary side winding of the transformer T in the second embodiment are shown in FIG. 1 and FIG. However, if it is not necessary to insulate electrostatically, each part of the winding is shared without being separated, that is, one winding The present invention can also be applied as a winding by a so-called autotransformer winding method in which a tap is pulled out from the middle or further wound to form another winding.
[0029]
In addition, in the description of the embodiment, the case where the target wave is received has been described. However, the configuration according to the present invention is not limited to the reception loop antenna device, but the transmission signal is input using the output terminal in the embodiment as an input terminal. Then, it can be applied as a loop antenna device for transmission or transmission / reception.
[0030]
【The invention's effect】
As described above, in the loop antenna apparatus mainly used for broadcasting / communication in the long and medium wave band, conventionally, only one or two waves of tuning can be stably extracted. By providing the frequency tuning means and electromagnetically coupling with the loop antenna means, a single loop antenna device can receive multiple frequencies in a stable manner, so that an extremely efficient loop antenna device can be provided. In addition, by configuring the loop antenna means using a coaxial cable, the present apparatus can be configured easily and inexpensively, and the weather resistance is improved.
[0031]
Further, by extracting the tuning signal from the output terminal via the second high-frequency transformer, the influence of the load side on the antenna side can be reduced, and multi-frequency tuning can be achieved more stably.
Alternatively, even if the first high-frequency transformer is provided with a tertiary winding and the tuning signal is extracted from this tertiary winding, the multi-frequency tuning output can be similarly satisfactorily taken out. Since the number of parts is reduced, downsizing and cost reduction are possible.
[Brief description of the drawings]
FIG. 1 shows a circuit configuration of a first embodiment of the present invention (1)
FIG. 2 is a diagram showing a circuit configuration of the embodiment (2).
FIG. 3 is a diagram showing the structure of the embodiment of the present invention. FIG. 4 is a diagram for explaining a tuning function of the multi-frequency tuning circuit of the embodiment of the same. FIG. 5 is a diagram showing a circuit configuration of the second embodiment of the invention. FIG. 6 is a diagram showing an example of a dual circuit configuration with the circuit configuration of the present invention.
1 Loop antenna 2 Coaxial cable 5 Multi-frequency tuning circuit 6 Output terminals T ₁ , T ₂ , T transformer

Claims (3)

In a loop antenna device using a loop antenna having a relatively short circulation length with respect to the wavelength of the radio wave of the band used,
Loop antenna means in which a coaxial cable is formed in a loop shape with the loop length;
Ri formed by connecting a series resonant circuit having a predetermined resonant frequency to parallel a plurality, and a multi-frequency tuning means in the form of a plurality of two-terminal reactive circuit network tunable collectively frequency,
A first high-frequency transformer having a winding ratio in which the number of primary windings is greater than the number of secondary windings;
The loop antenna means is connected to the primary winding, the multi-frequency tuning means is connected to the secondary winding, and the loop antenna means and the multi-frequency tuning means are connected via the first high-frequency transformer. Is combined with the impedance of the multi-frequency tuning means so that the impedance of the loop antenna means is equivalently low. The second high-frequency transformer is connected in series to a loop antenna circuit including the loop antenna means and the first high-frequency transformer, and a tuning signal is extracted from an output terminal connected to the second high-frequency transformer. The multi-frequency tuning loop antenna device according to 1. 2. A multi-frequency tuned loop antenna according to claim 1, wherein a tertiary winding is provided in the first high-frequency transformer, and a tuning signal is extracted from an output terminal connected to the tertiary winding. apparatus.

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