JP2006333134A - Antenna device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an antenna device adapted to a plurality of frequency bands maintaining a mounting property, stability in a change with time and electric-field resistant noise characteristics and, improving a receiving gain. <P>SOLUTION: In the antenna device, ferrite-bar antennas formed of winding coils 15 (15xa, 15xb, 15ya and 15yb) for medium waves and coils 16 (16xa, 16xb, 16ya and 16yb) for short waves at places separated from one another from ferrite bars are arranged in the orthogonal X-axis direction and Y-axis direction, respectively, while each ferrite-bar antenna is shielded electrostatically. In the antenna device, a tuning circuit for the medium waves is composed of the coils 15 for the medium waves fitted to each ferrite bar and a tuning capacitor 17, and the tuning circuit for short waves is composed of the coils 16 for short waves and a tuning capacitor 18 for short waves. In the antenna device, radio waves are extracted at a common output terminal through an impedance matching circuit by a circuit amplifying the signals of these tuning circuits and a low-pass filter LPF and a high-pass filter HPF. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an antenna device using a ferrite bar antenna and corresponding to a plurality of frequency bands.

  NAVTEX is operated internationally as a system that provides marine safety information such as navigation warnings for ships that travel mainly from the coast to about 300 nautical miles. In Japan, the Japan Coast Guard broadcasts an international NAVTEX 518 kHz broadcast and a Japanese NAVTEX 424 kHz broadcast.

  Meanwhile, IMO resolution MSC. According to 148 (77), it is required as a specification of an international NAVTEX receiver that a broadcast signal of either 490 kHz or 4.2095 MHz and a broadcast signal of 518 kHz can be received simultaneously. It is to be applied to duty ships constructed from the 1st.

  A shared active antenna of 518 kHz and 490 kHz has already been put into practical use, and an electric field type antenna device using a whip antenna and a magnetic field type antenna device using a ferrite bar have been put into practical use.

Patent Document 1 discloses an antenna using a ferrite bar. In order to receive a single radio wave (300 kHz band) broadcast from a beacon station (base station) of DGPS (Differential GPS), for example, the antenna shown in Patent Document 1 is 1 for each ferrite bar. A ferrite bar antenna in which two coils are wound is used. Further, the ferrite bar antenna is disposed between the two substrates, and the ferrite bar antenna is configured to shield the electric field.
JP 2000-312110 A

  In order to be able to receive the above-mentioned international NAVTEX broadcast even from a distance, the receiver should be able to receive the short wave band of 4.2095 MHz, and to support both the medium wave band and the short wave band. It is desirable to configure. In this case, (1) a format in which both the medium wave band and the short wave band are received by the electric field type antenna, (2) a format in which both the medium wave band and the short wave band are received by the magnetic field type antenna, and (3) the electric field type antenna One of the forms that combine magnetic field antennas is conceivable.

(1) Disadvantages of the type of reception by the electric field antenna-The electric field antenna requires grounding (earth), but if the mounting mast is non-metallic, a long ground wire is required.

  ・ If the grounding condition deteriorates due to secular change (such as rust caused by salt damage), the reception gain of the antenna will be extremely deteriorated. This is because the path of the antenna current is extremely reduced.

・ Horizontal directivity deteriorates due to electrostatic coupling with a conductor near the antenna. (For example, it is ideal that the antenna for NAVTEX has a non-directional horizontal plane directivity.)
・ Electric field components near the antenna (for example, radiation electric field noise inside and outside the ship) are received.

  Since the antenna itself cannot be shielded by electric field, the pulsed strong radio wave from the radar installed in the vicinity of the antenna is detected by the non-linearity of the tuning circuit / amplifier circuit, so that the original received signal is suppressed.

(2) Disadvantages of receiving with a magnetic antenna ・ When receiving signals in multiple frequency bands at the same time, different coils are wound around the ferrite bar for each frequency band. As a result, the effective Q value decreases, and the power (voltage) induced in the coil decreases. Further, the tuning frequency shifts for each of the first and second frequency bands due to the mutual induction.

  ・ The effective height of the antenna cannot be increased compared to the original electric field type.

(3) Disadvantages of combined form of electric field type antenna and magnetic field type antenna From the characteristics of frequency band, in the above example, it is most realized to receive 518 kHz and 490 kHz with magnetic field type antenna and 4.2095 MHz with electric field type antenna, respectively. It's easy to do. However, the frequency in the vicinity of 4.2095 MHz is based on a radio communication transmission wave (for example, 4065 to 4143 kHz as voice communication (SSB) and 4202.5 to 4207.0 kHz as narrowband printing telegram (NBDP)). Since it is suppressed, it is necessary to shorten the whip length of the whip antenna in consideration thereof. However, since the S / N ratio of the electric field antenna decreases by receiving the electric field component in the vicinity thereof (radiated electric field noise inside and outside the ship), in order to secure a predetermined S / N ratio, it is impossible to extremely shorten the whip length. Can not.

  Accordingly, an object of the present invention is to solve the above-mentioned problems, maintain mountability, aging stability, electric field noise resistance characteristics, increase reception gain, and simultaneously receive signals in a plurality of frequency bands. An object of the present invention is to provide an antenna device capable of performing

In order to solve the above problems, the antenna device of the present invention is configured as follows.
(1) A ferrite bar antenna formed by winding a first frequency band coil and a second frequency band coil at positions separated from each other with respect to the ferrite bar, and a first frequency band coil and a second frequency band Means for simultaneously receiving electromagnetic waves of a first frequency band and a second frequency band, each connected to a coil.

  (2) A ferrite bar antenna formed by winding a first frequency band coil and a second frequency band coil at positions separated from each other with respect to the ferrite bar, and a shield member for shielding an electric field around the ferrite bar antenna Is provided.

  (3) A conductor pattern for electric field shielding is formed on two substrates sandwiching the ferrite bar antenna, and a side substrate on which the electric field shielding conductor pattern is formed is disposed between the end portions of the two substrates. The electric field shield member is configured to cover the formed opening surface.

  (4) A first frequency band tuning amplifier circuit that forms a tuning circuit with the first frequency band coil and the first frequency band tuning capacitor and amplifies a tuning signal; the second frequency band coil; A second frequency band tuning amplifier circuit that forms a tuning circuit with the two frequency band tuning capacitors and amplifies the tuning signal, an output signal of the first frequency band tuning amplifier circuit, and the second frequency band tuning amplifier And an output sharing circuit for simultaneously outputting the output signal of the circuit to a common output terminal.

  (5) a first frequency band tuning circuit in which the ferrite bar antennas are disposed in the X-axis direction and the Y-axis direction orthogonal to each other, and includes a first frequency band coil of the ferrite bar antenna in the X-axis direction; A first frequency band phase synthesis circuit that synthesizes the first frequency band tuning circuit including the first frequency band coil of the ferrite bar antenna in the Y axis direction with a phase difference of 90 degrees, and a ferrite bar antenna in the X axis direction The second frequency band tuning circuit including the second frequency band coil and the second frequency band tuning circuit including the second frequency band coil of the ferrite bar antenna in the Y-axis direction are synthesized with a phase difference of 90 degrees. And a second frequency band phase synthesis circuit.

  (6) A plurality of the ferrite bar antennas are arranged in each of the X-axis direction and the Y-axis direction, and the first frequency band coils and the second frequency band coils are serially connected to each other in the same direction. Connecting.

  (1) Inductive coupling between the first frequency band coil and the second frequency band coil by winding the first frequency band coil and the second frequency band coil away from the ferrite bar. The degree of coupling becomes smaller. Therefore, a decrease in effective Q value is suppressed, a decrease in power (voltage) induced in both coils is suppressed, and a necessary gain can be ensured. In addition, for each of the first and second frequency bands, a shift in the tuning frequency due to the mutual induction is suppressed.

  (2) Since the electric field shield is provided around the ferrite bar antenna, it is not easily affected by the noise electric field regardless of the surrounding environment. Therefore, for example, the original received signal is not suppressed even by a pulsed strong radio wave from a radar installed in the vicinity of the antenna. In addition, by providing the electric field shield, a distributed capacitance is formed between the coil and the electric field shield, and the magnetic coupling between the first and second frequency band coils is relaxed. Even when receiving operations are performed simultaneously, good reception can be performed.

  (3) The vertical direction of the ferrite bar antenna is electric field shielded by two parallel substrates sandwiching the ferrite bar antenna, and the side surface direction of the ferrite bar antenna is electric field shielded by the side substrate. For this reason, electric field shielding is performed in all directions, and it is difficult to be affected by a noise electric field from any surrounding direction.

  (4) A first frequency band tuning amplifier circuit that forms a tuning circuit with the first frequency band coil and the first frequency band tuning capacitor and amplifies the tuning signal; a second frequency band coil; and a second frequency A tuning circuit for the second frequency band that amplifies the tuning signal while configuring a tuning circuit with the tuning capacitor for the band, an output signal of the tuning amplifier circuit for the first frequency band, and an output of the second frequency band tuning amplifier circuit By providing an output sharing circuit that simultaneously outputs signals to a common output terminal, signals in the first frequency band and signals in the second frequency band can be received at the same time. Can be received continuously and reliably.

  (5) A first frequency band tuning circuit including the first frequency band coil of the ferrite bar antenna in the X-axis direction, and a first frequency band tuning including the first frequency band coil of the ferrite bar antenna in the Y-axis direction. And a second frequency band tuning circuit including a second frequency band coil of the ferrite bar antenna in the X-axis direction, and a second frequency band of the ferrite bar antenna in the Y-axis direction. By combining the second frequency band tuning circuit including the coil for use with a 90-degree phase difference, good omnidirectionality can be obtained on the plane where the X axis and the Y axis intersect.

  (6) By arranging a plurality of ferrite bar antennas in the X-axis direction and the Y-axis direction, and connecting the first frequency band coils and the second frequency band coils in series with respect to the ferrite bar antenna in the same direction. You can earn gains. Moreover, the installation area (occupied area in the space) generated by arranging the ferrite bar antennas in the X-axis direction and the Y-axis direction which are originally orthogonal to each other can be increased even if the number of ferrite bar antennas in both directions is increased The gain can be improved without increasing the ratio series and without increasing the size of the entire apparatus.

An antenna device according to an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a diagram showing a connection relationship between a plurality of ferrite bar antennas and coils wound around them. The ferrite bars 7, 8, 9, and 10 are all formed by molding ferrite into a cylindrical shape. Here, these ferrite bars are arranged so that the ferrite bars 7 and 8 are both oriented in the X-axis direction and the ferrite bars 9 and 10 are both oriented in the Y-axis direction. However, here, the ferrite bars 7 and 8 facing the X-axis direction and the ferrite bars 9 and 10 facing the Y-axis direction are illustrated separately for explanation.

  One ferrite bar 7 facing the X-axis direction is provided with a medium wave coil 15xa and a short wave coil 16xa. The other ferrite bar 8 is provided with a medium wave coil 15xb and a short wave coil 16xb. Similarly, medium-wave coils 15ya and 15yb and short-wave coils 16ya and 16yb are provided on the ferrite bars 9 and 10 facing the Y-axis direction, respectively. With respect to these ferrite bars 7 to 10, the medium wave coils 15xa, 15xb, 15ya, 15yb and the short wave coils 16xa, 16xb, 16ya, 16yb are separated from each other by a predetermined distance (at a position distant from the ferrite bar). ) Arrange.

  Specifically, the ferrite bars 7 to 10 each have a cylindrical shape with a diameter of 9 mm and a length of 70 mm, and the medium-wave (490 kHz, 518 kHz) coil 15 is a coil with 100 turns and a short-wave (4.209 MHz). The coil 16 is a coil with 20 turns, and the interval between the medium wave coil 15 and the short wave coil 16 is 20 mm.

  As shown in the figure, two ferrite bars facing in the same direction are provided so that the magnetic field components of electromagnetic waves coming from the same direction are received and the induced voltage of each coil is added, that is, the outputs are strengthened. In addition, the winding direction of the coils for the same frequency band is determined and the coils are connected in series.

  That is, one end of the medium wave coil 15xa is grounded, the other end is connected to one end of the other medium wave coil 15xb, the other end is connected to the medium wave tuning capacitor 17x, and the medium wave coil shown later is connected. It is connected to output to the amplifier circuit. Also, one end of the short wave coil 16xa is grounded, the other end is connected to one end of the other short wave coil 16xb, the short wave tuning capacitor 18x is connected to the other end, and output to a short wave amplifier circuit described later. Connected to do. Similarly, one end of the medium wave coil 15ya is grounded, the other end is connected to one end of the other medium wave coil 15yb, and the medium wave tuning capacitor 17y is connected to the other end. It is connected to output to the amplifier circuit. Also, one end of the short wave coil 16ya is grounded, the other end is connected to one end of the other short wave coil 16yb, and the short wave tuning capacitor 18y is connected to the other end and output to the short wave amplifier circuit described later. Connected to do.

  Further, as shown in FIG. 1, the winding start direction of the coils connected in series is reversed (for example, the position of the winding start of the coils 15xa and 16xa of the ferrite bar 7 is on the right side in the figure, while The winding start positions of the coils 15xb and 16xb of the bar 8 are on the left side in the drawing), so that unnecessary inductive coupling does not occur between the coils of the ferrite bar antennas arranged in parallel.

  FIG. 2A is a circuit diagram of a tuning circuit using the ferrite bar antenna and the tuning capacitor for the medium wave coil. The same applies to the connection of the short-wave coil. Thus, the coils of the same frequency band of the ferrite bar antennas facing in the same direction are connected in series.

  The relationship between the output of the circuit including the ferrite bar antenna facing the X-axis direction and the output of the circuit including the ferrite bar antenna facing the Y-axis direction as shown in FIG. By adding and synthesizing with, non-directional characteristics in the horizontal plane direction are obtained comprehensively.

  In the example shown in FIGS. 1 and 2, two ferrite bar antennas in the X-axis direction and Y-axis direction are provided, but one ferrite bar antenna in each direction may be provided. Moreover, three or more may be sufficient.

  Here, mutual induction between the medium wave coil and the short wave coil provided on the same ferrite bar will be described with reference to FIG.

  Here, a ferrite bar antenna provided with a medium wave coil 15xa and a short wave coil 16xa is shown as a representative. The current i1 that flows through the medium wave coil 15xa at the time of medium wave resonance and the current i2 that flows through the short wave coil 16xa at the time of resonance of the short wave are respectively expressed as follows using symbols in the drawing.

i1 = E1 / r1
i2 = E2 / r2
However, E1 and E2 are induced voltages of the coils 15xa and 16xa, and r1 and r2 are resistance components of the coils 15xa and 16xa.

The induced voltage is expressed as follows.
EL1 = i1 × 2πfL1
EL2 = i2 × 2πfL2
Here, L1 and L2 are the inductances of the coils 15xa and 16xa.

And the induced electromotive force generated between the two coils is
Em1 = −Mdi2 (t) / dt
Em2 = −Mdi1 (t) / dt
It is represented by

  As a result of such an induced electromotive force, a shift occurs in the tuning frequency of the medium wave band and the tuning frequency of the short wave band, and the effective Q value of each decreases, so that the interval between the different coils in the two frequency bands is widened. . Thereby, the mutual induction M is reduced, and the induced electromotive force is suppressed.

  FIG. 4 is an equivalent circuit diagram in a state where an electric field shield (Faraday shield) is applied to the ferrite bar antenna in the state shown in FIG. The broken line in the figure represents the electric field shield. Distributed capacitances C1-1 to C1-n are generated between the electric field shield and the coils 15xa and 16xa. The resonance current of the coil is dispersed by these distributed capacities. For example, the current i1 flowing through the coil 15xa has a relationship of i1 = (total current of Δi1-1 to Δi1-n) + (coil current i1 ′). Similarly for the short wave coil 16xa, the current i2 flowing through the coil 16xa has a relationship of i2 = (total current of Δi2-1 to Δi2-n) + (coil current i2 ′).

  For example, if the number of turns of the medium wave coils 15xa and 15xb is 100 turns, and the combined inductance L1 of the medium wave coils 15xa and 15xb is 1480 μH, the tuning capacitance for tuning to a frequency of 500 kHz is 68 pF. If the distributed capacitance is about 53 pF, the target value of the capacitance C1 of the tuning capacitor 17x is 15 pF, so that the tuning capacitor 17x is a 30 pF trimmer capacitor.

  Further, if the number of turns of the short wave coils 16xa and 16xb is 20 turns and the combined inductance L2 of the short wave coils 16xa and 16xb is 74 μH, the tuning capacitance for tuning to the frequency of 4.2095 MHz is 19 pF. If the distributed capacitance is about 9 pF, the target value of the capacitance C2 of the tuning capacitor 18x is 10 pF, so that the tuning capacitor 18x is a 20 pF trimmer capacitor.

  Under these conditions, when the coupling coefficient between L1 and L2 is actually measured, it becomes 0.4 or less, and the influence of the two tuning circuits for medium wave and short wave can be reduced to the extent that there is no practical problem by the electric field shield. It was.

  As described above, by applying the electric field shield, the magnetic coupling between the coils for both the medium wave band and the short wave band is relaxed, and the medium wave and short wave electromagnetic waves can be received simultaneously better.

Other effects of the electric field shield are as follows.
(1) It becomes difficult to receive suppression due to reception of an electric field component in the vicinity of the antenna, and noise resistance in the ship is improved.

  (2) Prevent electrostatic coupling with conductors existing near the antenna (including the coil wiring pattern on the printed circuit board and the amplification circuit at the center of the printed circuit board, including the internal conductor and the mast near the antenna). The antenna balance (horizontal omnidirectionality) can be maintained.

  (3) It acts as a reflector for radar waves (3 GHz and 9 GHz radio waves) from the vicinity of the antenna, and the influence of radar waves can be prevented.

Next, a circuit configuration of the entire NAVTEX antenna apparatus using the antenna described above will be described with reference to FIG.
A tuning circuit is configured by connecting a tuning capacitor 17x for a medium wave in parallel to a series circuit of middle wave coils 15xa and 15xb for a ferrite bar antenna facing the X-axis, and the tuning signal is input to the gate of the FET Q1x at the first stage of the amplifier circuit. is doing. Further, a tuning circuit is configured by connecting a tuning capacitor 17y in parallel to a series circuit of middle-wave coils 15ya and 15yb for ferrite bar antennas facing in the Y-axis direction, and the tuning signal is applied to the gate of FET Q1y in the first stage of the amplifier circuit. You are typing.

  Similarly, a tuning circuit is configured by connecting a short-wave tuning capacitor 18x in parallel to a series circuit of short-wave coils 16xa and 16xb of a ferrite bar antenna facing the X axis direction, and the tuning signal is supplied to the gate of the FET Q2x at the first stage of the amplifier circuit. You are typing. Also, a tuning circuit is configured by connecting a medium-wave tuning capacitor 18y in parallel to a series circuit of short-wave coils 16ya and 16yb of the ferrite bar antenna facing the Y-axis direction, and the tuning signal is input to the gate of FET Q2y in the first stage of the amplifier circuit. is doing.

  The stagger tuning amplifier circuits SAx and SAy amplify the output signals of the FETs Q1x and O1y, respectively. Q is dumped so that this amplification frequency band includes a band of 490 kHz to 518 kHz. Single-tuned amplifier circuits MAx and MAy tune-amplify the outputs of FETs Q2x and Q2y, respectively. This tuning frequency is 4.2095 MHz.

  The synthesis amplifier circuit Am synthesizes and amplifies the output signals of the stagger tuning amplifier circuits SAx and SAy. The output of one stagger tuning amplifier circuit SAx is connected to the synthesis point via the capacitor Cm, and the other stagger tuning amplifier circuit SAy is connected. The output is connected to the synthesis point via a resistor Rm. Therefore, the output signals of the two stagger tuning amplifier circuits SAx and SAy are synthesized with a 90 ° phase difference.

  The synthesis amplifier circuit As synthesizes and amplifies the output signals of the single-tune amplifier circuits MAx and MAy. The output of one single-tune amplifier circuit MAx is connected to the synthesis point via the capacitor Cs, and the other single-tune amplifier circuit is connected. The output of MAy is connected to the synthesis point via a resistor Rs. Therefore, the output signals of the two single-tuned amplifier circuits MAx and MAy are synthesized with a 90 ° phase difference.

  The low-pass filter LPF passes the medium wave band (490 kHz, 518 kHz) and cuts the short wave band (4.2 MHz), and the high-pass filter HPF conversely cuts the medium wave band (490 kHz, 518 kHz) and cuts the short wave band (490 kHz, 518 kHz). 4.2 MHz). By using these two filters, an output sharing circuit for matching the output of the synthesis amplifier circuit Am for the medium wave band and the output of the synthesis amplifier circuit As for the short wave band to the coaxial output which is a common output unit is provided. It is composed. Therefore, the medium wave circuit and the short wave circuit can simultaneously output from a common output terminal (in this example, coaxial output) without interfering with each other.

  The output sharing circuit including the low-pass filter LPF and the high-pass filter HPF outputs a medium wave signal and a short wave signal simultaneously to the common output terminal at the same time, that is, without switching by a switch. Will be able to receive medium and short wave signals simultaneously.

  The circuits other than the ferrite bar antenna described above are configured on the circuit board and shielded by the shield case 24.

The effective height he of the ferrite bar antenna shown in FIG. 1 is expressed as follows.
he = Q · μe · (2πNA / λ)
μe = α ・ μm
However,
λ: Received wavelength A: Effective area N: Total number of turns of coil Q: Total Q value (effective Q value) of coil, tuning capacitor, and amplifier circuit (load amplifier circuit). Specifically, it is as follows.

(1) In the case of medium wave (500 kHz) When N = 200, r = 4.5 mm, Q = 10, and μe = 0.8 × μm = 23.2, the effective height he = 0.031 [m]. .

  However, μm is a toroidal value (= 290), and the effective magnetic permeability μe when the bar is formed is obtained by multiplying it by a coefficient of 0.8.

  When the output level to the main receiver is 6 dBμ, the input voltage of the amplifier is 6 dBμ-15 dB (gain of the entire amplifier circuit shown in FIG. 5) = − 9 dBμ.

Therefore, the practical electric field strength Emu is
Emu = -9 (dB [mu])-Ehe
= -9-(-30.2)
= 21.2 (dBμ / m)
It becomes.

  However, Ehe = 20 log (he).

(2) In the case of a short wave When N = 40, r = 4.5 mm, Q = 10, μe = 0.8 × μm = 23.2, the effective height he = 0.052 [m].

Therefore, the practical electric field strength Emu is
Emu = -9 (dB [mu])-Ehe
= -9-(-25.6)
= 16.6 (dBμ / m)
It becomes. However, Ehe = 20 log (he).

  Therefore, it can be understood that a practically sufficient gain can be obtained for both the medium wave and the short wave.

Next, the structure of the antenna device will be described with reference to FIGS.
FIG. 6 is an external perspective view of the main part of the antenna device. In FIG. 6, reference numeral 1 denotes an upper substrate, which is arranged in parallel to the hidden lower substrate in FIG. 6. Reference numerals 3, 4, 5, and 6 denote side substrates, which are arranged so as to cover the opening surfaces formed between the end portions formed by the parallel arrangement of the upper substrate 1 and the lower substrate. In FIG. 6, the conductor patterns provided on each substrate are not shown.

  9A and 9B are diagrams showing the configuration of the main part of the antenna device, wherein FIG. 9A is a top view and FIG. 9B is a right side view. FIG. 7 is an exploded perspective view showing a state where the side substrates 3 to 6 are removed from the state shown in FIG. 6 and the upper substrate 1 is removed.

  7 and 9, reference numeral 2 denotes a lower substrate, and four ferrite bar antennas indicated by 7, 8, 9, 10 on the upper surface thereof, and supports 11, 12, 13, 14 is attached. The four supports 11 to 14 are formed with holes into which the end portions of the ferrite bars 7 to 10 are inserted. Moreover, the boss | hub shown by b is formed in the upper surface of the support bodies 11-14. Similarly, bosses similar to the bosses on the upper surface are formed on the lower surfaces of these supports 11 to 14. FIG. 7 shows a state in which bosses projecting from the lower surfaces of the supports 11 to 14 are formed on the lower substrate 2 in a state where the ends of the ferrite bars 7 to 10 are inserted into the holes of the supports 11 to 14 respectively. The state inserted in one hole is shown.

  Holes are also formed in the four corners of the upper substrate 1, and these are assembled by covering the upper substrate 1 so that the bosses b on the upper surfaces of the supports 11 to 14 are inserted into these holes.

  As shown in FIG. 7, a rectangular ground electrode G is formed at the center of the upper and lower surfaces of the upper substrate 1 and the lower substrate 2. In addition, conductor patterns for electric field shielding (hereinafter referred to as “electric field shielding pattern”) indicated by s1, s2, s3, and s4 are formed in four directions. These conductor patterns are arranged by arranging a plurality of fine line conductors parallel to each side of the substrate, connecting the thin line conductors at a predetermined location (in this example, a center line portion which is symmetrical in the left and right direction) and ground electrodes. Connected to G. Further, these four electric field shield patterns s1 to s4 form patterns with a predetermined gap so that their end portions do not conduct with each other. Thus, by providing a thin wire conductor pattern parallel to the side of the substrate, an electric field component parallel to these conductor patterns does not pass through the conductor pattern and is shielded from the electric field. Magnetic field components parallel to these conductor patterns are transmitted without being shielded. Therefore, the electric field shield patterns s1 to s4 do not reduce the gain of the ferrite bar antenna. Such a shield with a conductor pattern for electric field shielding is also called a Faraday shield.

  A shield case 24 for shielding the circuit shown in FIG. 5 is provided at the center of the upper and lower surfaces of the lower substrate 2.

  The distributed capacitance of the coil generated by the electric field shield determines the line width, the line interval, and the coil interval of the electric field shield conductor pattern so as to fall within the range of 1/2 to 2/3 of the value of the tuning capacitor.

  Even if four ferrite bar antennas are arranged in this way, the installation area of the entire ferrite bar antenna is only slightly increased compared to the case where two orthogonal ferrite bar antennas are arranged, and without increasing the overall size, The gain of the antenna can be increased.

  FIG. 8 is a plan view representing one of the side substrates 3 to 6 shown in FIG. Electric field shield patterns indicated by s5 and s6 are formed on the side substrate. These conductor patterns are arranged with a plurality of fine wire conductors parallel to each side of the substrate, and the thin wire conductors are connected to each other at a predetermined location (in this example, a center line portion that is symmetric). The thin line conductors of these electric field shield patterns are formed in parallel to the ferrite bar direction of the ferrite bar antenna (direction perpendicular to the loop surface of the coil). By configuring the electric field shield pattern with the thin wire conductors in this way, electric field shielding can be performed without increasing the capacitance component between the circuit portions formed on the upper and lower substrates 1 and 2 and the electric field shield pattern. it can. Therefore, the side substrate does not adversely affect the circuit.

  Further, four holes indicated by h are formed in the side substrate. As shown in FIGS. 6 and 7, protrusions indicated by p are formed at the end portions of the upper substrate 1 and the lower substrate 2, and as shown in FIG. The four side substrates 3 to 6 are attached so as to be fitted into the holes h. A conductor land for soldering is provided around the hole h of the side substrate, and a ground electrode that is continuous with each electric field shield pattern is formed on the protruding portion p at the ends of the upper substrate 1 and the lower substrate 2. In the state where the protrusions p of the upper substrate 1 and the lower substrate 2 are inserted into the holes h of the side substrate, both are soldered. As a result, the electric field shield patterns s5 and s6 on the side substrate are electrically connected to the ground electrodes on the upper substrate 1 and the lower substrate 2, respectively. Also, the upper and lower two substrates 1 and 2 are joined and integrated by the four side substrates 3 to 6, and the rigidity is increased as a whole, and vibration resistance and impact resistance are improved.

  As shown in FIG. 8, since the electric field shield patterns s5 and s6 are electrically separated, the electric field shield pattern and ground electrode of the upper substrate 1 and the electric field shield pattern and ground electrode of the lower substrate 2 are used. And are electrically separated. Thereby, the loop by an electrode is not formed around a ferrite bar antenna, and the gain of a ferrite bar antenna is not reduced.

  6 constitutes the main part of the antenna device shown in FIG. 6. Since the support for supporting the ferrite bar antenna between the corners of the upper and lower substrates is made of conductive rubber, The four corners of the substrate are also field shielded with this support. Therefore, the electric field shield is provided around the ferrite bar antenna with almost no gap, and the shielding effect becomes more complete.

  In the example shown above, the four side substrates 3 to 6 are attached and further soldered so that the protrusions p of the upper substrate 1 and the lower substrate 2 are fitted into the holes h of the side substrate, Although the side substrates 3 to 6 are engaged with the upper and lower substrates 1 and 2, the upper and lower substrates 1 and 2 and the side substrates 3 to 6 are mechanically engaged only by fitting the protrusions p to the holes h. And may be electrically connected.

  FIG. 10 is a view showing a state in which the main part of the antenna device is mounted in a case, and the case portion is shown in cross section. In FIG. 10, reference numeral 23 denotes a case to which the main part of the antenna device is attached, and reference numeral 22 denotes a dome-shaped cover that covers the upper portion of the case 23. Screw portions are provided on the outer peripheral surface of the case 23 and the inner peripheral surface of the cover 22, and the cover 22 is screwed into the case 23 to ensure waterproofness. The upper surface of the case 23 is provided with a receiving portion for receiving a boss protruding from the lower surface of the ferrite bar antenna supports 11 to 14 shown in FIG. In addition, bosses for screwing the upper and lower substrates are formed.

  An electromagnetic wave transmitted from an international NAVTEX broadcasting station is radiated from a vertical antenna, and since its electric field component E is a longitudinal wave and a magnetic field component H is a transverse wave, this electromagnetic wave is an electric field composed of a thin line-shaped conductor pattern extending in the horizontal direction. It penetrates the shield pattern. On the other hand, a noise electric field whose electric field polarization plane is not perpendicular to the ground is suppressed because the horizontal component of the electric field is reflected by the electric field shielding conductor pattern.

11 to 13 show the measurement results of the horizontal plane directivity of the antenna device described above.
11 shows the characteristics at 518 kHz, FIG. 12 shows the characteristics at 490 kHz, and FIG. 13 shows the characteristics at 4.2095 MHz. All show the measurement results of three samples shown in (1) to (3). The horizontal plane directivity balance in the medium wave band (518 kHz, 490 kHz) is less than 2 dB (± 1 dB is the target), and it can be seen that all the antenna devices (1) to (3) satisfy this. . In addition, the horizontal plane directivity in the short wave band is a target of less than 3 dB (± 1.5 dB), and it can be seen that all of (1) to (3) satisfy this.

  In the embodiment, the antenna device corresponding to the two frequency bands of the medium wave band and the short wave band is shown. However, the “first frequency” and the “second frequency” of the present invention are classified into the medium wave band and the short wave band. The present invention is not limited, and can be similarly applied to the case where two frequency bands that are separated from each other to the extent that a single coil provided on the ferrite bar cannot be used in common.

It is a figure which shows the connection relation of a ferrite bar antenna and the coil provided in it. It is a figure which shows the connection relation of the coil provided in the ferrite bar antenna. It is a figure shown about the mutual induction electromotive force of the coil for medium waves and the coil for short waves provided in one ferrite bar antenna. It is a figure shown about the effect of an electric field shield. It is a figure which shows the circuit structure of the whole antenna apparatus. It is an external appearance perspective view of the principal part of an antenna device. It is a disassembled perspective view of the principal part. It is a top view of a side board. It is a figure which shows the structure of the principal part of an antenna apparatus. It is a figure which shows the structure of the whole antenna apparatus. It is a figure which shows the measurement result of horizontal plane directivity in 518kHz of an antenna apparatus. It is a figure which shows the measurement result of horizontal plane directivity in 490kHz of an antenna apparatus. It is a figure which shows the measurement result of horizontal-plane directivity in 4.2095MHz of an antenna apparatus.

Explanation of symbols

1-Upper substrate 2-Lower substrate 3-6-Side substrate 7-10-Ferrite bar 11-14-Support 15-Medium wave coil 16-Short wave coil 17-Medium wave tuning capacitor 18-Short wave tuning Capacitor 22-Cover 23-Case 24-Shield case G-Ground electrode s1-s6-Electric field shield pattern p-Protruding part h-Hole

Claims (6)

  A ferrite bar antenna formed by winding a first frequency band coil and a second frequency band coil at positions separated from each other with respect to the ferrite bar, and a first frequency band coil and a second frequency band coil, respectively. Means for simultaneously receiving the electromagnetic waves of the first frequency band and the second frequency band connected to each other.   A ferrite bar antenna formed by winding a first frequency band coil and a second frequency band coil at positions separated from each other with respect to the ferrite bar, and a shield member for electric field shielding around the ferrite bar antenna are provided. Antenna device.   A conductor pattern for electric field shielding is formed on the two substrates sandwiching the ferrite bar antenna, and a side substrate on which the electric field shielding conductor pattern is formed is formed between the end portions of the two substrates. The antenna device according to claim 2, wherein the electric field shield member is configured to cover an opening surface. A first frequency band tuning amplifier circuit that forms a tuning circuit with the first frequency band coil and the first frequency band tuning capacitor and amplifies a tuning signal;
A second frequency band tuning amplifier circuit that forms a tuning circuit with the second frequency band coil and the second frequency band tuning capacitor and amplifies a tuning signal;
An output sharing circuit for simultaneously outputting the output signal of the first frequency band tuning amplifier circuit and the output signal of the second frequency band tuning amplifier circuit to a common output terminal;
The antenna device according to claim 1, 2 or 3.   The first frequency band tuning circuit including the ferrite bar antennas disposed in directions of the X axis direction and the Y axis direction orthogonal to each other and including a first frequency band coil of the ferrite bar antenna in the X axis direction; A first frequency band phase synthesizing circuit that synthesizes the first frequency band tuning circuit including the first frequency band coil of the axial ferrite bar antenna with a phase difference of 90 degrees; and an X axis ferrite bar antenna The second frequency band tuning circuit including the second frequency band coil and the second frequency band tuning circuit including the second frequency band coil of the ferrite bar antenna in the Y-axis direction are synthesized with a phase difference of 90 degrees. The antenna device according to any one of claims 1 to 4, further comprising a second frequency band phase synthesis circuit.   A plurality of the ferrite bar antennas are arranged in each of the X axis direction and the Y axis direction, and the first frequency band coils and the second frequency band coils are connected in series with respect to the ferrite bar antenna in the same direction. The antenna device according to any one of claims 1 to 5.

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