JP2011193133A - Antenna device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain an antenna device which sufficiently reduces an RCS, in consideration of an influence of a reflected wave from a structure itself such as an earth conductor or an antenna element. <P>SOLUTION: An antenna device has: an earth conductor 2; a dipole antenna element 1 arranged separated from the earth conductor 2 by a predetermined distance to receive an electromagnetic wave from the outside as a reception signal, and emitting an inputted reflected signal as the electromagnetic wave; and a power reflection device 6 connected to the dipole antenna element 1 to adjust one of an amplitude and a phase of the reception signal so as to cancel the electromagnetic wave from the outside reflected in the earth conductor 2 and the dipole antenna element 1 themselves, and reflect the reception signal on the antenna element as the reflected signal. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an antenna device applied to an array antenna used for applications such as radar.

  Array antennas in which a plurality of antenna elements are arranged are used in a wide range of fields, and a desired beam can be formed by adjusting the amplitude and phase of a signal radiated as an electromagnetic wave from each antenna element. In addition, in an antenna device applied to an array antenna used for applications such as radar, it is necessary to reduce a radar reflection area (RCS: Radar Cross Section) so that its position cannot be detected.

Therefore, in the conventional antenna device, it has been proposed to reduce the RCS by absorbing the energy of the electromagnetic wave received by the antenna element (see, for example, Patent Document 1).
Hereinafter, the conventional antenna device disclosed in Patent Document 1 will be described in detail with reference to FIG.

FIG. 12 is a block diagram showing a conventional antenna device.
In FIG. 12, the antenna device includes an antenna element 51, a first switch 52, a transmission circuit 53, a second switch 54, an amplifier 55, a reception circuit 56, a phase shifter 57, and a variable attenuator 58.

  The first switch 52 is a switch that switches between the transmission circuit 53 and the reception circuit 56. The first switch 52 is switched to a terminal on the transmission circuit 53 side when radiating (transmitting) electromagnetic waves from the antenna element 51, and when receiving electromagnetic waves from the outside with the antenna element 51, and when neither transmitting nor receiving is performed, The terminal is switched to the terminal on the receiving circuit 56 side.

  The second switch 54 is a switch for switching between the reception circuit 56 and the conjugate matching element 59 including the phase shifter 57 and the variable attenuator 58. The second switch 54 is switched to a terminal on the receiving circuit 56 side when the antenna element 51 receives external electromagnetic waves, and is switched to a terminal on the conjugate matching element 59 side when neither transmission nor reception is performed.

  Here, the conjugate matching element 59 is adjusted to match the impedance at the feeding point of the antenna element 51. Therefore, in a state where the antenna element 51 is connected to the conjugate matching element 59, the energy of the electromagnetic wave received by the antenna element 51 is absorbed by the conjugate matching element 59 under non-reflecting conditions. Therefore, the RCS of the antenna device can be reduced.

JP 2009-109333 A

However, the prior art has the following problems.
In a general antenna device, in order to radiate electromagnetic waves in a specific direction, a ground conductor is disposed behind the antenna element, so it is necessary to consider the influence of reflected waves from the ground conductor. In addition, since electromagnetic waves are reflected even in the structure of the antenna element, it is necessary to consider the influence of the reflected wave from the antenna element itself.

  In the conventional antenna device, the energy of the electromagnetic wave received by the antenna element is absorbed by the conjugate matching element that matches the impedance at the feeding point of the antenna element without considering the influence of the reflected wave from the ground conductor or the antenna element itself. Therefore, there is a problem that RCS cannot be sufficiently reduced.

  The present invention has been made to solve the above-described problems, and an antenna device capable of sufficiently reducing RCS is obtained in consideration of the influence of reflected waves from the ground conductor and the antenna element itself. For the purpose.

  An antenna device according to the present invention includes a ground conductor, an antenna element that is arranged at a predetermined distance from the ground conductor, receives an electromagnetic wave from the outside as a received signal, and radiates an input reflected signal as an electromagnetic wave, and an antenna Reflecting means connected to the element and adjusting at least one of the amplitude and phase of the received signal so as to cancel the external electromagnetic wave reflected by the ground conductor and the antenna element itself, and reflecting the reflected signal to the antenna element as a reflected signal Is.

According to the antenna device of the present invention, the reflecting means adjusts at least one of the amplitude and the phase of the received signal so as to cancel the electromagnetic wave from the outside reflected by the ground conductor and the antenna element itself, and the antenna element is used as the reflected signal. The antenna element radiates the input reflected signal as an electromagnetic wave.
Thereby, the electromagnetic wave from the outside reflected by the ground conductor and the antenna element itself is canceled by the electromagnetic wave radiated from the antenna element according to the reflected signal.
Therefore, an antenna device that can sufficiently reduce RCS can be obtained in consideration of the influence of reflected waves from the ground conductor and the antenna element itself.

It is a block diagram which shows the antenna apparatus which concerns on Embodiment 1 of this invention. (A)-(f) is explanatory drawing which shows the specific structural example of the power reflection apparatus of the antenna apparatus which concerns on Embodiment 1 of this invention. It is explanatory drawing for demonstrating the principle by which RCS is reduced by the antenna device which concerns on Embodiment 1 of this invention. It is explanatory drawing for demonstrating the principle by which RCS is reduced by the antenna device which concerns on Embodiment 1 of this invention. It is explanatory drawing for demonstrating the principle by which RCS is reduced by the antenna device which concerns on Embodiment 1 of this invention. It is a block diagram which shows the antenna apparatus which concerns on Embodiment 2 of this invention. It is a block diagram which shows the antenna apparatus which concerns on Embodiment 3 of this invention. It is a block diagram which shows the antenna apparatus which concerns on Embodiment 4 of this invention. It is a block diagram which shows the antenna apparatus which concerns on Embodiment 5 of this invention. It is a block diagram which shows the antenna apparatus which concerns on Embodiment 6 of this invention. It is a block diagram which shows the antenna apparatus which concerns on Embodiment 7 of this invention. It is a block diagram which shows the conventional antenna apparatus.

  Hereinafter, preferred embodiments of the antenna device according to the present invention will be described with reference to the drawings. In the drawings, the same or corresponding parts will be described with the same reference numerals.

Embodiment 1 FIG.
1 is a block diagram showing an antenna apparatus according to Embodiment 1 of the present invention. In FIG. 1, this antenna device includes a dipole antenna element 1, a ground conductor 2, a switch 3, an amplifier 4, a receiving circuit 5, and a power reflecting device 6 (reflecting means).

The dipole antenna element 1 receives an electromagnetic wave from the outside and outputs it as a reception signal to the switch 3 at the subsequent stage. The dipole antenna element 1 radiates a reflected signal (described later) from the power reflecting device 6 as an electromagnetic wave.
The ground conductor 2 is disposed at a distance of approximately λ / 4 from the dipole antenna element 1. Here, λ indicates a wavelength at an operating frequency (for example, frequency f1) in which the antenna device is used.

The switch 3 switches the connection destination of the dipole antenna element 1 to the receiving circuit 5 side or the power reflecting device 6 side.
The amplifier 4 amplifies the reception signal from the dipole antenna element 1 and outputs the amplified signal to the reception circuit 5.
The reception circuit 5 performs reception processing on the reception signal from the dipole antenna element 1 amplified by the amplifier 4.

  The power reflecting device 6 adjusts at least one of the amplitude and phase of the received signal from the dipole antenna element 1 so as to cancel the electromagnetic wave from the outside reflected by the ground conductor 2 and the dipole antenna element 1 itself, and switches it as a reflected signal. 3 is reflected by the dipole antenna element 1.

Hereinafter, a specific configuration example of the power reflecting device 6 will be described with reference to FIG.
FIG. 2A shows a power reflection device 6 using the variable resistance element 7. By changing the resistance value of the variable resistance element 7, the amplitude and phase of the reflected signal reflected by the dipole antenna element 1 can be adjusted.
FIG. 2B shows a power reflection device 6 using the variable capacitance element 8. By changing the capacitance value of the variable capacitance element 8, the phase of the reflected signal reflected by the dipole antenna element 1 can be mainly adjusted.

FIG. 2 (c) shows the power reflection device 6 using the variable induction element 9. By changing the induction value of the variable induction element 9, the phase of the reflected signal reflected by the dipole antenna element 1 can be mainly adjusted.
FIG. 2D shows a power reflection device 6 in which the variable attenuator 10 and the phase shifter 11 are combined. The variable attenuator 10 can adjust the amplitude of the reflected signal reflected by the dipole antenna element 1, and the phase shifter 11 can adjust the phase of the reflected signal.

  FIG. 2 (e) shows a power reflection device 6 in which an amplifier 4, a variable attenuator 10, a phase shifter 11 and a circulator 12 are combined. The power reflection device 6 amplifies the received signal from the dipole antenna element 1 by the amplifier 4, adjusts the amplitude of the signal by the variable attenuator 10, adjusts the phase of the signal by the phase shifter 11, and adjusts the phase of the signal by the circulator 12. The signal from the phase shifter 11 is reflected to the dipole antenna element 1 as a reflected signal.

FIG. 2F shows a power reflection device 6 in which the amplifier 4, the reception circuit 5, the signal generator 13 and the circulator 12 are combined. The power reflecting device 6 amplifies the received signal from the dipole antenna element 1 by the amplifier 4, detects the signal by the receiving circuit 5, generates a reflected signal corresponding to the signal detected by the signal generator 13, The reflected signal from the signal generator 13 is reflected on the dipole antenna element 1 by the circulator 12. Here, the signal generator 13 may be an analog system or a digital system.
In addition, you may comprise the power reflection apparatus 6 combining arbitrarily the thing of Fig.2 (a)-(f).

  When the dipole antenna element 1 is used, that is, when a desired electromagnetic wave from the outside is received by the dipole antenna element 1, the switch 3 is switched to the receiving circuit 5 side, and the electromagnetic wave received by the dipole antenna element 1 is used as a received signal. Input to the receiving circuit 5. On the other hand, when the dipole antenna element 1 is not used, that is, when electromagnetic waves from the outside are not received, the switch 3 is switched to the power reflection device 6 side, and RCS is reduced.

Subsequently, the principle that the RCS is reduced by the antenna device according to the first embodiment of the present invention will be described with reference to FIGS.
FIG. 3 schematically shows a state of reflection from the dipole antenna element 1 and the ground conductor 2. In general, the RCS of the antenna device is maximized in the vertical direction of the ground conductor 2, and therefore, the RCS in the vertical direction will be described here.

  In FIG. 3, a plane wave 14 (electromagnetic wave) is incident on the dipole antenna element 1 from a distance (external). At this time, if the impedance matching between the dipole antenna element 1 and the feed line 15 connected to the dipole antenna element 1 is achieved, most of the plane wave 14 is transmitted into the feed line 15. An electromagnetic wave transmitted into the feed line 15 is defined as an in-line wave 16.

  A part of the plane wave 14 is reflected by the structure of the dipole antenna element 1. A reflected wave from the dipole antenna element 1 itself is defined as a structure reflected wave 17. A part of the plane wave 14 is reflected by the ground conductor 2. The reflected wave from the ground conductor 2 is defined as a ground conductor reflected wave 18.

  Here, in the conventional antenna device disclosed in Patent Document 1, a conjugate matching load is connected to the feed line 15 and the in-line wave 16 is absorbed, thereby reducing the RCS. However, in this method, as described above, the influence of the structure reflected wave 17 and the ground conductor reflected wave 18 is not considered, and a reflected wave in the vertical direction of the ground conductor 2 exists.

Next, the result of simulating RCS for an array antenna in which a plurality of dipole antenna elements 1 are arranged will be shown in comparison with that of a conventional antenna device.
FIG. 4 shows a simulation model in an array state in which twelve dipole antenna elements 1 are arranged. In FIG. 4, the distance between the dipole antenna elements 1 is λ, and the ground conductor 2 is set to have a size that protrudes about λ / 2 outside the dipole antenna element 1. Further, as described above, the distance between the ground conductor 2 and the dipole antenna element 1 is approximately λ / 4.

FIG. 5 shows a scattered field when the plane wave 14 is irradiated from the + Z direction of FIG.
FIG. 5A shows a scattering field when the dipole antenna element 1 does not exist and only the ground conductor 2 exists. FIG. 5B shows a scattering field when twelve dipole antenna elements 1 and ground conductors 2 are arranged as shown in FIG. 4 and the dipole antenna element 1 is terminated at 65Ω. Note that 65Ω is a load capable of obtaining conjugate matching with the dipole antenna element 1.

  Comparing FIGS. 5A and 5B, it can be seen that the level of the scattering field in the + Z direction is reduced by about 8 dB. However, as described above, since the structure reflected wave 17 and the ground conductor reflected wave 18 exist, the scattered field in the + Z direction does not have a sufficiently low value, and the RCS when the antenna device is viewed from the + Z direction is Not reduced enough.

FIG. 5C shows a scattered field when 12 dipole antenna elements 1 and ground conductors 2 are arranged as shown in FIG. 4 and the dipole antenna element 1 is terminated at 20Ω.
Comparing FIGS. 5B and 5C, it can be seen that the level of the scattering field in the + Z direction is reduced by about 18 dB. Therefore, RCS when this antenna device is viewed from the + Z direction can be sufficiently reduced.

  When the dipole antenna element 1 is terminated at 20Ω, the level of the scattered field in the + Z direction can be reduced because part of the in-line wave 16 is reflected by the terminating resistance and is radiated again from the dipole antenna element 1 as an electromagnetic wave. This is because the electromagnetic wave, the structure reflected wave 17 and the ground conductor reflected wave 18 radiated again cancel each other out of phase with each other in the + Z direction.

  As described above, when the dipole antenna element 1 is not used, the RCS can be reduced by switching the switch 3 to the power reflecting device 6 side and connecting the dipole antenna element 1 and the power reflecting device 6. it can. The example shown in FIG. 5 shows a scattered field at a resonance frequency where the input impedance of the dipole antenna element 1 is a pure resistance.

  When the frequency of the incoming electromagnetic wave deviates from the resonance frequency, the variable resistance element 7 (see FIG. 2 (a)) and the variable capacitance element 8 (see FIG. 2 (b)) or the variable induction element are included in the power reflecting device 6. RCS can be reduced by using a combination of 9 (see FIG. 2C).

  Here, when the structure reflected wave 17 or the ground conductor reflected wave 18 increases due to an increase in the size of the ground conductor 2 or a change in the structure of the dipole antenna element 1, the structure of the in-line wave 16 alone is sufficient. It becomes difficult to cancel the object reflected wave 17 and the ground conductor reflected wave 18. In this case, the in-line wave 16 is amplified to the extent that these reflected waves are canceled by the circuits as shown in FIG. 2 (e) and FIG. 2 (f) and radiated again from the dipole antenna element 1. Thus, RCS can be reduced.

  In addition, even if the dipole antenna element 1 shown in FIG. 1 is a single antenna device or an array antenna in which a plurality of dipole antenna elements 1 shown in FIG. 4 are arranged, the RCS can be similarly reduced. it can. Further, in the array antenna, the distribution of the reflection phase of each dipole antenna element 1 can reduce the RCS in a desired direction.

As described above, according to the first embodiment, the reflecting means adjusts at least one of the amplitude and the phase of the received signal so as to cancel the electromagnetic wave from the outside reflected by the ground conductor and the antenna element itself, and the reflected signal The antenna element radiates the input reflected signal as an electromagnetic wave.
Thereby, the electromagnetic wave from the outside reflected by the ground conductor and the antenna element itself is canceled by the electromagnetic wave radiated from the antenna element according to the reflected signal.
Therefore, an antenna device that can sufficiently reduce RCS can be obtained in consideration of the influence of reflected waves from the ground conductor and the antenna element itself.

Embodiment 2. FIG.
FIG. 6 is a block diagram showing an antenna apparatus according to Embodiment 2 of the present invention. In FIG. 6, the antenna apparatus includes a dipole antenna element 1, a ground conductor 2, an amplifier 4, a receiving circuit 5, a circulator 12, a coupler 19 (coupling circuit), and an amplitude / phase adjuster 20. Here, the circulator 12, the coupler 19, and the amplitude / phase adjuster 20 form a reflection means.

The operation of the antenna device having the above configuration will be described below. Note that description of operations similar to those of the first embodiment is omitted.
The electromagnetic wave received by the dipole antenna element 1 is input to the amplifier 4 through the circulator 12 as a received signal. The output from the amplifier 4 is input to the receiving circuit 5. A part of the output from the amplifier 4 is branched by the coupler 19 and input to the amplitude / phase adjuster 20.

  The amplitude / phase adjuster 20 amplitude and phase of the input received signal so as to cancel electromagnetic waves (structure reflected wave 17 and ground conductor reflected wave 18) from the outside reflected by the ground conductor 2 and the dipole antenna element 1 itself. Is reflected by the dipole antenna element 1 through the circulator 12 as a reflected signal. The reflected signal input to the dipole antenna element 1 is radiated again as an electromagnetic wave. Thereby, RCS can be reduced.

In the first embodiment, since the receiving circuit 5 side and the power reflecting device 6 side are switched by the switch 3, the RCS is reduced while using the dipole antenna element 1, that is, receiving electromagnetic waves from the outside. I couldn't.
On the other hand, according to the second embodiment, since there is no switching operation of the switch 3, RCS can be reduced while using the dipole antenna element 1 as a receiving antenna.

Embodiment 3 FIG.
FIG. 7 is a block diagram showing an antenna apparatus according to Embodiment 3 of the present invention. In FIG. 7, the antenna device includes a dipole antenna element 1, a ground conductor 2, an amplifier 4, a receiving circuit 5, a power reflecting device 6, and a duplexer 21. Here, the power reflecting device 6 and the duplexer 21 form a reflecting means.

The operation of the antenna device having the above configuration will be described below. Note that description of operations similar to those of the first embodiment is omitted.
The electromagnetic wave received by the dipole antenna element 1 is input to the duplexer 21 as a received signal. The duplexer 21 outputs a received signal having a frequency f1 (first frequency) to the amplifier 4 and outputs a received signal other than the frequency f1 to the power reflecting device 6. The output from the amplifier 4 is input to the receiving circuit 5.

  The power reflection device 6 has the amplitude and phase of the input received signal so as to cancel electromagnetic waves (structure reflected wave 17 and ground conductor reflected wave 18) from the outside reflected by the ground conductor 2 and the dipole antenna element 1 itself. At least one of them is adjusted and reflected to the dipole antenna element 1 through the duplexer 21 as a reflected signal. The reflected signal input to the dipole antenna element 1 is radiated again as an electromagnetic wave. Thereby, RCS in frequencies other than f1 can be reduced.

  As described above, according to the third embodiment, RCS at other frequencies can be reduced while receiving the electromagnetic wave of frequency f1.

Embodiment 4 FIG.
FIG. 8 is a block diagram showing an antenna apparatus according to Embodiment 4 of the present invention. In FIG. 8, the antenna device includes a dipole antenna element 1, a ground conductor 2, a circulator 12, a coupler 19, an amplitude / phase adjuster 20, and a transmission circuit 22. That is, this antenna device includes a transmission circuit 22 instead of the amplifier 4 and the reception circuit 5 shown in FIG. Here, the circulator 12, the coupler 19, and the amplitude / phase adjuster 20 form a reflection means.

The operation of the antenna device having the above configuration will be described below. Note that description of operations similar to those of the second embodiment is omitted.
The electromagnetic wave received by the dipole antenna element 1 is input to the amplitude / phase adjuster 20 via the circulator 12 as a received signal. The amplitude / phase adjuster 20 amplitude and phase of the input received signal so as to cancel electromagnetic waves (structure reflected wave 17 and ground conductor reflected wave 18) from the outside reflected by the ground conductor 2 and the dipole antenna element 1 itself. Is output to the coupler 19 as a reflected signal.

  The transmission circuit 22 generates a transmission signal and outputs it to the coupler 19. In the coupler 19, the reflected signal from the amplitude / phase adjuster 20 and the transmission signal from the transmission circuit 22 are mixed and output to the dipole antenna element 1 via the circulator 12. The reflected signal and transmission signal input to the dipole antenna element 1 are radiated as electromagnetic waves. Thereby, RCS can be reduced.

  As described above, according to the fourth embodiment, it is possible to reduce RCS with respect to electromagnetic waves coming from the outside while using the dipole antenna element 1 as a transmission antenna.

Embodiment 5 FIG.
FIG. 9 is a block diagram showing an antenna apparatus according to Embodiment 5 of the present invention. In FIG. 9, this antenna device includes a dipole antenna element 1, a ground conductor 2, a power reflection device 6, a duplexer 21, and a transmission circuit 22. That is, this antenna apparatus includes a transmission circuit 22 instead of the amplifier 4 and the reception circuit 5 shown in FIG. Here, the power reflecting device 6 and the duplexer 21 form a reflecting means.

The operation of the antenna device having the above configuration will be described below. Note that description of operations similar to those of the third embodiment is omitted.
The electromagnetic wave received by the dipole antenna element 1 is input to the duplexer 21 as a received signal, and the received signal other than the frequency f1 is output to the power reflecting device 6. The power reflection device 6 has the amplitude and phase of the input received signal so as to cancel electromagnetic waves (structure reflected wave 17 and ground conductor reflected wave 18) from the outside reflected by the ground conductor 2 and the dipole antenna element 1 itself. At least one of them is adjusted and reflected to the dipole antenna element 1 through the duplexer 21 as a reflected signal.

  The transmission circuit 22 generates a transmission signal having a frequency f 1 and outputs the transmission signal to the dipole antenna element 1 via the duplexer 21. The reflected signal and transmission signal input to the dipole antenna element 1 are radiated as electromagnetic waves. Thereby, RCS in frequencies other than f1 can be reduced.

  As described above, according to the fifth embodiment, RCS at other frequencies can be reduced while transmitting an electromagnetic wave having a frequency f1.

Embodiment 6 FIG.
FIG. 10 is a block diagram showing an antenna apparatus according to Embodiment 2 of the present invention. In FIG. 10, the antenna device includes a dipole antenna element 1, a ground conductor 2, a switch 3, an amplifier 4, a receiving circuit 5, a circulator 12, a coupler 19, an amplitude / phase adjuster 20, and a transmitting circuit 22. That is, this antenna device includes a switch 3 and a transmission circuit 22 in addition to the antenna device shown in FIG.

  The switch 3 switches the connection destination of the dipole antenna element 1 to the transmission circuit 22 side or the reception circuit 5 side. One end of the switch 3 is connected to the transmission circuit 22, and the other end of the switch 3 is connected to the circulator 12. Here, the circulator 12, the coupler 19, and the amplitude / phase adjuster 20 form a reflection means.

The operation of the antenna device having the above configuration will be described below. Note that description of operations similar to those of the second embodiment is omitted.
When the dipole antenna element 1 is used as a transmission antenna, the switch 3 is switched to the transmission circuit 22 side, and a transmission signal generated by the transmission circuit 22 is output to the dipole antenna element 1. On the other hand, when the dipole antenna element 1 is used as a receiving antenna, the switch 3 is switched to the receiving circuit 5 side, and the electromagnetic wave received by the dipole antenna element 1 is input to the receiving circuit 5 as a received signal.

  As described above, according to the sixth embodiment, the dipole antenna element 1 can be operated as both a transmission antenna and a reception antenna. In addition, since the reflection means for reducing the RCS is incorporated on the receiving circuit 5 side of the switch 3 as in the second embodiment, when the dipole antenna element 1 is used as a receiving antenna, the RCS is set. Can be reduced.

  In the sixth embodiment, the configuration in which the switch 3 and the transmission circuit 22 are combined on the basis of the antenna device shown in the second embodiment is described. However, the present invention is not limited to this, and the first and third embodiments are not limited thereto. The switch 3 and the transmission circuit 22 may be combined based on the antenna device shown in FIG. In these cases, the same effect as in the sixth embodiment can be obtained. Further, the reflection means for reducing the RCS described in the fourth and fifth embodiments may be incorporated on the transmission circuit 22 side of the switch 3. A diplexer may be used instead of the switch 3.

Embodiment 7 FIG.
FIG. 11 is a block diagram showing an antenna apparatus according to Embodiment 7 of the present invention. In FIG. 11, this antenna apparatus includes a dipole antenna element 1, a ground conductor 2, an amplifier 4, a receiving circuit 5, a circulator 12, a coupler 19, an amplitude phase adjuster 20, and a curved frequency selection surface 23 (Frequency Selective Surface, (Hereinafter referred to as “FSS23”).

  The FSS 23 is arranged in the radiation direction of the dipole antenna element 1, transmits the electromagnetic wave having the operating frequency f1 of the dipole antenna element 1, and acts as a metal surface for electromagnetic waves other than the frequency f1. Here, the circulator 12, the coupler 19, and the amplitude / phase adjuster 20 form a reflection means.

The operation of the antenna device having the above configuration will be described below. Note that description of operations similar to those of the second embodiment is omitted.
When the electromagnetic wave arriving from the outside is at the frequency f1, the RCS can be reduced as shown in the second embodiment. Further, when the electromagnetic wave coming from outside is other than the frequency f1, the incoming electromagnetic wave is scattered by the FSS 23, so that the scattered field in the direction in which the electromagnetic wave arrives is reduced, and RCS at a frequency other than f1 is reduced. be able to.

  As described above, according to the seventh embodiment, RCS can be reduced regardless of whether the electromagnetic wave arriving from the outside is the operating frequency f1 of the dipole antenna element 1 or other than the frequency f1. Further, since the FSS 23 has a characteristic of transmitting the electromagnetic wave having the frequency f1, the operation of the dipole antenna element 1 as an antenna is not hindered.

  In the seventh embodiment, the configuration in which the FSS 23 is combined with the antenna device shown in the second embodiment is shown. However, the present invention is not limited to this, and the antenna devices shown in other first and third to sixth embodiments. May be combined with FSS23. In these cases, the same effect as in the seventh embodiment can be obtained.

  DESCRIPTION OF SYMBOLS 1 Dipole antenna element, 2 Ground conductor, 3 Switch, 4 Amplifier, 5 Receiver circuit, 6 Power reflection apparatus, 7 Variable resistance element, 8 Variable capacity element, 9 Variable induction element, 10 Variable attenuator, 11 Phase shifter, 12 Circulator, 13 Signal generator, 14 Plane wave, 15 Feed line, 16 In-line wave, 17 Structure reflected wave, 18 Ground conductor reflected wave, 19 Coupler, 20 Amplitude phase adjuster, 21 Divider, 22 Transmitter circuit, 23 Frequency selective surface.

Claims (10)

With ground conductors,
An antenna element that is disposed at a predetermined distance from the ground conductor, receives an electromagnetic wave from the outside as a received signal, and radiates an input reflected signal as an electromagnetic wave,
At least one of the amplitude and phase of the received signal is adjusted so as to cancel the electromagnetic wave from the outside that is connected to the antenna element and reflected by the ground conductor and the antenna element itself, and is reflected on the antenna element as the reflected signal. Reflecting means for reflecting;
An antenna device comprising: A switch provided between the antenna element and the reflecting means and for branching the received signal;
A receiving circuit that is connected to one end of the switch on the branch side and that performs a receiving process on the received signal;
The antenna device according to claim 1, wherein the reflection unit is connected to the other end of the switch on the branch side. A receiving circuit connected to the antenna element and performing a receiving process on the received signal;
The reflecting means is
A coupling circuit provided between the antenna element and the receiving circuit and branching a part of the received signal;
An amplitude and phase adjustment circuit that is connected to the coupling circuit and adjusts the amplitude and phase of the branched received signal and outputs the received signal as the reflected signal;
A circulator provided between the antenna element and the coupling circuit, for outputting the received signal from the antenna element to the receiving circuit, and outputting the reflected signal from the amplitude / phase adjusting circuit to the antenna element; The antenna device according to claim 1, comprising: A receiving circuit connected to the antenna element and performing a receiving process on the received signal;
The reflecting means is
A power reflection device that adjusts at least one of the amplitude and phase of the input received signal and outputs the received signal as the reflected signal;
2. A duplexer that outputs the received signal having a first frequency to the receiving circuit and outputs the received signal other than the first frequency to the power reflecting device. Antenna device. A transmission circuit connected to the antenna element for generating a transmission signal for radiating as an electromagnetic wave from the antenna element;
The reflecting means is
An amplitude and phase adjustment circuit that adjusts the amplitude and phase of the input received signal and outputs the received signal as the reflected signal;
A circulator that is provided between the antenna element and the transmission circuit, outputs the reception signal from the antenna element to the amplitude phase adjustment circuit, and outputs the transmission signal from the transmission circuit to the antenna element; ,
The antenna apparatus according to claim 1, further comprising: a coupling circuit that is provided between the circulator and the transmission circuit and that mixes and outputs the transmission signal and the reflection signal. A transmission circuit connected to the antenna element and generating a transmission signal of a first frequency for radiating as an electromagnetic wave from the antenna element;
The reflecting means is
A power reflection device that adjusts at least one of the amplitude and phase of the input received signal and outputs the received signal as the reflected signal;
A duplexer that outputs the transmission signal of the first frequency from the transmission circuit to the antenna element and outputs the reception signal other than the first frequency to the power reflection device. The antenna device according to claim 1. A transmission circuit for generating a transmission signal for radiating as electromagnetic waves from the antenna element;
The antenna device according to any one of claims 2 to 4, further comprising separation means for separating the reception signal and the transmission signal. A receiving circuit that performs a receiving process on the received signal received by the antenna element;
The antenna device according to claim 5, further comprising a separation unit that separates the reception signal and the transmission signal.   The structure according to any one of claims 1 to 8, further comprising a structure that is arranged in a radiation direction of the antenna element and reflects or scatters an electromagnetic wave different from an operating frequency of the antenna element. The antenna device described.   The antenna device according to any one of claims 1 to 9, wherein a plurality of the antenna elements are arranged side by side.

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