JP2013026817A - Phased array antenna - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the following problem: A conventional phased array antenna used for a radar device degrades because a part of transmission power is consumed in a terminator connected to a transmission/reception changeover switch by mutual coupling between elements.SOLUTION: The phased array antenna includes: a first antenna that transmits and receives signals; a second antenna that only receives signals; and a feeder circuit that distributes a transmission signal to the first antenna and synthesizes reception signals from the first antenna and the second antenna. The second antenna prevents generation of efficiency degradation during signal transmission by providing a stub for reflecting a transmission signal leaked and invaded while the first antenna is conducting signal transmission.

Description

  The present invention relates to a phased array antenna. Specifically, the present invention relates to a phased array antenna used in a radar apparatus mounted on an aircraft, a ship, or a ground device.

  The phased array antenna is provided with a phase shifter for performing beam scanning on each element antenna of an array antenna in which element antennas are arranged in a plane or curved surface. Compared to conventional mechanically driven antennas, beam scanning can be performed at high speed, and amplifiers can be distributed in each element antenna. It is actively used as an antenna for ships or ground radar devices.

  In the conventional phased array antenna, as will be described later, a part of the transmission signal is transmitted from the element antenna to the circulator by leakage from the adjacent element antenna due to mismatch between the element antenna and the feed line or mutual coupling between elements. Return to. These powers are sent to the terminator via a duplex switch to protect the low noise amplifier and converted to heat.

The decrease in efficiency due to leakage from adjacent element antennas due to mutual coupling between elements is significant when the element spacing is narrow. For example, in the case of an infinite planar array with element spacing of λ / 2 (λ is the operating wavelength) It is known that the theoretical upper limit of efficiency due to the mutual coupling is π / 4.
In this case, 20% or more of the power applied by the high power amplifier is necessarily consumed by the terminator.

  As a technique for preventing such a decrease in efficiency due to coupling between elements, an element antenna is thinned out of a plurality of element antennas in an array antenna apparatus in which a plurality of element antennas are provided at lattice points of a given arrayed lattice. In this case, a technique is disclosed in which a termination resistor attached to a feeding point of a thinning element antenna that is not excited is removed while leaving a radiation element of the thinning element antenna that is not excited on the aperture surface of the array antenna (for example, Patent Document 1).

Japanese Patent No. 4515925

  However, in the conventional technique, the termination element attached to the feeding point of the thinning element that is not excited is removed while the radiation element of the thinning element antenna that is not excited is left on the opening surface, and the feeding line between the feeding point and the feeding point is removed. Therefore, depending on the element spacing and element type, the RF signal reflected by the thinning element is superimposed on the RF signal from the radiating element in reverse phase, thereby reducing the element antenna gain within the antenna coverage.

Also, depending on the element antenna, the matching state is different, so that the reception side lobe is increased by increasing the variation of the element pattern caused by receiving the RF signal reflected and re-radiated by the adjacent element by mutual coupling, etc. Could cause problems.
Such an increase in the reception side lobe causes an increase in reception clutter power in the radar apparatus, causing problems such as a decrease in detection distance.

  The phased array antenna according to the present invention includes a first antenna for transmitting and receiving a signal, a second antenna for receiving a signal, a transmission signal to the first antenna, and the first antenna. And a feeding circuit that synthesizes a reception signal from the second antenna, wherein the second antenna transmits the transmission signal when the first antenna transmits the transmission signal. An amplifier for amplifying the received signal and a variable attenuator when the received signal is received by the second antenna. The power supply circuit is connected via a device.

According to the phased array antenna of the present invention, at the time of transmission, it is possible to improve the antenna efficiency by suppressing the power consumption at the terminator of the adjacent thinning element, and at the time of reception, the beam is formed by using all elements, Low side lobe characteristics required by the beam can be easily obtained.

It is a block diagram of the phased array antenna which concerns on Embodiment 1 of this invention. It is a block diagram of the phased array antenna which concerns on other embodiment of this invention. It is a block diagram of the conventional phased array antenna.

  Here, after a problem is first described by explaining the configuration and operation of a conventional phased array antenna, the phased array antenna according to the present invention will be described.

FIG. 3 is a diagram showing an example of the configuration of a conventional phased array antenna.
In FIG. 3, 1 is an element antenna, 2 is a circulator that is connected to the element antenna and separates transmission and reception signals, 3 and 7 are transmission / reception changeover switches, 4 is a high-power amplifier that amplifies the transmission signal, and 5 is leaked from the circulator A terminator that absorbs the transmission signal, 6 is a low-noise amplifier that amplifies the reception signal, 8 is a phase shifter, and 9 is a power feeding circuit that distributes the transmission signal to each element antenna and synthesizes the reception signal.
In FIG. 3, (a) shows a state in which the transmission / reception changeover switches 3 and 7 are both placed on the transmission side in the transmission state. FIG. 3B shows a case where the transmission / reception changeover switch is tilted to the reception side in the reception state.

Next, the operation will be described. In the transmission state (FIG. 3A), the signal distributed by the power feeding circuit 9 is given a phase for forming a desired beam by the phase shifter 8, and is transmitted by the high power amplifier 4 via the transmission / reception changeover switch 7. Amplified and sent to the circulator 2 and radiated from the element antenna 1.
The RF signal radiated from the element antenna 1 forms a desired beam in space based on the phase given by the phase shifter, is reflected by a distant target, and returns to the antenna as a received signal.

  Due to the time difference until the RF signal returns, the reception signal received by each element antenna in the reception state (b) is sent to the low noise amplifier 6 via the circulator 2 and the transmission / reception selector switch 3 and amplified. The phase shifter 8 gives a phase for forming a desired beam, is synthesized by the feeding circuit 9, and is sent to the receiver.

  Due to recent advances in device technology, devices used in the high power amplifier 4 have shifted from conventional gallium arsenide to high voltage / high output devices such as gallium nitrogen and silicon carbide. With these devices, it is becoming possible to realize an output of several tens to hundreds of watts in a microwave band with a single high power amplifier.

Therefore, even in the phased array antenna, it is possible to obtain the same transmission power with a smaller number of elements than before.
However, since such a high power amplifier is expensive, fewer elements are connected to the high power amplifier over the array aperture. It is conceivable to reduce the number of high power amplifiers while suppressing a decrease in array aperture gain by so-called element thinning.

  In Patent Document 1, the radiating element of the thinning element antenna that is not excited is left on the opening surface, the termination element attached to the feeding point of the thinning element that is not excited is removed, and the feeding line between the feeding point and the feeding point is removed. Therefore, depending on the element spacing and the element type, the RF signal reflected by the thinning element is superimposed on the RF signal from the radiating element in reverse phase, thereby reducing the element antenna gain within the antenna coverage. It was.

Also, depending on the element antenna, the matching state is different, so that the reception side lobe is increased by increasing the variation of the element pattern caused by receiving the RF signal reflected and re-radiated by the adjacent element by mutual coupling, etc. Could cause problems.
Such an increase in the reception side lobe causes an increase in reception clutter power in the radar apparatus, causing problems such as a decrease in detection distance.

Embodiment 1 FIG.
Next, a phased array antenna according to Embodiment 1 of the present invention will be described with reference to the drawings.
FIG. 1 is a diagram showing a configuration of a phased array antenna according to Embodiment 1 of the present invention.
In FIG. 1, 1 is an ON element antenna (an element antenna that excites and transmits signals), and 2 is a circulator (an example of a transmission / reception number switching unit) that is connected to the excitation element antenna and separates transmission and reception signals. 3) is a transmission / reception selector switch (corresponding to the first transmission / reception selector switch), 4 is a high power amplifier for amplifying the transmission signal, 5 is a terminator for absorbing the transmission signal leaked from the circulator, and 6 is a reception signal. , 7 is a transmission / reception changeover switch (corresponding to a second transmission / reception changeover switch), 8 is a phase shifter, 9 is a power supply circuit that distributes a transmission signal to each element antenna and synthesizes a reception signal, 10 Is a variable attenuator that gives an appropriate excitation distribution to the received signal, 11 is a decimation element antenna (a decimation element antenna that performs only signal reception, corresponding to the second antenna), 2 is a stub that reflects the RF signal leaked in the thinning element at an appropriate phase, 31 is a transmission / reception changeover switch (corresponding to a third transmission / reception changeover switch), and 71 is a transmission / reception changeover switch (equivalent to a fourth transmission / reception changeover switch). ).
FIG. 1A shows a transmission state where transmission / reception change-over switches 3, 7, 31, 71 are placed on the transmission side, and FIG. 1B shows a reception state where transmission / reception change-over switches 3, 7 , 31 and 71 are placed on the receiving side.

Next, the operation of the phased array antenna according to Embodiment 1 will be described.
In the transmission state of FIG. 1 (FIG. 1 (a)), the signal distributed in the power feeding circuit 9 is given a phase for forming a desired beam by the phase shifter 8, and high power is transmitted via the transmission / reception changeover switch 7. Amplified by the amplifier 4, sent to the circulator 2, and radiated from the ON element antenna 1.
The RF signal radiated from the ON element antenna 1 forms a desired beam in space based on the phase given by the phase shifter 8.

  At this time, a part of the RF signal radiated from the ON element antenna 1 is coupled to the adjacent thinning element 11 by mutual coupling between the elements, but with an appropriate phase with a preset stub 12 via the transmission / reception changeover switch 31. By being reflected, it is radiated from the thinning element 11 again, so that it is superimposed on the transmission signal from the ON element antenna 1 and contributes to improving the efficiency of the ON element antenna 1.

Due to the time difference until the RF signal returns, the reception signal received by each ON element antenna 1 in the reception state (FIG. 1B) is sent to the low noise amplifier 6 via the circulator 2 and the transmission / reception changeover switch 3. After being amplified, the phase shifter 8 gives a phase for forming a desired beam. Further, a desired excitation distribution is given by the attenuator 10, synthesized by the power feeding circuit 9, and sent to the receiver.
The received signal received by the thinning element 11 is sent to the low noise amplifier 6 via the transmission / reception selector switch 31 and amplified, and then given a phase for forming a desired beam by the phase shifter 8. It is done. Further, a desired excitation distribution is given by the attenuator 10 and is synthesized by the power feeding circuit 9 in the same manner as the reception signal from the ON element to form a reception beam.

  Here, the attenuator 10 is set with an attenuation amount corresponding to a distribution for realizing a low side lobe, for example, a Dorf Chebyshev distribution and a Taylor distribution, and there is no circulator 2 in the thinning element system with respect to the ON element system. The amount of attenuation for correcting the variation in gain between systems due to the above is set.

Also, in the reception state, all element antennas are connected to the feed line and the low noise amplifier, and the matching conditions of the element antennas are the same for all elements, so that the RF signals reflected and re-radiated by adjacent elements are mutually coupled. Variation of the receiving element pattern due to reception by the receiver is reduced, and low side lobe characteristics required by the receiving beam can be easily obtained.

As described above, according to the embodiment of the present invention, the power consumed by the terminator of the adjacent decimation element is reflected and re-radiated by the stub 12 at the time of transmission in the conventional phased array antenna, In addition to improving the efficiency of the antenna and forming a beam using all elements at the time of reception, low sidelobe characteristics required for the reception beam can be easily obtained.

In this embodiment, the circulator 2 is used as a device that separates a transmission signal and a reception signal. However, the circulator 2 is not limited to this circulator, and any device having a function of separating transmission and reception signals may be used. For example, a transmission / reception switch may be used.

In the present embodiment, the ON element antenna (excitation element antenna) 1 performs transmission and reception, but may be a transmission-dedicated antenna that performs only signal transmission. In this case, as shown in FIG. 2, the phased array antenna has a configuration in which a transmission-dedicated antenna and a reception-dedicated antenna are arranged in a plane or curved surface. Depending on the application, such a transmission-dedicated antenna and a reception-dedicated antenna are used. It is good also as an antenna structure which has arranged.

1 ON element antenna (first antenna), 2 circulator, 3 transmission / reception switch (first transmission / reception switch), 4 high power amplifier, 5 terminator, 6 low noise amplifier, 7 transmission / reception switch (second transmission / reception) Changeover switch), 8 phase shifter, 9 feeding circuit, 10 variable attenuator, 11 thinning element antenna (second antenna), 12 stub, 31 transmission / reception changeover switch (third transmission / reception changeover switch), 71 transmission / reception changeover switch ( Fourth transmission / reception changeover switch).

Claims (4)

A first antenna that transmits and receives signals, a second antenna that receives signals, a transmission signal that is distributed to the first antennas, and reception from the first antenna and the second antenna A phased array antenna comprising a power feeding circuit for combining signals,
The second antenna is connected to a stub that reflects the transmission signal leaked into the second antenna at a predetermined phase when the first antenna transmits the transmission signal. A phased array antenna, wherein an antenna is connected to the power feeding circuit via an amplifier, a variable attenuator, and a phase shifter that amplify the received signal when receiving the received signal. The first antenna is connected to a transmission / reception signal switching unit that separates a transmission signal and a reception signal, and one end of the transmission / reception signal switching unit is connected to an amplifier that amplifies the transmission signal when transmitting the transmission signal. And the other end of the transmission / reception signal switching unit is connected to a terminator, and one end of the transmission / reception signal switching unit is opened via the amplifier when receiving the received signal. 2. The phased array antenna according to claim 1, wherein the other end of the transmission / reception signal switching unit is connected to the feeding circuit through an amplifier, a variable attenuator, and a phase shifter for amplifying the received signal. . A first antenna that transmits and receives signals, a second antenna that receives signals, a transmission signal that is distributed to the first antennas, and reception from the first antenna and the second antenna A phased array antenna comprising a power feeding circuit for combining signals,
A transmission / reception signal switching unit connected to the first antenna and separating a transmission signal and a reception signal;
A first transmission / reception switch that is connected to one terminal of the transmission / reception signal switching unit from which a reception signal is output, and switches a connection destination between a terminator and a reception signal amplifier that amplifies the reception signal;
A variable attenuator connected to the received signal amplifier and providing a predetermined excitation distribution to the received signal;
A transmission signal amplifier that is connected to the other terminal of the transmission / reception signal switching unit and amplifies and outputs a transmission signal;
A second transmission / reception change-over switch connected to the phase shifter connected to the power feeding circuit and switching a connection destination between the variable attenuator and the transmission signal amplifier;
A third transmission / reception selector switch that is connected to the second antenna and that switches between a reception signal amplifier that amplifies the reception signal and a stub that reflects the input signal at a predetermined phase;
A variable attenuator connected to the received signal amplifier and providing a predetermined excitation distribution to the received signal;
A fourth transmission / reception change-over switch connected to the phase shifter connected to the power feeding circuit and switching the connection destination between the variable attenuator and the terminator;
With
At the time of transmission, each connection destination of the first, second, third, and fourth transmission / reception switch is the terminator, the transmission signal amplifier, the stub, and the terminator,
At the time of reception, the connection destination of each of the first, second, third, and fourth transmission / reception change-over switches is the reception signal amplifier, the variable attenuator, the reception signal amplifier, and the variable attenuator.
A phased array antenna characterized by that. The phased array antenna according to any one of claims 1 to 3, wherein the first antenna and the second antenna are arranged adjacent to each other in a planar or curved shape.

Images