JP2015025743A - Output port number conversion matrix circuit and phased array antenna - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power supply circuit and a phased array antenna, capable of greatly suppressing side lobe.SOLUTION: An output port number conversion matrix circuit 20 includes: four or more input terminals connected to the output terminal of a power supply circuit 10 for multi-beam one-to-one; the even number of branch passages branched from the input terminal; output terminals Port2-Port7 more than the number of input terminals by the number of branch passages; and transmission lines L0-L3 connected to the respective output terminals Port2-Port7 and performing impedance matching. The output port number conversion matrix circuit 20 is configured such that a power level supplied to the central output terminals Port4 and Port5 is maximum, and a power level supplied to an output terminal is gradually small as the position of the output terminal is away from the center.

Description

  The present invention relates to a conversion matrix circuit for the number of output ports of a multi-beam antenna used for angle measurement of a microwave laser, for example, a 4-element / 6-element conversion matrix circuit capable of suppressing side lobes of a phased array antenna and a phased including the same. It relates to an array antenna.

  In order to discriminate between an intruder and a false detection in a security system, there is a need for a system that identifies the position of the intruder and tracks the object detected by the camera. In order to configure this system, target position information is required, and one method for obtaining this information is to use a microwave sensor as the sensor. In order to detect the position of the intruder, it is necessary to perform distance measurement and angle measurement.

Regarding distance measurement, a simple method using a two-frequency CW method has been reported (Non-Patent Document 1).
Regarding angle measurement, a method of detecting the direction of a target by scanning a beam using a phased array antenna in the field of radar technology has been reported. However, this method is expensive and complicated for consumer applications. It is difficult to adopt (Non-Patent Document 2). As a method for measuring the angle at low cost, there is a sequential roving method using a beam switching antenna (Non-Patent Document 3). This directs the beam in a plurality of different directions and estimates the target direction from the reception level in each beam direction.

  In recent years, HTBM (Hybrid Three Direction Beam Matrix) circuits, QTBM (Quarter Wavelength Three Direction Beam Matrix) circuits, and RTBM (Rat-race Tree Beam Matrix) circuits have been used as inexpensive and simple four-element beam switching antenna feed circuits. Have been reported. These are feed matrix circuits that can switch the beam in three directions by setting the phase difference between antennas to 0 °, 90 °, and −90 ° by a switch (Non-Patent Document 4, Non-Patent Document 5, Non-patent). Reference 6).

Merrill I. Skolnik, Introduction to Radar systems, 3 rd.New York: McGraw-Hill, 2001. Merrill Skolnik, Radar Handbook, 2nd.New York: McGraw-Hill, 1990. Takashi Yoshida, “Revised Radar Technology,” The Institute of Electronics, Information and Communication Engineers, pp.3, Tokyo, 1996. Masatoshi Tsuji, “Feeding Matrix Placed on a Single Layer with Hybrid Coupler Controlling Beams in Three Directions Including Boresight,“ IEICE Transaction on communications, Vol.E95-B, No10, pp. 3324-3327, Oct. 2012. Masatoshi Tsuji; “Boresight using λ / 4 transmission line, small-feed matrix circuit with 3-beam direction control,” IEEJ Transactions C, Vol.128, No.6, pp.926-932, Jun. 2008. Masatoshi Tsuji; “3-way beam switching small-sized feed matrix circuit using rat race,” IEICE Transactions B, vol. J94-B, no. 3, pp. 484-486, Mar. 2011. Hiroyuki Arai, “New Antenna Engineering,” General Electronic Publishing Company, pp. 84-85, Tokyo, 1996.

In the conventional beam switching antenna, the side lobe is large, and when used for angle measurement, the side lobe makes it difficult to detect the target direction, which is a problem.
Even in the beam switching antenna using the HTBM circuit, the QTBM circuit, and the RTBM circuit, there is a problem that the side lobe is large and it is difficult to detect the target direction of the side lobe when used for angle measurement.

  Accordingly, an object of the present invention is to provide a power feeding circuit and a phased array antenna that can significantly suppress side lobes compared to conventional systems.

A first invention is an output port number conversion matrix circuit connected to a multi-beam antenna power supply circuit, and has four or more input terminals connected one-to-one with the output terminals of the multi-beam antenna power supply circuit And an even number of branch paths branched from the input terminals, output terminals having more branch paths than the number of input terminals, and transmission lines connected to each output terminal and performing impedance matching, The output port number conversion matrix circuit is characterized in that the power level fed to the output terminal is the highest, and the power level fed becomes smaller as the position of the output terminal is further away from the center.
According to a second invention, in the first invention, there are four input terminals, six output terminals, each connected to a transmission line having a line length of λ / 4, and a pair of terminals located at both ends. An input terminal is connected to the branch path, and a pair of output terminals located at both ends are further connected to a ground resistance (R ₁ ), a transmission line (L ₃ ) having a line length of 2λ, and the branch path, respectively. Features.
According to a third invention, in the second invention, a characteristic impedance Z ₀ of a transmission line (L ₀ ) having a line length λ / 4 connected to a pair of output terminals (Port 4 and Port 5) located in the center, A characteristic impedance Z ₁ of a transmission line (L ₁ ) having a line length of λ / 4 connected to a pair of output terminals (Port 3 and Port 6) adjacent to a pair of output terminals positioned, and a pair of outputs located at both ends terminal (Port2, Port7) connected to the line length lambda / 4 transmission line (L ₂₎ of the characteristic impedance Z _2, the characteristic impedance Z ₃ and the ground resistance of the transmission path of the line length 2λ (L ₃₎ (R ₁ ) is calculated by the following equations 1 to 5.
[Formula 1]
[Formula 2]
[Formula 3]
[Formula 4]
[Formula 5]
A fourth invention is a phased array antenna antenna comprising the output port number conversion matrix circuit according to any one of the first to third inventions, and a multi-beam antenna feeding circuit.

  According to the present invention, the side lobe in the boresight direction of the phased array antenna can be greatly improved by applying a simple improvement to the conventional feeding circuit.

The block diagram of the matrix electric power feeding circuit which concerns on an Example. Explanatory drawing of the pattern of the 6 element batch array antenna which concerns on an Example. The graph which shows the radiation characteristic of the 6 element array antenna which concerns on an Example.

  Hereinafter, details of the present invention will be described with reference to examples, but the present invention is not limited to the examples.

The system of the embodiment includes a feed matrix circuit and an antenna connected to the circuit.
<Configuration of feeding matrix circuit>
FIG. 1 is a configuration diagram of a power feeding matrix circuit according to the present embodiment. The power feeding matrix circuit of this embodiment includes a multi-beam power feeding circuit 10 and an output port number conversion matrix circuit 20.
The multi-beam power supply circuit 10 is a known four-element three-way beam switching power supply circuit, and can be configured by, for example, the above-described HTBM, QTBM, and RTBM circuits. The signal input to Port 1 is subjected to impedance conversion by a transformer TR having a turns ratio of 2: 1, and then the phase is changed by phase shifters Ph1 to Ph4 and transmitted to output terminals ANT1 to ANT4 of a four-element beam switching antenna. .

The output port number conversion matrix circuit 20 includes a pair of transmission lines L _{0 to} L ₃ and a resistor R 1. The line length of each transmission line in the matrix circuit 20 is L _{0 to} L ₂ = λ / 4 and L ₃ = 2λ. Transmission line L ₃ as shown by a rectangle long is disposed on the back surface of the substrate.
The input terminals of the matrix circuit 20 are connected to ANT1 to ANT4 of the power supply circuit 10. That is, each signal transmitted to ANT1~ANT4 of the feeder circuit 10 enters the output port number conversion matrix circuit 20 is split into 6 output Port2~Port7 through the transmission line L ₀ ~L ₃ and the resistor R1.
Next, an operation of converting a 4-output signal into 6 outputs with sidelobe suppression will be described.

<Operation>
ANT2 and signal output from ANT3 is directly transmitted to the Port4, Port5 via the transmission line L _0. ANT1 and signals output from ANT4, the signal is branched at the connection point of L ₃ and L _1. That is, the signal output from ANT1 is transmitted to Port3 and Port7, and the signal output from ANT4 is transmitted to Port2 and Port6. Here, some of the signals transmitted each L _3, after consuming the power in each R _1, to Port2 from ANT4, transferred from ANT1 to PORT7. L ₁ and L ₂ operate as λ / 4 impedance converters, and each port is matched.

In order to form a beam with suppressed side lobes, the power level supplied to each port is set so that the central port 4 and port 5 are the largest and the level is smaller at the end port. When the power is fed to the Port4 and Port5 P1, Port3 and Port6 power fed to P2, the power fed to Port2 and Port7 and P3, transmission line L ₀ ~L ₃ characteristic impedance Z ₀ to Z ₃ And the resistance R ₁ can be obtained by the following equations 1 to 5. Here, R ₀ is the input / output impedance of Port2 to Port7.

[Formula 1]
[Formula 2]
[Formula 3]
[Formula 4]
[Formula 5]

<Simulation and results>
The simulation of the power feeding matrix circuit according to the example was analyzed by a high-frequency circuit simulator SNAP (modified contact analysis method, MEL).
The input / output impedance of each port is 50Ω. Each transmission line uses a microstrip line. The power ratio is set to P1: P2: P3 = 1: 0.653: 0.228 according to the power distribution of binomial directivity (Non-patent Document 7). From the above formulas 1 to 5, the characteristic impedance and resistance value of each transmission line are calculated as follows.

[Characteristic impedance and resistance value of each transmission line]
Z ₀ = 50Ω, Z ₁ = 76.25Ω, Z ₂ = 20.36Ω, Z ₃ = 87.7Ω, R ₁ = 5.23Ω.

The frequency used in the design is 2.45 GHz in the ISM band.
The width and length of each microstrip line are determined by the simulator: L ₀ : (1.86 mm, 18.9 mm), L ₁ : (0.85 mm, 19.45 mm), L ₂ : (6.36 mm, 18 mm), L ₃ : (0.63 mm, 157 mm). The passage loss of the line and the reflection loss due to the junction part of the line are ignored as being small.
The phase values of the phase shifters Ph1 to Ph4 when performing the simulation are all 0 ° when the beam is in the boresight direction (β = 0 °), and (Ph1) when the beam is in the left direction (β = 90 °). , Ph2, Ph3, Ph4) = (0 °, 90 °, 180 °, 270 °, 0 °) and the beam is in the right direction (β = −90 °), (Ph1, Ph2, Ph3, Ph4) Set to = (0 °, -90 °, -180 °, -270 °, 0 °).

Table 1 is the result of the simulated S-parameter at 2.45 GHz.

When β = 0 °, the phase difference between the ports is 0 °, when β = 90 ° is + 90 ° with respect to Port2, and when β = −90 ° is −90 ° with respect to Port2.
From these results, it can be seen that the circuit of the example operates as a six-element beam switching antenna. Moreover, those levels correspond to the set power ratio. S ₁₁ was −40 dB or less in any setting, and it was confirmed that matching was achieved.
These simulation values were consistent with the theoretical values, and it was confirmed that they were designed correctly.

<Antenna and radiation characteristics>
FIG. 2 shows a six-element patch array antenna according to the embodiment.
The array antenna used in this embodiment is a 19 mm square rectangular patch antenna. Numbers 2 to 7 attached to the patch antenna are feed points, and port numbers connected from the feed circuit are shown. The feeding method is backside feeding at an input impedance of 50Ω, 6mm away from the bottom side. The patch antennas are arranged at intervals of 0.33λ to reduce the size. Assuming a high dielectric constant material (PPO, Panasonic) as a material of the substrate, ε _r = 10.2, tan δ = 0.004, and a substrate thickness of 0.8 mm are used.

Next, the radiation characteristics when the power output from the power feeding matrix circuit of the example was fed to the antenna by an electromagnetic field simulator were analyzed by SONNET (moment method).
FIG. 3 is a graph showing the results of radiation characteristics when β is 0 ° and 90 °.
As a comparison value, the directivity of the conventional four-element beam switching antenna is shown in gray. This is a characteristic when the antenna shown in FIG.
The radiation characteristic is calculated with a horizontal angle θ at 5 ° intervals and marked with a marker. The vertical axis represents the maximum radiation level as 0 dB.

At β = 0 °, the beam direction is 0 °. The side lobe was -40.5 dB at a θ of 65 °, an improvement of 20.2 dB compared to the conventional 4-element system. The antenna gain of 6 elements is 0.5 dB lower than the conventional 4 elements. This is due to the power loss due to R _1.
At β = 90 °, the beam direction is −40 °. The side lobe was -27.5 dB at a θ angle of 30 °, an improvement of 17.8 dB compared to the conventional 4-element system.
The result of β = −90 ° is the same as the characteristic obtained by horizontally inverting the result of β = 90 °.

  From the above simulation results, it was confirmed that the side lobe was improved by about 20 dB in the matrix circuit of the example compared to the conventional circuit.

10 Feeding circuit for multi-beam antenna 20 Output port number conversion matrix circuit

Claims (4)

An output port number conversion matrix circuit connected to a multi-beam antenna feeding circuit,
Four or more input terminals connected one-to-one with the output terminals of the multi-beam antenna power supply circuit;
An even number of branches branched from the input terminal;
More output terminals than the number of input terminals by the number of branches,
A transmission line connected to each output terminal and performing impedance matching,
An output port number conversion matrix circuit characterized in that the power level supplied to the center output terminal is the highest, and the power level supplied decreases as the position of the output terminal moves away from the center. There are four input terminals,
There are six output terminals, each connected to a transmission line having a line length of λ / 4,
A pair of input terminals located at both ends are connected to the branch path,
2. The output according to claim 1, wherein a pair of output terminals located at both ends are further connected to a ground resistance (R ₁ ), a transmission line (L ₃ ) having a line length of 2λ, and the branch line, respectively. Port number conversion matrix circuit. Characteristic impedance Z ₀ of a transmission line (L ₀ ) having a line length λ / 4 connected to a pair of output terminals (Port 4 and Port 5) located in the center, a pair of outputs adjacent to the pair of output terminals located in the center Characteristic impedance Z ₁ of the transmission line (L ₁ ) with a line length λ / 4 connected to the terminals (Port 3 and Port 6), and the line length connected to a pair of output terminals (Port 2 and Port 7) located at both ends calculated by the characteristic impedance Z _2, equations 1 to 5 characteristic impedance Z ₃ and the ground resistor (R ₁₎ is below the transmission path line length of 2 [lambda] (L ₃₎ of the transmission line but λ / 4 (L ₂₎ The output port number conversion matrix circuit according to claim 2, wherein
[Formula 1]
[Formula 2]
[Formula 3]
[Formula 4]
[Formula 5]
  A phased array antenna antenna comprising the output port number conversion matrix circuit according to any one of claims 1 to 3 and a multi-beam antenna feeding circuit.