JP5937536B2 - Antenna device - Google Patents

Description

  The present invention relates to an antenna device used for a radio wave radar.

  In radio wave radar, one of the techniques for controlling antenna directivity is known to reduce the side lobe level by providing a guide made of a metal wall or the like on the side of the radiating element (for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 2012-4700

  By the way, in recent years, since the manufacture is easy and the cost is low, an antenna device configured by using a microstrip antenna as a radiating element and using a microstrip line as a feeding line is widely used.

  However, in such an antenna device composed of a microstrip antenna and a microstrip line, an unnecessary radiation component generated from the feed line causes a side lobe increase, which is one of the causes of deterioration of antenna directivity.

However, in the conventional apparatus that controls the radiation component from the radiation element, there is a problem that the influence of the above-described unnecessary radiation cannot be suppressed.
In order to solve the above problems, an object of the present invention is to suppress the influence of unnecessary radiation in an antenna device and improve the characteristics of the antenna device.

  In the antenna device of the present invention, a radiating element group and a feed line are formed on the same surface of the substrate. Here, the part of the power feeding line wired along the outer edge of the part where the radiating element group is formed is called a main line.

  In addition, a shielding part is provided on the substrate. The shielding portion includes a side wall portion standing on the opposite side of the radiating element group along the main line and an upper wall portion projecting from the side wall portion to the upper portion of the feeder line.

  According to the antenna device of the present invention configured as described above, not only can the influence of unwanted radiation from the main line of the feeder line be suppressed by the shielding part, but also the radiation characteristic of unwanted radiation is controlled by the shielding part. By utilizing the unnecessary radiation, side lobes caused by radiation from the radiating element group can be suppressed, that is, the characteristics of the device can be improved.

It is a whole block diagram of the antenna device of 1st Embodiment. It is explanatory drawing which shows the structure and effect | action of a shielding part. It is a graph which shows the directivity of an unnecessary radiation source. It is a graph which shows the directivity of the whole transmission antenna part. It is a graph which shows the relationship between the height of a side wall part, and the radiation level to the receiving antenna side direction. It is a block diagram which shows the structure of the transmission antenna part periphery of the antenna device of 2nd Embodiment. It is explanatory drawing which shows the structure of the shielding part in 2nd Embodiment, (a) is the figure seen from the side in which the receiving antenna part is located in FIG. 7, (b) is the sectional drawing. It is a graph which shows the directivity of the whole transmission antenna part in 2nd Embodiment. It is explanatory drawing which shows the modification of the shielding part shown in 2nd Embodiment. It is explanatory drawing which illustrates the other shape of a shielding part.

Embodiments of the present invention will be described below with reference to the drawings.
[First Embodiment]
<Configuration>
The antenna device 1 is used as an antenna for an in-vehicle radar, and includes a transmission antenna unit 10, a reception antenna unit 20, and a shielding unit 30, as shown in FIG. These parts are formed on one surface (front surface) of the rectangular dielectric substrate 3. A ground pattern (not shown) is formed on the entire other surface (back surface) of the dielectric substrate 3. Hereinafter, the longitudinal direction of the dielectric substrate 3 is also referred to as the X-axis direction, the short direction is also referred to as the Y-axis direction, and the direction orthogonal to the plane is also referred to as the Z-axis direction.

  The transmitting antenna unit 10 includes a radiating element group SA composed of a plurality of radiating elements 11 arranged two-dimensionally along the X-axis direction and the Y-axis direction, and power feeding to the radiating elements 11 constituting the radiating element group SA. It is comprised with the electric power feeding line 12 which performs. The feed line 12 extends along the X-axis direction and the main line 12a wired along the outer edge (Y-axis direction) of the radiating element group SA formation side from the radiating element group SA formation site to the receiving antenna unit 20 side. Each radiating element 11 is provided with a branch line 12b that is wired along the radiating element array and has one end connected to the main line 12a, and each radiating element 11 constituting the radiating element array is connected to the radiating element array. The corresponding branch line 12b is connected via an individual line.

  The reception antenna unit 20 includes n (n is 2 or more) unit antennas RAi (i = 1 to n) arranged along the X-axis direction. The unit antenna RAi has the same configuration, and includes a plurality of radiating elements 21 formed in a rectangular shape and a feeding line 22 that feeds power to each radiating element 21. The radiating elements 21 are arranged in two rows along the Y-axis, and a feed line 22 is wired between the two radiating element rows, and is connected to the feed line 22 via individual lines.

  The radiating elements 11, 21 and the feed lines (including individual lines) 12 and 22 constituting the transmitting antenna unit 10 and the receiving antenna unit 20 are a microstrip antenna together with a ground pattern on the back surface of the dielectric substrate 3. And a microstrip line.

  The shielding portion 30 is made of a metal plate having a cross-sectional shape formed in an L-shape, and as shown in FIG. 2A, along the main line 12 a of the feed line 12 that constitutes the transmitting antenna unit 10, the main line 12 a. Further, a side wall portion 31 erected on the receiving antenna unit 10 side and an upper wall portion 32 projecting from the tip of the side wall portion 31 to the upper portion of the main line 12a are provided. Hereinafter, the main line 12a of the feed line 12 is also referred to as an unnecessary radiation source 12a.

<Effect>
In the antenna device 1 configured as described above, of the unwanted radiation from the unwanted radiation source 12a,
The component toward the reception antenna side direction that is the direction in which the reception antenna unit 20 is formed (the right direction in FIG. 2A) is shielded and suppressed by the shielding unit 30. Of the unwanted radiation from the unwanted radiation source 12a, the component toward the direction of the transmission antenna, which is the direction in which the radiation element group SA of the transmission antenna unit 10 is formed (the left direction in FIG. 2A), is shown in FIG. As shown in FIG. 2B, the direct wave from the unnecessary radiation source 12a and the reflected wave reflected by the shielding unit 30 interfere with each other and are suppressed. Further, the unwanted radiation component directed toward the transmitting antenna side of the radiation component from the radiation element group SA is directed in the same direction as the unwanted radiation component and interferes with the radiation component forming the side lobe. Reduce strength.

  As described above, according to the antenna device 1, not only the influence of the unnecessary radiation from the unnecessary radiation source 12a can be suppressed, but also the side lobes can be suppressed by using the unnecessary radiation, that is, the characteristics of the device can be improved. Can be made.

<Simulation>
The results of the simulation are shown in FIGS.
However, here, assuming that a millimeter wave of 76.5 GHz (wavelength λ = 3.92 mm) is used, the height of the side wall portion 31 is L1 = 3 [mm], and the overhang length of the upper wall portion 32 is L2 = The interval from the unwanted radiation source 12a to the side wall portion 31 was set to 6 [mm] and W1 = 4.7 [mm].

  FIG. 3 is a graph obtained by simulating the directivity of the unnecessary radiation source 12a alone. The solid line indicates the presence of the shielding part 30, and the dotted line indicates the case where the shielding part 30 is not present. From the figure, it can be seen that the presence of the shielding portion 30 significantly suppresses unnecessary radiation from the front direction toward the receiving antenna side, and concentrates in the direction toward the transmitting antenna.

  FIG. 4 is a graph in which the directivity of the entire transmission antenna unit 10 is obtained by simulation. A solid line indicates the case with the shielding part 30 and a dotted line indicates a case without the shielding part. From the figure, the side lobe in the direction of the reception antenna (left side in the figure) with respect to the main lobe is reduced by shielding unwanted radiation from the unwanted radiation source 12a in that direction by the shielding unit 30, and the transmission antenna. It can be seen that the side lobe in the lateral direction (right side in the figure) is reduced by interfering with unwanted radiation from the unwanted radiation source 12 a guided by the shielding unit 30.

  FIG. 5 is a graph obtained by simulating the radiation level in the direction of the receiving antenna of the transmitting antenna unit 10 by changing the height L1 of the side wall 31. FIG. From the figure, it can be seen that the shielding effect in the direction of the receiving antenna becomes maximum at around 3 mm (3λ / 4).

  That is, when designing the radar apparatus 1, L1 = 3λ / 4 is set, and the simulation results are used so that the other parameters (L2, W2) satisfy the conditions (1) and (2) below. Can be set.

(1) Unnecessary radiation directed from the unnecessary radiation source 12a toward the transmitting antenna side efficiently cancels the direct wave from the unnecessary radiation source 12a and the reflected wave reflected by the shielding unit 30.
(2) Unnecessary radiation directed from the unnecessary radiation source 12a toward the transmitting antenna side and unnecessary radiation forming a side lobe in the directivity of the radiation element 11 efficiently cancel each other.

[Second Embodiment]
A second embodiment will be described.
In the antenna device 2 of the present embodiment, since the shape of the shielding part 40 is only different from the shielding part 30 of the antenna device 1, this different part will be mainly described.

In the antenna device 2, the shielding unit 40, as shown in FIG.
Unnecessary from the base 41 having a shape surrounding the receiving antenna unit 20 except for the side facing the receiving antenna unit 20 (hereinafter referred to as the open side), the side wall 42 erected on the open side end of the base 41, and the tip of the side wall 42 And an upper wall portion 43 projecting from the upper portion of the radiation source 12a. In addition, each part 41-43 which comprises the shielding part 40 is comprised integrally by processing and forming a metal plate. However, as shown in FIG. 7, the side wall portion 42 is integrated with the base portion 41 in the vicinity of both ends in the longitudinal direction (Y-axis direction), and in the other portions, the lower end of the side wall portion 42 and the dielectric substrate are integrated. 3 is formed so that a gap (hereinafter referred to as a side wall lower gap) 44 is formed.

  In the antenna device 2 configured as described above, the size of the side wall gap 44 is adjusted as appropriate, and the amount of radio wave leakage from the side wall gap 44 is adjusted to thereby improve the side directivity characteristics of the transmitting antenna unit 10. The balance of the lobes can be adjusted.

In addition, the size of the side wall lower gap 44 may be set to a size that can effectively suppress the side lobe from the result obtained by simulation or the like.
FIG. 8 is a graph obtained by simulating the directivity of the transmitting antenna unit 10 as a whole. The solid line indicates the case where there is no side wall gap 44 and the dotted line indicates the case where the side wall gap 44 exists. Here, the size of the side wall lower gap 44 is W2 = 0.3 [mm].

<Modification>
In the antenna device 2, the shielding unit 40 is configured to form a side wall lower gap 44. Further, as illustrated in FIG. 9, the protruding direction of the upper wall part 43 is formed above the side wall lower gap 44. A protruding portion 45 protruding from the side wall portion 42 toward the opposite side may be provided, and the length L3 in the protruding direction of the protruding portion 45 may be set to an odd multiple of λ / 4. As a result, it is possible to adjust the radiation characteristics of unwanted radiation from the unwanted radiation source 12a, and thus the directivity of the entire transmission antenna unit 10, while suppressing leakage of radio waves from the side wall lower gap 44.

[Other Embodiments]
As mentioned above, although embodiment of this invention was described, it cannot be overemphasized that this invention can take a various form, without being limited to the said embodiment.

For example, at least a part of the configuration of the above embodiment may be replaced with a known configuration having a similar function.
In the embodiment described above, the side walls 31 and 42 of the shielding parts 30 and 40 are formed linearly along the main line (unnecessary radiation source) 12a of the power supply line 12, but like the shielding part 50 shown in FIG. Further, the side wall portion may be formed in a shape curved with respect to the main line 12a, and the shape of the side lobe in the directivity of the entire transmission antenna 10 may be controlled more precisely by this shape.

  DESCRIPTION OF SYMBOLS 1, 2 ... Antenna apparatus 3 ... Dielectric board 10 ... Transmitting antenna part 11, 21 ... Radiating element 12, 22 ... Feed line 12a ... Main line (unnecessary radiation source) 12b ... Branch line 20 ... Receiving antenna part 30, 40, 50 ... Shielding part 31, 42 ... Side wall part 32, 43 ... Upper wall part 41 ... Base part 43 ... Upper wall part 44 ... Side wall lower gap 45 ... Projection part

Claims (8)

A substrate on which a radiating element group composed of a plurality of radiating elements and a feeding line for feeding power to each radiating element constituting the radiating element group are formed on the same surface;
Side walls erected on the opposite side of the radiating element group across the main line along the main line, the main line being a portion of the feeder line wired along the outer edge of the portion where the radiating element group is formed A shielding portion that shields radio waves, and an upper wall portion that projects from the side wall portion to the upper portion of the power supply line,
An antenna device comprising:   2. The antenna device according to claim 1, wherein a wavelength of a signal transmitted or received by the radiating element group is λ, and a height of the side wall portion is set to 3λ / 4.   The said shielding part is formed in the shape which has the clearance gap for adjusting the leakage amount of the unnecessary radiation from the said main line between a side wall part and a board | substrate, The Claim 1 or Claim 2 characterized by the above-mentioned. The antenna device described.   The antenna device according to claim 3, further comprising a protruding portion protruding in an opposite direction to the upper wall portion at an upper portion of the gap.   5. The length of the protruding portion in the protruding direction is set to an odd multiple of λ / 4, where λ is a wavelength of a signal transmitted or received by the radiating element group. Antenna device.   The antenna device according to claim 1, wherein the side wall portion of the shield has a curved shape.   The antenna device according to claim 1, wherein the radiating element group constitutes a transmission antenna.   The antenna apparatus according to claim 7, wherein a reception antenna is formed on the substrate on a side opposite to the radiating element group with the shielding portion interposed therebetween.