Antenna chip

Abstract

An antenna chip includes: a first ground pad (30) and a second ground pad (40) aligned in a first direction orthogonal to a thickness direction of a substrate (20) with a gap (G) therebetween, the gap including a first gap (G1) and a second gap (G2) extending from the first gap in a second direction orthogonal to the thickness direction and different from the first direction; a signal pad (50) located within the first gap; a first antenna patch (71) constituting at least a part of an antenna; and a signal line (60) extending in the second direction from the signal pad and passing through the second gap, and configured to transmit an electrical signal input to the signal pad to the first antenna patch. A first boundary (B1) between the first ground pad and the first gap and a second boundary (B2) between the second ground pad and the first gap has an arc-shape concentric with the signal pad.

Description

ANTENNA CHIP

[0001] The present invention relates to an antenna chip.

[0002] In recent years, with the growing demand for increased data rates and larger bandwidth, millimeter-wave frequencies from 30 to 500 GHz became major candidates for the future development of wireless communication systems. To realize high data transmission rates and high-capacity networks, the design of integrated circuits at higher frequencies became necessary and led to the successful development of integrated circuit chips including power amplifiers (PA), low noise amplifiers (LNA), mixers, filters, etc. at various frequencies up to 500 GHz. At the same time, to radiate the amplified signal, the development of on-chip antennas, they are antenna chips, was also observed.

[0003] In general, the evaluation of the characteristics of the integrated circuit chips is obtained by the measurement of the chip’s output signal in a probing station (NPL1) where 3-point probes are used. In the case of the measurement of the chip, each of the input and the output that has the signal pad and the two ground pads is connected to the vector network analyzer (VNA) through the 3-point probe. The middle signal probe of the 3-point probe is in contact with the signal pad of the chip. The first and second outer ground probes of the 3-point probe are in contact with the first and second ground pads of the chip, respectively. In the evaluation of the characteristics of the antenna chip, the output side 3-point probe is replaced by a probe antenna at some distance from the antenna chip to collect the output signal radiated from the antenna chip.

[0004] Banan, B., Shokraneh, F., Berini, P., & Liboiron-Ladouceur, O. (2017). "Electrical performance analysis of a CPW capable of transmitting microwave and optical signals. " International Journal of Microwave and Wireless Technologies, 9(8), 1679-1686. doi:10.1017 / S1759078717000575

[0005] In the evaluation of the characteristics of the antenna chip, the radiation pattern of the output signal is measured. In the radiation pattern measurement, the angle of the probe antenna relative to the antenna chip is successively changed, and the antenna gain at each angle is measured by VNA using the probe antenna. One solution to achieve the angle changes is to rotate the antenna chip. In this case, the antenna chip rotates with respect to the 3-point probe. This is because the 3-point probe is usually configured in such a way that it cannot rotate.

[0006] When the antenna chip is rotated with respect to the 3-point probe, if the rotation angle increases, the ground probe of the 3-point probe may not be able to contact the ground pad, due to the shape of the ground pad on the antenna chip.

[0007] An objective of the present invention is to provide an antenna chip that can be connected to a connection object, such as a 3-point probe, even if the rotation angle to the connection object is increased.

[0008] An antenna chip according to the present invention is an antenna chip comprising: a substrate including a first main surface; a first ground pad and a second ground pad formed on the first main surface and aligned in a first direction orthogonal to a thickness direction of the substrate with a gap therebetween, the gap including a first gap and a second gap extending from the first gap in a second direction orthogonal to the thickness direction and different from the first direction; a signal pad formed on the first main surface and located within the first gap; a first antenna patch formed on the first main surface, located outside the gap, and constituting at least a part of an antenna; and a signal line formed on the first main surface, extending in the second direction from the signal pad and passing through the second gap, and configured to transmit an electrical signal input to the signal pad to the first antenna patch, wherein a first boundary between the first ground pad and the first gap has a shape of a portion of an outline of a circle or regular n-sided polygon (where n is an even number greater than or equal to 6) concentric with the signal pad, and a second boundary between the second ground pad and the first gap has a shape of a portion of an outline of a circle or regular m-sided polygon (where m is an even number greater than or equal to 6) concentric with the signal pad.

[0009] According to the above configuration, the antenna chip can be connected to the connection object even if the rotation angle of the antenna chip to the connection object is increased.

[0010] Fig. 1 is a plan view of an antenna chip according to an embodiment of the present invention.Fig. 1 is a bottom view of the antenna chip illustrated in Fig. 1.Fig. 3 is an enlarged plan view of a portion of the antenna chip illustrated in Fig. 1.Fig. 4 is a perspective view of a portion of the antenna chip illustrated in Fig. 1.Fig. 5 illustrates the configuration when measuring the radiation pattern of the antenna chip.Fig. 6 illustrates the configuration when measuring the radiation pattern of the antenna chip after rotation.Fig. 7 illustrates the radiation pattern simulations for each of the two different types of antennas (antenna_1 and antenna_2).Fig. 8 illustrates an antenna chip for a comparative example.Fig. 9 is a graph that illustrates simulation results of the impedance matching for signal pad side (Port 1) and the coplanar waveguide side (Port 2) for the frequency range of 150 GHz to 350 GHz.Fig. 10 is a graph that illustrates S parameters of the simulated signal pad and transition to the coplanar waveguide feed.Fig. 11 is a graph that illustrates simulation results of the characteristic impedance matching for signal pad side (Port 1) and the coplanar waveguide side (Port 2) for the frequency range of 150 GHz to 350 GHz, for different substrate materials.Fig. 12 is a schematic plan view of an antenna chip of a variation of the embodiment according to the present invention.Fig. 13 is an enlarged plan view of an antenna chip of a variation of the embodiment according to the present invention.Fig. 14 is a schematic enlarged plan view of an antenna chip of a variation of the embodiment according to the present invention.

[0011] An embodiment and variations thereof of the invention will be described with reference to the drawings. In each drawing, the same or similar elements are marked with the same reference sign. For multiple same elements, only some of them are signed. In drawings, some features are simplified and / or exaggerated for clarity.

[0012] As illustrated in Fig. 1 to Fig. 4, an antenna chip 10 according to this embodiment includes a substrate 20, ground pads 30 and 40, a signal pad 50, a signal line 60, antenna patches 71 and 72, a ground plane 80, and multiple vias 91 to 94.

[0013] The substrate 20 has a first main surface 21 and a second main surface 22 that is the back side of the first main surface 21. The main surfaces are the surfaces with the largest area among the respective surfaces of the substrate 20. On the first main surface 21, the ground pads 30 and 40, the signal pad 50, the signal line 60, and the antenna patch 71 are formed. On the second main surface 22, the antenna patch 72 and the ground plane 80 are formed.

[0014] The ground pads 30 and 40 are formed in a rectangular shape. The ground pads 30 and 40 are arranged to be aligned in a first direction orthogonal to the thickness direction of the substrate 20 with a gap G therebetween. The gap G extends in a second direction that is orthogonal to the thickness direction and different from the first direction. Here, the second direction is orthogonal to the first direction. The gap G is demarcated by and separates ground pads 30 and 40. Gap G includes gaps G1 to G3.

[0015] The circular signal pad 50 is located within the gap G1. The gap G1 is formed in an enlarged concentric shape of the signal pad 50. The boundary B1 between the gap G1 and the ground pad 30 has the shape of a first arc of a large diameter circle that is concentric with the signal pad 50 and has a larger diameter than the signal pad 50. The boundary B2 between the gap G1 and the ground pad 40 has the shape of a second arc of said large diameter circle, opposite to the first arc. The second arc is the arc opposite the first arc across the center of the large diameter circle. The width w1of a region between the signal pad 50 and the boundary B1 is constant. The width w1of a region between the signal pad 50 and the boundary B2 is also constant.

[0016] The gap G2 extends in the second direction from the gap G1. Linear signal line 60 extends from signal pad 50 in the second direction and passes through the gap G2. The second direction end of the signal line 60 is connected to the antenna patch 71 located outside the gap G. The signal pad 50, the signal line 60, and the antenna patch 71 are integrally formed as one conductive layer. The one conductive layer, the ground pad 30, and the ground pad 40 are formed apart from each other on the first main surface 21.

[0017] The gap G3 extends from the gap G1 in the direction opposite to the second direction. No conductors that transmit electrical signals, such as the signal pad 50 and the signal line 60, described below, are located in the gap G3.

[0018] A portion of the ground pad 30 and a portion of the ground pad 40 aligned in the first direction with the gap G1 therebetween are referred to as pad regions 31 and 41, respectively. A portion of the ground pad 30 and a portion of the ground pad 40 aligned in the first direction with the gap G2 therebetween are referred to as pad regions 32 and 42, respectively. A portion of the ground pad 30 and a portion of the ground pad 40 aligned in the first direction with a gap G3 therebetween are referred to as pad regions 33 and 43, respectively.

[0019] The part 35 at the boundary B1 side of the pad region 31, the part 45 at the boundary B2 side of the pad region 32, and signal pad 50 disposed between them constitute a coplanar waveguide CPW2. The parts 35 and 45 are arranged to be aligned in the first direction with a gap G1 therebetween. The pad regions 32 and 42 and the signal line 60 disposed between them constitute a coplanar waveguide CPW1.

[0020] The ground plane 80 formed on the second main surface 22 of the substrate 20 has a rectangular portion 81 covering the coplanar waveguide CPW1 from the second main surface 22 side and a pair of rectangular portions 82 and 83 extending in a direction opposite to the second direction from both end portions of the rectangular portion 81 in the first direction. The ground plane 80 has a shape that does not cover the coplanar waveguide CPW2 from the second main surface 22 side, that is, a shape that avoids the coplanar waveguide CPW2 when viewed from the thickness direction of the substrate 20.

[0021] The antenna patch 72 formed on the second main surface 22 of the substrate 20 extends from the ground plane 80 in the second direction. The antenna patch 72 and the ground plane 80 are integrally formed as one conductive layer. The antenna patch 72 and the antenna patch 71 described above constitute an antipodal Vivaldi antenna.

[0022] The plurality of vias 91 to 94 penetrate the substrate 20. The plurality of vias 91 and 92 electrically connect the ground pad 30 to the ground plane 80. The plurality of vias 93 and 94 electrically connect the ground pad 40 to the ground plane 80.

[0023] Viewed from the thickness direction of the substrate 20, the plurality of vias 91 are aligned in the first direction at a position overlapping the pad region 32 of the ground pad 30, and the plurality of vias 92 are aligned in the second direction at a position overlapping a region of the pad region 31 other than the part 35. The plurality of vias 91 electrically connect the pad region 32 to the rectangular portion 81 of the ground plane 80. The plurality of vias 92 electrically connect the pad region 31 to the rectangular portion 82 of the ground plane 80.

[0024] Viewed from the thickness direction of the substrate 20, the plurality of vias 93 are aligned in the first direction at a position overlapping the pad region 42 of the ground pad 40, and the plurality of vias 94 are aligned in the second direction at a position overlapping a region of the pad region 41 other than the part 45. The plurality of vias 93 electrically connect the pad region 42 to the rectangular portion 81 of the ground plane 80. The plurality of vias 94 electrically connect the pad region 41 to the rectangular portion 83 of the ground plane 80.

[0025] The vias 91 to 94 limit the area of electromagnetic wave generated by electrical signal propagating through the signal line 60. The additional role of the vias 91 to 94 in millimeter-wave frequencies is to limit the leakage of the electromagnetic wave through the substrate 20 and absorb the undesired substrate resonance modes and various parasitic that are often generated during the operation of the antenna chip 10 at millimeter-band frequencies.

[0026] The method of measuring the radiation pattern of the radiated signal radiated by the antenna 70 of the antenna chip 10 will be described. First, a 3-point probe 952 is connected to the antenna chip 10 placed in the basic position (0-degree rotational angle position) illustrated in Figure 5. This connection brings the signal probe 952A, ground probe 952B, and ground probe 952C of the 3-point probe 952 into contact with the signal pad 50, ground pad 30, and ground pad 40 of the antenna chip 10, respectively. This contact grounds the ground pads 30 and 40, the ground plane 80 connected to them via vias 91-94, and the antenna patch 72 connected to the ground plane 80. A VNA 951 sends an electrical signal for radiation pattern measurement via the signal probe 952A to input to the signal pad 50. The input electrical signal is transmitted to the antenna patch 71 via the signal pad 50 of the coplanar waveguide CPW2 and the signal line 60 of the coplanar waveguide CPW1. Antenna 70, which includes antenna patches 71 and 72, radiates the electrical signal transmitted to antenna patch 71 in the form of electromagnetic wave, such as millimeter wave. The electromagnetic wave is radiated in a radiation pattern PT. The VNA 951 collects this electromagnetic wave with the probe antenna 953, with area R as the measurement area, and measures the antenna gain based on this electromagnetic wave.

[0027] The antenna chip 10 is then rotated and the three-point probe 952 is reconnected, as illustrated in Fig. 6. The center of rotation of the antenna chip 10 is the center of the signal pad 50. As the antenna chip 10 rotates, the position and orientation of the 3-point probe 952 remain the same. The antenna gain is then measured in the same process as in Figure 5. The antenna chip 10 is rotated multiple times, and the antenna gain is measured each time it is rotated. The antenna chip 10 may be rotated at a rotation angle between that illustrated in Figure 5 and that illustrated in Figure 6.

[0028] The position of the probe antenna 953 changes with the angle of rotation of the antenna chip 10. The position of the probe antenna 953 relative to the antenna chip 10 may be determined based on the characteristics of the probe antenna 953.

[0029] The contact position of the signal probe 952A is the center of the signal pad 50. Therefore, when the antenna chip 10 is rotated, the contact position of the signal probe 952A remains unchanged at the center of signal pad 50. The contact positions of the ground probes 952B and 952C will change. Here, the boundaries B1 and B2 defining the ground pads 30 and 40, respectively, are arc-shaped, concentric with the signal pad 50 and larger in diameter than the signal pad 50, as described above. Therefore, the respective contacts between the ground probes 952B and 952C and the ground pads 30 and 40 are maintained even when the rotation angle of the antenna chip 10 is increased. Here, the antenna chip 10 can be rotated a wide range of ±70° to 75°, or 140° to 150° total. With a small step of rotation angle, precise measurements of the radiation pattern in the total range of 140° to 150° are possible.

[0030] Fig. 7 illustrates simulated radiated signals (electromagnetic waves) from two antipodal Vivaldi antennas tuned for a peak gain at 265 GHz. The radiation patterns in the x-y plane (antenna plane) are illustrated in Fig. 7. Hereafter, the antenna in the simulation on the left side of Figure 7 is referred to as antenna_1 and the antenna in the simulation on the right side as antenna_2.

[0031] In Antenna_1 radiation pattern, the maximum simulated antenna gain is about 10.2 dBi, while in Antenna_2, the maximum gain is about 10.3 dBi. In the simulation, for a similar gain of Antenna_1 and Antenna_2 at the same frequency of 265 GHz, the shape of the radiation pattern changes, illustrating different gain values at the same radiation angles. For example, at 60° and 120°, both antennas illustrate a similar gain of about 7.5 dBi. With a further change of the angle to 30° and 150°, the simulated results differ, illustrating antenna gain of about 1-2 dBi for Antenna_1, and about 5 dBi for Antenna_2. It can be concluded that Antenna_2 is more broadband than Antenna_1 in this case. Although, the value of 5 dBi is twice smaller than the peak gain value, at 265 GHz it is still considered to be usable. Therefore, to confirm the simulated results and broadband characteristics of the fabricated Antenna_2, the measurement at larger angles is necessary. With the respective shapes of signal pad 991 and ground pads 992 and 993 for the comparative example as illustrated in Figure 8, ground probes 952B or 952C cannot contact ground pads 992 or 993 when measuring at large angles such as the aforementioned 30 and 150 degrees. This may result in changes in impedance, etc., and accurate measurements may not be realized. However, the above structure of antenna chip 10 (especially the arc shape of boundaries B1 and B2) allows accurate measurement because the respective contact between ground probes 952B and 952C and ground pads 30 and 40 is ensured.

[0032] The input impedance may be tuned to 50 Ω to reduce the signal input loss (insertion loss). Also, the coplanar waveguides CPW1 and CPW2 may also possess matched impedance to avoid large reflections and mismatch of the signal.

[0033] In this embodiment, the geometry of the conductive (metal) layers (the pads 30, 40, and 50, and signal line 60) and the waveguide CPW1 and CPW2 are first designed and then tuned to exhibit characteristic impedance of Z0= 50 Ω, for the indium phosphide substrate 20 (εr= 12.3), a substrate thickness of tSUB= 55 μm, a metal layer thickness of tM= 4 μm, and a via radius of RVIA= 30 μm, which are standard parameters for a high-frequency circuit for wireless communication applications. While the dielectric constant εrdoes not change, the changes in the thickness of the substrate 20 and metal layer will cause a significant change in the impedance; thus, should be considered in the initial design of the pads.

[0034] In this embodiment, the coplanar waveguide CPW2 can be considered a coplanar waveguide without backside ground plane, the coplanar waveguide CPW1 can be considered a coplanar waveguide with a backside ground plane 80. The impedance is adjusted by the shape of the ground plane 80. Generally, the impedance of the coplanar waveguide can be calculated using equation 1. In equation 1, εeffis the effective dielectric constant, K(k) is the elliptical integral, and K(k’) is the complement of K(k).

[0035] The effective dielectric constant can be calculated using equation 2. In equation 2, “K” is the complete elliptic integral of the first kind, and “k”, “k1”, “ k’ ”, and “ k1’ ” are equal. In equation 3 to 5, “s” is the line width (2*R or s in Fig.3), “w” is the gap width (w1or w2in Fig.3), and “h” is the thickness of the substrate (tSUB).

[0036] In this embodiment, for a 55-μm-thick InP substrate (εr= 12.3), a characteristic impedance of 50 Ω was achieved for the R = 20 μm, w1= 30 μm, s = 9 μm, and w2= 10 μm.

[0037] Next, the results of the electromagnetic wave simulation based on the structure of a portion of the antenna chip 10 illustrated in Fig. 4 will be described. The signal input was applied to the pad cross-section in the center plane of the signal pad 50 (Port1). The output signal was collected from the coplanar waveguide CPW1 with the ground (Port2).

[0038] Fig. 9 illustrates the simulation results of the impedance versus frequency measurements for the beforementioned dimensions（R, w1, s, and w2,etc.） of the coplanar waveguides CPW1 and CPW2. As can be seen, a stable characteristic impedance value of about 50 Ω was achieved for a large frequency range from 150 GHz to 350 GHz, for both Port 1(input) and Port 2(output), which allows for stable measurements of the characteristics of the antenna chip 10 at various frequencies. The operation at a wide range of frequencies allows the usage of once-designed coplanar waveguides CPW1 and CPW2 in various devices, with the assumption that the substrate material and substrate thickness will not change.

[0039] Fig. 10 illustrates the S parameters extracted from the simulation. Parameters of the signal transmission (S21 and S12) illustrate the insertion loss below 1 dB in the frequency range of 150-350 GHz. The S11 and S22 parameters illustrate values below -15 dB in the frequency range of 150-350 GHz; thus, it is concluded that the return loss of the system is acceptable for the antenna design, which typically requires values below -10 dB. Furthermore, the designed coplanar waveguides CPW1 and CPW2 can work as an input signal pad and the output signal pad in the case the antenna works as a transceiver.

[0040] According to this embodiment, the circular signal pad 50 and the ground pads 30 and 40 with arc contours (boundaries B1 and B2) that are concentric and large in diameter with the signal pad 50 allow keeping the same dimensions (R, w1, etc.) of the waveguide in the plane including contact points between the 3-point probe 952 and the pads 30 to 50, even at much larger measurement angles. This reduces some discrepancies and impedance mismatch.

[0041] The material of substrate 20 may be replaced by other materials different from indium phosphide. In Table 1, the summarized dimensions of the coplanar waveguides CPW1 and CPW 2 extracted from the simulation results when Si, SiN, GaAs, GaN, InP, and Ge are used as the substrate materials are illustrated.

[0042] Assuming the same thickness of the substrate tSUB, the dielectric constant of the material is the main parameter that influences the dimensions. Although, many parameters can be arbitrarily chosen, generally, lower dielectric constant materials require larger signal pad 50 and signal line 60 (R and s) than the materials with higher dielectric constants εr, while the spacings between the conductive layers of the coplanar waveguides CPW1 and CPW2 (w1and w2) is decreased with lower εr. The size of the signal pad 50 should be large enough to allow for contact with the signal probe 952A.

[0043] Fig. 11 illustrates, for each material, the value of the characteristic impedance of the structure in Figure 4 with the dimensions in Table 1. As illustrated, in every case, stable values of the impedance around 50 Ω were achieved, illustrating that the coplanar waveguides CPW1 and CPW2 can easily be tuned to exhibit desired values of impedance, also different from 50 Ω for a certain application, for a variety of substrates. The substrate material may be a polymer or other material.

[0044] The specific configuration of the antenna chip is not limited to the structure described above. For example, a processing circuit located between the signal line 60 and the antenna patch 71 and configured to process the electrical signal transmitted from the signal line 60 to the antenna patch 71 may be provided. The processing circuit may include one or any combination of a power amplifier, a low noise amplifier, a mixer, and a filter. The antenna 70 can also be changed to any antenna. In the antenna chip 10, the antenna 70 is composed of two antenna patches 71 and 72, but the antenna may be composed of a single antenna patch.

[0045] Fig. 12 illustrates an antenna chip 100 with processing circuit 190 and an antenna 70 replaced by a Vivaldi antenna 170 consisting of a single antenna patch. In Fig. 12, the processing circuit 190 is drawn as a simplified block. In the case of antenna chip 100, the electrical signal after processing (e.g., after amplification) by the processing circuit 190 transmitted to the Vivaldi antenna 170 as the electrical signal transmitted from signal line 60 to the Vivaldi antenna 170. In Fig. 12, the ground plane 80 does not cover the processing circuit 190 from the second main surface 22 side, but a ground plane may be provided to further cover the processing circuit 190.

[0046] The shapes of boundaries B1 and B2 can also be changed to any shape. Boundary B1 may have the shape of a portion of the outline of a regular n-sided polygon (where “n” is an even number greater than or equal to 6) concentric with the signal pad, and the boundary B2 may have the shape of a portion of the outline of a regular m-sided polygon (where “m” is an even number greater than or equal to 6) concentric with the signal pad. “n” and “m” may be the same or different. Such a shape also ensures the connection between the 3-point probe and the antenna chip when the rotation angle of the antenna chip with respect to the 3-point probe is increased.

[0047] The signal pad 50 may be a regular n-sided polygon, and the boundaries B1 and B2 may be the shapes of portions of the outline of the concentric enlarged shape of the signal pad 50. By matching the shapes of signal pad 50 and boundaries B1 and B2 in this way, the outline of signal pad 50 and boundaries B1 and B2 can be parallel, and some discrepancies and impedance mismatch, as described above, when the antenna chip is rotated, is reduced to some extent. Figure 13 illustrates the signal pad 50 and ground pads 30 and 40 (boundaries B1 and B2) when n = 8.

[0048] The antenna chip may be connected to any object other than the 3-point probe 952.

[0049] As illustrated in Fig. 13, A resistor 290 may be provided with first and second ends connected to the ground pads 30 and 40, respectively. In Fig. 13, resistor 290 is depicted by a circuit symbol. The resistor 290 is a lumped resistor that dissipates the excess energy from the ground pads 30 and 40. In some designs, during the operation of the antenna chip, especially at higher frequencies, the shapes of the ground pads 30 and 40 might cause a gradual accumulation of the electric field and the power in the pad area, due to the resonance generation in the gaps between the signal pad 50 and ground pads 30 and 40, which then can affect the measured characteristics and the performance. Here, the resistor 290 is connected to the pad regions 33 and 43. The resistor 290 has a greater resistivity value than ground pads 30 and 40. The resistor 290 also allows the performance increase of the Antenna chip by reducing the S11 characteristics.

[0050] Although the invention has been described above with reference to embodiments and variations, the invention is not limited to the above embodiments and variations. For example, the present invention includes various modifications to the above embodiments and variations that can be understood by those skilled in the art within the scope of the technical concept of the invention. Each of the configurations listed in the above embodiments and variations can be combined as appropriate to the extent that there is no contradiction.

[0051] 10...antenna chip, 20...substrate, 21...first main surface, 22...second main surface, 30...ground pad, 31 to 33...pad regions, 35 ...part, 40...ground pad, 41 to 43...pad regions, 45...part, 50...signal pad, 60...signal line, 70 ...antenna, 71-72...antenna patch, 80...ground plane, 81-83...rectangular portions, 91-94...via, 100... Antenna chip, 170...Vivaldi antenna, 190...processing circuit, 290...resistor, 952...3-point probes, 952A...signal probe, 952B-952C...ground probes, 953...probe antenna, 991...signal pads, 992 to 993...ground pads, B1 to B2...boundaries, CPW1 to CPW2...coplanar waveguides, G...gap, G1-G3...gap, PT...radiation pattern, R...region.

Claims

1. An antenna chip comprising: 　　　　a substrate including a first main surface; 　　　　a first ground pad and a second ground pad formed on the first main surface and aligned in a first direction orthogonal to a thickness direction of the substrate with a gap therebetween, the gap including a first gap and a second gap extending from the first gap in a second direction orthogonal to the thickness direction and different from the first direction; 　　　　a signal pad formed on the first main surface and located within the first gap; 　　　　a first antenna patch formed on the first main surface, located outside the gap, and constituting at least a part of an antenna; and 　　　　a signal line formed on the first main surface, extending in the second direction from the signal pad and passing through the second gap, and configured to transmit an electrical signal input to the signal pad to the first antenna patch, wherein 　　　　a first boundary between the first ground pad and the first gap has a shape of a portion of an outline of a circle or regular n-sided polygon (where n is an even number greater than or equal to 6) concentric with the signal pad, and 　　　　a second boundary between the second ground pad and the first gap has a shape of a portion of an outline of a circle or regular m-sided polygon (where m is an even number greater than or equal to 6) concentric with the signal pad.

2. The antenna chip according to claim 1, wherein 　　　　the signal pad is circular, 　　　　the first boundary has a shape of a first arc of a large diameter circle that is concentric with the signal pad and has a larger diameter than the signal pad, and 　　　　the second boundary has a shape of a second arc of the large diameter circle opposite to the first arc.

3. The antenna chip according to claim 1, further comprising 　　　　a ground plane formed on a second main surface that is the back side of the first main surface of the substrate, wherein 　　　　the ground plane is formed in a shape that covers, from the second main surface side, a first coplanar waveguide including the signal line through the second gap and a portion of each of the first and second ground pads aligned in the first direction with the second gap therebetween.

4. The antenna chip according to claim 3, wherein 　　　　the ground plane is formed in a shape that, when viewed from the thickness direction, avoids a second coplanar waveguide including the signal pad and a portion of each of the first and second ground pads aligned in the first direction with the first gap therebetween.

5. The antenna chip according to claim 3, further comprising 　　　　one or more first vias that penetrate the substrate and electrically connect the ground plane to the first ground pad, and 　　　　one or more second vias that penetrate the substrate and electrically connect the ground plane to the second ground pad.

6. The antenna chip according to claim 3, further comprising 　　　　a second antenna patch formed on the second main surface and electrically connected to the ground plane, wherein 　　　　the first antenna patch and the second antenna patch constitute an antipodal Vivaldi antenna.

7. The antenna chip according to claim 1, further comprising 　　　　a processing circuit located between the signal line and the first antenna patch and configured to process the electrical signal transmitted from the signal line to the first antenna patch.

8. The antenna chip according to claim 1, further comprising 　　　　a resistor including first and second ends connected to the first and second ground pads, respectively.

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