CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority to Japanese Patent Application Number 2018-179027 filed on Sep. 25, 2018. The entire contents of the above-identified application are hereby incorporated by reference.

BACKGROUND

Technical Field

The present disclosure relates to a scanning antenna, and more particularly relates to a scanning antenna in which an antenna unit (also referred to as an “element antenna”) has a liquid crystal capacitance (also referred to as a “liquid crystal array antenna”), and a TFT substrate used for such a scanning antenna.

Antennas for mobile communication and satellite broadcasting require functions that can change the beam direction (referred to as “beam scanning” or “beam steering”). As an example of an antenna (hereinafter referred to as a “scanning antenna” (scanned antenna) having such functionality, phased array antennas equipped with antenna units are known. However, phased array antennas of the related art are expensive, which is an obstacle for popularization as a consumer product. In particular, as the number of antenna units increases, the cost rises considerably.

Therefore, scanning antennas that utilize the high dielectric anisotropy (birefringence index) of liquid crystal materials (including nematic liquid crystals and polymer dispersed liquid crystals) have been proposed (JP 2007-116573 A, JP 2007-295044 A, JP 2009-538565 A, JP 2013-539949 A, WO 2015/126550, and R. A. Stevenson et al., “Rethinking Wireless Communications: Advanced Antenna Design using LCD Technology”, SID 2015 DIGEST, pp. 827-830.). Since the dielectric constant of liquid crystal materials has a frequency dispersion, in the present specification, the dielectric constant in a frequency band for microwaves (also referred to as the “dielectric constant for microwaves”) is particularly denoted as “dielectric constant M(εM)”.

JP 2009-538565 and R. A. Stevenson et al., “Rethinking Wireless Communications: Advanced Antenna Design using LCD Technology”, SID 2015 DIGEST, pp. 827-830. describe that an inexpensive scanning antenna can be obtained by using liquid crystal display device (hereinafter referred to as “LCD”) technology.

The applicant develops a scanning antenna which can be mass-manufactured by utilizing manufacturing techniques of LCDs of the related art. WO 2017/061527 of the application applied by the applicant discloses a scanning antenna which can be mass-manufactured by utilizing the manufacturing techniques of LCDs of the related art, a TFT substrate used for such a scanning antenna, and a manufacturing method and driving method of such a scanning antenna. For reference, the entire contents of the disclosures of WO 2017/061527 are incorporated herein.

SUMMARY

An object of the present disclosure is to provide a scanning antenna that can further improve the performance of a scanning antenna described in WO 2017/061527, and a TFT substrate used for such a scanning antenna.

According to the embodiments of the present disclosure, there are provided solutions according to the following items.

Item 1

A scanning antenna including:

a plurality of antenna units arranged in the scanning antenna;

a TFT substrate including a first dielectric substrate;

a slot substrate including a second dielectric substrate, and a slot electrode supported by a first main surface of the second dielectric substrate;

a liquid crystal layer provided between the TFT substrate and the slot substrate; and

a reflective conductive plate disposed opposing a second main surface of the second dielectric substrate opposite to the first main surface with a dielectric layer interposed between the reflective conductive plate and the second dielectric substrate, wherein each of the plurality of antenna units includes
a TFT supported by the first dielectric substrate,
a patch electrode electrically connected to a drain of the TFT,
a slot formed in the slot electrode corresponding to the patch electrode; and
a first region in which the patch electrode and the slot electrode overlap each other when viewed from a normal direction of the first dielectric substrate,
the plurality of antenna units includes a plurality of first antenna units and a plurality of second antenna units, and
a distance between the patch electrode and the slot electrode in the first region of the plurality of second antenna units is smaller than a distance between the patch electrode and the slot electrode in the first region of the plurality of first antenna units.
Item 2

The scanning antenna according to item 1,

wherein a thickness of the liquid crystal layer in the first region of the plurality of second antenna units is smaller than a thickness of the liquid crystal layer in the first region of the plurality of first antenna units.

Item 3

The scanning antenna according to item 1 or 2,

wherein a thickness of the patch electrode in the plurality of second antenna units is greater than a thickness of the patch electrode of the plurality of first antenna units.

Item 4

The scanning antenna according to any one of items 1 to 3

wherein a thickness of the slot electrode in the first region of the plurality of second antenna units is greater than a thickness of the slot electrode in the first region of the plurality of first antenna units.

Item 5

The scanning antenna according to any one of items 1 to 4,

wherein each of the plurality of first antenna units includes at least one first insulating layer formed in the first region between the first dielectric substrate and the patch electrode, each of the plurality of second antenna units includes at least one second insulating layer formed in the first region between the first dielectric substrate and the patch electrode, and a sum of thicknesses of the at least one second insulating layer is greater than a sum of thicknesses of the at least one first insulating layer.
Item 6

The scanning antenna according to any one of items 1 to 4,

wherein each of the plurality of second antenna units includes at least one insulating layer formed in the first region between the first dielectric substrate and the patch electrode, and each of the plurality of first antenna units does not include an insulating layer in the first region and between the first dielectric substrate and the patch electrode.
Item 7

The scanning antenna according to any one of items 1 to 6,

wherein each of the plurality of first antenna units includes at least one third insulating layer formed in the first region between the second dielectric substrate and the slot electrode, each of the plurality of second antenna units includes at least one fourth insulating layer formed in the first region between the second dielectric substrate and the slot electrode, and a sum of thicknesses of the at least one fourth insulating layer is greater than a sum of thicknesses of the at least one third insulating layer.
Item 8

The scanning antenna according to any one of items 1 to 6,

wherein each of the plurality of second antenna units includes at least one insulating layer formed in the first region between the second dielectric substrate and the slot electrode, and each of the plurality of first antenna units does not include an insulating layer in the first region and between the second dielectric substrate and the slot electrode.
Item 9

The scanning antenna according to any one of items 1 to 8,

wherein each of the plurality of first antenna units includes at least one first conductive layer formed in the first region between the first dielectric substrate and the patch electrode, each of the plurality of second antenna units includes at least one second conductive layer formed in the first region between the first dielectric substrate and the patch electrode, and a sum of thicknesses of the at least one second conductive layer is greater than a sum of thicknesses of the at least one first conductive layer.
Item 10

The scanning antenna according to any one of items 1 to 8,

wherein each of the plurality of second antenna units includes at least one conductive layer formed in the first region between the first dielectric substrate and the patch electrode, and each of the plurality of first antenna units does not include a conductive layer in the first region and between the first dielectric substrate and the patch electrode.
Item 11

The scanning antenna according to any one of items 1 to 10,

wherein a thickness of the second dielectric substrate in the first region of the plurality of second antenna units is greater than a thickness of the second dielectric substrate in the first region of the plurality of first antenna units.

Item 12

The scanning antenna according to item 11,

wherein the second dielectric substrate includes a plurality of recessed portions overlapping the first region of the plurality of second antenna units when viewed from a normal direction of the first dielectric substrate, formed on the first main surface of the second dielectric substrate.
Item 13

The scanning antenna according to any one of items 1 to 12,

wherein each of the plurality of antenna units includes a columnar spacer, and

a height of the columnar spacer of the plurality of first antenna units is approximately equal to a height of the columnar spacer of the plurality of second antenna units.

Item 14

The scanning antenna according to any one of items 1 to 13,

wherein the TFT substrate includes

a gate metal layer supported by the first dielectric substrate and including a gate electrode of the TFT,

a source metal layer supported by the first dielectric substrate and including a source electrode of the TFT,

a semiconductor layer of the TFT, supported by the first dielectric substrate,

a gate insulating layer formed between the gate metal layer and the semiconductor layer,

an interlayer insulating layer formed on the TFT, and

an additional insulating layer formed between the first dielectric substrate and the patch electrode,

each of the plurality of second antenna units includes the additional insulating layer in at least the first region, and

each of the plurality of first antenna units does not include the additional insulating layer.

Item 15

The scanning antenna according to any one of items 1 to 14,

wherein the TFT substrate includes

a gate metal layer supported by the first dielectric substrate and including a gate electrode of the TFT,

a source metal layer supported by the first dielectric substrate and including a source electrode of the TFT,

a semiconductor layer of the TFT, supported by the first dielectric substrate,

a gate insulating layer formed between the gate metal layer and the semiconductor layer, and

an interlayer insulating layer formed on the TFT, and

each of the gate insulating layer and/or the interlayer insulating layer includes a plurality of openings or a plurality of recessed portions overlapping with the patch electrode of each of the plurality of first antenna units when viewed from the normal direction of the first dielectric substrate.
Item 16

A TFT substrate including:

a dielectric substrate; and

a plurality of antenna unit regions arranged on the dielectric substrate,

wherein each of the plurality of antenna unit regions includes

a TFT supported by the dielectric substrate, and

a patch electrode electrically connected to a drain of the TFT, the plurality of antenna unit regions include a plurality of first antenna unit regions and a plurality of second antenna unit regions, and

a height of the patch electrode of the plurality of second antenna unit regions is greater than a height of the patch electrode of the plurality of second antenna unit regions.

Item 17

The TFT substrate according to item 16,

wherein a thickness of the patch electrode of the plurality of second antenna unit regions is greater than a thickness of the patch electrode of the plurality of first antenna unit regions.

Item 18

The TFT substrate according to item 16 or 17,

wherein each of the plurality of antenna unit regions includes a second region including two mutually opposing sides of the patch electrode when viewed from a normal direction of the dielectric substrate,

each of the plurality of first antenna unit regions includes at least one first insulating layer formed in the second region between the dielectric substrate and the patch electrode,

each of the plurality of second antenna unit regions includes at least one second insulating layer formed in the second region between the dielectric substrate and the patch electrode, and

a sum of thicknesses of the at least one second insulating layer is greater than a sum of thicknesses of the at least one first insulating layer.

Here, the two mutually opposing sides of the patch electrode refer to two sides opposing each other with a slot therebetween in the scanning antenna, and refers to the short sides of the substantially rectangular patch electrode (see, for example,FIGS. 4A and 4B).

Item 19

The TFT substrate of item 16 or 17,

wherein each of the plurality of antenna unit regions includes a second region including two mutually opposing sides of the patch electrode when viewed from a normal direction of the dielectric substrate,

each of the plurality of second antenna unit regions includes at least one insulating layer formed in the second region between the dielectric substrate and the patch electrode, and

each of the plurality of first antenna unit regions does not include an insulating layer in the second region and between the dielectric substrate and the patch electrode.

Item 20

The TFT substrate of any of items 16 to 19,

wherein each of the plurality of antenna unit regions includes a second region including two mutually opposing sides of the patch electrode when viewed from a normal direction of the dielectric substrate,

each of the plurality of first antenna unit regions includes at least one first conductive layer formed in the second region between the dielectric substrate and the patch electrode,

each of the plurality of second antenna unit regions includes at least one second conductive layer formed in the second region between the dielectric substrate and the patch electrode, and

a sum of thicknesses of the at least one second conductive layer is greater than a sum of thicknesses of the at least one first conductive layer.

Item 21

The TFT substrate of any of items 16 to 19,

wherein each of the plurality of antenna unit regions includes a second region including two mutually opposing sides of the patch electrode when viewed from a normal direction of the dielectric substrate,

each of the plurality of second antenna unit regions includes at least one conductive layer formed in the second region between the dielectric substrate and the patch electrode, and

each of the plurality of first antenna unit regions does not include a conductive layer in the second region and between the dielectric substrate and the patch electrode.

Item 22

The TFT substrate of any of items 16 to 21,

wherein each of the plurality of antenna unit regions includes a second region including two mutually opposing sides of the patch electrode when viewed from a normal direction of the dielectric substrate, each of the plurality of antenna unit regions including
a gate metal layer, supported by the dielectric substrate and including a gate electrode of the TFT,
a source metal layer supported by the dielectric substrate and including a source electrode of the TFT,
a semiconductor layer of the TFT supported by the dielectric substrate,
a gate insulating layer formed between the gate metal layer and the semiconductor layer,
an interlayer insulating layer formed on the TFT, and
an additional insulating layer formed between the dielectric substrate and the patch electrode,
each of the plurality of second antenna unit regions includes the additional insulating layer in at least the second region, and
each of the plurality of first antenna unit regions does not include the additional insulating layer.
Item 23

The TFT substrate of any of items 16 to 22, including a gate metal layer supported by the dielectric substrate and including a gate electrode of the TFT;

a source metal layer supported by the dielectric substrate and including a source electrode of the TFT;

a semiconductor layer of the TFT, supported by the dielectric substrate;

a gate insulating layer formed between the gate metal layer and the semiconductor layer; and

an interlayer insulating layer formed on the TFT,

wherein each of the gate insulating layer and/or the interlayer insulating layer includes a plurality of openings or a plurality of recessed portions overlapping with the patch electrode of each of the plurality of first antenna unit regions when viewed from a normal direction of the dielectric substrate.

According to the embodiments of the present disclosure, the performance of the scanning antenna can be further improved.

