Liquid crystal antenna unit and liquid crystal phased array antenna
A liquid crystal antenna unit and a liquid crystal phased array antenna are provided. The liquid crystal antenna unit includes: a first substrate, a second substrate opposite to the first substrate, a liquid crystal layer between the first substrate and the second substrate, a transmission line on a first surface and extending in a first direction along the first surface, a first antenna oscillator on the first surface and arranged as an elongated dipole extending in a second direction along the first surface, a second antenna oscillator on a surface of the second substrate distal to the first substrate and at a position corresponding to the first antenna oscillator, and a ground electrode on a surface of the first substrate distal to the second substrate.
1. A liquid crystal antenna unit, comprising:
a first substrate;
a second substrate opposite to the first substrate;
a liquid crystal layer between the first substrate and the second substrate;
a transmission line on a first surface and arranged to extend in a first direction along the first surface, wherein the first surface is one of a surface of the first substrate proximal to the second substrate and a surface of the second substrate proximal to the first substrate;
a first antenna oscillator on the first surface and arranged as an elongated dipole extending in a second direction along the first surface, wherein the dipole comprises two poles spaced apart from each other by a gap, and the first antenna oscillator is configured to couple an electromagnetic wave between the two poles and the transmission line at the gap;
a second antenna oscillator on a surface of the second substrate distal to the first substrate and at a position corresponding to the first antenna oscillator, wherein the second antenna oscillator has an elongated shape extending in the second direction along the surface of the second substrate distal to the first substrate, and a length of the second antenna oscillator is less than a length of the first antenna oscillator; and
a ground electrode on a surface of the first substrate distal to the second substrate, wherein the ground electrode comprises an elongated electrode portion at a position corresponding to the first antenna oscillator, the elongated electrode portion extends in the second direction along the surface of the first substrate distal to the second substrate, and a length of the elongated electrode portion is greater than the length of the first antenna oscillator.
2. The liquid crystal antenna unit according to claim 1 , wherein the length of the second antenna oscillator is 0.7 to 0.9 times the length of the first antenna oscillator, and the length of the first antenna oscillator is less than the length of the elongated electrode portion.
3. The liquid crystal antenna unit according to claim 2 , wherein the first substrate and the second substrate comprise a same material, and the second substrate has a thickness that is 3 to 5 times as large as a thickness of the first substrate.
4. The liquid crystal antenna unit according to claim 2 , wherein the first substrate and the second substrate comprise different materials, respectively, and a thickness of the first substrate and a thickness of the second substrate satisfy the following relationship:
3
ɛ
1
ɛ
2
≤
H
2
H
1
≤
5
ɛ
1
ɛ
2
,
where H 1 is the thickness of the first substrate, H 2 is the thickness of the second substrate, ε 1 is a dielectric constant of the first substrate, and ε 2 is a dielectric constant of the second substrate.
5. The liquid crystal antenna unit according to claim 1 , wherein the first substrate and the second substrate comprise a same material, and the second substrate has a thickness that is 3 to 5 times as large as a thickness of the first substrate.
6. The liquid crystal antenna unit according to claim 1 , wherein the first substrate and the second substrate comprise different materials, respectively, and a thickness of the first substrate and a thickness of the second substrate satisfy the following relationship:
3
ɛ
1
ɛ
2
≤
H
2
H
1
≤
5
ɛ
1
ɛ
2
,
where H 1 is the thickness of the first substrate, H 2 is the thickness of the second substrate, ε 1 is a dielectric constant of the first substrate, and ε 2 is a dielectric constant of the second substrate.
7. The liquid crystal antenna unit according to claim 6 , wherein the second substrate is a composite board comprising N layers of materials, and the dielectric constant ε 2 of the second substrate is calculated according to the following formula:
ɛ
2
=
∑
i
N
(
Ti
H
2
*
ɛ
2
i
)
where
H
2
=
∑
i
N
Ti
,
Ti is a thickness of an i-th layer of material, ε 2i is a dielectric constant of the i-th layer of material, and N is an integer greater than or equal to 2.
8. The liquid crystal antenna unit according to claim 1 , wherein the second substrate is a composite board comprising N layers of materials, where N is an integer greater than or equal to 2.
9. The liquid crystal antenna unit according to claim 1 , wherein the second antenna oscillator, the first antenna oscillator, and the elongated electrode portion are arranged such that a center of the second antenna oscillator, a center of the gap in the first antenna oscillator, and a center of the elongated electrode portion are all on a straight line perpendicular to the first substrate or the second substrate.
10. The liquid crystal antenna unit according to claim 1 , wherein the first direction is perpendicular to the second direction.
11. The liquid crystal antenna unit according claim 1 , wherein the transmission line comprises a coplanar waveguide transmission line comprising a signal line and two ground wires respectively on both sides of the signal line.
12. The liquid crystal antenna unit according to claim 11 , wherein one end of the signal line is electrically connected to one end, which is proximal to the gap, of one pole of the two poles of the dipole, and one end of one ground wire, which is closer to the other pole of the two poles of the dipole, of the two ground wires, is electrically connected to one end of the other pole proximal to the gap.
13. The liquid crystal antenna unit according to claim 11 , wherein the first surface is the surface of the first substrate proximal to the second substrate, the liquid crystal antenna unit further comprises an electrode structure on a second surface, and the second surface is the surface of the second substrate proximal to the first substrate.
14. The liquid crystal antenna unit according to claim 13 , wherein the electrode structure comprises a plurality of electrodes parallel to each other and extending along the second surface in a direction perpendicular to the first direction.
15. The liquid crystal antenna unit according to claim 11 , wherein the first surface is the surface of the second substrate proximal to the first substrate, the liquid crystal antenna unit further comprises an electrode structure on a second surface, and the second surface is the surface of the first substrate proximal to the second substrate.
16. The liquid crystal antenna unit according to claim 1 , wherein the ground electrode further comprises an additional electrode portion extending from the elongated electrode portion in a direction perpendicular to the second direction along the surface of the first substrate distal to the second substrate.
17. The liquid crystal antenna unit according to claim 1 , wherein an orthographic projection of the first antenna oscillator on the first substrate, an orthographic projection of the second antenna oscillator on the first substrate, and an orthographic projection of the elongated electrode portion on the first substrate overlap each other.
18. The liquid crystal antenna unit according to claim 1 , wherein a thickness of the liquid crystal layer is less than 100 μm.
19. A liquid crystal phased array antenna, comprising a plurality of liquid crystal antenna units in an array, wherein each of the plurality of liquid crystal antenna units is the liquid crystal antenna unit according to claim 1 .
20. The liquid crystal phased array antenna according to claim 19 , wherein the first substrates of the plurality of liquid crystal antenna units as a whole are a single substrate, and the second substrates of the plurality of liquid crystal antenna units as a whole are another single substrate.