Claims:We claim
1. An optically transparent UWB MIMO antenna (100) comprising of
a glass substrate (101),
a pair of monopole radiators (102) with partial ground plane (103) placed on either side of the glass substrate (101)
characterized in that,
a half square cut monopole (201 & 202) loaded with semi-circular slot (211), wherein it is coated with ITO
a stair case shaped stubs (305) attached to the partial ground plane (103), wherein it is coated with dual layer (FTO/ITO)

2. The optically transparent UWB MIMO antenna (100) as claimed in 1, wherein the half square cut monopole (201 & 202) has semi-circular slot (211) deployed at the center with diameter (207) to achieve wider impedance bandwidth.

3. The optically transparent UWB MIMO antenna (100) as claimed in 1, wherein the half square cut monopole (201& 202) loaded with semi-circular slot (211) has an offset feed line with width (208) and length (209) to achieve maximum radiation efficiency.

4. The optically transparent UWB MIMO antenna (100) as claimed in 1, wherein the partial ground plane (103) has a square notch (309) with length (304) and width (303) to improve the reflection coefficient characteristics.

5. The optically transparent UWB MIMO antenna (100) as claimed in 1, wherein the half square cut monopole (201 & 202) loaded with semi-circular slot (211) is replicated along the x-axis at a distance of (210) to achieve spatial diversity.

6. The optically transparent UWB MIMO antenna (100) as claimed in 1, wherein the partial ground plane (103) has staircase shaped stubs (305) with step size (306) and length (307 & 308) to improve the isolation between the half square cut monopole (201 & 202) loaded with semi-circular slot (211).

7. The optically transparent UWB MIMO antenna (100) as claimed in 1, wherein the partial ground plane (103) increases the capacitance effect between the partial ground plane (103) and half square cut monopole (201& 202) loaded with semi-circular slot (211) realizing a wider bandwidth.

8. The optically transparent UWB MIMO antenna (100) as claimed in 1, wherein the UWB MIMO antenna (100) operates over a frequency range of 2.4-11 GHz with isolation greater than 20 dB and the optical transmittance of the UWB MIMO antenna (100) is greater than 72%.

Dated this 15th day of March 2021.
, Description:Field and use of Invention: -
[001] The field of the present invention is Antenna Engineering, particularly relates to the design of Multi-Input Multi-Output (MIMO) antenna. The present invention can be applied in automotive communications to improve the aesthetics and further to enhance the quality and reliability of the wireless link.

Background of the Invention: -
[002] Owing to the development in modern communication technologies, modern automobiles are fitted with systems for AM radio, FM radio, TV, cellular and keyless entry. To satisfy these wireless requirements, antennas are placed on the exterior parts of the automobiles. Space is often limited for placing the antennas in automobiles. The antennas embedded inside the vehicle does not see an ideal radiation environment due to the scattering and shadowing caused by the automobiles. The significant portion of the automobiles is covered with glass. Hence, if antennas are optically transparent then the antenna deployment space can be easily expanded to the windshields, mirrors and sunroof. The transparent antenna can be placed on the windshields, only if the optical transmittance of the antenna is greater than 72%. The conductive films used for the design of transparent antennas are transparent metal oxide films such as ITO (Indium doped Tin Oxide), FTO (Fluorine doped Tin Oxide), AZO (Aluminium doped Zinc Oxide); multilayer films, an ultra-thin metal film such as copper, silver, gold; wired metal mesh films and Micro metal mesh. Furthermore, the metal oxide films provide high transmittance compared to other materials. This invention designed an optically transparent antenna using metal oxide films since the optically transparent antennas placed on the vehicles require optical transmittance greater than 70%.
[003] UWB (Ultra-wide Band) communication has been an area of extensive research in recent years due to its potential applications and advantages over narrowband technology. The narrowband systems suffer from low data rate and are highly sensitive to transmitter and receiver locations. The UWB technology is likely to provide a high data rate and is adopted in many applications such as high-speed mobile communications, in-car sensor network communication, automotive localization, and tracking with high spatial resolution, emergency services, and roadside assistance. However, in urban environment the signals are distorted due to the multi-path fading. So, UWB systems are integrated with MIMO technology in the automobiles to alleviate multipath fading, achieve high data rate, and to ensure channel capacity and link quality. The coupling between the antennas in the multi-antenna system severely affects the system performance. To overcome this issue, the isolation should be increased between the antenna elements. UWB MIMO antenna is proposed in the invention with high isolation between the radiating elements without adding any decoupling structures.

Objective of the Invention:-
[004] The primary objective of the invention is to design a spatial diverse optically transparent UWB antenna.
[005] Another objective of the present invention is to provide high isolation between the antennas without adding any decoupling structures.
[006] It is another objective of the present invention is to integrate the optically transparent antenna into the automotive environment to overcome fading effects.

[007] It is yet another objective of the present invention is to provide low correlation between the antennas and obtain good diversity performance.

Brief description of the prior art:-
[008] There are patents on transparent antenna design and UWB MIMO antenna design, but the proposed invention is an optically transparent UWB MIMO antenna.
Draw backs of existing state-of-art
1. Most of the UWB transparent antennas proposed in the literature have poor realized gain.
2. The MIMO antennas isolation is obtained by using complicated decoupling structures.
3. The envelope correlation between the elements is reduced with complicated structures.
4. Optically transparent UWB MIMO antenna targeted for automotive environment are not proposed in the literature

This proposed invention has the following advantages:

1. The proposed UWB MIMO antenna has a simple geometry since there are no additional decoupling structures.
2. The proposed UWB MIMO antenna provides a wider bandwidth of 8.6 GHz.
3. The proposed MIMO antenna provides isolation greater than 20 dB over the entire operating region which is better than most of the MIMO antennas reported in the literature.
4. The proposed optically transparent antenna has an omni-directional radiation pattern with a peak realized gain of 2 dBi and radiation efficiency of 60%.
5. The Envelope Correlation Coefficient (ECC) of the proposed MIMO antenna is less than 0.04 for the frequency 2.4 to 6.3 GHz and it is less than 0.02 between 6.4 to 11 GHz showing that it has a better correlation between the antenna elements.
6. The optical transmittance of the proposed antenna is greater than 72% which is better than most of the optically transparent antennas in literature. It can be integrated on the glass surfaces of the vehicles without blocking the view of the driver.

Summary of the Invention:-
[009] A novel optically transparent UWB MIMO antenna is reported in the invention. It consists of two semi-circular slot loaded rectangular monopole on one side of the substrate and a staircase ground structure on the other side of the glass substrate. The antenna is designed on a soda-lime glass substrate with a thickness of 2.2 mm, a dielectric constant of 7, and a loss tangent of 0.04. The monopole radiators of the antenna are made of ITO film with sheet resistance 10 ?/sq and thickness 800 nm. The partial ground plane is made of dual-layer (FTO/ITO) film with sheet resistance 4 ?/sq and thickness 1.4 µm. The dual-layer coating is used in the ground plane to reduce the conductive losses in the ground by decreasing the sheet resistance. The proposed antenna occupies an area of 29 ? 50 mm2. The optical transmittance of the proposed UWB MIMO antenna is 72% and hence it can be installed on the glass surfaces of the automotive (windshield of the car). The antenna placed on the car does not block the normal vision of the driver/passenger. The MIMO antenna can also be mounted on the rear windshield of the car. The transparency property of the UWB MIMO antenna makes it unique and can be used to replace the traditional automotive antennas while retaining the functionalities. The proposed transparent antenna exhibits a good impedance matching over a frequency of 2.4-11 GHz with isolation greater than 20 dB, a peak gain of 2 dBi, and optical transmittance greater than 72% which is suitable for UWB automotive applications.

Brief Description of the figures:
[010] The accompanying drawings illustrate the embodiment of invention and complete understanding of the principles of invention.
Figure 1: An exemplary embodiment of the UWB MIMO antenna and its layered view.
Figure 2: An exemplary embodiment of the front view of the UWB MIMO antenna.
Figure 3: An exemplary embodiment of the rear view of the UWB MIMO antenna.
Figure 4: Reflection and Isolation characteristics of the UWB MIMO antenna.

Detailed description of the invention:-
[011] A novel transparent UWB MIMO antenna (100) for automotive applications is reported in the present invention. Figure 1 refers to the exemplary embodiment of the UWB MIMO antenna (100) and its layered view. Figure 2 refers to the exemplary embodiment of the front view (200) of the transparent UWB MIMO antenna (100). The length and width of the UWB MIMO antenna (100) is (203) and (204) respectively. The UWB MIMO antenna (100) comprises of two half square cut monopole (201 & 202) with semi-circular slot (211) with partial ground plane (103). The half square cut monopole (201 & 202) with semi-circular slot (211) is designed by removing half portion of the square forming a rectangle with length (206) and width (205). Later, a semi-circular slot with diameter (207) is etched from the center of the half square cut monopole (201 & 202). The two half square cut monopoles (201 & 202) with semi-circular slot (211) are identical. The half square cut monopole (201 & 202) with semi-circular slot (211) is replicated by placing at a distance of (209) to achieve spatial diversity. The half square cut monopole (201 & 202) with semi-circular slot (211) improves bandwidth and also transparency of the antenna. The two half square cut monopole (201 & 202) with semi-circular slot (211) are connected to a 50 ? coaxial connector through an offset feed line of width (208) and length (209).
[012] Figure 3 refers to the exemplary embodiment of the rear view (300) of the transparent UWB MIMO antenna (100). The length and width of the partial ground plane (103) is (301) and (302). The partial ground plane (103) is designed by adding stair case shaped stubs (305) and notch (309). The stair case shaped stubs (305) consist of two steps with step size (306) and length (307 & 308). A notch (309) of length (304) and width (303) is introduced into the partial ground plane (103). The partial ground plane (103) with stair case shaped stubs (305) and notch (309) increases the capacitance effect between the partial ground plane (103) and the two half square cut monopole (201 & 202) with semi-circular slot (211) realizing a wide bandwidth. The partial ground plane (103) with stair case shaped stubs (305) provides high isolation between the monopole radiators (102).
[013] Figure 4 depicts the reflection (S11 and S22) and isolation (S21 and S12) coefficients (400) of the UWB MIMO antenna (100). The UWB MIMO antenna (100) is operated over the entire UWB range that is from 2.4-11 GHz. The isolation between the antennas is greater than 20 dB over the entire UWB frequency range.