Description:Field of Invention
The current invention relates to Designing a reconfigurable sensing antenna for ultrawideband applications entails creating an antenna system that can operate over a wide frequency range while adapting to changing environmental conditions and communication needs. The invention focuses on identifying application-specific needs and constraints, such as frequency range, radiation pattern requirements, and environmental factors. The antenna should be able to efficiently cover the entire UWB spectrum, and its properties must be dynamically adjusted. This could include tunable components such as varactors, PIN diodes, or MEMS switches that can change the antenna's frequency, polarisation, or radiation pattern.

The objectives of this invention
The invention aims to design a compact reconfigurable sensingantenna for ultrawide band applications in which a multi-band reconfigurable multiple-input multiple-output (MIMO) sensing antenna is designedand antenna elements are combined with ultra-wideband (UWB)to suit the requirements of CR applications. frequency reconfigurability can be obtained by integrating PIN and varactor diodes. To examine the antenna parameters and performance at various frequency spectrums the testing of antenna is considered for two modes of operations with PIN diodes ON and OFF states, along with the tuning of varactor diode for a frequency range of 1 GHz.

Background of the invention
The concept of cognitive radio (CR) has been introduced by Joseph Mitola to overcome the bandwidth and spectrum challenges in most of the wireless communication networks [J. Mitola, ProceedingsoftheIEEE 97, Vol.97, 626-641,DOI: 10.1109/JPROC.2009.2013012,2009]. Introduction of CR systems along with wireless communications proved to obtain a great success for the network engineers to overcome most of the challenges that are linked with bandwidth allocation, efficiency, data management and data transmission speeds. The nature of complexity is very high in wireless networks due to the involvement of group of wireless nodes which establish the communication without having any formal infrastructure [A.M.Joykutty, and B. Baranidharan, 2020 International Conference on Smart Electronics and Communication (ICOSEC), pp. 878-884. DOI:10.1109/ICOSEC49089.2020.9215360]. They do not have any kind of fixed working topology to deal with and the topologies tend to vary instantaneously. Therefore, it is very difficult to make them operate them under a specific frequency spectrum or with a defined allocated bandwidth, and they can create a problem of radio spectrum scarcity [Shruti, and R. Rakhee,IEEE Annals of the History of Computing, Vol. 21, no. 7, pp. 2318-2331, 2022, DOI: 10.1109/TMC.2020.3042836.2020]. To meet such circumstances, the CR systems understand the availability of spectrum which is not under use and unoccupied. These systems are capable of switching and allocating the bandwidth requirements based on the demand by the end users. CR is comprised with two antennas (i.e., ultra-wideband sensing antenna and reconfigurable antenna) at the front end [Naveen Jacob, et.al., Procedia Computer Science, Vol.171, PP. 1279-1285, DOI: https://doi.org/10.1016/j.procs.2020.04.136.]. The role of ultra-wideband (UWB) antenna is to sense the spectrum of interest. However, the reconfigurable antenna helps to change the radiating characteristics of the antenna to operate with the available bandwidth (BW) [Sasmita Dash and Amalendu Patnaik, Photonics and Nanostructures - Fundamentals and Applications, Vol. 40, pp. 100-800, 2020, https://doi.org/10.1016/j.photonics.2020.100800.]The role of reconfigurable antennas in the wireless communication systems plays a vital role to adopt the existing circumstances and to act dynamically for the on-demand requirements of the end users to allocate the unused BW.Recently, extensive investigation of reconfigurable antennas is taking place for CR applications with the introduction of 4G and 5G technologies in wireless communications. The antenna design proposed by [R. Hussain, and M. S. Sahrawi, IET Microwaves, Antennas & Propagation vol. 9, pp.940-947, 2015 DOI: DOI: https://doi.org/10.1049/iet-map.2014.0605] is suitable to handle the wireless devices and mobile terminals that are operated for 4G applications. A low-cost embedded wireless cognitive network was implemented with unlicensed 2.4 GHz along with a real-time multi-sector spectrum sensing [D. Mazzer, et.al., Microwave and Optical Technology Letters 58, vol.no. 8 PP.1929-1934 2016 DOI: https://doi.org/10.1002/mop.29938]. This network functionality provided the reconfigurable radiation pattern by using an antenna array. A reconfigurable transceiver and antenna developed by Joseph et al. is allocating the transmission of two different frequencies (2.4 and 3.1 GHz) [S. D. Joseph, et.al., Wireless Personal Communications, Vol no. 3 PP: 3435-3462,2017]. Similar attempt was made by Ullah et al. by proposing two triple-band monopole antennas with different geometrical structures[Sadiq Ullah, et.al., AEU- International Journal of ElectronicsandCommunications,Vol.81,pp.236-242,2017,].These antennas claimed to function with a frequency band of 2.45, 3.5, and 5.2 GHz at different switching conditions. Another novel feature of reconfigurable antenna functioning at 2.45 GHz was introduced. to work underground mines. This experiment was carried out by authors at University of Queensland mine with a frequency of 1 GHz frequency band [H. Kunsei, et.al., IEEE Transactions on Antennas and Propagation, vol. 66, no. 12, pp. 7505-7510, Dec. 2018, doi: 10.1109/TAP.2018.2869250]. An improvement of 34% was claimed by the authors in coherence BW for line-of-sight (LOS) and non-line-of-sight (NLOS) propagation. The role of reconfigurableantennas in adaptive systems, wireless applications (such as 4G and 5G), and different types of capabilities were discussed [Ojaroudi Parchin, et.al., Electronics 8, Vol no. 2, pp 128,2019, https://doi.org/10.3390/electronics8020128]. The authors explored some of the interesting research aspects of reconfigurable antennas in their article towards usage of active materials included with Varactor PIN diodes and microelectromechanical systems (MEMS). A prototype of reconfigurable antenna was used. [D. N. Viet, et.al., EURASIP Journal on Wireless Communications and Networking,vol.no. 1, pp.1-17, 2019] to evaluate the performance of the reconfigurable antennas that are functioning based on spatial modulation. Some of the mathematical tools and theories applied over the empirical data were used to validate the data against Monte Carlo simulation results. Boufrioua [A. Boufrioua, Wireless Personal Communications 110, Vol.no. 4, pp 1879-1885, 2020] suggested switchable slot for the reconfigurable antennas that are etched over a rectangular patch, so that the incorporation PIN diodes in these slots can be used as a switch to ON and OFF. A better performance with respect to radiation pattern and return losses were observed with this experiment at different frequencies. Very recently, liquid-based reconfigurable antenna was proposed [Abu Bakar H, et.al.,Sensors, Vol No. (3), pp.827, 2021, DOI: https://doi.org/10.3390/s21030827] to meet the advanced requirements of wireless communications. Electrical properties of different liquids were examined at room temperatures to achieve the reconfiguration with respect to polarization, frequency, and radiation pattern. A novel approach of reconfigurable antennas by embedding conducting e-threads was proposed by hard-magnetic soft substrates were presented by Alharbi et al. [S. Alharbi, et.al., IEEE Transactions on Antennas and Propagation, vol. 68, no. 8, pp. 5882-5892, Aug. 2020, doi: 10.1109/TAP.2020.2988937]. This approach depends on the soft-magnetic materials which seriously suffer from stress failures, have got limited degree of freedom, and programmable polarity deformations are not possible. A reconfigurable microstrip patched antenna proposed by Guo et al. enables variode frequencies to cover the operations in S and C bands [Guo, et al. , Progress in Electromagnetics ResearchM 88 (2020): 159-167.]. The proposed antennas operate between frequency range of 3.29 to 4.01 GHz and 5.35 to 7.00 GHz to cover both the bands by maintaining the gain of 4.5 dBi.

Desription of Prior Art
Multiple-input multiple-output (MIMO) antennas are well known for their ability to improve data rates and reliability in in-building communication systems when compared to single antenna configurations. However, creating compact MIMO antennas with low profiles presents significant challenges. One such challenge is ensuring adequate isolation between co-located transmit and receive antennas in the MIMO system. Furthermore, achieving ultra-wideband (UWB) performance across the entire desired frequency range, such as the commercial communication and data bands between 700 and 2700 MHz, presents a significant challenge. Furthermore, the intricate task of designing MIMO antennas that not only incorporate the benefits of UWB but also maintain minimal coupling between co-located antennas, resulting in high isolation, adds to the complexity (US9716312). Research reveals novel approaches to antenna system configurations that take advantage of over-coupling between multiple antenna elements to achieve effective wide-band operation. This strategy uses a configuration with multiple antenna elements, where changes made to one antenna element, known as the influencing antenna element, cause significant changes in the operational frequency band of another antenna element, known as the respondent antenna element. Over-coupling causes a phenomenon in which the resonate frequency of the antenna element is split into multiple frequency bands at the second antenna. This frequency splitting, when applied to initially narrow-band antenna elements, allows the over-coupled antenna system to operate effectively across a wide band (US 20140240189). The scientific literature describes a novel cognitive HF radio system that includes a cognitive engine designed to improve HF transmission parameters through experiential learning from previous transmissions across a variety of transmission and environmental scenarios. Furthermore, it introduces electrically small HF antennas, which can include non-foster matching elements. Furthermore, the literature discusses another electrically small HF antenna and its associated impedance matching networks. Notably, it describes an impedance matching network that uses non-foster matching elements to improve antenna performance (US10903918B2).
Summary of Invention
The design, development, and testing of a multi-band frequency reconfigurable MIMO antenna with ultra-wideband sensing capabilities has been completed. The antenna consists of a U-shaped UWB sensor antenna with MIMO Meandered line components for spectrum sensing, and two planar inverted F-shaped antennas with Meandered line structures for frequency reconfigurability in communication. PIN diodes provide for frequency reconfigurability and multimode communication by acting as on/off switches. Varactor diodes allow for tuning across a wide bandwidth. With frequency reconfiguration across three bands using PIN diode switching (0.7GHz-0.85GHz, 1.25GHz-1.45GHz, and 1.6GHz-3GHz), the suggested sensing antenna covers a frequency range of 0.3GHz to 3GHz.The antenna system was constructed on a single 120 x 65 x 1.4 mm FR4 substrate. The suggested technique for frequency reconfigurable ultra-wideband MIMO increases efficiency while achieving a significant gain of 4dB at a single frequency and more than 2dB for multi-band frequencies. The suggested antenna design is small and allows for multi-band operation within the UWB range. In addition to a UWB antenna set up in a MIMO configuration, the same antenna is utilized for both sensing and communication. The omnidirectional radiation pattern, high efficiency, and consistent gain of the MIMO AND UWB sensing antenna span the intended bands.

Detailed description of the invention
The novel approach of reconfigurable multiple-input and multiple-output (MIMO) antenna is designed, tested and fabricated for UWB sensing. The monopole reconfigurable antenna is designed, which covers a frequency range of ~690 to 2910 MHz. A detailed test was carried out upon the antenna design for the scattered parameters (i.e., S-Parameters), to plot gain patterns and to measure the efficiency. This antenna design was tested for ON-state and OFF-state of the varactor diodes to plotted the gain patterns.
The design is consisting of two layers. Top layer consists of two meander line MIMO reconfigurable antenna with 8×57 mm2 and the bottom layer is designed with a UWB sensing antenna. The ground plane of the antenna is situated on the top layer of the board, which is considered as a GND reference plane for the reconfigurable antenna. The top view and bottom view of the proposed reconfigurable MIMO antenna with the biasing circuit is shown in Fig. 1 with all dimensions measured in mm. The corresponding schematic with detailed arrangement of diodes (PIN and Varactor)
In this antenna, the frequency reconfigurability is obtained by using the diodes (D1 to D4) . The role of PIN diodes (D1 and D3) is to connect the radiating parts and to switch the antenna arrangement to function in operating bands. Similarly, the fine tuning of the antenna operations is obtained with the help of varactor diodes (D2 and D4) for low frequency bands and the shorting wall of the antenna is connected to meander line and GND plane.
The role of biasing circuit is very crucial to maintain a balance between different frequencies that varies from very low to UWB frequencies. The role of biasing circuit is not just limited to offer a balance for the circuit but allows the same to operate in multi-frequency bands. The circuit components are a combination of series arrangement of RF choke (1 ??H) and a resistor (2.1 K?) connected with PIN or Varactor diode connecting the radiating part of the proposed antenna structure.
Thereconfigurable antenna model for UWB sensing was simulated using HFSSTM tool. The antenna was simulated and tested for ON and OFF states to obtain the gain plot, radiation pattern, and to observe the S-Parameters at different frequencies. The radiation pattern for the proposed antenna under the OFF state and ON state are simulated

The Mode-I of operation represents the PIN diode in OFF state at the time of simulation for the proposed reconfigurable MIMO antenna. In this mode, the varactor diodes capacitance is varied to test the effect on operating frequency, which is found to negligible. The gain was calculated at 1.75 GHz with two different cut angles (i.e., Phi at 00 and 900) and two resistance values (i.e., at 50 k? and 0.0001k?).
The simulated results for reflection coefficient for the OFF state are noted. The corresponding S-parameters are calculated for the resistance values of 0.0001k? and 50k?. From the observations it can be seen that the antenna is resonating (i.e., first resonance) at 0.75 GHz with an impedance bandwidth of 0.12 GHz. The second resonance occur at 1.16 GHz and with the impedance bandwidth of 1.53 GHz. Whereas in case of third resonance at 1.53 GHz, it is giving rise to the impedance bandwidth of 0.5 GHz. The fourth resonance was noticed at 2.9 GHz with an impedance bandwidth of 0.81 GHz. Finally, the antenna is also resonating at 2.9 GHz with an impedance bandwidth of 0.23 GHz.

The Mode-II of operation represents the PIN diode in ON state at the time of simulation for the proposed reconfigurable MIMO antenna. In this mode, the varactor diodes are applied with a biased voltage ranging between 0-6V. A slight change in capacitance of the varactors is observed and the impact of that was seen over the operating frequencies with a smooth transition. In this mode, the gain was calculated at 1.75 GHz for three different cut angles (i.e., Phi at 00, 900) with a resistance value of 50 k?. From the observed results it is seen that the antenna is giving Omni directional pattern in H-plane and in E-plane for both OFF state and ON state.
The simulated results for reflection coefficient for the ON state are noted7. The corresponding S-parameters are calculated for the resistance values of 0.0001k? and 50k?.From the observations it can be seen that the antenna is resonating (i.e., first resonance) at 0.73 GHz with an impedance bandwidth of 0.06 GHz. The second resonance occur at 1.39 GHz and with the impedance bandwidth of 0.2 GHz. The third resonance occurs at 1.82 GHz with the impedance bandwidth of 0.33 GHz. Finally, the antenna is also resonating at 2.94 GHz with an impedance bandwidth of 0.3 GHz. To understand gain parameters for the proposed reconfigurable MIMO antenna, 3D gain patterns were obtained from HFSS tool. The gain patterns are acquired in ON and OFF circumstances, respectively, for both modes of operation. When the antenna is turned on, it provides a gain of 4 dBi; when it is turned off, it provides a gain of 2.4 dBi. Depending on the application, the structure can have appropriate radiating patches added to it in the desired direction to increase the gain values. The antenna is determined to be linearly polarized and to represent the moderate directivity based on the radiation patterns.

Brief description of Drawing
In the figures which are illustrated exemplary embodiments of the invention.
Figure 1. Geometry of Reconfigurable MIMO Antenna for CR platform and arrangement of PIN and Varactor diodes for the Biasing Circuit.
Figure 2. Radiation pattern, Reflection coefficient and Gain plot for proposed antenna under OFF State.
Figure 3. Radiation pattern, Reflection coefficient and Gain plot for proposed antenna under OFF State.

Detailed description of the drawing

Figure 1 figure 1(a)shows the designed anantenna geometry which was simulated using HFSS 18.2. and figure 1(b) shows thefabricatedantenna on a FR4 substrate. The PIFA MIMO was designed on top layer of the substrate which is operated as frequency reconfigurable antenna. UWB antenna is introduced on to the bottom layer of the structure which helps to operate at UWB band. The combination of MIMO and UWB can be used in cognitive radio applications. Ground plane was placed on the top layer of the substrate.Figure 1(c)depicts the Arrangement of PIN and Varactor diodes for the Biasing Circuit this biasing circuit is connected to the MIMO antenna varactor diode is used scan the frequency spectrum where PIN diode is used to achieve the frequency reconfigurability. The power supply to the pin diodes is given with the equivalent circuit. SMA connector is used to give the feeding to the antenna.
Figure 2 Figure 2(a) illustratesthe Radiation pattern of the antenna under OFF State of MIMO antenna this shows that the antenna can radiates in all directions. Figure 2(b) represents the S11 parameter of MIMO antenna in OFF state it can be seen that the antenna is resonating (i.e., first resonance) at 0.75 GHz with an impedance bandwidth of 0.12 GHz. The second resonance occur at 1.16 GHz and with the impedance bandwidth of 1.53 GHz. Whereas in case of third resonance at 1.53 GHz, it is giving rise to the impedance bandwidth of 0.5 GHz.

Figure 3 figure 3(a) illustrates the Radiation pattern of the antenna under ON State of MIMO antenna it is seen that the antenna is giving Omni directional pattern in H-plane. Figure 3(b) represents the S11 parameter of MIMO antenna in ON state the antenna is resonating (i.e., first resonance) at 0.73 GHz with an impedance bandwidth of 0.06 GHz. The second resonance occur at 1.39 GHz and with the impedance bandwidth of 0.2 GHz. The third resonance occurs at 1.82 GHz with the impedance bandwidth of 0.33 GHz. Finally, the antenna is also resonating at 2.94 GHz with an impedance bandwidth of 0.3 GHz. Figure3(c) Shows the Gain Plot for ON State for the proposed MIMO Antenna which is providing 2.4 dB gain. , Claims:The scope of the invention is defined by the following claims:

Claims:

1. The antenna is simulated using Ansoft High Frequency Structural Simulator HFSS.18.2 comprising following steps:
a) A PIFA on top layer of the substrate which was integrated with PIN diode to achieve a frequency reconfigurability.
b) A Square shape ground plane is used to improve the antenna's bandwidth and reduce its surface area.
c) A varactor diode switches the antenna for different frequency ranges, ensuring the entire frequency spectrum.

2. As per claim 1, the antenna was developed using printed circuit board technology and tested with a network analyzer for S11 parameters and an anechoic chamber for radiation patterns at multiple frequencies.
3. As per claim 1, the antenna's reconfigurability is achieved using PIN diodes, which switches between multiple frequency bands. This increases the antenna's versatility for wireless communication especially for cognitive radio.