Polarization Reconfigurable Circular Patch MIMO Antenna with Improved Isolation

This paper presents, compact multiband frequency reconfigurable 3x1 MIMO antenna for cognitive radio applications. The antenna comprises 3-elements reconfigurable MIMO antenna and single element UWB sensing antenna. The frequency reconfigurability range under (S11 ≤ -10 dB) from 7-14.8 GHz using single PIN diode, while the UWB frequency range from 2.597-23.08 GHz. The antenna is designed and optimized to cover such wireless applications such as WiMAX, international telecommunication union (ITU), satellite, and broadband applications. The antenna is optimized using a Genetic Algorithm to operate in the MIMO and cognitive radio systems. The antenna dimensions for 3-elements MIMO antenna are 55 x 65 x 1.6 mm3 printed on an FR-4 epoxy substrate with relative dielectric constant εr = 4.3, loss tangent tan (δ) = 0.002 and 50 Ω microstrip feed line. The obtained simulated gain is ranging from 2.8-8.25 dB and the maximum simulated gain is 8.25 dB at 8.5 GHz. The return loss, Envelope Correlation Coefficient ECC, and Isolation are obtained to be less than -25 dB, less than 0.018, and less than -17 dB respectively. Detailed simulation results are explored and studied in this research. The CST software is used to simulate and optimize the proposed antenna.

The paper addresses the investigations of four elements MIMO antenna with reconfigurable grounds for 5 G NR n3/n1/n40/n41/n77/n79 to X-bands using PIN diodes. Initially, a single unit ultra wideband antenna is implemented, and then it is extended to 2 × 2 MIMO with reconfigurable grounds using one PIN diode. Later, the 4 × 4 MIMO antenna with reconfigurable grounds using six PIN diodes is developed. This study has the novelty that it gives the analysis and design of MIMO antennas switching between unconnected and connected grounds by the method of reconfiguration. The proposed 4 × 4 MIMO is fabricated on FR4 substrate with a volume of 0.485λ0 × 0.326λ0 × 0.0075λ0 mm3, where λ0 is calculated at a lowest resonating frequency. It has operating frequency bands of 1.4–1.6 GHz, 1.75–2.5 GHz and 2.7–13 GHz with connected grounds. The port isolation in the majority of the band is ≤ −15 dB. The inference is included on all the performance metrics. The fabricated MIMO performance is in line with simulated results and hence validates the observations of this research work. So, the proposed MIMO designs are compatible with 5 G wireless applications.

With the rapid development of science and technology, it is an inevitable trend for wireless communication systems to work on the same platform in different frequency bands. Reconfigurable antenna realizes the reconfiguration of parameters such as resonant frequency, polarization mode and radiation direction. The function of traditional multi-antennas can be realized by a single antenna. This paper presents a frequency reconfigurable antenna, which is especially suitable for multi-band and single-band hopping network communication systems. The simulation results show that the bias network has little effect on the antenna performance. In this paper, a polarization reconfigurable clover antenna fed by coplanar waveguide is proposed, which can realize switching function between left-handed circular polarization and right-handed circular polarization.

A novel dual-sense polarization reconfigurable dual-band microstrip antenna

In this article, a circular microstrip tunable wideband frequency and polarisation reconfigurable antenna are investigated. The wideband tunability is achieved by placing the four varactor diodes between circular microstrip patch and circular ring. The impedance bandwidth of 2.09–2.96 GHz (34.52%) is realised by tuning the capacitance value from 4.15 pF (0 V) to 0.94 pF (6 V). Both frequency tunability and polarisation reconfigurability are controlled in the antenna using the proposed cascaded branch line coupler feed network. The four single pole double throw and two dual in‐line package switches are used in the feed network to control the tunable impedance bandwidth of the antenna over a wideband from 1.25 to 2.95 GHz. The vertical linear polarisation and horizontal linear polarisation (H‐LP) are achieved by any one of the feed port excited in the antenna. Similarly, the right‐hand circular polarisation and left‐hand circular polarisation are realised by exciting both the feed ports in the antenna with±90° phase difference. The impedance bandwidth of proposed feed network is well matching with the tunable bandwidth of the patch antenna. Simulated and experimental verification results show good agreement.

This communication presents a model and optimization of a dual-sense circularly polarized (RHCP/LHCP) 2-port MIMO antenna with increased isolation. The antenna operates in a broad frequency range of 1.76–4.0 GHz and is loaded with a metasurface. It has dimensions of 98.5 × 39 mm2 and an edge-to-edge distance of 55.5 mm. The MIMO antenna is created by replicating a single unit and placing it in a mirrored configuration around the y-axis. The dimensions of the unit antenna are 40 × 39 × 0.8 mm3 and it is printed on a substrate made of FR4 with a thickness of 0.8 mm. The substrate has a relative permittivity (ε r) of 4.4 and a loss tangent (tanδ) of 0.02. The isolation between the ports may be enhanced by including a metasurface absorber, increasing from 12 dB to 23 dB. To verify the wideband and CP properties, we examine the MIMO antenna unit element for its reflection coefficient, peak gain (4.2 dB), radiation efficiency (about 90%), axial ratio, and surface current distribution. Machine learning is used to improve the design of metasurface unit cells to achieve optimum absorption. The Envelope correlation coefficient (ECC), Diversity gain (DG), and Channel capacity loss (CCL) of the proposed metasurface absorber-enabled antenna are simulated and calculated to prove its MIMO identity. The HFSS simulations are consistent with the experimental results obtained from the developed model.

This paper presents the use of electromagnetic bandgap (EBG) structure in the pattern and polarization reconfigurable antenna for beam-steering configurations. The proposed antenna consists a group of EBG structure to control the pattern reconfigurability. While two triangular slits are introduces on the square patches to give polarization reconfigurability. The PIN diode is used as the switching method. A maximum +15° and -15° of beam steering is achieved at both linear and circular polarization.

This paper presents the design and implementation of a novel four‐port multiple input multiple output (MIMO) antenna with reconfigurable filtering characteristics. The proposed filtering MIMO antenna is constructed using a super wideband (SWB) monopole. The feedline of the monopole radiator is integrated with a microstrip filter network. Reconfigurable filtering characteristics are realized using a feed selection network making the antenna work at two modes viz. SWB mode (2.2 to over 20 GHz) and dual narrow‐band (d‐NB) mode (2.45 and 5.8 GHz). The feed selection is accomplished using a PIN diode. An interlocked four‐port MIMO antenna is then constructed using the proposed reconfigurable filtering monopole antenna. The proposed antenna exhibits an average gain greater than 5.2 dBi in both operating modes and has total efficiency greater than 80%. The MIMO parameters such as envelope correlation coefficient (ECC), diversity gain (DG), and mean effective gain (MEG) are evaluated and presented. The prototype MIMO antenna is fabricated and the experimental results are validated in real‐time. The proposed reconfigurable MIMO antenna is suitable for wireless local area network (WLAN), Internet of things (IoT), dedicated short‐range communication (DSRC), ultra‐wideband (UWB), and SWB applications in the automotive scenario.

A novel approach for low mutual coupling and ultra-compact Two Port MIMO antenna development for UWB wireless application

This study presents a high-efficiency circular microstrip patch antenna designed for radio frequency identification (RFID) applications simulation results illustrate the performance of a circular microstrip patch antenna operating at 900 MHz. Microstrip antennas are renowned for their ability to meet the requirements of compact, lightweight designs, ensuring compatibility, and ease of integration. This research focuses on the development of a circular microstrip antenna, formed as a circular patch on a 0.035 mm thick FR-4 substrate. The design was realized using a substrate with a relative permittivity (εr) of 4.3, a loss tangent (tan δ) of 0.021 and a substrate height (h) of 1.6 mm. The antenna dimensions are small, measuring 58×45 mm, with a circular patch radius of 17 mm. The antenna operates over a frequency range from 0.5 GHz to 2 GHz. Key performance parameters include a return loss of -49.8 dB, a wide bandwidth of 150 MHz, a voltage standing wave ratio (VSWR) of 1.009, a gain of 2.161 dB, and a directivity of 2.200 dBi. Antenna design and simulation were carried out using computer simulation technology (CST) Studio Suite Software, specifically adapted to RFID applications.

A novel single feed frequency and polarization reconfigurable microstrip patch antenna

This paper presents the design and analysis of a reconfigurable microstrip slot antenna using RF PIN diodes as switching device for S and C band. Here pattern and frequency reconfigurable microstrip antenna is designed by changing the slot length on ground plane through six MPP4203 PIN Diodes. These six PIN diodes are used to electrically connect and disconnect the slot to alter the total slot length 76 mm in x axis and 56 mm in y axis. Here three switches are positioned in slot which is cut along the x-axis and another three switches are positioned in the slot along the y-axis. The analysis of reconfigurable antenna using PIN diode is done using the simulation performed on Ansys HFSS. The pattern and frequency reconfigurability of proposed antenna is analyzed for S (2–4 GHz) and C band (4–6 GHz) in terms of return loss and radiation pattern. The microstrip antenna design shows the pattern and frequency reconfigurability at 11 resonating frequencies. The proposed reconfigurable antenna is capable to resonate at three resonating frequencies (2.2, 2.3, and 2.4 GHz) in S band and 8 resonating frequencies (5.7, 5.8, 5.9, 6, 6.1, 6.3, 6.4, and 6.5 GHz) in C band. The simulated radiation patterns at various resonating frequencies shows pattern reconfigurability with acceptable gain in xz and yz plane of microstrip patch antenna. Furthermore the re-configurable antenna reduced the front end system's size and offers pre-filtering at the receiver. The proposed microstrip patch slot antenna is quite suited to be integrated with WLAN and Bluetooth devices with less structure complexity.

A single fed circularly polarized reconfigurable patch antenna is proposed. The antenna consists of a radiating patch incorporated with an H-shaped slot at its center. Four ultra-miniature switches are used for polarization reconfiguration. The antenna is designed to operate at the center frequency of 2.357 GHz. The antenna achieves either left-hand polarization or right-hand polarization depending upon switching of corresponding switches. The antenna parameters are simulated using Ansoft high-frequency structure simulator and are validated using an Agilent network analyzer (N9925A) and antenna test systems. The antenna achieves a good impedance match of 120MHz between 2.26GHz – 2.38GHz band and achieves low cross-polarization isolation of -22.82 dB for RHCP and -21.77 dB for LHCP configurations at its operating frequency. The antenna finds application in areas of modern wireless communication.

SummaryA two‐port multiple‐input‐multiple‐output (MIMO) antenna system operating in the mm‐wave band for 5G applications is presented. The two elements of MIMO structure are separated from each other by 19 mm (1.9 ) and excited by microstrip feed. The MIMO elements are circular patches with round cuts at the edges to improve impedance bandwidth. Quadrilateral slot in the ground plane is designed to improve the radiation characteristics of the radiating element having size 18 0.8 mm3. The MIMO design is simulated through CST. The proposed antenna works in 27–29 GHz range, providing a potential bandwidth of 2 GHz. Furthermore a gain is improved from 8.2 to 8.75 dB and efficiency increase from 85% to 88% and high isolation of 64 dB is achieved by placing 4‐elements of metamaterial with size 4.5 18 mm2 in the middle of two circular monopole antennas. The metamaterial gives us a band stop response and act as decoupler and enhance the isolation to reduce mutual coupling. By analyzing the radiation characteristics of the proposed design, in term of reflection coefficient, surface currents, reduced mutual coupling, suitable gain, envelope correlation coefficient (ECC), diversity gain (DG) and radiation pattern, the recommended antenna can be considered a good candidate for 5G applications.

In this work, an ultra-wideband graphene-based micro-sized circular patch-shaped Yagi-like MIMO antenna was investigated over 1–30 THz of the frequency spectrum. The proposed antenna structure was designed over a polyimide substrate with 620 × 800 µm2. This antenna was radiated over three bands over 1–30 THz. The maximum bandwidth achieved 10.96 THz, with −26 dB of the return loss isolation. These three bands were also mathematically analyzed using various MIMO antenna parameters to match the MIMO antenna criteria. This antenna provided all the accepted results as per the limits set by these antenna parameters. The effect of the different port excitation on the change of directivity of the overall structure is also reported. The MIMO antenna parameters such as TARC (Total Active Reflection Coefficient), ECC (Envelope Correlation Coefficient), MEG (Mean Effective Gain), CCL (Channel Capacity Loss), and DG (Directivity Gain) were investigated for the proposed structure. These values were also identified to check the compatibility and challenges associated with short-distance communication. The suggested THz MIMO antenna provides the operating bands of 1–10 THz and 15–30 THz, with good isolation values. An average of 7 dB gain was observed in the 2 × 2 antenna structure. The newly developed MIMO antenna in the THz frequency range may be used for high-speed short-distance and terahertz communications.