Physical Review B

A compact multiple-input-multiple-output (MIMO) antenna with a small size of 26×40 mm2 is proposed for portable ultrawideband (UWB) applications. The antenna consists of two planar-monopole (PM) antenna elements with microstrip-fed printed on one side of the substrate and placed perpendicularly to each other to achieve good isolation. To enhance isolation and increase impedance bandwidth, two long protruding ground stubs are added to the ground plane on the other side and a short ground strip is used to connect the ground planes of the two PMs together to form a common ground. Simulation and measurement are used to study the antenna performance in terms of reflection coefficients at the two input ports, coupling between the two input ports, radiation pattern, realized peak gain, efficiency and envelope correlation coefficient for pattern diversity. Results show that the MIMO antenna has an impedance bandwidth of larger than 3.1-10.6 GHz, low mutual coupling of less than -15 dB, and a low envelope correlation coefficient of less than 0.2 across the frequency band, making it a good candidate for portable UWB applications.

Compact MIMO Antenna for Portable Devices in UWB Applications

A compact dual band-notched ultra-wideband (UWB) multiple-input multiple-output (MIMO) antenna with high isolation is designed on a FR4 substrate (27 × 30 × 0.8 mm3). To improve the input impedance matching and increase the isolation for the frequencies ≥ 4.0 GHz, the two antenna elements with compact size of 5.5 × 11 mm2 are connected to the two protruded ground parts, respectively. A 1/3 λ rectangular metal strip producing a 1.0 λ loop path with the corresponding antenna element is used to obtain the notched frequency from 5.15 to 5.85 GHz. For the rejected band of 3.30-3.70 GHz, a 1/4 λ open slot is etched into the radiator. Moreover, the two protruded ground parts are connected by a compact metal strip to reduce the mutual coupling for the band of 3.0-4.0 GHz. The simulated and measured results show a bandwidth with |S11| ≤ -10 dB, |S21| ≤ -20 dB and frequency ranged from 3.0 to 11.0 GHz excluding the two rejected bands, is achieved, and all the measured and calculated results show the proposed UWB MIMO antenna is a good candidate for UWB MIMO systems.

Compact Dual Band-Notched UWB MIMO Antenna With High Isolation

Two compact coradiator multiple-input-multiple-out (MIMO) antennas operating in the UWB frequency band with dual polarization are proposed. Different from traditional MIMO antennas, the radiator is shared by two antenna elements, which greatly reduce the overall size of the MIMO system. High isolation between the two antenna elements is achieved by etching a T-shaped slot in the radiator and extending a stub on the ground. Dual polarization can be realized by exciting the pentagonal radiator with perpendicular feeding structure. The simulated results of current and electric-field distribution show the dual-polarization characteristics of the diversity system. Besides, a four units UWB MIMO antenna is also proposed. Furthermore, the diversity characteristics of mean effective gains (MEGs) and diversity gain (DG) are also studied. The simulated and measured results demonstrate that the UWB-MIMO antenna has good impedance matching, isolation and dual polarization characteristics.

Compact Coradiator UWB-MIMO Antenna With Dual Polarization

In this paper, a compact design of multiple-input multiple-output (MIMO) Antenna with dual sharply rejected notch bands for portable wireless ultrawideband (UWB) applications is presented and experimentally investigated. The proposed UWB MIMO Antenna has a compact size of 18 mm $\times$ 34 mm. The tapered microstrip fed slot Antenna acts as a single radiating element with inverted L-shaped slits to introduce notches at wireless local area network and the IEEE INSAT/Super-Extended C-bands. The mutual coupling of less than −22 dB is achieved over the entire operating band (2.93–20 GHz). At the center of notched band, the efficiency of the Antenna drops that indicates a good interference suppression performance. The performance of the MIMO Antenna in terms of isolation among the ports, radiation pattern, efficiency, realized gain, envelope correlation coefficient, mean effective gain, and total active reflection coefficient is studied.

Tapered Fed Compact UWB MIMO-Diversity Antenna With Dual Band-Notched Characteristics

Wireless power transfer using resonant inductive coupling has been employed in a number of applications, including wireless charging of electronic devices and powering of implanted biomedical devices. In these applications, power is transferred over short distances, which are much smaller (~ λ/100) than the wavelength of operation. In such systems, the power transfer efficiency of the link is inversely related to the range of operation. The power transfer efficiency is principally a function of the Q's of the individual coils and the coupling between them. In this paper, we demonstrate improvements in power transfer efficiencies using negative permeability metamaterials by increasing the mutual coupling between coils. A metamaterial slab is designed for operation at 27 MHz and is compact in size. The power transfer efficiency of the telemetry system in free space is compared to that in the presence of the metamaterial placed near one of the coils. The efficiency of the system increased in the presence of the metamaterial even as the free-space separation was held constant. This shows that compact negative permeability metamaterials can be used to increase power transfer efficiency of short-range telemetry systems used in various applications.

Improving Power Transfer Efficiency of a Short-Range Telemetry System Using Compact Metamaterials

Recently it was shown that co-located vector antennas can provide the same capacity increase as spatial array antennas in multiple-input multiple-output (MIMO) systems. This paper describes the design of a vector antenna consisting of a loop antenna and two orthogonal bowtie antennas for a ultrawideband (UWB) MIMO system that operates in the frequency range 3.6-8.5 GHz. Channel capacity calculations performed with the antenna operating in a rich scattering environment show that spectral efficiency of the UWB vector antenna system approaches that of the traditional spatial array. This demonstrates that vector antennas can be used in place of spatial arrays where compact UWB multiantenna systems are needed.

Increasing Channel Capacity of an Ultrawideband MIMO System Using Vector Antennas

Various embodiments of a multi-mode antenna are described. The antenna is preferably constructed having a first inductor coil and a second inductor coil. A plurality of shielding materials are positioned throughout the antenna to minimize interference of the magnetic fields that emanate from the coils from surrounding materials. The antenna comprises a coil control circuit having at least one of an electric filter and an electrical switch configured to modify the electrical impedance of either or both the first and second coils.

Multi-Mode Wireless Antenna Configurations

A method of fabricating a single structure multiple mode antenna is described. The antenna is preferably constructed having a first inductor coil that is electrically connected in series with a second inductor coil. The antenna is constructed having a plurality of electrical connections positioned along the first and second inductor coils. A plurality of terminals is connected to the electrical connections that facilitate numerous electrical connections and enables the antenna to be selectively tuned to various frequencies and frequency bands.

Method of fabricating a single structure multi mode antenna for wireless power transmission using magnetic field coupling

Various embodiments of a single structure multiple mode antenna are described. The antenna is preferably constructed having a first inductor coil that is electrically connected in series with a second inductor coil. The antenna is constructed having a plurality of electrical connections positioned along the first and second inductor coils. A plurality of terminals facilitates connection of the electrical connections thereby providing numerous electrical connection configurations and enables the antenna to be selectively tuned to various frequencies and frequency bands. An internal switch circuit is provided that facilitates electrical connection of the various terminals and frequency tuning.

Ajit Rajagopalan

Papers

Improving Power Transfer Efficiency of a Short-Range Telemetry System Using Compact Metamaterials

Increasing Channel Capacity of an Ultrawideband MIMO System Using Vector Antennas

Multi-Mode Wireless Antenna Configurations

Method of fabricating a single structure multi mode antenna for wireless power transmission using magnetic field coupling

Single structure multi mode antenna for wireless power transmission using magnetic field coupling having an internal switch circuit