Benjamin D. Braaten

A Self-Adapting Flexible (SELFLEX) Antenna Array for Changing Conformal Surface Applications

A phased-array test platform for studying the self-adapting capabilities of conformal antennas is developed and presented. Specifically, a four-port 2.45-GHz receiver with voltage controlled phase shifters and attenuators is designed along with four individual printed microstrip patch antennas attached to a conformal surface. Each antenna is connected to the corresponding receiver port with a flexible SMA cable. It is shown that with appropriate phase compensation, the distorted radiation pattern of the array can be recovered as the surface of the conformal array changes shape. This pattern recovery information is then used to develop a new self-adapting flexible 1 × 4 microstrip antenna array with an embedded flexible sensor system. In particular, a flexible resistive sensor is used to measure the deformation of the substrate of a conformal antenna array, while a sensor circuit is used to measure the changing resistance. The circuit then uses this information to control the individual voltage of the phase shifters of each radiating element in the array. It is shown that with appropriate phase compensation, the radiation properties of the array can be autonomously recovered as the surface of the flexible array changes shape during normal operation. Throughout this work, measurements are shown to agree with analytical solutions and simulations.

Reconfigurable UWB Antenna With RF-MEMS for On-Demand WLAN Rejection

A MEMS reconfigurable ultra-wideband (UWB) antenna that rejects on-demand all WLAN signals in the entire 5.15 to 5.825 GHz range (675 MHz bandwidth) is presented. The antenna design, miniaturization procedure, and monolithic integration with the MEMS and biasing network on SiO2 Quartz substrate are described. The integration challenges are addressed and the work is presented in a way that is useful for antenna engineers. A method to vary the rejection bandwidth is also provided. The fabricated prototype is conformal and single-sided. The antenna is measured using a custom-built platform at a university laboratory. Results indicate a successful integration and minimal interference of the MEMS and biasing circuitry with the antenna, paving the road for more integrated reconfigurable antennas on SiO2 using MEMS technology. Such antennas can improve UWB, WLAN and cognitive radio communication links.

A Novel Compact UHF RFID Tag Antenna Designed With Series Connected Open Complementary Split Ring Resonator (OCSRR) Particles

A novel compact planar antenna for passive UHF radio frequency identification (RFID) tags is presented. Instead of using meander-line sections, much smaller open complementary split ring resonator (OCSRR) particles are connected in series to create a small dipole with a conjugate match to the power harvesting circuit on the passive RFID tag. The manufactured (prototype) OCSRR RFID tag presented here has an antenna input impedance of 15.8 + J142.5 Ω at a frequency of 920 MHz and a max read range of 5.48 m. This performance is achieved with overall tag dimensions of 0.036λ0 × 0.17λ0 where λ0 is the free space wavelength of 920 MHz.

A Printed Rampart-Line Antenna with a Dielectric Superstrate for UHF RFID Applications

A printed Rampart line antenna with a dielectric superstrate for passive radio frequency identification (RFID) tags is presented. A design process is outlined to determine the number of elements used in the rampart line antenna to achieve the required gain for the desired read range. An inductive loop is then added to the port to match the antenna with the passive tag circuitry. It is shown that a passive tag with a printed Rampart line antenna and a dielectric superstrate can achieve comparable read ranges to commercially available passive RFID tags.

A Frequency Reconfigurable Transmitter Antenna With Autonomous Switching Capabilities

Frequency reconfigurable antennas have many benefits that can be used to improve the performance of wireless systems. Then again, many existing multiband systems cannot use a frequency reconfigurable antenna because of the additional control signals required to operate the antenna. In this communication, an autonomous frequency reconfigurable antenna topology that does not require these control signals from the radio is presented. To control the antenna, a power splitter and bandpass filter is used to pass a portion of the RF power driving the antenna in a particular band to voltage-doubling circuitry. This voltage-doubler circuit is then used to convert the RF signal into a DC output control voltage which then in turn controls the reconfigurable features of the antenna. By setting the bandpass filter to one of the reconfigurable frequencies, RF power can then be used to reconfigure the antenna in a specific band while not reconfiguring in other bands. This flexibility makes this design very useful for existing and future cost effective wireless systems.

A Compact Meander-Line UHF RFID Tag Antenna Loaded With Elements Found in Right/Left-Handed Coplanar Waveguide Structures

A new planar meander-line antenna for passive UHF radio frequency identification (RFID) tags is presented. Specifically, a meander-line antenna is loaded periodically with coplanar waveguide (CPW) LC elements traditionally found in right/left-handed waveguide structures. It is shown that by using the antenna presented in this letter in a prototype passive UHF RFID tag, effective read ranges up to 4.87 m can be achieved. Many different dielectric substrates and CPW-LC load dimensions are investigated to illustrate how the input impedance, gain, and overall dimensions of the antenna are affected by these structural differences. It is shown that the overall dimension of the meander-line antenna can be reduced by slightly more than 18% with the introduction of the CPW-LC elements to the design. Several of the simulation results are validated by comparison with measurements.

A Miniaturized Dual-Band MIMO Antenna for WLAN Applications

This letter reports on a compact planar dual-band Multiple-Input and Multiple-Output (MIMO) antenna for Wireless Local Area Network (WLAN) applications. The proposed antenna primarily consists of two meandered monopole radiators that are decoupled by introducing a folded Y-shape isolator element and it is shown that the edge coupling between the radiators and isolator introduces the resonance at the lower band. The miniaturization is achieved by passing the signal on to the bottom layer where a meandered line conductor introduces a broadside coupling with the radiator, originating the higher band resonance. The antenna operates between 2.4 GHz to 2.5 GHz and 5.45 GHz to 5.65 GHz with an isolation of more than 25 dB and 15 dB, respectively. The antenna measures only 19 ×23 mm2.

A Compact Dual-Band EMI Metasurface Shield With an Actively Tunable Polarized Lower Band

In this letter, a compact tunable metasurface for dual-band electromagnetic interference (EMI) shielding is being proposed. In particular, Jerusalem crosses intersecting diagonally are used to design and synthesize a prototype metasurface shield. It has been shown that a finite 4 × 3 array of the Jerusalem crosses can be used for EMI shielding in the 900 MHz and 1.8-GHz GSM bands. Then, to develop an active shield that is tunable, varactor diodes were attached to the dual-band metasurface. Measurements have shown that the lower band of the metasurface can be changed (tuned) with various control voltages. Finally, simulation, equivalent circuit computations, and measurements are shown to agree.

A Compact CSRR-Enabled UWB Diversity Antenna

The purpose of this letter is to introduce a compact ultrawideband (UWB) diversity antenna with a very low envelope correlation coefficient (ECC). The design employs a hybrid isolation enhancing and miniaturization technique. The antenna consists of two counter facing monopoles, and is miniaturized by using not only inverted-L stubs but also a complementary split-ring resonator (CSRR) on the ground plane. The added components enhance isolation and enable tighter packing of the antennas. The result is a very compact multiple-input–multiple-output (MIMO) array with an overall size of 23

A Compact Dual-Band Bow-Tie Slot Antenna for 900-MHz and 2400-MHz ISM Bands

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