The advancement in wireless communications requires the integration of multiple radios into a single platform to maximize connectivity. In this paper, the design process of reconfigurable antennas is discussed. Reconfigurable antennas are proposed to cover different wireless services that operate over a wide frequency range. They show significant promise in addressing new system requirements. They exhibit the ability to modify their geometries and behavior to adapt to changes in surrounding conditions. Reconfigurable antennas can deliver the same throughput as a multiantenna system. They use dynamically variable and adaptable single-antenna geometry without increasing the real estate required to accommodate multiple antennas. The optimization of reconfigurable antenna design and operation by removing unnecessary redundant switches to alleviate biasing issues and improve the system's performance is discussed. Controlling the antenna reconfiguration by software, using Field Programmable Gate Arrays (FPGAs) or microcontrollers is introduced herein. The use of Neural Networks and its integration with graph models on programmable platforms and its effect on the operation of reconfigurable antennas is presented. Finally, the applications of reconfigurable antennas for cognitive radio, Multiple Input Multiple Output (MIMO) channels, and space applications are highlighted.

Reconfigurable Antennas: Design and Applications

RF MEMS technology was initially developed as a replacement for GaAs HEMT switches and p-i-n diodes for low-loss switching networks and X-band to mm-wave phase shifters. However, we have found that its very low loss properties (high device Q), its simple microwave circuit model and zero power consumption, its high power (voltage/current) handling capabilities, and its very low distortion properties, all make it the ideal tuning device for reconfigurable filters, antennas and impedance matching networks. In fact, reconfigurable networks are currently being funded at the same level-if not higher-than RF MEMS phase shifters, and in our opinion, are much more challenging for high-Q designs.

Tuning in to RF MEMS

A communication apparatus which communicates data with plural other communication apparatuses by performing wireless communication includes: plural antennas; a communication level obtainment unit which obtains communication levels for the antennas obtained when the communication apparatus performed the wireless communication with the other communication apparatuses; a count unit which counts, for each of the antennas, the number of established communications that is the number of one or more of the other communication apparatuses which successfully established communication through the antenna; an antenna selection unit which selects, when the total number of antennas whose numbers of established communications are greatest is more than one, one of the antennas corresponding to a communication level that is highest among communication levels of plural antennas of the other communication apparatus corresponding to the lowest communication level; and a transmission unit which broadcasts predetermined data to the other communication apparatuses through the selected antenna

Communication apparatus and communication method

An electronic device provides a capability of distinguishing between human tissue and a non-human object in proximity of a transmission source. In this manner, transmission power adjustments to the transmission source can be made selectively, depending on whether human tissue or a non-human object is detected in the proximity of the RF transmitter. Distinguishing between human tissue and other non-human-tissue objects in proximity of the transmission source provides for selective control of SAR adjustments. Accordingly, an electronic device can avoid certain communication performance reductions introduced by decreases in transmission power effected to comply with SAR standards by reducing transmission power when human tissue is detected in the proximity but not reducing transmission power when a non-human object (but no human tissue) is detected in the proximity.

Selective specific absorption rate adjustment

A wireless power transfer method for a wireless power transfer apparatus using full and half-bridge inverter topologies includes detecting whether or not a wireless power receiver (200) is present within a range of power being transferrable in a wireless manner, transmitting a detection signal to the wireless power receiver (200), receiving at least one of identification information and setting information from the wireless power receiver (200), receiving a control error packet from the wireless power receiver (200), and controlling an amount of power to be transferred by using the combination of a driving frequency, a duty cycle or a power signal phase to the full or half-bridge inverter.

Wireless power transfer method, apparatus and system

This paper presents a state-of-the-art discrete RF microelectromechanical systems (MEMS) tunable filter designed for 25-75-MHz operation. This paper also presents an enhanced model of the RF MEMS switch, which is used for accurate prediction of the tunable filter response. The two-pole lumped-element filter is based on digital capacitor banks with on-chip metal-contact RF MEMS switches and lumped inductors, and results in a tuning range of 3:1 with fine frequency resolution, and a return loss better than 13 dB for the entire tuning range. The relative bandwidth of the filter is 4 plusmn 1% over the tuning range and the insertion loss is 3-5 dB, limited mostly by the inductor Q and the switch loss. The IIP3 measurements prove that tunable filters with metal-contact series RF MEMS switches show extremely linear behavior (IIP3 > 68 dBm).

A 25–75-MHz RF MEMS Tunable Filter

Methods and systems for selecting one of a plurality of antennas to be used as a transmit antenna based on an orientation of a user device are described. A user device determines an orientation of the user device, and selects one of multiple antennas to use as a first transmit antenna based on the orientation of the user device. The user device transmits information using the first transmit antenna.

Antenna deployment switching for data communication of a user device

This paper demonstrates a design procedure for frequency tunable reconfigurable antennas based on the application of reactive loads. Unlike other design procedures, antennas of arbitrary geometry can be tuned utilizing the proposed design framework. The design technique utilizes the theory of network characteristic modes to systematically compute reactive load values required to resonate any antenna at many frequency points in a wide frequency range. For simplicity, a 1.2 m dipole antenna is used to demonstrate the design procedure by tuning it at four loading ports along the antenna body. Both simulations and measurements demonstrate wide frequency tunability characteristics of the dipole input impedance (tunability range wider than 1:4) while preserving the radiation pattern and polarization at seven different frequency states. Lastly, a loaded PIFA is briefly examined as a more complex application of the procedure.

Design of Frequency Reconfigurable Antennas Using the Theory of Network Characteristic Modes

A conceptual framework is proposed to systematically design antennas with broadband impedance and pattern characteristics using multiple reactive loads. Antennas of arbitrary geometry can have their bandwidths expanded using this technique. The technique is applied to a narrow band thin wire dipole antenna to demonstrate its main features. It is shown that the loaded antenna resonates a desired current over a wide frequency band. The loads are shown to require non-Foster elements when realized. Simulations demonstrate the broadband characteristics of both the dipole input impedance and radiation pattern.

Application of Characteristic Modes and Non-Foster Multiport Loading to the Design of Broadband Antennas

A method to design antennas with broadband characteristics. In an exemplary embodiment, a method comprises loading an antenna structure with multiple reactive loads. The multiple loads are synthesized by applying the theory of Characteristic Modes. Another exemplary embodiment includes an antenna adapted to have broadband characteristics. One example is a wire dipole antenna. In an exemplary embodiment, a loaded antenna may be adapted to resonate an arbitrary current over a wide frequency band. The loads may require non-Foster elements when realized. Exemplary embodiments may include the broadband characteristics of the both the input impedance at the terminal of the antenna as well as the radiation pattern.

Khaled Ahmad Obeidat

Papers

A 25–75-MHz RF MEMS Tunable Filter

Antenna deployment switching for data communication of a user device

Design of Frequency Reconfigurable Antennas Using the Theory of Network Characteristic Modes

Application of Characteristic Modes and Non-Foster Multiport Loading to the Design of Broadband Antennas

Implementation of ultra wide band (UWB) electrically small antennas by means of distributed non foster loading