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This paper presents a frequency reconfigurable antenna fed by a coplanar waveguide (CPW). The antenna is able to switch between narrowband operation, centred at 5.8 GHz, and wideband operation in the range of 3.5 GHz to 5.97 GHz. It consists of an ellipse‐shaped wideband antenna integrated with a bandpass filter for narrowband operation. A pair of rectangular resonators with stubs is implemented at the ground plane to alter the electrical length.When a pair of integrated p‐i‐n diodes are turned OFF, a passband is realized in conjuction with two stopbands to suppress unwanted frequencies. On the other hand, wideband operation is realized when the end of the slot is shorted by eliminating the function of resonator. The overall size of the proposed antenna is 37.8 × 49 mm2, inclusive of the DC biasing circuit. Simulated and measured for radiation pattern and reflection coefficient are carried out to compare the results. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 59:171–176, 2017

Q-factor constraints are usually imposed on conductor loops employed as proximity range High Frequency Radio Frequency Identification (HF-RFID) reader antennas to ensure adequate data bandwidth. However, pairing such low Q-factor loops in inductive energy transmission links restricts the link transmission performance. The contribution of this paper is to assess the improvement that is reached with a two-stage design method, concerning the transmission performance of a planar square loop relative to an initial design, without compromise to a Q-factor constraint. The first stage of the synthesis flow is analytical in approach, and determines the number and spacing of turns by which coupling between similar paired square loops can be enhanced with low deviation from the Q-factor limit presented by an initial design. The second stage applies full-wave electromagnetic simulations to determine more appropriate turn spacing and widths to match the Q-factor constraint, and achieve improved coupling relative to the initial design. Evaluating the design method in a test scenario yielded a more than 5% increase in link transmission efficiency, as well as an improvement in the link fractional bandwidth by more than 3%, without violating the loop Q-factor limit. These transmission performance enhancements are indicative of a potential for modifying proximity HF-RFID reader antennas for efficient inductive energy transfer and data telemetry links.