This paper presents a planar monopole backed with a 2×1 array of Electromagnetic Band Gap (EBG) structures. The reflection phase of a single EBG unit cell has been studied and exploited towards efficient radiation of a planar monopole antenna, intended for wearable applications. The shape of the EBG unit cell and the gap between the ground and the EBG layer are adjusted so that the antenna operates at 2.45 GHz. The proposed antenna retains its impedance matching when placed directly upon a living human subject with an impedance bandwidth of 5%, while it exhibits a measured gain of 6.88 dBi. A novel equivalent array model is presented to qualitatively explain the reported radiation mechanism of the EBG-backed monopole. The proposed antenna is fabricated on a 68×38×1.57 mm 3 board of semi-flexible RT/duroid 5880 substrate. Detailed analysis and measurements are presented for various cases when the antenna is subjected to structural deformation and human body loading, and in all cases the EBG-backed monopole antenna retains its high performance. The reported efficient and robust radiation performance with very low specific absorption rate (SAR), the compact size, and the high gain, make the proposed antenna a superior candidate for most wearable applications used for offbody communication.

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A reconfigurable band-pass filter with switchable bandwidth, for wireless applications is demonstrated using a dual-mode microstrip square-loop resonator. The proposed filter has been designed on Rogers RO4003C and achieves switchable bandwidth by changing the length of two tuning stubs with the implementation of two strategically placed p-i-n diodes as switching elements. The filter was designed with a center frequency of 2.4 GHz and the two distinct operation states have bandwidths, 113 MHz (4.8%) with an insertion loss of 1.2 dB and 35 MHz (1.5%) with an insertion loss of 1.5 dB. The physical size of the fabricated reconfigurable filter including the implementation of the DC bias lines is comparable to the size of a conventional filter.

A novel dynamically reconfigurable bandpass filter (BPF) employing stepped impedance resonators (SIRs) that can operate as either a single-band or a dual-band filter is demonstrated. The reconfigurable BPF uses four p-in diodes as switching elements. With the four p-in diodes in the "OFF" state, the filter behaves as a low-loss (0.85 dB) single-band BPF with a passband around 2.45 GHz. The reconfigurable SIR filter can operate as a dual-band bandpass filter with two center frequencies at 1.6 GHz and 2.45 GHz. The diodes are dynamically set to the "ON" state in the presence of a 1.6 GHz RF signal that is received by an RF triggered power management unit (PMU), integrated on the back side of the microstrip filter in a dual-layer architecture. The RF triggered PMU consists of a PIFA antenna, a highefficiency voltage doubler rectifier (47% at-13 dBm) and an active dc-to-dc power booster. The rectified output voltage is used as the enabling voltage for the dc-to-dc power booster. This, in turn, provides the required dc power for the diodes biasing. The filter switches from single-band to dual-band when a wireless input RF signal (>-13 dBm) is received by the RF triggered PMU's antenna. Index Terms-Microwave filter, reconfigurable, rectenna wireless power transfer. I. INTRODUCTION HERE has been an increasing demand for switchable and reconfigurable microwave devices, such as filters for wireless communication systems, where several different wireless devices co-exist and share the same frequency spectrum. Band pass filters (BPFs) with multi-frequency response and high stopband rejection are widely used, therefore reconfigurable BPFs can be utilized for controlling either standalone signals or combinations of information signals, with different frequency spectrum characteristics [1], [2]. In [1] a