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Antennas using the active frequency selective surface (AFSS) can achieve fast beam‐scanning ability at a low cost. In this study, a switched beam antenna with a high gain and 360° coverage in the horizontal plane is proposed. Twelve columns of AFSS form a cylindrical cavity and are transmissive or reflective to the incident electromagnetic waves under the control of PIN diodes. Benefiting from a coaxial continuous transverse stub array placed at the cavity centre and using 4 units to generate a high gain omnidirectional radiation, the proposed antenna can realise a highly directive switched beam. An antenna prototype is designed, fabricated and measured. Results show that it achieves a |S11| < −10 dB bandwidth of 12.9% and is able to sweep its beam around the azimuth plane with a high gain up to 13.6 dBi at 5.8 GHz working frequency. [ABSTRACT FROM AUTHOR]

A new rasorber with a switchable transmission/reflection band between two wide absorption bands is proposed based on an ultrathin low‐profile frequency selective surface. To miniaturise the periodicity in the lossy layer, convoluted elements and lumped capacitors are applied, while in the bandpass layer, non‐resonate elements are implemented with PIN diodes embedded. Moreover, a square loop loaded with resistors is introduced to the bottom of the lossy layer, which consequently extends the bandwidth of the high‐frequency absorption band without an increase in thickness. The simulation indicates that the proposed design presents a switchable transmission/reflection band in two‐sided absorption bands with a periodicity of 0.089λL (wavelength at the lowest operating frequency) and thickness of 0.066λL. Angular stability and polarisation insensitivity are also obtained due to the low profile and symmetry. A prototype was fabricated and measured, according to which the switchable transmission band covers 3.67–3.93 GHz; the absorption bands cover 2.37–3.23 GHz and 4.09–6.63 GHz in the OFF state of the diodes, and 2.23–3.02 GHz and 4.01–6.53 GHz in the ON state. As reasonable agreements between the measurement and simulation results are observed, the performance of the design is verified. [ABSTRACT FROM AUTHOR]

Usually, Radar signature of an object is reduced using microwave absorber surface. Recently, another approach based on time‐modulated frequency‐selective surfaces has been developed to deceive Radar detection by selectively generating harmonics/sidebands. Here, a polarization‐insensitive time‐modulated frequency‐selective surface is proposed that works over a broad frequency range. The design employs a PIN diode‐based switchable frequency‐selective surface to switch between the two states of reflection coefficient. Monochromatic incident electromagnetic (EM) wave, upon reflection from the surface is modulated by a periodic time‐varying reflection coefficient to generate several harmonics/sidebands along with the incident frequency. In the frequency spectrum of the reflected EM wave, the power of the incident frequency component is suppressed below that of the sidebands. The time‐modulated frequency selective surface has the capability to suppress the incident frequency component for any incident EM wave in 2–4 GHz that is S band, as well as generate spurious reflection sidebands. [ABSTRACT FROM AUTHOR]

A switchable polarisation conversion/in‐phase reflection metasurface (PCIPR‐MS) based on a Pin diode is proposed in this study. By changing the working state of the Pin diode, the PCIPR‐MS can be used as a polarisation conversion metasurface (PCM) and an artificial magnetic conductor (AMC), respectively. Furthermore, the designed PCIPR‐MS can be arranged into a checkerboard surface to integrate with the antenna, which means that the PCIPR‐MS can be flexibly switched to control the radiation and scattering characteristics of the antenna in a time‐sharing manner. The simulation results show that the 3‐dB axial ratio (AR) bandwidth is 4.31 to 6.14 GHz (35%) with the application of the AMC as the metal ground plane of the antenna in the radiation state, and the right‐hand circularly polarised (RHCP) gain is enhanced by more than 1.5 dB from 4.65 to 5.80 GHz in a low‐profile compared with the reference antennas. By using the PCM, phase cancelation is achieved in the scattering state of the antenna to realise the low‐RCS characteristics. [ABSTRACT FROM AUTHOR]

This study presents a simple and low‐profile cylindrical dielectric resonator antenna (CDRA) for the fifth‐generation (5G) band (3.5 GHz) with switchable polarization. The antenna can operate with linear or circular polarization (right‐handed circular polarization [RHCP] or left‐handed circular polarization [LHCP]) by changing the states of the PIN diodes below the CDRA, while keeping the same operating frequencies. The antenna operates at three modes (Mode 1, Mode 2, and Mode 3). It exhibits linear polarization in Mode 1, RHCP in Mode 2, and LHCP in Mode 3. The 10‐dB bandwidths of 750 MHz (3.1–3.85 GHz), 950 MHz (3.03–3.98 GHz), and 960 MHz (3.03–3.99 GHz) are noted for Mode 1, Mode 2, and Mode 3, respectively. The 3‐dB axial ratio bandwidth of 22.2% (3.09–3.86 GHz) and 21.4% (3.08–3.82 GHz) is achieved for Mode 2 and Mode 3, respectively. The reported antenna has high gain (>5.25 dBi for all operating modes) and high radiation efficiency (>79.8% for all operating modes). The proposed antenna is suitable for use in polarization diversity applications. [ABSTRACT FROM AUTHOR]

An innovative four‐bit second order multifunction active frequency selective structure controlled via four PIN diodes with nine different combinations is introduced. The proposed design is equipped with electromagnetic switching, frequency switching and polarization selection at two passbands. The coding states 0000 and 1111 offer transmission to the passbands centred at 1.96 and 4.98 GHz frequencies and shield to the bands centred at 4.98 and 1.96 GHz for transverse electric (TE)/transverse magnetic (TM) waves, respectively. The coding state 1010 offers transmission to the TE and TM waves at 1.96 GHz and 4.98 GHz, respectively and shields the TM and TE waves at 1.96 GHz and 4.98 GHz, respectively. Contrarily, the coding state 0101 offers transmission to the TE and TM waves at 4.98 GHz and 1.96 GHz, respectively and shields the TE and TM waves at 1.96 GHz and 4.98 GHz, respectively. The coding states 1000/0100 and 1101/1110 allow transmission to the TE wave at 1.96 and 4.98 GHz frequencies, respectively and shield to both the passbands at TM wave. Conversely, the coding states 0001/0100 and 1011/0111 allow transmission to the TM wave at 1.96 and 4.98 GHz frequencies, respectively and shields to both the passbands at TE wave. The coding state 1100/0011 provides shield to all the frequencies below 7.7 GHz. The designed structure is validated through the measured response of the fabricated prototype. [ABSTRACT FROM AUTHOR]

Broadband polarisation reconfigurable antenna based on crossed dipole and parasitic elements is proposed in this study, which can switch among three polarisation modes, i.e. linear polarisation, left‐hand circular polarisation and right‐hand circular polarisation. The proposed antenna consists of two crossed dipoles fed by a 3/4 square ring, two microstrip feeding elements etched at the centre of the upper and lower sides of the dielectric substrate, and three sets of microstrip parasitic elements helping broaden the axial‐ratio (AR) bandwidth. Four PIN diodes are embedded between each crossed dipole and the microstrip feeding element, which enable the polarisation reconfigurability. The working principle of polarisation reconfigurability is analysed in detail. The measured results show that the proposed antenna has a −10 dB overlapped impedance bandwidth of 63.5% (2.04–3.94GHz) and the 3 dB overlapped AR bandwidth is about 54.5% (2.4–4.2GHz), resulting in a wide overall bandwidth of 48.6% (2.40–3.94GHz). Besides, the measured peak gain of this antenna reaches up to 8.5 dBi. The proposed antenna can be a good candidate for 2.45GHz WiFi, LTE 4G, and sub‐6GHz 5G applications. [ABSTRACT FROM AUTHOR]

An innovative four‐bit second order multifunction active frequency selective structure controlled via four PIN diodes with nine different combinations is introduced. The proposed design is equipped with electromagnetic switching, frequency switching and polarization selection at two passbands. The coding states 0000 and 1111 offer transmission to the passbands centred at 1.96 and 4.98 GHz frequencies and shield to the bands centred at 4.98 and 1.96 GHz for transverse electric (TE)/transverse magnetic (TM) waves, respectively. The coding state 1010 offers transmission to the TE and TM waves at 1.96 GHz and 4.98 GHz, respectively and shields the TM and TE waves at 1.96 GHz and 4.98 GHz, respectively. Contrarily, the coding state 0101 offers transmission to the TE and TM waves at 4.98 GHz and 1.96 GHz, respectively and shields the TE and TM waves at 1.96 GHz and 4.98 GHz, respectively. The coding states 1000/0100 and 1101/1110 allow transmission to the TE wave at 1.96 and 4.98 GHz frequencies, respectively and shield to both the passbands at TM wave. Conversely, the coding states 0001/0100 and 1011/0111 allow transmission to the TM wave at 1.96 and 4.98 GHz frequencies, respectively and shields to both the passbands at TE wave. The coding state 1100/0011 provides shield to all the frequencies below 7.7 GHz. The designed structure is validated through the measured response of the fabricated prototype. [ABSTRACT FROM AUTHOR]

Here, a novel geometry of dual-band polarisation reconfigurable patch antenna is presented. The proposed prototype design consists of two orthogonal arms as a patch, an inclined slotted asymmetric pentagonal-shaped ground plane and a PIN diode with a biasing circuit. The polarisation reconfiguration is controlled via ON/OFF states of the PIN diode. The unique feature of the proposed antenna design is that it provides polarisation reconfiguration without considerable deviation in -10 dB impedance bandwidth (IBW) frequency response. The proposed antenna has a measured -10 dB IBW of 49.28% (3.96-6.55 GHz) and 41.47% (4.3-6.55 GHz) in the ON-state and OFF-states of the PIN diode, respectively. In the ON-state of the PIN diode, the antenna exhibits a dual-band circular polarisation. The first 3 dB axial ratio (AR) band is 4.5% (4.3-4.5 GHz) and the second 3 dB AR band is 17.69% (5.1-6.09 GHz). The proposed antenna exhibits almost uniform gain over the entire operating axial-ratio bandwidth, with peak CP gain of 2.8 dBic. The suggested antenna has a wide -10 dB IBW, and it is suitable for Cband wireless applications. [ABSTRACT FROM AUTHOR]

A flexible dual-band dual-polarised CPW-fed monopole antenna with discrete-frequency reconfigurability is presented here. In the proposed antenna, to achieve dual-band performance, a U-slot is incorporated within the CPW-fed monopole. The antenna is fabricated on a flexible and transparent substrate so that it can be used for conformal applications. The effect of antenna bending on its performance is discussed here. Further, the proposed antenna structure is extended to achieve discretefrequency reconfigurability. Two p-i-n diodes are incorporated within the monopole to achieve reconfigurability of higher band. A simplified equivalent circuit of the reconfigurable antenna is also presented and validated using full wave EM simulation. To validate the proposed structure, dual-band antenna and discrete frequency reconfigurable antenna have been fabricated and tested. [ABSTRACT FROM AUTHOR]

In this study, an ultra-wideband (UWB) monopole antenna with a dynamically reconfigurable notch band, along with the associated RF-triggered power management unit (PMU) that enables the dynamic reconfigurability, are presented. The UWB monopole antenna has a rectangular slot which hosts a J-shaped stub, electrically connected with the radiator using one PIN diode switch. When the diode is OFF, the monopole antenna has a UWB characteristic, while when it is turned ON a frequency notch is created at 5.6 GHz. The diode is fed from a PMU that consists of a rectenna and a DC-to-DC active booster. When the rectenna that consists of a patch antenna and a rectifier receives a -11 dBm or higher 5.6 GHz signal, it rectifies the RF signal into a sufficiently high DC voltage. The rectified DC voltage is applied to the cascaded DC-to-DC booster as enabling signal, and the booster provides at its output terminal sufficient DC power to actuate the PIN diode and thus dynamically reconfigure the UWB antenna. The dynamically reconfigurable notch band is created immediately in response to the reception of an external, -11 dBm RF signal at 5.6 GHz, and it disappears in real time immediately after the external RF signal is removed. [ABSTRACT FROM AUTHOR]

A band- and frequency-reconfigurable circularly polarised (CP) filtenna that exhibits good selectivity and out-of-band rejection in both its wideband and continuously tunable narrowband states is reported for cognitive radio (CR) applications. The filtenna provides two switchable operational states: a wideband state from 2.52 to 3.53 GHz for sensing and a tunable state of narrowband states from 2.44 to 3.19 GHz for communications. The corresponding 3-dB axial ratio bandwidths completely overlap these impedance bandwidths. A single PIN diode is utilised to switch between these two operational states to achieve the band-reconfigurable performance. Two varactor diodes are employed to realise the frequency-reconfigurable performance by facilitating a continuous shift of the narrowband states over the operational communication frequencies. [ABSTRACT FROM AUTHOR]

A new planar beam-switching dipole antenna is proposed in this study. It consists of a peanut-shaped dipole with folded slots and a pair of parasitic elements with two positive intrinsic-negative (PIN) diodes. The feeding structure is made up of a short microstrip line, which is excited by a differential signal. Based on the Yagi–Uda antenna, pattern reconfigurability is realised by changing the states of PIN diodes. The proposed antenna is simulated, fabricated and measured. Experimental results indicate that the proposed antenna obtains an impedance bandwidth for |Sdd| < −10 dB of 13.7% from 3.25 to 3.73 GHz. The average gain of the antenna is about 5.7 dBi, with the radiation efficiency up to 60%. The antenna realises the radiation bandwidth of 11.6% covering 3.25–3.65 GHz. The proposed antenna shows good performances, which makes it suitable for the applications of 5G communication system. [ABSTRACT FROM AUTHOR]

This study presents a tunable dual-band gallium nitride (GaN) power amplifier (PA) operating in L-band. The first band is aimed near the lower edge of the L-band, 1 GHz, and the second band is aimed near the upper edge of the L-band, 2 GHz, which is located around the second harmonic of the first band. A pin diode-based tunable load matching circuit is proposed and designed in order to present the optimum fundamental and harmonic load impedances to the transistor in both operating bands for maximum efficiency and output power. A method of controlling the tunable load matching circuit according to the input frequency is proposed by the design of a band-selective power detection circuit incorporated into the source matching circuit of the PA. The implemented PA delivers 41.5 dBm output power with 81.3% drain efficiency (DE) at 920 MHz and 41 dBm output power with 60.2% DE at 1720 MHz. [ABSTRACT FROM AUTHOR]

A novel magneto-electric dipole antenna with wide H-plane beamwidth, triple-linear polarisation and frequency reconfiguration is proposed for 5G communications. In this study, the radiated dipoles are designed with the arc-shaped planes to exhibit wide H-plane performance. A bent cross-dipole feed with PIN diodes and varactor diodes inserted into its four arms at different altitudes is utilised to excite and control the antenna. Consequently, a measured wide beamwidth ranging from -67° to 67° can be achieved in H-plane. In addition, the height of the proposed antenna decreased about 30% due to the bent designs. Finally, by controlling the PIN diodes and varactor diodes, the three kinds of linear polarisations and frequency reconfiguration functionalities for 2G/3G/LTE/5G applications can also be easily obtained. With the above-mentioned features, the proposed antenna well suits for intelligent base-station communications. [ABSTRACT FROM AUTHOR]

A frequency reconfigurable printed microstrip-fed patch antenna is proposed here. The antenna consists of a microstrip feed connected to a circular radiating element divided into three patches which are connected through silicon PIN diodes used as switches for achieving reconfigurability as being cheap and easy to implement having high switching capabilities. The slots of different shapes are etched out in all the three patches to cover all used wireless local area network (WLAN) frequency bands, including 2.4, 3.6, 4.9, 5.1, and 5.9 GHz. A bias tee is designed and connected to provide a DC bias to the PIN diodes. A prototype of the reconfigurable antenna is fabricated and measured along with the bias tee. The measured and simulated results are found in good agreement. [ABSTRACT FROM AUTHOR]

A tunable low-pass to bandpass switchable filter is presented in this study. The proposed structure consists of two concentric resonators. Along with varactors, outer resonator is also loaded with a PIN diode switch. The switching conditions of the PIN diode - OFF lead to a low-pass filter (LPF) and ON lead to a bandpass filter. At the ON condition of the switch, the outer resonator behaves as two resonators which are coupled to each other through two ways - inductively coupled through via hole and capacitively coupled through the varactor loaded between the resonators. The coupling coefficients between the two grounded resonators are controlled using varactors to achieve constant fractional bandwidth (CFBW) tunability. The third CFBW tunable band with bandpass characteristic having three transmission zeros across the passband is achieved using inductively coupled inner resonators. A filter is designed, simulated and fabricated. The response shows a tunable LPF having a tuning range of 0.55-1.4 GHz. One tunable CFBW bandpass response with a tuning range of 0.850-1.25 GHz is achieved with a CFBW of 64%. The third tunable band with bandpass filtering behaviour is achieved with a tunable range of 1.04-1.6 GHz with a CFBW of 13.4%. [ABSTRACT FROM AUTHOR]

A beam reconfigurable antenna with high gain is presented with low complexity switching capability. The design consists of a printed dipole antenna with reconfigurable parasitic elements that are combined with a partially reflecting surface to provide main lobe radiation pattern switching between boresight and close to end-fire at an operating frequency of 1.81 GHz. The reconfigurability is achieved using only two PIN diodes and the measured gain of the antenna is 8.5 dBi gain at boresight and 14.3 dBi towards the end-fire direction. [ABSTRACT FROM AUTHOR]

Reconfigurable frequency-selective surfaces (RFSSs) are of significant interest in applications, such as secure communication systems or tunable radomes, to improve indoor communication and smart antennas. In order to change the frequency-selective surface (FSS) characteristics, and therefore its frequency response, conventional methods include loading with active semiconductor devices such as varactors, PIN diodes, Schottky diodes and radio-frequency microelectromechanical system. Another possibility is the use of mechanical adjusts, such as spring resonators or mechanical rotation. When PIN diodes are used, commonly only the reverse and forward regions, OFF and ON states, respectively, are considered. In this study, the implementation of an RFSS is described, using PIN diodes as active components. The RFSS is based on the four-arms star geometry, and initial design equations and procedures are presented. Numerical and measured results are shown for different project stages, with a very good agreement. In addition to obtaining two distinct resonant frequencies, due to the OFF and ON states, a third situation is included, considering the PIN diode threshold region when the FSS becomes practically transparent, which is an interesting feature with potential applications. [ABSTRACT FROM AUTHOR]

A reconfigurable multiple-input multiple-output (MIMO) antenna design for the smartphone with a metal frame capable of covering hepta-band LTE/WWAN is proposed. The proposed antenna has four monopole slots (two long slots and two short slots) etched on the top and bottom side of the system ground, respectively. Two PIN diodes are inserted into the two long monopole slots. When these two PIN diodes are OFF, the two long monopole slots can generate the desired lower-band (824-960 MHz) which can be applied in a 2 × 2 MIMO system. When these two PIN diodes are ON, the corresponding lengths of these two long slots are decreased to the same length as the short slots. Then these four ports can excite the desired upperband (1710-2690 MHz) which can be used for a 4 × 4 MIMO system. In addition, the performances of the proposed antenna including the return loss, isolation, efficiency, envelop correlation coefficient, mean effective gain, and channel capacity are presented. [ABSTRACT FROM AUTHOR]

This study proposes an electronically switched parasitic array radiator (ESPAR) antenna at 5.9 GHz to meet the intelligent transportation systems standards. This antenna offers pattern switching capability with three distinct radiation patterns, i.e. one quasi-omni and two directives in opposite directions, by controlling the mutual coupling at the parasitic elements with PIN diode switches. A considerable gain increase of up to 3 dB is achieved in the directive mode, while maintaining a satisfying impedance matching between the switching states. The compact ESPAR antenna is printed on a low loss Rogers dielectric and consists of one active and two parasitic monopoles. S11 and radiation pattern results are presented, derived from both simulations and measurements, exhibiting a close agreement. [ABSTRACT FROM AUTHOR]

In this study, the authors present a simple reconfigurable multiband antenna with two PIN diode switches for worldwide interoperability for microwave access (WiMAX)/wireless local area networks (WLAN) applications. The antenna permits reconfigurable switching in up to ten frequency bands between 2.2 and 6 GHz, with relative impedance bandwidths of around 2.5 and 8%. The proposed antenna has been simulated using computer simulation technology microwave studio software and fabricated on an FR-4 substrate. It is compact, with an area of 50 x 45 mm², and has a slotted ground substrate. Both measured and simulated return loss characteristics of the optimised antenna show that it satisfies the requirement of 2.4/5.8 GHz WLAN and 3.5 GHz WiMAX antenna applications. Moreover, there is good agreement between the measured and simulated results in terms of radiation pattern and gain. [ABSTRACT FROM AUTHOR]

A small-size reconfigurable smartphone antenna using a PIN diode for WWAN/LTE and global navigation satellite system (GNSS) smartphone application is presented. When the diode is in 'OFF' state, a T-shaped feeding strip and an encircled T-shaped parasitic shorted strip formed a coupled-fed antenna, which achieves a low-wideband covering GSM850/900 bands and a high-wideband covering GSM1800/1900/UMTS2100/LTE2300/2500 bands. When the diode is in 'ON' state, a loop antenna working at 1/2 wavelengths is formed to cover the bands of GNSS, which includes four positioning systems (COMPASS, GALILEO, GPS and GLONASS). In addition, the proposed antenna is easily printed on a small ground clearance of 375 mm2 without loading any lumped element. Also, the proposed simple and compact antenna is convenient to be optimised for desired bands. Finally, the good agreement of simulated and experimental results proves that the proposed antenna is suitable for practical mobile terminal equipment. [ABSTRACT FROM AUTHOR]

A selectable multiband isolation of single pole double throw (SPDT) switch with switchable transmission line stub resonators for applications of WiMAX and LTE in 2.3 and 3.5 GHz bands is presented. Two SPDT switches are presented. (Design 2) either allows selecting only one band while unselecting the other or selecting both of them. However, (Design 1) does not allow so. The transmission line stub resonator used in this design is an open stub resonator with quarter wave of the electrical length. By using a simple mathematical model, the theory of the transmission line stub resonator was discussed where it can be cascaded and resonated at centre frequencies of 2.3 and 3.5 GHz. Moreover, the cascaded transmission line stub resonators can be reconfigured between all-pass and band-stop responses using discrete PIN diodes. The key advantage of the proposed SPDT with switchable transmission line stub resonators is a multiband high isolation with a minimum number of PIN diodes. Therefore, the simulated and measured results showed the followings: <3 dB of insertion loss, >10 dB of return loss and >30 dB of multiband isolation in 2.3 and 3.5 GHz bands. [ABSTRACT FROM AUTHOR]

In this study, a Koch snowflake frequency reconfigurable antenna for wideband applications is presented including experimental verification. The frequency reconfigurable approach is obtained for UHF band using RF PIN diodes, lumped capacitor and inductors. Proposed antenna is compact, therefore, it can be used as an array element. It has three measured frequency bands. These bands are: case I, 3.34– 4.52 GHz (30%); case II, 2.2–3.4 GHz (43%); and case III, 1.45–4.1 GHz (95.49%). In cases I and II, two different bands are obtained and case III covers almost the frequency band of case I and case II. Thus, the impedance bandwidth of the proposed antenna provides continuous wideband frequency coverage from 1.45 to 4.52 GHz (103%). In addition, the measurements are carried out to validate the performance of the antenna. The proposed antenna has good agreement between simulated and measured results with reasonably low cross polarisation. [ABSTRACT FROM AUTHOR]

A back-to-back microstrip patch antenna with a switchable pattern is proposed for WLAN applications. The patch elements, printed on FR-4 substrates with a common ground plane, are switched with a single-pole double-throw PIN diode circuit. Switching the feed selects either of two identical radiation patterns in the opposing hemispheres for spatial diversity that would benefit a distributed network. [ABSTRACT FROM AUTHOR]

The design of a frequency-reconfigurable (FR) multiple-input-multiple-output (MIMO) monopole antenna with a wide-continuous tuning range in handheld devices is presented. The antenna consists of two symmetrical FR monopole elements and a FR defected-ground structure (DGS). The monopole elements have two sections, sections 1 and 2, connected together using a PIN diode. Section 1 alone generates a high-frequency band at 2.26 GHz. By turning ON the PIN diode, sections 1 and 2 will be connected together to generate a low-frequency band at 1.93 GHz. The DGS is used to achieve high isolation between the monopole elements and reconfigurable to follow the low- or high-frequency operations. Simple and novel biasing circuits employing only 3 DC wires are designed to control these diodes. The methodology of using the design in other frequency bands is proposed. Results on S-parameters, radiation pattern, realized peak gain and envelope-correlation coefficient (ECC) are presented. Measured results show that the antenna has a wide-frequency tuning range from 1.88 to 2.64 GHz, covering the long-term-resolution (LTE) 1, 2, 23, 25, 33-37 and 39-40 bands with low mutual coupling and ECC of less than -20 dB and 0.5, respectively. The effects of the feeding cable used in measurement are studied. [ABSTRACT FROM AUTHOR]

This study presents a wearable antenna for a global positioning system-global system for mobile communication (GPS-GSM)-based anti-theft tracking system to be embedded in high-cost clothing and luggage accessories (such as leather bags). To assess the feasibility of this solution, a prototype antenna was designed mimicking the shape of one of the Levi Strauss & Co.'s logos, and it was fabricated using a conductive non-woven fabric on a layer of leather. Furthermore, to cover both the GPS L1 and the GSM-1800 bands with a single radiating element, positive-intrinsic-negative (PIN) diodes were employed to reconfigure the operating frequency of the antenna. Experimental data demonstrating the feasibility of the proposed design strategy are presented and discussed. [ABSTRACT FROM AUTHOR]

A new type of pattern-reconfigurable reflectarray phased by reconfigurable unit cells that are centrally controlled by a laptop is presented. The proposed reflectarray with single-layer radiators employs a phasing element formed by a fixed-size circular ring attached by a variable-length arc phase delay line controlled by positive-intrinsic-negative diodes. The biasing network of the diodes is properly designed to minimise the interference between the radiating structure and the biasing circuit. To that end, the biasing circuit is placed on a substrate layer below the ground plane whereas the PIN switching diodes are embedded within radiators. The biasing signal is transmitted to the switching elements at the top layer using vias that penetrate the thin substrate layer, the foam layer and the ground plane. Investigations are carried out to verify the performances of the phasing element using a waveguide simulator. A reflectarray, which includes a C-band offset fed 8 × 8 elements, is configured to switch its main beam between 20° and 30° from the broadside direction. A biasing control unit is added to the fabricated reflectarray and activated using a laptop. The measured radiation patterns of the proposed reflectarray demonstrate a beam-switching characteristic from the broadside direction, which confirm the proposed design method. [ABSTRACT FROM AUTHOR]

In this study, a reconfigurable planar inverted-F antenna (PIFA) with a parasitic strip line for a hepta-band wireless wide area network (WWAN)/long term evolution (LTE) mobile handset is proposed. The PIN diode is located between the end of the parasitic strip line and the protruded ground plane. Depending on the on/off-state of the PIN diode, the degree of coupling between the conventional PIFA and the parasitic line is controlled and the fundamental resonant frequency of the proposed antenna is adjusted. As a result, the fundamental resonant frequencies cover the (global system for mobile communication) GSM850 (824-894 MHz) and GSM900 (880-960 MHz) bands. By the parasitic strip line extended from the protruded ground plane, impedance matching at the higher-order modes (f2 and f3) is improved and the fourth resonant frequency f4 is remarkably decreased. The high band of the antenna is formed by combining these three higher-order modes to cover the GSM1800 (1710-1880 MHz), GSM1900 (1850-1990 MHz), universal mobile telecommunication system (UMTS) (1920-2170 MHz), LTE2300 (2305-2400 MHz) and LTE2500 (2500-2690 MHz) bands. [ABSTRACT FROM AUTHOR]

In this study, a novel reconfigurable antenna using a PIN diode is proposed for multi band (GSM900/1800/1900/ UMTS/LTE2300/2500) operation in mobile handsets. By adjusting the on/off state of the PIN diode, the reconfigurable antenna operates in a planar inverted-F antenna (PIFA) mode as well as a loop mode. The operating bandwidth at a low band is attributed to the PIFA mode. The broad bandwidth at a high band is easily achieved in the PIFA mode as well as the loop mode. It is observed from the measured results that this planar antenna exhibits an impedance bandwidth of ∼8.7% at the 920-MHz band and ∼48.3% at the 2250-MHz band. With the reconfigurable technology, the antenna can achieve a compact size of 27 ×10 ×1.6 mm3. [ABSTRACT FROM AUTHOR]

A compact reconfigurable microstrip slot antenna with switchable single and dual band notch functions for ultrawideband (UWB) applications is presented in this study. In the proposed structure, an additional resonance is excited by etching two symmetrical notches on the feed-line and thereby a UWB characteristic is obtained. Then, by cutting two slots on the radiating patch and embedding two positive-intrinsic-negative (PIN) diodes along these slots, switchable single and dual band notch performances are added to the antenna performance. By changing the bias states of the PIN diodes, the antenna is capable of exhibiting four different performances of UWB spectrum coverage, UWB coverage with single rejection of the wireless local area network (WLAN) band, UWB coverage with single rejection of the WiMAX and C-band spectrum, and UWB coverage with dual band notch function at the WLAN, the WiMAX and the C-band frequencies. Good agreement between the simulated and the measured results is achieved at different performances of the antenna. The designed antenna has a small size of 20 × 20 mm2 and the measured results reveal that the fabricated antenna has good radiation behaviour in the UWB frequency spectrum with switchable band notch functions at 3.15-3.85 and 5.43-6.1 GHz which can eliminate the UWB frequency band interference with the WiMAX, the C-band and the WLAN systems. [ABSTRACT FROM AUTHOR]

Radio-frequency identification (RFID) tags (passive kind) are typically not designed to include ultra-wide band (UWB) pulse generators, but may be in the future. The reason is that the very short pulses produced by the RFID tags could be used to estimate their positions with errors of solely a few centimetres using time difference of arrival techniques. Currently, the method most commonly used to estimate tag positions relies on received signal strengths (less accurate). An UWB pulse generator based on a PIN diode is presented in this study. This pulse generator was designed to produce a positive unipolar pulse for each high-to-low transition (1.8 V to 0) it receives at its input. This trigger signal is generated by a microntroller-based battery-free RFID tag. The end result is a pulse with an amplitude of ~300 mV and a duration of slightly <2 ns measured using a 50 Ω load. [ABSTRACT FROM AUTHOR]