Search

This communication presents an omnidirectional rectenna array with an enhanced RF power distributing strategy. The proposed rectenna array consists of three bidirectional subarray antennas, a $3\times $ 3 RF power distributing network, and a three-element rectifier array. Utilizing the $3\times $ 3 network to redistribute the varying RF power received by the three antennas, the RF-to-dc power conversion efficiency of the rectenna array can be enhanced under the illumination of electromagnetic (EM) waves with arbitrary incident angles. Measurement results reveal that the proposed rectenna array has an improved omnidirectional-harvesting capability compared with the design without RF power distributing strategy, thus can be readily used for RF energy-harvesting applications. [ABSTRACT FROM AUTHOR]

A wideband differentially fed dual-polarized dual-mode antenna is presented in this letter. Four slots are placed a square shape to construct the slot loop antenna, and the outer ground of the slot loop is bended to achieve a compact size. A simple out-of-phase power splitter with a wide bandwidth and accurate 180° phase difference is integrated with the radiator to feed the slot loop. The 1 and 2 λ modes of the slot loop antenna are excited with the differential feeding for a wide impedance bandwidth (IMBW). By loading the distributed inductors at the ends of each slot, a radiator size of 106 × 106 mm2 is obtained to cover LTE700/GSM850/GSM900 bands. Measured results show that the antenna has the IMBWs of 0.63–1.09 GHz (0.46 GHz, 53.5%) and 0.63–1.08 GHz (0.45 GHz, 52.6%) for the two input ports, isolation of more than 31.5 dB, and stable gain of around 7.15 ± 0.35 dBi for Port 1. [ABSTRACT FROM AUTHOR]

This letter presents two designs of pattern-reconfigurable wearable antennas for body-centric wireless communications (BCWC). The reconfigurabilities of these two designs are realized utilizing two totally different mechanisms. In the first design, two subantennas with different radiation patterns are integrated. With a reconfigurable feeding network, the design can switch between the two subantennas. In the second design, the antenna's internal structure can be reconfigured to perform different radiation patterns. Measured results verify that both antenna designs provide reconfigurable omnidirectional and directional radiation patterns. [ABSTRACT FROM AUTHOR]

This letter presents a reconfigurable antenna with sum and difference patterns for the applications of wireless local area network (WLAN) access points. The proposed antenna consists of a 2 × 2 circularly polarized (CP) stacked-patch antenna array and a switchable monopulse comparator network. Utilizing this comparator network to excite the CP antenna array, sum, azimuth difference, elevation difference, and bidifference beams are produced and can be switched by controlling the dc voltages on the p-i-n diodes. Measurement reveals that the antenna's return loss is better than 10 dB in the frequency ranges of 2.26–2.58 GHz, 2.24–2.62 GHz, 2.25–2.61 GHz, and 2–3 GHz at the sum, azimuth difference, elevation difference, and bidifference modes, respectively. The measured axial ratios, gains, and radiation patterns also show that this antenna can be applied to enhance the communication-area coverage capability for WLAN access points. [ABSTRACT FROM AUTHOR]

This letter presents two 2 × 2 polarization-insensitive dual-polarized rectenna arrays with different power combining strategies for wireless power transmission applications. With a dual-polarized antenna array, the incident wave can be received and decomposed into the horizontally and vertically polarized components, which are equally redistributed by a hybrid coupler. By this means, the efficiency of the rectenna, in which the power is equally input to the two rectifiers in parallel, is independent of the incident wave's polarization. Based on the equal power routing mechanism, two rectenna arrays using the RF and dc combining strategies are designed and analyzed. Measurement results show that both rectenna arrays are insensitive to the incident wave's polarization, and have their own advantages and disadvantages. [ABSTRACT FROM AUTHOR]

An airborne $K$ -band (18–26.5 GHz) array antenna is presented in this article. It takes the form of meandering waveguide structure to handle large power in a radar system. The magneto-electric (ME) dipole is used as the array element for the relative broad beamwidth. Good agreement is achieved between simulation and measurement. A single array element demonstrates impedance bandwidth of 19–24 GHz. The maximum gain is 10.76 dBi at 24.2 GHz with 3 dB gain bandwidth covering the whole $K$ -band. Symmetric radiation patterns on both the E- and H-planes are observed with 66° half power beamwidth. The $2\,\,\times2$ array has an impedance bandwidth of 19.9–22.8 GHz. The maximum gain is 16.2 dBi at 25.2 GHz with 3 dB gain bandwidth covering 19.4–26 GHz. Symmetric radiation patterns on both planes show 26° half-power beamwidth. Taking the advantage of 3-D printing technology to implement complex device, the water- and air-cooling channels are considered at the beginning of antenna design. A parametric study is conducted to analyze the influence of fabrication tolerance on antenna’s frequency response. A high-power analysis is conducted to verify the power handling capability of the antenna. The proposed design highlights the capability of 3-D printing technology in fabricating complex and highly integrated microwave devices. [ABSTRACT FROM AUTHOR]

This letter presents a novel quad-polarization-agile aperture-coupled antenna using a reconfigurable impedance converter. The designed reconfigurable converter can achieve impedance and phase changes under the control of p-i-n diodes. Based on this converter, a quad-mode switchable feeding network can be produced. Utilizing the feeding network to excite a dual-polarized aperture-coupled patch antenna, polarization reconfigurability is realized. By switching the p-i-n diodes, two orthogonal linear polarizations (LPs) and two orthogonal circular polarizations can be generated. Measurement results show that its return-loss bandwidth is wider than 2.5% at LP modes, its axial-ratio bandwidth is better than 1.8%, and its cross polarizations are below –20 dB for all the states. [ABSTRACT FROM AUTHOR]

It is difficult to effectively rectify or convert low power in the circuit stage of harvesters. The high-gain antenna can offer a higher level of power and is beneficial to RF power harvesting in a low power density environment. To extend the narrow beam of the conventional high-gain rectenna, the multiport and multibeam antenna is promising. To pursue a simple configuration and avoid extra beamforming networks, a traveling-wave grid-array antenna (GAA) with two isolated ports and two symmetrically tilted beams is proposed. A prototype is designed and fabricated after a detailed analysis of the GAA with tilted beams and the coplanar stripline-based rectifier. The measured results show that the proposed rectenna is sensitive and effective in a wide-angle range. The harvesting angle range is extended by combining two tilted beams and can be greater than 70°, where the level of dc power exceeds $100~\mu \text{W}$ when the power density is as low as $1~\mu \text{W}$ /cm2. A maximum dc output of 3.6– $203.8~\mu \text{W}$ and a maximum RF-to-dc conversion efficiency of 16.3%–45.3% are available at 2.45 GHz, under the condition that the power density ranges from 0.052 to $1~\mu \text{W}$ /cm2. [ABSTRACT FROM AUTHOR]

We present a three-dimensional (3-D) printed metallic K-band (18–26.5 GHz) passive front end for satellite communication. It is intended to be used as a unit cell in a large antenna array. The proposed front end is composed of a two-stage $1 \times 4$ power divider, rectangular-to-circular waveguide tapers, and a linear four-element conical antenna array, which are too complex to be fabricated by a traditional machining process in a whole piece. Taking advantage of the 3-D printing technology in realizing complex structures, we achieve a highly integrated passive module. A good agreement is achieved between simulation and measurement. The proposed front end has impedance bandwidth 19–21 GHz, the maximum gain of 15.5 dBi at 21 GHz, and desirable radiation patterns on both E- and H -planes. The influence of fabrication tolerance like the surface roughness and dimensional tolerance are observed and analyzed. Compared with traditionally fabricated metallic microwave passive devices, the proposed work has a shorter turnaround time and a lower cost. Compared with dielectric 3-D printed microwave devices, it features more simplicity in terms of process and better physical robustness. It opens up new possibilities for microwave device fabrication. [ABSTRACT FROM AUTHOR]

In this communication, a reconfigurable feeding network is proposed for the design of a quad-polarization-agile antenna. By switching the PIN diodes, the four transmission modes with selected phase differences can be electrically tuned at two output ports. For each mode, the measured insertion loss of the feeding network is less than 0.8 dB at the operating frequency. Because of its compact size, the proposed feeding network can be further integrated with a dual-polarized aperture-coupled antenna, which can exhibit two orthogonal linear polarizations and two orthogonal circular polarizations. Measured results of the polarization-agile antenna are shown in detail, which verify its performance. [ABSTRACT FROM AUTHOR]

An implantable rectenna, which consists of a planar inverted-F antenna (PIFA) and a rectifier circuit, is proposed for far-field wireless power transfer. The PIFA has a folded ground plane to miniaturize its size. The performance of the wireless power link between the implanted antenna and an external antenna is examined. A method of adding a parasitic patch over the human body is used to enhance the wireless power link, thus to increase the received power level. Safety considerations of far-field RF powering are discussed. The RF-to-DC conversion circuit efficiency is optimized after the receiver power level of the implantable antenna is estimated based on the safety considerations. Finally, a rectifier circuit and an integrated rectenna solution are discussed. [ABSTRACT FROM PUBLISHER]

This communication presents a 60-GHz wideband circularly polarized (CP) U-slot patch antenna array of 4\,\times\,4 elements on low temperature cofired ceramic (LTCC). A CP U-slot patch antenna is used as the array element to enhance the impedance bandwidth and a stripline sequential rotation feeding scheme is applied to achieve wide axial ratio (AR) bandwidth. Meanwhile, a grounded coplanar waveguide (GCPW) to stripline transition is designed for probe station measurement. The fabricated antenna array has a dimension of 14\,\times\,16\,\times\,1.1 mm^3. The simulated and measured impedance bandwidths, AR bandwidths, and radiation patterns are investigated and compared. Measured results show that the proposed antenna array has a wide impedance bandwidth from 50.5 GHz to 67 GHz for \vert S 11 \vert < -10~dB, and a wide AR bandwidth from 54 GHz to 65.5 GHz for AR< 3~dB. In addition, it exhibits a peak gain of 16 dBi and a beam-shaped pattern with 3-dB beam width of 20 ^\circ. Moreover, its AR keeps below 3 dB within the 3-dB beam width. [ABSTRACT FROM PUBLISHER]

This letter presents a novel adaptive rectifier for wireless power transmission (WPT) applications. By utilizing a depletion-mode field-effect transistor (FET) switch, the configuration of the rectifier can automatically adapt to the input power level. Compared with traditional rectifiers, it can provide a consistent high RF-to-dc power conversion efficiency (PCE) over a significantly extended operating input power range. Measured results show that the PCE of this proposed adaptive rectifier keeps above 50% in the input power range spanning from -14 up to 21 dBm. Additionally, maximum PCE of more than 75% is achieved in the input power range from 5 to 15 dBm. [ABSTRACT FROM PUBLISHER]