A procedure to design and optimize triaxial horn antennas is presented. Under Matlab control, a powerful body-of-revolution code is used to analyze the simultaneous performance of tri-band horns. A simultaneous S/X/Ka triaxial horn is designed as an example.
An 82 to 98 GHz medium power amplifier is presented in a commercially available 0.1 µm GaAs process. The amplifier achieves greater than 20 dB gain and a measured Psat above 20 dBm across the frequency range. The maximum Psat of 22 dBm is measured at 96 GHz, corresponding to a power density of 395 mW/mm. A peak PAE of 13.3% is measured at 96 GHz.
Multi-beam gradient-index (GRIN) lenses are investigated to enable high aperture efficiencies and 2-D wide angular coverages. Metasurface composed of engineered elements with varied refractive indices is employed to implement the lens. Innovative methodologies are developed to calculate refractive-index distributions on the lens as well as the corresponding feed positions for multiple beams. A three-metal-layer element is developed to enable the variation of effective refractive index. Microstrip patch array antennas are designed as feed sources. Thirteen feed arrays are arranged on two focal arcs in xoz and yoz planes. A GRIN lens prototype is constructed, radiating multiple beams in a wide range of ±45° in two orthogonal planes with low scanning losses. The peak realized gain is 21.8 dBi with an aperture efficiency of 62.8%. The operating bandwidth is 22.2% from 12 GHz to 15 GHz.
In this paper, an electromagnetically transparent dipole working at the low-band (LB, 1.7-2.5 GHz) is proposed to simultaneously suppress the cross-band scattering and coupling to the high-band (HB, 4.4-5.0 GHz) antenna in a dual-band array. Dual-functional patches with vias are loaded on radiating arms of the LB dipole, which can introduce reversed induced-currents at the HB to restore the deteriorated HB radiation patterns and improve cross-band isolations at the HB. After the loading, HB patterns are well recovered, showing great consistency with the patterns of the HB dipoles operating alone. The transmission coefficients between the LB and HB ports are also greatly reduced.
In this paper, modulated metasurface based multibeam antenna is presented. The impedance superposition method of all impedance modulations for different beams is utilized in the design. The current reported multi-beam modulated metasurface has a very small number of beams due to the mutual interference of different impedance modulations. It is found that the source locations for each beam play a key role in interference suppression. Instead of using the time consuming full-wave simulation-based optimization, in this paper, the optimal source locations are obtained by using the aperture fields calculated from the zeroth-order approximation of the currents on the metasurface. A five-beam modulated metasurface antenna has been designed, providing an angular coverage up to ±30°. The peak realized gain for the broadside beam is 21.3 dBi at 14.30 GHz.
This paper examines the effect of a halfspace on the residues of the extracted resonant modes of an obliquely-oriented conductive wire target above it. Previous studies have focused on the case where the target is in free space, but in this case, the halfspace interacts electromagnetically with the target and alters the residue. The results show that the residue of the fundamental mode is affected by the dielectric properties of the halfspace, while the residues of higher-order modes remain similar as the properties change. These findings provide insights for designing automated recognition solutions for targets above halfspaces.
A frequency-reconfigurable wearable textile antenna with compact size working in the UHF band for RFID applications is presented. The antenna achieves a wide frequency tuning range of 27.6% extending from 0.783 to 1.034 GHz aiming to cover the 0.923 GHz Industrial Scientific and Medical (ISM) radio bands. The proposed antenna is manufactured and experimentally characterized to validate the design concept.
This paper presents a full ground-backed antenna configuration consisting of a core radiating patch located on top of the substrate and additionally quad-elements placed perpendicularly on the substrate.This assembly is intended to consolidate in an autonomous vehicle's shark fin aerial.By adjusting the dimensions of quad-elements, autonomy in tuning can be achieved.The quad-elements are optimized to tune in the Global Positioning System (GPS) L1 and L2 operational bands.
The time-domain performance of a wearable UWB antenna under bending is presented in this paper. The system fidelity factor (SFF) is evaluated for a case where a cylindrical bending radius of 50 mm is applied to both the transmitting and receiving antennas at a distance of 380 mm. The antenna demonstrates to maintain relatively high SFF with an average value of 81% and 76% under H-plane and E-plane bending, respectively. It exhibits a promising pulse-preserving capability suitable for UWB pulse transmission. The comparative evaluation indicates that the SFF slightly decreases under bending for directional UWB antennas.
This paper reviews and highlights the potential of near-field metallic metasurfaces (MMs) in developing high-performance antenna systems. The proposed MMs are realized based on near-field phase translation and successfully employed to enhance the gain and steer the beam in a large 3D conical space. The dielectric-free, low-cost, and lightweight attributes of MMs can be leveraged for usage in strict operating conditions.
The design of a broadband driver amplifier between 40-60 GHz is presented in this paper. The amplifier is implemented in 0.1 µm gallium arsenide process from Win Semiconductors. The amplifier achieves a measured gain of 15.5 dB at a nominal bias. The measured gain flatness is within 1 dB between 40-60 GHz. The simulated output power is greater than 16 dBm across most of the band. This driver amplifier is suitable to drive the local oscillator signal of a W-band sub-harmonic mixer.
Obtaining end-fire patterns is a serious challenge to antenna design in wearable applications, especially for unobtrusive antenna configurations integrated in clothing accessories such as buttons. Herein we propose a button antenna to serve Wireless Body Area Networks (WBAN) and apply the principle of Huygens source to produce the desired end-fire patterns. To this end, the antenna ground plane is exploited to construct a magnetic current loop which is a radiation component of the realized Huygens source. Experimental validation of a prototype suggests that this button antenna is capable of partially covering the Unlicensed National Information Infrastructure (U-NII) band. Moreover, a good agreement between pattern simulation and measurement validates the expected quasi-end-fire patterns in free-space and in on-phantom scenarios.
As an efficient and fast way to solve inverse electromagnetic problems, a deep learning algorithm for microwave imaging of complex objects is proposed. It solves the scattered wide-band time domain signals using a cascaded structure of convolutional and U-net neural networks. The algorithm is trained and tested using 2000 sets of data covering the band 0.5-2 GHz generated from an imaging domain that includes complex shaped targets irradiated by 16 antennas. Mean values of Intersection over Union (IoU) are near 0.7 for all the tested cases, while 1.0 represents a perfect overlap between the reconstructed image and ground truth, and a value above 0.5 shows a satisfying shape reconstruction (i.e., more than half of the reconstructed image overlaps with the ground truth). More than 80% of tested cases have less than 50% relative errors compared to the ground truth. These results show great potential for the developed algorithm in localization, shape reconstruction, and classification of complex objects in microwave imaging.
A low-profile dual-polarized patch antenna is proposed for millimeter-wave (mmWave) applications. Characteristic mode analysis (CMA) was used to reveal two orthogonal modes that excited the driving patch and the 2×2 patch array. In the proposed antenna, the coupling between the top 2×2 radiator and the middle driving patch can be regulated by through-holes, enabling the mmWave dual-polarized patch antenna to obtain suitable operating bandwidth with a low profile. The proposed antenna with an overall size of 0.34λ 0 ×0.34λ 0 ×0.05λ 0 operates from 24.1 GHz to 29.7 GHz(-10dB). The simulation shows that the isolation is better than 21 dB, and the peak gain is 6.9 dBi.
A differential phase shifter pair which is able to supply full 360° phase difference between two output ports is demonstrated. Thanks to the differential pair configuration, the phase shifter element requires much less phase dynamic range compared to conventional phase shifters. The basic phase-tuning unit contains a 50 Ω host microstrip line, with three identical shorted-stub-loaded varactors and two open-ended stubs on its edge. The phase shifter pair is able to produce full 360° phase difference continuously with a maximum insertion loss of 2.3 dB at 5 GHz and 2.5 dB between 4.75 and 5.25 GHz. The good agreement between simulation and measurement suggests that the differential phase shifter pair is promising and practical for microwave and antenna applications.
Broadband filters are critical for wide communication capacity but have footprint and fabrication limitations. We present a broadband filter based on cascaded effective-medium-cladded all-silicon Bragg gratings, which has a compact size of 17 mm × 3.9 mm × 0.25 mm. The proposed design leads to a stopband covering the whole IEEE terahertz wireless communications band from 252–325 GHz with an average rejection level of 20 dB, and a passband from 220–252 GHz with the insertion loss less than -3 dB. Attributed to the introduction of a longitudinal effective-medium slot in the middle of the host waveguide, the filtering bandwidth and rejection level is significantly increased, leading to a decrease in the filter footprint and an additional degree of design flexibility compared to conventional Bragg grating filters. Such a broadband filter can be used in terahertz communication systems, terahertz sensors and other emerging terahertz technologies.
This paper explains the method to reduce the signal coupling between two overlapped RF paths by applying phase cancellation. When two RF paths cross over each other, how the signal transmits in the decoupling circuit is described, and the phase variation of the E-field vectors at different stages is presented with relevant amplitudes. For demonstration, a prototype in K-band is constructed based on rectangular waveguides, and fabrication is conducted by using additive manufacturing and electroplating technologies. The measurement is consistent with the simulation.
We present a study of the absorption of sepia melanin (squid ink) in the 1.0 THz to 16 THz region. Data for the dielectric properties of biological materials, including melanin, for this region are sparse in literature. The sepia melanin ink reflectance data show a significant decrease in the reflectance at all frequencies when compared to water in the 1.0 THz to 16.0 THz region, with a 40% reduction in the 1.5 THz to 6.0 THz region, and a further reduction in the 6.0 THz to 12 THz region. The results strongly suggest that melanin remains a strong absorber in the region between the well documented sub 1.0 THz and the far IR region.
There is an increasing demand for the gallium nitride-based power amplifiers for different applications. A current controlling circuit integrated with the power amplifier on the same chip is proposed in this paper, for the purpose of monitoring the reliable operation of the power amplifier. The designed broadband differential amplifier, which is the important building block of the controlling circuit, has a gain of 43 dB and a bandwidth up to 0.1 GHz. The amplifier is operated from a ± 28 V supply which results in a higher peak-to-peak swing than a CMOS based design.
Satellite communication typically requires the use of circular polarization (CP) for effective signal propagation and robust reception, particularly for SATCOM on the move. The dual sense, or left- (LHCP) and right-handedness (RHCP), of this polarization technique means a satellite system requires prior knowledge of the transmitted signal polarization sense to avoid link degradation due to polarization mismatch. Without this prior knowledge, the system requires polarization agility. This paper proposes polarization agility from a compact single patch design.
