A rigorous analysis of the scattering of plane and cylindrical waves from a strip loaded single near zero and double near zero (DNZ) metamaterial cylindrical object is presented. The proposed problem has been solved using integral equations derived from Green’s theorem and usual tangential boundary conditions. During the analysis, it was found that by loading a strip onto the metamaterial cylindrical objects, one can enhance or diminish the scattering under some specified conditions. It is shown that an enhancement in the back scattering occurs for a strip loaded DNZ metamaterial cylinder as compared to the back scattering of an unloaded DNZ metamaterial cylinder for both types of incident polarization. In the case of a specifically located electric line source, it is argued that by loading a strip onto a DNZ metamaterial cylinder, one can reduce the magnitude of the total field significantly at specific observation azimuth angles. For a specific location of a magnetic line source, the magnitude of total field of a strip loaded mu near zero (MNZ) metamaterial can be significantly enhanced as compared to unloaded MNZ cylinder in the specific observation directions. This parametric investigation is helpful in the designing of cylindrical metamaterial-based devices.

This paper presents a millimeter-wave end-fire dual-polarized (DP) array antenna with symmetrical radiation patterns and high isolation. The DP radiation element is formed by integrating a quasi-Yagi antenna (providing horizontal polarization) into a pyramidal horn antenna (providing vertical polarization), resulting in a DP radiation element with a symmetrical radiation aperture. To efficiently feed the DP element while maintaining high isolation, a mode-composite full-corporate-feed network is employed, comprising substrate-integrated waveguide supporting the TE10 mode and substrate-integrated coaxial line supporting the TEM mode. This design eliminates the need for additional transition structures, achieving excellent mode isolation and a reduced substrate layer number. A 1 × 4-element DP array prototype operating at 26.5–29.5 GHz using low temperature co-fired ceramic technology was designed, fabricated, and measured. The test results indicate that the prototype achieves an average gain exceeding 10 dBi for both polarizations within the operating band. Thanks to the symmetrical DP radiation element and mode-composite full-corporate-feed network, symmetrical radiation patterns for both polarizations are observed in both the horizontal and vertical planes, along with a high cross-polarization discrimination of 22 dB and polarization port isolation of 35 dB.

Reconfigurable intelligent surfaces (RISs) enhance the performance of wireless communication networks, particularly within millimeter wave (mm-Wave) bands. When a line-of-sight link is not strong enough or is fully blocked. The location of RIS has a significant impact on the RIS’s wireless channel and system performance. A wireless communication model has been proposed in a mm-Wave environment supported by RIS. The proposed model contains one transmitter and five users at the receiving end. Due to the small distance between users, there is interference between them and the received signal-to-interference-plus-noise ratio (SINR) decreases. Three RISs separated by different interspace distances were proposed to serve users at various distances from the transmitter to reduce inter-user interference. The simulation results showed that increasing the distance between the RIS site and the TX-User line served a larger number of users, and the three heights of the RIS provided a coverage range domain complementary to each other for different user sites. The improvement percentages in SINR for the second and third RIS are 48.46% and 77.38%, respectively. Enlarging the size of the RIS only increases the signal capacity and does not affect the coverage range domain of the single RIS.

Intelligent Reflecting Surface (IRS) technology operating at mm-wave frequencies is promising for 6G applications. However, this technique faces the challenge of beam splitting, as beams cannot be directed accurately at all frequencies. To enhance system performance and lessen the beam spillting effect, the IRS is developed using phase shifters and time delay modules, as the problem is analyzed in this paper. The results of the simulation revealed that the proposed system, which is based on sub-surface IRS and time delay modules, successfully overcomes the packet splitting challenge effectively. The proposed architecture was 94.5% better in gain compared with the traditional architecture. The results explained a 54% improvement in data rate when time delay is used in the Phase-shift-Time delay-Phase delay (PTDP) system compared to the conventional design. Moreover, the use of 2-bit phase shifting alone in the proposed design was appropriate to realize close to optimal performance due to the system capability to direct power in the desired direction through the use of precoding technology, which compensates for losses resulting from beam splitting.

A long-range, compact, wideband Ultra High Frequency (UHF) radio frequency identification (RFID) tag is proposed. The design features a triangular patch, designed to achieve wideband impedance matching. The tag exhibit −10 dB bandwidth from 753 to 917 MHz with a substrate thickness of 1.575 mm. The overall size of the tag is 121 × 30 × 1.575 mm3. The gain and bandwidth for varying substrate thickness is investigated. Further, two parasitic strips are designed alongside the patch to operate the tag more effectively at Federal Communications Commission (FCC) band in simultaneous with European Telecommunications Standards Institute (ETSI) band with increased read range. With parasitic strips, the tag exhibits −10 dB bandwidth from 766.5 to 896.5 MHz and 905 to 943.6 MHz which covers the bandwidth requirements in Europe, Asia, and North America. A prototype of the proposed tag is fabricated and experimentally tested with the RFID Higgs 4 IC. The tag provides a read range of over 14 m in 865–870 MHz and 13 m in 902–928 MHz when the tag is operated in free space and a read range of over 10.2 m in 865–870 MHz range and 10.3 m in 902–928 MHz range when mounted on a metallic surface of size of 200 × 200 m2 . The performance parameters of the designed tag are also compared with some commercially available designs.

This paper presents a wideband dual-polarized in-band full duplex antenna which can also suppress the higher order modes. A dual differential capacitive feeding scheme is proposed to increase the isolation between the co-located transmitter and receiver ports. The proposed design uses λ/4 resonators in close vicinity of the radiating patch to provide spurious-free characteristics. Further, a parasitic patch placed above the radiating patch at height “h” is used to enhance the input matching, impedance bandwidth, and gain of the proposed design. The key features of the proposed structure are its wide impedance bandwidth (∼20%), high inter-port isolation (>58 dB) throughout the entire operating frequency range (2.26–2.76 GHz), and simultaneous suppression of higher order modes which makes it a suitable candidate for modern wireless application. Finally, a prototype is fabricated and measurement results are in good agreement with simulation results.

This paper presents a flexible SiGe monolithic microwave integrated circuit (MMIC) chipset for 120 GHz ultra-wideband frequency-modulated continuous wave radar systems. The highly integrated chipset is implemented with multiple-input and multiple-output radar in mind which leads to transmit and receive MMICs with four integrated channels in each chip. The transmitter achieves an output power of 12.9 dBm with a total power consumption of only 403 mW. The receiver chip incorporates a sub-harmonic approach for suppression of leakage radiation at 120 GHz through a receive channel. Both chips integrate active multiplier chains that are driven by a third reference dual band voltage-controlled oscillator (VCO) MMIC that can deliver an output at center frequencies of 15 or 30 GHz. The reference VCO MMIC demonstrates relative tuning ranges of 32%.

In this paper, we propose a hybrid sparse array design utilizing Delaunay Triangulation algorithm for element positioning and Convex algorithm for element excitation optimization. This Delaunay Triangulation algorithm yields a radiation pattern devoid of grating lobes. Then Convex algorithm is used to optimize the element excitations to further decrease side-lobe-level. The minimum inter-element distance is as large as 8 times of wavelength. The peak-side-lobe-level can be −17.3 dB. Furthermore, beam steering can be achieved with good performance within 80° field-of-view range.

A type of signal-interference fourth-order dual-band bandpass filter (BPF) with multiple out-of-band transmission zeros (TZs) is reported. A second-order dual-band BPF block is firstly discussed, which is composed of two microstrip-to-slotline vertical transitions that are back-to-back connected by means of an in-parallel asymmetrical microstrip-line-based closed loop. It exhibits spectrally symmetrical passbands regarding the design frequency fD and three TZs at the inter-band region. Subsequently, by using stepped-impedance-line segments at the longest path of the transversal signal-interference closed loop, its dual-band BPF counterpart with second-order spectrally asymmetrical dual passbands is presented. Next, in order to increase the filter order as well as the number of out-of-band TZs for augmented stopband attenuation, a fourth-order dual-band BPF circuit is conceived. To this aim, two Y-shaped stepped-impedance microstrip stubs are loaded at the input and output ports of the previously devised second-order frequency-symmetrical dual-band BPF block. The RF operational principles of all these dual-band BPFs are detailed through their associated transmission-line-based equivalent circuits. Moreover, for experimental-demonstration purposes, a 1.154-/2.818-GHz two-layer microstrip proof-of-concept prototype of a fourth-order sharp-rejection dual-band BPF is designed, simulated, and characterized. It features inter-band power-rejection levels higher than 28.68 dB and lower-/upper-stopband attenuation levels above 40.92 dB from DC to 4.64 GHz.

In this paper, a large, compact array antenna that can be expanded in the 2-D plane is proposed for near-field radio frequency identification applications. By the introduction of the fractal structure and corner joint method, the array is easy to expand in the 2-D plane. An antenna element can be divided into a dozen or so loops, and traveling wave distribution makes sure that every loop is excited in a time period. So that a strong and uniform magnetic field could be generated in a large area. As a proof of concept, array antennas with $1 \times 8$, $2 \times 4$, and $3 \times 3$ elements are designed, fabricated, and measured. The measured bandwidth of the antennas covers the entire Chinese standard. Reading distances of the proposed large array antennas achieved up to 57 mm. Results show that the proposed antenna could realize flexibility and extendibility in a large area with stable and uniform magnetic field distribution.

This manuscript presents a millimeter-wave GaN high-power amplifier (HPA) intended for next generation inter-satellite links (ISLs). The proposed architecture achieves a fractional bandwidth wider than 18% in the V-band spectrum, to deliver a 10 Gbit/s throughput compatible with multi-thousand-km ISLs. Core of the HPA is the monolithic microwave integrated circuits (MMIC ) power amplifier which covers the whole 59–71 GHz band with high efficiency through innovative topologies and a cutting-edge gallium nitride on silicon carbide (GaN-on-SiC) process. The MMIC is then parallelized by means of a 1-to-8 splitter/combiner to obtain a V-band 10 W GaN HPA. Measurement results show a peak small-signal gain of 25.6 dB, 6.5% peak power-added efficiency, and a maximum P1dB of 40.3 dBm.

In this article, a qualitative work has been carried out based on airborne pulsed Doppler (PD) RF sensor consist of its operational requirements in terms of phase noise modeling and associated contributing factors. Precise and efficient theoretical modeling of phase noise requirement for airborne-PD radar or long-range RF sensor is presented. This work also emphasis on the limitation of conventional phase noise modeling practices used for PD RF sensor. An improved equation has been derived for accurate phase noise estimation considering the range correlation effect and inline flicker contribution on residual phase noise requirement. Random vibrations causes increase in phase noise level around low frequency offsets region in local oscillator. The proposed phase noise model is efficient enough to counter phase noise degradation at lower frequency offsets. The proposed model is also experimentally validated. Improved modeling offers benefit in reducing the stringent RF sensor phase noise specifications at close-in frequency offsets using range correlation effect and precise inclusion of inline flicker contribution. Present work can be used to mitigate random vibration effects at close-in phase noise offsets, which avoids complex stabilization practices and stringent oscillator design phase noise specification.

Antenna arrays are a main driver of next generation millimeter-wave communication and radar systems as shrinking antenna sizes leverage larger arrays to compensate for reduced link budget. However, conventional phase controlled arrays exhibit a frequency dependent scan angle that appears as loss to a fixed counterpart. Bandwidth limitations introduced by the so-called beam squint effect hinder larger array sizes and data rates thereby generating a demand for timed arrays as a solution. This paper gives a quantified overview of the beam squint phenomenon, different hardware architectures as well as evaluation parameters and common shortcomings of true-time delay (TTD) elements. A broad variety of TTD realizations from literature are compared by their operational principles and performance. Finally, the delay interpolation principle, its non-idealities, and their impact on a hierarchically time delay controlled D-band antenna array are described. Extended content on a previously published, continuously tunable TTD implementation at a center frequency of 144 GHz with a bandwidth of 26 GHz and a delay range of 1.75 ps that requires only 0.53 × 0.3 mm2 of core chip area is presented. Measurement results have been obtained from a demonstrator manufactured in 130 nm BiCMOS technology.

In this work, a compact active integrated antenna based on a highly compatible antenna-in-package (AiP) solution is proposed. It consists of two sections, namely, a cover plate integrated with an antenna and a package backplane that carries a GaN power amplifier (PA) die. The proposed AiP solution not only provides efficient interconnection between the antenna and the GaN PA die while providing physical shielding, but also provides impedance compensation for the die to improve the matching performance. Besides, a plated through hole array is designed inside the package backplane to significantly improve heat dissipation performance. The proposed AiP solution is compatible with radio frequency integrated circuit (RFIC) dies with different pin arrangements. Two prototypes are fabricated and measured for validation. The first prototype is the active integrated antenna based on the GaN PA, which shows an impedance bandwidth of 25.7–28.7 GHz, a peak gain of 31 dBi, and a dimension of 8 mm × 8 mm × 1.7 mm. Another prototype is based on a GaN front-end module (FEM) die integrating the PA and low noise amplifier, which demonstrates better EVM and ACPR than the conventional design with separate antenna and FEM.

This paper presents a novel design of quad-band rat-race couplers (RRCs) based on a modified T-shaped structure (MTSS). Two coupled lines are incorporated into the conventional dual-band T-shaped structure to create the MTSS, making it equivalent to a quarter-wavelength transmission line at four operating bands. The ABCD matrix method is applied to analyze the quad-band MTSS, deriving closed-form equations for calculating parameters of the structure. Then, a conventional RRC is separated into quarter-wavelength transmission lines, which are replaced by the proposed MTSS. To validate the design method, a quad-band RRC operating at 0.6, 1.196, 1.853, and 2.45 GHz is designed, fabricated, and tested. Simulation and experimental results demonstrate excellent agreement with theoretical prediction. The measured results show that input return loss exceeds 21.75 dB, isolation is greater than 21.6 dB, and insertion loss is less than 4.4 dB at all four operating frequencies. Phase deviations observed from the measured in-phase and out-phase responses are within 0o ± 4.6o and 180o ± 6.7o, respectively. Compared to most previously reported quad-band RRCs, the proposed circuit features a simple design and offers superior performance in isolation, return loss, and insertion loss.

This paper presents a vertically folded gap waveguide filter for use as the filter element for each antenna in an array of slotted waveguide antennas, at W-band. Loaded gap-waveguide resonators are used to reduce the footprint of the filter, and the filter is vertically folded to reduce the length. New input and output transitions are proposed, as well as inter-resonator coupling structures that conform to the basic gap-waveguide structure. A 7th order filter with a bandwidth of 10 GHz and a center frequency of 101 GHz is designed to meet geometric constraints of a transmitter system. A sensitivity analysis was performed on the structure to determine the required manufacturing tolerances. The filter was manufactured and measured yielding 10 dB of return loss in the passband and a detuning of the passband by 1 GHz. The return loss at 88 GHz peaked due to deviations in manufactured gap height in the gap waveguide. Deviations from the simulated response were accounted for with a parameter extraction from the measured results.

This work describes the design process of a single-pole double-throw (SPDT) microwave switch operating at Ka-band. It is tailored to a tunable reflective termination design that can be used in tunable power amplifier configurations. A high electron mobility transistor and a resonating network are employed in shunt configuration to enhance the performance in the output port’s active and inactive conditions. The small and large signal measurements showcase a 2 GHz bandwidth with an insertion loss and isolation better than −1.8 dB and −25 dB, respectively, and handling power levels of up to 3 W at 30.5 GHz. The load-pull measurements across the entire Smith chart offer comprehensive insights into the behavior of the SPDT when operating with complex and reactive loads, fulfilling the purpose of tunable reactive termination.

A reconfigurable leaky-wave antenna and its application capable of electronically steering the beam within the entire hemisphere is presented. The original antenna is designed as a 1D array of conducting patches on a dielectric substrate coupled by varactors in series with interdigital capacitors. The beam of this antenna is driven by a DC bias that controls the capacitances of the varactor diodes over a frequency range from 8 to 8.2 GHz. Simulations showed a change in the direction of the main radiation pattern within 55° at 8 GHz by varying the varactor capacitances in the range of 0.1 to 1 pF. The maximum gain is 10 dBi and the side lobe level is -10 dB. The fabricated antenna sample operates at an applied DC voltage between 0 and 12 V, which corresponds to varactor capacitances controlled in the range of 1 to 0.15 pF. This gives a range of elevation angles equal to 40°. The application of the antenna in a reconfigurable star-type structure is proposed. The direction of the main lobe of the radiation pattern in azimuth is controlled by switching between the centrally excited eight antenna arrays using PIN diodes. The direction of radiation in elevation is controlled by the DC bias of the varactors of a particular array switched to “ON”. This complex beam steering throughout the hemisphere represents a novel character of the presented antenna. The antenna has a planar structure. Low-cost printed circuit board technology was used for its fabrication.

The study introduces a novel dual-reflector antenna featuring a modified sub-reflector design aimed at improving aperture efficiency. A cylindrical-shaped keeper is introduced to enhance the performance of the sub-reflector. The dual-reflector configuration comprises a main parabolic reflector and a modified sub-reflector, with diameters of 16.5 λ and 2.2 λ, respectively, operating at 5.5 GHz. The antenna demonstrates a bandwidth (BW) of approximately 25.4% (4800–6200 MHz). Experimental measurements indicate favorable characteristics, including low cross-polarization levels (<−25 dB), minimal back lobe levels (F/B > 30 dB), high isolation between ports (>38 dB), and VSWRs less than 1.5:1 for both port1 and port2. The antenna exhibits an efficiency of around 58% and achieves a measured peak gain of approximately 32 dBi within the operating BW.