Search Results (69)

This paper presents the design of a wideband circularly polarized crossed-dipole antenna for multi-GNSS applications, covering the frequency range of 1.16–1.61 GHz. The proposed antenna employs orthogonally placed dipole elements fed by a three-branch quadrature hybrid coupler for broadband and wide gain/axial ratio beamwidth. The design is carried out using CST Studio Suite for a single dipole antenna followed by a crossed-dipole antenna, a feed network, and the entire antenna structure. The designed multi-GNSS antenna shows, at 1.16–1.61 GHz, a reflection coefficient of less than −17 dB, a zenith gain of 3.9–5.8 dBic, a horizontal gain of −3.3 to −0.2 dBic, a zenith axial ratio of 0.6–1.0 dB, and horizontal axial ratio of 0.4–5.9 dB. The proposed antenna has a dimension of 0.48 × 0.48 × 0.25 λ at the center frequency of 1.39 GHz. The proposed antenna can also operate as an LHCP antenna for L-band satellite phone communication at 1.525–1.661 GHz. Full article

Wireless power transfer systems require not only strong coupling capabilities but also stable output under various misalignment conditions. This paper proposes a hybrid magnetic coupler for autonomous underwater vehicles (AUVs), featuring two identical arc-shaped rectangular transmitting coils and a combination of an arc-shaped rectangular receiving coil and two anti-series connected solenoid coils. The arc-shaped rectangular receiving coil captures the magnetic flux generated by the transmitting coil, which is directed toward the center, while the solenoid coils capture the axial magnetic flux generated by the transmitting coil. The parameters of the proposed magnetic coupler have been optimized to enhance the coupling coefficient and improve the system’s tolerance to misalignments. To verify the feasibility of the proposed magnetic coupler, a 300 W prototype with LCC-S compensation topology is built. Within a 360° rotational misalignment range, the system’s output power maintains around 300 W, with a stable power transmission efficiency of over 92.14%. When axial misalignment of 40 mm occurs, the minimum output power is 282.8 W, and the minimum power transmission efficiency is 91.6%. Full article

The quarter-wave transformer is a useful circuit for impedance matching. In this paper, we use three equal-length transmission lines to design dual-band quarter-wave transformers. Closed-form design equations are derived. The proposed structure is found to be suitable for dual-band operation with a frequency ratio greater than 5. Numerous microwave passive components are composed of quarter-wave transformers. For these components consisting of quarter-wave transformers, the use of dual-band quarter-wave transformers can inherently result in dual-band operation. The proposed structure is, therefore, a simple and effective element for designing dual-band microwave passive components with a frequency ratio greater than 5. Because the existing techniques for designing dual-band circuits are mostly suitable for frequency ratios lower than 5, the proposed structure, therefore, complements the existing techniques. To demonstrate the applicability of the structure, two directional couplers, namely, a dual-band branch-line hybrid and a dual-band rat-race hybrid, are designed and fabricated on a RO4003C substrate. Measurement results validate the applicability of the proposed structure. Full article

This study explores the impact of graphene integration on lithium niobate (LiNbO₃, LN) ridge waveguides and directional couplers, focusing on coupling efficiency, polarization-dependent light absorption, and temperature sensitivity. Experimental and simulation results reveal that graphene loading significantly alters the effective mode refractive index and enhances waveguide coupling, enabling precise control over light transmission and power distribution. The temperature-dependent behavior of graphene–LN structures demonstrates strong thermal sensitivity, with notable changes in output power ratios between cross and through ports under varying temperatures. These findings highlight the potential of graphene–LN hybrid devices for compact, high-performance photonic circuits and temperature sensing applications. This study provides valuable insights into the design of advanced integrated photonic systems, paving the way for innovations in optical communication, sensing, and quantum technologies. Full article

This paper presents our research on an E-band Radio Frequency (RF) front-end packaging structure based on back-to-back gap waveguide (GW). This design effectively mitigates the impact of air gaps on performance and offers the advantage of large assembly tolerances. Additionally, its back-to-back structure enables structural stacking, which can reduce the overall packaging size. In terms of functionality, the structure integrates hybrid couplers, bandpass filters, and amplifier packaging structures. Notably, the hybrid couplers provide high port isolation, facilitating a higher isolation duplex function by simply connecting high-order bandpass filters at the output ports without the need for additional optimization. Furthermore, these couplers also serve as power dividers/combiners. When combined with the H-plane amplifier packaging structures, the output power of the module is theoretically increased by 3 dB. Based on the measurements, the results indicate that this structure operates within the frequency ranges of 71–76 GHz and 81–86 GHz. The common port return loss is below 12 dB, while the in-band insertion loss is less than 2.26 dB and 2.42 dB, respectively. These findings demonstrate excellent electrical performance and suitability for E-band communication systems. Full article

A 90° optical hybrid employing an MMI coupler was fabricated on a thin-film lithium niobate (TFLN) platform that can be used for integrated coherent transceivers. The fabricated 90° optical hybrid exhibited a CMRR greater than 20 dB, a phase error below ±7.5°, and an excess loss less than 1.8 dB (including contributions from the 90° hybrid, a 1 × 2 MMI coupler, and an optical delay line, after subtracting the losses from the coupler and delay line, the 90° optical hybrid introduced less than 0.9 dB of loss) over the C-band with a compact footprint of 13.8 × 250 μm², facilitating the future development of high-bandwidth optical coherent transceivers heterogeneously integrated on TFLN. Full article

This paper presents a differential phase coupler design methodology in the IPD process. The coupler consists of a balun and two phase-shifter circuits. The compact balun was designed with lumped components and a common inductor. Each output of the balun circuit was connected to a phase shifter with an opposite phase to make a desired output phase. In the design example, a three-port 90-degree hybrid coupler was implemented on the IPD process to operate at the 6 GHz WIFI frequency. The post-simulation showed that all reflection coefficients were below −19 dB, with an insertion loss of 1.76 dB and isolation of 20 dB. The core chip size was only 0.02λ₀ × 0.018λ₀. Full article

This paper presents a circularly polarized (CP) microstrip antenna with dual circular polarization that is fed using a 3 dB 90° hybrid coupler to ensure dual-CP radiation. The proximity-coupled structure is used as a feeding technique to obtain a larger operational bandwidth that covers the standard LTE 43 of the 5G mid-band applications (3.6–3.8 GHz). The antenna was fabricated on an FR4 dielectric substrate with overall dimensions of 66.1 × 35 × 1.6 ${\mathrm{m}\mathrm{m}}^3$. A circular patch was formed as a radiating element, with four identical slits that were etched on the patch to guarantee the presence of CP radiation at the required mid-band of the 5G frequency range. The measured impedance bandwidth (BW) of this antenna was 10.6% (3.46–3.85 GHz), while the 3 dB axial ratio bandwidth (ARBW) was 8.2% along the range (3.50–3.80 GHz). The measured average gain was about 1.3 dBi along the antenna impedance bandwidth. Full article

We propose and demonstrate a microwave photonic system to generate multiband and multi-format microwave waveforms based on an actively mode-locked optoelectronic oscillator (AML-OEO) using a dual-polarization dual-drive Mach–Zehnder modulator (DPol-DDMZM). In the proposed system, the upper DDMZM is injected by two baseband single-chirped signals, and the lower DDMZM is biased to realize single-sideband (SSB) modulation using a 90° hybrid coupler. The lower DDMZM is also used to construct an AML-OEO loop, which outputs microwave frequency comb signals. By setting the phase difference in the applied two single-chirped signals, multiband up-, down-, and dual-chirped microwave signals are successfully generated. Furthermore, the tunability of the system can be realized by adjusting the frequency and power of the injection signal in the AML-OEO loop, the passband of the electrical filter, and the chirp rate of the single-chirped signal. The proposed scheme is theoretically analyzed and experimentally verified. Full article

In an underground inductive power transfer (IPT), it is inevitable to produce the phenomenon of misalignment between the transmitter and the receiver, which will reduce the output current, voltage and output efficiency of the whole IPT system. Aiming to solve this problem, a universal hybrid coupler is proposed, which can still stabilize the output in the expected range and has the ability of anti-misalignment when the X and Z directions are misaligned. The coupler is composed of a BP coupler and $\Gamma$ type network. The secondary edge of the coupler introduces a $\Gamma$ network, which decouples the two main coils on the same side of the receiver from the auxiliary coil and reduces the complexity of the system. The coupler can effectively reduce the coupling fluctuation caused by physical movement between the downhole transmitting end and the receiving end, thereby ensuring the stable output of the coupler. As a widely used IPT system, it can access the rest of the circuit topology whose output is independent of the load and achieve misalignment-tolerant output. Finally, based on the proposed hybrid IPT coupler theory, a 500 W misalignment-tolerant coupler prototype was built, and the compensation topologies were configured as series–series (SS) and series/inductance/capacitance/capacitor (S/LCC) structures. When the X and Z direction is misaligned, the constant current and voltage independent of the load can be output by switching the compensation topology. The experimental results are the same as the theoretical analysis. Full article

A silicon photonics-based optical phased array (OPA) is promising for realizing solid-state and miniature beam steering. In our work, a 1 × 16 silicon optical phased array (OPA) hybrid integrated with a III–V laser is proposed and demonstrated. The III–V laser chip is vertically coupled with a silicon OPA chip based on a chirped grating coupler with a large bandwidth. The coupling efficiency reaches up to 90% through utilizing the metal reflector underneath the silicon oxide layer. The one-dimensional antenna array comprising silicon waveguides with half-wavelength spacing enables beam steering with none high-order grating lobes in a 180° field of view. The measured beam steering angle of the hybrid integrated OPA chip is ±25°, without grating lobes, and the suppression ratio of the side-lobes is larger than 9.8 dB with phase calibration. Full article

Butler Matrix networks are well established as beamforming networks for phased antenna arrays. The challenge we address in this work is to cover the entire (advanced 5G or 6G) FR3 band (7–24 GHz) with a single network, while retaining low losses and minimal size. The employed multilayer topology is also well established; however, the matching between the utilized hybrid couplers and the phase shifters constitutes a major challenge for such a wideband operation. This is achieved herein by employing meander lines with appropriate curvature and introducing two distinct design methods for the Butler Matrix. The first method focuses on designing individual components separately, followed by their integration into the overall Butler Matrix structure. This approach is demonstrated through the design, prototyping, measurements, and validation of an 8 × 8 Butler Matrix beamformer, which operates across the 6–16 GHz band (FR3 Low). The second method introduces a wideband-matching technique which simplifies the implementation process by designing the Butler Matrix as a single, unified structure. This technique is applied to both 4 × 4 and 8 × 8 Butler Matrices, which are implemented and simulated for the low FR3 band. Both design methods result in wideband operation and compact size and meet the desired performance criteria. Full article

This paper describes the design of a hybrid coupler with a continuously variable output phase difference. This is achieved by using reconfigurable transmission lines with electrically tunable lengths controlled by two biasing voltages through varactor diodes placed across the coupler branches. The design of the coupler is based on the quadrature hybrid structure for the case where the output phase difference is 90° and on the asymmetric structure for the other cases. The proposed coupler can achieve a tunable output phase difference from 52° to 128°, while keeping a coupling coefficient of −3 dB (± 0.5 dB) over the entire desired frequency band. To validate the simulated results, a prototype working at 3.5 GHz was fabricated and tested. The measurement results show good correspondence with the simulation results, especially when the output phase difference is 90°, while a phase mismatch of less than 7° was observed for the other cases. The presented coupler would be a great asset for antenna feeding arrays, especially the Butler matrix. Full article

In this paper, a 3 dB 90-degree hybrid coupler with size reduction and harmonics rejection was designed. In the proposed coupler structure, four simple low-pass filters (LPFs) were applied. An artificial neural network (ANN) was used to determine the dimensions of the applied LPFs based on EM simulation data. The applied ANN model could also provide the desired LPF parameters, including the cut-off frequency (fc), bandwidth (BW), and insertion loss (IL). Designing an applied LPF involves complex mathematical calculations and simulations to optimize parameters. However, by utilizing neural networks, the design process can be significantly streamlined and automated. Neural networks have the ability to learn complex patterns and relationships within data, making them well suited for optimizing the performance of applied components. The proposed 90-degree hybrid coupler works correctly at 1800 MHz and has a small size of 16.6 mm × 15.15 mm, which provides a 73% size reduction compared to a normal 1800 MHz coupler. The designed coupler not only decreases the circuit size but also provides a wide rejection band from 4.8 GHz to 11.2 GHz, which suppresses the second to sixth harmonics. The insertion loss parameter of this 90-degree hybrid coupler is less than 0.1 dB at the working frequency, which shows the superior performance of the proposed coupler. Full article

We designed a narrow-linewidth external-cavity hybrid laser leveraging a silicon-on-insulator triple Euler gradient resonant ring. The laser’s outer cavity incorporates a compact, high-Q resonant ring with low loss. The straight waveguide part of the resonant ring adopts a width of 1.6 μm to ensure low loss transmission. The curved section is designed as an Euler gradient curved waveguide, which is beneficial for low loss and stable single-mode transmission. The design features an effective bending radius of only 26.35 μm, which significantly improves the compactness of the resonant ring and, in turn, reduces the overall footprint of the outer cavity chip. To bolster the laser power and cater to the varying shapes of semiconductor optical amplifier (SOA) spots, we designed a multi-tip edge coupler. Theoretical analysis indicates that this edge coupler can achieve an optical coupling efficiency of 85%. It also reveals that the edge coupler provides 3 dB vertical and horizontal alignment tolerances of 0.76 μm and 2.4 μm, respectively, for a spot with a beam waist radius of 1.98 μm × 0.99 μm. The outer cavity, designed with an Euler gradient micro-ring, can achieve a side-mode suppression ratio (SMSR) of 30 dB within a tuning range of 100 nm, with a round-trip loss of the entire cavity at 1.12 dB, and an expected theoretical laser linewidth of 300 Hz. Full article