Microwave and Optical Technology Letters最新文献

An assembled antenna, based on the non-uniform compression of two wide-beamwidth quadrifilar helical antennas (QHA) with a miniaturized monopole, is proposed for submersible applications. Initially, the impact of each parameter of the QHA on the Half Power Beamwidth (HPBW) is analyzed. Subsequently, the structural parameters of the spiral arm's compression part are examined. Utilizing theoretical analysis, the structure of the QHA is established, and two QHAs with differing polarizations are combined with a miniaturized monopole antenna to enable the proposed antenna to operate in triple-mode, encompassing satellite navigation, duplex communication, emergency location, and search and rescue (SAR). Finally, the antenna is constructed and evaluated. The evaluation results indicate that the left-hand circularly polarized QHA achieves a 189° HPBW and a 208° ARBW within the B1C satellite navigation band (1575.42 ± 16.368 MHz) and a 201° HPBW and a 206° ARBW within the L satellite communication uplink band (1615.68 ± 7 MHz). The right-hand circularly polarized QHA exhibits a 202° HPBW and a 186° ARBW in the S satellite communication downlink band (2491.75 ± 15 MHz). The monopole antenna operates effectively at 406 MHz, emitting vertically polarized waves suitable for SAR.

A novel filtering power divider (FPD) with high isolation and wideband reflectionless characteristics is proposed. The wideband filtering characteristics of the FPD come from the joint contribution of the coupled lines and the stepped impedance resonator, where the coupled lines provide the passband characteristic, and the stepped impedance resonator generates and tunes the transmission zeros outside the passband to enhance out-of-band suppression and improve frequency selectivity. The absorption-isolation network and absorptive stubs improve isolation between output ports while achieving input reflectionless characteristics. Through theoretical analyses and experimental verification, a prototype microstrip line was developed, with simulation results showing good agreement with measured data. Measured results indicate that the proposed FPD—with a center frequency of 2.47 GHz—delivers excellent isolation: better than 30 dB within the passband and superior to 22 dB over the entire 0 to 7 GHz frequency range. The input reflectionless bandwidth is up to 277% from 0 to 6.87 GHz.

In this manuscript, a new wideband and high-gain filtering slotline antenna with reconfigurable notch band is presented. This work is designed based on a triple-mode and high-gain filtering slotline antenna, which is center-fed by a short-ended microstrip feedline. Then, the microstrip feedline is directly extended to form a shunt open-ended stub with varactor. Through controlling the voltage on the varactor, an independently and continuously reconfigurable notch band in the passband can be introduced. To validate the design principle, a prototype antenna is designed and fabricated. The measured results show that the notch band can continuously reconfigurable from 2.5–3.02 GHz while its bandwidth and normalized radiation patterns are unchanged.

A cooperative optimization framework with enhanced parameterized topology and current-driven dimensionality reduction approach is proposed. The expansion of the design space in both dimensionality and diversity is achieved by the enhanced parameterized topology through the introduction of Boolean and shape variables, which permit free adjustment of geometry, topology type, position, and dimension. Furthermore, rapid dimensionality reduction is achieved using a current-driven strategy, whereby the current distribution is analyzed to identify critical parameters. The ensuing multi-objective optimization challenge is addressed by a global-local cooperative surrogate-assisted multi-objective differential evolution algorithm (GLCSA-MODE). The approach is guided synergistically by global and local surrogate models to achieve rapid enhancement of antenna performance. To validate the effectiveness of the proposed method, a microstrip patch antenna is optimized, fabricated, and measured. The measured results are in good agreement with the simulations, demonstrating an impedance bandwidth of 43.21% (4.88–7.57 GHz) and a flat gain response in the passband. The results confirm the method's effectiveness in dual-objective optimization and its capability to generate unconventional antenna topologies.

This paper presents the design of an ultra-compact circularly polarized (CP) satellite antenna integrated with gradient shorting strips. By etching gradient rectangular slots on the diagonal and opposite sides of a square radiating patch, and arranging gradient shorting strips around these slots, the antenna achieves an 84.8% size reduction compared to a traditional half-wavelength air microstrip antenna, with minimized electrical dimensions of 0.195λ₀ × 0.195λ₀ × 0.027λ₀. Notably, the gradient shorting strips act as parasitic elements to effectively broaden the antenna beam. Measurement results show a 4 dB gain improvement at ±70° elevation angles relative to the conventional air microstrip antenna. The antenna exhibits a port return loss (RL) better than −10 dB over a 27.8% bandwidth (340–450 MHz) and maintains an axial ratio (AR) < 3 dB across a 25.3% bandwidth (345–445 MHz). At the center frequency (400 MHz), the main radiation gain is ~6.0 dB with a −3 dB gain bandwidth of ~4.6%.

This paper presents a digitally controlled reflective-type phase shifter (RTPS) operating from 2.1 to 2.3 GHz, achieving a full 360° phase-shift range using a single DAC. In conventional digitally controlled RTPS implementations, the achievable phase resolution is limited by the nonlinear capacitance–voltage characteristic of varactor diodes and the nonlinear relationship between phase and load reactance, resulting in uniform DAC voltage steps translating into non-uniform phase increments. To mitigate this limitation while maintaining low circuit complexity, an 8-bit uniform DAC is employed in conjunction with a phase-code mapping strategy, where selected digital control codes are used to realize approximately uniform phase steps across the tuning range. The DAC output is multiplexed between two resonating load branches, enabling full-range phase control using a single DAC and a single control line. The proposed RTPS achieves an approximately uniform phase-shift resolution of about 3° ± 1° with low and stable insertion loss over the operating band. This approach provides a practical and robust solution for high-resolution digitally controlled beamforming and phased-array systems.

A wideband millimeter-wave highly isolated dual-polarized magneto-electric (ME) dipole antenna with sandwich feeding is proposed for a 60-GHz unlicensed band. The ME dipole antenna is placed between two orthogonal feeds to form a virtual ground, which suppresses current coupling and significantly improves port isolation. The isolation performance of the proposed antenna was analyzed through comparison with two different reference structures and optimized through parameter studies. The S-parameter was assessed using a GSG probe linked to a vector network analyzer (VNA). The size of the fabricated 4 × 4 array antenna is 11 mm × 11.5 mm × 0.54 mm (2.2λ₀ × 2.3λ₀ × 0.11λ₀). The measured port isolation (S21) of the proposed ME dipole antenna was better than −30.6 dB, achieving a bandwidth of 27.8% (52.9–70 GHz) and a peak gain of 16.78 dBi. Additionally, the measured and simulated S₁₁ was < −10 dB with 32.7% bandwidth covering from 50.3 to 70 GHz.

A guided-wave EMP simulator model combined triangles and distributed resistor loads on thin-wires is proposed in the FDTD method. The principal achievement of this new application of thin wire model is to enable us to achieve progressively accurate EMP simulator model. For checking the metal junction, a new colorful cube checking method is introduced. The calculation results are verified by the measurements of the extant EMP simulator.

This study demonstrated an extensive study on the combined method of laser-induced breakdown spectroscopy (LIBS) with the microwave-assisted (MW) method. A Nd:YAG laser beam is focused on the Aluminum (Al) sample to produce plasma, while the microwave power with intensities of 0 W, 30 W, 50 W, and 70 W is applied to evaluate its contribution to plasma generation. The findings showed the aluminum emission lines were remarkably increased with an enhancement factor of 1.90, 2.37, and 2.78 times at the microwave power of 30 W, 50 W, and 70 W, respectively, as compared to the case when no microwave power was added. The plasma parameters including electron temperature (T_e) and electron density (N_e) are evaluated based on the spectroscopies approaches like Boltzmann plot and the Stark broadening method, respectively. The results showed an important increase in the values of both parameters whenever the microwave power is added to the plasma emission method. The temporal profile of both parameters showed a higher pattern relative to the case when there is no added microwave power. Moreover, the plasma decay rates showed lower decay rates whenever the MW method is employed, thereby confirming the feasibility of the MW-LIBS method to produce superior plasma performance and efficiency. These outcomes revealed the potential of MW-LIBS in practical applications, including environmental monitoring and material analysis.

This article presents 10 elements wideband multiple-input multiple-output (MIMO) antenna with novel T-shape metamaterial (MTM) for mm-wave applications. The novel T-shape MTM and radiating elements are manufactured on single layer Roger 5880 RT/Duroid substrate, the overall size of the design is 20 × 78 × 0.8 mm. The low gain in mm-wave antennas, and high mutual coupling due to arrangement of multiple antennas in close proximity are main challenges that proposed design must address. The parameters, such as gain, isolation, and reflection coefficient, are significantly improved by introducing T-shape MTM. The gain is enhanced from 5 to 18 dBi, isolation is improved from 12 to 26 dB. The impedance bandwidth is 31 GHz in the given range of 11.5–42.5 GHz. Moreover, diversity performance parameters, such as diversity gain (DG), correlation, and multiplexing efficiency, are also discussed to analyze and validate further the performance of MIMO design. Therefore, the presented MIMO antenna is suitable candidate for mm-wave applications.