International Journal of RF and Microwave Computer-Aided Engineering最新文献

This paper proposes a compact and high-gain filtenna array based on substrate-integrated waveguide (SIW) technology for the W-band (75–110 GHz) high-speed wireless communication systems and imaging/detection systems. By utilizing the high integration of SIW technology, the SIW filter, butterfly slot antenna array, and patch antenna array are vertically integrated to form a filtenna array. Due to the vertical integration of two antenna arrays, the filtenna array achieves a smaller footprint. The use of butterfly-shaped slot antennas increases the bandwidth of the antenna. The butterfly slot antenna array and patch antenna array each have five units. After fabrication and testing, the filtenna array achieves high gain as well as filtering function, reducing the size of the overall circuit. The filtenna array has a center frequency of 95 GHz, a bandwidth of 3 GHz, and a maximum gain of 12.95 dB.

A data transmission system is designed for the SDGSAT-1 small satellite to meet the high-speed data processing and transmission requirements. The data transmission system consists of two principal components: the transmitter and the steerable transmission antenna. To satisfy the satellite link budget requirement, the 37.5 dBm X-band transmitter has been developed for an 810 Mbps data rate with 8PSK modulation. The dual circularly polarized antenna with a pointing mechanism has a gain of over 20 dBi, and the pointing accuracy error is less than 0.110°. The data transmission system’s EIRP exceeds 28 dBW. On-orbit operations have demonstrated that the data transmission system exhibits excellent performance and high reliability.

This paper presents a multifunctional wearable antenna that operates in multiple frequency bands, including 2.4, 4.5, 5.8, and 6.4 GHz. The proposed antenna structure is designed for both industrial scientific medical (ISM) and wireless body area network (BAN) frequency bands. The antenna employs metamaterial (MTM) unit cells to enable modes with different radiation patterns, implementing monopole-like (null at broadside) and patch-like patterns for on- and off-body communications. The maximum gain achieved is 7.6 dB at 4.5 GHz, and the antenna also provides circular polarization in the off-body frequency (5.8 GHz) with a minimum 1.13 dB axial ratio (AR). The structure is fed by a microstrip feedline for user convenience, and a full-ground plane is included to protect the human body from backward radiation. To validate the advantages of the proposed design, the antenna was fabricated, and its parameters were measured. The results showed good agreement between simulation and measurement. The effect of antenna bending was also investigated, and the results indicated that the antenna operates acceptably for bending radii up to 60 mm. Additionally, the specific absorption rate (SAR) was investigated, and low values below the standard rates were confirmed.

The fusion of deep learning techniques with conventional methods has garnered significant attention within the field of electromagnetic inverse scattering. The utilization of a traditional noniterative method for acquiring a presolution, followed by an enhancement procedure via neural networks, presents notable benefits such as simplicity and fast computational speed. However, the accuracy of this approach is usually impacted by the precision of the presolution, especially for strong scatterers. To alleviate this limitation, this research introduces a novel learning-based variational backpropagation method (VBPM). Through the utilization of variational operations, the proposed method refines the initial induced current obtained by the backpropagation (BP) method. Subsequently, an appropriate neural network is constructed to establish the relationship between the refined presolution and the true solution. Compared with the BP scheme (BPS) without variational operations, the proposed approach effectively enhances the solution accuracy with almost the same inversion time.

Wavelength division multiplexing (WDM) technology is widely used in high-capacity optical communication systems, enabling the simultaneous transmission of multiple signals over optical fiber. However, signal attenuation and dispersion pose significant challenges to long-distance optical transmission. To mitigate these effects, this study investigates the performance of a four-channel dense wavelength division multiplexing (DWDM) network with and without the use of an erbium-doped fiber amplifier (EDFA) and linear chirped fiber Bragg grating (LCFBG). In the absence of EDFA and LCFBG, the signal quality factor (QF) deteriorates as the bit rate increases, with a marked degradation at higher transmission speeds. Our results show that the introduction of EDFA significantly reduces the bit error rate (BER) and improves the QF. Moreover, combining EDFA with LCFBG provides superior performance, effectively compensating for dispersion and attenuation across various transmission distances (0.5, 1, 1.5, and 2 km) and data rates (2, 5, 8, 10, 15, and 20 Gbps). The combination of EDFA and LCFBG outperforms other configurations in terms of signal quality, with a notable improvement in the QF and overall system reliability. These findings suggest that the integrated use of EDFA and LCFBG is an effective solution for enhancing the performance of DWDM systems, especially for long-haul, high-capacity optical transmission.

Improving the efficiency of backward wave oscillators (BWOs) operating in a low magnetic field regime remains a significant research challenge. In this field regime, increased transverse motion of electrons leads to variable interaction impedance. Consequently, the beam wave synchronization with the desired mode is disrupted, resulting in reduced efficiency. To partially overcome this challenge, an adiabatically varying nonuniform slow wave structure (SWS) with a circular ridged wall profile is proposed. The SWS helps in maintaining the synchronization of the beam bunch with the desired normal mode throughout the interaction length. The circular SWS increases the field breakdown limit of the electrodynamic structure. This, in turn, results in an average output power of 810 MW at 9.8 GHz with a power increment of 50% compared to the uniform SWS, guided by a 0.6 T magnetic field. The low magnetic field operation helps in the implementation of a permanent magnet, which results in a repetitive microwave system. The novelty of this work lies in the use of an adiabatically tapered, nonuniform SWS geometry to ensure continuous synchronism at low magnetic fields, which is rarely addressed in conventional BWO designs. This method offers practical significance in reducing system size, weight, and cost by eliminating bulky electromagnets. Further efficiency enhancement is limited by overbunching, which induces Coulomb instability and leads to back-streaming of electrons, as observed in particle-in-cell simulation conducted using CST Microwave Studio.

We propose a multifunctional cascade metasurface designed for manipulating electromagnetic waves in the microwave frequency range with comprehensive theoretical analysis, design optimization, and experimental validation. A set of electrically thin metasurfaces based on planar spirals with free space impedance is used to manipulate electromagnetic waves. The metasurfaces simultaneously generate distinct, independent, and mutually compatible wave transformations at various frequencies. A multifunctional cascade metasurface integrates several functional devices, including a reflective cross-polarizer, a transmissive cross-polarizer, and a nonreflective absorber. Each designed metasurface has a free space impedance over a sufficiently wide frequency range that encompasses the operating frequencies of all metasurfaces. This attribute guarantees the autonomous and mutually noninterfering functioning of all metasurfaces in the cascade.

This paper presents a 28- and 38-GHz bandpass filter for 5G communication systems, which is implemented in an interdigital-coupling microstrip line structure on a Rogers RT5880 substrate. The main resonator is composed of two U-shaped units loaded with short cutoffs and stepped impedance stubs connected at the bottom of the U-shaped structure. The design is effectively tuned to work in the 28 and 38 GHz bands of 5G NR. The LC equivalent circuit of the filter is converted to a physical size of the lumped element by using planar microstrip technology for physical implementation; the suppression in the stop band is lower than −20 dB. The proposed bandpass filter is designed as a microstrip line structure, which can be easily matched with the next level components due to its planar structure. Therefore, it is easier to apply in 5G devices and is suitable for 5G n257 and n260 applications.

A quad-fed triband circularly polarized (CP) patch antenna based on three resonant modes is proposed in this paper. This antenna consists of a square patch loaded with an open cross slots, two pairs of arc slots, and four shorting pins. The acquisition of the three bands is attributed to the simultaneous excitation of TM₁₁ mode of circular patch, TM₁₀ mode of square patch, and the one-wavelength cross slot mode. The TM₁₁ mode of circular patch is excited by the cooperation of the arc slots and the shorting pins, while the loading of the open cross slot moves the TM₁₀ and TM₂₁ modes of the square patch to a higher frequency. Furthermore, the introduction of the arc slots improves the impedance matching of the one-wavelength cross slot mode. The equivalent circuit of the proposed quad-fed patch antenna is established, and its validity is verified. For implementing CP radiation with the same sense in all three bands, a sequential phase feed network is designed and cooperated with the antenna. In order to verify the design concept, an antenna prototype is fabricated and measured. The measured results show that the VSWR is less than 2 in 2.54–5.5 GHz, which can cover the three frequency bands of the proposed antenna. The AR bandwidths in three bands are 33.1%, 27.6%, and 8.6%, respectively. The peak RHCP gains in the three bands are 5, 9.9, and 4.1 dBic, respectively. The profile is 0.032λ₀ (λ₀ is the wavelength in the free space at 3.2 GHz).

This paper presents a new small, low-profile planar triple-band microstrip antenna for WLAN/WiMAX and 5G applications. Nowadays, various wireless services are being integrated into a single device, so these devices require multiband resonant antennas to maintain their compact and portable size. Therefore, the aim of current research was to combine WLAN WiMAX and 5G communication standards together into a single wireless device by designing an antenna that can stimulate triple-band operation. The proposed antenna consists of circular-shaped rectangular slotted radiator encircled by a rectangular ring and a defected ground plane. The designed antenna has a compact size of 20 × 32 mm² (0.16λ₀ × 0.256λ₀). The optimum dimensions were obtained using parametric studies of the key parameters of the antenna. The proposed antenna offers three different bands—I 2.3–2.70, II 3.2–3.92, and III 5.1–5.9 GHz, which clearly covers the entire WLAN (2.4/5.2/5.8 GHz), WiMAX (2.5/3.5/5.5), and 5G bands. Finally, a proposed antenna was built and studied experimentally to verify the design concept as well as validate the simulation results. The good agreement of the simulation results with the measured results proved that the antenna can simultaneously operate on WLAN (2.4/5.2/5.8 GHz), WiMAX (2.5/3.5/5.5 GHz), and 5G frequency bands. This antenna is a suitable candidate for a device that can be used for these three services simultaneously.