Microwave and Optical Technology Letters最新文献

An efficient dual band transmission metasurface capable of generating OAM beams of different orders in the K-band and Ka-band is designed. The proposed metasurface unit consists of an intermediate dielectric substrate layer and two metal resonators for top and bottom layers. By adjusting the rotation angles of different resonators, the circularly polarized transmission phase at the K-band and Ka-band can be controlled independently, with both transmission coefficients larger than 0.8. By using this unit, a metasurface array that generates + 1 order OAM beam at the K-band and + 2 order OAM beam at the Ka-band is realized. Experimental results show that the generated OAM beams exhibit excellent performance, with measured main mode purity at the these two test frequencies is 0.71 and 0.7, respectively. This study provides a solution for generating multi-band OAM beams.

This paper presents a high-precision, compact 6-bit digital attenuator with optimal cascade order that utilizes capacitive compensation. An improved topology is proposed, and the common centroid mathematical model of the resistor array is analyzed based on post-layout simulation, thus further enhancing the performance of the attenuator. The employment of these optimization techniques, in conjunction with the consideration of linearity and impedance variation, has enabled the determination of an optimal cascading sequence for achieving optimal performance. The fabrication of the 6-bit attenuator utilizes a 65-nm CMOS process, resulting in a core area of merely 0.0065 mm². It features ultra-wideband operation with a 31.5 dB tuning range and 0.5 dB adjustment steps. Within the DC-15 GHz frequency range, the insertion loss of the reference state is found to be between 3.6 and 6.4 dB, and the return loss of all 64 states is below −10 dB. The root mean square (RMS) values of amplitude error and phase error are less than 0.5 dB and 3°.

In this paper, a polarization-converting metasurface based on a notched patch with bathe holes is proposed, capable of achieving polarization conversion at arbitrary angles. The unit cell of the metasurface consists of a notched patch with bathe holes on the top layer, a pair of coplanar waveguide (CPW) transmission lines on the bottom layer, and two plated through holes connecting the top and bottom layers. Polarization conversion is achieved by tuning the electrical lengths of the two coplanar waveguide transmission lines in the ground plane. The characteristics of the metasurface polarization converter are theoretically analyzed and validated through full-wave simulations and experimental measurements. The measured results are in good agreement with the simulated ones, indicating its potential applications in electromagnetic stealth and wireless communication systems.

This paper reports a full-rate reference-less bang-bang clock and data recovery (BBCDR) circuit with current mismatch elimination functionality. Specifically, a simplified frequency acquisition loop (FAL) based on lock detection (LD) is proposed to achieve efficient and robust frequency acquisition without the need to determine the polarity of frequency errors. This technique eliminates the need for multiphase clocks and additional high-speed samplers, significantly saving power and area. In addition, a compact current mismatch elimination circuit is introduced to mitigate the impact of the bang-bang phase detector (BBPD) metastability characteristic. Prototyped in 28-nm CMOS, the BBCDR circuit automatically tracks a PRBS-11 none-return-to-zero (NRZ) input between 28.4 and 30.5 Gb/s, with the total chip area being 0.12 mm². At a rate of 30.5 Gb/s, the peak-peak jitter of the recovered clock and data are 2.25 $��\; ��{��\; �\text{ps}�}_{�\text{p-p}��}��$ and 7.31 $��\; ��{��\; �\text{ps}�}_{�\text{p-p}��}��$, respectively, with a core power efficiency of 1.80 pJ/bit.

Radio Frequency Energy Harvesting (RFEH) technique has garnered substantial attention due to its tremendous potential for sustainable and autonomous power supply for Internet of Things (IoT). In response to the prevailing challenges in current RFEH systems, which requires to simultaneously achieve omnidirectional radiation patterns, ultra-wideband characteristics, low-profile design, and further miniaturization and integration with Si-CMOS process, we propose a novel low-profile silicon-based coplanar waveguide antenna with wide radiation angles and ultra-wideband characteristics, fabricated using MMIC technology. Simulation results demonstrate that the designed silicon-based coplanar waveguide antenna exhibits ultra-wideband properties, with a return loss of less than −10 dB across the frequency range of 1–6 GHz. Furthermore, the antenna maintains multi-band operation characteristics in practical testing, achieving an actual return loss of −20 dB within the operational frequency bands and a maximum gain of 1.76 dBi. Moreover, the antenna is applied to a RFEH system, exhibiting an energy conversion efficiency of 16.45%. Our study shows a new venue to design a high-efficient antenna for high-performance RFEH applications.

This letter presents a W-band Colpitts voltage-controlled oscillator (VCO) designed in a 130 nm SiGe BiCMOS process. The proposed VCO employs a push-push harmonic extraction topology to generate the second harmonic output, while a novel optimal capacitance ratio technique is used to minimize the phase noise over the entire tuning range. The output frequency range of this VCO is 92.9 ~ 100.0 GHz, with a phase noise of −90.53 dBc/Hz at a 1 MHz frequency offset. The supply voltage is 2.5 V, and the power consumption of the VCO core and buffer is 80 mW and 32.5 mW, respectively. The chip area of this VCO is 0.438 mm².

This paper presents a 0.35–2 GHz bidirectional true time delay (TTD) transmit/receive (T/R) multifunctional chip utilizing a 0.25-μm GaAs enhancement/depletion (E/d-mode) pseudomorphic high electron mobility transistor (pHEMT) process. The chip integrates several key components: a 6-bit TTD with coverage of 945 ps and a step of 15 ps, a bidirectional amplifier (BA) featuring an improved common source-common gate structure, a 1.6-dB amplitude equalizer (AE), and seven parallel drivers (PDs) for TTD and BA control. The 6-bit TTD employs all-pass networks for the delay path and utilizes three types of reference paths to compensate for the amplitude imbalance between the delay path and the reference path. Meanwhile, the BA employs a dual-C structure combined with dual R-L feedback to mitigate process variation sensitivity significantly. Besides, the 1.6-dB AE is utilized to achieve an overall 1-dB positive gain slope in both transmit and receive modes. In transmit mode, the chip achieves a gain of 4.9–5.9 dB with output power at 1 dB compression point (OP1dB) exceeding 19.3 dBm. In receive mode, the chip achieves a gain of 5.1–6.1 dB, accompanied by a noise figure (NF) lower than 2.56 dB, and an OP1dB larger than 5.4 dBm. Both transmit and receive modes achieve 1-dB positive gain slope. Meanwhile, the transmit and receive root-mean-square (RMS) TTD errors are less than 12.7 and 12.4 ps with associated RMS amplitude errors lower than 0.52 and 0.43 dB, respectively. To the authors' knowledge, this study represents the first demonstration of a GaAs-based bidirectional TTD multifunction chip operating in the UHF band.

Optical waveguides can be used to confine and propagate optical signals. In this study, an optical waveguide was formed by helium ion implantation with an energy of 400 keV and a dose of 6 × 10¹⁶ions/cm² in the Nd³⁺-doped silicate glass. The morphology was examined using a microscope to record its shape. The dark-mode spectrum and corresponding effective refractive indices of the He⁺-implanted Nd³⁺-doped silicate glass waveguide were measured at 632.8 nm by the prism coupling technique. The energy loss, projected range, and longitudinal straggling of the irradiated helium ions were derived by the SRIM 2013 package. The near-field light intensity profile for the He⁺- irradiated Nd³⁺-doped silicate glass waveguide was measured by the end-face coupling system, which is the first observation compared with earlier works. The optical properties of the waveguide suggest that it is a promising candidate for integrated optics systems.

In this letter, a novel reconfigurable filter with multifunction of continuous tunable frequency, bandwidth (BW), and attenuation is proposed. The tunable filter is integrated designed based on a fully tunable filtering coupling structure with external quality factor (Q_e) control and a tunable attenuation unit with impedance transformation capability. The fully tunable filtering coupling structure is deigned using terminal varactor loaded half-wavelength microstrip resonator with tunable center frequency and coupling coefficient. Adjustment of Q_e is realized through the addition of a varactor at the feedline port. Tunable attenuation is achieved by loading PIN diodes through a coupling structure. To improve the efficiency of impedance transformation, an asymmetric structure is employed. The performance degradation of the bandwidth and center frequency due to the tunable attenuation can be compensated by the fully tunable filtering coupling structure. The measurements show that the reconfigurable filter can be tuned from 0.99 to 1.61 GHz with tunable attenuation and bandwidth. The attenuation can be tuned over a range of 30.6 dB at 1.4 GHz, and the fractional bandwidth (FBW) can be tuned from 10% to 30% at 1.3 GHz.

This letter presents a novel frequency-reconfigurable aperture-coupled circular patch antenna based on substrate-integrated suspended line (SISL) technology, designed for single-/dual-band switching and frequency tuning in the C-band. The proposed antenna consists of an aperture-coupled circular patch with a sectoral slot and a biasing circuit to control a single PIN diode or a pair of varactor diodes. The characteristic mode analysis (CMA) was instrumental in the design of the reconfigurable patch and the feeding. The first antenna configuration can switch between single and dual-band operation, with a single band operating at 5.6 GHz with 11.62% fractional bandwidth (FBW) and a peak realized gain of 9.01 dBi, and a dual-band at 5.3/6 GHz with 6.04%/6.17% FBW and 8.57 dBi peak realized gain. The second antenna configuration (with the same physical structure) can tune the operational frequency between 4.84 and 5.89 GHz based on varactor diode reverse bias voltage with a frequency ratio (FR) of 1.22 and achieve a peak realized gain of 9.44 dBi within the tuning range. Both antenna configurations exhibited stable broadside radiation. The total antenna size is $��0.8�\; �{\lambda }_0�\; �\times �\; �0.8�\; �{\lambda }_0�\; �\times �\; �0.06�\; �{\lambda }_0�$, where $��{\lambda }_0�$ is the free space wavelength corresponding to the lowest operating frequency. This study provides a comprehensive solution for next-generation wireless systems by combining a compact platform, innovative feeding mechanisms, and state-of-the-art analysis techniques.