Showing papers on "Insertion loss published in 2022"

Over GHz bandwidth SAW filter based on 32° Y-X LN/SiO2/poly-Si/Si heterostructure with multilayer electrode modulation

Abstract: Enhancing the central frequency ( fc) and bandwidth (BW) and reducing insertion loss (IL) are essential steps in surface acoustic wave (SAW) filter applications in the 5G era. With this in mind, we construct a 32° Y-X LiNbO3(300 nm)/SiO2(300 nm)/poly-Si(1 μm)/Si heterostructure to avoid both acoustic leakage through the waveguide effect and electrical loss through the introduction of a poly-Si layer. By separately modulating the electrode thicknesses of series and parallel resonators, the spurious modes can be mitigated out of the filter passband, preventing them from negatively impacting the filter characteristics. Moreover, to reduce Ohmic loss, an optimized design for an Al/Cu/Ti multilayer electrode is proposed as a replacement for the Cu/Ti electrode resonators built on Al/Cu/Ti electrodes provide a high resonance frequency of 3.76 GHz, a large electromechanical coupling coefficient of 23%, and a maximum quality factor of 1510 (twice that of the Cu/Ti electrodes). Finally, SAW filters with an fc of 3728 MHz and a 3-dB BW of 1052 MHz are implemented, with IL of 0.92 dB. The achieved specifications demonstrates that one-chip SAW filter is expected to become n77 band filtering solution.

Dual-Band Dual-Rotational-Direction Angular Stable Linear-to-Circular Polarization Converter

Abstract: A dual-band dual-rotational-direction reflective linear-to-circular polarization converter based on metasurface is designed, fabricated, and measured. The unit cell consists of an open ring and a square patch. The open ring creates two resonances, and the square patch is used to improve the axial ratio (AR). It is shown that this design can be working at two frequency bands, i.e., 29.0–41.5 GHz and 52.5–61.5 GHz. Interestingly, it is found that the linearly polarized wave in $x(y)$ -direction can be converted into right(left)-handed circularly polarized wave at the former band, and into left(right)-handed circularly polarized wave at the later band. Compared to other designs in the literature, this design demonstrates 45° angular stability for 3 dB AR over two operational bands. In addition, this design is realized on a single substrate, making it easier to be fabricated. Furthermore, the insertion loss can be as low as 0.5 dB, showing a very low-loss property. Lastly, the unit cell is less than 0.2 wavelength at the lower frequency band. The measured results show good agreement with simulation. Potential applications can be envisaged in dual-band and dual-polarization communication.

Connector-style hollow-core fiber interconnections.

Abstract: To go beyond the fundamental limits imposed by latency, nonlinearity, and laser damage threshold in silica glass fibers, the hollow-core fiber (HCF) technique has been intensively investigated for decades. Recent breakthroughs in ultralow-loss HCF clearly imply that long-haul applications of HCF in communications and lasers are going to appear. Nevertheless, up to now, the HCF technique as a whole is still hampered by the limited length of a single span and the lack of HCF-based functional devices. To resolve these two issues, it is of importance to develop ultralow-loss and plug-and-play HCF interconnections. In this work, we report on HCF interconnections with the lowest-ever insertion losses (0.10 dB for HCF to standard single-mode fiber (SMF) and 0.13 dB for HCF to itself in the 1.5 µm waveband) and in a pluggable means. Two fiber mode-field adapters, one based on a graded-index multi-mode fiber (GIF) and the other utilizing a thermally expanded core (TEC) SMF, have been tested and compared. An extra insertion loss arising from imperfect refractive index distribution in a commercial GIF is observed. Our HCF interconnections also realize a back-reflection of <-35 dB over a 100 nm bandwidth as well as other critical metrics in favor of practical applications. Our technique is viable for any type of HCF.

Design and Experiment of 1 THz Slow Wave Structure Fabricated by Nano-CNC Technology

Abstract: This article reports a slow-wave structure (SWS) working at 1 THz which can be fabricated through nano-computer numerical control (nano-CNC) technology for the first time. First, a 1 THz deformed quasi sine waveguide (D-QSWG) SWS has been designed and simulated in this article. To reduce the metal loss of input and output waveguide, a coupler which transit the waveguide to over mode rectangular waveguide has been designed. The simulation result shows that input and output waveguides with this coupler have lower metal loss than that of WR1 rectangular waveguide. To fabricate the designed D-QSWG SWS, tungsten steel endmills have been used. The fabricated SWS has the surface roughness around 58–74 nm, the corresponding effective conductivity is around $2\times 10^{{7}}$ –1.85 $\times 10^{{7}}$ S/m. And the cold test results show that the insertion loss of the fabricated model is less than 30 dB while the reflection loss is less than −15 dB in the frequency range of 0.998–1.016 THz, which has a good consistency with the simulated results. The beam-wave interaction simulation results based on the cold test results show that the designed D-QSWG traveling wave tube (TWT) has the output power of 300 mW, and the 3 dB bandwidth is around 3 GHz.

Silicon photonic flat-top WDM (de)multiplexer based on cascaded Mach-Zehnder interferometers for the 2 µm wavelength band.

Abstract: The 2 µm wavelength band has proven to be a promising candidate for the next communication window. Wavelength-division multiplexing (WDM) transmission at 2 µm can greatly increase the capacity of optical communication systems. Here, we experimentally demonstrate a high-performance silicon photonic flat-top 8-channel WDM (de)multiplexer based on cascaded Mach-Zehnder interferometers for the 2 µm wavelength band. A three-stage-coupler scheme is utilized to provide passbands and reduce channel crosstalk, and 11 thermo-optic phase shifters have allowed active compensation of waveguide phase errors. The fabricated device shows low insertion loss (< 0.9 dB), channel crosstalk (< 20.6 dB) and 1-dB bandwidth of 2.3 nm for operating wavelength ranging from 1955nm to 1985nm. The demonstrated (de)multiplexer could potentially be used for WDM optical data communication in the 2 µm spectral band.

Ultra-low loss waveguide platform in silicon photonics

Abstract: Silicon photonics is the most promising technology for applications ranging from large-bandwidth, low power consumption datacom transceivers, to wearable health monitoring devices, or optical data-bus for quantum processors. To bring silicon PIC based products to the market, ultra-low loss waveguides would be preferred. In the conventional submicron silicon platforms, higher propagation loss (in the order of ~1 dB/cm) induced by the roughness of the etched sidewalls, as well as higher fiber-to-waveguide coupling loss due to its sub-micron dimensions impose challenges for its deployment in many products. VTT’s thick-SOI technology offers a promising alternative, owing to its lower propagation loss (~0.1 dB/cm), reduced polarization sensitivity, and capacity to handle higher optical power without exciting nonlinear losses. Its micron-scale cross-section enables efficient edge coupling. Exploiting its ultra-low loss, we have demonstrated unprecedented level of integration such as, a 40-channel array waveguide grating (AWG) based mux/de-mux, or a Faraday rotator based on silicon spirals, without employing any magneto-optic material. Now we reduced the propagation loss further, down to record-low 4 dB/m, by controlled annealing of waveguides in 100% pure H2 environment. In our optimized, MPW-compatible annealing process, the atomic mobility of Si smoothens the scallops from etching, without causing any structural deformation of the waveguides. This substantially reduced loss enabled us to develop ultra-high Q ring resonators on our thick-SOI platform, as well as sidewall smoothening for the active components, thereby making our platform a bedrock for the emerging applications such as, quantum computing, biosensors, and 3D imaging.

100 GHz micrometer-compact broadband monolithic ITO Mach–Zehnder interferometer modulator enabling 3500 times higher packing density

Abstract: Abstract Electro-optic modulators provide a key function in optical transceivers and increasingly in photonic programmable application-specific integrated circuits (ASICs) for machine learning and signal processing. However, both foundry-ready silicon-based modulators and conventional material-based devices utilizing lithium-niobate fall short in simultaneously providing high chip packaging density and fast speed. Current-driven ITO-based modulators have the potential to achieve both enabled by efficient light–matter interactions. Here, we introduce micrometer-compact Mach–Zehnder interferometer (MZI)-based modulators capable of exceeding 100 GHz switching rates. Integrating ITO-thin films atop a photonic waveguide, one can achieve an efficient V π L ${V}_{\pi }L$ = 0.1 V mm, spectrally broadband, and compact MZI phase shifter. Remarkably, this allows integrating more than 3500 of these modulators within the same chip area as only one single silicon MZI modulator. The modulator design introduced here features a holistic photonic, electronic, and RF-based optimization and includes an asymmetric MZI tuning step to optimize the extinction ratio (ER)-to-insertion loss (IL) and dielectric thickness sweep to balance the trade-offs between ER and speed. Driven by CMOS compatible bias voltage levels, this device is the first to address next-generation modulator demands for processors of the machine intelligence revolution, in addition to the edge and cloud computing demands as well as optical transceivers alike.

High-performance silicon polarization switch based on a Mach–Zehnder interferometer integrated with polarization-dependent mode converters

Abstract: Abstract As the key element for optical systems, polarization controllers with versatile functionalities are highly desired. Here, a CMOS-compatible polarization switch is proposed and realized by using a Mach–Zehnder interferometer integrated with two polarization-dependent mode converters (PDMCs) at the input/output ends. The PDMCs, which utilize the mode hybridness and adiabatic mode evolution in a silicon-on-insulator (SOI) ridge waveguide taper, provide a low-loss adiabatic transmission for the launched TE0 mode as well as efficient mode conversion from the launched TM0 mode to the TE1 mode. For the MZI structure, there are two 1 × 2 dual-mode 3-dB power splitters based on a triple-core adiabatic taper, and two thermally-tunable phase-shifters embedded in the arms. The polarization state and the polarization extinction ratio (PER) of the transmitted light can be dynamically tuned by introducing some phase difference between the MZI arms electrically. The fabricated device has an excess loss of ∼0.6 dB for the TE0 and TM0 modes. When the switch is off, the TE0 and TM0 modes go through the device without exchange. In contrast, when the switch is on, the TE0–TM0 conversion occurs and the measured PER is about 20 dB.

Aluminum scandium nitride thin-film bulk acoustic resonators for 5G wideband applications

Abstract: Abstract Bulk acoustic wave (BAW) filters have been extensively used in consumer products for mobile communication systems due to their high performance and standard complementary metal-oxide-semiconductor (CMOS) compatible integration process. However, it is challenging for a traditional aluminum nitride (AlN)-based BAW filter to meet several allocated 5G bands with more than a 5% fractional bandwidth via an acoustic-only approach. In this work, we propose an Al 0.8 Sc 0.2 N-based film bulk acoustic wave resonator (FBAR) for the design of radio frequency (RF) filters. By taking advantage of a high-quality Al 0.8 Sc 0.2 N thin film, the fabricated resonators demonstrate a large K eff 2 of 14.5% and an excellent figure of merit (FOM) up to 62. The temperature coefficient of frequency (TCF) of the proposed resonator is measured to be −19.2 ppm/°C, indicating excellent temperature stability. The fabricated filter has a center frequency of 4.24 GHz, a −3 dB bandwidth of 215 MHz, a small insertion loss (IL) of 1.881 dB, and a rejection >32 dB. This work paves the way for the realization of wideband acoustic filters operating in the 5G band.

Flat Optical Frequency Comb Generator Based on Integrated Lithium Niobate Modulators

Abstract: Chip-scale electro-optic (EO) frequency combs are expected to play an essential role in future high-capacity optical communications systems and next-generation mobile communications. The application requires integrated EO frequency comb generators featuring good spectral flatness, high modulation bandwidth, low driving voltage and low insertion loss simultaneously. Here, we demonstrate a flat-top optical flat comb (OFC) generator based on high-performance lithium niobate on insulator modulators. The OFC generator shows a low on-chip loss (2.1 dB), a low driving voltage over a broad frequency range, and a large 3-dB EO bandwidth. Moreover, with consuming power of less than 2W, the presented device produces 13 lines with a power variation of less than 1.2 dB and a line spacing of 31 GHz which can further be extended to 67 GHz.

Path-Independent Insertion-Loss (PILOSS) 8 × 8 Silicon Photonics Switch with <8 nsec Switching Time

Abstract: We demonstrate strictly non-blocking and 8 × 8 silicon photonics switch with 10-90% switching time of <8 nsec, on-chip loss of 3.8±0.19 dB independent of path settings, and 20-dB crosstalk bandwidth of ~30 nm. © 2022 The Author(s)

Dual-Frequency Linear-to-Circular Polarization Converter for Ka-Band Applications

Abstract: A dual-band linear-to-circular planar polarization converter based on a multilayer printed circuit board (PCB) is proposed and demonstrated. Each cell of the periodic surface is formed by six substrate layers separated by five foam spacers. The three top layers are identical and contain an ‘I’-type strip, while the three layers on the bottom side are realized with three identical Jerusalem crosses (JC). A linearly polarized (LP) wave tilted 45° relative to the x- and y-axis of the converter is used to illuminate the polarizer. In this configuration, right-handed circularly polarized (RHCP) waves are generated at the Ka-band while left-handed circularly polarized (LHCP) waves are generated at the K-band. An equivalent circuit model based on transmission lines is proposed and used to design the polarizer together with full-wave simulations. The simulated/measured axial ratio (AR) remains below 3 dB in the bands 19.4–21.8 GHz (12.5%) and 27.9–30.5 GHz (8.7%) with an insertion loss better than 0.5 dB.

Double Busbar Structure for Transverse Energy Leakage and Resonance Suppression in Surface Acoustic Wave Resonators Using 42°YX-Lithium Tantalate Thin Plate

Abstract: This article describes a new transverse edge structure with double busbar for surface acoustic wave (SAW) devices employing a 42°YX-lithium tantalate thin plate such as incredible high-performance (I.H.P.) SAW. This design offers good energy confinement and scattering loss suppression for a wide frequency range. First, preexisting transverse edge designs are reviewed, and their difficulties are pointed out using the dispersion relation for lateral SAW propagation. Then, numerical simulations are performed using the periodic 3-D finite-element method (FEM) powered by the hierarchical cascading technique, and effectiveness of the proposed structure is revealed. In addition, we also provide a possible solution to expand the frequency range giving well energy confinement and demonstrate effectiveness of manipulating the SAW slowness curve shape for transverse mode suppression.

Heterogeneously integrated lithium niobate photonics

Abstract: We demonstrate a hybrid L iNbO3-Si3N4 photonic integrated platform with propagation loss of 8.5 dB/m at wafer scale. The platform exhibits low insertion loss (4 dB) and precise lithographic control. We also demonstrate a number of applications of the platform.

Millimeter-Wave Waveguide-to-Microstrip Inline Transition Using a Wedge-Waveguide Iris

Abstract: A novel waveguide-to-microstrip inline transition was proposed using a wedge-waveguide iris to form an ultra-compact U-bend waveguide. The wedge-waveguide iris not only functioned as a wide wall of the height-reduced waveguide for the $E$ -plane probe, but also played a critical role in impedance matching and parasitic resonance suppression. The working principle was investigated through theoretical analysis and full-wave simulation, and the relevant design processes for the transition were discussed. Moreover, two back-to-back transition prototypes, one working at the $W$ -band and the other working at the WR4.3 band, were designed, fabricated, and measured. The back-to-back prototypes obtained an insertion loss of less than 0.8 and 1.2 dB, with a return loss better than 15 dB in the $W$ -band and WR4.3 band, respectively. The measurement results were consistent with simulation results. A miniaturized 110-GHz tripler incorporating this transition for inline output was fabricated. A conversion efficiency of 2.5%–3.6% was achieved in 90–120 GHz at 100-mW driving power.

Wideband Hybrid Couplers With Unequal Power Division/Arbitrary Output Phases and Applications to Miniaturized Nolen Matrices

Abstract: In this article, a new design approach for developing hybrid couplers with arbitrary power division and the phase difference is presented. The design is based on a transformer-based coupler with high isolation between sum and difference ports. Based on this model, a modified coupler is developed by including two L-shaped networks to produce constant phase differences at two output ports. Slotlines and microstrip-to-slotline transitions are used for expanding the bandwidth and introducing a 180° phase difference at the difference port. Two prototypes with equal and unequal power division are designed and verified. Experimental results reveal that the proposed designs can achieve constant phase difference, low insertion loss, and satisfactory matching across a broad bandwidth of more than 40%. Based on the proposed designs, a simplified multibeam Nolen matrix is also designed utilizing only three hybrid couplers and no phase shifters. The compact beamforming network demonstrates that the proposed component is very useful for size reduction in wireless communication systems.

An Isolated Out-of-Phase 3-dB Power Divider via Waveguide-to-Microstrip Transition

Abstract: In this letter, we present a 3-dB power divider with isolated port. The input port is a rectangular waveguide and two output ports are microstrip lines. The measured results of the power divider show above 12-dB minimum isolation over 13–16 GHz, with an input return loss of better than 15 dB. The return loss of the output ports is better than 10 dB, with an insertion loss of lower than 0.35 dB. A maximum amplitude imbalance of about 0.15 dB is observed within 13–16 GHz, with a phase imbalance of better than 2.5°. The proposed power divider in this letter is compact and good integration with the monolithic microwave integrated circuit (MMIC) devices.

A 3-D Printed 300 GHz Waveguide Cavity Filter by Micro Laser Sintering

Abstract: This article explored the use of high-precision metal three-dimensional printing in subterahertz waveguide devices and demonstrated a 300 GHz waveguide bandpass filter made by micro laser sintering (MLS) process. The filter structure is composed of five rectangular waveguide cavities (fundamental TE101 mode), two back-to-back right-angle bends and WR-03 waveguide sections. It is made of two identical blocks of stainless steel and two brass plates were used to clamp them together and achieve secure contact in the E plane cut. The measured response of the as fabricated stainless-steel filter showed minimum passband insertion loss of 4.7 dB due to the degraded effective conductivity of the stainless steel and surface roughness. To reduce the insertion loss, the filter was gold plated using an electro-less process with nickel undercoat layer. Plating the filter significantly improved the passband insertion loss, measured to be between 1.1 and 2.7 dB. Inspection of the filter using an Alicona optical system showed that dimensional accuracy within ± 15 μm on average has been achieved by the MLS printer. The investigative study tested the boundary of the technology in subterahertz device applications.

Silicon Multimode Waveguide Crossing Based on Anisotropic Subwavelength Gratings

Abstract: Multimode waveguide crossings (MWCs) are becoming more and more important as one of the key elements for on‐chip optical routing and cross‐connection. However, it is still very challenging to achieve scalable MWCs with compact footprints, low excess losses (ELs), and low intermode cross‐talks (CTs). This work demonstrates an unprecedented silicon MWC with high performances by using the anisotropy of one‐/two‐dimensional (1D/2D) subwavelength grating (SWG) structures. For the proposed silicon MWC, the 2D‐SWG crossing region at the center has a higher refractive index than the 1D‐SWG regions at both sides for the guided‐modes of TE polarization, due to the anisotropy of the 1D/2D SWGs. As a result, the crossing region can be equivalent to a straight waveguide, and the launched TE modes can transmit through the crossing region with negligible ELs and low intermode CTs. Such an MWC can be scaled very flexibly and easily according to the new principle. The fabricated three‐mode MWC with a footprint of 14.8 × 14.8 µm2 shows ELs of <0.26 dB and intermode CTs of <−20 dB in the wavelength range of 1525–1605 nm.

Low-Loss Calibration-Free 2 × 2 Mach-Zehnder Switches With Varied-Width Multimode-Interference Couplers

Abstract: Large-scale photonic switches are essential components for telecommunications and interconnects, incorporating many cascaded 2 × 2 optical switches. To keep the excess loss of the entire switch low, it is crucial to develop ultralow-loss 2 × 2 optical switches by introducing new coupler designs. In this paper, a low-loss calibration-free 2 × 2 Mach-Zehnder switch (MZS) designed with varied-width multimode-interference (MMI) couplers is proposed and fabricated. In this design, the MMI coupler has a varied-width MMI region and two multimode output waveguides. The MMI coupler optimized by the particle swarm optimization (PSO) algorithm has an ultralow excess loss < 0.053 dB and a suppressed higher-order mode excitation < −26 dB across the C-band (1530–1565 nm). Such a varied-width MMI coupler with two multimode output waveguides can be used compatibly for the MZS with widened phase shifters, so that the random phase imbalance between the two MZS arms can be suppressed effectively, which thus is promising for calibration-free operation. For the present MZS fabricated with standard 180-nm silicon photonic foundry processes, the excess loss is ∼0.5 dB across the C-band and the extinction ratio is ∼25 dB without calibration.

A 23‐ to 28‐GHz 5‐bit switch‐type phase shifter with 1‐bit calibration based on optimized ABCD matrix design methods for 5G MIMO system in 0.15‐μm GaAs

Abstract: The fifth‐generation (5G) mobile communication system is being developed to provide ultra‐high‐speed and large‐capacity wireless communication services. However, due to the large transmission loss in the air for high‐frequency signals, it is necessary to use large‐scale array antennas to achieve adaptive control of antenna directivity to compensate for the loss. This paper reports a passive phase shifter operating at 23–28 GHz. The proposed 5‐bit switch‐type phase shifter with 1‐bit calibration is designed in a 0.15‐μm GaAs process. A new design method based on the optimized ABCD matrix and impedance matching techniques between a chip and a printed circuit board (PCB) is developed to obtain better radio‐frequency (RF) signal transmission. The proposed phase shifter features a good‐phase performance with a measured root‐mean‐square (RMS) phase error of less than 10° across 23–28 GHz. For all the phase shift states, the insertion loss is 18 ± 2 dB at 28 GHz and the RMS gain error is less than 2.1 dB over 23–28 GHz including pads and RF connector loss. The phase shifter consumes no DC power and occupies a chip area of 2 × 0.7 mm2 including all the pads.

A Terahertz Band-Pass Filter Based on Coplanar-Waveguide and Spoof Surface Plasmon Polaritons

Abstract: A THz ultra-broadband band-pass filter based on coplanar-waveguide and spoof surface plasmon polaritons (SSPPs) is proposed, which can be operated from 0.65 THz to 2.02 THz with high efficiency and compact size. Additionally, the lower and upper cut-off frequencies of the proposed filter can be controlled independently by changing the corresponding parameters. The interdigital structure is used to filter the low frequency wave, meanwhile, the SSPPs is designed for producing the upper cut-off frequency. The operating principles are explained by dispersion curves and field distributions. The return loss and insertion loss of the proposed filter are higher than 11 dB and less than 2 dB in the passband, respectively. For validating the proposed band-pass filter design concept, a prototype of a filter operating at millimeter-wave frequency is fabricated and measured, and the measured results have a good agreement with the simulated ones.

A Hybrid Filter With Extremely Wide Bandwidth and High Selectivity Using FBAR Network

Abstract: An extremely wideband hybrid bandpass filter (BPF) with high selectivity and low insertion loss is proposed in this brief. The hybrid BPF is composed of three coupled lines (CLs), six matching transmission lines (TLs) and two film bulk acoustic resonator (FBAR) networks with ladder-type structure. These two FBAR networks can help greatly enhance the upper and lower sideband roll-off of the hybrid BPF. At the same time, the passband is compensated by CLs and TLs. The odd-even mode theory is used to analyze the hybrid BPF to obtain the analytical solutions. Through electromagnetic-acoustic co-simulation and optimization, a hybrid BPF with extremely wideband is fabricated and measured. A discussion on the deviation between the simulation and the measured results is presented. The measured hybrid BPF has a 3-dB fractional bandwidth of 56 %, a minimum insertion loss of 1.733 dB and a shape factor of 0.83 simultaneously.

A High-Efficiency 142–182-GHz SiGe BiCMOS Power Amplifier With Broadband Slotline-Based Power Combining Technique

Abstract: In this article, a high-efficiency broadband millimeter-wave (mm-Wave) integrated power amplifier (PA) with a low-loss slotline-based power combing technique is proposed. The proposed slotline-based power combiner consists of grounded coplanar waveguide (GCPW)-to-slotline transitions and folded slots to simultaneously achieve power combining and impedance matching. This technique provides a broadband parallel–series combining method to enhance the output power of PAs at mm-Wave frequencies while maintaining the compact area and high efficiency. As a proof of concept, a compact four-to-one hybrid power combiner is implemented in a 130-nm SiGe BiCMOS back-end-of-line (BEOL) process, which leads to a small die area of 126 $\mu \text{m}\,\,\times $ 240 $\mu \text{m}$ and a low measured insertion loss of 0.5 dB. The 3-dB bandwidth is over 80 GHz covering the whole G-band (140–220 GHz). Based on this structure, a high-efficiency mm-Wave PA has been fabricated in the 130-nm SiGe BiCMOS technology. The three-stage PA achieves a peak power gain of 30.7 dB, 3-dB small-signal gain bandwidth of 40 GHz from 142 to 182 GHz, a measured maximum saturated output power of 18.1 dBm, and a peak power-added efficiency (PAE) of 12.4% at 161 GHz. The extremely compact power combining methodology leads to a small core area of 488 $\mu \text{m}\,\,\times $ 214 $\mu \text{m}$ and an output power per unit die area of 662 mW/mm ² .

Novel High Isolation and High Capacitance Ratio RF MEMS Switch: Design, Analysis and Performance Verification

Abstract: In this paper, a novel high isolation and high-capacitance-ratio radio-frequency micro-electromechanical systems (RF MEMS) switch working at Ka-band is designed, fabricated, measured and analyzed. The proposed RF MEMS switch mainly consists of a MEMS metallic beam, coplanar waveguide (CPW) transmission line, dielectric layer and metal–insulator–metal (MIM) fixed capacitors. The measured results indicate that the insertion loss is better than 0.5 dB at 32 GHz, and the isolation is more than 35 dB at the resonant frequency. From the fitted results, the capacitance ratio is 246.3. Compared with traditional MEMS capacitive switches, this proposed MEMS switch exhibits a high capacitance ratio and provides a wonderful solution for cutting-edge performance in 5G and other high-performance applications.

Reconfigurable Liquid Metal-Based SIW Phase Shifter

Abstract: This article presents the first substrate integrated waveguide (SIW) phase shifter that can be reconfigured using liquid metal (LM). This digital phase shifter exhibits low insertion loss and is reciprocal and bidirectional. It incorporates a series of holes which can be filled or emptied of liquid metal, enabling us to add or remove via connections dynamically, on-the-fly. Using a collection of such holes, it is possible to create a wall along the E-plane or H-plane of the waveguide. When the wall is in place, it blocks the passage of energy. When the wall is absent, energy is able to flow. In this way, it is possible to guide the electromagnetic (EM) waves through one of three paths, having different electrical lengths. The result is a digital switched-line phase shifter that achieves coarse steps of phase change, from 0° up to 180°, in steps of 60°. By filling or emptying individual holes, it is possible to introduce reactive loading into each path. In this way, it is possible to achieve fine phase control in steps of 10°. Using both forms of reconfiguration in unison, the proposed phase shifter is able to deliver a phase shift of up to 180°, in steps of 10°. The proposed phase shifter operates at 10 GHz and exhibits an insertion loss of less than 2.3 dB over its entire operating band. Furthermore, the underlying concept of the proposed phase shifter can be readily scaled for operation in the millimeter-wave (mm-wave) band. The existing phase shifters operating in that band exhibit significant insertion losses. MM-wave phase shifters are expected to find application in 5G mobile access points.

High-Production-Rate Fabrication of Low-Loss Lithium Niobate Electro-Optic Modulators Using Photolithography Assisted Chemo-Mechanical Etching (PLACE)

Abstract: Integrated thin-film lithium niobate (LN) electro-optic (EO) modulators of broad bandwidth, low insertion loss, low cost and high production rate are essential elements in contemporary interconnection industries and disruptive applications. Here, we demonstrated the design and fabrication of a high performance thin-film LN EO modulator using photolithography assisted chemo-mechanical etching (PLACE) technology. Our device shows a 3-dB bandwidth over 50 GHz, along with a comparable low half wave voltage-length product of 2.16 Vcm and a fiber-to-fiber insertion loss of 2.6 dB. The PLACE technology supports large footprint, high fabrication uniformity, competitive production rate and extreme low device optical loss simultaneously, our result shows promising potential for developing high-performance large-scale low-loss photonic integrated devices.

Inverse design of a binary waveguide crossing by the particle swarm optimization algorithm

Abstract: This paper describes the inverse design of the particle swarm optimization algorithm combined with the three-dimensional finite-difference time-domain simulation to design a waveguide crossing that resembles a binary code. The device consists of 15 × 15 air holes in a 220-nm silicon slab on a 3-μm-thick SiO2 substrate with one input port and three output waveguide ports. The designed device has a small footprint of 4μm2 and a short simulation time of 1.7 h. In the wavelength range of 1.5–1.6μm, the device has insertion loss IL<0.85 dB and crosstalk XT<−14.5 dB. This device tolerates air hole-position disordering of ηp=23%, and hole-radius disordering of ηr=35%, so it is appropriate to use in the complementary metal–oxide–semiconductor fabrication process. The paper also proposes integrated interconnections that contain 2 × 2 waveguide crossings and have IL<2.9 dB and XT<−13 dB, and 3 × 3 waveguide crossings that have IL<5 and XT<−12.5 dB.

A Harmonic-Free Wilkinson Power Divider Using Lowpass Resonators

Abstract: This paper presents a Wilkinson power divider (WPD) capable of suppressing unwanted bands up to 16th harmonic with high isolation. In this WPD, a lowpass filter composed of a main resonator and three bended stubs are used to guarantee a wide stopband. The presented WPD illustrates suitable performance at 0.85 GHz for GSM applications. Isolation between of output ports, input return loss and insertion loss are better than 24 dB, 20 dB and 3.4 dB, respectively.