Insertion Loss Research Articles

A broadband low‐loss SPDT RF switch using a new off‐chip compensation technology

SummaryAn off‐chip compensation technology for low‐loss and broadband characteristics of radio frequency (RF) switches is proposed based on mathematical analysis of series shunt single pole double throws switches in this letter. This compensation technology can absorb the parasitic parameters of the switch Field Effect Transistor, improving the insertion loss and return loss of the switch as well as supporting higher bandwidth. To verify the design principle, a RF switch, using the SANAN GaAs 0.15 um pseudomorphic High Electron Mobility Transistors (pHEMT) process, and an off‐chip compensation network were designed and implemented. Specifically, after using an off‐chip compensation network, the measured bandwidth of switch has been expanded from 1.1–8.8 to 0.8–11 GHz, while the input and output return loss have also improved significantly.

Dynamic characteristics of bladder type attenuator for hydraulic systems

Flow ripples caused by the pump will lead to system failure or equipment damage. The bladder type attenuator is utilised to suppress flow ripples in piping systems, though its mathematic model has not been given out precisely. In this paper, the governing equations of the hollow cylindrical shell describing the bladder’s behaviour are studied. Considering the bladder’s viscoelastic materials, the constitutive function is obtained through DMA (Dynamic thermo-mechanical analysis) test and the WLF (Williams–Landel–Ferry) equation. Thus, the dynamic model of the attenuator can be written as an impedance expression, which consists of integral, fractional, constant, and differential components. Three experiments are carried out to validate the theoretical models. The static and dynamic models of the bladder are validated by experiments, indicating good agreement. The impedance model of the attenuator is validated by a hydraulic experiment assessed with the IL (insertion loss) index, showing high accuracy. All models proposed in this work are proven to be effective and accurate, and can be used to evaluate and optimise the bladder type attenuator theoretically.

22/43 GHz low-insertion-loss dual-polarized multi-layer bandpass frequency selective surfaces for millimeter astronomy

We design a frequency selective surface (FSS) capable of transmitting K-band and reflecting Q-band radio waves. The equivalent circuit approach assists the distribution of multi-layer FSS to achieve a third-order bandpass response with an incident angle of less than 30°. The unit structure consists of three metal layers embedded with two dielectric substrates. Especially, the FSS provides a 3 dB transmission bandwidth range from 18.6 to 26.7 GHz with a maximum measured insertion loss of 0.61 dB. Hence the proposed polarization-insensitive FSS with low insertion loss can be applied in the observation system of millimeter astronomy.

Design and Simulation of a System-in-Package Chip for Combined Navigation.

This paper proposes a system-in-package combination navigation chip. We used wire bonding, chip stacking, surface mount, and other processes to integrate satellite navigation chips, inertial navigation chips, microprocessor chips, and separation devices. Finally, we realized the hardware requirements for combined navigation in a 20 mm × 20 mm chip. Further, we performed a multi-physics simulation analysis of the package design. For antenna signals, the insertion loss was greater than -1 dB@1 GHz and the return loss was less than -10 dB@1 GHz. The amplitude of these noises of the signal between the MCU and the IMU was approximately 20%, and the maximum value of the coupling coefficient between signal lines on the top surface was 13.4174%. The ninth mode of the power plane yielded a maximum voltage of 55 mV, and all power delivery networks had a DC voltage drop of less than 2%. The highest temperature in the microsystem was approximately 42 °C. These results show that our design performed well in terms of signal, power, and thermal performance.

Harmonic Suppressed Wilkinson Power Divider Using Parallel Resonant Shunt Stub

This paper proposes a harmonic-suppressed Wilkinson power divider (HS WPD) utilizing parallel resonant shunt stubs (PRSSs). PRSSs are integrated into the conventional WPD by adding functionalities such as bandpass filtering, harmonic suppression, and physical port separation. The resonance conditions and design equations of the PRSS are theoretically derived and verified through circuit simulations. Using the PRSS, we designed an HS WPD operating at 1 GHz. The fabricated HS WPD demonstrated an insertion loss of 3.2 dB at the fundamental frequency, with a wide 3 dB bandwidth of 129%. The harmonic suppression levels at the 2nd and 3rd harmonic frequencies are measured to be 21.0 dB and 25.8 dB, respectively. The measured input return loss at the fundamental frequency was 27.9 dB, whereas the output return loss was 24.6 dB. Additionally, the HS WPD demonstrates isolation levels at the fundamental, 2nd, and 3rd harmonic frequencies, with levels of 29.2 dB, 17.8 dB, and 47.1 dB, respectively. It also exhibited broadband isolation (>8.7 dB) across the frequency range of 100 kHz to 3.35 GHz. The PRSS design allows for the physical separation of the ports without requiring additional circuitry. Compared to previously reported PDs, the proposed design offers multiple functions in a compact size, making it highly suitable for various microwave systems.

A Compact Bandpass Filter with Widely Tunable Frequency and Simple Bias Control

This research paper introduces an innovative design for a compact bandpass filter, notable for achieving a substantial tuning range of operational frequencies using just a single bias voltage. The design is based on a planar microstrip approach, distinguished by its straightforward and efficient structure. Additionally, this filter is characterized by its excellent performance in suppressing out-of-band frequencies. To validate the practicality and effectiveness of this novel design, a compact filter was designed, manufactured, and measured. The testing results were impressive, showing that the filter’s measured center frequency could be tuned across a wide spectrum, from 1.1 to 3.1 GHz, achieving a relative bandwidth of up to 95%. Herein, the relative bandwidth is derived from the calculation of 2(fhigh − flow)/(fhigh + flow). Remarkably, the filter consistently maintains a return loss exceeding 19 dB throughout its tuning range. Additionally, it sustains a 15 dB return loss bandwidth greater than 90 MHz, with the insertion loss varying between a minimum of 0.9 dB and a maximum of 2.1 dB. The compactness of the filter is one of its standout features, with circuit dimensions measuring a mere 0.06λg × 0.09λg (physical dimensions is 13.8 mm × 21.3 mm), where λg represents the wavelength at the filter’s lowest center frequency.

Compact all-optical half adder based on topology optimization

We proposed an inverse-designed compact half adder on a silicon-on-insulator platform with a footprint of 2µm×2µm. The optical power of SUM and CARRY is controlled by different input combinations, according to the truth table of a half adder. Topology optimization is applied to cope with multiple objective functions in such a combinational logic circuit. The transmittance at 1550 nm for CARRY with 11 input is 170.2%, with extinction ratios (ERs) of 27.1 and 5.8 dB for SUM and CARRY, respectively. The SUM and CARRY outputs have ERs over 22.0 dB and 5.7 dB from 1515 nm to 1600 nm. Phase condition and morphology analysis show that the device has high tolerance on phase fluctuation and fabrication. The proposed device with compact footprint, low insertion loss, and large bandwidth presents a novel, to the best of our knowledge, approach to achieve all-optical combinational logic circuits with inverse design.

Cost analysis of ultrawideband transmission in optical networks

We examine the cost associated with increasing traffic on a reference transport network for both single- and multiband systems, with a total transmission bandwidth ranging from 4.8 to 20 THz (S2 + S1 + C + L-band, where S2 and S1 are the two halves of the S-band). The number and cost of amplifiers, transceivers, and fibers are considered. To ensure stable transmission power and simplified network management, we take noise loading into account. The optimal combination of transmission bands—for each system—is evaluated based on the maximization of the capacity calculated from the minimum per-band generalized signal-to-noise ratio of each band. The results reveal that, despite the lower spectral efficiency due to the higher fiber attenuation and band MUX/DEMUX insertion losses, multiband systems can effectively reduce the number of fibers needed, thus postponing the deployment of new fibers. The most cost-effective solution depends on the fiber and S-band amplifier costs and the forecast of the required network capacity. When additional fibers are freely available or fiber costs are minimal, employing a C-band-only system proves to be the most economical choice. As fiber costs increase, additional bands gradually become more appealing, progressing from the C-band-only to the C + L-band, and then to the addition of half of the S-band (S1 + C + L-band) or the whole S-band (S2 + S1 + C + L). Furthermore, multiband transmission systems are more attractive when considering higher traffic loads. We also propose an optimal order of deployment of transmission bands in a pay-as-you-grow approach. The corresponding cost evolution demonstrates that this approach is a viable solution to mitigate excessive costs during the initial stages of a network operation, even though it leads to an increased number of fibers and transceivers used before all transmission bands are enabled. Additionally, we show that the S1- and S2-bands have worse optical performance, making them more suitable for shorter lightpaths. Consequently, operating the S-band in single-hop links and simplifying the add-drop multiplexer architecture could be beneficial.

Single-wideband and dual-band bandpass filters based on compact quadruple-mode resonator

A stub-loaded U-shaped microstrip resonator (U-SLR) exciting two odd-modes and two even-modes and its applications to single-wideband and dual-band bandpass filter (DB-BPF) are introduced. The parallel-coupled lines (PCLs) at input/output (I/O) ports can provide a wideband response by exciting two additional modes in the passband, so-called PCLs modes. In addition to the transmission poles (TPs) in the passband, two transmission zeros (TZs) in the lower and upper stopbands can be created by the loaded stubs. A compact size, high-selectivity, and low insertion loss WB-BPF is designed, fabricated, and tested. Moreover, a compact and low loss DB-BPF with closely spaced passbands is designed and tested. TZ-shifting method is used to design a DB-BPF by splitting the wideband. To achieve this, it is sufficient to change the length of only one of the loaded stubs. The calculated, simulated and measured frequency responses for both single-wideband and DB-BPFs are in very good agreement.

Analyzing Three Types of Design Methods for 5G N41 Band Acoustic Wave Filters

This paper presents three design methods for acoustic wave (AW) filters: the direct conversion design method, the slope parameter method, and the band edge fitting method (BEFM). Since the conventional BVD model consists only of lumped elements and has accuracy only near the resonance frequency, an NM-BVD model capable of broadband modeling is proposed in this paper and used to design the filter. In the proposed BEFM, a systematically optimal filter method is used to design the AW filter, and each AW resonator is tuned to the filter prototype value to meet the desired specifications. Thus, the filter design time and the number of resonators can be efficiently improved, and the filter design time can be reduced compared with the direct conversion and slope parameter methods commonly used in filter design. To demonstrate the effectiveness of these design methods, the proposed methods were used to design and fabricate an N41 filter using scandium-doped aluminum nitride (ScAlN) resonators. The broadband capabilities of the filter were verified using BEFM. The design, fabrication, and measurement of a broadband filter that meets the requirements of the 5G N41 frequency band centered at 2.593 GHz with a bandwidth of 196 MHz have verified the filter fabricated using the proposed design method. The insertion loss is less than -3 dB in the target band and more than 30 dB out of band. In summary, the proposed BEFM provides an efficient and accurate method for designing AW filters.

Optical 2-bit nanoscale multiplier using MIM waveguides.

The plasmonic 2-bit multiplier is designed at a 1310nm operating wavelength and a 65% transmission threshold (T t h r e s h o l d ). Using the finite element method (FEM) with the COMSOL version 15 software, we simulated the suggested 2-bit multiplier, based on the principle of the constructive and destructive interferences between the input light waves. The results were delivered in graphs containing the transmission level (T) versus an operating wavelength range between 800 and 2000nm, magnetic field distribution, modulation depth (MD), contrast ratio (CR), and insertion loss (IL). The modulation depth was 99.91%, the CR was 14.75dB, and the IL was -1.2d B.

Low loss and ultra-broadband design of an integrated 3 dB power splitter centered at 2 µm.

Because chemical gas is sensitive to absorption in the 2µm band, and 2µm matches the absorption band of the remote sensing material, many remote sensors and optical sensors are designed to operate in the 2µm wavelength region. In this paper, we designed an integrated 3dB power splitter centered at 2µm. The study of this device is built on a silicon-on-insulator (SOI) platform. We introduced a subwavelength grating (SWG) to improve the performance of the device. We used the three-dimensional finite-difference time-domain (3D FDTD) method to analyze the effect of the structure on the power splitter. The insertion loss (IL) of the fundamental TE mode is only 0.04dB at 2µm and its bandwidth of IL <0.45d B is 940nm (1570-2510nm). It is suitable for multidomain and all-band photonic integrated circuits at 2µm.

Design of an IMI optical 2 × 4 decoder circuit based on square disk resonators.

This paper presents the design of a 2×4 decoder that was developed by using the finite element method (FEM) in conjunction with the COMSOL version 5.5 software. Insulator-metal-insulator (IMI) waveguides with four substructures were used in the fabrication of the plasmonic decoder. Gold is used as a conducting material. Thisis a challenge for us, while Teflon is used as a dielectric material in the fabrication process. The dimensions of thispart are 1090nm by 400nm. At an operating wavelength of 1550nm, the transmission threshold (T t h r e s h o l d ) of this scheme has been determined to be 10%. In order to assess the effectiveness of the plasmonic decoder, it is recommended that the modulation depth (MD), contrast ratio (CR), and insertion loss (IL) parameters be carried out. Both the highest values of CR and MD are 12.33 decibels, and the maximum value of MD is 99.96%. It is because of these qualities that this work is distinguished from earlier works.

Study of Multi-Channel Mode-Division Multiplexing Based on a Chalcogenide-Lithium Niobate Platform

A multi-channel mode-division multiplexing based on a chalcogenide-lithium niobate platform using chalcogenide films with adjustable refractive index is proposed, with the aim of overcoming issues with narrow bandwidth and large crosstalk in conventional multiplexers. An asymmetric directional coupler, employing chalcogenide-based thin-film modulation, was designed to realize the multiplexing and separation of TE1, TE2, and TE3 modes. Simulations show that the device is capable of obtaining an insertion loss of between 0.03 dB and 0.7 dB and a crosstalk of between −21.66 dB and −28.71 dB at 1550 nm. The crosstalk of the TE1, TE2, and TE3 modes is below −20.1 dB when accessing the waveguide output port in the 1500–1600 nm band. The proposed multiplexer is a promising approach to enhance the transmission capability of thin-film lithium-niobate-integrated optical paths.

2D material platform for overcoming the amplitude–phase tradeoff in ring resonators

Compact and high-speed electro-optic phase modulators play a vital role in various large-scale applications including optical computing, quantum and neural networks, and optical communication links. Conventional electro-refractive phase modulators such as silicon (Si), III-V and graphene on Si suffer from a fundamental tradeoff between device length and optical loss that limits their scaling capabilities. High-finesse ring resonators have been traditionally used as compact intensity modulators, but their use for phase modulation has been limited due to the high insertion loss associated with the phase shift. Here, we show that high-finesse resonators can achieve a strong phase shift with low insertion loss by simultaneous modulation of the real and imaginary parts of the refractive index, to the same extent, i.e., ΔnΔk∼1. To implement this strategy, we demonstrate an active hybrid platform that combines a low-loss SiN ring resonator with 2D materials such as graphene and transition metal dichalcogenide [tungsten disulphide (WSe2)], which induces a strong change in the imaginary and real parts of the index. Our platform consisting of a 25 µm long Gr-Al2O3-WSe2 capacitor embedded on a SiN ring of 50 µm radius (∼8% ring coverage) achieves a continuous phase shift of (0.46±0.05)π radians with an insertion loss (IL) of 3.18±0.20 dB and a transmission modulation (ΔTRing) of 1.72±0.15dB at a probe wavelength (λ p ) of 1646.18 nm. We find that our Gr-Al2O3-WSe2 capacitor exhibits a phase modulation efficiency (Vπ2⋅L) of 0.530±0.016V⋅cm and can support an electro-optic bandwidth of 14.9±0.1GHz. We further show that our platform can achieve a phase shift of π radians with an IL of 5 dB and a minimum ΔT of 0.046 dB. We demonstrate the broadband nature of the binary phase response, by measuring a phase shift of (1.00±0.10)π radians, with an IL of 5.20±0.31dB and a minimal ΔTRing of 0.015±0.006dB for resonances spanning from 1564 to 1650 nm. This SiN–2D hybrid platform provides the design for compact and high-speed reconfigurable circuits with graphene and transition metal dichalcogenide (TMD) monolayers that can enable large-scale photonic systems.

On-chip passive pump-rejection long-pass filters for integrated SiC-based nonlinear and quantum photonic chips

We present an on-chip passive pump-rejection filter on an integrated silicon carbide (SiC)-on-insulator photonic platform. Our filters exploit the optical absorption from an amorphous silicon (α-Si) thin-film layer deposited on the top surface and on the sidewalls of the SiC waveguide to reject light with a wavelength below 1.0 µm. The filter has a simple design and can be readily fabricated using a standard semiconductor wafer fabrication process and can be integrated as a pump-rejection filter component for SiC-based nonlinear and quantum photonic chips. We experimentally demonstrate a pump-rejection efficiency exceeding 230 dB/mm for 780 nm wavelengths, while we extract an insertion loss of ∼1 dB for the O-, C-, and L-bands.

A segment-coupled six-mode multiplexer based on multi-core fiber

In this paper, a segment-coupled six-mode multiplexer based on multi-core fiber (MCF) is proposed to achieve multiplexing of LP01, LP11, LP21, LP02, LP31 and LP12 modes according to the principle of mode coupling and phase matching. The mode multiplexer consists of a two-part fiber waveguide that supports six modes of transmission at 1.55 μm wavelength. The transmission performance is analyzed with the finite element method (FEM) and the beam propagation method (BPM). The simulation results show that the insertion loss (IL) of the mode multiplexer is less than 1 dB in the wavelength range of 1.5439–1.5558 μm, and the lowest IL is 0.1837 dB. The coupling efficiencies (CEs) of the six modes are 99.7 %, 92.0 %, 98.6 %, 98.3 %, 97.4 % and 86.6 %, respectively. The designed mode multiplexer dramatically improves fiber space utilization while achieving more higher-order mode conversion. The mode multiplexer can be applied to the mode division multiplexing (MDM) system to solve the problem of mode multiplexing and demultiplexing.

Temperature and Twist Sensor Based on the Sagnac Interferometer with Long-Period Grating in Polarization-Maintaining Fiber.

We utilized a CO2 laser to carve long-period fiber gratings (LPFGs) on polarization-maintaining fibers (PMFs) along the fast and slow axes. Based on the spectra of LPFGs written along two different directions, we found that when LPFG was written along the fast axis, the spectrum had lower insertion loss and fewer side lobes. We investigated the temperature and twist characteristics of the embedded structure of the LPFG and Sagnac loop and ultimately obtained a temperature sensitivity of -0.295 nm/°C and a twist sensitivity of 0.87 nm/(rad/m) for the LPFG. Compared to the single LPFG, the embedded structure of the LPFG and Sagnac loop demonstrates a significant improvement in temperature and twist sensitivities. Additionally, it also possesses the capability to discern the direction of the twist. The embedded structure displays numerous advantages, including easy fabrication, low cost, good robustness, a wide range, and high sensitivity. These features make it highly suitable for applications in structural health monitoring and other related fields.

Compact module for complementary-channel THz pulse slicing

We present a modular quasi-optical pulse slicer designed for use at terahertz (THz) frequencies. Given a quasi-cw input, the two outputs of a module are (1) a pulse with programmable duration and (2) its complement. The quasi-optical design incorporates a laser-driven silicon switch at Brewster's angle to the incoming THz beam, which limits undesired reflections before the switch is activated such that THz power is only transmitted when the switch is “on.” An “off” switch ensures that no power is leaked after the pulse and that the switching profile is sharp. The slicer's small footprint (0.048×0.072×0.162 m3) and small insertion loss (1.2 dB at 320 GHz) as well as high switching efficiency (∼70%) allows modules to be stacked to create multiple pulses. The output channel that is not used for experiments can be used for concurrent analysis of beam parameters. Stacking modular assemblies will enable more complex sequences of kW-level pulses than are currently achievable for applications including free-electron-laser or gyrotron-powered pulsed electron spin resonance at high magnetic fields.

Performance analysis of PLC-based 32-channel arrayed waveguide grating used for FBG interrogator

The Fiber Bragg grating (FBG) is an optical fiber component that reflects or diffracts optical signals of specific wavelengths through periodic refractive index changes inside it. Currently, the use of arrayed waveguide grating (AWG) to interrogate such optical signals is a popular research topic at present. Using the planar lightwave circuit, we designed and fabricated a 32-channel AWG. The AWG has an insertion loss of less than 4 dB, a 3 dB bandwidth of about 1.76 nm, and a crosstalk of non-adjacent channels of less than −28 dB. Additionally, we integrated the AWG with a photodetector (PD) array and built a corresponding wavelength interrogation system, which was tested using three different interrogation methods. The test results indicate that when using the linear fitting, this AWG provides the best results using the dual-channel edge filtering method with an interrogation range of 1.6 nm and an interrogation accuracy of 18.9–20.1 pm. The interrogation accuracies of the relative intensity method are 9.4 pm and 3.7 pm when Gaussian and Lorentzian fittings are used.