Insertion Loss Degradation Research Articles

Compact SOI Dual-Mode (De)multiplexer Based on the Level Set Method

Mode (de)multiplexer is an essential device in integrated multimode photonic systems. Here, we present a dual-mode (de)multiplexer that separates two input modes, TE0 and TE1, into two output ports while converting TE1 to TE0 mode. Based on the adjoint and level set method, the device features a small footprint of 9.4 μm × 2.9 μm, and a minimum feature size over 200 nm is achieved, affirming stable and reliable fabrication. Through simulations, we observed insertion losses of less than 0.28 dB for TE0 mode and 0.35 dB for TE1 mode within the wavelength range of 1500–1600 nm, accompanied by crosstalk levels lower than −30 dB. In our experimental tests, we achieved insertion losses of less than 0.89 dB for TE0 mode and 0.44 dB for TE1 modes within the 1530 nm to 1570 nm range, with crosstalk maintained below −25 dB. Furthermore, we conducted an experimental verification of the differences between the standard device and the boundary dilation/erosion device, observing an insertion loss degradation by 0.61 dB within a deviation range of ±40 nm, which demonstrates the device’s robustness to the fabrication. The proposed devices exhibit exceptional performance and feature a compact structure, thus holding significant potential for the development of future multimode integrated photonic circuits.

Numerical Insight Into the Origin of Nonreciprocity and Performance Enhancement in Nonreciprocal Bandpass Filters Using Evolutionary Algorithm

In this paper, a non-reciprocal filter with enhanced directivity is analyzed methodically, and the filter parameters are optimized using an evolutionary algorithm. The non-uniform spectral dispersion of power among the harmonics in opposite directions is substantiated with the aid of filtering polynomials. These polynomials indicate the origin of at least one transmission zero within the passband in the reverse direction, thereby promoting the non-reciprocal filter response. The filter’s return loss, insertion loss, and isolation characteristics exhibit a trade-off that demands an optimization algorithm to effectuate the judicious choice of circuit parameters. This problem is addressed by designing a 150 MHz lumped element non-reciprocal bandpass filter based on the parameters extracted using an evolutionary algorithm based particle swarm optimization (PSO). The simulated and measured results comply well with the modeling, and the results exhibit maximum directivity of 28.2 dB without degradation in insertion loss (1.1 dB) and return loss (16.2 dB) within the passband. The algorithm can be utilized in designing non-reciprocal filters having different center frequencies and bandwidths.

Method of the out-of-band rejection improvement of the AlN based surface acoustic wave filters

AlN based surface acoustic wave (SAW) filters with an acoustic wavelength (λ) of 8 µm have been fabricated based on sputtered AlN films on sapphire. The acoustic velocity of 1-µm-AlN/Sapphire bilayer structure is 5536 m/s, 60% higher than that of LiNbO3. The central frequency, insertion loss, out-of-band rejection, and bandwidth of fabricated AlN based two-port type SAW filters with a delay gap of λ are 692 MHz, 25.58 dB, 35.40 dB, and 2.7 MHz, respectively. The impact of delay gap on the performance of AlN based filters have been studied experimentally. By the analysis of frequency response of SAW filters with delay gaps of λ, 15λ, and 30λ with and without time gating technique, we find that increase the delay gap of AlN based SAW resonators can improve the out-of-band rejection effectively because of the reduction of electromagnetic coupling, with a cost of a little degradation of insertion loss due to the small propagation loss of AlN/Sapphire bilayer. When the delay gap is increased from λ to 15λ, out-of-band rejection of AlN based filters is increased by 4.75 dB, while the insertion loss is only increased by 0.81 dB. When the delay gap is further increased from 15λ to 30λ, the suppression of out-of-band rejection is not obvious.

Decoupling Structures for Millimeter Wave Integrated Circuits in Digital CMOS Processes

This brief studies the effect of nonideal decoupling structures on the performance of single-ended circuits operating at the millimeter wave frequency range. Based on a first-order approximation, an upper limit on the impedance of decoupling structures is derived, given a prespecified accepted degradation in insertion loss. To verify the analysis, a 110-GHz single-ended amplifier with a compact decoupling structure based on distributed interdigitized metal-oxide-metal capacitor is implemented. The full-wave electromagnetic simulations of the decoupling structure show an input impedance of (0.47 – j0.12) $\Omega $ at 110 GHz, and the magnitude is less than $1~\Omega $ from 82 to 144 GHz. The degradation in the insertion loss of the matching network is simulated to be less than 0.5-dB compared with the use of ideal decoupling capacitors at 110 GHz. The area of the decoupling structure is $18\times 100 ~\mu \text{m}^{2}$ when implemented in 65-nm digital CMOS process.

Modeling up to 45 GHz of coupling between microvias and PCB cavities considering several boundary conditions

The recent developments in electronic cards such as the network equipment are characterized by the miniaturization of the board size and the increasing complexity of the layout. Because of these requirements, multi-layered printed circuit boards are commonly used and vias connecting signal lines on different layers, or integrated circuit devices to power and ground planes, are frequently used and often essential. However, a via is not an ideal transmission line. Besides, it creates discontinuities at high frequencies leading to high insertion loss degradation of signal which limits the performances of integrated circuit and systems. In this paper, the impacts of coupling between via and parallel-plates cavity on the response of microwave integrated devices are highlighted in the first part. Then, to describe the intrinsic interaction between the via transition and parallel-plate modes, the notion of parallel-plates matrix impedances is presented and new boundary conditions like open or plated through holes shielded boundaries of the cavities are introduced. Then, using this physics-based model, an intuitive equivalent circuit has been developed. Finally, the proposed approach and the equivalent circuits were validated by using comparisons with electromagnetic simulations and measurements in different scenarios.

Modeling and Quantification for Electromagnetic Radiation of Power-Bus Structure With Multilayer Printed Circuit Board

The ground bounce noises in a power distribution network of multilayered stack-ups in electronic packages and boards will cause simultaneous switching noise coupling, high insertion loss degradation of signal via, and stray radiation. These lead to signal integrity, power integrity, and electromagnetic compatibility problems. This paper presents an efficient numerical method for evaluating the radiation emission from power-bus structure in complex electronic packaging of high-speed integrated circuit system. It is based on the discretization technique and the boundary integral equation. First, the variational field distribution on the peripheral surfaces of power-bus structure induced by the return current is calculated by using the Helmmholtz equation and boundary conditions. The peripheries of power–ground (P/G) planes and via are discretized into small elements. Then, the changing transient impedance at the edge of antipad plate caused by displacement current through P/G planes is calculated with the assumptive exciting current 1 mA. Finally, the far field radiation is obtained through equivalent magnetic current of edge field. Cavity-model analysis is used to verify, and the good agreement with the theoretical prediction validates the correctness and efficiency of the present analysis.

Quasi-elliptic evanescent-mode filters using non-resonating mode waveguide cavities

A new technique to realize quasi-elliptic bandpass filters with extreme close-in rejection is presented in this paper. The basic idea consists of embedding non-resonating mode waveguide cavities within the structure of an evanescent-mode filter. Such a combination of cavities and resonators allows the generation of very close transmission zeros while realizing at the same time relatively wide passbands and stopbands. Both H-plane TE201 mode and E-plane TM110 mode configurations are used as non-resonating mode waveguide cavities. In contrast with the other elliptic evanescent-mode filters using conventional approaches, the insertion loss degradation at the filter cut-off frequencies is minimized thanks to the high-Q factor of the waveguide cavities, whose corresponding poles are located right at the edges of the passband. The experimental results of an evanescent-mode filter having 9.950–11.000 GHz passband and providing more than 45 dB rejection between 11.040 and 11.050 GHz validate the proposed solution.

Influence of titania cladding on SOI grating coupler and 5 μm-radius ring resonator

Titania cladding is deposited on a 5μm-radius silicon-on-insulator ring resonator and grating couplers which are patterned by deep-ultraviolet lithography. The influence of titania cladding is studied by measuring the transmission spectra of the ring resonator coupled to a pair of single-mode fibers through the grating couplers. Temperature dependent wavelength shift of TE-like mode through the ring resonator is reduced to −20 to +20pm/K from 74pm/K without a noticeable degradation of insertion loss through the ring and the transmission peak of grating coupler is shifted at about 50nm by the addition of titania cladding.

Modeling, Quantification, and Reduction of the Impact of Uncontrolled Return Currents of Vias Transiting Multilayered Packages and Boards

The returning displacement currents of vias transiting multilayered stack-ups in electronic packages and boards excite parasitic transverse electromagnetic modes in power-ground plane pairs, causing them to behave as parallel-plate waveguides. These waves may cause significant coupling in the power-ground cavity, leading to electromagnetic reliability (EMR) issues such as simultaneous switching noise coupling, high insertion loss degradation of signal vias, and stray radiation from the periphery/edges of the package/board. In this contribution, we model and quantify EMR problems caused by uncontrolled return currents of signal vias in conventional multilayer stack-ups. Traditional methods used to minimize these problems, and their limitations are discussed. We propose a low-cost layer stack-up, which overcomes most of the limitations of conventional stack-ups by providing well-defined return-current paths for microstrip-to-microstrip via transitions. Test samples of the proposed configuration are designed, fabricated, and measured. Very good correlation is obtained between measurement and simulation. Finally, a circuit model for the microstrip-to-microstrip via transition, considering the return-current paths, is developed and the circuit parameters are analytically calculated. Conventional closed-form expressions used for the extraction of these parameters, particularly the via capacitance, are extended and modified.

Design of a digital, ultra-broadband electro-optic switch for reconfigurable optical networks-on-chip

We present a novel design for a noise-tolerant, ultra-broadband electro-optic switch, based on a Mach-Zehnder lattice (MZL) interferometer. We analyze the switch performance through rigorous optical simulations, for devices implemented in silicon-on-insulator with carrier-injection-based phase shifters. We show that such a MZL switch can be designed to have a step-like switching response, resulting in improved tolerance to drive-voltage noise and temperature variations as compared to a single-stage Mach-Zehnder switch. Furthermore, we show that degradation in switching crosstalk and insertion loss due to free-carrier absorption can be largely overcome by a MZL switch design. Finally, MZL switches can be designed for having an ultra-wide, temperature-insensitive optical bandwidth of more than 250 nm. The proposed device shows good potential as a broadband optical switch in reconfigurable optical networks-on-chip.

A High-Linearity Single-Pole-Double-Throw Pseudomorphic HEMT Switch Based on Tunable Field-Plate Voltage Technology

A high-isolation high-linearity GaAs pseudomorphic high-electron mobility transistor single-pole-double-throw microwave switch was developed using a tunable field-plate (FP) bias voltage technology. In this paper, a piece of FP metal was deposited between 0.15-mum-long gate and drain terminals. An extra FP-induced depletion region was generated to suppress the harmonics of switching associated with OFF-state operation. When switching into the ON-state, the FP switch is associated with an insertion loss similar to that of the standard switch below 6 GHz. However, the isolation performance can be enhanced by 10 dB using an FP technology, which reduces the OFF-state capacitance that is produced by the extra FP-induced depletion region. The FP provides an additional mechanism to suppress the power of the second- and third-order harmonics in the OFF-state with slight ON-state insertion-loss degradation.

Temperature dependence of low loss polymeric AWG

We investigate on the variation of loss and temperature dependence of a polymeric arrayed waveguide grating (AWG) depending on its substrate, by fabricating 16-channel polymeric AWGs with various substrate conditions. Insertion loss for a polymeric AWG on a silicon substrate is measured as low as 3.1dB. The temperature-dependent wavelength shift for a polymeric AWG detached from the substrate is maintained within 0.1nm from 20 to 80°C. But we observe a degradation of insertion loss and a little instability in wavelength characteristics both for the detached polymeric AWG and for a polymeric AWG on a polymer substrate. We investigate on those optical properties of the polymeric AWGs based on measured thermal expansion properties of the polymers.

Ladder-type bulk acoustic wave filter with common ground inductor

The present invention relates to a ladder-type bulk acoustic wave filter with a common ground inductor, which obtains high attenuation in a high frequency stop band adjacent to a pass band without the insertion loss degradation of the pass band, so that the ladder-type bulk acoustic wave filter is useful as a transmit filter. According to the present invention, the plurality of shunt resonators are commonly grounded through the inductor, so that zeros are generated due to the interaction between the stray capacitance of shunt resonators and the common ground inductor, thus improving attenuation characteristics in a high frequency stop band.

15-GHz fully integrated nMOS switches in a 0.13-/spl mu/m CMOS process

Two fully integrated nMOS switches have been demonstrated at 15 GHz in a 0.13-/spl mu/m CMOS foundry process. One incorporates on-chip LC impedance transformation networks (ITNs) while the second one does not. The switches with and without ITNs achieve the same 1.8-dB insertion loss at 15 GHz, but 21.5 and 15 dBm input P/sub 1dB/, respectively. The degradation of insertion loss due to use of ITNs is compensated by reducing the mismatch loss caused by the bond pad parasitics. The switch without ITNs is suitable for 3.1-10.6 GHz ultra-wide-band (UWB) applications. The switch with ITNs has /spl sim/5 dB worse isolation than the switch without. The difference is due to the larger transistor size of the switch with ITNs, which introduces lower parasitic impedance path between Tx/Rx ports and antenna port.

DC-110-GHz MMIC traveling-wave switch

This paper presents the broadest band monolithic-microwave integrated-circuit traveling-wave switch ever reported for millimeter-wave applications. The developed switch with the novel structure of a 400-/spl mu/m-gate finger field-effect transistor (FET) indicated an insertion loss of less than 2.55 dB and an isolation of better than 22.2 dB from dc to 110 GHz. Also, the switch indicated no degradation of insertion loss and an ON/OFF ratio of more than 22.7 dB up to an input power of 26.5 dBm at 40 GHz. Circuit analytical results based on a lossy transmission-line model for small-signal performance and circuit simulation results using the two-terminal nonlinear FET model for large-signal operation successfully showed good agreement with the experimental results.

The Image Source-Virtual Barrier Model for Prediction of Reflection Effects from Barriers

This study employed a computer program to identify the insertion loss degradation of barrier due the reflection. The mathematical theories of single barrier prediction are based on Maekawa prediction [1], which predicts the attenuation produced by the barrier as a function of geometry and frequency. The single image source concept was used for estimating the reflection effect of the second barrier. A scale model of a scale 1:20 and a line source made of small speakers were used to verify the accuracy of the computer program. The results from the program agree well with those of scale models. The results show that the region of where the illuminated zone of the virtual source and the shadow zone of the primary source overlap (Ys1 < Y < Ys) is the critical region of noise degradation. Thus, the image source model with a virtual barrier is a very useful and straight-forward tool for the design of parallel barriers. Four barrier design parameters have been analyzed; sound source position, barrier height, distance between parallel barriers and the usefulness of absorptive material applied at the second barrier.

A theoretical model for parallel noise barriers

The conventional approach for modeling parallel noise barriers has been mostly based on using the single barrier theory with image sources to model the reflected fields. This approach does not take into account diffraction in the field between the two barriers. The conventional method also tends to predict higher insertion loss degradation than field measurements have shown. A theoretical model is proposed to include diffraction in the part of the field due to single or multiple reflections. For the reflected field between the barriers, a barrier is assumed to act as a baffled sound source whose pressure amplitude and phase are given by that of the reflected wave. The source field and the barrier shape are unrestricted. In this case, only the reflected portion of the incident wave propagates back to the opposite barrier whereas in the image source method the whole incident wave is reflected. The angular spectrum method is used to calculate the field from the various reflections. The new model is compared to various other calculations and published field measurements.

A review of parallel traffic noise barrier literature

It is widely accepted that a single noise barrier beside a highway will provide a degree of noise reduction for neighboring homes. An interesting issue arises when residential areas line both sides of the highway, requiring two parallel barriers, one on each side of the highway. An abundance of research has been carried out to examine this situation. The research suggests that this configuration allows for multiple reflections to occur between the two barriers, unfortunately resulting in less noise reduction for both residential areas. Researchers attacking this problem have uncovered many relevant issues. This paper will summarize these issues and will class them into those in which there is consensus and those in which there is no consensus. Researchers agree that multiple reflections exist in a parallel wall situation, that these reflections cause an insertion loss degradation, that the insertion loss degradation can be controlled, and that making barriers absorptive or tilting them is effective in reducing the degradation. They do not agree on the extent of insertion loss degradation, the significance of environmental variables such as ground cover, or the limits to improvements from absorptive or tilting barriers.

Novel high-isolation FET switches

This paper describes novel high-isolation monolithic microwave/millimeter-wave integrated circuit (MMIC) field-effect transistor (FET) switches that have higher isolation characteristics than conventional switches without much insertion loss degradation. The newly developed switches consist of series/shunt FETs and T-shaped R-C-R circuit. Each FET switch utilizes the parasitic capacitive component of the FETs in the off-state to produce a band-rejection filter at the operating frequency. The design method of the newly proposed switches and their characteristics are described herein. With this method, the isolation characteristics are improved by more than 15 dB between 5.4 GHz and 6.4 GHz and more than 20 dB between 5.5 GHz and 6.1 GHz over conventional values.

A Review of Studies of Insertion Loss Degradation for Parallel Highway Noise Barriers

A Review of Studies of Insertion Loss Degradation for Parallel Highway Noise Barriers