Single Input Port Research Articles

Self-configuring programmable silicon photonic filter for integrated microwave photonic processors

Reconfigurable photonic filters show great promise as a potential solution to meet the evolving needs of future microwave communication systems. By integrating high-performance filters into programmable microwave photonic processors, they can provide significant benefits for signal processing applications. The development of an algorithm that can automatically characterize and reconfigure the filter using a single optical input and output port is essential for this purpose. This paper presents an optimization technique for a fully tunable ring-assisted Mach–Zehnder interferometer filter. The proposed filter design eliminates the need for monitoring components and employs a novel algorithm that operates independently in each ring by switching between the two arms of the filter. In addition, the filter can be configured to implement different filter architectures, allowing for flexible filtering requirements. Measurements were performed using the device as an interleaver, implementing different types of infinite impulse response filters in the optical and radio frequency domains. Side-coupled integrated spaced sequence of resonator filters were also implemented by reconfiguring the same device. These results demonstrate the exceptional reconfigurability of the filter design proposed herein in terms of bandwidth and central frequency.

Integrated Microwave Antenna/Sensor for Sensing and Communication Applications

In this article, a dual-functional microwave system with a single input port that can simultaneously be used for antenna and sensor applications is presented. The dual-functional ability of the proposed system is achieved by integrating a two-port microwave sensor and a Wi-Fi antenna with a novel frequency-selective multipath filter (FSMF). The FSMF ensures efficient system operation by not affecting the operational bandwidth of the communicating antenna in the presence of different sensed materials under test (MUTs) on top of the sensor. The proposed microwave sensor also has a unique capability of measuring one more sensing parameter in addition to the often used reflection and transmission coefficients. The additional parameter is the frequency distance of two closely spaced resonance frequencies of the microwave sensor in the presence of an MUT. Compared to existing state-of-the-art techniques, the additional sensing parameter (as done in this work) can be used as an alternative to transmission coefficient for characterization of different MUTs or as an additional parameter giving more degree of freedom. The entire system is designed in a single substrate with a common input source. The performance of the dual-functional system was tested using different MUTs and showed a good agreement with the measurement results.

An Antenna Based on Three Coupled Dipoles With Minimized E-Field for Ultra-High-Field MRI

In this work, we demonstrate an approach for local reduction of the electric field amplitude of the transmitted radio-frequency signal in ultrahigh-field magnetic resonance imaging (MRI). We excite a suitable combination of three coupled dipole hybrid resonances composing a single transmit antenna array element. Using numerical optimization, we designed a feeding network for three coupled dipoles placed over an electromagnetic phantom mimicking a human body. This network of discrete elements provides the appropriate amplitudes and phases of three dipole currents excited by a single input port. It allows controlling the electric field distribution in the vicinity of the antenna. Our goal was to obtain a minimum of the electric field at the given relatively small depth inside the phantom, where body implants are typically located while keeping a tolerable level of the magnetic field toward the phantom’s center. We designed and manufactured a three-dipole antenna prototype optimized for MRI of the human body at 7 T (proton Larmor frequency of 298 MHz). The experimental validation showed a 40 dB reduction of the electric field amplitude at a depth of 4 cm compared to a conventional single-dipole antenna. The coupling network can be rearranged to target different depths. Therefore, a principle of electric field minimization at a controllable position inside the body has been shown, which may be useful for designing transmit MRI antennas with improved safety of implants.

Router1x3 Protocol Design Implementation and Verification with Virtual Cut through Mechanism for Network on Chip (NoC)

Hundreds of processors and memory cores are implemented on a single substrate called the System on Chip (SoC). The SoC with bus-based architecture has restrictions on the processing speed of the system and as the design becomes complex and the issue of scalability arises. Hence NoC is designed to enhance the scalability, data reliability, and processing speed with low power consumption by decoupling communication from computations [1]. Using NoC the IP cores of SoC are connected through on-chip routers and send data to each other through packet switching. The router is a processing chip that decides the right path for data transmission, hence the efficient design of the router is essential to enhance the performance and throughput of the system [2]. To reduces latency through the switch, the Virtual cut-through mechanism is a packet switching technique, in which the switch starts forwarding a packet as soon as the destination address is processed by header. Hence the present work focuses on a router input-output protocol design with the Virtual Cut-through mechanism for closed-loop communication. Router 1x3 has a single input port and three output ports. The architecture of Router 1x3 with sub-modules such as FIFO, FSM, Synchronizer, and Register is designed analyzed and verified using Verilog, System Verilog language, and Universal Verification Methodology(UVM). And it is also implemented on Xilinx 14.5 IDE with Spartan-6- XC6SLX45 FPGA.

Phase‐Modulated Interferometry, Spectroscopy, and Refractometry using Entangled Photon Pairs

AbstractThe authors demonstrate a form of two‐photon‐counting interferometry by measuring the coincidence counts between single‐photon‐counting detectors at an output port of a Mach–Zehnder Interferometer (MZI) following injection of broad‐band time‐frequency‐entangled photon pairs (EPP) generated from collinear spontaneous parametric down conversion into a single input port. Spectroscopy and refractometry are performed on a sample inserted in one internal path of the MZI by scanning the other path in length, which acquires phase and amplitude information about the sample's linear response. Phase modulation and lock‐in detection are introduced to increase detection signal‐to‐noise ratio and implement a “down‐sampling” technique for scanning the interferometer delay, which reduces the sampling requirements needed to reproduce fully the temporal interference pattern. The phase‐modulation technique also allows the contributions of various quantum‐state pathways leading to the final detection outcomes to be extracted individually. Feynman diagrams frequently used in the context of molecular spectroscopy are used to describe the interferences resulting from the coherence properties of time‐frequency EPPs passing through the MZI. These results are an important step toward the implementation of a proposed method for molecular spectroscopy—quantum‐light‐enhanced 2D spectroscopy.

Beam combining of fiber lasers by a 3 × 1 signal combiner at a power >13 kW

An all-fiber 3 × 1 power combiner with each input port being capable of handling comparatively high power is demonstrated in this paper. Both of the simulation and experiment are investigated. Three self-made Yb-doped fiber lasers with a center wavelength of 1080 nm and maximum output power of 4.5 kW are applied in the experiment. An average output power of 13.06 kW is obtained when a total power of 13.2 kW are launched into the power combiner. The experimental results illustrates that the total efficiency is approximate 99% and the beam quality is M2 ≈ 6, which is close to the simulation results. To best of our knowledge, this is the highest handling power for the each input port as well as total output power for 3 × 1 combiners ever reported. The results indicates a higher capability of handling power for a single input port and higher total power scaling for a 3 × 1 signal combiner.

Differential Sensing Based on Quasi-Microstrip Mode to Slot-Mode Conversion

In this letter, a differential sensor and comparator based on a mode conversion detector implemented by means of a slotline resonator is proposed for the first time. The sensor divides the input signal between two identical sensing elements, a pair of microstrip lines loaded with complementary split-ring resonators (CSRRs). Such CSRRs are symmetrically etched in the ground plane at both sides of the slotline. Therefore, by truncating symmetry, e.g., by loading one of the CSRRs with the reference (REF) sample and the other one with the sample under test (SUT), the slot mode is generated in the slotline resonator. The signal level associated with this mode, which can be inferred by means of a slotline/microstrip transition, depends on the level of asymmetry generated by CSRR loading. Consequently, the proposed structure is useful for differential sensing, where a single input and output port suffices to excite the sensor and to measure the output variable, the magnitude of the transmission coefficient.

Inter-polarization mixers for coherent detection of optical signals.

Electro-magnetic (EM) mixers are fundamental building blocks in communication systems. They are used in frequency/wavelength filters, interferometric modulators, amplitude-phase receivers, to name a few. Traditional EM mixers have two or more input ports and work only for co-polarized signal and local-oscillator (LO) incident on its inputs. Here we report on novel designs, in silicon, of inter-polarization EM mixers operating at 1550 nm wavelength. The 180-degree optical mixer comprising a single input port is demonstrated to coherently mix orthogonally polarized signal and LO. Using the proposed 180-degree mixer, we report on a novel design for a 90-degree optical mixer on silicon with small footprint, broadband response, low loss and good fabrication tolerance. It exploits birefringence of a waveguide to achieve broadband and fabrication-tolerant 90° phase difference between the signal/LO relative phase in the in-phase and quadrature components. A monolithic silicon photonics coherent receiver is demonstrated using the reported 90-degree mixer, and its operation at 22 Gbaud and 44 Gbaud is shown. These mixers pave the way for novel coherent receiver architectures in long-haul, metro, passive optical networks and data-center interconnect applications.

Performance analysis of triple asymmetrical optical multiple ring resonator with a 1 × 3 input-output waveguide for application as an optical filter.

Modelling of a triple asymmetrical optical multiple ring resonator (TAOMRR) with a 1×3 input-output waveguide has been carried out in the present paper, and its performance as an optical filter is analyzed. The mathematical modelling of the proposed configuration is carried out in the z domain using a delay line signal processing technique. Free spectral range (FSR), group delay, and dispersion characteristics of the proposed TAOMRR are evaluated from the frequency response plot obtained in MATLAB from all the possible input-output port configurations. The field analysis of the proposed configuration is realized using the finite difference time domain (FDTD) method. The optimal coupling coefficient obtained from the MATLAB simulation is used to design the various optical couplers in FDTD analysis. The proposed configuration offers three outputs with different FSRs for a single input port, which greatly enhances the data handling capabilities in communication networks.

Design and Implementation of a 16-Word by 1-Bit Register File Using Adiabatic Quantum Flux Parametron Logic

We have been developing extremely energy-efficient microprocessors using the adiabatic quantum flux parametron (AQFP) logic. In this study, we designed and fabricated an AQFP register file, which is one of the key building blocks in the microprocessor. The 16-word by 1-bit register file with dual output ports and a single input port was designed by using an AQFP cell library with a minimalist design. The circuit is composed of three decoders and feedback delay latches (D-latches), which are clocked by four-phase excitation currents. The circuits were fabricated using the AIST 10 kA/cm2 Nb process. The total junction number and circuit area are 2544 and 3.1 mm × 5.4 mm, respectively. The estimated energy consumption is 18 aJ per clock cycle for 5 GHz operation. The latency is 1600 ps for 5 GHz operation. In the low-speed test, we confirmed the correct operations across 15 addresses.

Theory and Implementation of RF-Input <newline/>Outphasing Power Amplification

Conventional outphasing power amplifier systems require both a radio frequency (RF) carrier input and a separate baseband input to synthesize a modulated RF output. This work presents an RF-input/RF-output outphasing power amplifier that directly amplifies a modulated RF input, eliminating the need for multiple costly IQ modulators and baseband signal component separation as in previous outphasing systems. An RF signal decomposition network directly synthesizes the phase- and amplitude-modulated signals used to drive the branch power amplifiers (PAs). With this approach, a modulated RF signal including zero-crossings can be applied to the single RF input port of the outphasing RF amplifier system. The proposed technique is demonstrated at 2.14 GHz in a four-way lossless outphasing amplifier with transmission-line power combiner. The RF decomposition network is implemented using a transmission-line resistance compression network with nonlinear loads designed to provide the necessary amplitude and phase decomposition. The resulting proof-of-concept outphasing power amplifier has a peak CW output power of 93 W, peak drain efficiency of 70%, and performance on par with a previously-demonstrated outphasing and power combining system requiring four IQ modulators and a digital signal component separator.

Reconfigurable Square-Ring Microstrip Antenna

A reconfigurable design for a dual-feed square-ring microstrip patch antenna is described. The dual feeds are used to excite two orthogonal modes of the antenna, and each feed network is composed of a coupling patch, an impedance transformer, and a variable capacitor. In addition, the two feeds are connected to a single input port through a T-junction power divider. The proposed design can perform polarization diversity at different frequencies by tuning the capacitance values of the two capacitors. A prototype integrating with a pair of varactor diodes and related dc bias circuits is constructed. Typical experimental results are shown along with numerical simulation results. Both of them demonstrate that the prototype can provide one linear polarization and two circular polarizations at one operating frequency; moreover, the operating frequency can also be tuned to adjacent frequencies.

Analysis of Large-Scale Multi-Stage All-Optical Packet Switching Routers

All-optical packet switching can overcome limitations of electronic switches in terms of power consumption, speed, cost, and footprint. Switch architectures combining wavelength converters and fiber delay lines provide tunable routing and contention resolution when used with an N×N arrayed waveguide grating (AWG), a key passive optical component to bypass electronic processing limitations. An AWG passively routes either single or multiple input port wavelengths to output ports. A single wavelength per port strategy reduces crosstalk within the AWG, but drastically increases the dimensionality of the device. AWG design constraints due to bandwidth limitations and fabrication processes limit the port number for the foreseeable future to under 100. In order to scale optical switches to emerging network requirements, we must use multiple wavelengths per port. In this paper, we examine several optical router architectures for data center applications using multiple wavelengths per port, and quantify the physical layer impairments. We consider not only the AWG crosstalk, but also Q-factor degradation caused by the multiple wavelength conversions occurring when a packet is buffered for contention resolution. We present the results as a function of the number of recirculations for on–off-keying (OOK) signal formats. While previous work has addressed this issue in terms of accumulated loss, we focus on accumulated intensity noise due to crosstalk and amplified spontaneous emission (ASE). We compare the routing performance of each architecture, and we point out that the AWG crosstalk and accumulated ASE noise during packet recirculation are both critical to the routing performance.

Interfacing microfluidics to LDI-MS by automatic robotic spotting

We developed a method of interfacing microfluidics with mass spectrometry (MS) using a robotic spotting system to automate the contact spotting process. We demonstrate that direct and automated spotting of analyte from multichannel microfluidic chips to a custom microstructured MALDI target plate was a simple, robust, and high-throughput method for interfacing parallel microchannels using matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS). Using thermoplastic cyclic olefin copolymer (COC) polymer microfluidic chips containing eight parallel 100 μm × 46 μm microchannels connected to a single input port, spotting volume repeatability and MALDI-MS signal uniformity are evaluated for a panel of sample peptides. The COC microfluidic chips were fabricated by hot embossing and solvent bonding techniques followed by chip dicing to create open ends for MS interfacing. Using the automatic robotic spotting approach, microfluidic chip-based reversed-phase liquid chromatography (RPLC) separations were interfaced with electrochemically etched nanofilament silicon (nSi) target substrate, demonstrating the potential of this approach toward chip-based microfluidic separation coupled with matrix-free laser desorption/ionization mass spectrometry.

Methodology for Efficient Substrate Noise Analysis in Large-Scale Mixed-Signal Circuits

A methodology is proposed to efficiently analyze substrate noise coupled to a sensitive block due to an aggressor digital block in large-scale mixed-signal circuits. The methodology is based on identifying voltage domains on the substrate by exploiting the small spatial voltage differences on the ground distribution network of the aggressor circuit. Specifically, similarly biased regions on the substrate short-circuited by the ground network are determined, and each of these regions is represented by a single equivalent input port to the substrate. The remaining ports within that domain are ignored to reduce the computational complexity of the extraction process. An algorithm with linear time complexity is proposed to merge those substrate contacts exhibiting a voltage difference smaller than a specified value, identifying a voltage domain. An equivalent contact is placed at the geometric mean of the merged contacts, ignoring all of the remaining ports such as the source/drain junctions of the devices. The ground network impedance is updated for each merged contact based on the proposed algorithm to maintain sufficient accuracy of the noise voltage. The substrate with reduced input ports is extracted using an existing extraction tool to analyze the noise at the sense node. As compared to the full extraction of an aggressor circuit, the methodology achieves a reduction of more than four orders of magnitude in the number of extracted substrate resistors with a peak-to-peak error of 24%.

Dual-polarized slot-coupled planar antenna with wide bandwidth

A new dual-polarized slot-coupled microstrip patch antenna is presented, which can achieve high-isolation, low cross-polarization levels, a wide bandwidth, and low backward radiation levels. The coupling slot is an H-shaped slot. For wide bandwidth and easy integration with active circuits, it uses slot-coupled stacked microstrip patches. The theoretical analysis is based on the finite-difference time-domain (FDTD) method. First, a parametric study on the input impedance of the antenna with a single input port is presented. Based on the results, a dual-polarized microstrip antenna is designed, fabricated, and then measured. The measured return loss exhibits an impedance bandwidth of over 20.9% and the isolation between two polarization ports is better than 36 dB over the bandwidth. The cross-polarization levels in both E and H planes are better than 22 dB. The front-to-back ratio of the antenna radiation pattern is better than 21 dB. Both theoretical and experimental results of return loss, isolation, and radiation patterns are presented and discussed.

A time A‐D converter LSI for accurate measurement of multitime‐interval by digital processing

AbstractThe authors previously have reported on the “ring gate delay” system which digitizes the infinitesimal time interval with the delay time of the inverter as the resolution, without using the high‐speed reference clock [1]. A problem then is the improvement of the accuracy since the delay time of the inverter depends on various conditions such as the ambient temperature, the supply voltage, and the fabrication condition. To remedy this point, an LSI is constructed and the delay time of the original circuit is monitored continuously using the quartz oscillation clock of a relatively low frequency as the reference, and the time to be measured is digitized with a high accuracy based on the delay time. In this system, it is not necessary to control the delay time, which makes it possible to utilize the shortest delay time.By a single measurement process using a single input port, up to four pulses can be measured consecutively. If the pulse interval to be measured in less than the specified time, the pulses are combined into a single pulse and an incorrect operation is prevented.In this study, a sample device is constructed by a 1.5‐μm CMOS process. The measurement range of 2200 ns (12 bit) with the time resolution 0.5 ns is achieved using the supply voltage of 5 V. The minimum pulse interval that can be measured is 55 ns (at 25°C). The reference clock used is 2 MHz. The number of transistors is 15, 000 and the chip size is 3.5 mm × 3.8 mm. The constructed LSI is composed totally of digital circuits. The operation is robust against the environmental condition, and a stable operation is realized for the ambient temperature of −35 to 140°C.

A two-photon interference experiment using type II optical parametric down conversion

A pair of orthogonally polarized light quanta, produced from type II parametric down conversion, is injected into a single input port of a beamsplitter and detected coincidently by two detectors placed in the two output ports of the beamsplitter. With the help of a set of crystal quartz plates, a Pockel's cell and two linear polarizers, the coincidence counting rate exhibits interference modulation of the pump frequency with 88% visibility when manipulating the voltage across the Pockel's cell, regardless of the optical delay (which is much greater than the coherence length) and the mutual incoherence. This two-photon interference effect is responsible by a nonclassical two-photon state which is entangled both in spin and in space-time.

Precision Phase Adjustment of a Linear Accelerator High Power Waveguide Feed Network

Each klystron of the SLAC accelerator feeds four consecutive 10-foot accelerator sections through approximately 25 feet of earth shielding. The high power waveguide network which divides and guides the power to the four sections is adjusted so that the rf waves traveling within the accelerator sections are, at the end of each section, phased within ± two degrees of an ideal wave traveling at the velocity of light. A modulated reflection technique is used to compare the electrical phase length from a single input port through the four arms of the network during adjustment. The inclusion of the previously tuned accelerator sections in the network allows the total phase error to be minimized if careful control is exercised over the section terperatures. The measuring system, the reflection modulators, and the possible errors involved are discussed.