Additional Delay Line Research Articles

Ultra-Wideband Common-Mode Rejection Structure with Autonomous Phase Balancing for Ultra-High-Speed Digital Transmission.

For ultra-high-speed digital transmission, required by 5G/6G communications, ultra-wideband common-mode rejection (CMR) structures with autonomous phase-balancing capability are proposed. Common-mode noise, caused by phase and amplitude unbalances, is one of the most undesired disturbances affecting modern digital circuits. According to the circuit design guides with a typically used differential line (DL) for high-speed digital transmission, common-mode rejection is achieved using CMR filters, and the unbalanced phase, caused by a length difference between the two signal lines of a DL, is compensated by inserting an additional delay line. However, due to nonlinear phase interactions between the two DLs and unbalanced electromagnetic (EM) interferences, the conventional compensation method is frequency-limited at around 10 GHz. To significantly enhance the common-mode rejection level and extend the phase recovery bandwidth, the proposed CMR structure utilizes a planar balanced line (BL), such as a coplanar stripline (CPS) or a parallel stripline (PSL), along with additional conductor strips arranged laterally near the BL. To demonstrate the performance of the proposed BL-based CMR structures, various types of CMR structures are fabricated, and the measurement results are compared with the 3D EM simulation results. As a result, it is proven that the proposed BL-based CMR structures have the capability to reject the common-mode noise with suppression levels of more than 10 dB and to simultaneously recover the phase balance from near DC to over 40 GHz.

Continuous spatial self-cleaning in GRIN multimode fiber for self-referenced multiplex CARS imaging.

We demonstrate how spatial beam self-cleaning and supercontinuum generation in graded-index multimode optical fibers can be directly applied in multiplex coherent anti-Stokes Raman Scattering (M-CARS) spectroscopy. Although supercontinuum generation causes pump depletion mainly in the center of the beam, the partial recovery of the pump brightness due to self-cleaning may enable self-referenced M-CARS, with no additional delay lines to synchronize pump and Stokes waves. As a proof-of-principle, we report examples of imaging of single chemical compounds and polystyrene beads. The new scheme paves the way towards simpler M-CARS systems based on multimode fiber sources.

Hardware Random Number Generator Using Josephson Oscillation and SFQ Logic Circuits

A hardware random number generator using Josephson oscillation and a few single flux quantum (SFQ) logic gates is presented. The logic circuit of the random number generator consists of one toggle flip flop and one and gate. A prototype random number generator is designed by logic cells based on a 2.5-kA/cm2 Nb/AlOx/Nb integration process. The fundamental operation at a few hundred megahertz of the random number sampling frequency is confirmed by numerical simulation when a DC/SFQ converter is used for generating trigger signals. An additional delay line using an overdamped Josephson transmission line is used for increasing the timing jitter to get random numbers. The delay line makes it possible for the random number generator to operate over 1 GHz. To confirm the fundamental operation of the circuit, a primitive SFQ random number generator is fabricated using the AIST standard process with 2.5-kA/cm2 Nb/AlOx/Nb junctions and the standard logic cell library. A random number generation based on a low-speed functional test is successfully confirmed.

A broadband Faraday fiber-optic current sensor with excess noise compensation

A Faraday fiber-optic current sensor with suppression of excess noise produced by a low-coherent light source is presented. The sensor is designed to detect short current pulses and represents an in-line interferometer with a sensing element based on a spun highly birefringent fiber. To suppress the excess noise, a two-channel light detection scheme without an additional delay line is applied. It is established that bending birefringence induced in the spun fiber wound on a coil limits the noise suppression. To minimize this effect, a new geometry of the sensing coil is used. The proposed sensor exhibits a 5-fold improvement of the signal-to-noise ratio and the same enhancement of the sensitivity to a value of 0.8A in the 3.5 MHz bandwidth. The minimum duration of the measured current pulse is 200 ns.

Young’s Modulus Determination of Polyester and Epoxy by Means of Ultrasonic Pulse Echo Testing

The Young’s modulus or elasticity modulus is material ability to resist elastic deformation when loaded. Thermosetting polymers have a wide range of modulus elasticity values. To determine the elasticity modulus value, materials need to be destructive tested, such as tensile test or bending test. But in industrial field, they avoided destructive test. Theoretically, the modulus of elasticity can also be determined by ultrasonic testing pulse echo method. This method has already applied successfully for metals material. The goal of this research was to evaluate probe used in longitudinal velocity measurement of polyester and epoxy and to determine Young’s Modulus of polyester and epoxy by means ultrasonic pulse echo testing. This method was performed using three longitudinal probes that have different diameters, frequencies, and additional delay line. The specimens were varied with different thicknesses. The ultrasonic pulse echo method uses probe 3 with a diameter of 12.7mm, a frequency of 1.5MHz, and additional delay line is most suitable to measure the longitudinal velocity of polyester and epoxy with thickness of 2.82-36.72 mm. Probe 3 has a smaller diameter and additional delay lines thus eliminating the effect of dead zones. The elastic modulus error of thermoset polymer material through ultrasonic testing of pulse echo method compared to the mechanical modulus of elasticity is still very large, i.e. 102% for epoxy, and 159% for polyester. A large error is caused by attenuation and the use of the elasticity modulus equation from ultrasonic testing that still requires modification.

A Feeding Technique for Wideband CP Patch Antenna Based on 90° Phase Difference Between Tapped Line and Parallel Coupled Line

A feeding technique for wideband circularly polarized (CP) patch antenna based on the 90° phase difference between tapped line and parallel coupled line in a feeding network is proposed. The tapped line and parallel coupled line are equivalently regarded as a direct coupling element with 0° phase delay and a J -inverter coupling element with 90° phase delay, respectively. In design, two identical λ /2 resonators are employed to excite two orthogonal modes for wideband equal magnitude. Meanwhile, the feeding lines are tapped and coupled to the two resonators, and tapped line and coupled line can inherently provide 90° phase difference as demanded for CP radiation with no need for an additional delay line or a phase shifter. The whole structure is modeled as an equivalent three-port network, and the theoretical axial ratio (AR) is calculated with the magnitude and phase of the voltage at the radiation conductance. Since two minima in AR response emerge, this proposed patch antenna can achieve a wide AR bandwidth. The theoretical performance is finally verified by a fabricated CP patch antenna prototype with a profile of 0.042 λ 0, and the 3 dB AR fractional bandwidth is 7.07%.

Analog Predistortion Linearizer With Independently Tunable Gain and Phase Conversions for Ka-Band TWTA

Analog predistortion (APD) is an effective technique to improve the linearity of the traveling-wave tube amplifier (TWTA). This paper presents a novel APD linearizer with independently tunable gain and phase conversions. Based on symmetrical dual-branch vector synthetic topology, which avoids introducing the additional delay line, this linearizer achieves a simple circuit structure. Independent tuning of gain and phase conversions of this linearizer is realized by changing the bias voltages of the two branches. Theoretical analysis and tuning process of this linearizer are discussed in detail. Simulated and measured results are in a good agreement, and both of them verify that this linearizer has the independent tuning ability. Furthermore, a 250-W Ka-band TWTA is linearized by this linearizer, and the measurement results demonstrate the effectiveness of this linearizer in TWTA linearization.

Virtual fine delay line using one-stage inverter delay

A virtual fine delay line (VFDL) using only two ring oscillators and counters can cover a wide frequency operation range clock without adding any additional delay line stage. The proposed ring oscillator can easily make a unit delay as a one-stage inverter. The VFDL achieves fine resolution of less than 60 ps and small circuit area with two clock cycles lock-in time.

Subnanosecond risetime pulse generators

Treats the design of solid-state pulse generators with risetimes less than 100 ps. These generators have been used in time-domain measurements on microwave components and materials to obtain frequency characteristics from time domain waveforms. A brief review of various sources including avalanche transistors, tunnel diodes, and step-recovery diodes (SRD's) is given. The main feature is a description of a 60-ps risetime step generator with modifications for impulse and RF pulse outputs. In the step generator an avalanche transistor driver produces a 30-V step, which is successively sharpened by two SRD's to a 20-V 60-ps risetime step. A trigger signal is provided by the first SRD followed by an internal 70-ns delay so that the faster pulse from the second SRD stage can be displayed on a sampling oscilloscope with no additional delay lines. The basic step can be differentiated to produce a 6-V 60-ps halfwidth impulse or filtered to generate a 1-V 500-ps wide RF burst with principal spectral amplitude in the 9-16 GHz frequency range. These generators provide a larger instantaneous spectral amplitude than the commonly used tunnel diode pulser.