Analysis of pseudo-interleaving AWG

With the development of electronic and information technology, the signal generator has been widely used in various fields of electronic technology. And the requirement of its performance is increasingly more and more superior, such as adjustable frequency and range, high frequency stability, fast conversion speed, etc. Meanwhile, Some uncommonly special waveforms are needed in some special environment, for example a waveform of 1/(T-t) form used in quantum random number generator. Therefore high-speed and stability arbitrary waveform generator have great significance for the practical application of scientific research. In this paper, the design of the arbitrary waveform generator is based on a FPGA chip: XC6SLX75T, using the DDS technology and a high-speed DAC, the digital sampling frequency is up to 1GHz.

The paper describes a channel simulator especially suited for simulating transmissions over satellites. The increasingly large instantaneous bandwidths of satellite transmission systems make it challenging to perform a digital channel simulation in the lab using standard equipment, as dynamic range and bandwidth are linked and the available data converter technology and feasible clock rates for digital processing impose a certain limit, which is typically lower than the feasible bandwidth of an analogue transponder on a high operating frequency. The paper describes the architecture of a digital channel simulator, which allows combining of multiple signal processor cards for parallel processing to a signal bandwidth which exceeds the bandwidth of a single card. By cascading up to seven processor boards the channel simulator can simulate a bandwidth of up to 700 MHz. In case the transponder bandwidth to be simulated is less than the full bandwidth of the simulator, the total bandwidth can be divided up into up to three sub-bands which operate independently The propagation effects and effects of the satellite transponder itself are simulated for each sub-band. To test the behaviour of the system under interference conditions, Arbitrary Waveform Generators allow insertion of multiple interference signals with configurable bandwidths and sampling rates. A shaped noise source allows the user to simulate the presence of in-band and out-of-band interferers in each sub-band. Phase noise is implemented by a multiplication with ejphi(t) for each sub-band. Both a memoryless non-linearity is simulated and an output filter can be configured for each sub-band. Additive white Gaussian noise may be added with variable noise density. Large scale and small scale fading can be simulated by either streaming complex fading multiplication factors from hard disk or using integrated channel models. For automated setups, the channel simulator can be fully remote controlled.

The linear frequency swept light source is a critical device for several sensing applications, including FMCW LiDAR, with which the maximum sensing distance is determined by the coherence length of the light source and the spatial resolution is limited by the frequency scan nonlinearity. Here, we report what we believe to be a novel approach to generate highly coherent optical linear frequency sweeps (LFS) with a Fourier domain mode-locked (FDML) opto-electronic oscillator (OEO) deploying carrier suppressed single sideband (CS-SSB) modulation enabled by a dual-parallel Mach-Zehnder modulator (DP-MZM), with the coherence length determined by the fixed frequency laser used in the OEO, without the need of an expensive high-speed arbitrary waveform generator (AWG). Concurrently, a radio frequency (RF) LFS synchronized with the optical LFS is also generated with the FDML OEO. We obtained a nearly ideal optical LFS around 1550 nm with a side-mode suppression ratio of 27.4 dB, by controlling the bias point and the RF power feeding back to the DP-MZM in the OEO loop. The resulting dual optical and RF LFS' achieved a chirp rate of 27.27 MHz/µs and a frequency tuning range of 0.6 GHz, which can be extended to 142 MHz/µs and 2.0 GHz, respectively by reducing the size of the tunable ring filter circuit inside the OEO loop. By using pre-distortion method, the residual nonlinearity is reduced to 1.9881 × 10-5, and the root mean square (RMS) value of the frequency swept nonlinearity is less than 0.764 MHz. Our dual optical and RF LFS generation with a CS-SSB FDML-OEO has the advantages of long coherence length, high tuning speed, excellent frequency tuning linearity and repeatability, and potentially low cost, which can be used to make a dual optical and RF FMCW ranging system (LiDAR and RADAR) and are attractive for many applications, such as 3D sensing and autonomous driving, as well as optical frequency domain reflectometer (OFDR), and other applications requiring fast and reliable linear frequency sweeps in either optical and RF domains.

Benefitting from a large bandwidth and compact configuration, a time-domain pulse-shaping (TPS) system provides possibilities for generating broadband radio frequency (RF) arbitrary waveforms based on the Fourier transform relationship between the input–output waveform pair. However, limited by the relatively low sampling rate and bit resolution of an electronic arbitrary-waveform generator (EAWG), the diversity and fidelity of the output waveform as well as its reconfiguration rate are constrained. To remove the EAWG’s limitation and realize dynamic real-time reconfiguration of RF waveforms, we propose and demonstrate a novel approach of RF arbitrary-waveform generation based on an improved TPS system with an integrated dual parallel Mach–Zehnder modulator (DPMZM) and multi-tone inputs. By appropriately adjusting the DC bias voltages of DPMZM and the power values, as well as the center frequencies of the multi-tone inputs, any desired RF arbitrary waveform can be generated and reconfigured in real time. Proof-of-concept experiments on the generation of different user-defined waveforms with a sampling rate up to 27 GSa/s have been successfully carried out. Furthermore, the impact of modulation modes and higher-order dispersion on waveform fidelity is also discussed in detail.

The Arbitrary Waveform Generator (AWG) is an important instrument that is widely used in automatic test equipment, radar system, and other fields for generating complex signals. The increasing demand for waveform's complexity is consisted of repeatable segments and advanced-segments, where each segment or segments group could be repeated multiple times. Those requirements make the existing design, implemented by an address generator, complex. The software defined technology can separate the instruction sequence processing from the Data plane to the Controller where the complex logic is defined by software, which lead to a simplified data plane. This paper proposes a design that will generate complex arbitrary waveform by decoupling the waveform composing logic in address generator out from the data plane as an instruction controller. The controller support instruction sequence defined by segment and a jump instruction, which can implement the repeatable segments and the advanced-segments, respectively. We built an AWG based on this design and made the implementation in a field programmable gate array with a required clock frequency of 125 MHz. The design has a high sampling rate of 4 gigabit samples per second and can generate complex arbitrary waveform consisting of repeatable segments and advanced-segments.

We propose and experimentally demonstrate a photonic approach to generating a chirped microwave waveform with a large time-bandwidth product (TBWP) based on self-heterodyne technique. We use the chirp characteristic of a distributed feedback (DFB) laser (LD) to generate a frequency-modulated optical pulse, to directly modulate the LD using an injection current with a parabolic current shape that is controlled by a microwave waveform generated by a low-speed arbitrary waveform generator (AWG). The frequency-modulated optical waveform is then sent to an unbalanced Mach-Zehnder interferometer (MZI) to get two time-delayed replicas of the input waveform. A chirped microwave waveform is then generated by beating the time-delayed waveforms at a high speed photodetector (PD). The proposed technique is theoretically studied and experimentally demonstrated. Using an AWG with sampling rate of 100 MS/s and an MZI with an arm length difference of 144 m, we experimentally generate a linearly chirped microwave waveform with a long time duration of 1 μs and a bandwidth of 4.2 GHz, with a TBWP of 4200.

Focus on test and measurement

Remote monitoring of patients using wireless capabilities increasingly plays an important role in healthcare and the communication with implanted medical devices (IMDs). In the case of IMDs, transmission is characterized by low peak power and low duty cycle to reduce the potential for adverse bio-effects. Currently, most IMDs use radio-frequency (RF) electromagnetic waves to communicate through the body. The corresponding maximum bandwidth allowed is 300 kHz as regulated by the FCC, which inherently limits the communication rates of these devices (limiting to maximum data rates of 50 kb/s). Beyond bandwidth restrictions, the main limitation for using RF electromagnetic waves in the body is loss of signal because of attenuation in the body. For these reasons the output power of RF devices is limited to 25 µW, which also limits data rates to 50 kb/s. In this study, an ultrasonic communication channel is explored for IMD communications as an alternative to EM transmission. We demonstrate the ability to communicate through tissues using the ultrasonic communications channel while maintaining data rates necessary for streaming of high definition video. In our experiments we used a matched pair of 5-MHz f/3 single-element transducers operating in a pitch-catch configuration in a tank of degassed water. Between the transducers was placed either a slab of pork tenderloin or a slab of beef liver (each more than 2 cm thick). Quadrature amplitude modulation (QAM) and quadrature phase shift keying (QPSK) signals were coded for transmission into the transmitting transducer using an arbitrary waveform generator. Signals were transmitted and captured by sending 10 snapshots (packets) of 50,000 samples (10,000 training / 40,000 decision-directed) using a fractionally-spaced (2 samples per symbol) decision feedback equalizer with up to 40 taps in the feed forward section, and 40 taps in the feedback section. Signals were successfully decoded through the samples using QPSK, 16QAM and 64QAM codes with bit error rates of (BER) < 1e-4. A maximum data rate of 30 Mbps using the 64QAM was achieved through both the pork tenderloin and the beef livers. These experiments successfully demonstrate that communications through the ultrasonic channel can provide data rates capable of streaming high definition video.

Today a growing number of applications in design engineering, production and environmental testing, and system service require specific analog waveforms and digital patterns. Such requirements are neither satisfactorily nor easily met by the use of standard function or single purpose, custom generators. Traditional methods of waveform generation suffer from undesirable complexity or mediocre performance and are otherwise limited. For the majority of arbitrary waveform generation applications, including medical engineering, modal analysis and electronic engineering, direct digital synthesis techniques are satisfactory. Direct digital synthesis, based generally on periodic retrieval of predetermined amplitude values, may be used to 2 generate such waveforms. Within the limits imposed by the system's maximum sample rate and the Nyquist criteria, any waveform may be produced using these techniques. The objective of this inquiry, within a particular set of constraints, is to extend the cost/performance envelope of direct digital synthesis techniques for the generation of arbitrary waveforms. Performance is enhanced, particularly in the areas of output bandwidth and signal purity.

This paper presents the evolution of LNE’s impedance bridge (Wheatstone bridge) used to calibrate AC resistors defined in the two terminal-pair configuration. A new automated Wheatstone bridge, based on four resistances, was developed to operate in the full complex plane for resistances ranging from 400 Ω to 2 MΩ and for frequencies up to 20 kHz. A commercial dual precision arbitrary waveform generator supplies the bridge and PXI modules achieve the balance. Phase and frequency synchronization solutions between the arbitrary waveform generator source and the PXI modules were used. The choice of these instruments allows the bridge to be easily automated and to benefit from recent progress in the development of digital-analog converters, in particular those with high frequency sampling rates and resolution. The bridge is mainly dedicated to realize the periodic calibration of LNE’s standard resistors, used for routine customer calibrations. The traceability of LNE’s standard resistors is ensured, firstly, by the calibration of a 1 kΩ resistor by comparison to a calculable resistor up to 20 kHz. Then, this resistor is used as a reference element to ensure the traceability of all LNE’s standard resistors using the new bridge. The validation was done by comparing the results obtained, for some resistors with very low drift, with those obtained during calibrations performed in 1983, 1995 and 2009. For resistors of 1 kΩ in a 1:1 ratio, the expanded uncertainty of series resistance variation and argument are, respectively, less than 1.3 µΩ Ω−1 (k = 1) and 1.2 µrad (k = 1), up to 20 kHz.

This article describes the feasibility of signal generation by employing the System on Chip (SoC) ZedBoard™ platform to produce intensity modulation in Time Division Multiplexing-fiber Bragg grating sensor. SoC has the capability to reduce complexity and increase the flexibility in the design of digital instruments. Experimental results show that the system can regulate the period and Duty cycle for two output waveforms and frequency. The employment of SoC in the TDM-FBG sensor system provides overall performance enhancement over the conventional single pulse, since it shows a rapid response time of 3.4 ns compared to 8.2 ns when Arbitrary Waveform Generator is used. Further enhancement on accuracy can be done by using a high-speed digital-analog converter board with a higher sampling rate.

Partial discharge (PD) phenomenon in high-voltage (HV) apparatus is a warning symptom of insulation degradation that can eventually lead to equipment breakdown. The ultra-high frequency (UHF) or electromagnetic method has been widely adopted to monitor the insulation condition of HV power equipment such as power transformers. To detect PD occurrence on HV power transformers, the UHF method is preferable due to its high immunity to external interferences such as background noise and electromagnetic interferences from telecommunication. The UHF antennas are used in the UHF method to detect the electromagnetic waves emitted by PD events inside the power transformer tank. Many studies about the design of UHF antennas to detect PD on power transformers have been conducted previously. However, these UHF sensors are still facing noise disturbances especially for on-line partial discharge measurement, in presence of high noise levels. To address interference issues affecting the UHF sensor sensitivity, this paper presents a novel UHF PD sensor called rectangular microstrip patch antenna or simply patch antenna. This type of antenna has a simple structure, low cost for fabrication, and ultra-wideband (UWB) frequency enabling it to detect PD signals in a wide frequency range within the UHF range (300MHz-3GHZ). To design, simulate and optimize the UHF antenna, the HFSS software was used. The FR4-epoxy substrate having a thickness of 1.6mm, and a dielectric constant of 4.4 was used to design and simulate this rectangular patch antenna. The perfect electric conductor (PEC) was used on the rectangular patch, feedline, and ground plane of the designed patch antenna. The proposed antenna has a low reflection coefficient, low VSWR < 2, a wide bandwidth, as suitable gain, and directivity enabling this antenna to be a suitable and promising sensor for PD detection on power transformers.

The problem of interpreting the results of software performance analysis is very critical. Software developers expect feedback in terms of architectural design alternatives (e.g., re-deploy a component), whereas the results of performance analysis are pure numbers. Support to the interpretation of such results that helps to fill the gap between numbers and software alternatives is still lacking. Performance antipatterns can play a key role in the search of performance problems and in the formulation of their solutions. In this poster, we introduce a process to elaborate the analysis results and to score performance requirements, model entities and guilty performance antipatterns.

Currently, almost all hard disk drives (HDDs) have adopted a loading/unloading mechanism that increases their recording capacity and improves their reliability. However, these mechanisms still create a few scratches or defects in the loading/unloading zone. Slipping at the dimple–flexure interface was recently reported as one of the causes. In this research, we first analyzed the relative behavior of dimple–flexure based on fretting wear marks. We determined that the dimple–flexure behavior included both slipping and rotating motion simultaneously. We then verified the distinct slipping and rolling phenomenon at the moment of ramp contact using finite-element method (FEM) analysis. An experimental setup was constructed, and an unloading experiment was carried out to obtain the ramp contact characteristics corresponding to various unloading velocities. Based on the verified FEM, the characteristics of dimple–flexure relative behavior were investigated for various suspension design parameters, ramp contact characteristics, and unloading velocities. A higher ramp contact force and shorter contact duration resulted in larger slip displacements and roll angles between the dimple and the flexure. Finally, we analyzed the unloading performance of an HDD for various design parameters using quasi-static approximation while considering the relative behavior between the dimple and flexure. The quasi-static analysis indicated a change of approximately 15 % in the flying height at an unloading velocity of 40 in. per second when the relative motion between the dimple and flexure was considered during the unloading process. Even, slider–disk contact occurred at an unloading velocity of 50 ISP.

Sequential equivalent time sampling (ETS) has been extensively used in data acquisition instruments (e.g., sampling oscilloscopes and time domain reflectometers). A novel step delay method is proposed based on the frequency difference to obtain a higher sampling rate in sequential ETS. It is different from the classic step delay methods and is capable of increasing the sampling rate. The sampling clock and the repetitive signal are taken as examples in this study. The time-frequency conversion relationship indicates that a fine step delay will be generated in the time domain if there is a frequency difference between the two in the frequency domain. The core of the proposed method is the selection of the appropriate frequency difference (step delay) according to the desired equivalent sampling rate. Two experiments were performed to verify the proposed method. The feasibility of the proposed method is verified using a digital storage oscilloscope. Four cases are examined in the experiment, and the final equivalent sampling rate is obtained as 5 PS/s for the equivalent sampling of a 4.999 995GHz (or higher) signal. A data acquisition system with a 10 MS/s real-time sampling rate is designed to verify the feasibility of the proposed method, obtaining a theoretical equivalent sampling rate of 585 GS/s. The theoretical equivalent sampling rate and the examined equivalent sampling rate are consistent. The equivalent sampling waveform and real-time sampling waveform of a 1GHz signal are compared, and the comparison result suggests that the proposed method can acquire more waveform information. The proposed method obtains a high equivalent sampling rate for repetitive signals, and techniques (e.g., oversampling) are given to obtain higher vertical resolution. The proposed method, combined with a sample-and-hold amplifier, can also achieve a higher analog bandwidth.