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The paper presents a new signal generator for charge-pumping. Modular structure of the generator is discussed with special emphasis on signal-generation module consisting of five independent signal channels. Digital signal synthesis is chosen to minimize inaccuracies. Noise analysis is performed to demonstrate the validity of the design of signal channel. Calibration procedure is also discussed.

The arbitrary waveform generator is characterised by its flexible signal generation, high frequency resolution and rapid frequency switching speed and is wildly used in fields like communication, radar systems, quantum control, astronautics and biomedicine.With continuous development of technology, higher requirements are placed on to the arbitrary waveform generator. Sampling rate determines the bandwidth of the output signal, spurious-free dynamic range determines the quality of generated signal. Due to above, these two indicators’ improvement is vital. However, the existing waveform generation methods cannot generate signals with quality good enough due to their technical limitations, and in order to realize a high system sampling rate, to accomplish waveform generation process in FPGA, multipath parallel structure is needed. Therefore, we proposed a parallel waveform synthesis structure based on digital resampling, which fixed the problems existing in the current methods effectively and achieved a high sampling rate as well as high quality arbitrary waveform synthesis. We also built up an experimental test bench to validate the proposed structure.

We report here on the implementation of arbitrary waveform generation (AWG) capabilities at ∼200GHz into an Electron Paramagnetic Resonance (EPR) and Dynamic Nuclear Polarization (DNP) instrument platform operating at 7T. This is achieved with the integration of a 1GHz, 2 channel, digital to analog converter (DAC) board that enables the generation of coherent arbitrary waveforms at Ku-band frequencies with 1ns resolution into an existing architecture of a solid state amplifier multiplier chain (AMC). This allows for the generation of arbitrary phase- and amplitude-modulated waveforms at 200GHz with >150mW power. We find that the non-linearity of the AMC poses significant difficulties in generating amplitude-modulated pulses at 200GHz. We demonstrate that in the power-limited regime of ω110MHz) spin manipulation in incoherent (inversion), as well as coherent (echo formation) experiments. Highlights include the improvement by one order of magnitude in inversion bandwidth compared to that of conventional rectangular pulses, as well as a factor of two in improvement in the refocused echo intensity at 200GHz.

This article presents a low-cost circuit that generates narrow pulses with programmable waveform, amplitude, and position based on the spectrum stitching method. Specifically in this article, narrow pulses are generated through stitching the spectra of five subsignals, and the subsignals are generated by three regular arbitrary waveform generators with a bandwidth of 200 MHz. The experimental results of pulse generation with various waveforms, amplitude profiles, and position profiles are demonstrated. The pulses demonstrated in this article have a pulse width between 2 and 4 ns, with spectral coverage of about 500 MHz, which is well beyond the capacity of each of the three arbitrary waveform generators used in this work. The experimental results of this article indicate that the spectrum stitching technique has excellent potential to increase the effective bandwidth of arbitrary waveform generators using low-cost circuits. [ABSTRACT FROM AUTHOR]

The arbitrary waveform generator is now commonly used to generate waveforms in many fields. The Nyquist sampling theorem only provides an open interval for the sampling rate selection, but how to determine a specific sampling rate within this open interval has not been discussed. In practice, the sample rate conversion is adopted to convert the arbitrarily selected sample rate to a safe one which keeps the mirror frequency out of a fixed passband of an anti-aliasing filter in an arbitrary waveform generator whose sample rate is variable. To select a safe sample rate with low computational cost and memory requirements for conversion, an algorithm, with fractional sample rate conversion in mind, is proposed in this paper to guarantee the safety of the target sample rate and the bound of resource cost. The experimental results show that not only the computational cost and memory requirements of sampling rate conversion but also the frequency stability and harmonics of the generated signal in the proposed algorithm overcome the method that arbitrary converts the sampling rate to a fixed maximum one.

A new method for high-speed photonic arbitrary waveform generation using optical sinc-pulse sequences and Mach-Zehnder modulators is presented, enabling a three- to four-fold increase in sampling rate compared to the bandwidth of the used modulator for generating the pulses and an $N$ -fold increase compared to the bandwidth of the incorporated electronics, with $N$ as the number of parallel branches. Proof of concept experimental results, using conventional off-the-shelf fiber components have been presented in this study. Due to its simplicity and the possibility to achieve high sampling rates with low bandwidth photonic and electronic equipment, this method is beneficial for integration on a silicon photonics platform. [ABSTRACT FROM AUTHOR]

In this article, a high‐frequency arbitrary waveform generator (AWG) based on Fourier synthesis theory is presented. A key element consists of a nonlinear transmission line (NLTL) that acts as a harmonic generator for large signals and as a phase shifter for small signals. The harmonics generated by the NLTL are separated into four channels using power dividers and each harmonic is bandpass filtered in each channel. The phase and the amplitude are then modulated in each channel by an NLTL phase shifter and a voltage variable attenuator. Finally, vector modulated signals from each channel are combined in Wilkinson power combiners to form any waveform shape. We used 0.5 GHz as a master signal and synthesized waveforms using all four channels. [ABSTRACT FROM AUTHOR]

The advent of fast arbitrary waveform generators in the sub-nanosecond time regime recently enabled new experimental developments in the field of pulsed EPR. In this article, the new possibilities of such fast phase/amplitude modulated microwave pulses are shortly described with respect to applications in pulsed dipolar spectroscopy. Some of the specific challenges of an accurate creation of such pulses in the field of EPR are outlined. Finally, a short outlook of potential applications is given and some specific experimental conditions are discussed, where shaped pulses might have an especially important impact in the future. [ABSTRACT FROM AUTHOR]

• Bump-shaped pulses suppress transients in quantum-limited ESR spectroscopy at 10 mK. • Bump-shaped pulses enable driving spins with a bandwidth larger than the cavity. • Bump-shaped pulses increase the Signal-to-Noise Ratio. • Bump-shaped pulses enable CPMG sequences with short inter-pulse delay. In high sensitivity inductive electron spin resonance spectroscopy, superconducting microwave resonators with large quality factors are employed. While they enhance the sensitivity, they also distort considerably the shape of the applied rectangular microwave control pulses, which limits the degree of control over the spin ensemble. Here, we employ shaped microwave pulses compensating the signal distortion to drive the spins faster than the resonator bandwidth. This translates into a shorter echo, with enhanced signal-to-noise ratio. The shaped pulses are also useful to minimize the dead-time of our spectrometer, which allows to reduce the wait time between successive drive pulses. [ABSTRACT FROM AUTHOR]

The DEER (double electron-electron resonance, also called PELDOR) experiment, which probes the dipolar interaction between two spins and thus reveals distance information, is an important tool for structural studies. In recent years, shaped pump pulses have become a valuable addition to the DEER experiment. Shaped pulses offer an increased excitation bandwidth and the possibility to precisely adjust pulse parameters, which is beneficial especially for demanding biological samples. We have noticed that on our home built W-band spectrometer, the dead-time free 4-pulse DEER sequence with chirped pump pulses suffers from distortions at the end of the DEER trace. Although minor, these are crucial for Gd(III)-Gd(III) DEER where the modulation depth is on the order of a few percent. Here we present a modified DEER sequence--referred to as reversed DEER (rDEER)--that circumvents the coherence pathway which gives rise to the distortion. We compare the rDEER (with two chirped pump pulses) performance values to regular 4-pulse DEER with one monochromatic as well as two chirped pulses and investigate the source of the distortion. We demonstrate the applicability and effectivity of rDEER on three systems, ubiquitin labeled with Gd(III)-DOTA-maleimide (DOTA, 1,4,7,10-Tetraazacyclododecane-1,4,7,10-tetraacetic acid) or with Gd(III)-DO3A (DO3A, 1,4,7,10-Tetraazacyclododecane-1,4,7-triyl) triacetic acid) and the multidrug transporterMdfA, labeled with a Gd(III)-C2 tag, and report an increase in the signal-to-noise ratio in the range of 3 to 7 when comparing the rDEER with two chirped pump pulses to standard 4-pulse DEER. [ABSTRACT FROM AUTHOR]

This paper demonstrates a phase switching algorithm for Interpolating Digital-to-Analog Converter (DAC) based Arbitrary Waveform Generator (AWG) that resides in Automated Test Equipment (ATE) to test semiconductor devices. This confirms a previous exercise that was made by experiment with different Intermodulation Distortion (IMD) suppression techniques and starting phase shifts to suppress IMD tones of the AWG with the interpolating DAC. We show that the poor performance of the AWG can be improved by using the phase switching algorithm over the installed base of a company’s tester platform. It is also shown that the IMD performance of AWGs across a company’s tester installed base can be equalized, and how it can be achieved using the phase switching technique. We describe how the IMD specifications of the instrument are much worse than those actually measured, and by using phase switching, better performance can be achieved than what would be possible under normal conditions. We present how this technique allows the use of a low-cost tester resource to test IMD products of such as communication application ADCs with a higher dynamic range than what was previously possible. [ABSTRACT FROM AUTHOR]

We present a 34 GHz continuous wave (CW)/pulsed electron paramagnetic resonance (EPR) spectrometer capable of pulse-shaping that is based on a versatile microwave bridge design. The bridge radio frequency (RF)-in/RF-out design (500 MHz to 1 GHz input/output passband, 500 MHz instantaneous input/output bandwidth) creates a flexible platform with which to compare a variety of excitation and detection methods utilizing commercially available equipment external to the bridge. We use three sources of RF input to implement typical functions associated with CW and pulse EPR spectroscopic measurements. The bridge output is processed via high speed digitizer and an in-phase/quadrature (I/Q) demodulator for pulsed work or sent to a wideband, high dynamic range log detector for CW. Combining this bridge with additional commercial hardware and new acquisition and control electronics, we have designed and constructed an adaptable EPR spectrometer that builds upon previous work in the literature and is functionally comparable to other available systems. [ABSTRACT FROM AUTHOR]

The DEER (double electron-electron resonance, also called PELDOR) experiment, which probes the dipolar interaction between two spins and thus reveals distance information, is an important tool for structural studies. In recent years, shaped pump pulses have become a valuable addition to the DEER experiment. Shaped pulses offer an increased excitation bandwidth and the possibility to precisely adjust pulse parameters, which is beneficial especially for demanding biological samples. We have noticed that on our home built W-band spectrometer, the dead-time free 4-pulse DEER sequence with chirped pump pulses suffers from distortions at the end of the DEER trace. Although minor, these are crucial for Gd(III)-Gd(III) DEER where the modulation depth is on the order of a few percent. Here we present a modified DEER sequence—referred to as reversed DEER (rDEER)—that circumvents the coherence pathway which gives rise to the distortion. We compare the rDEER (with two chirped pump pulses) performance values to regular 4-pulse DEER with one monochromatic as well as two chirped pulses and investigate the source of the distortion. We demonstrate the applicability and effectivity of rDEER on three systems, ubiquitin labeled with Gd(III)-DOTA-maleimide (DOTA, 1,4,7,10-Tetraazacyclododecane-1,4,7,10-tetraacetic acid) or with Gd(III)-DO3A (DO3A, 1,4,7,10-Tetraazacyclododecane-1,4,7-triyl) triacetic acid) and the multidrug transporter MdfA, labeled with a Gd(III)-C2 tag, and report an increase in the signal-to-noise ratio in the range of 3 to 7 when comparing the rDEER with two chirped pump pulses to standard 4-pulse DEER.

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Chirp and shaped pulses have been recently shown to be highly advantageous for improving sensitivity in DEER (double electron–electron resonance, also called PELDOR) measurements due to their large excitation bandwidth. The implementation of such pulses for pulse EPR has become feasible due to the availability of arbitrary waveform generators (AWG) with high sampling rates to support pulse shaping for pulses with tens of nanoseconds duration. Here we present a setup for obtaining chirp pulses on our home-built W-band (95 GHz) spectrometer and demonstrate its performance on Gd(III)-Gd(III) and nitroxide-nitroxide DEER measurements. We carried out an extensive optimization procedure on two model systems, Gd(III)-PyMTA–spacer–Gd(III)-PyMTA (Gd-PyMTA ruler; zero-field splitting parameter (ZFS) D ∼ 1150 MHz) as well as nitroxide–spacer–nitroxide (nitroxide ruler) to evaluate the applicability of shaped pulses to Gd(III) complexes and nitroxides, which are two important classes of spin labels used in modern DEER/EPR experiments. We applied our findings to ubiquitin, doubly labeled with Gd-DOTA-monoamide ( D ∼ 550 MHz) as a model for a system with a small ZFS. Our experiments were focused on the questions (i) what are the best conditions for positioning of the detection frequency, (ii) which pump pulse parameters (bandwidth, positioning in the spectrum, length) yield the best signal-to-noise ratio (SNR) improvements when compared to classical DEER, and (iii) how do the sample’s spectral parameters influence the experiment. For the nitroxide ruler, we report an improvement of up to 1.9 in total SNR, while for the Gd-PyMTA ruler the improvement was 3.1–3.4 and for Gd-DOTA-monoamide labeled ubiquitin it was a factor of 1.8. Whereas for the Gd-PyMTA ruler the two setups pump on maximum and observe on maximum gave about the same improvement, for Gd-DOTA-monoamide a significant difference was found. In general the choice of the best set of parameters depends on the D parameter of the Gd(III) complex. [ABSTRACT FROM AUTHOR]

In this paper, we describe how a phase switching technique is used to control the harmonic contents of a generated sinusoidal signal using digital signal processing techniques. We will describe how this technique equalizes the harmonic performance of arbitrary waveform generators installed in a large scale integration test system, allowing extended performance testing of the total harmonic distortion of an analog-to-digital converter that ordinarily would be possible only using more advanced test equipment. Once a device has been characterized and correlated to the bench, a test engineer is required to release the product into production. One of the major issues surrounding this exercise is the difference in the obtained results between testers of the same manufacture for parameters sensitive to harmonics, noise, and spurious components such as total harmonic distortion. By using the techniques developed in this paper, the user will be able to deploy an academic solution to an industrial problem and extend the range of test equipment that ordinarily would need to be discarded for such test requirements. We will then show the gauge repeatability and reproducibility between two testers of the same manufacture, and how using the described technique produces a better correlation, thus allowing less stringent guard-bands to guarantee the performance of those devices that have performance criteria close to the device specification. This work also goes some way to proving previous papers' works on distortion shaping testing to enhance the spectral performance of arbitrary waveform generators. [ABSTRACT FROM AUTHOR]

We report here on the implementation of arbitrary waveform generation (AWG) capabilities at ∼200 GHz into an Electron Paramagnetic Resonance (EPR) and Dynamic Nuclear Polarization (DNP) instrument platform operating at 7 T. This is achieved with the integration of a 1 GHz, 2 channel, digital to analog converter (DAC) board that enables the generation of coherent arbitrary waveforms at K u -band frequencies with 1 ns resolution into an existing architecture of a solid state amplifier multiplier chain (AMC). This allows for the generation of arbitrary phase- and amplitude-modulated waveforms at 200 GHz with >150 mW power. We find that the non-linearity of the AMC poses significant difficulties in generating amplitude-modulated pulses at 200 GHz. We demonstrate that in the power-limited regime of ω 1 < 1 MHz phase-modulated pulses were sufficient to achieve significant improvements in broadband (>10 MHz) spin manipulation in incoherent (inversion), as well as coherent (echo formation) experiments. Highlights include the improvement by one order of magnitude in inversion bandwidth compared to that of conventional rectangular pulses, as well as a factor of two in improvement in the refocused echo intensity at 200 GHz. [ABSTRACT FROM AUTHOR]

Digital electronic technology experiment is one of the specialized courses for the student majoring in electronics or related. The arbitrary waveform generator based on DDS is used to the digital electronic technology comprehensive virtual simulation experiment. This teaching case covers almost all core knowledge in the theory of digital electronic technology course, and has characteristic of strong comprehensive. It is convenient for students to master theoretical knowledge fragmentation in the course to build into a relatively complete knowledge system. Experiment results such as sine wave, rectangular wave, triangle wave, arbitrary wave and Lissajous figures can be observed through the oscilloscope. The students ’ interests in learning are stimulated due to high presentation of experiment results. Practice shows that, comprehensive virtual simulation case can improve the students ? ability to design complex digital circuit system. It can also cultivate the students ’ ability of practical innovation and engineering application. It achieved good teaching effect, and was beneficial to the improvement of teaching level. [ABSTRACT FROM AUTHOR]

A low-field nuclear magnetic resonance ( NMR) instrument is an important tool for investigating a wide variety of samples under different conditions. In this paper, we describe a system constructed primarily with commercially available hardware and control software, capable of single-pulse NMR experiments. Details of the construction of the main B0 magnet are also included. The operating frequency for demonstration is 460 kHz (10 mT), however, the range of the hardware spans 700 Hz (16 μT) to 25 MHz (0.6 T). Tip angle optimizations are used to find the most narrow usable pulse width for this configuration, and the T1 of water is measured by single-pulse-saturation-recovery ( SPSR) to demonstrate the potential for this system as a relaxometer. Discussions of resonator construction and efficiency, power requirements and programming strategies that would increase the utility of this system are also included. Construction of any low-field NMR system will depend on experimental interests, budget and engineering resources. A survey of other low-field NMR systems from the literature is included to aid the novice or experienced magnetic resonance scientist in consideration of how a low-field spectrometer could be constructed and used in the lab. [ABSTRACT FROM AUTHOR]