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A pulse 720 MHz EPR imager with a permanent magnet, arbitrary waveform generator based excitation, and detection system operating in the direct sampling and signal down-conversion modes is presented. This flexible instrument allowed testing various acquisition modes and demonstrating its signal to noise ratio advantage over the previously used 250 MHz instrument.

This article mainly focuses on the concept of cognitive radio paradigm in the ultra-wideband 3.1–10.6 GHz and recent trends of various antenna systems required for these applications. This paper also presents the working principle of cognitive radio model and the importance of UWB 3.1–10.6 GHz technology for various wireless communication applications. In the cognitive radio model, ultra-wideband antennas are employed for free channels identification and reconfigurable narrow band antennas for communication. Based on the utilization of different UWB and narrow band antennas, the antennas are divided into four distinct categories. The first category covers individual UWB and narrow band antennas. The second category includes reconfigurable UWB/NB antennas. The third category consists of dual-port integrated UWB and NB antennas. The fourth category comprise of multi-port integrated UWB and NB antennas. So, this paper reports all the four categories of ultra-wideband and frequency reconfigurable narrow band antennas clearly. It also focuses on the recent trends in these antennas. Moreover, it discusses about the comparison study of various antennas and their characteristics. Furthermore, a discussion on hardware working principle and its implementation is presented. The hardware realization is presented using arbitrary waveform generator, real-time signal analyzer, software defined radio platforms, field programmable gate arrays and universal software radio peripheral.

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.

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.

In this paper a digital architecture for generating piecewise-linear arbitrary waveforms is presented. The proposed design is able to generate a piecewise-linear periodic signal by only using a minimum number of input data (breakpoints). The generator circuit implements a hybrid scheme which takes advantage of two methods: the purely piecewise-linear interpolation and the lookup-table structure. From the piecewise-linear method exploits the characteristic of a reduced memory requirement as well as the capability of automatically construct a waveform by repetitive (iterative) function evaluations. From lookup-table makes use of the simplicity in hardware implementation and the higher processing speed. In order to verify the performance of this proposal, three piecewise-linear waveforms have been successfully implemented in a ATMEGA32 microcontroller. Experimental results show a fast execution speed and a reduced memory demand in the proposed circuit realization.

We developed two digital magnetic resonance imaging (MRI) consoles using general-purpose digital instruments and microcontroller boards. The first console consisted of a digital oscilloscope (8-bit resolution, 250-MHz sampling frequency), an arbitrary waveform generator (14-bit resolution, 100-MHz sampling frequency), and three 32-bit microcontroller boards. The second console consisted of a digital oscilloscope (16-bit resolution, 1-GHz sampling frequency) with a built-in waveform generator (14-bit resolution, 200-MHz sampling frequency) and three 32-bit microcontroller boards. MRI experiments were performed using a 1.0-T and 90-mm gap yokeless permanent magnet to evaluate the MRI consoles. Three-dimensional spin-echo and gradient-echo images were successfully acquired using the first and second MRI consoles using an undersampling technique and RF phase correction. We concluded that the digital MRI consoles could be built using general-purpose digital instruments and microcontroller boards at a reduced cost and within a short development time.

To obtain wideband orthogonal waveforms of radar systems with high-range resolution and good correlation properties, this paper proposes two types of orthogonal wideband hybrid-coding waveforms, polyphase discrete frequency (PDF) waveforms and polyphase signed-chirp (PSC) waveforms. Using an intra-pulse hybrid modulation, high-range resolution can be obtained, and good correlation properties between different waveforms are easier to optimize within a larger optimization space. Specifically, good correlation properties of the PDF waveforms are indeed easier to achieve without a loss of range resolution, as occurs with a discrete frequency coding waveform. Compared with polyphase coding waveforms, the signal bandwidth of each PSC waveform is twice as large as that of sub-pulse chirp signals, and superior correlation properties are obtained. Finally, various designed waveforms optimized by the genetic algorithm are provided to demonstrate the effectiveness of these proposed wideband hybrid-coding waveforms.

We present a low cost radio-frequency (RF) generator suitable for experiments with cold atoms. The RF source achieves a sub-hertz frequency with tunable resolution from 0 MHz to 400 MHz and a maximum output power of 33 dBm. Based on a direct digital synthesizer (DDS) chip, we implement a ramping capability for frequency, amplitude and phase. The system can also operate as an arbitrary waveform generator. By measuring the stability in a duration of 600 s, we find the presented device performs comparably as Agilent33522A in terms of short-term stability. Due to its excellent performance, the RF generator has been already applied to cold atom trapping experiments.

In this paper, a dynamic optical arbitrary waveform generator (OAWG) based on cross phase modulation (XPM) is proposed. According to the characteristics of XPM, the nonlinear phase shift of signal can be changed along with the pump power. The amplitude of signal can be changed by controlling the phase shift at one arm of a Mach-Zehnder interferometer (MZI) using XPM effect between signal and pump. Therefore, the phase and amplitude of the optical frequency comb (OFC) can be controlled by two pump arrays. As a result, different kinds of waveforms can be synthesized. Due to the ultrafast response of XPM, the generated waveform could be dynamically updated with an ultrafast frequency. The waveform fidelity is affected by the updating frequency.

We demonstrate a high-spatial-resolution fast Brillouin optical time-domain analysis scheme based on frequency agility and differential double-pulse for distributed dynamic measurement. The frequency-agility probe wave is obtained from the second-order sideband of modulated light by using frequency-agility microwave signal from a wideband arbitrary waveform generator. The differential double-pulse technique is proposed to improve the spatial resolution while keeping the capability of dynamic measurement. In experiment, a spatial resolution of 20 cm is achieved by using a 52/50 ns differential double-pulse, and the distributed vibration measurement is demonstrated over a 50-m Panda fiber with a maximum vibration frequency of up to 50 Hz. With only five averages, the standard deviation of the strain accuracy is of 14 μV.

Evaluation of the electrical stimulation efficiency of various stimulating waveforms is an important issue for efficient neural stimulator design. Concerning the implantable micro devices design, it is also necessary to consider the feasibility of hardware implementation of the desired waveforms. In this paper, the charge, power and energy efficiency of four waveforms (i.e. square, rising ramp, triangular and rising ramp-decaying exponential) in various durations have been simulated and evaluated based on the computational model of the auditory nerve fibers. Moreover, for a fair comparison of their feasibility, a fully integrated current generator circuit has been developed so that the desired stimulating waveforms can be generated. The simulation results show that stimulation with the square waveforms is a proper choice in short and intermediate durations while the rising ramp-decaying exponential or triangular waveforms can be employed for long durations.

A turnkey fiber laser source generating high beam quality pulses with 240 W average power and arbitrary pulse shapes is presented in theory and experiment. It is based on semiconductor laser diode modulated by arbitrary waveform generator as a seed and polarization maintaining (PM) master oscillator power amplifier (MOPA) system to boost the pulse energy. Detailed experimental and theoretical studies are in a very good agreement. The polarization extinction ratio (PER) of system measured at maximum output power is beyond 17 dB with the excellent beam quality factor M 2 of 1.25.

In this paper a fast digital real-time spectrometer was developed for timing and analysis of nuclear pulse signals. The hardware system design and algorithm implementation with field-programming gate array (FPGA) and digital signal processor (DSP) were introduced. The performance of the digital constant fraction discrimination (dCFD) platform was experimentally tested with Agilent 80 MHz function/arbitrary waveform generator and LaCl3:Ce3+ scintillator detector for 22Na positron annihilation gamma spectroscopy. The amplitude and time information of γ photon was online obtained. The energy resolution could be 5.525% and the timing resolution 293.75 ps, the system error estimation of dCFD approach was also studied. The results showed that this spectrometer achieved a timing resolution close to that of traditional CFD timing resolution with a more simplified system structure.

This paper describes algorithms for gener- ating a low-distortion single-tone signal, for testing ADCs, using an arbitrary waveform generator (AWG). The AWG consists of DSP (or waveform memory) and DAC, and the nonlinearity of the DAC generates distortion components. We propose here to use DSP algorithms to precompensate for the distortion. The DSP part of the AWG can interleave multiple signals with the same frequency but different phases at the input to the DAC, in order to precompensate for distor- tion caused by DAC nonlinearity. Theoretical analysis, simulation, and experimental results all demonstrate the effectiveness of this approach.

Optical arbitrary waveform generation will allow waveforms to be synthesized at optical frequencies but with the flexibility currently available at radiofrequencies. This technique is enabled by combining frequency comb technology, which produces trains of optical pulses with a well-defined frequency spectrum, with pulse shaping methods, which are used to transform a train of ultrashort pulses into an arbitrary waveform. To produce a waveform that fills time, the resolution of the shaper must match the repetition rate of the original pulse train, which in turn must have a comb spectrum that is locked to the shaper. Here, we review the current efforts towards achieving optical arbitrary waveform generation and discuss the possible applications of this technology.

We demonstrate a high-spatial-resolution fast Brillouin optical time-domain analysis scheme based on frequency agility and differential double-pulse for distributed dynamic measurement. The frequency-agility probe wave is obtained from the second-order sideband of modulated light by using frequency-agility microwave signal from a wideband arbitrary waveform generator. The differential double-pulse technique is proposed to improve the spatial resolution while keeping the capability of dynamic measurement. In experiment, a spatial resolution of 20 cm is achieved by using a 52/50 ns differential double-pulse, and the distributed vibration measurement is demonstrated over a 50-m Panda fiber with a maximum vibration frequency of up to 50 Hz. With only five averages, the standard deviation of the strain accuracy is of 14 μV.

This paper is to present a systematic performance analysis of asynchronous quaternary direct sequence code division multiple access (DS-CDMA) systems using random signature sequences with arbitrary chip waveforms. The simplified improved Gaussian approximation method for bit error rate computation is extended to include arbitrary time-limited (full response or partial response) or band-limited chip waveforms with arbitrary receiver filters. As a time-limited partial response chip waveform modulation format, the well-known power and spectral efficient "superposed quadrature amplitude modulation" with matched filter or zero-forcing filter is evaluated, and the results show that the optimum zero-forcing filter will yield a performance better than the matched filter counterpart. For band-limited chip waveforms, based on an elementary density function of a second-order polynomial, a class of second-order continuity pulses is proposed for analysis. It is found that all common band-limited pulses are only its special cases. As a member of the class, the widely used frequency domain raised cosine pulse has the worst anti-multiuser-access-interference capability, which has been pointed out in (H. H. Nguyen, Proceedings of IEEE Canadian Conference on Electrical & Computer Engineering, 2002, pp. 1271--1275).

Background In ultrasound imaging systems, the digital transmit beamformer is a critical module that generates accurate control over several transmission parameters. However, such transmit front-end module is not typically accessible to ultrasound researchers. To overcome this difficulty, we have been developing a compact and fully programmable digital transmit system using the pulse-width modulation (PWM) technique for generating simultaneous arbitrary waveforms, specifically designed for research purposes. Methods In this paper we present a reconfigurable arbitrary waveform generator (RAWG) for ultrasound research applications that exploits a high frequency PWM scheme implemented in a low-cost FPGA, taking advantage of its flexibility and parallel processing capability for independent controlling of multiple transmission parameters. The 8-channel platform consists of a FPGA-based development board including an USB 2.0 interface and an arbitrary waveform generator board with eight MD2130 beamformer source drivers for individual control of waveform, amplitude apodization, phase angle and time delay trigger. Results To evaluate the efficiency of our system, we used equivalent RC loads (1 kΩ and 220 pF) to produce arbitrary excitation waveforms with the Gaussian and Tukey profiles. The PWM carrier frequency was set at 160 MHz featuring high resolution while keeping a minimum time delay of 3.125 ns between pulses to enable the acoustic beam to be focused and/or steered electronically. Preliminary experimental results show that the RAWG can produce complex arbitrary pulses with amplitude over 100 Vpp and central frequency up to 20 MHz with satisfactory linearity of the amplitude apodization, as well as focusing phase adjustment capability with angular resolution of 7.5°. Conclusions The initial results of this study showed that the proposed research system is suitable for generating simultaneous arbitrary waveforms, providing extensive user control with direct digital access to the various transmission parameters needed to explore alternative ultrasound transmission techniques.

A wide variety of complex waveforms can be generated by approximating the desired analog waveform from an array of digital values. Some basic properties of these digital approximations are discussed in terms of pulse amplitude modulation and sampling theory. The waveforms are generated by transferring the digital values to a digital-to-analog converter followed by a low-pass filter. This usually requires the dedicated use of a computer. We have built a device, incorporating solid state memory, that can store, time, and transfer previously computed digital values, so that a computer is no longer necessary to generate the waveforms. Specifications of the digital-to-analog converter and appropriate settings of the filter are discussed, along with a simplified procedure for calculating waveforms that have line spectra. An adaptation of this procedure enables the device to be used as a high-speed programmable pure-tone source.

A simple biological signal generator capable of reproducing complex biopotential waveforms is described. It is constructed by a combination of digital and analog circuit components and can be used under different experimental conditions, such as in calibration of biomedical instrumentation systems, or simply as a function generator providing voltage outputs of various waveforms. The biopotential waveform to be generated is sampled at a high frequency and the samples are stored sequentially in a programmable read only memory (PROM). The samples are then fed in the same sequence to a digital-to-analog (D/A) converter and the resulting output is amplified and a DC offset is added. External controls are provided to adjust the DC offset, amplitude and repetition rate of the signal generated. The reproduced voltage signals are stable and superior in quality to those produced by conventional biological signal generators.