A novel direct waveform synthesis technique with carrier frequency programmable

In this paper, we propose a low-cost arbitrary waveform generator to simulate battery voltage transients specified by ISO 16750–2 voltage profiles. The proposed methodology is based on the technique of direct digital synthesis (DDS) implemented in a microcontroller. The proposed approach allows reducing the amount of Flash memory used by the lookup table. The device generates several types of waveforms and uses a sequencer to combine them into the desired voltage profile. For testing purposes, emulations of the variations on the cranking voltage and the superimposed A.C. voltage are used to validate the proposed solution.

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.

Phase to amplitude conversion is an essential part in the technique of direct digital frequency synthesis. A novel theory of phase to amplitude conversion named curve approximation is proposed in this paper to solve the existing problems of present digital frequency synthesizers. It has more advantages over traditional phase to amplitude conversion methods, such as simple hardware circuit, fast conversion speed, low loss and high precision. A mathematical function approximating normalized waveforms is presented in the paper and then is corrected by a small ROM lookup table containing the difference between normalized waveform and curve approximation. It can be seen from MATLAB simulation that the given curve is essentially coincident with the normalized waveform. Frequency synthesizer based on DSP and MCU verifies the feasibility of curve approximation in direct digital frequency synthesis. Experimental result shows that this method has excellent performance.

Long Range(LoRa) Backscattering Communication (BC) not only has the advantages of low cost and low power consumption, but also has a long communication distance. However, the existing LoRa BC scheme is complex and can not be applied to actual engineering. For this purpose, a new LoRa BC method is proposed. A Direct Digital frequency Synthesis (DDS) technique is used to generate a square wave with a linear frequency variation as a LoRa scattering modulation signal. For the first time, the prototype of LoRa BC system based on MCU is demonstrated. Experimental results show that design can successfully realize backscatter communication at any position between the station and the receiver which are 208 meters apart, while being compatible with commodity LoRa chipset. In addition, the method is also applicable to an Application Specific Integrated Circuit (ASIC) design, which enables the LoRa backscattering IC to have higher robustness, lower cost, and lower power consumption.

Standing-wave ultrasonic motors (usm) have the advantages of small volume, light weight, fast response, high-precision position, power-off self-locking, no electromagnetic interference and vacuum adaptability etc. It has broad application prospects in the field of space laser communication. Because the driving force and power of single motor are limited, and in order to meet the requirement of torque margin in engineering applications, ultrasonic motors are usually used in pairs in laser tracking and pointing system. However, due to the preload of the motor, the inconsistency between production and manufacturing, and the matching between the driving circuit and the motor and so on, the resonance frequency among motors varies from hundreds of Hz to several kHz, which makes it difficult to realize synchronous control. In addition, the inherent nonlinear characteristics of piezoelectric ceramic also affect the high-precision control of the ultrasonic motor. In order to further improve the synchronous driving control performance of parallel motor, an ultrasonic motor driving control system based on high-performance Digital Signal Processor(DSP) and Direct Digital Synthesis(DDS) technique is designed in the paper. The frequency, amplitude and phase of the motor driving signal can be tuned independently and precisely in this design, and the open-loop characteristics of the ultrasonic motor are measured.

In-phase and quadrature-phase (IQ) sinusoidal signals are used as bases functions in many phase modulation schemes in communication systems. Generating such signals in engineering education laboratories without higher-end signal generators is quite challenging. Most of the time, the IQ signals used in undergraduate engineering education laboratories are in audio frequency range that is used to demonstrate or experiment with various phase modulation schemes. This paper presents a method to generate IQ sinusoids in the audio frequency range using direct digital synthesis technique. The system developed is simulated using MathWorks® Simulink and implemented on commonly available Xilinx’s® Spartan 6 FPGA. The system designed is capable of producing phase correct sine and cosine waves having frequencies between 1 Hz and 20 kHz.

Phase feedback and adjustment between wireless nodes greatly reduce the power efficiency of distributed beamforming. In this paper, we propose a distributed transmit beamforming method without any phase feedback between nodes. The concept of our approach is to have the received signals retrace their ways, so that the phase offset of the forward path compensates that of the backward path; as a result, signals from different nodes in-phase combine at the destination. Therefore, the received power or the communication range is increased. In order to implement the concept of "retracement", we also propose a transceiver prototype which is based on the Direct Digital Synthesis technique. Experimental and simulation results validate the effectiveness of our approach.

This paper presents a detailed study on the design of a miniature, ultra-broadband, high-resolution, low-power consumption frequency synthesizer which employs both the direct and indirect frequency synthesis techniques. A high-resolution, fast frequency-switching DDS (direct digital synthesis) acts as the reference of a broad-band phase locked loop which is the key component of the frequency synthesizer. The theoretical resolution of the design is 128μHz and the bandwidth ranges from 137.5MHz to 4.4GHz. The supply voltage is 5V, corresponding to a total power consumption of 2W. The frequency synthesizer is described in detail and some analyses are made based on the experimental results.

This article discusses the current state and development trends of microwave frequency synthesizers for test-and-measurement instruments. The discussed trends are also applicable for other synthesizer types used as modules in more complex systems. Test-and-measurement synthesizer market is estimated at $300 with an annual growth rate about 3%.A modern trend for the development of frequency synthesizers is associated with low phase noise, low spurious and fast switching speed. Important parameters also include operating frequency range, frequency resolution, modulation capabilities as well as size and cost characteristics. The main architectures based on direct analog, direct digital and indirect synthesis are evaluated. As of today, traditional indirect phase-lock-loop (PLL) architectures still dominate. On the other hand, direct analog synthesis is the most advanced approach that demonstrates extremely fast switching speed and low phase noise. Nevertheless, future developments are associated with direct digital synthesis (DDS) due to the rapid progress in solid-state technologies. DDS are currently available as special integrated circuits (IC) or can be build using field-programmable logic arrays (FPGA) and high-frequency digital-to-analog converters (DAC). Parallel (multichannel) digital structures coupled with high-frequency DACs allow generating output signals at microwave frequencies. Further improvements are possible using two or more DACs in an interleaved data mode. Wider frequency coverage through several tens of gigahertz and lower spur characteristics are expected.The article notes that modern frequency synthesizers allow generating complex signals using vector IQ-modulation. The modulation bandwidth is constantly increases through hundreds of megahertz or even several gigahertz. Further advances in microwave frequency synthesizers are associated with new reference types such as sapphire-loaded cavity oscillators with combined frequency stabilization as well as optoelectronic methods.

This chapter provides a design of micro-broadband radar signal source based on direct digital frequency synthesis technology. This micro-broadband radar signal source is composed of baseband signal source and frequency multiplier chain. Direct Digital Synthesis (DDS) chip AD9858 was used in the baseband signal source. A FPGA chip was employed to load DDS control words to create 200MHz ± 50MHz baseband signal. Multiplier chain achieved up-conversion and frequency doubling of baseband signal, and output 1.5GHz + 400MHz broadband radar Linear Frequency Modulated (LFM) signal. Oscilloscope and spectrum analyzer measurements results showed that the quality of LFM signal met the design requirements.KeywordsExcitation SignalLinear Frequency ModulateBaseband SignalLinear Frequency Modulate SignalFPGA ChipThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Direct digital synthesis (DDS) is a useful tool for generating periodic waveforms. In this two-part article, the basic idea of this synthesis technique is presented and then focused on the quality of the sinewave a DDS can create, introducing the SFDR quality parameter. Next effective methods to increase the SFDR are presented through sinewave approximations, hardware schemes such as dithering and noise shaping, and an extensive list of reference. When the desired output is a digital signal, the signal's characteristics can be accurately predicted using the formulas given in this article. When the desired output is an analog signal, the reader should keep in mind that the performance of the DDS is eventually limited by the performance of the digital-to-analog converter and the follow-on analog filter. Hoping that this article would incite engineers to use DDS either in integrated circuits DDS or software-implemented DDS. From the author's experience, this technique has proven valuable when frequency resolution is the challenge, particularly when using low-cost microcontrollers.

PurposeThis paper aims to analyze the pressure behavior in dual porosity reservoirs using different techniques in an attempt to correctly characterize reservoir properties. Pressure transient tests in naturally fractured reservoirs often exhibit non-uniform responses.Design/methodology/approachThe pressure transient tests in naturally fractured reservoirs were analyzed using conventional semi-log analysis, type curve matching (using commercial software) and Tiab’s direct synthesis (TDS) technique. In addition, the TDS method was applied in case of a naturally fractured formation with a vertical hydraulic fracture. These techniques were applied to a single-layer, naturally fractured reservoir under pseudosteady state matrix flow. By studying the unique characteristics of the different flow regimes appear on the pressure and pressure derivative curves, various reservoir characteristics can be obtained such as permeability, skin factor and fracture properties.FindingsFor naturally fractured reservoirs, a comparison between the results semi-log analysis, software matching and TDS method is presented. In case of wellbore storage, early time flow regime can be obscured that lead to incomplete semi-log analysis. Furthermore, the type curve matching usually gives a non-uniqueness solution, as it needs all the flow regimes to be observed. However, the direct synthesis method used analytical equation to calculate reservoir and well parameters without type curve matching. For naturally fractured reservoirs with a vertical fracture, the pressure behavior of wells crossed by a uniform flux and infinite conductivity fracture is analyzed using TDS technique. The different flow regimes on the pressure derivative curve were used to calculate the fracture half-length in addition to other reservoir properties.Originality/valueThe results of different field cases showed that TDS technique offers several advantages compared to semi-log analysis and type curve matching. It can be used even if some flow regimes are not observed. Direct synthesis results are accurate compared to the available core data and the software matching results. It can be used to confirm the software matching results and to give reliable reservoir characteristics when there is lack of data.

High silica zeolite Y nanocrystals by dealumination and direct synthesis

linear frequency modulated continuous wave (LFM-CW) radars require high linearity and good phase noise characteristics of its modulated signal to obtain a good resolution and sensitivity. Direct digital Synthesis (DDS) is becoming an increasingly competitive alternative to traditional Voltage Controlled Oscillators (VCO) to perform the modulation. Although there are plenty of publications describing the performance of the DDS, there has up to now not been any direct comparison between the performance of the DDS and the VCO as applied in FM-CW radars. In this paper the performance of DDS is analyzed both theoretically and with measurements. The performance of DDS in a linear frequency modulated continuous wave (LFM-CW) radar system, (the Transportable Atmospheric Radar TARA developed in IRCTR), is compared to a VCO demonstrating its superiority. DDS is, therefore, expected to play an important role in radar systems in the near future.

Various modulation techniques are usually utilized to enhance the radar performance, or to add more capabilities to the radar that otherwise would not have been possible. Digital generation methods of frequency modulated continuous wave signals include direct waveform synthesis and frequency synthesis. The implementation of waveform generation and upconversion method are described in this paper with a simplified digital implementation technique using FPGAs (Field Programmable Gate Array). The design follows a systematic approach following steps of timing generation from external encoder, baseband modulated waveform generation, upconversion of the waveform to intermediate frequency, filtering and finally frequency synthesis using external DDS (Direct Digital Synthesizer). The design is also capable of generating BITE waveform for test checking in the system. Our design is capable of generation of waveform for stationary as well as non-stationary radars. For non-stationary radars, the waveform is so generated that the doppler effect due to the movement of the radar is compensated. The paper explains more on this. This work mainly focuses on the fact that the total design has been implemented on a single FPGA and the implementation solution utilizes the efficient FPGA resources so as to meet the timings in crucial applications. Moreover, the paper enhances the features of the design with simulation and real time results used to validate the design.