Vol. 2, Issue I, Jan ISSN

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1 REALIZING A SIGNAL GENERATOR WITH ARBITRARY WAVEFORMS ON FPGA USING DIRECT DIGITAL SYNTHESIS AND DESIGNING WITH PLAN AHEAD Twinkle Gupta 1, Mudit Vaish 2, Mr. Rakesh Jain 3 1 Research Scholar, Jaipur (Raj.) gupta.twinkle18291@gmail.com, 2 Research Scholar, Jaipur (Raj.) muditvaish8191@gmail.com, 3 Assistant Professor, Jaipur (Raj.) jaijinendra@gmail.com Abstract: As the world is attracting towards the compact digital designing techniques, growing science is developing the products matches to our comfort like those are efficient, fast working and have superior bear and tear quality than the old mechanism. In electronics field this compactness plays a big role, multiple things can be designed on a single chip. Here is an example of that: A Signal Generator. We can design a signal generator that is not bulky in size, less distortion figures, cost effective and efficient in every manner. Its designing technique is DDS and the whole working can be implemented through VHDL language and we can sum up this on a single chip named FPGA and can see the whole picture of clock signals, input blocks, output blocks, voltage and ground connections with the help of PLAN AHEAD Software. Keywords: Signal Generator, FPGA, DDS technology, PLANAHEAD (Xilinx14.1) 1. INTRODUCTION Signal generator is related with a complex electronic box that has complex signals, unwanted noise, typical merging of frequencies and a heavy body and sometimes its operation become so typical. As its name implies, it is only to produce sine waves. Signal generators generally produce some electric impulses. We can also use it in a lab as testing equipment. A complex circuitry is used to design a signal generator s hardware. It contains quartz crystal, two keys presented at the front of signal generator s body which are known as frequency key and amplitude key and to adjust the signals manually, a knob is presented near to these keys. To connect the communication cable and to sweep the signal a trigger button is used and for toggling, the mod key (on/off) is used. These all together make a heavy structure, it increases its complexity [3]. To reduce this complexity here is an alternate; it can be designed on a single chip (FPGA). FPGA gives a platform to implement any kind of design. These are prefabricated semiconductor devices based around a matrix of configurable logic blocks (CBLs) connected via programmable interconnects. Basically FPGAs contain I/O blocks, CBLs, Mux s, F/F s, and optional registers to store data. 2. LITERATURE REVIEW In history we can t assume a signal generator generating hybrid or arbitrary waveforms as it was designed to produce only sine waves. For the generation of standard waveforms and arbitrary/hybrid waveforms, it is categorized into two categories: Frequency generator Arbitrary waveform generator Function generator often produces a repeating electrical signal [11]. We can also find it as a periodic signal. It can also generate several types of waves like square, sine, saw tooth and triangular waves based on requirement of user. Function generator generates the standard functions including sine wave too [4]. AWG generates any form of wave either standard form or nonstandard form. This type of generator generates the output of any type of pulse like standard waveforms (squaw, tri, pulses, Page 70

2 etc.), non-standard waveforms (exponential, cardiac, etc.), and combination of two or more signals or much more a user can expect from such type of generator. There is always found a mixture of various types of waves and they all are produced in digital form [5]. So to see them in analog form a DAC circuit is always available to convert the digital part into analog. Both are different in their ways to generate frequencies, phenomenon/architecture, and its technique of synthesis. But it s not enough as the technology is moving towards a new space. To give a new technology wings to an ordinary signal generator the older way of synthesis and older design is not enough. As various elements restrict its working and limit its analytical part of measuring the waveforms. DDS is viewed as a growing technology. Let s have a look on direct digital synthesis. It is a technology with new and enhanced features of frequency synthesis and a better way to produce signals. Micro-Hertz tuning resolution of output frequency and sub-degree phase tuning capability, all under complete digital control. The DDS architecture eliminates the need for the manual system tuning and tweaking associated with component aging and temperature drift in analog synthesizer solutions. Now focus on its designing, which make it more flexible to handle all analytical problems that can t be solved in a complex structure. A short sized less complex design let the spurs of signals out and give more and more reliable output. Here we are merging the arbitrary/hybrid waveforms with the standard waveforms including sine wave for counting its amplitude on each step/interval. Its designing steps those can be viewed through Xilinx based software PLAN AHEAD. This software is loaded with all new and advanced features those are helpful in structural design. Xilinx uses a LUT format to design an FPGA. Through LUT a user can easily design a digital form of wave with particular intervals [7]. This process of designing is simple but attractive. And with this when DDS is used this term makes the device more efficient and add reduced complexity feature in it, as the whole circuitry is designed over a single chip. And PLAN AHEAD is that software which provides the designing view of its device plan and its package plan such as Mux, flip-flops, I/O blocks, registers, and all peripherals connected with the FPGA at a glance [8]. modulation schemes [9]. This technique allows direct modulation of the output signal in the digital domain. DDS is restricted to lower frequencies ( 100 MHz) to avoid high power consumption. Sine wave which is shown in fig.3 is the amplitude of standard waveform. Figure 1: Square Wave 3. DDS TECHNOLOGY Direct digital synthesis technique this scheme proposed in 1971 and soon came to the attention because of its good frequency resolution and fast frequency performance [2]. The DDS can be FM, PM or AM modulated. Fig.1 is showing the square wave. Fig.2 is showing the triangular wave. These waves are treated as pulse train for modulation. It can generate arbitrary waveforms and capable of fast switching between frequencies. DDS avoids the use of an analog VCO and achieves low phase noise, provides fine frequency steps (close channel spacing) also provide continuous-phase channel switching at the output, an important property in some Figure 2: Triangular Wave Page 71

3 Xilinx 14.1: The scheme proposed to design FPGAs is software designing such as Xilinx based designing [1]. Xilinx14.1 is the software that supports programming language VHDL and with the help of LUT method an FPGA can be programmed for any type of circuit or any type of system for which a user want to mold it. And also reconfigurable any time according to demand. Although expensive but popular in market as suitable for any kind of design. LUTs are the best part of designing. Through this any type of waveform can be designed digitally with particular intervals. 4. DESIGNING SCHEME We can realize our project on Xilinx tool known as PLAN AHEAD. PLAN AHEAD is software that can be used in various ways at different points in the FPGA design flow. This software provides a complete flow management tool from RTL development to circuit debugging. A full package of designing tool on which we can elaborate our whole design in such a way that it can show particular block schematic, I/O planning view. Here are the block diagrams of all waves viewed through plan ahead produced by the signal generator. Figure 4: Square Wave + Saw Tooth Wave Fig.4 shows the arbitrary waveform that is the combination of square wave and saw tooth wave. And in additional, Plan Ahead can be used to control each major step of the FPGA design process, including RTL development and analysis, logic synthesis, physical design analysis, floor planning and implementation control with the ISE software [10]. Here is the view of floor planning and device package in fig. 5 and fig. 6. Figure 3: Sine Wave Figure 5: Floorplanning View Page 72

4 5. CONCLUSION Every device and instrument has its own limits and conditions of working. Merging various techniques make a circuit complex and heavy. But this signal generator which we are designing is neither heavy in its hardware nor complex in its designing and working. Thus we conclude that programming a signal generator on FPGA including arbitrary/hybrid waveforms is quite good example in reference of growing technique [6]. DDS makes it more reliable and efficient device by providing a new phenomenon of synthesis that is not limited to just phase and oscillator s frequencies. Direct digital synthesis synthesizes the waveforms without any disturbance and spurges. The impact of direct digital synthesis is far reaching, and the opportunities and advantages are extensive. This technology is better than PLL based frequency synthesis. Now collect the qualities of PLAN AHEAD, an FPGA designing software plan proposed by Xilinx. Loaded with all designing tools (floor planning, RTL schematic, elaborated designing step, implementation, placement and routing step, I/O view, clock view, device view etc.) including a full project dictionary, through which log files can be located very easily. FPGA has a better future with PLAN AHEAD. It sets each and every pin according to designing algorithm. To accommodate this, different types of Plan Ahead Projects can be created. They are differentiated by types of input sources used to create the Project. 6. ADVANTAGES Arranging all the facts and features together, these three ideas of making a signal generator better that it can produce the mixture of standard and non-standard waveforms, explore infinite advantages of it. Here are some: Starting with its designing, FPGA the single chip contains the whole complex design of a signal generator. An FPGA design makes it cost effective. Next idea is an alternate to the old way of synthesis (PLL), introduction of direct digital synthesis to signal generator gives it new wings to generate the various types of waveforms on different ranges of frequency without any distortion, noise, limited feedback range, speed and spurges [12]. As DDS completes its task very fast and digitally, it has a power and spark to be stayed in the world of digital signal processing. Power consumption of this type of signal generator is affordable as its components work on low voltages i.e. 3V to 12V. Size issues are not here; its size is small and precise. Figure 6: Package View Less time consumable as the process of performing the waveforms can be done immediately as soon as it can be read through the RAM of the circuit. 7. FUTURE WORK Including all the pros and cons of these three ideas we can assume that DDS will be a technology to synthesize a signal generator with arbitrary waveforms without any restricted plans and algorithms. And using PLAN AHEAD we can design any complex circuit without facing any type of complexity in it. Both the techniques have their own uniqueness and criteria on their performances. Thus both can be used with any digital system and instruments have a great future with these two dynamic areas of the digital world. FPGA plays an important role in the advancement of this signal generator. This moldable technology makes it cost effective and less time consumable [13]. Hence it has a great scope in future to design any type of circuit. And through VHDL the complexity of writing a proper algorithm for the circuit reduces. This is reason that the whole package of these all verities is beneficial for the construction of any kind of circuitry whatever circuit a user want to make in execution practically. For further improvement we can add a DAC circuit with FPGA kit board to see the waveforms in their exact analog form. REFERENCES [1] Wang Jingsheng, Sun Lin, VHDL EDA software development MAX + PLUS II applications [J], Journal of Shandong University of Science and Technology, 2004 (23) 1: [2] Zheng Bing, Fang Huali, FPGA-based direct digital frequency synthesis device [J] information and computer,2009,8:9-10. Page 73

5 [3] Liu, L., L. Huang, X. Tan and G. Fang, 2009a. Design of a sine signal generator. Electr. Design Eng., 17(7): [4] Feng, X., W. Zhong, L. Hu and W. Lu, Multimodulation function sine wave generator based on DDS. Foreign Electr. Meas. Technol., 29(1): [5] ZHOU Qiao-di,HUANG Ji-ye,LIU Jing-biao, An Experimental Method of Sine-Wave Signal Generator Based on FPGA. ; Research and Exploration Laboratory,2003. [6] Dr. Konstantinos Tatas,ACOE201 Computer Architecture I Laboratory Exercises Background and Introduction to FPGAs. [7] Gregory Ray Goslin, Digital Signal Processing Program Manager Xilinx, Inc Logic Dr. San Jose, CA 95124,a guide to using field programmable gate arrays (FPGAs) for application-specific digital signal processing performance. [8] David Maliniak, Electronic Design Automation Editor, basics of FPGA design, A Supplement to Electronic Design/December 4, [9] Analog Devices, Inc., a technical tutorial on digital signal synthesis, [10] Shoucheng Ding, Aimin An and Xinke Gou, College of Electrical and Information Engineering, Lanzhou University of Technology, Lanzhou , China, DIGITAL WAVEFORM GENERATOR BASED ON FPGA,Research Journal of Applied Sciences, Engineering and Technology 4(14): , [11] Manjiri A. Bopche, Dr A.Y. Deshmukh, Department Of Electronics Engineering G. H. Raisoni College of Engineering, Digdoh Hills, Nagpur, India , FPGA BASED DIRECT DIGITAL SYNTHESIS FUNCTION GENERATOR, International Journal of VLSI and Signal Processing Applications, Vol. 1, Issue 2, May 2011,(8-14),ISSN [12] WU Shu-rong, YANG Yin-tang, ZHU Zhang-m ing., Design of a DDS Based on FPGA ;. Aeronautical Computing Technique,2006,1:1-3. [13] FU Yu-peng, LI Ming-hao, LU Jin-hua, The Technique of DDS Design and its Realization with FPGA. ; Journal of Dalian Nationalities University,2004,5: Page 74