Area Efficient Reconfigurable Digital Up Converter for Software Defined Radio Based Wireless Sys
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July 2010,Volume 7,No.7(Serial No.68) Journal of Communication and Computer,ISSN I 548—7709,USA 龇 … Area Efficient ReCOnfigurabIe Digital Up Converter for Software Defined Radio Based Wireless Systems R ̄esh Mehra,Swapna Devi ECE Department,National Institute of Technical Teacher’Training&Research,Sector一26,Chandigarh 1 6001 9.India Received:May 12,2010/Accepted:June 01.2010/Published:July 25,2010 Abstract:In this paper an optimized approach is presented to implement an area efifcient digital up converter(Due)for Software Defined Radio(SDR).The proposed Due has been implemented using equiripple based multistage polyphase decomposition technique to reduce the computational complexi tty which results n i reduced area consumption on target FPG A device In thi.s method .proposed design has been implemented using embedded DSP48E macros to save general purpose logic which can be further utilized to implement other related functions on the same device.The DUC is designed with Matlab,simulated with Modelsim synthesized with Xilinx Synthesis Tool(XST)and implemented on Vir【ex.5 based xc5vlx50t.1ff1 l36 FPGA device.The results show that proposed DUC has consumed only 3%slices.4%LUTs and l0%flip lops fdue to efficient utilization ofembedded DSP48E macros available on target device.The proposed design has consumed 0.37734 W powers at 28.8。C iunction temperature to provide cost effective solution or fSDR based wireless communication applications. Key words:ASIC,Due,FPGA.SDR,XST 1.Intr0ducti0n Today’s consumer electronics such as cellular PDAs,portable computers and other nomadic computing devices.To flourish and succeed in these phones and other multi—media and wireless devices dynamic environment equipment suppliers must build highly flexible systems that operate across multiple often require digital signal processing(DSP) algorithms for several crucial operations in order to increase speed,reduce area and power consumption. wireless and wired network standards.They must be able to rapidly adopt new business models as they evolve,and they must be able to incorporate new signal The widespread use of digital representation of signals or transmission and storage has created challfenges in processing techniques that allow increased network capacity,increased coverage,increased quality of service,or a combination of al1.The answer to the the area of digital signal processing[1].The applications ofdigital FIR filter and up/down sampling techniques are found everywhere in modern electronic diverse range of requirements is the software deined fradio.There are many applications where the sampling products.For every electronic product,lower circuit complexity is always an important design target since it rate must be changed.Interpolators and decimators are utilized to increase or decrease the sampling rate.Up reduces the cost[2].The range of user terminals that need to be connected in this communication world, include cell phones,video phones,satellite phones, sampler and down sampler are used to change the sampling rate of digital signal in multi rate DSP systems.This rate conversion requirement leads to production of undesired signals associated with C0rresponding author: Rajesh Mehra(1 972一 ).ME. assistant professor.research fields:signal processing wireless & mobile communication. vlsi design. E.mail: aliasing and imaging errors.So some kind of filter should be placed to attenuate these errors.Filter is the rajeshmehra ̄:yahoo.com. Swapna Devi(1 970-1.Ph.D.,associate professor research ielfds:signal&image processing.soft computing. key point of the interpolator[3].Single—rate digital Area Efficient Reconfigurable Digital Up Converter for Software Defined Radio Based Wireless Systems 29 ilfters have been used to perform the sampling rate conversion process,however,they proved to be slow in terms of processing time due to the many filtering taps that must be used.Ultimately,multirate filters were particular it is widely recognized that DSPs and FPGAs are the most suited supports.However,when high data rates are involved,FPGAs can better fit the system requirements[8].So this paper focuses on eficifent design of Due on an FPGA target device. developed to offer relatively low sampling rate,thereby resulting in fewer iltering ftaps compared to single—rate iflters[4】.The digital signal processing application by 2.Digital Up Converter(Due) using variable sampling rates can improve the lfexibility of a software defined radio.It reduces the need for expensive anti—aliasing analog filters and enables processing of different types of signals with different sampling rates.It allows partitioning of the high—speed processing into parallel multiple lower speed processing tasks which can lead to a significant saving in computational power and cost. Due to a growing demand for such complex DSP applications,high performance,low—cost Soc jmpjementatiOns of DSP algorithms are receiving increased attention among researchers and design engineers.Although ASICs and DSP chips have been the traditional solution for high performance applications,now the technology and the market demands are looking for changes.On one hand,high development costs and time..to..market factors associated with ASICs can be prohibitive for certain applications whi le,on the other hand,programmable DSP processors can be unable to meet desired performance due to their sequential—execution architecture.In this context,embedded FPGAs offer a very attractive solution that balance high flexibility, time—to。market,cost and performance.Digital Up converter(Due)is the signiifcant nuclear physical module of wireless communication transmitter.One significant advantage of this converter is the requirements on the analogy components are relaxed [5】.In DUC,pulse shaping,interpolation and rfequency translation are the processes that executed in the design[6】.Up sampler is basic sampling rate alteration device used to increase the sampling rate by an integer factor[7】,The Due of SDR paradigm can be exploited resorting to different physical layers:in An ideal SDR base station would perform all signal processing tasks in the digital domain.However, current—generation wideband data converters cannot support the processing bandwidth and dynamic range required across different wireless standards.As a result, the analog—to—digital converter(ADC)and the digital—to—analog converter(DAC)are usually operated at intermediate frequency(IF)and separate wideband analog front ends are used for subsequent signal processing to the radio frequency(RF)stages.Digital IF extends the scope ofdigital signal processing(DSP) beyond the baseband domain out to the antenna to the RF domain.This increases the flexibility of the system while reducing manufacturing costs.Moreover,digital rfequency conversion provides greater flexibility and higher performance in terms of attenuation and selectivity than traditional analog techniques.The DUC section of SDR is mainly consists of root raised cosine(RRC)filter,interpolator and numerically controlled oscillator(NCO1 as shown in Fig.1.In digital up conversion,the input data is baseband if ltered and interpolated before it is quadrature modulated with a tunable carrier frequency.To implement the interpolating baseband finite impulse response(FIR)filter is used which can be optimal ifxed or adaptive filter architectures. NCO can generate a wide range of architectures for oscillators with spurious—free dynamic range in excess of 1 1 5 dB and very high performance.Depending on the number of rfequency assignments to be supported, 一 三基二 ~1. Fig.1 Digital up converter. 30 Area Efficient Reconfigurable Digital Up Converter for Software Defined Radio Based Wireless Systems digital uD converters can be implemented in an FPGA. 3G code—division multiple access(CDMA)一based systems and multi.carrier systems such as orthogonal rfequency division multiplexing(OFDM)exhibit signals with high crest factors(peak—to—average ratios). Such signals drastically reduce the efifciency of PAs used in the base stations.So crest factor reduction (CFR)is used to overcome this problem. 3.Proposed DUC Design In this paper,a Digital Up Converter(Due) designed has been designed to meet the future generation speciifcations using a pulse shaping FIR filter,compensating FIR interpolator,multi—section CIC interpolator using equiripple based polyphase decomposition technique with the help of Matlab[9]. The equiripple technique has been used because it needs less number ofrequired coefncients as compared to Kaiser or other window techniques to ̄mprove computational complexity and enhance speed.A DUC has been designed to convert the base band signal into high output sample rates found in a digital radio.At ifrst stage,a 32.tap equiripple based pulse shaping FIR iflter has been designed with interpolation factor of2 as shown in Fig.2.The word length and fraction length are set to be 1 6.1 5 for input and output respectively- The second stage of Due consists of 1 1一tap equiripple based FIR compensation filter with interpolation factor of 2 whose output response has been shown in Fig.3.The word length and fraction length are set to be 16,15 for input and output respectively. At third stage CIC filter has been used because it can achieve high sampling rate and can be implemented without multipliers.A 5.stage CIC filter is created with interpolation factor of 32 whose output response is shown in Fig.4.The input word length and fraction length are set to be 1 6 and 1 5.The output word length has been used as 20.The output fraction length and iflter internals have been calculated automatically to preserve full precision in order to achieve better results without losing the required information. Finally all the developed filters have been cascaded to design the final optimized DUC whose response has been shown in Fig.5. Magatitude Response(d 3 7Tap Fl R lnterlmlator ∞ 童 篁 ∞ 档 警 基_ Nomlalized Frequency(× ra&sample) Fig.2 Pulse shaping FIR f一M_f 一ilter- _ l l Magnitude Response(dB) 】 11 I)F l llI 粤‘) j: : Nonnalized Frequency(×A rad/ ̄mple) Fig.3 Compensation FIR iflter・ Magnitude Respon ̄(dB) 已 童 ’三 曲 。: :≤, - :! ;’ : —。 ; 是 i} Nonnalized Frequency(xll ra ̄samp!e) Fig.4 CIC Area Efficient Reconfigurable Digital Up Converter for Software Defined Radio Based Wireless Systems 3 I 一 1)一0f'_l1_ I, 4.Implementation Results&Discussion == 潦Ⅲ The hardware implementation of proposed multistage polyphase decomposition technique based optimized DUC is done by developing required VHDL code.In this technique,all the required coeficients are fdivided in two pars by using 2-branch polyphase decomposition.The proposed efficient two branch polyphase DUC structure has been shown in Fig.6 and can be expressed as: Fig.6 Proposed eficientf polyphase structure. ==n 删 氩娃 ; _=__: ==蔓 ~ 娃砖 童 H(z)=E..(= )+ .-IE (Z ) (1) In this structure input signal has been decimated before filtering which reduces the number of coeficients required to implementf the desired filter. This coefficient reduction in turn reduces the computational and hardware complexity of the proposed design.In the next step,the developed VHDL code has been simulated and tested using Modelsim simulator.The modelsim based zoomed in and zoomed Fig.7 Zoomed in DUC output response. out responses have been shown in Fig.7 and Fig.8 Magnitude Response(dB) ; { 3-Stage Cascaded DUC Reference Signal { Fig.8 Zoom out Due output response respectively.Then the tested VHDL model has been 撇 Nornmlized FroNt|they(x rad sample) Fig.5 Due response. Table 1 Resource utilization. synthesized and implemented on Viaex.5 based xc5vlx50t一1 ffl 1 36 target device. The resource utilization of the proposed model on Virtex一5 target device has been shown in Table 1 which shows that the proposed DDC has consumed Device utilization summary(estimated values) Logic utilization Number of slice registers 【-J Available 28,800 Used 965 Utilization(%) 3 Number of slice LUTs Number of fully used LUT FF pairs Number of bonded IOBS Number of BUFG/BUFGCTRLS 1,317 226 40 】 28,800 2.056 480 32 4 10 8 3 Number of DSP48Es 43 48 89 32 Area Efficient ReconfigurabIe Digital Up Converter for Software Defined Radio Based Wireless Systems Table 2 Power consumption Name Clocks Logic Value 0.00975(w) 0.00000 fw) Used l 2.043 TotaI available Utilization(%) 28.800 7.1 Signals 0.00000(w) 2.974 10s DSPs 0.00000(w) 0.00000(w1 40 43 542 48 7.4 89.6 Total qtiescent power Total dynamic power 0.36758(w1 0.00975(w) Total power O.37734(w1 Junction temp 28 8(degreesC) l965. 3—1 0%of general purpose resources in terms of slices, LUTs and flip-flops by eficifent utilization of embedded DSP48E macros available on target device. 【2】 S.J.Jou.K.Y.Jheng,H.Y.Chen,A.Y.Wu,Multiplierless multirate decimator/interpolator module generator,1EEE Asia—Pacific Conference on Advanced System Integrated Circuits,2004,pp.58—61. The proposed design has consumed 0.37734 W power at 28.8。C junction temperature as shown in Table 2. 5.Conclusions In this paper,an optimized multistage polyphase 【3】 H.P.Kuang,D.J.Wang.G.Zhou,Z.P.Xu,A multi-channel, area-eficifent, audio sampling rate interpolator.IEEE 8 International Conference on ASIC. 2009.pp.2 l-24. 【4】 A.H. AIi. An ef cient configurable hardware decomposition technique is presented to implement digital up converter for software defined radios.An equiripple technique is used to reduce the required number of coeficients in overallf design.The proposed implementation of fundamental multirate filter banks.5th International Multi—Conference on Systems,Signals and Devices.2008.PP.1-5. M.Luo.Y.F.Zhao.Z.M.Wang.An area.efficient 【5】 B.interpolator applied in audio ∑-△DAC.Third Intemational IEEE Conference on Signal-Image Technologies and Internet—Based System,2008,PP. 538-54l DUC has consumed only 3%slices,4%LUTs and 1 0 %flip flops due to eficifent utilization of embedded DSP48E macros available on Virtex-5 based xc5vlx50t一1 ffl 1 36 target device.The developed design M.Zawawi.M.F.Ain.S.I.S.Hassan.M.A.Zakariya, 【6】 N.C.Y.Hui.R.Hussin.Implementing WCDMA digital up converter in FPGA.IEEE International RF and Microwave Conference,2008,pp.91—95. tra,Digital Signal Processing.Tata Mc Graw Hil1. 【7】 S K MiThird Edition,2006. has consumed 0.37734 W power at 28.8。C iunction temperature to provide cost effective solution for software radio based wireless applications. 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