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PERFORMANCE ANALYSIS OF RADAR BASED ON DS-BPSK MODULATION TECHNIQUE

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PERFORMANCE ANALYSIS OF RADAR BASED ON DS-BPSK MODULATION TECHNIQUE Powered By Docstoc
					        INTERNATIONAL JOURNAL OF ELECTRONICS AND
  International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN
  0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 4, Issue 2, March – April (2013), © IAEME
COMMUNICATION ENGINEERING & TECHNOLOGY (IJECET)
ISSN 0976 – 6464(Print)
ISSN 0976 – 6472(Online)
Volume 4, Issue 2, March – April, 2013, pp. 137-143
                                                                            IJECET
© IAEME: www.iaeme.com/ijecet.asp
Journal Impact Factor (2013): 5.8896 (Calculated by GISI)                  ©IAEME
www.jifactor.com




             PERFORMANCE ANALYSIS OF RADAR BASED ON DS-BPSK
                          MODULATION TECHNIQUE

                                   Ami Munshi1, Srija Unnikrishnan2
      1
          (Watumull Instiute of Electronics and Telecommunication Engg and Computer Technology,
                                        University of Mumbai, India)
                 2
                   (Fr Conceicao Rodrigues College of Engg, University of Mumbai, India)


   ABSTRACT

          Radar (Radio Detection and Ranging) systems are widely used now-a-days as
   automotive radar for Intelligent Transport System (ITS). In this paper we mainly focus on
   analyzing the performance short distance radar based on spread spectrum technology. Spread
   spectrum modulation technique is chosen as it has some significant properties like accuracy
   of ranging, sensitivity, accuracy of power-estimation, interference suppression etc. The
   system is implemented in Matlab/Simulink.

   Keywords: DSSS, BPSK, Spread Spectrum, BER

 I.            INTRODUCTION

           The electronic principle on which radar operates is very similar to the principle of
   sound-wave reflection. If you shout in the direction of a sound-reflecting object, you will hear
   an echo. If you know the speed of sound in air, you can then estimate the distance and general
   direction of the object. The time required for an echo to return can be roughly converted to
   distance if the speed of sound is known [[1]][[2]].
           In this paper, we focus on analyzing a radar system based on direct sequence spread
   spectrum modulation technique. The goal is to detect target at a very short distance as near as
   20cm with high resolution. The system is developed in Matlab/Simulink. Simulink is a
   software package for modeling, simulating, and analyzing dynamic systems at any point. The
   performance is evaluated using Monte Carlo Simulation method.
           Section 2 gives details of DS-BPSK Radar model. Section 3 gives simulation results
   followed by conclusion in section 4 and references.

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 International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN
 0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 4, Issue 2, March – April (2013), © IAEME

II.      IMPLEMENTATION OF DS-BPSK RADAR

  DIRECT SEQUENCE SPREAD SPECTRUM MODULATION
         Spread spectrum is transmission technique in which pseudo noise code, independent
  of the data is employed as spread the signal energy over a bandwidth much greater than
                                                                                     pseudo
  information signal bandwidth. At the receiver, signal is despread using replica of pse
  noise code generator [[3]].

          In DSSS the spreading of the signal bandwidth occurs at baseband by multiplying the
                                chipping                                          pseudo-random
  baseband data pulses with a chipping sequence. This chipping sequence is a pseudo
  binary waveform with a pulse duration of Tc and a chipping rate of Rc=1/Tc. Each pulse is
  called a chip and Tc is the chip interval. For a given information symbol of duration Ts and a
                      =1/Ts,
  symbol rate of Rs=1/Ts, the duration of each chip is much less than the pulse length of the
                                                              than                      Rc>>Rs).
  information symbol (i.e., Tc<<Ts) and Rc is much higher than the symbol rate (i.e., Rc>>Rs)
  In practical systems, the number of chips per symbol must be an integer number with t         the
                                                                          [        ]..
  transition of the data symbols and the chips occurring at the same time [[3]][[4]].. The ratio of
  chips to symbols is called the spreading gain k or bandwidth expansion factor Be where,

  k= Be= Nc= Ts/Tc= Rc/Rs                                                                      (1)
  RADAR MODEL




                            Fig. 1. Model of Spread Spectrum Radar

         Fig.1. shows the basic architecture of radar using spread spectrum modulation
  technique. Baseband part of the transmitter section mainly consists of binary data generation,
  spreading the data using PN sequence and its modulation (BPSK). By using Bernoulli binary
  generator block in the communication tool box of Simulink, we can generate binary data
  stream of 250Kbps. By using PN sequence generator block in the communication tool box,

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International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN
0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 4, Issue 2, March – April (2013), © IAEME

we can generate PN sequence of 9Gbps data rate. By using BPSK modulator baseband block
                                                             [
in the communication tool box, we modulate the spread signal [[5]][[6]][[7]].

At the receiver front end, the received signal power is measured calculated using radar range
equation as follows

Prec = Pt G2 λ2σ                                                                            (2)
       (4π) 3 R4

         The delay between transmitted and received signal is calculated and accordingly
target range is obtained. The Error Rate Calculator is used at the receiver to calculate Bit
Error Rate (BER). It calculates the error rate as a running statistic, by dividing the total
number of unequal pairs of data elements by the total number of input data elements from one
    rce.
source. Autocorrelation is the one of the vital part of the system that provides uniqueness to
this radar system. The first operation of autocorrelation block is bit by bit synchronism of the
                                                                   integrated
received and transmitted signal and then bit by bit multiplied, integrated and dumped. The
power of the received signal represents the presence of target and the delay of the auto
                                                                      [          [10]].
correlation block represents the target distance from the transmitter [[8]][[9]][[10]




                                    Fig. 2. Target Model

                                                       2.
        The target model design is shown in Fig 2. Depending on the target range, the
transmitted signal is delayed and the signal power is attenuated. This signal is then reflected
towards the receiver. In the target, there is a provision made to change target cross section,
                                                              receiver
target range, and accordingly the reflected power towards the receiver.




                                              139
  International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN
  0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 4, Issue 2, March – April (2013), © IAEME

III.       SIMULATION RESULTS

           Various graphs are plotted by using following data in the model:

                          Chip rate (fc)                   1Gbps
                          Transmitted Power (Pt)           1W
                          Antenna Gain                     100
                          Wavelength(λ)                    0.3m
                          Target Cross Section (σ)         1m2
                          Minimum detectable signal        0.011mW
                          power (Pmin)
                          Velocity of light (c)            3x108m/s
                          Maximum        Radar     Range   8m
                          (Rmax)

                       Table. 1. Specifications of Spread Spectrum Radar

   EB/NO   VERSUS   BER

          For range (R) = 1m, Eb/No Vs BER graph is plotted using Bit Error Rate Analysis
   Tool in Matlab/Simulink. Monte Carlo simulation results and theoretical results are in Fig.3.
   below. We can see that as Eb/No ratio increases, BER decreases.




                                 Fig. 3. Eb/No versus BER graph

   RANGE VERSUS SIGNAL POWER

         As radar range increases, the signal power received at the receiver decreases. The
   minimum detectable signal power at the receiver Pmin= 0.000110726W or -39.55dB for
   Rmax =8m. Fig.4. shows the graph of range versus received signal power.

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International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN
0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 4, Issue 2, March – April (2013), © IAEME




                        Fig. 4. Range versus Received Power graph

CHIP RATE VERSUS MAXIMUM RANGE

       Relation between chip rate and maximum radar range is given by the following
equation.

        Rmax=     (Pt G2 λ2 σ) ¼                                                          (3)
                  ((4π) 3 Pmin) 1/4

        where, λ = c/fc
        where, c = 3e8 m/s, velocity of light

        We see that as the chip rate increases, the maximum range of detection decreases.
Fig.5. portray this relation.




                     Fig. 5. Chip Rate versus Maximum Range graph
                                                141
International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN
0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 4, Issue 2, March – April (2013), © IAEME

THEORETICAL DISTANCE VERSUS COMPUTED DISTANCE

        Fig.6. shows the graph of theoretical distance of the target and the distance computed
by the radar receiver model.




              Fig. 6. Theoretical Distance versus Computed Distance graph

IDENTIFICATION OF TARGET




                    Fig. 7. Detection of Target of σ = 1m2 at range 4m

        Fig.7. shows the target of σ= 1m2at 4m range. The received signal power at the
                                       =
              26.52dB).               X                                                     Y-
receiver is (-26.52dB). In the figure X-axis represents the target range in meters where as Y
axis represents the received signal power in dB. Here distance of the target is calculated by
calculating the relative time delay between the received signal and transmitted signal.

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  International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN
  0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 4, Issue 2, March – April (2013), © IAEME

IV.           CONCLUSION

              The work presented here gives design, implementation and analysis of radar transmitter-
      receiver using Matlab/Simulink. With chip rate of fc=1 GHz and target cross section σ=1m2 this radar
      model is based on radar range equation to detect maximum range of 8m and minimum range of 20cm.
      The peculiarity of this radar is that it is able to detect objects placed at a very short distance. The
      performance is examined using Monte Carlo simulation. It is observed that the system is more
      accurate in computing the distance of the target towards the maximum range. It is also noted that as
      the signal to noise ratio (Eb/No) increases the Bit Error Rate (BER) decreases. We can vary the
      detection range by changing the chip rate. There is also a provision for changing target cross section
      and antenna gain and accordingly the detection range can be varied. In this work, autocorrelation is
      one of the vital parts of the system that provides uniqueness to this radar system. The auto correlated
      value obtained from the align signal block represents the presence of target and the delay represents
      the target distance from the transmitter. The technology uses DS-BPSK signals to create noise like
      modulation, making the transmitted signal virtually undetectable to other receivers. The system
      developed has virtues such as high reliability, robustness, good efficiency, interference suppression,
      low power consumption etc., due to coding of the baseband pulses with PN sequence.

      REFERENCES

      [1]      Christian Wolff. Radartutorial.eu. December 20, 2009.
      http://www.radartutorial.eu/druck/index.en.html (accessed February 15, 2012).
      [2]      M Richards, J Scheer, W Holms. Principles of Modern Radar. Raleigh, NC 27615: Scitech, May
      2010.
      [3]      Meel, J. "De Nayer Instituut." October 1999.
      sss-mag.com/pdf/Ss_jme_denayer_intro_print.pdfSimilar (accessed February 15, 2012).
      [4]      Duke, Peter Smith. Direct sequence spread spectrum modulation for utility packet transmission in
      under water acoustic communciation network . Thesis, Monterey, California: Naval Postgraduate School,
      September 2002.
      [5]      Kanna, Ravikanath. Design of Zigbee Transmitter Receiver IEEE 802.15.4 using
      Matlab/Simulink. Masters Thesis, Rourkela, Odhisha: National Institute of Technology, 2011.
      [6]      Y. Ayogi, T Fukuchi, H Endo, M Kusunoki, Y Iso, K. Inoue, H. Ishizu, R. Kohno. "76Ghz Spread
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      ITSC '97., IEEE. 1997. 677-682.
      [7]      L. Sakkila, P. Deloof ,Y. Elhillali ,A. Rivenq ,S. Niar. "A real time signal processing for an
      anticollision road radar system." Vehicular Technology Conference. IEEE, 2006. 1-5.
      [8]      Soumyasree Bera, Debasish Bhaskar, Rabindranath Bera. www.ursi.org. 2011.
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      [9]      Mathworks. 2012. www.mathworks.com/help/toolbox/comm/ref/alignsignals.html (accessed
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      [10] Ami Munshi, Srija. Unnikrishnan. (May-June 2012). Implementation of Radar Transmitter-
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      [11] Sanjay M Trivedi and B. S. Raman, “Design of a Unified Timing Signal Generator (UTSG) for
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      [12] P.Ravi Kumar, G. Suresh , Dr. Y.Bhavani Kumar and D. Arun Kumar, “Laser Radar System for
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      Issue 2, 2012, pp. 474 - 483, ISSN Print: 0976-6464, ISSN Online: 0976-6472.


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