Implementation of Adaptive FIR Filter for Pulse Doppler Radar Amritakar Mandal 1 , Brajesh Kumar Kaushik 2 , Brijesh Kumar 3 , R. P. Agarwal 4 1 Electronic Engineering and Installation Unit, New Delhi, INDIA 2,3 Department of Electronics and Computer Engineering, Indian Institute of Technology-Roorkee, INDIA 4 Shobhit University, Meerut, INDIA Email: [amritkar2k@gmail.com; bkk23fec@iitr.ernet.in; brijesh2228@gmail.com; prajan@gmail.com;] Abstract—Digital Signal Processing (DSP) systems involve a wide spectrum of DSP algorithms and their realizations are often accelerated by use of novel VLSI design techniques. Now-a-days various DSP systems are implemented on a variety of programmable signal processors or on application specific VLSI chips. This paper presents the design of Adaptive Finite Impulse Response (FIR) filter for moving target detection in various clutter conditions in Radar Receiver. The design uses pipelined COordinate Rotation DIgital Computer (CORDIC) unit and pipelined multiplier to get high system throughput and reduced latency in each of the pipelined stage. Saving area on silicon substrate is essential to the design of any pipelined CORDIC. The area reduction in proposed design can be achieved through optimization in the number of micro rotations. For better adaptation and performance of Adaptive Filters and to minimize quantization error, the numbers of iterations are also optimized. Keywords— FIR Filter, Radar, Clutter, CORDIC, Pipelined Architecture, Micro-rotation. I. INTRODUCTION CORDIC algorithm was first developed by Jack E. Volder in 1959 [1]. CORDIC algorithm is extremely useful in efficient and effective implementation of DSP systems [2]. This algorithm allows implementation of trigonometric functions like sine, cosine, magnitude and phase with great precision by using just simple shift and adding operations [1-4]. Although the same functions can be implemented using multipliers, variable shift registers or Multiply Accumulator (MAC) units, but CORDIC can implement these functions efficiently while saving enough silicon area which is considered to be a primary design criteria in VLSI technology. This paper designs an adaptive FIR filter based Moving Target Detector (MTD). In MTD, an adjustable local sine/cosine wave generator is required. The sine and cosine terms can be calculated using polynomial approximation, e.g. Taylor series. But it requires a considerable amount of hardware space on the silicon substrate. Interpolation method using table look-up may be the other solution. But it also requires large number of gates and ROM memory. The CORDIC offers the opportunity to calculate the desired functions in a simple and efficient way. Due to the simplicity of the involved operations, the CORDIC realization of adaptive FIR filter is very well suited in VLSI hardware design and its implementation. This paper first describes the principle of target detection in Radar Receiver and then CORDIC algorithm and pipelined architecture design. Thereafter, implementation of CORDIC with adjustment of micro-rotation has been described. Finally CORDIC realization of adaptive filter is described. II. PRINCIPLE OF MOVING TARGET DETECTION For a moving target with a radial velocity, the range over which the wave train travels differs from one repetition to the next. Due to this difference in range, moving echoes are distinguished from fixed echoes [10]. A target with a radial velocity, r V , travels a distance of r r T V . over one repetition period, r T .For the radar pulse, the difference between the distance traveled (including return-trip) from one repetition to the next is: r r T V d . . 2 = Δ For two successive repetitions, the measurement of phase shifts between the transmitted and reflected wave gives the following difference: λ π λ π φ φ θ / . . 2 . 2 / . 2 1 r r n n T V d = Δ = - = + λ π / . . 4 r r T V = Where: n φ and 1 + n φ are phase shifts between transmitted wave and echo at n and ) 1 ( + n th repetitions respectively and λ is the wavelength transmitted by radar. This phenomenon is called Doppler effect. Due to Doppler effect, the frequency of the wave reflected by a moving object differs from the transmitted frequency by a value: λ / . 2 r d V f = , where d f is Doppler frequency Now we can get phase shift in terms of Doppler frequency: r d r d F f T f / . 2 . . 2 π π θ = = where r r T F 1 = The above equation shows that phase shift and Doppler frequency are proportional to target radial velocity. The phase detector in radar receiver measures the phase shift between the transmitted wave in the form of coherent oscillator (COHO) and intermediate frequency (IF) signal. The detected output is a radar vector signal with amplitude and phase. 978-1-4244-9190-2/11/$26.00 ©2011 IEEE