International Journal of Engineering and Technical Research (IJETR) ISSN: 2321-0869, Volume-3, Issue-6, June 2015 64 www.erpublication.org Abstract— In this paper, we present a VLSI implementation of low pass cascade & linear phase FIR filter for low power design. A dynamic power can be control using power supply. We proposed a VHDL implementation of low pass FIR filter. A output of the system in discrete form will transfer to MATLAB for frequency response generation. To make the pipelining more synchronous we have use a array based ROM to store inter-stage output. A cascade & linear phase FIR will be placed in the system and power consumption and frequency response will analysis. Index Terms— FIR, Dynamic power, ROM I. INTRODUCTION A finite impulse response (FIR) filter is a filter whose impulse response is of finite duration or response to any finite length input, because it settles to zero in finite time [1]. The impulse response of an Nth-order discrete-time FIR filter lasts exactly N + 1 sample from first nonzero element through last nonzero element, before it then settles to zero. FIR filter can be discrete-time or continuous-time and digital or analog [2]. FIR filter output is shown by following equation,          1 0 N k k k n x h n y (1) x[n] represents the filter input. H k represents the filter coefficients. y[n] represents the filter output. N is the number of filter coefficients (order of the filter). On taking z-transform of the above equation we get, ) ( ........ ) ( ) ( ) ( ) ( ) 1 ( 1 2 2 1 1 0 z X z h z X z h z X z h z X h z Y N N           (2) The equation of Y (z ) can be directly represented by a block diagram as shown in fig 1 and this structure is called Direct form structure or Fd.R filter [3]. The direct form structure provides a direct relation between time domain and z- domain equations. Jaya Gupta, student, M.Tech, VLSI Technology, Jagan Nath University, Jaipur, India Arpan Shah, Assistant Professor Department of ECE, Jagan Nath University, Jaipur, India Ramesh Bharti, Associate Professor Department of ECE, Jagan Nath University, Jaipur, India Fig 1 Direct Form structure of FIR Filter The frequency response of FIR filter is presented by ) (  j d e H . So the equation for DFT coefficients H(k) can be written as k j N k w j d e e H k H        2 ) ( ) ( (3) Where 2 1   N  , k= 0, 1,… (N-1) The samples of impulse response h(n) is given by, When N is odd,                       ) 2 1 ( 1 2 ) ( Re 2 ) 0 ( 1 ) ( N k N nk j e k H H N n h (4) When N is even,                       ) 1 2 ( 1 2 ) ( Re 2 ) 0 ( 1 ) ( N k N nk j e k H H N n h (5) Now the Transfer Function H (z) of the filter is given by z- transform of h (n).       1 0 ) ( ) ( ) ( ) ( N n n z n h z X z Y z H (6) The magnitude response ) (  j e H is given by A(  ),where ) cos( ) 2 1 ( 2 ) 2 1 ( ) ( 2 1 1 n n N h N h A N n           (7) VLSI Implementation and Performance Evaluation of Low Pass Cascade & Linear Phase FIR Filter Jaya Gupta, Arpan Shah, Ramesh Bharti