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Digital filters - Computable efficient recursive filters

Anna Engelbert ; Carl Hallqvist
Göteborg : Chalmers tekniska högskola, 2008. Ex - Institutionen för signaler och system, Chalmers tekniska högskola, ISSN 99-2747920-4; 057, 2008.
[Examensarbete på grundnivå]

In signal processing, the most widely used digital filter type is the Finite Impulse Response (FIR), mainly for its guaranteed stability. However, these filters requiring a higher order for the same specification compared with its recursive correspondence, the Infinite Impulse Response (IIR) filter. The order can be seen as required number of adders, multipliers and memory for the filter. In Application Specific Integrated Circuits (ASIC) and Field Programmable Gate Arrays (FPGA) applications, especially number of multipliers is desirable to keep low due the extensive logic. Hence, signal processing with FIR filters will result in a large amount of silicon or gates used. This thesis proposes two recursive filters, the Cascaded Integrator Comb- (CIC) filter and the Wave Digital Filter (WDF), where the former is used mainly for interpolation- or decimation. The CIC is a recursive moving average filter which is multiplier free, consisting only of two building blocks and has a linear phase. The WDFs simulates an analog lossless network, such as the ladder- or the lattice structure by using the bilinear transform and voltage waves as signal parameters. For fair comparison of the filters, methods for estimating the hardware cost are developed. A FIR halfband filter is also included and may be seen as a reference in both hardware cost and performance. For comparing performance Error Vector Magnitude (EVM) and Adjacent Channel Leakage Ratio is used, according the method described in 3GPP (3rd Generation Partnership Project). Moreover, interpolation and decimation is handled in a mathematical way to show the importance of using good lowpass filters in multirate systems.



Publikationen registrerades 2008-10-02. Den ändrades senast 2013-04-04

CPL ID: 74710

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