cascaded integrator comb filter

Cascaded Integrator Comb Filter

長庚電機通訊組碩一張晉銓

指導教授 : 黃文傑博士

Outline

What is Cascaded Integrator Comb (CIC) Filter

CIC filter transfer function CIC filter Implemented Register Growth Conclusions


In SDR system, samples rate changes very large. A digital linear phase finite impulse (FIR) filters for

decimation and interpolation. No multipliers and use limited storage. Cascaded ideal integrator stages operating at a high

sampling rate and an equal number of comb stages operating at a low sampling rate.


Well-suited for FPGA and ASIC implementation Reduce the computational expense of the

operation

CIC filter transfer function

LI zMzH )

1

11()(

1 L

c zzH )1()( 1

CIC filter transfer function

1 &2 stage CIC frequency response for M=8

L

Mjjw

LM

k

kM

eM

M

eH

zMz

z

MzH

]2/)1[(

1

01

2sin

2sin

)(

)1

()1

11()(

CIC filter transfer function 4 stage CIC frequency response for M=8 &16

CIC Implement of an Decimation Filter

CIC Implement of an interpolation Filter

Register GrowthMLBB in 2max log

Conclusions

Advantage No multipliers ,no storage is required for filter

coefficients The structure of CIC filters is very “regular” Little external control or complicated local timing

is required Easily design for wide range of rate change

factors “M”, with addition of scaling circuit and minimal changes filter timing

Conclusions

Disadvantage Register widths can become large with “M” If system with a fixed decimation ratio, need a des

igned filter to compensate for the CIC passband droop.

Frequency response is fully determined by M & L A new CIC decimation filter with using

“sharpening”

End

Thank you for your attention

cascaded integrator comb filter

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