Texas Instruments Incorporated

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GC2011A 3.3V DIGITAL FILTER CHIP

SLWS129A

This document contains information which may be changed at any time without notice

2.1

TRANSVERSAL FILTERS

The chip implements finite impulse response (FIR) transversal filters defined by Equation (1):

where x(n) is the input sample at time n, y(n) is the output sample at time n, N is the number of taps in the filter and h(k)

are the filter coefficients. Many common filters are symmetric, meaning the tap coefficients are symmetric about the

center tap. For example, the 16 coefficients (1, 2, 3, 4, 5, 6, 7, 8, 8, 7, 6, 5, 4, 3, 2, 1) have even-length symmetry. The

15 coefficients (1, 2, 3, 4, 5, 6, 7, 8, 7, 6, 5, 4, 3, 2, 1) have odd-length symmetry. Figure 2 shows the basic transversal

filter structure for an 8 tap non-symmetric filter, a 16 tap even symmetry filter and a 15 tap odd symmetry filter (actual

GC2011A filter sizes are up to 256 taps).

Figure 2. Basic Transversal Filters

The GC2011A chip implements the transversal filter structures shown in Figure 2 with the addition of pipeline

delays to increase the maximum clock rate of the chip. The pipeline delays add latency to the chip but do not effect its

operation.

yn

()

hk

()xn k

–

()

k

0

=

N

1

–

∑

=

Eq. (1)

x(n)

y(n)

(a) 8 TAP NON-SYMMETRIC FILTER

x(n)

y(n)

(b) 16 TAP EVEN SYMMETRY FILTER

x(n)

y(n)

(c) 15 TAP ODD SYMMETRY FILTER