GC2011A datasheet(25/50 Pages) TI

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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

3.9

COMPLEX TO REAL QUADRATURE UPCONVERT

Complex data can be converted to real data by doubling the sample rate, mixing the data up by FS/4 and saving

the real part. The control settings for this mode are shown in Table 9.

The filter is an interpolate by two low pass filter with a pass band from 0 to FS/4 and a stop band from FS/4 to

FS/2, where FS is the output sample rate. The even coefficients of the filter are stored in the A-path filter cells and the

odd-coefficients are stored in the B-path filter cells. The real half of the complex samples are input as A-in, and the

imaginary half are input as B-in. The real results are output as A-out in all modes except for the double rate output mode.

In the double rate output mode the even time samples are output as A-out and the odd time samples are output as B-out.

In the full rate in to double rate out mode the coefficients h(k) are stored in register 1 of each filter cell. In this

mode store h(k) in addresses:

128+2*k+1

for k even, and

192+2*k-1

for k odd,

where k ranges from 0 to 31. h(31) is the center tap.

In the half rate in to full rate out mode the coefficients are stored in registers 0 and 1 of each filter cell. In this

mode store h(k) in addresses:

128+k

for k modulo 4 = 0

192+k-1

for k modulo 4 = 1

128+k-1

for k modulo 4 = 2

192+k-2

for k modulo 4 = 3

where k ranges from 0 to 63. h(63) is the center tap.

In the quarter rate in to half rate out mode the coefficients are stored in registers 0, 1, 2 and 3 of each filter cell.

In this mode store h(k) in addresses:

128+k/2

for k even

192+(k-1)/2

for k odd

where k ranges from 0 to 127. h(127) is the center tap.

Table 10: Complex To Real Conversion Mode Control Register Settings

I/O Rates

Symmetr

# of Taps

(N)

A-PATH

B-PATH

Cascade Output

Latency

Out

REG0 REG1 REG0 REG1

REG

Full

Double

Odd

20D8

6108

00D8

6181

2000

0001

Half

Full

127

638B

A218

438B

A294

2000

0012

Quar-

ter

Half

255

A202

9018

8202

9094

2000

0033

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