GC5016 Datasheet, PDF (33/88 Pages) Texas Instruments – WIDEBAND QUAD DIGITAL DOWN CONVERTER/ UP CONVERTER

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GC5016
SLWS142G − JANUARY 2003 − REVISED NOVEMBER 2005
14 GC5016 DIGITAL UP CONVERSION (DUC) MODE
The GC5016 can be configured as a digital up converter (DUC). The DUC interpolates, filters, mixes, and sums the
customer inputs into one or several output ports. The GC5016 DUC (See Figures 2 and 16) has several blocks:
Transmit Input Interface
Gain
PFIR
CIC
Mixer
Sum, SumIn, and Transmit Output Formatter
The GC5016 has either four independent DUC channels, or two Wideband (split IQ) DUC channels. The DUC
accepts real or complex inputs, with complex being the more common. The GC5016 can have one, two, or four real
or complex DUC outputs.
The up-conversion channel details are reproduced in Figure 16.
20
I
18
127 to 255 Tap
18
6 Stage
20
21
Gain
PFIR
CIC Filter
Q
Interp. by 4*16
Interp. by 1*256
20
18
18
20
21
19
20
20
48
Frequency
Phase
NCO
16
Figure 16. Up-Conversion Channel Detail
The Transmit input formatter generates the Frame Strobe and channel divided clock, and is used to receive the
customer IQ data. The data input can be parallel IQ, interleaved IQ, or Time Division Multiplexed (TDM) IQ. The
Frame Strobe signal is generated to indicate to customer logic that another input sample is required.
The gain block provides fine gain adjustment for the channel’s IQ data.
The PFIR provides the first stage of interpolation. The typical PFIR interpolation is 3, 4, or 5. The number of PFIR
taps is dependent on the number of data streams and number of clocks available to compute the FIR taps. The PFIR
can interpolate from 1 to 16.
The Cascade Integrator Comb (CIC)filter provides the second stage of interpolation. The 6 stage CIC M=1 filter can
interpolate from 1 to 256.
The interpolated IQ data and the NCO’s frequency output sinusoid are mixed together in the mixer to generate the
channel digital IF output. The mixer output can be real or complex.
The Sum block within the GC5016 can be used to combine other GC5016 outputs (using the SumIn path) with this
GC5016’s channels.
The Transmit Output Format logic converts the Sum or fixed scale data to the Real, Interleaved Complex, Parallel
Complex, Double Rate Real, or Double Rate Complex output modes. An IFLG signal is output.
14.1 Special Modes− Split IQ, and Double Rate DUC Output
There are two special DUC modes: SplitIQ, and double rate.
The splitIQ Mode combines two channels to provide for more PFIR filtering. The A and B, or C and D channels can
be used in the splitIQ mode. The A and C channels process the I data, and the B and D channels process the Q data.
The parallel IQ and TDM modes may be used with the splitiq mode. In the splitIQ mode, the channel A and C mixers
are used. The cmd5016 software keywords splitiQ, splitIQ_AB, and splitIQ_CD are used to control this function.
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