GC1115 Datasheet, PDF (13/80 Pages) Texas Instruments – Crest Factor Reduction Processor

GC1115
www.ti.com
SLWS144 – FEBRUARY 2005
The CANCEL_MODE register determines whether the GC1115 is using real or complex coefficients
(corresponding to a symmetric or an asymmetric input spectrum), as well as whether coefficient symmetry is to
be exploited. Coefficient symmetry (mirrored coefficients) only applies when using real coefficients. The
CANCEL_MODE register also contains a four-bit field that indicates a timeout or hysteresis value. A non-zero
timeout value indicates that the PDCs are to examine the envelope of the input signal, rather than the magnitude
of the input signal. TI-provided Matlab cancel pulse design software automatically calculates the timeout value.
The CANCEL_LENGTH register specifies the number of unique cancellation coefficients used to cancel peaks.
The CANCEL_MODE register settings affect the interpretation of CANCEL_LENGTH. The following table
describes how CANCEL_LENGTH and CANCEL_DELAY are used, depending on CANCEL_MODE:
Table 2. Relationship Between CANCEL_MODE, CANCEL_LENGTH,
and CANCEL_DELAY
CANCEL_MODE
0 (Real, unique coefs)
1 (Real, mirrored coefs)
1 (Complex, unique coefs)
CANCEL_LENGTH
N (odd, from 15 to 255)
N (odd, from 15 to 255)
N (odd, from 15 to 127)
CANCEL_DELAY
(N-1)/2
N
(N-1)/2
OPERATING MODES
The GC1115 supports a variety of operating modes that accommodate a range of input formats, number of
channels, and follow-on A/D converter and transmit architectures. Users select a specific input and output
operating mode that depends upon:
• The number of channels (one or two)
• The input sampling rate:
– Up to 130 Msamp/sec in 1-channel mode
– Up to 65 Msamp/sec in 2-channel mode
– Down to 25 Msamp/sec in 1-channel parallel mode
– Down to 12.5 Msamp/sec in 1-channel multiplexed mode, or in 2-channel mode
• The input format (parallel or multiplexed)
• The input decimation factor (1, 2, or 4)
• The output interpolator mode (bypass, 2x real, 2x complex, 4x real)
• The output format (parallel, multiplexed, or odd-even; real or complex)
• The internal GC1115 clock rate (up to 320 MHz)
• The PLL multiplier (1x, 2x, or 4x)
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