HSP50214B_07 Datasheet, PDF (57/62 Pages) Intersil Corporation – Programmable Downconverter

HSP50214B
CONTROL WORDS 64-95: DISCRIMINATOR COEFFICIENT REGISTERS (SYNCHRONIZED TO PROCCLK)
BIT
POSITION
FUNCTION
DESCRIPTION
31-10
Discriminator FIR
Coefficient
The discriminator FIR coefficients are 22-bit-two’s complement. If the filter is symmetric, the coefficients
are loaded from the center coefficient at address 64 to the last coefficient. If the filter is asymmetric the
coefficients C₀ to C_N are loaded with C₀ in address 64 up to 64+N, where N is number of asymmetric
coefficients.
BIT
POSITION
31-10
CONTROL WORDS 128-255: 255 PROGRAMMABLE COEFFICIENT REGISTERS
FUNCTION
Programmable FIR
Coefficient
DESCRIPTION
The programmable FIR coefficients are 22-bit-two’s complement. If the filter is symmetric, the
coefficients are loaded from the center coefficient at address 128 to the last coefficient. If the filter is
asymmetric the coefficients C₀ to C_N are loaded with C₀ in address 128 up to 128+N, where N is number
of asymmetric coefficients.
Real Filters are computed as:
Xn-k+1 Ck1 + Xn-k+2 Ck-2 + ... XnC0),
where C0 is the coefficient in address 128 and Xo is the oldest data sample.
Complex filters outputs are computed as follows:
Xn is the most recent data sample.
k is the number of samples = number of (complex) taps.
C0_re is the coefficient loaded into CW128.
C0_im is the coefficient loaded into CW129.
The convolution starts with the oldest data, times the last complex coefficient, and ends with the newest
data, times the first complex coefficient loaded.
Iout = (-Xn-k+1_q * Ck-1_im + Xn-k+1_i * Ck-1_re).
+ (-Xn-k+2_q * Ck-2_im + Xn-1+2_i * Ck-2_re).
+ ...
+ (-Xn_q * C0_im + Xn_i * C0_re).
Qout = (Xn-k+1_i * Ck-1_im + Xn-k+1_q * Ck-1_re).
+ (Xn-k+2_i * Ck-2_im + Xn-1+2_q * Ck-2_re).
+ ...
+ (Xn_i * C0_im + Xn_q * C0_re).
57
FN4450.4
May 1, 2007