FIR Double Column

Block: FIR Double Column (fir_dbl_col)
Block Author: Aaron Parsons
Document Author: Ben Blackman

Contents

Summary
Mask Parameters
Ports
Description
- Usage

Summary

Takes in real and imaginary numbers to be multiplied by the coefficients and then the filter sums the real and imaginary parts separately. Then both sums are output as well as a delayed version of the unchanged inputs.

Mask Parameters

Parameter	Variable	Description
Inputs	n_inputs	The number of real inputs and the number of imaginary inputs.
Coefficients	coeff	A vector of coefficients of this FIR. Should be the same number of coefficients as inputs.
Add Latency	add_latency	The latency of the internal adders.
Mult Latency	mult_latency	The latency of the internal multipliers.

Ports

Port	Dir	Data Type	Description
real	IN	Inherited	This real input is to be multiplied by one of the coefficients.
imag	IN	Inherited	This imaginary input is to be multiplied by one of the coefficients.
real_back	IN	Inherited	These real inputs correspond to the second half of the input stream. They get added to one of the `real` inputs before being multiplied by the coefficient.
imag_back	IN	Inherited	These imaginary inputs correspond to the second half of the input stream. They get added to one of the `imag` inputs before being multiplied by the coefficient.
real_out	OUT	Inherited	This output is `real` delayed by 1 cycle.
imag_out	OUT	Inherited	This output is `imag` delayed by 1 cycle.
real_back_out	OUT	Inherited	This output is `real_back` delayed by 1 cycle.
imag_back_out	OUT	Inherited	This output is `imag_back` delayed by 1 cycle.
real_sum	OUT	Inherited	This is the sum of all the multiplications between `real` and `real_back` and their corresponding coefficients.
imag_sum	OUT	Inherited	This is the sum of all the multiplications between `imag` and `imag_back` and their corresponding coefficients.

Description

Usage

This block takes in a number of inputs in parallel and outputs a delayed version of them and also multiplies the inputs by the coefficients. Then real_sum and imag_sum are computed and are delayed due to the latency in the adders which depends both on the add_latency and the number of inputs. For example, if you choose the number of inputs to be 2, then there will be 2 real and 2 real_back input ports along with 2 imag and 2 imag_back input ports. The FIR Double Column blocks takes advantage of the symmetric filter tap coefficients by adding the first and last inputs together before multiplying by the coefficient. This results in a more efficient FIR filter column.