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RF Engines Ltd (RFEL) provide a range of high specification FPGA-based
Pipelined Fast Fourier Transform (FFT) cores. The pipelined or "streaming"
architecture ensures that all cores can process back-to-back blocks
of time-domain input data in real-time. FFT parameters such as radix,
processing parallelism and bit growth can be tailored by RFEL to
suit each application resulting in the most optimal design in terms
of silicon, power and performance.
Complementary core options include polyphase and standard windowing,
input buffering for single or multiple channel processing, input
buffering for overlapped FFT processing, bit-reversal and 100% efficient
real input FFT processing.
The designs are sold as Intellectual Property (IP) cores to equipment
manufacturers and allow a low cost and reduced risk route to a faster
design cycle.

Overview of the Range
The range includes the following types of FFT core:
1) HiSpeed FFT cores implement a Pipelined radix-2 Decimate
In Frequency (DIF) algorithm using a single data path pipeline.
This 'parallelism of 1' can typically accept complex time-domain
data at a maximum continuous rate (and hence signal bandwidth) of
100MHz, depending on the FPGA target. The HiSpeed architecture is
designed to be the smallest of the Vectis range in terms of logic
and multiplier resource, and is matched in terms of real-time bandwidth
to currently available 12-bit and 14-bit Analogue to Digital Converter
(ADC) devices. Product Page
2) QuadSpeed FFT cores implement a Pipelined radix-2 DIF
algorithm with a parallelism of 4. These cores can typically accept
complex time-domain data at a maximum continuous rate of 400MHz.
A QuadSpeed FFT core will consume roughly the same memory resource,
two to three times the logic and three to four times the multiplier
resource required by a HiSpeed core of the same transform length
and arithmetic precision. Product
Page
3) Matrix FFT cores implement a mixed-radix algorithm with
a parallelism of 2. These cores can typically accept complex time-domain
data at a maximum continuous rate of 200MHz. Transforms of any length
can be implemented, providing sufficient FPGA resource is available.
Product Page
4) HyperSpeed FFT cores implement a mixed-radix algorithm
with a parallelism of '2M' and a transform length of 'M x N'. 'M'
and 'N' can be any integer, though integer powers of two provide
the most silicon-efficient implementations. A HyperSpeed core with
a parallelism of 8 can typically accept complex time-domain data
at a maximum continuous rate of 800MHz. Product
Page
5) HyperLength FFT cores implement a mixed-radix algorithm
that requires RAM external to the FPGA to achieve large transform
lengths. Both transform length and maximum sustained processing
bandwidth are dependent on the type and configuration of external
RAM. Product Page
The Xilinx FFT Library includes a selection of more than
sixty HiSpeed and QuadSpeed FFT cores targetted at Xilinx Spartan
III, Virtex II, Virtex II Pro, and Virtex IV devices. The cores
are supplied on a single CD, and include a site licence for R&D
development purposes, and a licence for use of the cores in manufactured
product. Product Page
Features
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Pipeline architecture allows continuous processing with no gaps
in data |
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Parameterisable
at factory in terms of: |
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Processing
parallelism (defines maximum complex data rate) |
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FFT
length (powers of two / mixed-radix) |
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Arithmetic
bit-widths |
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Twiddle-factor
bit-width |
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Input
buffering |
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Bit-reverser |
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Resource
assignment (e.g. RAM and / or Multipliers versus Logic) |
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Fully
synchronous design |
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IFFT
control input |
Benefits
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Highly
optimised design with minimum silicon usage |
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Virtually
any transform length possible |
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Virtually
any bandwidth possible for short transform lengths |
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Parameterised
HDL design may be modified by RFEL to meet specific requirements |
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Fully
tested Netlist delivery |
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Fixed-point
Matlab models provided to de-risk core integration process |
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Reduced
technical and timescale risk to project |
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