1 Overview
Converts between sample rates whose ratio is not rational, or is rational with an inconvenient denominator — the usual case when a converter clock and a symbol rate are derived from unrelated references. The Farrow structure makes the resampling ratio a run-time input, so it can also close a timing-recovery loop directly.
2 Features
- Arbitrary, run-time-variable resampling ratio from 0.25 to 4.0
- Lagrange or minimax-optimised polynomial coefficients
- Polynomial order 2 – 6, selected at build time
- Usable as the interpolator inside a symbol-timing loop
- Image rejection > 90 dB over the useful passband
- Multi-channel mode with shared arithmetic
3 Applications
- O-RAN radio units and small cells
- Wideband transmit and receive signal chains
- Multi-carrier and multi-band radios
- Spectrum monitoring and surveillance receivers
4 Specifications
Figures below are for a representative configuration. Resource, latency and throughput scale with the build-time parameters; the released datasheet gives each as a closed-form function of those parameters so you can compute the number for your own configuration.
| Ratio | 0.25 – 4.0, arbitrary and run-time variable |
|---|---|
| Structure | Farrow, polynomial order 2 – 6 |
| Image rejection | > 90 dB (order 5, 80 % passband) |
| Ratio resolution | 32-bit fractional |
| Throughput | 1 sample per clock, up to 500 MHz |
| Interfaces | AXI4-Stream data, AXI4-Lite control |
| Typical FPGA | 1.4 kLUT, 18 DSP @ 400 MHz |
| Product family | Digital Front-End |
| Availability | Production |
5 Interfaces and control
The core presents AXI4-Stream data, AXI4-Lite control. All streaming interfaces follow the AXI4-Stream handshake with full back-pressure support; the control plane is generated by ALF-CR-REGGEN, so the register map in section 5 is generated from the same source as the delivered VHDL and cannot drift from it.
The register map is delivered as an IP-XACT description alongside a C header and a UVM register abstraction layer, all generated together. Every field carries its access policy, reset value and any side effect in the generated documentation.
6 Configuration
The core is configured through a single package file of build-time parameters and an elaboration-time consistency check that fails the build — rather than failing in simulation — when a parameter combination is not supported. There is no source fork per configuration, so you stay on the mainline release and keep receiving maintenance updates.
Re-parameterisation within the documented range is covered by your licence at no additional cost. If you need a parameter outside the documented range, that is a design services conversation rather than a new licence.
7 Verification
ALF-RF-FRS is signed off against the release criteria described on the quality page: bit-exact agreement with the reference model across the regression suite, 100 % statement, branch and toggle coverage with every exclusion reviewed, formal proof of deadlock freedom and reset correctness on the control logic, and timing closure with positive slack on every supported target from the delivered constraints.
The verification environment used for that sign-off is part of the deliverable set. You can re-run it against your own configuration on your own farm.
8 Deliverables
| VHDL source | Synthesisable VHDL-2008, readable and commented, lint-clean |
|---|---|
| Closed-box alternative | Encrypted netlist or protected model, where source is not licensed |
| Reference model | Bit-accurate C++ (Python bindings) or MATLAB, with stimulus scripts |
| Verification | UVM testbench, functional coverage model, interface assertions |
| Test vectors | Directed and constrained-random sets with expected outputs |
| Synthesis | Timing constraints, build scripts and reference reports per target |
| Example design | Buildable project instantiating the core in a system context |
| Documentation | Datasheet, integration guide, register map, interface timing |
| Software | Bare-metal C driver and Linux reference driver, where applicable |
9 Licensing and ordering
ALF-RF-FRS is available under single-project, multi-project, evaluation and academic licences. All models are one-time fees with no per-unit royalty. See licensing for the full terms, or request a quotation quoting this part number.
10 Document revision history
| Revision | Date | Change |
|---|---|---|
| 0.1 | July 2026 | Initial preliminary draft |