The modern day direct sampling FPGA/SOC devices like AMD’s Radio Frequency System-on-Chip (RFSoC) or Altera’s Agilex9 platforms delivers a fundamental shift in software-defined radio design: by integrating RF-class data converters, programmable logic, and ARM cores onto a single silicon die, it enables up to 64 GSPS ADC sampling and DAC output, and up to 16×16 MIMO in a Full-Height Half-Length PCIe card. But raw performance is only half the story as achieving high-performance SDR solutions requires more than just raw hardware capability—the true value lies in efficiently harnessing this performance through optimized architectures, software frameworks, and application-specific innovations which iWave is trying to address using various Adaptive SDR Framework.
What truly distinguishes these frameworks is its runtime adaptability — the ability to reshape the signal chain on-the-fly without halting operation or reloading firmware. Dynamic decimation and interpolation tuning, switchable streaming modes, and configurable channel counts transform this SDR from a fixed-function instrument into a live, responsive platform that evolves with the mission.
SDR Framework: The Platform’s Defining Capability
Static hardware is the antithesis of software-defined radio. The direct RF platform is built around the principle that every critical parameter of the signal chain— sample rate, bandwidth, channel count, data transfer mode — must be tuneable at runtime, without downtime, without bitstream reloads, and without disrupting adjacent channels. This section examines each reconfigurability dimension in depth.
Decimation Filter Tuning — Adaptive Receive Bandwidth
The receive path uses programmable decimation filters to reduce ADC sample rates before data reaches the FPGA fabric, The Adaptive SDR Framework enables dynamic decimation tuning at runtime, allowing SDR systems to adjust receive bandwidth without interrupting operation.
Why this matters: The optimal receive bandwidth is application-dependent and time-varying. A spectrum monitoring task may require a wide window say 2 GHz during initial scan, then narrow to 1 MHz around a signal of interest for demodulation — all without stopping acquisition.
Decimation Factors & Receive Applications
• ×2 decimation: Full wideband capture, maximum data rate to fabric
• ×4 decimation: Dual-band monitoring with reduced FPGA load
• ×8 decimation: Regional spectrum surveillance
• ×16 and above: Narrowband modes for low-power embedded operation
Integrated low-pass filters prevent aliasing during decimation without consuming FPGA fabric resources, preserving logic for signal processing.
Operational Impact: Switching decimation factor mid-operation takes effect within microseconds. A cognitive radio receiver can widen its capture window to detect emerging interference, then immediately narrow to a protected channel — the transition is seamless from the application’s perspective.
Interpolation Filter Tuning — Adaptive Transmit Bandwidth
On the transmit path, interpolation increases the DAC input sample rate, allowing the FPGA to operate at lower data rates while the DAC runs at full speed. This reduces fabric throughput requirements at the expense of output bandwidth. Within the Adaptive SDR Framework, interpolation factors can be modified in real time to optimize transmit bandwidth and FPGA resource utilization.
Why this matters: Transmit waveform requirements change with mission phase. A wideband jamming or channel sounding waveform may need the higher DAC bandwidth. A precision narrowband uplink needs only a fraction of that — and the FPGA throughput saved can be redirected to waveform quality, pre-distortion, or additional channels.
Interpolation Modes & Transmit Applications
• ×2 interpolation: Channel sounding, wideband waveform synthesis, radar chirp generation
• ×4 interpolation: Multi-carrier LTE/NR transmit, electronic countermeasures
• ×8 interpolation: Precision uplinks, single-carrier modulation, reduced fabric load
• Higher factors: Embedded tone generation, calibration signal injection, low-power narrowband beacons
Dynamic interpolation tuning is particularly powerful in multi-channel transmit configurations: individual DAC channels can operate at different interpolation factors simultaneously. A system can transmit a wideband waveform on channels 1–4 while concurrently transmitting a narrowband reference on channels 5–6, all from the same PCIe card, all without a configuration break
Burst Mode vs. Continuous Streaming — Matching Data Flow to Mission
The data transport layer between the RFSoC or Agilex9 and the host CPU is not a one-size-fits-all pipe. The SDR framework provides two fundamentally different streaming architectures, each optimised for a different class of application. Crucially, the mode can be changed at runtime without hardware reconfiguration
The Adaptive SDR Framework supports both burst mode and continuous streaming, enabling flexible deployment across radar, SIGINT, and communication applications.
Burst Mode Streaming
- Trigger-gated: Each acquisition window is precisely bounded by a hardware or software trigger
- SYSREF-aligned: Burst edges lock to the MTS clock edge for deterministic timing
- Low dead time: Transfers sized exactly to the capture window — no padding overhead
- Best for: Pulsed radar, channel sounding, spectrum sweeping, EW intercept
Continuous Streaming
- Uninterrupted: DMA engine and FPGA fabric sustain lossless flow to host memory at line rate
- Zero-gap: No acquisition dead time between transfers — every sample is delivered
- Backpressure: PCIe Gen 4 ×8 sustains all 16 channels simultaneously without throttling
- Best for: Spectrum monitoring, 5G NR data collection, SIGINT, real-time demodulation
The distinction matters operationally. In burst mode, the system captures a precisely-timed snapshot — for example, a 100 µs receive window aligned to a radar pulse repetition interval. In continuous mode, the system streams every sample to the host for offline or real-time processing, relying on the PCIe/ethernet/Auroara host interface capacity to sustain the load across all active channels.
Design Insight: Because streaming mode is a runtime parameter rather than a compiled-in firmware choice, the same hardware supports both use cases. A system can operate in continuous mode for wideband survey, then switch to burst mode for precision time-gated capture — all within the same operational session.
Configurable Channel Count — Scale to the Mission
The Adaptive SDR Framework supports up to 16×16 MIMO, with ADC and DAC channels dynamically enabled or disabled at runtime to optimize power, FPGA resource utilization, and data throughput for the mission.
Why this matters: Channel count flexibility turns a single hardware platform into a family of instruments. The same card can operate as a 2-channel precision receiver for laboratory calibration, a 4-channel coherent MIMO testbed for algorithm development, or a full 16-channel array for production system validation — the only difference is runtime configuration.
Channel Scaling Scenarios
- 2–4 channels: High-fidelity laboratory measurement, calibration, single-beam radar — maximum FPGA resources per channel for deep processing pipelines
- 8 channels: 4×4 MIMO testbed, multi-beam direction finding, multi-channel SIGINT — balanced performance and channel density
- 16 channels: Full massive MIMO prototype, 16-element phased array, dense spectrum monitoring across 16 independent frequency slots
- Mixed TX/RX: Asymmetric configurations — e.g., 4 TX + 16 RX for downlink-heavy beamforming research — supported natively
Disabling unused ADC/DAC tiles reduces power consumption and thermal dissipation, providing valuable thermal headroom in space-constrained deployments. It also frees FPGA resources, enabling more advanced processing—such as larger FFTs, stronger FEC, or enhanced beamforming—on the remaining active channels.
SDR Framework Reconfigurability Summary
The Adaptive SDR Framework provides comprehensive runtime control over bandwidth, channel scaling, and streaming modes, enabling maximum deployment flexibility.
| Parameter | What Changes | Operational Benefits |
|---|---|---|
| Decimation factor | Effective receive bandwidth per channel | Narrow or widen RX BW to match signal environment without reconfiguration |
| Interpolation factor | Transmit DAC data rate & output bandwidth | Match TX bandwidth to waveform requirements; free fabric for processing |
| Streaming mode | Data flow pattern (burst vs. continuous) | Precision time-gated capture or lossless continuous monitoring — same hardware |
| Active channel count | Enabled ADC/DAC tiles (2 to 16) | Scale power, thermals, and FPGA resources to application needs |
| NCO frequency | Per-channel centre frequency | Rapid frequency hopping and waveform agility in microseconds |
Conclusion
The Adaptive SDR Framework demonstrates how runtime reconfigurability unlocks the full potential of modern RFSoC and Agilex 9 SDR platforms in real-world deployments.
The ability to tune decimation and interpolation factors mid-operation, switch between burst and continuous streaming, and rescale channel count from 2 to 16 without hardware changes means that a single framework can be effectively used to build a wideband survey receiver in the morning, a precision narrowband demodulator in the afternoon, and a 16-element phased-array transmitter in the evening — all running from the same framework.
This is not incremental improvement. It is a redefinition of what a software-defined radio platform can be.
For more information about our SDR Framework Platforms, contacts us at mktg@iwave-global.com
