High-Level Synthesis (HLS)

HLS tools synthesize untimed C++ or SystemC descriptions directly into Register Transfer Level (RTL) implementations. This allows DPD algorithm designers to model complex Volterra kernels or memory polynomials in software, then automatically generate pipelined hardware. The abstraction eliminates the need to manually specify clock-cycle-accurate behavior, reducing development time from months to weeks.

Designers guide synthesis using compiler directives called pragmas to control hardware architecture without rewriting code:

• PIPELINE: Reduces initiation interval for streaming DPD data
• UNROLL: Parallelizes complex multipliers across DSP48 slices
• ARRAY_PARTITION: Maps coefficient tables to block RAM for simultaneous access
• DATAFLOW: Enables task-level parallelism between predistorter stages

HLS enables rapid what-if analysis of different micro-architectures. Engineers can sweep pragma configurations to balance throughput against resource utilization on a Xilinx RFSoC or Zynq UltraScale+. The tool reports clock frequency estimates and initiation intervals, ensuring the synthesized predistorter core meets the strict real-time adaptation latency budget before committing to place-and-route.

HLS tools automatically infer AXI4-Stream master and slave ports from function arguments, enabling seamless integration into Vivado IP Integrator block designs. A DPD function taking a stream of complex baseband samples is synthesized with standard handshake signals (TVALID, TREADY), connecting directly to JESD204B DMA engines or SERDES wrappers without custom glue logic.

HLS supports arbitrary-precision fixed-point arithmetic through template libraries. Algorithm designers can prototype with floating-point for correctness, then systematically reduce bit widths to minimize DSP48 slice consumption. The tool automatically propagates quantization effects, enabling precise trade-off analysis between coefficient quantization error and hardware cost for look-up table DPD implementations.

HLS flows include C/RTL co-simulation where the original C++ testbench drives both the software model and the generated RTL. This ensures bit-accurate equivalence between the algorithmic specification and the synthesized predistorter core. DPD engineers can inject captured power amplifier behavioral model data to verify linearization performance in simulation before hardware-in-the-loop testing.

The hardware description abstraction that models synchronous digital circuits in terms of data flow between registers and logical operations. HLS tools automatically generate RTL from C++ behavioral descriptions, eliminating manual Verilog/VHDL coding. RTL is the target output of the synthesis process, representing the clock-cycle-accurate microarchitecture before logic synthesis maps it to FPGA primitives.

A hardware optimization technique that inserts register stages between combinational logic operations to increase maximum clock frequency. In HLS, pragmas like #pragma HLS PIPELINE enable initiation interval (II) control, allowing new input samples to be accepted every clock cycle. For DPD cores, pipelining is essential to meet tight latency budgets while maintaining the throughput required for wideband signal linearization.

A high-throughput, unidirectional point-to-point protocol from the ARM AMBA 4 specification. HLS tools synthesize function arguments into AXI4-Stream ports using directives like #pragma HLS INTERFACE axis. This interface is the backbone of DPD data paths, connecting the predistorter core to DACs and ADCs without buffering overhead, using TVALID/TREADY handshaking for backpressure control.

A dedicated high-speed arithmetic logic block within Xilinx FPGAs, optimized for multiply-accumulate (MAC) operations. HLS tools automatically infer DSP48 usage for operations like complex multiplication in predistorter cores. Each slice contains a 25x18-bit multiplier and 48-bit accumulator, making it the fundamental compute primitive for implementing FIR filters and polynomial evaluation in DPD signal chains.

A numerical representation system where digits have a fixed radix point, essential for efficient FPGA implementation. HLS supports arbitrary-precision fixed-point types via ap_fixed<W,I> templates, enabling designers to specify exact bit widths. This avoids the resource cost of floating-point units while preserving the dynamic range needed for DPD coefficient precision and signal fidelity.

A hardware design paradigm where processing is triggered by data availability rather than a centralized program counter. The #pragma HLS DATAFLOW directive enables task-level parallelism, allowing multiple functions to execute concurrently in a streaming pipeline. This naturally maps the streaming nature of DPD signal processing, where sample acquisition, predistortion computation, and output generation operate simultaneously.