Node Hardware Interface Layer

1. RF Hardware

Supported configurations:

• Phased-array transceiver: Analog Devices AD9371-based radios or USRP X310 (example) with antenna coupler
• Motorized directional antenna: LNA + variable-gain frontend feeding USRP B210 or HackRF One
• Fixed antenna: simplified fixed-gain path for low-ERP test or backup operations

Hardware requirements:

• Carrier frequency: configurable 1–6 GHz (USRP X310), 70 MHz–6 GHz (B210), 10 MHz–6 GHz (HackRF)
• Sample rate: 40 MHz primary, 20 MHz secondary, 10 MHz tertiary
• Bit depth: 12–16 bits I/Q (hardware-dependent)
• Timing accuracy: PPS (pulse-per-second) input for deterministic sample clocking

Local oscillator (LO) reference:

• Source: GPSDO (GPS Disciplined Oscillator) or rubidium standard
• Discipline loop: ±500 ns per day typical after lock
• Fallback: TCXO (Temperature Compensated Crystal Oscillator) with ±2 ppm drift

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2. Phased-Array Beamforming Hardware (Primary Path)

FPGA-based beamforming:

• Device: Lattice ECP5 or Xilinx Zynq-7000
• Sample clocking: driven by GPSDO PPS
• Beamforming weights: updated via SPI or AXI interface from antenna control daemon
• Beam output: phase-coherent I/Q streams to transceiver RX port

Antenna array:

• 8–16 elements (typical)
• Element spacing: λ/2 at highest operating frequency
• Tuning range: 4.5–5.5 GHz (C-band example)
• Azimuth scan: 360° mechanical
• Elevation scan: 0–90° mechanical
• Gain: 15–20 dBi typical

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3. Antenna Actuation (Motorized or Phased)

For phased-array:

• Beam steering is all-electronic via FPGA weights (no moving parts)
• Slew rate: limited by FPGA update rate (~100 us per weight update)
• Typical slew rate: 10–50°/second

For motorized parabolic antenna:

• Azimuth motor: stepper or servo, 1–10°/second slew
• Elevation motor: stepper or servo, 1–5°/second slew
• Feedback: potentiometer or encoder on each axis
• Control interface: PWM (pulse-width modulation) or CAN bus

For fixed antenna:

• No actuation; beamforming or LO tuning only

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4. GNSS Receiver (Local Position & Timing)

Device: u-blox ZED-F9P or similar RTK-capable receiver

Functions:

• Provide local geodetic position (latitude, longitude, altitude)
• Provide PPS for sample clock discipline
• Provide integer-second timing and 1 MHz clock output
• Report fix quality (no fix, 2D, 3D, RTK Float, RTK Fixed)

Interface: UART (4800–460800 baud) or USB

Update rate: 1–10 Hz typical

Accuracy:

• Position: ±2 m typical (float), ±2 cm RTK Fixed
• Timing: ±50 ns PPS edge jitter typical

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Next: See Node-SoftwareProcesses-IPC for the software architecture and process model.