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K-LD7 Angle Radar Integration — Design

ARCHIVED DOCUMENT

This is a historical design or implementation note, kept as a record of why the code is shaped the way it is. It describes the project as of the date in its filename and is not a guide to follow — commands, paths, and constants may no longer match the code. See the Archive index for current alternatives.

Date: 2026-03-23 Status: Exploration phase

Goal

Add an RFbeam K-LD7 24GHz FMCW radar module to supplement the OPS243-A Doppler radar. The OPS243 handles speed and spin detection. The K-LD7 provides per-target angle, distance, and magnitude data that the OPS243 cannot.

Long-term, the K-LD7 may replace the camera for horizontal angle measurement and provide distance-to-target data. This phase is data gathering only.

K-LD7 Module Overview

  • Frequency: 24 GHz ISM band (same as OPS243)
  • Modulation: FMCW (vs OPS243's CW Doppler)
  • Beam: H80° × V34° (datasheet: ±40° H, ±17° V at -3dB)
  • Measurements per target: distance (m), speed (km/h), horizontal angle (°), magnitude
  • Multi-target: PDAT returns all detected targets; TDAT returns the strongest
  • Interface: UART, 115200 baud default (even parity), up to 3 Mbaud
  • Power: 5V, 200mA
  • Range settings: 5m / 10m / 30m / 100m
  • Speed settings: 12.5 / 25 / 50 / 100 km/h (max 62 mph — below golf ball speed)
  • Angle range: -90° to +90° horizontal
  • Driver: nickovs/kld7 Python library (pip install kld7)

Known Limitations

  1. Speed aliasing (not just saturation): Max 100 km/h (62 mph). The datasheet warns that speeds above the max setting produce wrong measurements due to aliasing — not just clipped values. Golf balls at 150+ mph will report incorrect speeds. This is acceptable since OPS243 handles speed. Angle and distance should still be valid.
  2. Very few frames per shot: At 100 km/h speed setting, frame duration is ~29ms (~34 fps). A golf ball transits the 5m detection zone in ~30ms, giving only 1-2 frames per shot. PDAT (raw detections) is more reliable than TDAT (tracked target) since the tracking filter likely won't lock on in time.
  3. Horizontal angle only: No vertical angle measurement. Vertical launch angle still requires camera or estimation. A second K-LD7 mounted at 90° could provide vertical angle (future consideration).
  4. Interference potential: Both radars operate at 24 GHz. May need frequency offset via K-LD7's RBFR parameter (low/mid/high base frequency).
  5. Tracking filter limitations: Tracks only 1 target with 30m max range. For multi-target scenarios or fast transients, rely on PDAT raw data instead.

Phase 1: Test Script

scripts/test_kld7.py

Standalone script for data gathering. No integration with the server or OPS243 yet.

Behavior: 1. Connect to K-LD7 via USB serial (EVAL board) 2. Configure for golf use case (short range, max speed, both directions) 3. Stream TDAT + PDAT + RFFT frames continuously 4. Print live target data to terminal 5. Save all frames to .pkl on Ctrl+C

Configuration for golf: - RSPI = 3 — 100 km/h max speed - RRAI = 0 — 5m range (ball is close to radar) - DEDI = 2 — both approaching and receding - THOF = 10 — low threshold for sensitivity - TRFT = 1 — fast detection (ball is transient)

Output format (.pkl): 

{
    "metadata": {
        "module": "K-LD7",
        "capture_start": "<iso timestamp>",
        "capture_end": "<iso timestamp>",
        "total_frames": N,
        "params": {"RSPI": 3, "RRAI": 0, ...},
    },
    "frames": [
        {
            "timestamp": <float>,
            "tdat": {"distance": 1.23, "speed": 45.2, "angle": 3.1, "magnitude": 500},
            "pdat": [{"distance": ..., "speed": ..., "angle": ..., "magnitude": ...}, ...],
            "rfft": [[256 bins], [256 bins]],
        },
        ...
    ]
}

CLI args: - --port — serial port (auto-detect if omitted) - --range — range setting: 5, 10, 30, 100 (default: 5) - --speed — max speed: 12, 25, 50, 100 km/h (default: 100) - --baud — baud rate (default: 115200) - --no-fft — skip RFFT frames (smaller output, faster) - -o, --output — output .pkl path (default: auto-generated in ~/openflight_sessions/) - -n, --max-frames — stop after N frames (default: unlimited)

Connection: USB via EVAL board → /dev/ttyUSB* on Pi.

Datasheets

  • docs/K-LD7_Datasheet.pdf — Module datasheet
  • docs/K-LD7-EVAL_Datasheet.pdf — EVAL board datasheet

Future Phases (not in scope now)

  • Phase 2: Side-by-side capture with OPS243 — correlate K-LD7 angle data with OPS243 speed/spin data on same shots
  • Phase 3: Integration module (src/openflight/kld7/) with real-time angle injection into shots
  • Phase 4: Evaluate replacing camera with K-LD7 for horizontal angle; consider second K-LD7 for vertical