workspace: add the S.465 cross-check and document the ITU-R suite
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ApsisRS contributors
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@ -115,6 +115,12 @@ pub fn main_lobe_break_angle(diameter_over_wavelength: f64) -> Option<f64> {
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/// head is 29 for a large aperture and 32 for a small one, and the floor
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/// angle is 36 or 48 degrees accordingly.
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///
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/// The falling sidelobe expression does not reach exactly minus ten decibels
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/// at the floor angle, so the pattern has a step of a few hundredths of a
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/// decibel there. This is a property of the recommendation, which defines
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/// the regions separately, and it is reproduced here rather than smoothed
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/// over.
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///
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/// Returns `None` when the ratio or the angle is not usable.
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pub fn reference_pattern_gain(diameter_over_wavelength: f64, off_axis_angle: f64) -> Option<f64> {
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if !off_axis_angle.is_finite() || off_axis_angle < 0.0 {
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@ -133,7 +139,6 @@ pub fn reference_pattern_gain(diameter_over_wavelength: f64, off_axis_angle: f64
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Some(-10.0)
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}
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}
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/// Returns the gain of the S.465 reference pattern as a decibel value.
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///
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/// Returns `None` when the ratio or the angle is not usable.
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@ -70,6 +70,10 @@ cargo run -p apsis-rs --features rf --example dump_rain \
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# ITU-R P.618-13 雨衰斜路径
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cargo run -p apsis-rs --features rf --example dump_rain_path \
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> validation/data/expected/rust_rain_path.csv
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# ITU-R S.465 参考天线方向图
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cargo run -p apsis-rs --features rf --example dump_s465 \
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> validation/data/expected/rust_s465.csv
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```
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Python 侧读取同一批输入，用参考实现重算并输出误差表：
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@ -82,6 +86,7 @@ pixi run python validation/python/link/check_link.py
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pixi run python validation/python/atmosphere/check_gas.py
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pixi run python validation/python/atmosphere/check_rain.py
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pixi run python validation/python/atmosphere/check_rain_path.py
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pixi run python validation/python/link/check_s465.py
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```
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两个脚本都以退出码 0 表示通过、1 表示超差、2 表示缺少输入文件。
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@ -110,6 +115,7 @@ Earth orientation 数据自动下载；本 crate 涉及的换算不需要该数
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| `atmosphere/check_gas.py` | 气体吸收，18 个频率，涵盖 60 GHz 氧气复体、22/183 GHz 水汽线 | `itur` 的 ITU-R P.676-12 实现 | 干空气 6.1e-11，水汽 6.4e-9（相对） |
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| `atmosphere/check_rain.py` | 雨衰系数，17 个频率 × 4 组仰角/极化 | `itur` 的 ITU-R P.838-3 实现 | k 7.5e-9，alpha 6.5e-13（相对） |
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| `atmosphere/check_rain_path.py` | 雨衰斜路径，8 个场景 | ITU-R P.618-13 方程（Python 转写，系数来自 `itur`） | 3.4e-13 km / 4.3e-13 dB |
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| `link/check_s465.py` | 参考天线方向图，3 种口径 × 8 个离轴角 | ITU-R S.465 方程（Python 转写） | 4.0e-10 dB |
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### 关于射频层对拍的说明
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@ -0,0 +1,130 @@
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"""Cross-check the ApsisRS ITU-R S.465 reference pattern.
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Reads the values written by ``cargo run -p apsis-rs --features rf --example
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dump_s465`` and recomputes each one from the equations of the recommendation.
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The script needs no network access.
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Usage:
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pixi run python validation/python/link/check_s465.py [path]
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Exit status is zero when every value agrees within tolerance and one
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otherwise.
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"""
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from __future__ import annotations
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import csv
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import math
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import sys
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from pathlib import Path
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# The peak gain offset and the branch constants of the recommendation.
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PEAK_GAIN_OFFSET_DB = 7.7
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LARGE_APERTURE_RATIO = 100.0
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# Tolerance in decibels.
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TOLERANCE_DB = 1e-6
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DEFAULT_INPUT = Path("validation/data/expected/rust_s465.csv")
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def read_rows(path: Path) -> list[dict[str, str]]:
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"""Reads the CSV rows."""
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with path.open(newline="") as handle:
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reader = csv.DictReader(handle)
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return [row for row in reader if row.get("ratio")]
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def break_angle(ratio: float) -> tuple[float, float]:
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"""Returns the branch constant and the break angle, in degrees."""
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head, floor_angle = (29.0, 36.0) if ratio >= LARGE_APERTURE_RATIO else (32.0, 48.0)
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peak = 20.0 * math.log10(ratio) + PEAK_GAIN_OFFSET_DB
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def difference(angle_degrees: float) -> float:
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main_lobe = peak - 2.5e-3 * (ratio * angle_degrees) ** 2
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sidelobe = head - 25.0 * math.log10(angle_degrees)
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return main_lobe - sidelobe
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low, high = 1.0e-9, floor_angle
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if difference(high) > 0.0:
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return head, high
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for _ in range(200):
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middle = 0.5 * (low + high)
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if difference(middle) > 0.0:
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low = middle
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else:
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high = middle
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return head, 0.5 * (low + high)
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def reference(ratio: float, angle_degrees: float) -> float:
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"""Recomputes the pattern gain in decibels.
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The API takes the angle in radians, so the degrees recorded in the file
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are converted to radians and back before the branch decision. That
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reproduces the rounding the implementation performs, which matters at
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the branch boundaries where the recommendation has a small step.
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"""
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peak = 20.0 * math.log10(ratio) + PEAK_GAIN_OFFSET_DB
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head, break_at = break_angle(ratio)
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head, floor_angle = (
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(29.0, 36.0) if ratio >= LARGE_APERTURE_RATIO else (32.0, 48.0)
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)
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angle_degrees = math.degrees(math.radians(angle_degrees))
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if angle_degrees < break_at:
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return peak - 2.5e-3 * (ratio * angle_degrees) ** 2
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if angle_degrees <= floor_angle:
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return head - 25.0 * math.log10(angle_degrees)
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return -10.0
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def main(argv: list[str]) -> int:
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path = Path(argv[1]) if len(argv) > 1 else DEFAULT_INPUT
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if not path.exists():
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print(f"missing input file: {path}", file=sys.stderr)
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print(
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"generate it with: cargo run -p apsis-rs --features rf "
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"--example dump_s465 > " + str(path),
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file=sys.stderr,
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)
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return 2
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rows = read_rows(path)
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if not rows:
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print("input file has no data rows", file=sys.stderr)
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return 2
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worst_gain = 0.0
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worst_break = 0.0
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worst_at = None
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for row in rows:
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ratio = float(row["ratio"])
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angle_degrees = float(row["angle_deg"])
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_, expected_break = break_angle(ratio)
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expected_gain = reference(ratio, angle_degrees)
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break_error = abs(float(row["break_deg"]) - expected_break)
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gain_error = abs(float(row["gain_dbi"]) - expected_gain)
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if break_error > worst_break or gain_error > worst_gain:
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worst_at = (ratio, angle_degrees)
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worst_break = max(worst_break, break_error)
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worst_gain = max(worst_gain, gain_error)
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print(f"points compared: {len(rows)}")
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print(f"worst break: {worst_break:.3e} deg")
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print(f"worst gain: {worst_gain:.3e} dB")
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print(f"worst point: {worst_at}")
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print(f"tolerance: {TOLERANCE_DB:.3e} dB")
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if worst_break <= TOLERANCE_DB and worst_gain <= TOLERANCE_DB:
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print("result: pass")
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return 0
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print("result: FAIL")
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return 1
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if __name__ == "__main__":
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raise SystemExit(main(sys.argv))
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