first commit

api/app/core/propagation.py

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+from __future__ import annotations
+
+from dataclasses import dataclass
+from math import log10
+
+from app.core.geo import GeoPoint, haversine
+
+
+@dataclass(frozen=True)
+class LinkBudget:
+    distance_km: float
+    fspl_db: float
+    diffraction_db: float
+    vegetation_db: float
+    atmospheric_db: float
+    total_loss_db: float
+    rx_power_dbm: float
+    fade_margin_db: float
+    fresnel_clear: bool
+    link_viable: bool
+
+
+def fspl(freq_mhz: float, dist_km: float) -> float:
+    if freq_mhz <= 0:
+        raise ValueError("freq_mhz must be positive")
+    if dist_km <= 0:
+        raise ValueError("dist_km must be positive")
+    return 32.44 + 20 * log10(freq_mhz) + 20 * log10(dist_km)
+
+
+def itm_loss(*args: object, **kwargs: object) -> float:
+    raise NotImplementedError("Longley-Rice ITM integration is implemented in a later stage")
+
+
+def p1812_field(*args: object, **kwargs: object) -> float:
+    raise NotImplementedError("ITU-R P.1812 integration is implemented in a later stage")
+
+
+def manual_link_budget(
+    tx: GeoPoint,
+    rx: GeoPoint,
+    tx_power_dbm: float,
+    tx_gain_dbi: float,
+    rx_gain_dbi: float,
+    sensitivity_dbm: float,
+    frequency_mhz: float,
+    diffraction_db: float = 0.0,
+    vegetation_db: float = 0.0,
+    atmospheric_db: float = 0.0,
+    misc_loss_db: float = 0.0,
+    fresnel_clear: bool = True,
+) -> LinkBudget:
+    distance_km = haversine(tx, rx) / 1000.0
+    free_space_loss = fspl(frequency_mhz, distance_km)
+    total_loss = free_space_loss + diffraction_db + vegetation_db + atmospheric_db + misc_loss_db
+    rx_power = tx_power_dbm + tx_gain_dbi + rx_gain_dbi - total_loss
+    margin = rx_power - sensitivity_dbm
+    return LinkBudget(
+        distance_km=distance_km,
+        fspl_db=free_space_loss,
+        diffraction_db=diffraction_db,
+        vegetation_db=vegetation_db,
+        atmospheric_db=atmospheric_db,
+        total_loss_db=total_loss,
+        rx_power_dbm=rx_power,
+        fade_margin_db=margin,
+        fresnel_clear=fresnel_clear,
+        link_viable=margin > 0 and fresnel_clear,
+    )