49 lines
1.9 KiB
Rust
49 lines
1.9 KiB
Rust
//! Core radio frequency primitives.
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//!
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//! This crate holds the quantities that the rest of the radio frequency
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//! layer is written in: power, gain, and the decibel scale that both are
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//! usually quoted on, together with the two relations that every link
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//! calculation starts from, the wavelength of a frequency and the free
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//! space path loss.
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//!
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//! Units are SI throughout. Power is in watts, frequency in hertz, distance
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//! in meters, and temperature in kelvin. Decibel values are power ratios,
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//! computed as ten times the base ten logarithm of the ratio.
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//!
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//! Two conventions are worth stating because they are easy to mix up:
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//!
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//! - A decibel is a ratio between two powers. A gain expressed in `dBi` is a
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//! ratio to an isotropic radiator and one in `dBd` is a ratio to a half
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//! wave dipole, which is 2.15 dB more directive than an isotropic
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//! radiator. [`Gain`] carries the ratio and both named forms.
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//! - The free space path loss increases with frequency as well as with
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//! distance, because both the effective aperture of a fixed gain antenna
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//! and the solid angle it subtends shrink as the wavelength shortens.
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//!
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//! ```
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//! use apsis_rf::{Power, wavelength};
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//!
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//! // A noise power of -204 dBW is about 4e-21 W.
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//! let noise = Power::from_dbw(-204.0).expect("the reading is finite");
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//! assert!(noise.watts() > 0.0);
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//!
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//! // A one meter wavelength corresponds to a frequency of 299.792 MHz.
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//! let lambda = wavelength(299_792_458.0).expect("the frequency is positive");
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//! assert!((lambda - 1.0).abs() < 1e-12);
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//! ```
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#![forbid(unsafe_code)]
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#![deny(missing_docs)]
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mod decibel;
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mod free_space;
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mod gain;
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mod power;
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pub use decibel::Decibel;
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pub use free_space::{free_space_path_loss, free_space_received_ratio, wavelength};
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pub use gain::{DIPOLE_OVER_ISOTROPIC_DB, Gain, HALF_WAVE_DIPOLE_RATIO};
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pub use power::{DBM_REFERENCE, DBW_REFERENCE, Power};
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pub use apsis_core::constant::{BOLTZMANN, SPEED_OF_LIGHT};
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