mapoet/lfmf

Low Frequency / Medium Frequency (LF/MF) Propagation Model

Low Frequency / Medium Frequency (LF/MF) Propagation Model

This code repository contains an the NTIA/ITS implementation of the Low Frequency / Medium Frequency (LF/MF) Propagation Model. LF/MF predicts basic transmission loss in the frequency range 0.01 - 30 MHz for propagation paths over a smooth Earth and antenna heights less than 50 meters.

Inputs

Variable	Type	Units	Limits	Description
h_tx__meter	double	meter	0 <= h_tx__meter <= 50	Height of the transmitter
h_rx__meter	double	meter	0 <= h_rx__meter <= 50	Height of the receiver
f__mhz	double	MHz	0.01 <= f__mhz <= 30	Frequency
P_tx__watt	double	Watt	0 < P_tx__watt	Transmitter power
N_s	double	N-Units	250 <= N_s <= 400	Surface refractivity
d__km	double	km	0 < d__km	Path distance
epsilon	double		1 <= epsilon	Relative permittivity
sigma	double	S/m	0 < sigma	Conductivity
pol	int			Polarization 0 = Horizontal 1 = Vertical

Outputs

Outputs to LFMF are contained within a defined Result structure.

Variable	Type	Units	Description
A_btl__db	double	dB	Basic transmission loss
E_dBuVm	double	dB(uV/m)	Electrice field strength
P_rx__dbm	double	dBm	Received power
method	int		Solution method 0 = Flat earth with curve correction 1 = Residue series

Return Codes

Possible return codes, including the corresponding defined constant name as defined in LFMF.h:

Value	Const Name	Description
0	SUCCESS	Successful execution
1000	ERROR__TX_TERMINAL_HEIGHT	TX terminal height is out of range
1001	ERROR__RX_TERMINAL_HEIGHT	RX terminal height is out of range
1002	ERROR__FREQUENCY	Frequency is out of range
1003	ERROR__TX_POWER	Transmit power is out of range
1004	ERROR__SURFACE_REFRACTIVITY	Surface refractivity is out of range
1005	ERROR__PATH_DISTANCE	Path distance is out of range
1006	ERROR__EPSILON	Epsilon is out of range
1007	ERROR__SIGMA	Sigma is out of range
1008	ERROR__POLARIZATION	Invalid value for polarization

Example Values

A set of example inputs and outputs are provided for testing purposes. This is not a comprehensive validation test set. The test set can be found in LFMF_Examples.csv.

Notes on Code Style

• In general, variables follow the naming convention in which a single underscore denotes a subscript (pseudo-LaTeX format), where a double underscore is followed by the units, i.e. h_tx__meter.
• Variables are named to match their corresponding mathematical variables from their publication text.
• Wherever possible, equation numbers are provided.

Configure and Build

C++ Software

The software is designed to be built into a DLL (or corresponding library for non-Windows systems). The source code can be built for any OS that supports the standard C++ libraries. A Visual Studio 2019 project file is provided for Windows users to support the build process and configuration.

C#/.NET Wrapper Software

The .NET support of LFMF consists of a simple pass-through wrapper around the native DLL. It is compiled to target .NET Framework 4.7.2. Distribution and updates are provided through the published NuGet package.

References

• Bremmer, H. "Terrestrial Radio Waves" Elsevier, 1949.
• DeMinco, N. "Medium Frequency Propagation Prediction Techniques and Antenna Modeling for Intelligent Transportation Systems (ITS) Broadcast Applications", NTIA Report 99-368, August 1999
• DeMinco, N. "Ground-wave Analysis Model For MF Broadcast System", NTIA Report 86-203, September 1986
• Sommerfeld, A. "The propagation of waves in wireless telegraphy", Ann. Phys., 1909, 28, p.665
• Wait, J. "Radiation From a Vertical Antenna Over a Curved Stratified Ground", Journal of Research of the National Bureau of Standards. Vol 56, No. 4, April 1956. Research Paper 2671

Contact

For questions, contact Nick DeMinco, [phone], [email protected]