Free Space Path Loss

Apply free space path loss to complex signal

• Library:

• Communications Toolbox / RF Impairments

• 

Description

The Free Space Path Loss block applies a free space path loss to a complex signal. The block simulates the loss of signal power due to the distance between the transmitter and receiver. The Mode parameter indicates whether you specify the loss in decibels or as a computation that is based on distance and the RF signal frequency.

Ports

Input

In1 — Complex signal

scalar | column vector

Complex signal, specified as a scalar or column vector.

Data Types: double | single
Complex Number Support: Yes

Output

Out1 — Output signal

scalar | vector

Output signal, returned as a scalar or column vector. This output is the same dimension and data type as the input signal.

Parameters

Mode — Loss calculation mode

Decibels (default) | Distance and Frequency

Loss calculation mode, specified as one of these options.

• Decibels — The loss is specified using the Loss (dB) parameter.

• Distance and Frequency — The loss is computed using the Distance (km) and Carrier frequency (MHz) parameters.

Loss (dB) — Power loss

10 (default) | scalar

Power loss in decibels, specified as a scalar. The decibel amount shown on the block icon is rounded for display purposes only.

Dependencies

To enable this parameter, set the Mode parameter to Decibels.

Distance (km) — Distance between transmitter and receiver

0.100 (default) | scalar

Distance between the transmitter and receiver in kilometers, specified as a scalar.

Dependencies

To enable this parameter, set the Mode parameter to Distance and Frequency.

Carrier frequency (MHz) — Carrier frequency

1920 (default) | scalar

Carrier frequency in megahertz, specified as a scalar.

Dependencies

To enable this parameter, set the Mode parameter to Distance and Frequency.

Model Examples

Apply Free Space Path Loss to QPSK Modulated Signal

The model applies free space path loss to a QPSK modulated signal.

Add RF Impairments to DQPSK Signal

This model applies RF impairments to a signal modulated by differential quadrature phase shift keying (DQPSK). To demonstrate and visualize the RF impairments, levels applied in this model are exaggerated and not representative of typical levels for modern radios.

Impact of RF Effects on Communication System Performance

Use Communications Toolbox™ blocks to model thermal noise, phase noise, and nonlinearity impairments of an RF transceiver. The model measures the effects of the impairments on the bit error rate (BER) of a communications system.

Block Characteristics

Data Types	double | single
Multidimensional Signals	no
Variable-Size Signals	no

Algorithms

The free-space path loss, L, in decibels is:

L = 20log₁₀(4πR/λ).

This formula assumes that the target is in the far-field of the transmitting element or array. In the near-field, the free-space path loss formula is not valid and can result in a loss smaller than 0 dB, equivalent to a signal gain. For this reason, the loss is set to 0 dB for range values R ≤ λ/4π.

Extended Capabilities

C/C++ Code Generation
Generate C and C++ code using Simulink® Coder™.