phased.Radiator: what are the units of measurement of the output signal and what is the reference distance?

I'm reading the manual on phased.Radiator class from Phased Array System Toolbox. There is written:

The output of phased.Radiator represents the field at a reference distance from the element or center of the array

Can you please tell me, in what units the signal is measured here? And what is the reference distance?

Answer 1

[Honglei Chen]

The radiator applies the antenna spatial response to the signal. In the simplest form, it essentially performs the following equation

y = sum(A(theta)*s)

where A(theta) is the steering vector at the direction of theta, s is the input and y is the combined signal at theta direction. Therefore there is no reference distance involved.

HTH

Answer 2

[Jeffrey Daniels]

I had to trace the code all the way into the built-in functions to figure this out for myself.

It really depends on what type of object you are using this class to radiate. You can radiate from radio antenne with directivity, antenna arrays, underwater sources, etc. So, it really depends on how you define the 'Sensor'.

One example is for an IsotropicProjector class. You can specify the 'VoltageResponse' of the source, which is in dB re 1uPa/V. When you use the radiator object with a signal and a projection angle, assuming your signal is in V, you get uPa (linear, not in dB) out of Radiator. For the case of an Isotropic (omni directional) projector, the signal will be the same in any projection angle, unless you specify it to be baffled.

% Define Underwater Noise Source.
TVR = 150; % [dB re 1uPa/V]
projector = phased.IsotropicProjector('FrequencyRange',[0 20e3],'VoltageResponse',TVR);
projRadiator = phased.Radiator('Sensor',projector,'PropagationSpeed',1472,'OperatingFrequency',32768);
% Define voltage input.
fc = 5000; % [Hz]
A = 100; % [V]
x = A*sin(2*pi*fc*t); % [V]
x = x(:);
% [uPa] = [V] * [uPa/V]  (TVR is converted to from dB to linear inside projRadiator)
sig = projRadiator(x,[0;0]); % [uPa]
figure, plot(t,abs(sig))
% Peak sig should be about 3154 uPa for this example.
% If TVR = 120 dB, 1V in equals 1 Pa.

[Steven Bordonaro]

It seems as if the units are Pa/V if you need a TVR or 120, for 1V to equal 1 uPa.