Help Page for
Ian's Phased Array Intensity
Polar Plot Demo Program
(Version 5.2 10/04/17 for drop down menus. ok. )
What does this progam do?
This program plots the rms intensity of a phased
array radar beam
with the specified parameters.
**
If you start with the page load form parameter defaults , and vary
the element spacing, or the wavelength values by clicking on the [-] [+] buttons to increase or decrease these
values
, the beam shape plot changes in interesting ways. **
You can also increase or decrease the beam direction angle in the same way, which will sweep the beam shape.
What is a Radio/Radar Phased Array?:
This program plots the rms intensity of a phased array radar beam
with the specified parameters.
A phased array is an array of ariels (usually dipoles) that transmit
a radio/radar signal with a electronically controlled phase shift
at each ariel element of the array.
The radio waves transmitted from each ariel element add up in
the free space infront of the array (that means everywhere the beam goes)
as radio waves do.
The effect of them adding up is like a ripple tank.
At some places the transmitted waves cancel, and at some points
they reinforce.
If the radio signals to each element of the array are controlled correctly
they can form a useful pattern, which in this case is a directed beam
of radio waves.
This can be suitable for radar applications, which require a beamed radio signal.
It is possible to
sweep the radar/radio beam by shifting the phase difference
of the signals to each ariel array element, which allows a radar system to
scan the area it is looking at without actually mechanically moving the arie
system. This means it can be done fast and under electronic control.
This program plots the rms intensity at (notionally) infinity
for a straight n element dipole phased array, with the specified swept
phase angle.
What is a Polar Plot?
A polar plot is a graph where the value to be graphed is represented by the radial distance
of the graph line from the plotting center, against the angle, which is the value it is to be graphed against.
In this case the radial distance is the rms intensity of the beam at (notionally) infinity for the
phased array beam, against the angle from the array for that part of the beam.
What this means is that the radial distance on the graph is the intensity
of the radio signal quite far out from the phased array ariels, along the angle on the graph.
If you think, doesn't the beam get weaker as it gets further away? The answer is yes,
and what this progam plots is the relative intensity of the beam signal at various different
angles.
This relative intensity pattern is the same at all distances significantly away from
the phased array, even though the beam signal intensity gets less as it gets further out.
Plotting Variables:
The variables that control the beam shape are are the number of array elements,
and the required beam direction (degrees).
The shape of the beam is controlled by the ratio of the wavelength
to the element spacing.
All of these can be specified, see below.
Input Form Values:
Beam Angle (degrees): This is the angle of the beam (to the right) to be specified by the phase of the signals sent to the array ariel elements.
Number of Array Elements (1-10): This is the number of dipole array elements in the array.The more of them there are the sharper/more focussed the
beam can be, if the element spacing to wavelength ratio is correct.
Element Spacing (dimensionless units): This is the (notional) spacing between the dipole ariel elements in the array. The assumption is that they are equally spaced
along a straight line.
Wavelength (Lambda) (dimensionless units): This the (notional) wavelength of the radio waves being generated.
The reason the element spacing values and Wavelength values are dimensionless is that the beam pattern is solely controlled by the ratio
of these two values, and so the actual units don't matter for the sake of calculating the plot.
Plotting Color: You can select the color of the plot with this; it has a drop down menu.
Plot the Beam RMS Beam Intensity Pattern Button: Click here to plot the pattern after you have selected/input the values you want in the above
form fields.
If you click on the [-] or [+] buttons the increase or decrease the values in the form, the beam pattern will automatically redisplay.