Beamforming by Phased Array Antennas

In this second video of the series on beamforming, we show the time domain wave propagation for two phased array antennas at different phase differences. Thanks to the constructive and destructive interferences, the main beam of the wave is steered towards angle of interest.

See also:
Phased Array Antenna Beam Steering Animation (Beamforming)
Beamforming by Phased Array Antennas 



Antenas en fase, Antenne réseau à commande de phase, フェーズドアレイレーダー, Фазированная антенная решётка, Фазована антенна решітка, 相位陣列, Szyki fazowane, Fázisvezérelt antennarács, מערך מופע, آرایه فازی

Corner Reflector (FDTD Animation)

Two corner reflectors with two different tilt angles have been simulated for demonstrating their reflection properties. The simulations are rendered using the total-field/scattered-field finite-difference time-domain algorithm. An identical incoming plane wave in the negative vertical direction hits the corner reflectors. Although having different tilt angles, they reflect the incoming way in the same positive vertical direction. Corner reflectors are known to be retro-reflectors and consists of 2 or more mutually perpendicular and intersecting flat surfaces. They automatically reflect the waves back towards to the source. In practice, they are used for calibration purposes (e.g. meteorological radars) and range detection. Also in maritime and air navigation, they are used to mark the desired objects on the radar screen (e.g. buoys, ships, runways etc). Corner reflectors are also used to as safety reflectors for cars, bikes, traffic signs and similar devices. Here, the reflectors are in the passive mode, but can also be used in semi-active mode to enhance the directivity of dipole antennas. Basically, by placing the dipole antenna in front of a corner reflector, the combined corner-reflector dipole antenna has a better directivity.

Ground Penetrating Radar (GPR) B-Scan Collection (FDTD Animation )

Here, B-scan data collection of a simple ground penetrating radar (GPR) is animated through the use of Finite-difference time-domain (FDTD) method. The upper part of the animation shows the 2D spatial propagation of the short pulse transmitted from the antenna at different spatial locations. The transmitting antenna shoots a short electromagnetic pulse (with a central frequency of 600 MHz) into the subsurface where the relative dielectric permittivity is 4. The short pulse is reflected from the air-soil interface and then from the target embedded in the subsurface. Then, the scattered signals are recorded by the same antenna in the receiving mode. The lower part of the animation corresponds to the received signals (A-scan) at the same antenna for each of the positions. This constitutes the so-called B-scan data collection.

Ground Penetrating Radar (GPR) FDTD Animation

Finite-difference time-domain (FDTD) animation of a sample ground penetrating radar (GPR) in action. Basically, a transmitting antenna shoots a short electromagnetic pulse (with a central frequency of 600 MHz) into the subsurface where the relative dielectric permittivity is 4. The short pulse is reflected from the air-soil interface and then either the rectangular or circular targets embedded in the subsurface. Then, the scattered signals are recorded by the receiving antenna of the GPR unit. This constitutes a single A-scan for the GPR measurement. Collection of A-scans along a spatial range constitutes the so called B-scans. Depending on the reflectivity of the target and soil properties, the success of GPR detection varies.

Ground Penetrating Radar -  Propagation within the subsurface

MEEP colormap for Matlab

I have been thinking of using the colormap used in the MEEP software (an open source FDTD code) as a nice alternative to the classical Matlab colormap. Here is the short Matlab code to generate it and the resulting images:

mincolor    = [1 0 0]; % red
mediancolor = [1 1 1]; % white   
maxcolor    = [0 0 1]; % blue      

ColorMapSize = 4;
int1 = zeros(ColorMapSize,3); 
int2 = zeros(ColorMapSize,3);
for k=1:3
    int1(:,k) = linspace(mincolor(k), mediancolor(k), ColorMapSize);
    int2(:,k) = linspace(mediancolor(k), maxcolor(k), ColorMapSize);
end
meep = [int1(1:end-1,:); int2];

colormap(meep); 
colorbar

Classical Matlab colormap (jet)	MEEP colormap with ColorMapSize 64
MEEP colormap with ColorMapSize 16	MEEP colormap with ColorMapSize 4

*Images are snapshots from the FDTD simulation of a dish antenna.

Dipole Antenna Radiation

Finite-difference time-domain (FDTD) simulation of a 2 wavelengths long dipole antenna at 400 MHz in free space. The radiation pattern is very different than that of the traditional half-wavelength dipole antenna. Nulls in the broadside and endpoints are clearly visible

Dish Antenna Animation (Parabolic reflector)