Waveguide Slot Array Simulation
Slotted waveguide arrays consist of a number of slots
cut into the walls of a waveguide forming an arraywith the slots acting as individual radiating elements.

shown here for reasons of clarity, eventhough fullradiation pattern was calculated.

The resonant slot array employes near half-wavelength
long resonant slots as individual radiators. The arrayelements are excited in the standing wave mode, which
is formed by a short circuit end of the waveguide.
The concrete design task here is a 10-elementtransversal slot array cut into the upper wide side of aWR-51 standard rectangular waveguide. The operating
frequency is the center of the K band, 18.5 GHz. The
dimensions of the waveguide cross-section are A=0.51
inch=12.95 mm, and B=0.255 inch=6.477 mm.

Single Slot Simulation

Fig.2. Complete model of waveguide slot

Fig.1. Model of one waveguide slot – one symmetry plane

TE10 waveguide mode is excited by a coaxial probe,
modeled by a wire segment λ/4 from the waveguideend, as shown in Fig.1. Slot is cut into the waveguideat the point where surface currents would otherwise belongitudinal, at the upper side of the waveguide. Only
half of the waveguide is modeled, due to symmetry.
The complete model is shown in Fig.2.

Fig.3. Real part of the Poynting vector longitudinalcomponent along the axis of the waveguide (one slot)

The real part of the longitudinal component of thePoynting vector calculated along the axis of thewaveguide shows the transfer of power from thegenerator to the slot (Fig.3). The first marker is set tothe position of the wire-probe feeder, while the secondmarker is at the position of the center of the slot.
The radiation pattern (in dBi) of a single slot is shownin Fig.4. Only radiation pattern in half-space has been

Fig.4. Radiation pattern in half-space of a single slot

www.wipl-d.com
contactus@wipl-d.com

This model requires only 444 unknowns thanks tohigher order MoM applied in WIPL-D Pro 3D EM
Solver. The simulation of a single slot including
calculation of radiation pattern in 32761 directions andnear field in 209 points took 3 seconds on an Intel(R)Core(TM) i7 Quad CPU with 3.07 GHz clock.

which are expected since distance between arrayelements is one guide-wavelength.

Waveguide Slot Array Simulation

Fig.6. Real part of the Poynting vector longitudinalcomponent along the axis of the waveguide (array)

Fig.5. 10-element slot array model – one symmetry plane

The 10-element model is built by using the single slot
model and applying a single Copy operation to create
the other 9 array elements. The slots are positioned
periodically at the points where surface currents would
otherwise be longitudinal, at the upper side of thewaveguide, one guide-wavelength apart. This distanceenables in-phase excitation of all slots.
The real part of the longitudinal component of thePoynting vector calculated along the axis of the
waveguide shows the transfer of power from thegenerator to the slots, with a part of power being
radiated at each slot (Fig.6). The markers designate thepositions of the generator and the fifth slot.
The radiation pattern (in dBi) of the slot array isshown in Fig.7. The gain is 14.8 dBi and the radiationis broadside, with two pronounced grating lobes,

Fig.7. Radiation pattern of the array

The model of a 10-element slot array takes only 2154
unknowns (around 35 MB of RAM) for rigorous
MoM simulation. The complete simulation, withcalculation of radiation pattern in 32761 directions andnear field in 470 points is done in 13 seconds on thesame Core i7 CPU.

Fig.8. Near field in front of slots in case of 10-element array

www.wipl-d.com
contactus@wipl-d.com