i have a small doubt regarding the design of a simple, linear waveguide slot array as shown in the figure i attached in the attachments. My doubt is that ... As the resonant slot antenna elements are radiating the part of the power excited the slot aperture, the input power supplied to the waveguide may not be able to travel a long distance in the slotted waveguide. Becuase, as the wave is travelling along the length of the WG, the power will be lost in the slots through radiation. Then ... i want to know.... is there any limit on the number of slot elements that could be placed??? How to decide it???
Please refer to the below mentioned image for easy understanding of my doubt.
You would normally decide the number of slots from the length of array needed to get the beamwidth you need, and the separation of the slots, which needs to be less than a wavelength to avoid grating lobes.
Read the literature about these antennas, where the question you ask is discussed in detail because that is how they work.
Either the antennas feed lines are resonant, so that the power is the same along the whole length, but the antenna is narrow-band and not steerable with frequency, or the coupling of each slot is increased along the length of the feed to account for the missing power, and the antenna can be scanned with frequency.
There is no limit to the number of slots, but for a large number of slots the feed will need to be very long and the losses in the feed will be very high. In the resonant feed, if it is very long it will be very narrow band.
It is possible to put tuning sections between the slots to reduce/increase frequency scanning or increase/reduce the bandwidth.
The number of slots ( array elements) are decided based on the required length of the array (element separation of 0.5 Lamda) that is needed to get the desired HPBW. Then the coupling to each slot is determined such that all slots radiate equally. Without considering these points one may get into a situation where there is no enough power for the last slot to be radiated.
- Badges
- Science topic
- Similar topics
- Physical Sciences
- Waves