Finished the antenna today with the updated dimensions and I am resonant at 152.4 mhz. Checking the 2 meter portion gives me a SWR of 4.2 It was a fun build, but just curious how your guys' cube came out. The slot antenna, which has been developed for 1.3GHz by G3JVL, is an easy means of obtaining an omni- directional radiation pattern with horizontal polarization. The antenna has a gain which depends principally upon its length and is typically 5 to 9 dBi. For slots that are made to be intentional antennas, they are usually slots in a waveguide or a box. Of course this changes the radiation pattern and the impedance, and the feed is not a voltage source directly across the sides but provided by the currents in the waveguide, but the basic mechanism of how they work remains the same.
Introduction
This paper was presented at the 40th Annual West Coast VHF/UHF Conference held on May 5-7 (1995?) in Cerritos, CA. Some editing was done to make it suitable for this WEB page.
Abstract
Slot antennas can be used for fixed stations, satellite ground stations and beacons. With proper mounting, a slot antenna can also be used for ‘microwave mobile’. With a 16-slot total, the antenna can have 10-12 dBi gain.
Slot antennas can be built from surplus waveguide sections, which will give an omni-directional pattern and horizontal polarization. This paper offers a computer aided method to calculate the proper dimensions for the slots and their locations.
Slot Antenna Design
Because the antenna is of one-piece construction, it is rugged and can be built cheaply, requiring only access to a reasonably precise drill press or milling machine. (Note: A precise milling machine is almost a necessity…de W3RJW)
Getting Ready
![Antenna Antenna](https://www.scielo.br/img/revistas/jmoea/v19n3//2179-1074-jmoea-19-03-0309-gf01.jpg)
The first step in construction of the antenna is to select a section of waveguide, which covers the desired frequency. Waveguide dimensions for several microwave bands are listed in table 1. If your waveguide doesn’t match the dimensions exactly, go ahead and run the program. The program will tell you if the waveguide is too small (if you attempt to operate a waveguide below its cutoff frequency, it will have unacceptable SWR and losses)
- Antenna Theory Tutorial
- Antenna Basic Terms
- Types of Antennas
- Antenna Arrays
- Wave Propagation
- Antenna Theory Useful Resources
- Selected Reading
Slot Antenna is an example of Aperture antenna. A rectangular slot is made on the conducting sheet. These slot antennas can be formed by simply making a cut on the surface, where they are mounted on.
Frequency Range
The frequency range used for the application of Slot antenna is 300 MHz to 30 GHz. It works in UHF and SHF frequency ranges.
Construction & Working of Slot Antennas
The use of slot antennas is well understood through its working principle. Let us have a look at the structure of a slot antenna.
When an infinite conducting sheet is made a rectangular cut and the fields are excited in the aperture (which is called as a slot), it is termed as Slot antenna. This can be understood by observing the image of a slot antenna. The following image shows the model of a Slot antenna.
The working of Slot Antenna can be easily understood through Babinet’s principle of optics. This concept gives an introduction to the slot antennas.
Babinet’s Principle
Babinet’s principle states that- “When the field behind a screen with an opening is added to the field of a complementary structure, the sum is equal to the field when there is no screen”.
The above images clearly explain the principle. In all the regions, which are non-collinear with the beam, the above two screens, in figures 1 & 2, produce the same diffraction pattern.
Case 1 − Consider a light source and a conducting plane (field) with an aperture before a screen. The light does not pass through the opaque area, but passes through the aperture.
![Antenna Antenna](https://d3i71xaburhd42.cloudfront.net/6a7abaa74758ad3f85cbb47a25e15353d91dbe60/2-Figure3-1.png)
![Antenna Antenna](https://cdn.comsol.com/wordpress/2018/02/spiral-slot-antenna-geometry.png)
Case 2 − Consider the light source and a conducting plane of the size of the aperture in the previous case, being held against the screen. The light does not pass through the plane but through the remaining portion.
Case 3 − Combine these two conducting planes of both the cases and put before the light source. The screen is not placed to observe the resultant combination. The effect of screen gets nullified.
Working of Slot Antenna
This principle of optics is applied to electromagnetic waves for the wave to get radiated. It is true that when a HF field exists across a narrow slot in a conducting plane, the energy is radiated.
![Slot Antenna Slot Antenna](https://www.dxzone.com/dx32340/vhf-skeleton-slot-antenna.jpg)
The first step in construction of the antenna is to select a section of waveguide, which covers the desired frequency. Waveguide dimensions for several microwave bands are listed in table 1. If your waveguide doesn’t match the dimensions exactly, go ahead and run the program. The program will tell you if the waveguide is too small (if you attempt to operate a waveguide below its cutoff frequency, it will have unacceptable SWR and losses)
- Antenna Theory Tutorial
- Antenna Basic Terms
- Types of Antennas
- Antenna Arrays
- Wave Propagation
- Antenna Theory Useful Resources
- Selected Reading
Slot Antenna is an example of Aperture antenna. A rectangular slot is made on the conducting sheet. These slot antennas can be formed by simply making a cut on the surface, where they are mounted on.
Frequency Range
The frequency range used for the application of Slot antenna is 300 MHz to 30 GHz. It works in UHF and SHF frequency ranges.
Construction & Working of Slot Antennas
The use of slot antennas is well understood through its working principle. Let us have a look at the structure of a slot antenna.
When an infinite conducting sheet is made a rectangular cut and the fields are excited in the aperture (which is called as a slot), it is termed as Slot antenna. This can be understood by observing the image of a slot antenna. The following image shows the model of a Slot antenna.
The working of Slot Antenna can be easily understood through Babinet’s principle of optics. This concept gives an introduction to the slot antennas.
Babinet’s Principle
Babinet’s principle states that- “When the field behind a screen with an opening is added to the field of a complementary structure, the sum is equal to the field when there is no screen”.
The above images clearly explain the principle. In all the regions, which are non-collinear with the beam, the above two screens, in figures 1 & 2, produce the same diffraction pattern.
Case 1 − Consider a light source and a conducting plane (field) with an aperture before a screen. The light does not pass through the opaque area, but passes through the aperture.
Case 2 − Consider the light source and a conducting plane of the size of the aperture in the previous case, being held against the screen. The light does not pass through the plane but through the remaining portion.
Case 3 − Combine these two conducting planes of both the cases and put before the light source. The screen is not placed to observe the resultant combination. The effect of screen gets nullified.
Working of Slot Antenna
This principle of optics is applied to electromagnetic waves for the wave to get radiated. It is true that when a HF field exists across a narrow slot in a conducting plane, the energy is radiated.
The image shows a slot antenna, which explains well about its working.
Consider an infinite plane conducting screen is taken and pierced with apertures of desired shape and size and this will be the screen of slot antenna. Another screen is considered interchanging the places of aperture and screen area which is the complementary screen.
These two screens are said to be complementary as they result in complete infinte metal screen. Now, this becomes the slot antenna. The terminal impedance is quite desirable for the radiation.
Radiation Pattern
The radiation pattern of the Slot antenna is Omni-directional, just like a half-wave dipole antenna. Take a look at the following illustration. It shows the radiation pattern of Slot antenna drawn in Horizontal and Vertical planes respectively
Advantages
The following are the advantages of Slot antenna −
- It can be fabricated and concealed within metallic objects
- It can provide covert communications with a small transmitter
Disadvantages
The following are the disadvantages of Slot antenna −
- Higher cross-polarization levels
- Lower radiation efficiency
Applications
The following are the applications of Slot antenna −
Slot Antennas For Hoa
- Usually for radar navigational purposes
- Used as an array fed by a wave guide