Traveling wave slotted guide array ? with frequency dependant squint angle

Generic image of a Traveling wave slotted guide array antenna

Generic image of a Traveling wave slotted guide array antenna

We recently added the Traveling wave slotted guide array to the Antenna Magus database. Compared with the previously added Resonant waveguide slot array, I must say I was impressed and amazed with some of the Traveling wave antenna?s advantages. It can handle higher power and operates over a much wider band (up to 25% bandwidth).

The slots of the Traveling wave slotted guide array are spaced equally on either side of the guide center moving further apart towards the load. Where the spacing is less than ?g/2 (and ?g is the wavelength in the waveguide), the beam squints towards the source, while a larger spacing results in a squint towards the load. Because the progressive phase shift between slots changes with frequency, the squint angle changes with frequency.

The image below shows the gain patterns of a 100 slot Traveling wave slotted guide array designed at 7 GHz, simulated over a wide frequency range. Note a total of 7 degrees shift in squint angle over a 10% change in center frequency. Being very popular for tracking radar applications, this could create a problem. For example when using a frequency sweep while tracking a small moving target the transmitted signal is constantly looking in different angles. I guess knowing the frequency of the returned signal; one can determine the squint angle and then calculate the exact position of the target? Maybe this can actually be seen as a useful ?feature? of this antenna.

Showing squint angle change for different frequencies.

Showing squint angle change for different frequencies.


Typical S11 of the Traveling wave slotted guide array

Typical S11 of the Traveling wave slotted guide array


Author: Robert Kellerman

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