Theory of BiQuad Antenna Design (now a digital TV channel question) Jan 11, 2013 #1. Hi everyone, I'm Designing a BiQuad antenna for WiFi applications. The design and optimization are relatively simple but i need some references of the theory behind this antenna. Making your own Bi-Quad (Wi-Fi) antenna The Bi-Quad antenna is one of the handiest, cheapest and easiest to build WiFi antennas. This blog entry will explain how to easily build one like in the picture below using cheap materials and a TNC-RP (reverse polarity tiny-N) low cost Wi-Fi router connector.
$begingroup$I want to DIY a double BiQuad antenna . But I find they are different from different web. As the picture first of below, the board under the antenna is flat, but the second has two orthogonal bend. I just want high dBi and use for 5.8G wireless image transmission. Which is better ?
Biquad Antenna Calc
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The metal plane really just has the purpose of acting as a reflector – due to symmetry, the biquad has the same pattern into the 'front' and back, and adding a simple metal plane in the right distance from the antenna will make the reflections add up constructively with the 'forward' direction, thus adding a 3dB to gain (in theory).
You want an infinitely sized, perfectly conducting ground plane. You don't get that, but something around two times the quad side length in each direction around the driven element should do most of the work – you don't lose that much if you don't have that.
The bent 'legs' might have the purpose of electrically 'enlarging' the plane area, but they might also serve as mechanical improvements, making the ground plane more rigid.
I'd recommend simulating this stuff – OpenEMS, free as it is, already comes with a Biquad example, and you'd only need to add a reflector to that and play with the parameters.
The problem I often encounter when researching this kind of question is that many Antenna 'theory' on the internet is written by Hams that assume that SWR (standing wave ratio) is the final and best and only measure for antenna quality, totally ignoring that an impedance-matched terminator has perfect SWR; so for example, I found one source that claimed that a driven element-plane distance that would lead to destructive interference is the optimal configuration – probably just because he saw a better impedance matching that way. But that's the dominant quality of antenna discussions – based on not-really-understood measures and vague heuristics rather than actual simulation and understanding :(
Marcus MüllerMarcus MüllerHere's a calculator for the version with the bended earth plane (see LH dimension in diagram below): -
So I would contact the guy who posted this blog to get more details of the radiation pattern. I don't think anyone on here will know this without such a consulation. The blog has a comment section that appears to have been used as recently as February this year.
Andy akaAndy aka