AN-SOF: Empowering antenna simulation, modeling, and design.
AN-SOF: Empowering antenna simulation, modeling, and design.
This 4-element biquad array resonates at 434 MHz. The wires that connect the driven element to the reflector work as a two-wire transmission line that allows us to obtain an input impedance of 50 + j0 Ohm.
It may be noticed that the polar plots are on a log scale. ARRL-style log scaling is coming in the December release of AN-SOF!
From this link > you can download 5 examples of antenna models that have less than 50 segments, so the calculations can be run with the trial version of AN-SOF:
Here is a relatively compact array of 5 square loops for 145 MHz. It does not need a matching network since the input impedance is practically 50 Ohm. Gain 12 dBi. Beamwidth 50 deg. F/B 20 dB.
2-element quad antennas are very popular due to their compact size and gain similar to a more element Yagi. In addition, they can be designed to obtain an input impedance of 50 Ohm.
This design can operate at 27.5 MHz. We have added a script that allows us to plot the gain and front-to-back ratio as a function of element spacing. See this video >.
We can see that both cannot be maximized at the same time, but it is preferable to choose the maximum F/B since the gain changes relatively little.
To create the Scilab script, we started from a basic design in AN-SOF and then exported it as a *.sce file.
Nathan Cohen in the US fractalized the quad loop based on the Minkowski square and invented an array of two elements. The biggest advantage of fractal antennas is that we get a wide bandwidth with a small size.
This simulation shows that we can almost double the bandwidth with a 3-element array. It has a reflector, a driven element, and a director. These are the results for the 20 m band (~ 14 MHz),
Quad size ~ 290 x 290 cm (0.14 x 0.14 of a wavelength)
Element spacing ~ 280 cm
450 KHz bandwidth (VSWR < 2) around 14.5 MHz
6 dBi gain
10 dB F/B
80° beamwidth
Vertical polarization
It has less gain than could be achieved with a 3-element Yagi, but it has a relatively large bandwidth and is a very compact antenna. It does not need a matching circuit and its impedance is 50 Ohm at resonance, so it could be fed directly through a 50 Ohm coax.
