Reduce the wifi antenna size
www.bbtantenna.com | 2010-8-9 11:05:40
In many cases, to reduce the wifi antenna footprint, we often need to reduce the size of the wifi antenna. So how to reduce the wifi antenna size of the case, the wifi antenna can still produce accurate resonance do? This is the issue discussed below.
A less than 1 / 4 wavelength wifi antenna is presented in multiples of capacitance. This is because it does not produce resonance and synthesis of its current and voltage phase relationship with the capacitive circuit is similar to the reason the phase relationship. So, we can add an inductor in the wifi antenna to make the wifi antenna to resonance.
Figure 1 is a dipole wifi antenna, the wifi antenna's arms less than 1 / 4 wavelength, then we can access in the arms, respectively, the wifi antenna produces a resonant inductor. The two inductors installed in proximity to the wifi antenna terminal position about a few centimeters at both ends than the mounted arm better, both large and small inductor can be obtained by experiment. For example, we can pass the test wifi antenna VSWR to get the right to install a large amount of low inductance.
To a length of wire wound into a half-wavelength spiral form, the effect and a quarter wavelength of the wifi antenna is almost the same, this design is called helical wifi antenna. Because of this very rare to find a matching wifi antenna transmission cable, so this wifi antenna is used in the device without transmission lines, such as mobile phones and other handheld wireless radio.
Usually we say 1 / 4 wavelength whip wifi antenna to wifi antenna. This wifi antenna is also a small wireless transceiver devices mostly use a kind of wifi antenna. In practice, due to size constraints, the length of the wifi antenna are always made of less than 1 / 4 wavelength, so to add the wifi antenna inductance, inductance of load in three ways: 1, bottom loading, 2, central load, 3, top loading, shown in Figure 2. Loading each has its pros and cons, from a mechanical point of view, the bottom of the load is ideal, but this way the radiation resistance of load is low and because most energy is radiated from the loading coil, so efficiency is relatively low.
The radiation resistance of the central load will increase, but in this case would have to produce a greater resonant inductor, the location of the more loaded up, the greater the required inductance. Top loaded wifi antenna rare, it is because inductor coil heavy the entire structure will become unwieldy, the wifi antenna's mechanical strength is difficult to be guaranteed. Consider the various factors from the central loaded wifi antenna is the best.
Vertical erection of the whip wifi antenna can only receive the vertical polarized wave, but sometimes we can put 1 / 4 broadcast wifi antenna made of a long combination of vertical and horizontal structure of the wifi antenna combination.
That both receivers can receive the vertical polarized wave has horizontal polarization wave, in which case, we may be made of the vertical part of the length greater than 1 / 4 wavelength, the wifi antenna was inductive, then the top of the wifi antenna wire with a cross section with the vertical wifi antenna to form a capacitor Ershi resonance occurs.
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