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As an important component for wireless signal radiation and reception, antennas play a key role in wireless communications. How does the antenna convert the signal from wired to wireless? How can we design an antenna with excellent performance?
About PCB antenna
What is a PCB antenna? As the name suggests, a trace is printed on the PCB. It can be drawn as a straight trace, an inverted F-shaped trace, a snake-shaped or circular trace, etc. The length is basically a quarter wavelength. Form an antenna to radiate or receive electrical signals.
PCB antenna design
Several key performance indicators of the antenna: gain, operating frequency band/bandwidth, standing wave ratio/input impedance.
PCB antenna model
The most common structure of PCB antenna is the inverted F antenna, as shown in the figure below.
Inverted F antenna model
The length of the antenna needs to match a quarter of the free space wavelength of the transmitted signal to achieve the highest transmission and reception conversion efficiency and to better produce better input impedance. The free space wavelength of the 2.45GHz signal is 122.45mm, so the corresponding antenna length is about 30.6mm, which is the length of the inverted F part (L) of the PCB antenna.
In actual design, in order to reduce the space occupied by the antenna as much as possible, serpentine wiring is often designed. The three parameters of the antenna height (H), the distance between the feeder and the ground point (S), and the width of the serpentine trace are designed to specific simulation debugging.
Antenna snake routing
In addition to the serpentine wiring in the inverted F part, the antenna also needs a good ground plane to achieve signal radiation and reception. The length requirement of the ground plane is the same as that of the serpentine wiring part, which is one-quarter of the free space wavelength of the transmitted signal, that is, 30.6mm. Considering the actual use environment of the product, the size of the wireless module cannot be too large.
Antenna snake routing
PCB antenna performance test
We conducted simulation tests on the antenna in the simulation software (with a test base plate), and conducted actual tests on the actual antenna. The test results showed that all parameters of the antenna met the design requirements.