Introduction
As an important device for radiating and receiving wireless signals, antenna plays a key role in wireless communication. How exactly does an antenna convert a signal from wired to wireless? How to design a good performance antenna? This series of articles will take you deeper.
Details
PCB Antenna Overview
What is a PCB antenna? As the name suggests, is printed on the PCB a wire, it can be drawn as a straight line, reversed F-shaped line, snake or circular line, etc., the length of a quarter of the wavelength can basically form an antenna, the electrical signal radiation out or receive signals.
Design index
Several key performance indicators of the antenna: gain, operating band/bandwidth, standing wave ratio/input impedance. In this issue, we refer to these key parameters to see how to design a high-performance PCB antenna.
Antenna model
The length of the antenna needs to conform to a quarter of the free space wavelength of the transmitted signal to achieve the highest transmission and reception conversion efficiency, while better generating a good 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) in the PCB antenna. In practical design, in order to minimize the space occupied by the antenna, it is often designed as a snake. The three parameters of antenna height (H), distance between feeder and ground point (S) and serpentine path width are designed to the specific simulation and debugging. Due to the influence of space, they are not explained here.
In addition to the serpentine routing of the inverted F part, the antenna also needs a good ground to achieve signal radiation and reception. The length of the ground surface is required to be the same as that of the serpentine wiring part, which is a quarter of the free space wavelength of the transmitted signal, that is, 30.6mm. Considering the actual use environment of the product, the volume of the wireless module cannot be too large, so in this design, we designed the overall size of the module to be 25*18mm, of which the maximum length of the grounding surface is about 25mm (diagonal). Because the ground length cannot reach 30.6mm, the antenna performance is affected to some extent. However, if the module is welded to the test or customer baseplate, the ground of the baseplate can be used to maximize the performance of the antenna.
