Recently we have finished development of certain FSK remote control transmitter, working at either 433MHz or 868MHz with respective max. transmitting power +10dB provided by chip, the remote control product has been in market for months now, and can be considered a success from performance perspective.
The remote control transmitter chip we chose is Si4010 MSOP10 from SiLabs, which has ASK / FSK transmitter circuit, crystal and MCU integrated into one small cost effective chip, making it perfect for wireless transmitter solutions among 27 – 960MHz range.
Si4010 power output is a open collector output with 2 pins, and the most efficient and cost effective antenna for small handheld device like this is PCB small loop antenna, our finished transmitter circuit board is as shown below.
And we can use this single board hardware design on two products, one at 433 and the other at 868, by changing two inductor components connected to loop antenna, together with Si4010 internal capacitor parameter, the latter part can be done by software programming.
As you can see, the rectangle shape copper wire on back of circuit board, around 1mm width, is the small loop antenna we talked about, during design, we have tried our best to maximize the valid covering area of antenna, to achieve best antenna efficiency.
In the following blog series in next few weeks, we will talk about how we designed the loop antenna – the layout, the component parameter we chose together with other aspects to make sure it outputs maximum power etc.
In summary, we will try to use the common tools we can reach, together with some easy to use antenna theory and calculations, to make PCB small loop antenna that works.