I am considering for a RFID transmitter, which just send power with no data. However, my frequency is not standard 13.56MHz not 27.12MHz, it is 27.095MHz.
Can I use the block diagram shown above? If yes, where can I get the 27.095MHz signal source?
I have two ideas now, first use a MCU and a PLL chip to derive the accurate frequency. Second, use the programmable crystal oscillator(which is also based on pll, with factory programmed) like SG8101 from epson. However, the output from SG8101 is a square wave, so I have to low pass it before it is send to amplify?
Best Answer
Inevitably, when transmitting power across a gap to an RFID device, to obtain best efficiency it is likely that you will make the transmit coil resonant (using a tuning capacitor) and similarly, you will make the RFID coil resonant also using a tuning capacitor.
The effect of "tuning" means that if you fed a square wave to the drive coil it would largely transmit a sine wave so, the process of producing a magnetic field will convert your square wave into a sine wave. There may be some other reasons to use extra filtering to improve the sine purity of course.
So, if you can make a square wave oscillator that runs at 27.095 MHz then your coil and tuning capacitor design should produce a reasonable sine wave. How pure this sine wave must be is down to you.