For a final year project at University, I need to use a GPS, Bluetooth and transceiver module. I am designing it so the antennas will be integrated with the board, none of the antennas are PCB antennas. So would be connected using SMA. I am going to place them maybe 60mm apart or 90/180 degrees apart but was wondering if this would be sufficient to avoid interference? If not, what would you recommend? I was thinking of filters as well but would like some advice as I am not terribly knowledgeable in PCB design.
PCB routing between the chip and the antenna connector must to be impedance matched, or performance will be severely degraded.
That means you need to take into account the range of operating frequencies for each connection, PCB trace dimensions, board thickness, material and dielectric constant, distance to ground plane and other traces, etc.
Texas Instruments and other manufacturers offer application notes on RF PCB design, which you should study very carefully. Make sure you understand all the considerations before attempting to lay out the board.
Thank you for your advice, I have seen the Texas Instruments notes so I will go through them again. I am placing the antennas as far apart as possible, with different polarisations. I have considered the radiation pattern, and have factored it in too. I am no longer looking into using filters for the antennas.
I have been looking into reducing noise within the circuit, so have come across placing capacitors over the VCC and GND pin of the microcontroller, and also the transmitting components (higher capacitance though). But was no sure if a capacitor should be placed over the SMA connector? I have seen some diagrams where people have done so, but I am not sure of its benefits. If anyone can advise, as this isn’t directly aimed at you I would appreciate it!
You would not put a bypass capacitor across the antenna connector. Depending on the circuit, there may be a bypass capacitor before the coupling inductor if the antenna needed power for an on-board preamp, and there may be one as part of the impedance-matching network if needed.
As for bypassing, rule of thumb is (other than following the IC datasheet recommendations) is one 100n cap from Vcc to GND at every power pin and larger (10u, 4u7, etc) near parts with intermittent heavy power draw (radios, some micros)
I would appreciate it!