designing trace anthtenas for 2 sets of rf rx+ tx

Question

First of all forgive me for my mistakes, English is not my main language.

I want to design a custom pcb (i'm not an expert just a hobby), I have a working breadboard circuit of an micro controller and rf reciver and transmitter, MCU + 433mhz(rx) + 433mhz(tx) +315mhz(rx) + 315mhz (tx)

In order to receive rf remotes 433/315 codes and re-transmit them on demand.

My problem is that every module needs it's on antenna,

That means 4 DIFFERENT antennas.... (!!!!)

I do not want 4 spiral big antennas on m pcb, So i need to design a trace antenna on the pcb, Is it possible to combine all antennas together, Or i need to trace on the pcb 4 different antennas?

A. 4 trace anthennas (433rx+433tx+315rx+315tx)

B. 2 trace anthennas (433rxtx + 315rxtx)

C. 1 antenna (433+315) is it even possible?

As i said, i'm no an expert, what is the right approach to it, in order for: 1. good design+ good reception, 2. minimum space on the pcb (need to be small).

Will one of you professionals can guide me what length and size and how should the trace antenna supposed to look like.

Thanks allot!, Your help means the world to me.

The modules are : H3V4F 3V 433Mhz (433 RX) H34B 3v 433mhz (433 TX) H3V4E 3V 315Mhz (315 RX) H34A 3v 315mhz (315 TX)

MODULES: http://www.ebay.com/itm/3V-5V-315Mhz-433Mhz-MINI-Wireless-Transmitter-Module-Receiver-Module-Transceiver-/331680416810

RX datasheet : http://www.smiery.com/H3V%20Series_EN.pdf

THANKS

Answer 1

I think it all depends on what range / sensitivity you expect to achieve. What I mean is: combining antennas will introduce some losses and that will decrease the sensitivity of the receivers and it will decrease the power the transmitters can transmit.

A one antenna solution is possible for sure with the restriction that you do not send and receive at the same time at the same frequency. If you do not do this then I see no problem.

You're in luck that such 315/433 MHz modules are not so "properly RF designed" and you can very likely get away with a simple way of combining all the antennas. The length of the antenna should ideally also be different for 315 and 433 MHz but that doesn't mean that a 315 MHz antenna does not work at 433 MHz. It does work, it is just a little bit less sensitive.

What I suggest you try is the following, to prevent the modules damaging each others input/output I would use small capacitor in series with each input and output. A 1 nF capacitor will do I think. So: get four 1 nF capacitors and one antenna. Connect all inputs and outputs to the antenna through a 1 nF capacitor. I must emphasize that this is not the ideal solution for optimum sensitivity and range but it is cheap to try and maybe it does the job.