designing trace anthtenas for 2 sets of rf rx+ tx

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)

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

THANKS

• English may not be your first language, but you can still follow two simple rules: Capitalize the first letter of each sentence, and capitalize the word "I". You don't need to know any grammar or vocabulary to follow these rules, so there is no excuse for not doing so. Jun 7, 2016 at 12:47
• You are right no excuse for that, edited my question.
– itai
Jun 7, 2016 at 12:54

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.

• Thanks for your comment, when you say "do not send and receive" do you mean in the mcu code, or do i need some kind of a "relay" circuit, 1. what will happens if i do? (i will just recive hat i transmitted? ill it damage the modules), will it be better to have 2 anthennas? one for 315mhz and one ofr 433mhz, that share rx+tx? thanks
– itai
Jun 7, 2016 at 20:15
• Yes, you should prevent that in the software. When you send and receive at the same frequency at the same time, you will receive what you just send. That is useless ! The modules will not be damaged, it will just not work. More antennas is always better. 2 Antennas, one for each frequency is a good idea. Still I would advise to use the 1 nF capacitors I suggested just to prevent any damage to the modules. Jun 7, 2016 at 20:30
• Thanks! we talking about 4 capacitors and 2 antennas 433mhz and 315 right? every module need it on capacitor? or every antenna can have one capacitor?
– itai
Jun 7, 2016 at 21:53
• Yes, 4 capacitors, one antenna for 315 MHz, one for 433 MHz. Jun 8, 2016 at 7:38