Combining Multiple Frequencies in a system

[hkrs]

Hi,

I am having an application in which I have to combine 2 frequencies say 10 MHz and 15 MHz. (Both frequencies are modulated with FSK data). How could I implement this without any loss ?

 

[BradtheRad]

It sounds as though you want to combine the signals into one signal, but in such a fashion that allows you to separate them later? Or do you wish to transmit them in a single medium?

* Would it work to send one frequency as a positive polarity, and the other as a negative?

* Multiplexed together via high frequency carrier?

* Frequency modulated via higher frequency carrier?

* By fiber optic... One signal sent in red light, the other in orange?

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I'm only brainstorming here. I'm not saying I know how to implement each idea.

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Mixed through a resistor network, then later split up via bandpass filters?

 

[hkrs]

I am trying to implement a system in which I have say 10 devices which works in 10 different frequencies say 10 MHz, 20 MHz, 30 MHz..... 100 MHz. The system is daisy chained so that at each node (device), the generated frequency is added to incoming frequency and so on. The generated frequency is FSK modulated and transmitted at 100 Kbps. In the other end, I want to separate all the frequencies and data.

 

[FvM]

You are describing the problem with inappropriate terminology. You are not "adding frequencies", you are combining signals.

Combining signals without loss can have different meanings and should be clarified.

1. No spectral loss, the signal must not be modified by the combiner
2. No power loss, the power of each modulator channel should be transferred to the common output without level attenuation

The second specification can be possibly achieved by passive filters, but the overall effort is most likely smaller if you use e.g. lossy directional couplers and an output amplifier. It should be considered that, depending on electrical length, 100 MHz frequency range probably demands for impedance matched design.