# Function generator for OFDM signal

I have been simulating analog circuits where the input resembles an OFDM signal, but with lower frequencies. Right now I am generating the input signal with MATLAB. I now want to have a physical implementation of the circuit. Can anyone please suggest which function generator will be suitable for this kind of operation? To be more specific, I would like to generate a signal which is the summation of sinusoidal waves with frequencies ranging from 2MHz to 100MHz and phase of pi or -pi. And the ideal scenario would be if I can generate an analog signal based on a given digital input.

• Questions seeking recommendations for specific products or places to purchase them are off-topic as they are rarely useful to others and quickly obsolete. Instead, describe your situation and the specific problem you're trying to solve. Also, without any specification of amplitude and frequency who can guess? You need to be much more detailed about what you want despite this question probably being closed because it is a shopping question. Jul 18, 2017 at 7:02
• Thanks a lot for your response. I understand your point. However, being new to this field, it would help me a lot if someone with experience could provide some suggestions. To be more specific, I would like to generate a signal which is the summation of sinusoidal waves with frequencies ranging from 2MHz to 100MHz and phase of pi or -pi. And the ideal scenario would be if I can generate an analog signal based on a given digital input.
– Siam
Jul 18, 2017 at 7:09
• Edited the question as you suggested.
– Siam
Jul 19, 2017 at 20:49

OFDM is a very inherently digital thing.

It's technically generated by applying a DFT (discrete fourier transform, as in digital) to transmit symbol vectors (symbols==digital transmission).

Spectrally, it's an array of sinc-shaped subcarriers places such that the zeros of the spectral shape of each carrier lies on all the other carriers center frequencies.

The only way to produce such sincs is (fourier transform!) to produce coherent rectangular signals on each subcarrier of the right period.

That is 100% identical to saying that you need a digital (as in: time discrete) circuit.

So, whatever circuit produces as spectral shape that is like that of an OFDM signal is a digital circuit. You can't build an analog OFDM.

A "summation of sinusoids", as you mention in one of your comments, is not remotely similar to OFDM – neither from a spectral in-band point of view (OFDM's everything but zero between center of carriers) nor from a larger bandwidth point of view – OFDM has severe sidelobes – nor from a Peak-to-Average-Power-Ratio – OFDM is known for leading to very non-constant time-signal envelope, very much unlike your simple array of sinusoid.

And the ideal scenario would be if I can generate an analog signal based on a given digital input.

Buy or build an SDR device, and transmit digitally generated OFDM signals. That's what SDR is all about: being able to describe the analog waveform in digital domain.

• Thanks a lot for the detailed explanation. It helped me a lot.
– Siam
Jul 19, 2017 at 20:48

Sounds like you probably want a arbitrary waveform generator. This piece of equipment is sort of the inverse of an oscilloscope - you generate a waveform and load it in to the arb, and it plays it back. However, you'll need to make sure that the waveform can be looped correctly as the buffer size is limited.