Halve freq gen's 800-960MHz?

I have a Marconi FM signal generator, model TF 2013, that was designed for cell phone testing. The frequency range produced is 800-960MHz.

Can someone tell me how feasible it would be to halve the above range to 400-480MHz, perhaps by bypassing one of the mutiplier stages?

I would suppose that replacing the cystal may cause problems in other parts of the circuit.

I don't have a circuit diagram at this stage, but can get one depending on the concensus here.

Or perhaps I can find it by poking around with a DFM.

Thanks for any suggestions.

Lou

Most Marconi signal generators (I've got a couple of 2019As) use PLL synthesisers, with a VCO running at the output frequency. Changing the frequency range would involve a lot of redesign work, it's probably not worth it. You could just use a flip-flop on the output, if a square wave is suitable for you.

Leon

I would suggest that instead of halving, you mix the output with an oscillator at 1200MHz. This will drop the output range to 400 -

Pearce Consulting

Oops! Excuse my crap maths - head definitely not on straight. Mix with an oscillator at 1360MHz for signals from 400MHz to 560MHz, but remember to invert the modulation.

Pearce Consulting

In that frequency range, something like this would be cheap, assuming you can't modify the 2013: View in a fixed-width font such as Courier.

----- | | 800-960 >-+------------------| mxr |-------+ | | | ---- | ---- |splt| | | ---- | | | | --- | ----- | +--|BPF|--> out | 400-500 | vco | | --- | ----- | | | | | | ---- | | | x2 | | | ---- | | | | ---- | | +--| phi | --- | -+- | |---|LPF|----+ |BPF| +--| det | --- -+- | ----- | | | +-------------------------------+

Should be this: View in a fixed-width font such as Courier.

----- --- 800-960 >-+------------------| mxr |-----|BPF| | | | --- | ---- | | | | | | ---- | ----- |splt| | 400-500 | vco | ---- | ----- | | | | | +----> out | | ---- | | | x2 | | | ---- | | | | ---- | | +--| phi | --- | -+- | |---|LPF|----+ |BPF| +--| det | --- -+- | ----- | | | +-------------------------------+