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Frequency conversion

Hi,

I'm not experienced in design analog circuits so I ask you some advices.

I have a sinusoidal generator (f_in) which outputs a frequency between

20 kHz and 100 kHz. A local oscillator (f_lo) could supply frequencies between 20 kHz and 80 kHz.

The goal is design a mixer with the output signal f_out = f_in - f_lo with a bandwidth of 20 kHz.

Examples:

f_lo = 20 kHz f_out = 0 kHz @ f_in = 20 kHz f_out = 20 kHz @ f_in = 40 kHz

f_lo = 80 kHz f_out = 0 kHz @ f_in = 80 kHz f_out = 20 kHz @ f_in = 100 kHz

May you point me towards the correct circuit configuration?

Thank you in advance Marco / iw2nzm

Reply to
Marco Trapanese
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What are you trying to do, exactly? Put 5 audio channels on one wire? That's an unnecessarily difficult way to do it, if so--you'll wind up with a lot of crosstalk due to mixer spurs.

Cheers,

Phil Hobbs

Reply to
Phil Hobbs

Phil Hobbs ha scritto:

Nope, just playing around a bat detector. Initially I would test the mixer with my function generator before putting up the mic, pre-amp and output amp stuff.

It would be nice a comb spectrum generator with a step frequency of 10 kHz to down-convert all ultrasonic frequency to audible (with 5 kHz apart) at one time. But this seems too complex for my skill - that is very low, indeed.

Bye Marco / iw2nzm

Reply to
Marco Trapanese

Basically, you are trying to make a mixer (in the multiplying sense of the word) for a single side band receiver.

Reply to
MooseFET

I see. Sounds like a fun project, if your microphone is up to the job. You can do this by using a sample/hold e.g. an LF398 as the phase detector, and a narrow pulse with a 10 kHz rep rate as the LO.

Cheers,

Phil Hobbs

Reply to
Phil Hobbs

How about buying another bat? It can detect the first bat.

Reply to
a7yvm109gf5d1

It seems possible in theory, but very difficult in practice, at least in the analog domain. Your sums and differences are very close together. So, you need to design ideal filters with very sharp cutoffs, or even tunable filters. It might be easier in the digital domain, with a good enough sampler.

Reply to
linnix

linnix ha scritto:

I was afraid for this. Another way - correct me if I'm wrong - is to use the super-heterodyne way or double conversion. This for the analog domain.

Anyway I have some experience with the digital stuff, so I'll consider also this option.

Thanks! Marco / iw2nzm

Reply to
Marco Trapanese

MooseFET ha scritto:

Yeah, it's true. I'll search through my radio books :)

Marco / iw2nzm

Reply to
Marco Trapanese 

--
http://www.google.com/search?hl=en&q=doubly+balanced+mixer&aq=f&oq=

JF
Reply to
John Fields

formatting link

This should help you get started.

H.

Reply to
Howard Eisenhauer

Howard Eisenhauer ha scritto:

Thank you, I run into this page time ago, but I forgot the bookmark.

Marco / iw2nzm

Reply to
Marco Trapanese

That folds all of the frequencies back and forth into a 5KHz band. This may be a good thing to do in a bat detector but isn't really what the OP asked for.

Making 8 sample and holds with a HC4051 and then picking the voltages off of them with a second HC4051 may be closer to what the OP asked for.

Reply to
MooseFET

I suspect the OP is not asking the right question Tam

Reply to
Tam

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