So, you want to add the frequency 1.6MHz, or a sideband at 1.6 (4.6 + 1.6 =
6.2MHz)?The first is a linear mixer (resistor, say), the second is a linear multiplier.
I have no idea what you mean by audio frequency. The farthest first order sideband that can be produced is +/-20kHz. (Higher order IMD products, from a nonlinear multiplier, will give spurs at multiples and so on.)
Tim
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The process that matches your description is Frequency modulation of the RF caRRIER. Say you have an rf carrier of 4.6 Mc, and you take a 20 Kc tone and frequency modulate the carrier. And, further, you arrange the amplitude and sensitivity such that the 20 KC tone produce a deviation of 800 kc. the resultant spectra would look like:
the carrier,
surrounded on both side by 20 kc "harmonics" on both sides further there will be "harmonics" at 20 40 60 80 etc , spacing, on each side of the carrier further, they will extend + or 800 Kc on each side, 1.6 mC all together.
The amthemactical function that describes the placemt and amplitude distribution of this "harmonics" often called sidebands, are the bessel's function.
Happy modulating
marc
link to actual mixer site
BS benevolent Stuff for engineers
[...]
Furthermore, if you modulate the frequency and the amplitude at the same time, you can get very peculiar spectrum. However the 20kHz modulation is not going to produce a pure 1.6MHz tone in addition to 4.6MHz carrier.
Vladimir Vassilevsky DSP and Mixed Signal Design Consultant
I am hoping some mathematical genius can help me with this. I read of a process whereby _specific_ harmonic frequencies can be added to a fixed RF carrier by mixing it with an audio frequency. Both are initially sinewaves, of course.
What is the mathematical basis for achieving this?
As an example, say one wants to add a 1.6MHz spectral component to a fixed 4.6MHz carrier. What frequency within the audio range would achieve this, and how is it determined.
Thank you greatly for any insight on this matter.
Mark Jennings
When applied to electronic music, this was called the Chowning method.
Summary at
If you want to see a 1.6MHz sine wave and a 4.6MHz sine wave on one terminal, you can combine the two inputs with a simple resistive combiner, as has already been suggested.
No harmonics at all will be present at the output of the resistive combiner.
If you want harmonics, the two (or more) inputs must pass through a non-linear device (mixer or modulator), in which case the output (this depends on the particular mixer/modulator chosen) will consist of the original inputs plus their sum and difference frequencies, plus sums and differences of harmonics of the inputs, such as 3n+m, 2m+17n, n+4m, etc.
In theory, it doesn't matter whether the frequencies are audio or RF. In practice, the mixer must be chosen to accommodate the frequencies to be mixed.
If this sounds like what you have in mind, do a Google search on "frequency mixer."
Chuck
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1.6 MHz is not in the audio range; so, just exactly what are you trying to do?
Tam
chuck,
the non linear device ie the mixer, will produce the desired sum and difference, and then you get the inter modulation products.. I consider the IM the "bad" result and distortion. I had thought that the poster, really wanted to produce a picket fence of evenly spaced spectra, and he described what he wanted best way he could. So the mixer and IM distortion will produce sorta what the poster wants but in a "bad" way. Te relatively wide BAND FM prodUCes A PICKET FENCE SPECTRA, AT THE SPACINGS AND ....DOESNT COUNT ON THE NON LINEAR TRANSFER CURVE OF A DIODE FOR EXAMPLE.
yOU CAN GET INto A WHOLE thread on making wieband, even ly spaced and equal(almost amplitude, picket fence spectra creations.. all depends what you really want to do, and considering implementation constraints to guide the final design optimizations.
best regards, Marco
snip
You can call them IM products but they are always present in the output of a nonlinear mixer. Usually unwanted in a mixer's output, but always bad in a device intended to be linear.
I had thought that the poster,
No way of knowing the OP's intent.
Chuck
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