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Two tone mixer upconverter simulation

Question asked by rfehn on Aug 31, 2003
Latest reply on Nov 4, 2003 by SERGEYTRU

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I tried to simulate an upconverter with input of 10 and 11 Mhz and a LO of 400Mhz. I would expect 2 tones of 410 and 411MHz at the RF output, but the simulation only gives 410Mhz. Why does not both tones appear in the simulation.
See the attached file.

Roy

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LLASCA_eesof Sep 2, 2003 3:02 AM
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I'm puzzled by this one myself after messing around with the file. Nothing obvious to me. I didn't inspect the circuit... but it seems odd.

After starting to compose this response I found that if I made the tones 10.5 and 11.5 MHz, I would get outputs. Not good!

Lance

"
I tried to simulate an upconverter with input of 10 and 11 Mhz and a LO of 400Mhz. I would expect 2 tones of 410 and 411MHz at the RF output, but the simulation only gives 410Mhz. Why does not both tones appear in the simulation.
See the attached file.

Roy
"
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SERGEYTRU Sep 16, 2003 7:05 AM
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This issue is a result of current implemented in Harbec fundamental frequencies search algorithm. I try to explain the problem.

Any circuit includes a set of sources of periodic signals (sources of multi-frequencies signals are represented as set of harmonical sources).
All the set is characterized by array of signal sources frequencies: Fsrc[nSrc] and array of harmonic orders of the frequencies Osrc[nSrc].
For example, if a circuit has 2 harmonic sources having frequencies 1MHz and 10MHz and orders 5 and 5, then it defined by
Fsrc[2]={1e6,10e6} and Osrc[2]={5,5}.

To find solution by HB-analysis we need to pass all the sources frequencies set to create a new set of fundamental frequencies,
any frequency of which not may be represented as linear combination of other elements of the set with integer coefficients:

Fbase[nBase], nBase<=nSrc.

So, this set of sources are characterized by 1-element array of fundamentals:
Fbase[1]={1e6} and Obase[1]={50}, which allows to define all frequency components of the sources.

For example, if a circuit has sources of 3 frequencies:

Fsrc[3]={10.001, 11, 400}
in this case number of fundamentals nBase=3 and Fbase[]={10.001, 11, 400}; Obase[]={5, 5, 5}
If now change 1st frequency by 10:
Fsrc[3]={10, 11, 400}
then nBase=2 and Fbase[]={10,11}; Obase[]={200,5}

The arrays of fundamentals are used to find a set of "balanced" frequencies for HB-analysis, which is a subset of set defined as intersection of the 2 set of frequencies:

Fbal = (Fbal src) x (Fbal base)

where "x" - used as sign of intersection of sets;
and sets of the balanced frequencies formed by signal sources frequencies and fundamental frequencies are defined as:

(Fbal src)={f=Sum(Fsrc[k]*i[k], k=1,..,nSrc)
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SERGEYTRU Nov 4, 2003 9:59 AM
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The bug has been fixed in the last release of GENESYS v.2003.10 (built after 11.03.2003)

From this version 2 algorithms of fundamental frequencies search controlled by new Harbec's keyword "basefreqssearch" were implemented.
The only in case of the keyword using, Harbec use old algorithm of fundamental frequencies search for a set of circuit signal sources, otherwise all unique base frequencies of signal sources set will be used as fundamentals.

For example, if a circuit includes the set of 4 signal sources, defined by pairs (frequency, order):

Fsrc = {(1.0e6, 3), (1.0e6, 5), (1.1e6, 5), (400.0e6, 5)} (1)

then, as default the new default algorithm will create the set of 3 fundamentals:

Ffund = {(1.0e6, 5), (1.1e6, 5), (400.0e6, 5)}      (2)

which results to using the 3D-Fourier transforms with numbers of discretes:

N3d = n[1] x n[2] x n[3],               (3)

where n[k]>2*order[k]=10, k=1,2,3; N3d >1000.

If the keyword "basefreqssearch" is used, then Harbec will use the algorithm of the fundamental frequencies search (as it was in previous versions), which will found set of 1 fundamental (1):

Nfund = {(1.0e6, 2000)}               (4)

It results to using the 1D-Fourier transforms, N1d>2*2000 = 4000.

In this case as a payment for using the 1D-FT will be generation of a huge number of incorrectly generated balanced frequencies (i.e. frequencies, which were created the only after using new set of fundamental frequencies, and not not may be created from the original signal sources frequencies and maximal harmonic and combination orders values) due to using a very small discretization frequency, are eliminated by the algorithm of balanced frequencies filtration, worked in this mode of Harbec.

The new default algorithm is independent on values of the base frequencies of the signal sources and in most cases it may be more efficient, then which uses minimization of dimension of the Fourier transform (used in all previous Harbec's versions), because it always generates exact set of balanced frequencies and therefore not uses any second filtration of the set, and for very large ratios of signal sources frequencies to fundamentals it may significantly increase Harbec's speed, because it demands less number of analyses to calculate FFT arrays: each point of the Fourier arrays = 1 circuit analysis (in frequency or time domain).
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Two tone mixer upconverter simulation

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