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Graphical summary of all relevant spurs and spur-free zones




show(hif) produces a spur graph of the OpenIF object hif. The spur graph contains:

  • Vertical green bands, representing spur-free zones.

  • Horizontal colored bands, representing spurious regions.

Spur graph

Spur-free zones are ranges of possible intermediate frequencies (IF) center frequencies that are free from intermodulation distortion. Depending on the configuration of the mixers in hif, spur-free zones may not appear. Clicking a spur-free zone produces a tool tip, which displays information about the spur-free zone:

  • Min IFCF — The minimum possible IF center frequency fIF for the corresponding spur-free zone.

  • Max IFCF — The maximum IF center frequency fIF for the corresponding spur-free zone.

Spurious regions contain intermodulation products from at least one mixer. The color of a spur on the spur graph indicates which mixer generates the spur, according to the legend on the spur graph. Clicking a spurious region produces a tool tip, which displays information about the spur:

  • RF Center Freq — The RF center frequency fRF of the mixer that generates the spur

  • M, N — The coefficients in the equation |MfRF – N(fRF ± fIF)| (down-conversion) or the equation |MfIF + N(fRF ± fIF)|. Injection type of the receiver determines the sign in the equations. These coefficients refer to the particular mixing product that generates the spurious region.

  • Spur Level — The difference in magnitude between a signal at 0 dBc and the spur. If you set hif.SpurLevel to a number greater than this value, then hif does not report the region as spurious.

  • Freq Range — The frequency range of the spurious region. Choosing an IF center frequency in this range causes interference with the intermodulation product corresponding to the spur.


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Set up the object

h = OpenIF('IFLocation','MixerOutput');

Add two mixers to the system

IMT1 = [99 0 21 17 26; 11 0 29 29 63; ...
       60 48 70 65 41; 90 89 74 68 87; 99 99 95 99 99];
IMT2 = [99 0 9 12 15; 20 0 26 31 48; ...
       55 70 51 70 53; 85 90 60 70 94; 96 95 94 93 92];

Check for spur-free zones


Input Arguments

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OpenIF object, specified as an object handle.

Version History

Introduced in R2011b

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See Also