Main Content


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-free zones are ranges of possible 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.


collapse all

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


Figure contains an axes. The axes with title OpenIF Spur Graph contains 40 objects of type patch. These objects represent Mixer 1, Mixer 2.

Input Arguments

collapse all

OpenIF object, specified as an object handle.

Introduced in R2011b