Produce spur graph for multiband transmitter or receiver




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.

The following figure shows a spur graph for the three-mixer multiband receiver example on the OpenIF class reference page.

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 on a spur-free zone produces a tooltip, 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 possible 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 on a spurious region produces a tooltip, 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)|. The sign of ‘±' in these equations is determined by the injection type of the mixer. 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.

Input Arguments

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hif — IF planning objectOpenIF object

Intermediate frequency planning (IF) object, specified as an OpenIF object.


  • The getSpurFreeZoneData function returns the endpoints of the spur-free zones in a matrix.

  • The report method displays mixer configurations, intermodulation tables, and spur-free zone information at the command line.


  • The OpenIF class reference page contains an example that shows how to find the spur-free zones of a multiband receiver with three mixers.

  • The example Finding Free IF BandwidthsFinding Free IF Bandwidths shows how to use information from a spur graph to design a multiband receiver with spur-free zones.

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