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tinySA Ultra mode

During normal low input mode a low pass filter at the input ensures the absence of mirror and spur signals but this also limits the maximum usable frequencies to the pass-band of the low pass filter (approx 800MHz) . When this low pass filter is removed the first mixer can be used to very high frequencies but next to the wanted mixing products also various mirrors and spurs will be generated. Using a special algorithm requiring multiple measurements at differing frequencies, similar to what is used in the Signal Hound USB spectrum analyzers, it is possible to eliminate most of these mirrors and spurs for signals that are present long enough to be measured multiple times. Very short or complex signals and wideband signals (wider then 1MHz) will not work well with the mirror and spur elimination algorithm.

In Ultra mode the input low pass filter is automatically enabled for all frequencies within the pass-band of the low pass filter (up to a maximum of 750MHz). For higher frequencies the low pass filter will be bypassed and the measurement will be slower due to the multiple measurements per frequency required for the mirror and spur elimination algorithm.

Next to the mirror and spur elimination algorithm it is also possible to remove mirrors and spurs by using an external pre-selector that only passes a limited frequency band to the input. A practical example of such a pre-selector is a Wi-Fi band filter or an antenna with limited bandwidth. For instance, using an antenna tuned to the WiFi band is sufficient to remove most spurs and mirrors and enables faster measurement and catching short transmissions for consolidation in a max-hold mode to see the Wi-Fi band occupation.

With the input low pass filter disabled the local oscillator (LO) will leak more into the RF input. Expect levels up to -10dBm. During normal measurements this should not be a problem but a very sensitive circuit connected to the RF input may be impacted

The maximum input frequency in ultra mode is limited to 12GHz (in the default HARMONIC 3 mode) or 20GHz (in HARMONIC 5 mode) but the maximum level calibrated frequency is 6GHz. The sensitivity reduces with increasing frequencies and is about 10dB lower above 2.5GHz and 25dB lower above 5.3GHz. The input correction table corrects for these reductions in sensitivity till 6GHz. Above 6GHz there is no frequency dependent correction and sensitivity drops quickly.

A full scan from 0Hz to 6GHz with the mirror and spur elimination algorithm activated takes almost 14 seconds.

Enabling Ultra mode has no negative impact on measurements below the ULTRA START frequency so once Ultra mode is enabled there is little reason to disable the Ultra mode but if needed this can be done also using same CONFIG/MORE/ENABLE ULTRA command. The mirror and spur elimination is automatically disabled and enabled when CONFIG/SPUR REMOVAL is set to AUTO ([A]). It can be manually deactivated if not needed when using a pre-selector by setting CONFIG/SPUR REMOVAL to OFF ([_])

To summarize the disadvantage of measuring in ultra mode:

  • Increased scan time
  • Fails to capture very short duration signals
  • Fails to capture scanning signals (e.g. from a sweeper)
  • Shows false signals when using with very complex or wide signals.
  • Higher LO leakage from RF connector

Ultra mode is disabled by default but can be enabled using the command CONFIG/MORE/ENABLE ULTRA using 4321 as the unlock code. Once enabled the ultra mode stay's enabled. Sometimes a FW update may require re-enabling. By enabling the ultra mode you acknowledge that you understand and agree with the limitations of the ultra mode.

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Page last modified on December 21, 2022, at 10:12 AM