include video, external, and frequency mask triggers (FMT). A user-specified pre-trigger capture
length enables the capture of I/Q data both before and after the trigger event. After the I/Q data
is captured, it is transferred to the PC at approximately 200 MB/s. This new function is available
through the application programming interface (API). See the API manual for more information.
The Spike software also includes this new 250 MSPS sample rate for short captures in Zero Span
mode.
Please note that the video trigger in this mode is happening in the FPGA on partially filtered data.
An additional FIR filter on the PC will attenuate out-of-band signals and noise that may have
contributed to the video trigger event.
2.6.6 Internal GPS and Time Stamping
The internal GPS, when the antenna is connected and GPS signal is present, synchronizes the
OCXO to typically within a part per billion after about 10 minutes. The pulse-per-second (PPS)
signal also generates an automatic internal trigger that is used to time stamp I/Q data in all I/Q
acquisition modes.
3 Understanding the SM-series Hardware
3.1 Highlights
All SM series analyzers use an ultra-low phase noise 100 MHz OCXO, which is multiplied and
filtered to generate a clean 1 GHz reference. The Local oscillator (LO) uses this 1 GHz reference
in a translation loop architecture, providing very low close-in phase noise with considerably lower
spurious than a DDS.
The SM series has been designed to have high IP3 and low DANL at all input levels, giving users
the ability to monitor the spectrum at full sensitivity without worrying about overdriving the front
end or generating excessive intermodulation products.
The hardware completely reconfigures the LO, RF, and FIR correction filters in under 20
microseconds, with a minimum frequency step time of 120 microseconds. The remaining 100
microseconds, when used to collect and process a 160 MHz patch of spectrum, provide a 2 GHz
sweep in under 2 ms, or over 1 THz/sec.
Continuous THz/s sweep rates enable the analyzer to monitor spans larger than 160 MHz,
hundreds or thousands of times per second. For example, using a 30 kHz RBW, a user can sweep
700 MHz to 2700 MHz, 500 times per second.
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