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Signal Hound BB API
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I/Q sweep lists are sequential I/Q acquisitions across a series of frequencies. Lists of up to 1200 frequencies can be provided. At each frequency, the reference level and number of samples to be collected can be configured. One measurement is referred to as a “sweep” and iterates through all configured frequency steps. Several sweeps can be queued to maintain maximum throughput.
(Example) A list of 3 frequencies is provided, 1GHz, 2GHz, and 3GHz. At each frequency 1000 I/Q samples are configured to be collected. Once configured a sweep can be performed which captures I/Q samples at the 3 frequencies, for a total of 3000 samples. If desired, N sweeps can be queued to be performed back-to-back, resulting in N * 3000 samples to be collected. By queuing the sweeps, blind time between sweeps is reduced or eliminated, improving probability of intercept and overall measurement speed.
I/Q sweep lists are advantageous when needing to acquire a discrete number of I/Q samples at several different frequencies. I/Q samples are collected at the devices native sample rate, 50MS/s for the USB SM devices and 200MS/s for the networked SM devices. The absolute fastest the SM device can switch frequencies is 120us. When I/Q capture amounts are small at each frequency, 120us frequency switch times can be achieved for a maximum of 8333.33 frequencies per second.
At each frequency, a timestamp is provided indicating the nanoseconds since epoch for the fist I/Q sample at that frequency. If the internal GPS is locked, this time is GPS time, If GPS is not locked, system time is provided. Regardless of GPS lock, relative timings between timestamps are highly accurate through use of internal device counters.
See the following functions for more information.
smSetIQSweepList***
smIQSweepList***
While the user can specify an arbitrary number of samples at each frequency, the SM device is internally limited to multiples of 2048 samples. For this reason, it is optimum to round up to the next multiple of 2048, which will not affect acquisition speed and reduce the number samples discarded.
Maximum sweep speed occurs when at most N samples are requested at each frequency. For the USB SM devices, N is 2048 samples, and for the networked devices, N is 6144 samples. When <= N samples are requested, the device will step at the maximum rate of 8333.33 frequencies per second. This equates to 333GHz of spectrum coverage per second for the USB SM devices and 1.333THz of spectrum coverage per second for the networked SM devices.