IEEE Std 1631:2008 pdf free download

IEEE Std 1631:2008 pdf free download.IEEE Recommended Practice for Measurement of 8-VSB Digital Television Transmission Mask Compliance for the USA.
5.3 Required equipment
It is most convenient if the sampling devices’ output impedance and all of the equipment and connecting cables below have the same nominal characteristic impedance. Otherwise, matching transfonners must be used to obtain the high return losses required for accurate measurements. Typically. 50 devices are used for emissions measurements.
This procedure requires the following items:
a) Spectrum analyzer or other measurement instrument: Required performance: the difference in amplitude between us specitied two-tone TOl (which is sometimes rcfcrred to as 1P3) and its internal displayed average noise floor level (DANL) in a 10 kHz measurement shall be ? 110 dli. It must suppon a 10 kHz measurement (i.e.. resolution) bandwidth and be capable of measuring total average power within a designated frequency range (i.e., with band power or channel power markers). This measurement is typically called a band power measurement or a channel power measurement, Although manual corrections are straightforward. measurements are simplified if the instrument automatically corrects band power measurements for errors caused by the proximity of its own noise floor. If the instrument’s internal variable input attenuator features a  5 dli step size, no external step attenuator is required.
b) Band stop filter: Required for measuring full-service emissions; sonwlirnes required for measuring the other two masks. The band stop filter reduces the amplitude of the S-VSB signal within the transmitter’s channel while leaving the adjacent channel emissions more than 2 MHz away from the channel edge (relatively) unattenuatcd. Lowering the amplitude of the in-channel X-VSB signal prevents the spectrum analyzer from internally creating intermodulation products that will invalidate the measurement. (See 6.2.)
For full-service measurements with the spectrum analyzer performance given above, the filter should meet the specification given in Figure 18 plus the following: Input power:
? I V and be tuned to the channel under test. The filter must also he well shielded to prevent otT-air ingress in high field strength locations such as transmitter sites.
As noted in 6.3.2.2, a reduced attenuation version of the band stop filter is sufficient for
measurement of emissions to the stringent and the simple masks. An instrument with a
120 dli difference between its two-tone TOl amplitude and its 10 kHz noise floor
(sensitivity) can measure the simple mask directly.