In particular, the signal spectrum shape must fall within the limits of certain masks or clearances specified in the relevant standards, for example, ETR290 for DVB-T. The specific masks depend on the signal type and the standard.
Primarily due to nonlinearity in power amplifiers, the RF output signal contains unwanted boundary and out-of-band components, the shape of which has given rise to the term "shoulders," and which tend to compromise compliance with the clearances or masks.
How to measure shoulder attenuation
Shoulder attenuation must be measured at the power amplifier output just before the signal is sent to the antenna through the network of passive devices. Due to the power level typically available at that point, external power attenuators are necessary to adjust the level to the maximum accepted by the analyzer.
Shoulder attenuation measurements must be performed following the procedures clearly outlined in the relevant standards, such as DVB-T and ATSC. These procedures are complex and require a high-performance spectrum analyzer and highly qualified operators. The maximum peak values within the channel, depending on the signal type and the resolution filter used, channel boundaries, various values at different frequency offsets, and various mathematical operations are all necessary elements for performing this measurement.
The HD RANGER 2 and HD RANGER 3 field strength meters for DVB-T, DVB-T2 and DVB-C2 as well as their corresponding ATSC and ISDB-T variants can perform this measurement fully automatically and display it along with other relevant data such as the pilot signal level, MER, VBER, etc.
Four red markers on the screen delineate the two windows where, according to the standards, the measurements will be focused. Within these windows, two reference points will be taken, called the upper shoulder attenuation (Upp) and the lower shoulder attenuation (Low), both automatically displayed on the analyzer.
This measurement is important but time-consuming if performed with conventional spectrum analyzers.
