The emissions masks dialog window is designed to define parameters of the unwanted emission of the transmitter.
Figure 360: Example on how to edit a function (i.e. like spectrum emission mask)
An emissions mask function is always defined by a sequence of triplets (x, y = f(x), z) displayed in the emissions mask grid where f(x) stands for the relative emitted power (in dBc) at frequency offset x (expressed in MHz), measured in a reference bandwidth z (expressed in kHz). A full description of the calculation of total emissions is available in ANNEX 6:.
Two curves are displayed:
- Red curves: It shows the actual curve of the mask, for given reference bandwidth z, that is:
y = f(x) (Eq. 72)
- Blue curves: it shows the curve normalized in a reference bandwidth of 1 MHz, that is:
y = f(x) + 10log(1000/z) (Eq. 73)
The blue curve is aimed to detect potential discontinuities in the definition of transmission mask, and is also the one which is used in actual simulations when integrating the total power of unwanted emissions, in order to overcome possible differences of victim and interferer bandwidthes.
The value of reference bandwidth is therefore extremely important as it has direct impact on the calculated unwanted emissions level. Unless the reference bandwidth is separately defined as a part of mask definition (e.g. for mask definitions in radio equipment standards, etc), you are advised to enter the total emissions bandwidth of interefering transmitter (i.e. channel width) as value for reference bandwidth.
The following functions are available in the dialog window:
- Add: To add a triplet click on Add button. Triplets are then automatically sorted by increasing x value,
- Delete: To suppress a triplet at marker position, click on Delete button;
- Sym: To symmetrize a transmission mask, click on Sym button, this results in generating for each triplet (x, y, z) a symetric triplet (-x, y,z) if it doesn't already exist;
- Load: click on the Load button to load a mask from an external text file. This file must contain one triplet (x, y, z) per line, with values TAB separated;
- Save: If you want to save the defined mask for future re-use or sharing with other users, click on Save button to export the defined mask grid to a text file.