The band sideband part of the band is affected by the hardware characteristics of the RF front-end device (mainly the sideband of the filter), and its performance is worse than that of the middle part of the band.
The graph below shows the insertion loss (IL) and VSWR (VSWR) performance of a B12 duplexer at the transmit port.
In the 3GPP specification, there are also special instructions for such sidebands.
3gpp ts 36.101 v18.3.0 (2023-09) 6.2.2 ue maximum output power
There is a special note, the original text is as follows:
note 2: 2 refers to the transmission bandwidths (figure 5.6-1) confined within ful_low and ful_low + 4 mhz or ful_high – 4 mhz and ful_high, the maximum output power requirement is relaxed by reducing the lower tolerance limit by 1.5 db
When the bandwidth of the transmitted useful signal falls within 4m of the sideband of the frequency band ful low and ful high, the lower limit of the maximum transmit power can be relaxed by 15db。For example, if the upper and lower limits of class 3 power consistency requirements are +-2, it can be relaxed to +2 -35。
As shown in the figure below, that is, the effective RB falls within 4MHz from the low boundary of the B12 band, in this case, the lower limit of the maximum transmit power can be relaxed to -35db。
The same instructions apply to NR5G, e.g. 3GPP TS 38101-1 v17.0.0 (2020-12) has a similar description in the maximum transmit power requirements.