PA technology choices:
SiGe or GaN
The technology you choose for the FWA front end depends on the EIRP, antenna gain and noise figure (NF) needs of
the system. All are functions of beamforming gain, which is a function of the array size. Today, you can choose between
a SiGe or GaN front end to achieve your desired system needs.
In the U.S., the Federal Communications Commission (FCC) has set high EIRP limits for 28GHz and 39GHz spectrum,
as shown in the following table.
FCC Power Limits for 28GHz & 39GHz Bands
To achieve 75dBm EIRP with a uniform rectangular array, the PA power output required per channel reduces as the
number of elements increases (i.e., the beamforming gain increases). As shown in the below figure, as the array size
gets very large (>512 active elements), the output power per element becomes small enough to use a SiGe PA, which
could then be integrated into the core beamformer RFIC.
Tradeoffs Between the Number of Antenna Array Elements and RFFE Process Technology
As you can see from the table below, a SiGe PA can achieve 65dBm EIRP using 1024 active channels. However,
by using GaN technology for the front end, the same EIRP can be achieved with 16x fewer channels.
| 9 |
#4
