LEON-G100 / LEON-G200 - System Integration Manual
GSM.G1-HW-09002-G3
Preliminary
Design-In
Page 94 of 125
2.4.1
Antenna termination
LEON-G100 / LEON-G200 modules are designed to work on a 50
Ω
load. However, real antennas have no
perfect 50
Ω
load on all the supported frequency bands. To reduce as much as possible performance
degradation due to antenna mismatch, the following requirements should be met:
Measure the antenna termination with a network analyzer: connect the antenna through a coaxial cable to
the measurement device, the |S
11
| indicates which portion of the power is delivered to antenna and which
portion is reflected by the antenna back to the modem output
A good antenna should have a |S
11
| below -10 dB over the entire frequency band. Due to miniaturization,
mechanical constraints and other design issues, this value will not be achieved. A value of |S
11
| of about
-6 dB - (in the worst case) - is acceptable
Figure 51 shows an example of this measurement:
Figure 51: |S
11
| sample measurement of a penta-band antenna that covers in a small form factor the 4 GSM bands (850 MHz, 900
MHz, 1800 MHz and 1900 MHz) and the UMTS Band I
Figure 52 shows comparable measurements performed on a wideband antenna. The termination is better, but
the size of the antenna is considerably larger.
Figure 52: |S
11
| sample measurement of a wideband antenna