LISA-C2 series and FW75-C200 - System Integration Manual
UBX-13000620 - R21
Early Production Information
Design-In
Page 60 of 103
2.4.1
Antenna termination
The LISA-C200 and FW75-C200 modules are designed to work on a 50
Ω
load. However, real antennas do not
have a perfect 50
Ω
load on all the supported frequency bands. Therefore, 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. |S
11
| indicates which portion of the power is delivered to antenna and which portion is
reflected by the antenna back to the module output.
A good antenna should have an |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. An |S
11
| value of about -6 dB – (in
the worst case) - is acceptable.
Figure 32 shows an example of this measurement:
Figure 32: |S
11
| sample measurement of a penta-band antenna that covers in a small form factor the 4 bands (850 MHz, 900 MHz,
1800 MHz and 1900 MHz)
Figure 33 shows comparable measurements performed on a wideband antenna. The termination is better, but
the size of the antenna is considerably larger.
Figure 33: |S
11
| sample measurement of a wideband antenna