User's Manual

LISA-U1/LISA-H1 series - System Integration Manual
3G.G2-HW-10002-2 Advance Information Design-In
Page 97 of 116
 Do not place antenna in close vicinity to end user since the emitted radiation in human tissue is limited by
S.A.R. regulatory requirements
 Do not use directivity antenna since the electromagnetic field radiation intensity is limited in some countries
 Take care of interaction between co-located RF systems since the GSM transmitted power may interact or
disturb the performance of companion systems
 Place antenna far from sensitive analog systems or employ countermeasures to reduce electromagnetic
compatibility issues that may arise
2.4.1 Antenna termination
The LISA-U1/LISA-H1 series modules are designed to work on a 50  load. However, real antennas have no
perfect 50  load on all the supported frequency bands. Therefore, in order to as much as possible reduce
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 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 54 shows an example of this measurement:
Figure 54: |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 55 shows comparable measurements performed on a wideband antenna. The termination is better, but
the size of the antenna is considerably larger.