Specifications

LEON-G100/G200 - System Integration Manual
GSM.G1-HW-09002-C Preliminary Design-In
Page 61 of 75
For integration observe these recommendations:
Ensure 50 Ω antenna termination, minimize the V.S.W.R. or return loss, as this will optimize the electrical
performance of the module. See section 2.4.1
Select antenna with best radiating performance. See section 2.4.2
If a cable is used to connect the antenna radiating element to application board, select a short cable with
minimum insertion loss. The higher the additional insertion loss due to low quality or long cable, the lower
the connectivity
Follow the recommendations of the antenna manufacturer for correct installation and deployment
Do not include antenna within closed metal case
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
LEON-G100/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. Therefore, in order to as much as possible reduce performance
degradation due to antenna mismatch, the following requirements should 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 40 shows an example of this measurement:
Figure 40: |S11| 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
Fig 41 shows comparable measurements performed on a wideband antenna. The termination is better, but the
size of the antenna is considerably larger.