Error! No text of specified style in document. - System Integration Manual
CDMA-2X-11004-P1
Objective Specification
Design-In
Page 63 of 79
Place antenna far from sensitive analog systems or employ countermeasures to reduce
electromagnetic compatibility issues that may arise
74.2.1
Antenna termination
The Error! No text of specified style in document. modules are designed to work on a 50
load.
However, real antennas have no perfect 50
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, 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 15 shows an example of this measurement:
Figure 15: |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 16 shows comparable measurements performed on a wideband antenna. The termination is
better, but the size of the antenna is considerably larger.
Figure 16: |S
11
| sample measurement of a wideband antenna
