Design of Antennas for Handheld DVB-H ... - Lunds tekniska högskola

The result of the return loss measurement was satisfactory and it was decided that
instead of this prototype a switched monopole with two RF switches should be
built.
To verify that the switch worked correctly and to make it possible to find out how
one switch affects the characteristic of the antenna a prototype with just one
switch was designed. The RF switch is connected between the matching circuits
and the antenna element and between the matching circuits and the antenna feed it
was needed to solder to switch between the different matching circuits. This
switched monopole prototype is called switched monopole 1 from now on.
The antenna that is called switched monopole 2 is exactly the same as switched
monopole 1 besides that it has a switch before the matching circuit and it has
different values of the matching components.
The RF switch that is used for these two prototypes is an antenna switch from
Peregrine (PE4268), other switches have been tested but without satisfactory
result. The used switches need three digital control signals that could be
withdrawn from an I2C-bus that the chipset provides. The I2C-bus can be
connected to the expander MAX7313 circuit that can be programmed to provide
the desired control signals. An alternative to this solution could be if the chipset
could deliver these signals directly.
The switched monopole 1 and 2 are built with a ground plane and an antenna
element with the same size as the switched monopole described above and with
the same distance between ground plane and antenna element. In figure 4.23 a
picture is shown of the switched monopole 2.
47