adg918 Analog Devices, Inc., adg918 Datasheet - Page 12

• Manufacturer Part Number: adg918
• Description: Wideband, 43db Isolation 1ghz, Cmos 1.65 V To 2.75v, 2 1 Mux/spdt Switches
• Manufacturer: Analog Devices, Inc.

ADG918/ADG919
APPLICATIONS
The ADG918/ADG919 are ideal solutions for low power, high
frequency applications. The low insertion loss, high isolation
between ports, low distortion, and low current consumption of
these parts make them excellent solutions for many high
frequency switching applications. The most obvious application
is in a transmit/receive block, as shown in the wireless metering
block diagram in Figure 26.
Other applications include switching between high frequency
filters, ASK generator, FSK generator, and antenna diversity
switch in many tuner modules.
ABSORPTIVE VS. REFLECTIVE
The ADG918 is an absorptive (matched) switch with 50 Ω
with 0 Ω terminated shunts to ground. The ADG918 absorptive
switch has a good VSWR on each port, regardless of the switch
mode. An absorptive switch should be used when there is a
need for a good VSWR that is looking into the port but not
passing the through signal to the common port. The ADG918 is
therefore ideal for applications that require minimum
reflections back to the RF source. It also ensures that the
maximum power is transferred to the load.
The ADG919 reflective switch is suitable for applications where
high off port VSWR does not matter and the switch has some
other desired performance feature. It can be used in many
applications, including high speed filter selection. In most cases,
an absorptive switch can be used instead of a reflective switch,
but not vice versa.
WIRELESS METERING
The ADG918 can be used in wireless metering applications. It
can be used in conjunction with the ADF7020 transceiver IC for
a utility metering transceiver application, providing the
terminated shunt legs, and the ADG919 is a reflective switch
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required isolation between the transmit and receive signals.
The SPDT configuration isolates the high frequency receive
signal from the high frequency transmit.
TUNER MODULES
The ADG918 can be used in a tuner module to switch between
the cable TV input and the off-air antenna.
This part is also ideal for use as an antenna diversity switch,
switching different antenna to the tuner.
FILTER SELECTION
The ADG919 can be used as a 2:1 demultiplex to switch high
frequency signals between different filters and also to multiplex
the signal to the output.
RF
RFC
ANTENNA
IN
CABLE
ANTENNA
VGA
ADG919
Figure 26. Wireless Metering
Figure 27. Tuner Modules
Figure 28. Filter Selection
RF1
RF2
TX/RX SWITCH
ADG918
ADG918/
ADG919
RF1
RF2
ADG919
TUNER
LNA
RFC
PA
RF
OUT