Data Sheet ADG904
Rev. D | Page 11 of 16
APPLICATIONS
The ADG904 and ADG904-R 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. They may be used
in applications such as switchable filters, transmitters and
receivers for radar systems, and communications systems from
base stations to cell phones.
The ADG9xx wideband switches are designed to meet the
demands of devices that transmit at ISM band frequencies of
1 GHz and higher. The low insertion loss, high isolation
between ports, single pin control interface, no requirement for
dc blocking capacitors, and TTL interface compatibility of these
parts make them cost-effective and an easy-to-integrate
switching solution for many high frequency switching
applications and low power applications where the parts can
handle up to 16 dBm of power.
ABSORPTIVE VS. REFLECTIVE
The ADG904 is an absorptive (matched) switch with 50 Ω
terminated shunt legs; the ADG904-R is a reflective switch with
0 Ω terminated shunts to ground. The ADG904 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 ADG904 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 ADG904-R reflective switch is suitable for applications
where high off port VSWR does not matter, and the switch has
other performance features. It may be used in many applica-
tions, including high speed filter selection. In most cases, an
absorptive switch may be used instead of a reflective switch, but
not vice versa.
ANTENNA DIVERSITY SWITCH
The ADG904 is ideal for use as an antenna diversity switch,
switching different antennas into the tuner. The low insertion
loss ensures minimum signal loss and high isolation between
channels, making these SP4T switches suitable for switching
applications in tuner modules and set-top boxes.
TUNER
ADG904
CABLE
RF1
RF2
RF3
RF4
VGA
ANTENNA
04504-0-021
Figure 27. Tuner Modules
FILTER SELECTION
The ADG904 can be used to switch high frequency signals
between different filters and to multiplex the signal to the
output. These SP4T switches are also ideal for high speed
signal routing.
RF
OUT
RFC
ADG904ADG904
RF1
RF2
RF3
RF4
RF1
RF2
RF3
RF4
RF
IN
RFC
04504-0-022
Figure 28. Filter Selection
Tx/Rx SWITCHING
The low insertion loss and high isolation between ports ensure
that the ADG904 and ADG904-R are suitable transmit/receive
switches for all ISM band and wireless LAN, providing the
required isolation between the transmit signal and the
receive signal.
ADG904
Tx
Rx
Rx
Rx
Rx
ANTENNA
04504-0-023
Figure 29. Tx/Rx Switching
