TQ5635 Ver la hoja de datos (PDF) - TriQuint Semiconductor
Número de pieza
componentes Descripción
Fabricante
TQ5635 Datasheet PDF : 25 Pages
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Use multiple ground vias for
maximum LNA gain
GND
RF In TQ5635
GND
LNA
Bias
MXR
In
GND
VDD
LO
In
Vdd
IFout
Vdd
Minimize These
Lengths
Figure 2. Critical signal Paths
Mixer – Filter Interaction:
Before attempting a new TQ5635 application, it is important to
understand the nonlinear interaction between the image filter
and the mixer subcircuit. The device IP3 is a strong function
of this interaction. For this reason it is helpful to consider the
filter and mixer as one nonlinear block.
LNA Portion
of TQ5635
25-100 ohms at RF-
short circuit at LO
TQ5635
Data Sheet
Figure 3 shows a much simplified block diagram of the LNA,
image filter, and mixer. The RF signal is amplified by the
LNA, passes through the image filter, and is converted down
to the IF where it is amplified by the IF output FET. The
quiescent current in the IF amplifier is set by the GIC network.
Both the filter and the mixer terminate the RF signal with
50ohms.
However, the situation is much different with the LO signal. At
the LO frequency the image filter looks like a short circuit.
Some LO energy leaks out of the mixer input, bounces back
off of the image filter and returns back into the mixer with
some phase or delay. The delayed LO signal mixes with the
normal LO to create a DC offset in the passive FET. A DC
blocking capacitor prevents the offset voltage from affecting IF
stage current.
It has been found empirically that varying the delay between
the filter and mixer can have positive or negative
consequences on IP3, CG, and NF. It is for this reason that
an LC network is useful between the SAW and mixer input,
even though the mixer input can have an adequate match at
the RF frequency without any external components.
Mixer Portion
of TQ5635
RF in
2
LNA Out
14
band pass
LO Leakage
12
Mixer
IF Output
FET
Blocking Cap
IF Output
7
Mixer in
Idd
LO Leakage ??????
IF + DC
IF
Offset
LO
9
to GIC
8
(LO Leakage?????+ LO) = DC Offset
at Mixer IF Output
Figure 3. Non-linear filter-Mixer Interaction
For additional information and latest specifications, see our website: www.triquint.com
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