TQ5131 Ver la hoja de datos (PDF) - TriQuint Semiconductor
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TQ5131 Datasheet PDF : 14 Pages
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TQ5131 Product Description
The TQ5131 is a miniature low noise mixer (downconverter) in a
small SOT-23-8 package (2.9X2.8X1.14 mm) with operation at
2.8v. It is designed for cellular CDMA applications and dual-
mode CDMA/AMPS mobile phones. The IC features excellent
linearity with an input intercept point of +2.5dBm in its high gain
mode and +10.0dBm in its low gain mode. It has a typical noise
figure of 4.5 dB for CDMA and 5.0 for AMPS mode. For
optimum performance the TQ5131 RF frequency of operation
should be from 869 to 894 MHz. The IF range is from 85 to 130
MHz and its injection mode for the local oscillator is high side.
Operation
The TQ5131 is a single-ended mixer with switching capabilities
for the various signal levels found in CDMA applications. It
consists of a RF amplifier, followed by a single-ended mixer
driven by a grounded gate LO buffer amplifier. The mixer output
can be directed either to the CDMA IF amplifier or the AMPS IF
amplifier via a switch. Pin 1 and 7 are used to control the RF
amplifier gain select and the mixer mode select respectively.
RF / C2 1
GND 2
TQ5131
8 Mx Vdd
7 LO / C1
GIC 3
CDMA 4
IF
Figure 1. TQ5131 Block Diagram
6 IFA GS/C3
AMPS
5 IF
Detailed Circuit Description: RF Amplifier
The TQ5131 has an integrated pre-amplifier stage in a cascode
configuration. The output is internally matched to 50 ohms at
881MHz. Pin 1 requires an external match that is set to deliver a
2:1 VSWR in both the low and high gain modes (i.e. RFA is on
or off). Figure 2 shows an approximated impedance at pin 1
(RFA input) to implement any desired match. The TQ5131
performance in TriQuint’s demo board was achieved using the
TQ5131
Data Sheet
following source impedance z = 1.86 + j2.41 Ω(normalized to 50
Ω).
0.5
0.5
-0.5
1.0
Source
2.0
A Impedance
0.68 @ 30.2
z = 1.86 + j 2.41
y = 0.20 - j 0.26
A
1.0
2.0
B
-2.0
-1.0
Input
Impedance
B (High Gain)
0.75 @ -63.1
z = 0.5 - j 1.51
y = 0.20 + j 0.60
Figure 2. RFA Input and Source Impedance
LO Buffer Amplifier
The on-chip LO buffer amplifier is a grounded gate FET. The
capacitor also serves as a DC block to the control voltage. The
TQ5131 has internal LO tuning. This eases the work of the RF
system designer and eliminates the need for the external tank
circuit (inductor and capacitor) that would otherwise be needed
to tune the frequency response of the LO buffer. The LO is
limited to high-side injection mode and it operates from 950MHz
to 1030MHz. The input to the LO buffer is through pin 7 which
also feeds the control line (C1) that selects the mixer mode of
operation, either CDMA or AMPS. Due to this logic control, the
only external component required at the LO port is a series
capacitor to prevent DC from traveling to other parts of the
system. The LO drive level of operation should be between -7
and 0 dBm. Best performance is obtained between –6 and –2
dbm.
LO/filter/Mixer interaction
The physical position of the image reject filter is likely to have an
effect on the performance of the mixer especially in the Low
Gain mode where the RF amplifier is switched out. This is
primarily due to self-mixing of the LO energy bouncing from the
filter back into the mixer either out-of-phase or in-phase creating
an offset in magnitude. To minimize this effect, TriQuint
For additional information and latest specifications, see our website: www.triquint.com
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