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LTC5592IUH#PBF

P1-P3P4-P6P7-P9P10-P12P13-P15P16-P18P19-P20
LTC5592
13
5592fa
For more information www.linear.com/LTC5592
The RF input impedance and input reflection coefficient,
versus RF frequency, are listed in Table 1. The reference
plane for this data is Pin 1 of the IC, with no external
matching, and the LO is driven at 2.16GHz.
Table 1. RF Input Impedance and S11
(at Pin 1, No External Matching, f
LO
= 2.16GHz)
FREQUENCY
(GHz)
RF INPUT
IMPEDANCE
S11
MAG ANGLE
1.6 66.0 + j6.8 0.15 20
1.7 62.4 + j0.5 0.11 2
1.8 57.9 – j3.8 0.08 –24
1.9 53.2 – j6.1 0.07 –59
2.0 48.5 – j8.8 0.09 –95
2.1 40.6 – j9.3 0.14 –130
2.2 35.0 – j0.1 0.18 –180
2.3 39.3 + j3.7 0.13 –201
2.4 41.2 + j3.9 0.11 –207
2.5 41.7 + j4.3 0.10 –211
2.6 42.8 + j4.1 0.09 –212
2.7 44.1 + j3.6 0.07 –213
applicaTions inForMaTion
Figure 5. LO Input Schematic
LO Input
The LO input, shown in Figure 5, is connected to the
primary winding of an integrated transformer. A 50Ω
impedance match is realized at the LO port by adding
an external series capacitor, C2. This capacitor is also
needed for DC blocking if the LO source has DC voltage
present, since the primary side of the LO transformer is
DC-grounded internally. The DC resistance of the primary
is approximately 1.8Ω.
The secondary of the transformer drives a pair of high
speed limiting differential amplifiers for channels A and B.
The LTC5592’s LO amplifiers are optimized for the 1.7GHz
to 2.5GHz LO frequency range; however, LO frequencies
outside this frequency range may be used with degraded
performance.
The LO port is always 50Ω matched when V
CC
is applied,
even when one or both of the channels is disabled. This
helps to reduce frequency pulling of the LO source when
the mixer is switched between different operating states.
Figure 6 illustrates the LO port return loss for the different
operating modes.
Figure 6. LO Input Return Loss
The nominal LO input level is 0dBm, though the limiting
amplifiers will deliver excellent performance over a ±6dBm
input power range. Table 2 lists the LO input impedance
and input reflection coefficient versus frequency.
Table 2. LO Input Impedance vs Frequency
(at Pin 16, No External Matching, ENA = ENB = High)
FREQUENCY
(GHz)
INPUT
IMPEDANCE
S11
MAG ANGLE
1.7 46.4 + j34.4 0.34 76
1.8 47.0 + j31.0 0.31 78
1.9 46.5 + J28.2 0.28 81
2.0 44.4 + J26.8 0.28 86
2.1 43.1 + j26.0 0.28 89
2.2 41.8 + j26.2 0.29 91
2.3 40.4 + j27.4 0.31 92
2.4 38.8 + j28.5 0.33 94
2.5 38.0 + j30.4 0.35 93
FREQUENCY (MHz)
1300 17001500
–30
–20
–25
RETURN LOSS (dB)
–15
–10
0
–5
5592 F06
1900 2100 2300 2500
BOTH CHANNELS ON
ONE CHANNEL ON
BOTH CHANNELS OFF
LO
TO
MIXER B
LTC5592
I
SEL
5592 F05
18
LO
16
17
ENA
ENB
C2
14
BIAS
BIAS
TO
MIXER A
LTC5592
14
5592fa
For more information www.linear.com/LTC5592
IF Outputs
The IF amplifiers in channels A and B are identical. The IF
amplifier for channel A, shown in Figure 7, has differen
-
tial open collector outputs (IFA
+
and IFA
–
), a DC ground
return pin (IFGNDA), and a pin for adjusting the internal
bias (IFBA). The IF outputs must be biased at the sup
-
ply voltage (V
CCIFA
), which is applied through matching
inductors L1A and L2A. Alternatively, the IF outputs can
be biased through the center tap of a transformer (T1A).
The common node of L1A and L2A can be connected to
the center tap of the transformer. Each IF output pin draws
approximately 50.5mA of DC supply current (101mA total).
An external load resistor, R2A, can be used to improve
impedance matching if desired.
IFGNDA (Pin 23) must be grounded or the amplifier will
not draw DC current. Inductor L3A may improve LO-IF
and RF-IF leakage performance in some applications, but
is otherwise not necessary. Inductors should have small
resistance for DC. High DC resistance in L3A will reduce
the IF amplifier supply current, which will degrade RF
performance.
applicaTions inForMaTion
For optimum single-ended performance, the differential
IF output must be combined through an external IF
transformer or a discrete IF balun circuit. The evaluation
board (see Figures 1 and 2) uses a 4:1 IF transformer for
impedance transformation and differential to single-ended
conversion. It is also possible to eliminate the IF transformer
and drive differential filters or amplifiers directly.
The IF output impedance can be modeled as 379Ω in
parallel with 2.2pF. The equivalent small-signal model,
including bondwire inductance, is shown in Figure 8.
Frequency-dependent differential IF output impedance is
listed in T
able 3. This data is referenced to the package
pins (with no external components) and includes the ef
-
fects of IC and package parasitics.
Figure 7. IF Amplifier Schematic with Bandpass Match
Figure 8. IF Output Small-Signal Model
Bandpass IF Matching
The bandpass IF matching configuration, shown in Figures
1 and 7, is best suited for IF frequencies in the 90MHz to
500MHz range. Resistor R2A may be used to reduce the IF
output resistance for greater bandwidth and inductors L1A
and L2A resonate with the internal IF output capacitance
at the desired IF frequency. The value of L1A, L2A can be
estimated as follows:
L1A = L2A =
1
2πf
IF
( )
2
• 2 • C
IF
where C
IF
is the internal IF capacitance (listed in Table 3).
22
21
IFA
+
IFA
–
0.9nH0.9nH
R
IF
C
IF
LTC5592
5592 F08
4:1
T1A
IFA
C7A
L2AL1A
C5A
R2A
L3A (OR SHORT)
V
CCIFA
20212223
IF
AMP
BIAS
101mA
4mA
IFBA
V
CCA
LTC5592
IGNDA
IFA
–
IFA
+
R1A
(OPTION TO
REDUCE
DC POWER)
5592 F07
LTC5592
15
5592fa
For more information www.linear.com/LTC5592
Values of L1A and L2A are tabulated in Figure 1 for vari-
ous IF frequencies. The measured IF output return loss
for bandpass IF matching is plotted in Figure 9.
Table 3. IF Output Impedance vs Frequency
FREQUENCY (MHz)
DIFFERENTIAL OUTPUT
IMPEDANCE (R
IF
||
X
IF
(C
IF
))
90 403 || – j610 (2.9pF)
140 384 || – j474 (2.4pF)
190 379 || – j381 (2.2pF)
240 380 || – j316 (2.1pF)
300 377 || – j253 (2.1pF)
380 376 || – j210 (2.0pF)
450 360 || – j177 (2.0pF)
applicaTions inForMaTion
Figure 9. IF Output Return Loss with Bandpass Matching
board (see Figure 2) has been laid out to accommodate
this matching topology with only minor modifications.
IF Amplifier Bias
The IF amplifier delivers excellent performance with V
CCIF
= 3.3V, which allows a single supply to be used for V
CC
and
V
CCIF
. At V
CCIF
= 3.3V, the RF input P1dB of the mixer is
limited by the output voltage swing. For higher P1dB, in
this case, resistor R2A (Figure 7) can be used to reduce
the output impedance and thus the voltage swing, thus
improving P1dB. The trade-off for improved P1dB will be
lower conversion gain.
With V
CCIF
increased to 5V the P1dB increases by over 3dB,
at the expense of higher power consumption. Mixer P1dB
performance at 1950MHz and 2350MHz is tabulated in Table
4 for V
CCIF
values of 3.3V and 5V. For the highest conversion
gain, high-Q wire-wound chip inductors are recommended
for L1A and L2A. Low cost multilayer chip inductors may
be substituted, with a slight reduction in conversion gain.
Figure 10. IF Output with Lowpass Matching
Figure 11. IF Output Return Loss with Lowpass Matching
Lowpass IF Matching
For IF frequencies below 90MHz, the inductance values
become unreasonably high and the lowpass topology
shown in Figure 10 is preferred. This topology also can
provide improved RF to IF and LO to IF isolation. V
CCIFA
is supplied through the center tap of the 4:1 transformer.
A lowpass impedance transformation is realized by shunt
elements R2A and C9A (in parallel with the internal RIF
and CIF), and series inductors L1A and L2A. Resistor
R2A is used to reduce the IF output resistance for greater
bandwidth, or it can be omitted for the highest conver
-
sion gain. The final impedance transformation to 50Ω is
realized by transformer T1A. The measured return loss
is shown in Figure 11 for different values of inductance
(C9A = open). The case with 82nH inductors and a 1k
load resistor (R2A) is also shown. The LTC5592 demo
4:1
T1A
IFA
50Ω
V
CCIFA
3.1 TO 5.3V
C5A
2122
IFA
–
IFA
+
C6
C9A
R2A
L1A L2A
LTC5592
5592 F10
FREQUENCY (MHz)
50
–25
–20
RETURN LOSS (dB)
–15
–10
0
–5
100
300
5592 F09
150 200 250
350
400 450
500
270nH
150nH
100nH
56nH
33nH
22nH
RETURN LOSS (dB)
–20
–25
–15
–10
0
–5
FREQUENCY (MHz)
500 100
150
5592 F11
200
250
68nH
100nH
180nH
82nH + 1k
P1-P3P4-P6P7-P9P10-P12P13-P15P16-P18P19-P20

LTC5592IUH#PBF

Mfr. #:
Buy LTC5592IUH#PBF
Manufacturer:
Analog Devices Inc.
Description:
RF Mixer Dual 1.6GHz 2.7GHz High Linearity High Gain Passive Mixer
Lifecycle:
New from this manufacturer.
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