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QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1233A-X
-A
WiMAX
456MHz
Low-side 3.6GHz
-B WiMAX
456MHz
High-side 2.6GHz
-C
UMTS
240MHz
High-side 2.14GHz
-D
PCS 240MHz
Low-side 1.95GHz
Supply Voltage
3.3V
Supply Current
226mA
LO Input Frequency Range
1.1GHz to 4GHz
LO Input Power
-
5 to +2dBm
1233A
-A
1233A
-B
1233A
-C
1233A
-D
WiMAX 3.6GHz
WiMAX 2.6GHz
UMTS
PCS
IF Input Frequency Range
12dB Return Loss, LO applied
330 to 505MHz
330 to 505MHz
174 to 263MHz
174 to 263MHz
RF Output Frequency Range
10dB Return Loss,
LO applied
3170 to 4100MHz
2260 to 2780MHz
2035 to 2285MHz
1840 to 2020MHz
Conversion Gain
-
0.5dB
1.3dB 2.6dB 1.9dB
Conversion Gain vs. Temperature
T = -40°C to 85°C
-0.027dB/°C
-0.027dB/°C
-0.020dB/°C
-0.020dB/°C
Output 3rd Order Intercept
23.2dBm
26.2dBm
27.3dBm
28dBm
Output 2nd Order Intercept
54dBm
45dBm
42dBm
40dBm
Single Sideband Noise Figure
12dB 12dB 9.9dB 9.9dB
Output Noise Floor
P = -5dBm
-155.5dBm/Hz
-157.5dBm/Hz
-158.1dBm/Hz
-158.1dBm/Hz
Output 1dB Compression
10.7dBm
13.7dBm
13.9dBm
13.6dBm
IF to LO Isolation
73dB 74dB 81dB 80dB
LO to IF Leakage
-
22dBm
-26dBm
-28dBm
-25dBm
LO to RF Leakage
-
35dBm
-36dBm
-35dBm
-34dBm
DESCRIPTION
1.5GHZ TO 3.8GHZ HIGH LINEARITY UPCONVERTING MIXER
LT5579
Demonstration circuit 1233A-x is a high linearity upconverting mixer featuring the LT5579.
The LT®5579 is a high performance upconverting mixer
IC optimized for output frequencies in the 1.5GHz to
The DC1233A-x series of demonstration circuits are
designed for evaluating the LT5579 IC at several common frequency ranges:
VERSION APPLICATION IF INPUT LO INPUT RF OUTPUT
3.8GHz range. It features single-ended LO input and RF
output ports to simplify board layout and to reduce system cost.
The LT5579 offers a superior alternative to passive mixers. Unlike passive mixers which have conversion loss
and require high LO drive levels, the LT5579 delivers
conversion gain at significantly lower LO input levels
and is less sensitive to LO power level variations. Only
-1dBm of LO power is needed, and the balanced design
Demonstration circuit 1233A-x can be easily optimized
for operations at other frequencies. Refer to the “Application Note” section and the LT5579 data sheet for details.
results in low LO signal leakage to the RF output. The
lower LO drive level requirements, combined with the
excellent LO leakage performance, translate into lower
LO signal contamination of the output signal.
Table 1. Typical Demo Circuit Performance Summary (TA = 25°C, VCC = 3.3V, P
PLO = -1dBm, unless otherwise noted. Low side LO for 1950MHz and 3600MHz. High side LO for 2140MHz and 2600MHz.)
PARAMETER CONDITIONS TYPICAL PERFORMANCE
Design files for this circuit board are available. Call
the LTC factory.
, LT, LTC, and LTM are registered trademarks of Linear Technology Corp.
All other trademarks are the property of their respective owners.
= -5dBm (-5dBm/tone for 2-tone tests,
IF
∆∆∆∆
f = 1MHz),
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QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1233A-X
1.5GHZ TO 3.8GHZ HIGH LINEARITY UPCONVERTING MIXER
APPLICATION NOTE
ABSOLUTE MAXIMUM RATINGS
Supply Voltage......................................................3.6V
LO Input Power.............................................. +10dBm
LO Input DC Voltage .................... -0.3V to VCC + 0.3V
RF Output DC Current........................................ 60mA
IF Input Power (Differential).......................... +13dBm
IF+, IF- DC Currents ........................................... 60mA
T
.................................................................150°C
JMAX
Operating Temperature Range.............. -40°C to 85°C
Storage Temperature Range............... -65°C to 150°C
IF INPUT INTERFACE
The standard demonstration circuit 1233A-x can be reconfigured for other IF input frequencies. The details of
the matching circuit are omitted in this guide, since the
LT5579 datasheet presents in depth explanations and
the IC’s IF input differential impedance. Matching component values for several common IF input frequencies
are listed in Table 2. Refer to the demonstration circuit
schematic in Figure 3.
Table 2. IF Input Component Values
IF Freq.
(MHz)
140
240
450
NOTE:
C1,C2
(pF)
70 1000 120 (2) 4.7nH 100 9.1
1000 120 (2)
C9 (1)
(pF)
82 33 (2)
33 33 (2)
C3
(pF)
TL1,TL2
(3)
Z0=70
Ω
Z0=70Ω
Z0=70Ω
L1,L2
R1,R2
(nH)
100 9.1
(
40 11
40 11
ΩΩΩΩ
)
3.
The 70Ω microstrip transmission line TL1 and TL2
provide inductances required for matching. At lower
frequencies, external inductors are necessary.
4.
R1 and R2 set the DC current in the mixer core to the
optimum level of 50mA per side. Their values should
be well matched for best LO leakage performance.
0.1% tolerance is recommended.
5.
L1 and L2 reduce the loading effect of R1 and R2.
Their self-resonant frequency should be at least several times the IF frequency. High quality wire-wound
type inductors are recommended. The DC resistances of L1 and L2 need to be accounted for in the
selection of R1 and R2.
LO INPUT INTERFACE
The LT5579’s LO input port is internally matched from
1.1GHz to 4GHz, with a minimum return loss across
this range of about 9dB at 2.3GHz. External matching
should be used for lower LO frequencies for best performance. Refer to the LT5579 datasheet for more information and impedance data.
RF OUTPUT INTERFACE
The LT5579 utilizes an internal RF transformer to step
down the mixer core output impedance to simply RF
output matching. Matching component values for several common RF output frequencies are listed in Table
3. High quality precision microwave capacitors, such
as the AVX Accu-p series, should be used for C8 to
minimize parasitics.
1.
Center of C9 is 3mm from the edge of the IC package
for all cases.
2.
C3 is a small-valued capacitor used to improve the
LO-RF leakage in some applications, and it has little
effect on impedance matching. C3’s value and location depend on LO and RF frequencies and are determined experimentally. In certain instances, two
common-mode capacitors to ground instead of one
single differential capacitor may provide better leakage suppression.
Table 3. RF Output Component Values
RF Frequency (MHz) C8 (pF) L3 (nH)
1650 1.5 6.8
1750
1950
2140
2600
3600
1.2 6.8
1 4.7
0.45 3.9
- 1.0
0.7
0Ω
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QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1233A-X
1.5GHZ TO 3.8GHZ HIGH LINEARITY UPCONVERTING MIXER
TEST EQUIPMENT AND SETUP
The LT5579 is a high linearity upconverting mixer IC.
Accuracy of its performance measurement is highly
dependent on equipment setup and measurement technique. The following precautions are recommended:
1.
Use high performance signal generators with low
harmonic output. Otherwise, utilize low-pass filters at the signal generator outputs to suppress
higher-order harmonics.
2.
Turn off the signal generators’ output automaticlevel-control (ALC). This prevents conflict in
power-level control between the two sources,
which can introduce intermodulation products.
3.
High quality combiners that provide broadband
50ΩΩΩΩ termination on all ports and have good port-
to-port isolation should be used. Attenuators on
the outputs of the signal generators are recommended to further improve source isolation to
prevent the sources from modulating each other
and generating intermodulation products.
4.
Beware of the signal generators’, and if used, source
amplifiers’ 1dB compression point. When driven
close to their 1dB compression point, the sources
and amplifiers may introduce additional distortions.
5.
The level of intermodulation products from the input
sources needs to be much lower than the products
expected to be generated by the DUT. In general, IM
products measured at the input connector to the DUT
should be 25dB or more below the expected level at
the DUT output.
6.
If possible, use small attenuator pads with good
VSWR on the demonstration circuit’s input and
output ports to improve source and load match to
reduce reflections, which may degrade measurement accuracy.
7.
Use narrow resolution bandwidth (RBW) and engage video averaging on the spectrum analyzer to
lower the displayed average noise level (DANL) in
order to improve sensitivity and to increase dynamic range. The trade off is increased sweep
time.
8.
Spectrum analyzers can produce significant internal
distortion products if they are overdriven. Generally,
spectrum analyzers are designed to operate at their
best with about –30dBm to -40dBm at their input filter or preselector.
put attenuation should be used to avoid saturating
the instrument, but too much attenuation reduces
sensitivity and dynamic range.
9.
Before performing measurements on the demo
circuit, the system performance should be evaluated to ensure that: 1) clean input signal can be
produced, 2) the spectrum analyzer’s internal distortion is minimized, 3) the spectrum analyzer has
enough dynamic range and sensitivity, and 4) the
system is accurately calibrated for power and frequency.
Sufficient spectrum analyzer in-
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QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1233A-X
1.5GHZ TO 3.8GHZ HIGH LINEARITY UPCONVERTING MIXER
QUICK START PROCEDURE
Demonstration circuit 1233A-x is easy to set up to
evaluate the performance of the LT5579. Refer to
Figure 1 and Figure 2 for proper measurement equipment connections and follow the procedure below:
NOTE:
Care should be taken to never exceed absolute
maximum input ratings.
RETURN LOSS MEASUREMENTS
1.
Configure the Network Analyzer for return loss
measurement, set appropriate frequency range,
and set the test signal to –5dBm.
2.
Calibrate the Network Analyzer.
3.
Connect all test equipment as shown in
4.
Apply 3.3V DC supply power, and verify that the
Figure 1
.
current consumption is approximately 226mA in
the presence of LO signal. The supply voltage
should be confirmed at the demo board VCC and
GND terminals to account for ohmic losses due to
the high current.
5.
With the LO signal applied, and the unused demo
board port terminated in 50Ω, measure return
loss of the IF input and RF output ports.
6.
Set the test signal to –1dBm, and re-calibrate the
Network Analyzer.
7.
Terminate the IF input and RF output ports in 50Ω.
Measure return loss of the LO input port.
RF PERFORMANCE MEASUREMENTS
1.
Connect all test equipment as shown in Figure 2.
2.
Set the LO source (Signal Generator 1) to provide
a -1dBm, CW signal to the demo board LO input
port at appropriate LO frequency.
3.
Set the IF sources (Signal Generators 2 and 3) to
provide two -5dBm CW signals, 1MHz apart, to
the demo board IF input port at the appropriate IF
frequency.
4.
Measure the resulting RF output on the Spectrum
Analyzer:
a.
The wanted two-tone RF output signals are at:
f
OUT(1,2)
f
OUT(1,2)
b.
The 2nd order intermodulation product which is
= fLO + f
= fLO – f
for low-side LO, and
IF(1,2)
for high-side LO
IF(1,2)
closest to the wanted RF signals is used to calculate the Output 2nd Order Intercept:
f
= fLO + (f
IM2
f
= fLO - (f
IM2
c.
Similarly, use the 3rd order intermodulation
IF1
IF1
+ f
) for low-side LO, and
IF2
+ f
) for high-side LO
IF2
products which are closest to the wanted RF
signals to calculate the Output 3rd Order Intercept:
f
= fLO + f
IM3,1
f
= fLO + f
IM3,2
f
= fLO - f
IM3,1
f
= fLO - f
IM3,2
Where
5.
Calculate Output 2nd and 3rd Order Intercepts:
∆
= f
IF
OIP2 = 2•P
OIP3 = (3•P
Where P
is the lowest power level of the two
OUT
wanted output signals at either f
the 2nd order intermodulation product at f
P
is the largest 3rd order intermodulation product
IM3
at either f
IM3,1
or f
IF2
OUT
- ∆
IF1
IF2
IF1
IF2
– f
– P
OUT
IM3,2
, and
IF
+ ∆
for low-side LO, and
IF
+ ∆
, and
IF
- ∆
for high-side LO
IF
.
IF1
IM2
– P
IM3
) / 2
OUT1
. All units are in dBm.
or f
OUT2
, P
IM2
Alternatively, the output intercept can be calculated
using the power difference between the desired output signal and the intermodulation products:
OIP2 =
OIP3 = (∆
Where
6.
Turn off one of the IF signal generators, and measure
∆
IM(2,3)
∆
IM2
IM3
= P
+ P
OUT
)/2 + P
OUT
– P
OUT
IM(2,3)
.
Conversion Gain, IF to LO isolation, LO to IF and LO
to RF leakages, and Input 1dB compression point.
is
IM2
, and
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QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1233A-X
1.5GHZ TO 3.8GHZ HIGH LINEARITY UPCONVERTING MIXER
Figure 1. Proper Equipment Setup for Return Loss Measurements
Figure 2. Proper Equipment Setup for RF Performance Measurements
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QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1233A-X
1.5GHZ TO 3.8GHZ HIGH LINEARITY UPCONVERTING MIXER
Figure 3. Demonstration Circuit Schematic
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