LTC559X View Datasheet(PDF) - Linear Technology
Part Name
Description
MFG CO.
LTC559X Datasheet PDF : 20 Pages
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LTC5567
Applications Information
The IF matching shown in Figure 10 uses 249Ω resistors
and 390nH supply chokes to produce a wideband 200Ω
differential output. This differential output is suitable for
driving a wideband differential amplifier, filter, or a wide-
band 4:1 transformer. The evaluation board layout allows
the removal of the IF transformer to evaluate the mixer
performance with a differential output.
The complete test circuit, shown in Figure 11, uses re-
sistive impedance matching attenuators (L-pads) on the
evaluation board to transform each 100Ω IF output to
50Ω. An external 0°/180° power combiner is then used to
convert the 100Ω differential output to 50Ω single-ended,
to facilitate measurement.
Table 5 compares the IF bandwidth and 1dB compression
for the standard 400Ω and wideband 200Ω IF output re-
sistances. As shown, the 200Ω matching doubles the IF
bandwidth, and increases the RF input P1dB to +13dBm.
330pF
200Ω
LOAD
LTC5567 IF+
IF–
249Ω
249Ω
390nH
VCC
390nH
100Ω
100Ω
330pF
5567 F10
Figure 10. Wideband 200Ω Differential Output
Table 5. IF Bandwidth and 1dB Compression for 400Ω and
200Ω Differential IF Output Resistance (RF = 1.69 to 2.24GHz,
LO = 1.65GHz, VCC = 3.3V, TC = 25°C, L1, L2 = 390nH)
ROUT R1, R2
(Ω)
(Ω)
P1dB
(dBm)
1dB (CONVERSION GAIN)
IF FREQUENCY RANGE
400 3.01k
10.1
65MHz to 327MHz
200
249
13.0
45MHz to 580MHz
Measured voltage conversion gain, IIP3 and SSB noise
figure, at the 200Ω differential output are plotted in Fig-
ure 12. Voltage gain, rather than power gain, is plotted
to emphasize the voltage gain due to the 200Ω output.
As shown, the conversion gain is flat within 1dB over the
45MHz to 590MHz IF output frequency range.
28
26
IIP3
24
22 RF = 1.69GHz TO 2.24GHz
20 LO = 1.65GHz
18
ZRF = 50Ω
ZIF = 200Ω DIFFERENTIAL
16 TC = 25°C
14
NF
12
10
8
6
GV
4
40 90 140 190 240 290 340 390 440 490 540 590
IF FREQUENCY (MHz)
5567 F12
Figure 12. Voltage Conversion Gain, IIP3 and NF vs IF
Output Frequency for Wideband 200Ω Differential IF
LO
1.65GHz
0dBm
3.9pF
LTC5567 LO
RF
1.69GHz
TO
2.24GHz
2.7pF
RF
EN
EN
LO
RF
BIAS
VCC
10nF
IF+
IF–
IADJ
249Ω
249Ω
L-PADS AND 180° COMBINER
FOR 50Ω SINGLE-ENDED MEASUREMENT
330pF
69.8Ω
IF+
50Ω
1MHz TO 500MHz
COMBINER
390nH
71.5Ω
IFOUT
200Ω
390nH
IF–
69.8Ω
50Ω
0°
OUT
180°
330pF
71.5Ω
10nF
3.3V
89mA
5567 F11
Figure 11. Test Circuit for Wideband 200Ω Differential Output
IFOUT
50Ω
5567f
15
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