ADL5380-29A-EVALZ AD [Analog Devices], ADL5380-29A-EVALZ Datasheet - Page 24

• Manufacturer Part Number: ADL5380-29A-EVALZ
• Description: 400 MHz to 6 GHz Quadrature Demodulator
• Manufacturer: AD [Analog Devices]

ADL5380
RF INPUT
The RF inputs have a differential input impedance of approximately
50 Ω. For optimum performance, drive the RF port differentially
through a balun. The recommended balun for each performance
level includes the following:
•
•
•
AC couple the RF inputs to the device with 100 pF capacitors.
Figure 79 shows the RF input configuration.
The differential RF port return loss is characterized, as shown
in Figure 80.
BASEBAND OUTPUTS
The baseband outputs QHI, QLO, IHI, and ILO are fixed
impedance ports. Each baseband pair has a 50 Ω differential
output impedance. The outputs can be presented with differential
loads as low as 200 Ω (with some degradation in gain) or high
impedance differential loads (500 Ω or greater impedance yields
the same excellent linearity) that is typical of an ADC. The TCM9-1
9:1 balun converts the differential IF output to a single-ended
output. When loaded with 50 Ω, this balun presents a 450 Ω
load to the device. The typical maximum linear voltage swing for
these outputs is 2 V p-p differential. The output 3 dB bandwidth
is 390 MHz. Figure 81 shows the baseband output configuration.
Up to 3 GHz is the Mini-Circuits TC1-1-13.
From 3 GHz to 4 GHz is the Johanson Technology
3600BL14M050.
From 4.9 GHz to 6 GHz is the Johanson Technology
5400BL15B050.
–10
–12
–14
–16
–18
–20
–22
–24
–26
–28
–30
–8
0
0.5
Figure 80. Differential RF Port Return Loss
1.0
RF INPUT
BALUN
1.5
Figure 79. RF Input
2.0
RF FREQUENCY (GHz)
2.5
3.0
100pF
100pF
3.5
21
22
4.0
RFIN
RFIP
4.5
5.0
5.5
6.0
Rev. 0 | Page 24 of 36
ERROR VECTOR MAGNITUDE (EVM) PERFORMANCE
EVM is a measure used to quantify the performance of a digital
radio transmitter or receiver. A signal received by a receiver has all
constellation points at their ideal locations; however, various
imperfections in the implementation (such as magnitude
imbalance, noise floor, and phase imbalance) cause the actual
constellation points to deviate from their ideal locations.
In general, a demodulator exhibits three distinct EVM
limitations vs. received input signal power. At strong signal
levels, the distortion components falling in-band due to non-
linearities in the device cause strong degradation to EVM
as signal levels increase. At medium signal levels, where the
demodulator behaves in a linear manner and the signal is well
above any notable noise contributions, the EVM has a tendency to
reach an optimum level determined dominantly by the quadrature
accuracy of the demodulator and the precision of the test equipment.
As signal levels decrease, such that noise is a major contribution,
the EVM performance vs. the signal level exhibits a decibel-for-
decibel degradation with decreasing signal level. At lower signal
levels, where noise proves to be the dominant limitation, the
decibel EVM proves to be directly proportional to the SNR.
The ADL5380 shows excellent EVM performance for various
modulation schemes. Figure 82 shows the EVM performance of
the ADL5380 with a 16 QAM, 200 kHz low IF.
ILO
IHI
–10
–15
–20
–25
–30
–35
–40
–45
–50
–5
0
–90
RF Input Power for a 16 QAM 160ksym/s Signal
Figure 82. EVM, RF = 900 MHz, IF = 200 kHz vs.
Figure 81. Baseband Output Configuration
–70
3
4
RF INPUT POWER (dBm)
ADL5380
–50
–30
16
15
–10
QHI
QLO
10