Evaluation Board User Guide
UG-016
Rev. 0 | Page 9 of 28
Adjust the Amplitude of the Input Signal
Next, adjust the amplitude of the input signal for each channel
as follows:
1.
Adjust the amplitude of the input signal so that the
fundamental is at the desired level (examine the
Fund
Power
reading in the left panel of the
VisualAnalog FFT
window). If the gain pin voltage is too low, it is not possible
to reach full scale without distortion. Use a higher gain setting
or a lower input level to avoid distortion. This also depends
on the PGA gain setting, which can be 30 dB, 27 dB, 24 dB
(default), or 21 dB. See Figure 14 and Figure 15.
08
28
2-
0
14
Figure 14. VisualAnalog, FFT Graph, Gain = 0 V
0
8
282
-01
5
Figure 15. VisualAnalog, FFT Graph, Gain = 1.6 V
2.
If another channel needs to be evaluated, change the
channel setting within the ADC Data Capture block.
Channels A and B are the default displayed channels
ADC
Data Capture Settings
box under the
General
tab. Clock
Frequency and the number of samples can also be changed.
3. Click the disk icon within the
Graph
box to save the
performance plot. See Figure 16.
0
–20
–40
–60
–80
–100
–120
–140
0
5
10
15
20
FREQUENCY (MHz)
AM
P
L
IT
UDE
(
d
BF
S
)
08
28
2-
0
16
f
IN
= 5MHz @ –1dBFS
LNA = 21.6dB
PGA = 24dB
V
GAIN
= 1.6V
LPF = 1 × 1/3 × F
SAMPLE
HPF = F
LP
÷ 20.7
Figure 16. Typical FFT, AD9276 and AD9277
USING THE INTEGRATED I/Q DEMODULATOR
(CW DOPPLER MODE)
To examine the spectrum of the CW Doppler integrated I/Q
demodulator output, use the following procedure:
1.
Complete the steps in the Configuring the Board and
Using the Software for Testing sections to ensure that the
evaluation board is set up correctly.
2.
Optionally, remove the voltage source from the gain pin,
J401. It does not affect the CW Doppler output.
3.
Use a 1 meter, shielded, RG-58, 50 Ω coaxial cable to
connect the spectrum analyzer to J402 and/or J403.
8.
Connect a 20 MHz signal source to J303, 4LO input. Use a
clean signal generator with low phase noise to provide an
input clock signal. Use a 1 meter, shielded, RG-58, 50 Ω
coaxial cable to connect the signal generator.
9.
Connect an analog input signal, 5.0123 MHz for example,
to ChA, J101. Use a clean signal generator with low phase
noise to provide an input signal to the desired channel. Use
a 1 meter, shielded, RG-58, 50 Ω coaxial cable to connect
the signal generator. For best results, use a narrow-band
band-pass filter with 50 Ω terminations and an appropriate
center frequency (Analog Devices uses TTE, Allen
Avionics, and K&L band-pass filters).
4.
In the
ADCBase 0
tab of the SPI Controller, find the
MODES(8)
box. Select the
CW Mode
option (see Figure 17).
Содержание UG-016
Страница 12: ...UG 016 Evaluation Board User Guide Rev 0 Page 12 of 28 08282 021 Figure 22 DUT Analog Input Circuits Continued...
Страница 13: ...Evaluation Board User Guide UG 016 Rev 0 Page 13 of 28 08282 022 Figure 23 DUT VREF and Decoupling...
Страница 15: ...Evaluation Board User Guide UG 016 Rev 0 Page 15 of 28 08282 024 Figure 25 Clock Circuitry...
Страница 17: ...Evaluation Board User Guide UG 016 Rev 0 Page 17 of 28 08282 026 Figure 27 Top Side...
Страница 18: ...UG 016 Evaluation Board User Guide Rev 0 Page 18 of 28 08282 027 Figure 28 Ground Plane Layer 2...
Страница 19: ...Evaluation Board User Guide UG 016 Rev 0 Page 19 of 28 08282 028 Figure 29 Power Plane Layer 3...
Страница 20: ...UG 016 Evaluation Board User Guide Rev 0 Page 20 of 28 08282 029 Figure 30 Power Plane Layer 4...
Страница 21: ...Evaluation Board User Guide UG 016 Rev 0 Page 21 of 28 08282 030 Figure 31 Ground Plane Layer 5...
Страница 22: ...UG 016 Evaluation Board User Guide Rev 0 Page 22 of 28 08282 031 Figure 32 Bottom Side...
Страница 27: ...Evaluation Board User Guide UG 016 Rev 0 Page 27 of 28 NOTES...
