+2.8V
+0.2V
HP8644A
Frequency
Synthesizer
Convert
Command
Locked
Analog
Input
Fluke HP6080A
or
HP8644A
Frequency
Synthesizer
ADC614
Under
Test
TTL
Latches
74F574
High-Speed
SRAM
64KB x 16
DSP
Processor
Low-Pass
Filter
3dB
50Ω
– or –
Data Valid
Crystal
Filter
FIGURE 2. Block Diagram of FFT Test for SNR, SFDR and Swept-Power Test.
+2.8V
+0.2V
HP8644A
Frequency
Synthesizer
Convert
Command
Locked
Analog
Input
Fluke HP6080A
or
HP8644A
Frequency
Synthesizer
Band
Pass
Filter
ADC614
Under
Test
TTL
Latches
74F574
High-Speed
SRAM
64KB x 16
DSP
Processor
3dB
Signal
Combiner
50Ω
50Ω
Data Valid
Σ
Fluke HP6080A
or
HP8644A
Frequency
Synthesizer
FIGURE 3. Block Diagram of FFT Test for Two-Tone IMD.
Bandwidth: ≈1MHz to ≈30MHz
In-to-In Isolation: 45dB at 5MHz
In-to-Out Loss: 6dB
50Ω
In
50Ω
Out
L2
L4
L6
L8
50Ω
Out
49.9Ω
50Ω
C1
C3
C5
C7
C9
In
49.9Ω
10 turns #24 AWG
bifilar wound on
Amidon FT 50-43
toroid core.
49.9Ω
9th-Order 0.5dB Ripple
Tchebychev Low-Pass Filter
Attenuation at 2X cutoff frequency = 90dB.
Cutoff frequency = –3dB frequency; to convert cutoff frequency to
–0.5dB frequency, multiply all LC values by 0.98997.
50Ω
In
Cutoff
Freq.
FIGURE 5. Passive Signal Combiner.
C
C
C
C
C
L
L
L
L
8
1
3
5
7
9
2
4
6
(MHz)
(pF)
(pF)
(pF)
(pF)
(pF) (µH)
(µH) (µH)
(µH)
2.5
1.25
2269 3458 3531 3458 2269 4.11
4538 6917 7062 6917 4538 8.23
4.43 4.43
8.86 8.86
4.11
8.23
0.625 9077 13,833 14,125 13,833 9077 16.45 17.73 17.73 16.45
FIGURE 4. Ninth-Order Harmonic Filter.
®
9
ADC614
BB [ BURR-BROWN CORPORATION ]
