CASPER Memo 005
ADC frequency response characteristics
Christina de Jesus
May 2006
Introduction
The iADC, which can digitize either two streams of data at 1 Gsps or one stream of data at 2 Gsps,
was designed to be the IBOB's input data source. It has seven SMA input ports: I+, I-, clk_i, sync,
Q+, Q-, and clk_q. Each of these input ports was designed for 50-ohm termination.
I- and Q- traces have been cut in all 0.2.x ADCs, and likely will be in future runs.
Motivation
This characterization was undertaken to quantify the extent of the ADC's power rolloff and to
check for a power dip around 700MHz.
Test equipment
The 1GHz, 6 April 2006 version of the pocket spectrometer and 16 March 2006 version of pocketplot was used for measurement.
Clock: 1024MHz @ 0 dBm, HP 8780A rated to 3 Ghz
Input: 16MHz-1000MHz, 16MHz intervals @ -30dBm, Agilent E4438C rated to 1.0GHz
Results
ADC datasheet characteristics (from page 23 of the ADC datasheet, found at http://www.atmel.com/dyn/resources/prod_documents/doc2153E.pdf)
Measurements show that the ADC levels are consistent with those specified in the datasheet.
No significant dip in power was observed at 700MHz; however, power levels reduce significantly
after 1GHz.
All data taken can be found here.
Further measurements should be taken at input frequencies beyond 1GHz to verify ADC behavior.
It will also be convenient to characterize each ADC board's frequency response for testing purposes.
| ADC serial | Frequency (Mhz) | Power level (?) |
| 0.2.1 | 16 | 2.42E+013 |
| | 32 | 2.28E+013 |
| | 48 | 2.22E+013 |
| | 64 | 2.22E+013 |
| | 80 | 2.20E+013 |
| | 96 | 2.19E+013 |
| | 112 | 2.19E+013 |
| | 128 | 2.11E+013 |
| | 144 | 2.43E+013 |
| | 160 | 2.30E+013 |
| | 176 | 2.07E+013 |
| | 192 | 2.06E+013 |
| | 208 | 2.06E+013 |
| | 224 | 2.00E+013 |
| | 240 | 1.97E+013 |
| | 256 | 1.96E+013 |
| | 272 | 1.95E+013 |
| | 288 | 1.93E+013 |
| | 304 | 1.87E+013 |
| | 320 | 1.88E+013 |
| | 336 | 1.85E+013 |
| | 352 | 1.82E+013 |
| | 368 | 1.79E+013 |
| | 384 | 1.75E+013 |
| | 400 | 1.70E+013 |
| | 416 | 1.68E+013 |
| | 432 | 1.67E+013 |
| | 448 | 1.63E+013 |
| | 464 | 1.57E+013 |
| | 480 | 1.52E+013 |
| | 496 | 1.49E+013 |
| | 512 | 1.61E+013 |
| | 528 | 1.46E+013 |
| | 544 | 1.44E+013 |
| | 560 | 1.39E+013 |
| | 576 | 1.32E+013 |
| | 592 | 1.33E+013 |
| | 608 | 1.34E+013 |
| | 624 | 1.30E+013 |
| | 640 | 1.26E+013 |
| | 656 | 1.24E+013 |
| | 672 | 1.24E+013 |
| | 688 | 1.18E+013 |
| | 704 | 1.11E+013 |
| | 720 | 1.12E+013 |
| | 736 | 1.14E+013 |
| | 752 | 1.14E+013 |
| | 768 | 1.08E+013 |
| | 784 | 1.01E+013 |
| | 800 | 9.89E+012 |
| | 816 | 9.51E+012 |
| | 832 | 8.52E+012 |
| | 848 | 8.19E+012 |
| | 864 | 7.57E+012 |
| | 880 | 7.05E+012 |
| | 896 | 4.68E+012 |
| | 912 | 4.68E+012 |
| | 928 | 3.38E+012 |
| | 944 | 2.94E+012 |
| | 960 | 2.86E+012 |
| | 976 | 3.36E+012 |
| | 992 | 4.15E+012 |
|  |
| ADC serial | Frequency (Mhz) | Power level (?) |
| 0.2.3 | 16 | 2.47E+013 |
| | 32 | 2.32E+013 |
| | 48 | 2.27E+013 |
| | 64 | 2.28E+013 |
| | 80 | 2.26E+013 |
| | 96 | 2.19E+013 |
| | 112 | 2.23E+013 |
| | 128 | 2.20E+013 |
| | 144 | 2.23E+013 |
| | 160 | 2.17E+013 |
| | 176 | 2.07E+013 |
| | 192 | 2.04E+013 |
| | 208 | 2.09E+013 |
| | 224 | 2.06E+013 |
| | 240 | 2.01E+013 |
| | 256 | 1.98E+013 |
| | 272 | 1.98E+013 |
| | 288 | 1.97E+013 |
| | 304 | 1.93E+013 |
| | 320 | 1.92E+013 |
| | 336 | 1.92E+013 |
| | 352 | 1.88E+013 |
| | 368 | 1.82E+013 |
| | 384 | 1.78E+013 |
| | 400 | 1.75E+013 |
| | 416 | 1.72E+013 |
| | 432 | 1.70E+013 |
| | 448 | 1.66E+013 |
| | 464 | 1.61E+013 |
| | 480 | 1.56E+013 |
| | 496 | 1.52E+013 |
| | 512 | 1.44E+013 |
| | 528 | 1.49E+013 |
| | 544 | 1.48E+013 |
| | 560 | 1.43E+013 |
| | 576 | 1.39E+013 |
| | 592 | 1.37E+013 |
| | 608 | 1.38E+013 |
| | 624 | 1.35E+013 |
| | 640 | 1.30E+013 |
| | 656 | 1.29E+013 |
| | 672 | 1.29E+013 |
| | 688 | 1.27E+013 |
| | 704 | 1.23E+013 |
| | 720 | 1.20E+013 |
| | 736 | 1.22E+013 |
| | 752 | 1.21E+013 |
| | 768 | 1.19E+013 |
| | 784 | 1.11E+013 |
| | 800 | 1.07E+013 |
| | 816 | 1.02E+013 |
| | 832 | 9.39E+012 |
| | 848 | 9.00E+012 |
| | 864 | 9.00E+012 |
| | 880 | 7.34E+012 |
| | 896 | 5.10E+012 |
| | 912 | 5.49E+012 |
| | 928 | 4.53E+012 |
| | 944 | 4.79E+012 |
| | 960 | 5.45E+012 |
| | 976 | 6.52E+012 |
| | 992 | 7.51E+012 |
|  |
| ADC serial | Frequency (Mhz) | Power level (?) |
| 0.2.4 | 16 | 2.41E+013 |
| | 32 | 2.25E+013 |
| | 48 | 2.20E+013 |
| | 64 | 2.21E+013 |
| | 80 | 2.18E+013 |
| | 96 | 2.14E+013 |
| | 112 | 2.16E+013 |
| | 128 | 2.31E+013 |
| | 144 | 2.20E+013 |
| | 160 | 2.08E+013 |
| | 176 | 2.02E+013 |
| | 192 | 1.96E+013 |
| | 208 | 2.02E+013 |
| | 224 | 1.97E+013 |
| | 240 | 1.90E+013 |
| | 256 | 1.89E+013 |
| | 272 | 1.88E+013 |
| | 288 | 1.89E+013 |
| | 304 | 1.86E+013 |
| | 320 | 1.82E+013 |
| | 336 | 1.77E+013 |
| | 352 | 1.72E+013 |
| | 368 | 1.68E+013 |
| | 384 | 1.67E+013 |
| | 400 | 1.61E+013 |
| | 416 | 1.60E+013 |
| | 432 | 1.58E+013 |
| | 448 | 1.58E+013 |
| | 464 | 1.53E+013 |
| | 480 | 1.46E+013 |
| | 496 | 1.41E+013 |
| | 512 | 1.37E+013 |
| | 528 | 1.38E+013 |
| | 544 | 1.36E+013 |
| | 560 | 1.32E+013 |
| | 576 | 1.26E+013 |
| | 592 | 1.25E+013 |
| | 608 | 1.23E+013 |
| | 624 | 1.18E+013 |
| | 640 | 9.10E+012 |
| | 656 | 1.09E+013 |
| | 672 | 1.14E+013 |
| | 688 | 1.13E+013 |
| | 704 | 1.08E+013 |
| | 720 | 1.04E+013 |
| | 736 | 1.06E+013 |
| | 752 | 1.08E+013 |
| | 768 | 1.08E+013 |
| | 784 | 9.85E+012 |
| | 800 | 9.70E+012 |
| | 816 | 9.85E+012 |
| | 832 | 9.82E+012 |
| | 848 | 8.67E+012 |
| | 864 | 8.52E+012 |
| | 880 | 7.84E+012 |
| | 896 | 6.25E+012 |
| | 912 | 5.62E+012 |
| | 928 | 4.35E+012 |
| | 944 | 3.51E+012 |
| | 960 | 2.77E+012 |
| | 976 | 2.46E+012 |
| | 992 | 2.75E+012 |
|  |