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EVLA SAMPLERS

EVLA SAMPLERS. High speed wide band 3-bit for most bands Lower speed narrower band 8-bit for bands with RFI. 1. HIGH SPEED SAMPLER. 2GHz bandwidth 3-bit 4096 Msamples/sec. Specifications nearly identical to ALMA. Simpler clock requirements, EVLA doesn't require variable clock phase.

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EVLA SAMPLERS

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  1. EVLA SAMPLERS • High speed wide band 3-bit for most bands • Lower speed narrower band 8-bit for bands with RFI. 1

  2. HIGH SPEED SAMPLER • 2GHz bandwidth 3-bit 4096 Msamples/sec. • Specifications nearly identical to ALMA. • Simpler clock requirements, EVLA doesn't require variable clock phase. • Uses sampler chip being developed for ALMA. • ALMA schedule compatible with EVLA. 2

  3. HIGH RESOLUTION SAMPLER • Low frequency band RFI environment requires high resolution sampler. • 8-bit 2048 Msamples/sec 1GHz bandwidth. • 8-bits parts are commercially available that operate at 1.5Gsamples/sec. that support 2:1 interleave. • Implications for threshold level matching and sampling clock skew. 4

  4. LEVEL MATCHING • Parts guaranteed for ½ LSB absolute errors. • 2:1 interleave puts level matching artifacts at DC and Nyquist frequency. 6

  5. SAMPLING CLOCK SKEW • Clock phase between sampler chips must be closely controlled at 180 deg. • Skew between samplers creates images symmetric around frequency 0.25. • This is a feature that can be easily detected and used to automatically trim clock phase by module microcontroller. • Could potentially use PCAL or other test signal. 7

  6. MAX 108 FAMILY • MAX 108 1.5 Gsa/sec. MAX 104 1.0 Gsa/sec. • Designed to support interleaved operation. • 2.2GHz analog input bandwidth. • >7.5 ENOB at -3dB FS published performance. • Correlator processing in high resolution modes is to be 7 bits plus sign. • Only 8 bit commercial parts available at this speed. 9

  7. RFI-DEFENSE IN DEPTH • Circuit Design • Component Selection - connectors • Board Design • Packaging 10

  8. CIRCUIT DESIGN • Differential signaling techniques. • Ground,shielding and power organization. • Component selection. 11

  9. BOARD LAYOUT • Stripline transmission line techniques. • Multilayer with ground and power planes on outer layers. • Careful attention to isolation of separate ground and power planes. • RFI is consistent with good high speed electrical performance. 12

  10. PACKAGING • 3 samplers and data transmitter in a single module. • Careful shielding of analog input circuitry from digital sections. • Careful power distribution within module. • Minimize external penetrations. • Extended height module with honeycomb filter. 13

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