UADC4 Universal Analog to Digital Converter for ZERO IF receivers - - PowerPoint PPT Presentation

UADC4

Universal Analog to Digital Converter for ZERO IF receivers

EME Conference 2018 Alex Artieda, ZS6EME 18/08/2018 1

by Alex Artieda, ZS6EME

Agenda

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• Introduction
• Are ZERO IF receiver ‘old Technology’?
• PC Audio cards are for music, limiting factor
• UADC4 design

– ADC – Buffer stage – Clock – PCB layout (4 layers)

• UADC4 performance
• Questions?

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Are ZERO IF receiver ‘old Technology’?

• Mixers create always unwanted signals
• Phase noise in the LO affect ‘reciprocal mixing’
• DDC enthusiast said YES!! It’s old technology

DDC Promise

• Sampling on the antenna
• Use of NCO (Numerical controlled oscillator)
• Big amount of band width....in milliseconds
• Phase noise and reciprocal mixing are not

problems any more.

Cool!!!, looks promising...BUT....

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Are ZERO IF receiver ‘old Technology’?

DDC Promise

• Perspective for amateur radio communications
• Sampling big amount of BW, is necesary?, MORE is better?
• What about Dynamic range?..MORE is always better
• What the market can delivery today?
• Implementation cost?

DDC Technology, today, lack of enough Dynamic Range and have excess of BW for amateur radio applications

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PC Audio cards are for music, limiting factor

• For more then 20 years Amateur radio operators use PC Audio

cards ‘as ADC’ units, success was great until those audio cards cannot add any bit more of performance

Why?

Audio cards, even with sampling at 24bits, limit their best characteristics to just 20KHz of band width Our ears and brains cannot process signal beyod that limit. Why manufactures will extend perfect performance over that limits?

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PC Audio cards are for music, limiting factor

THE LIMIT IS THERE!!

JUST 20KHz OF GOOD PERFORMACE THE REST IS JUST MARKETING!!

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• The ADC

UADC4 Design

• Sampling up to 768 KHz, 32 bits
• Keep excellent performance up to 192KHz, 24 bit
• Up to 121 dB dynamic range in single mode.
• Up to 124 dB dynamic range in 4 to 2
• Up to 127 dB dynamic range in 4 to 1

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• Buffer stage by the Manufacture

UADC4 Design

Not really a good one!!

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UADC4 Design

• Clock

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PCB Layout (4 layers)

Signal layer

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Power Layer

PCB Layout (4 layers)

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PCB Layout (4 layers)

GND2 Layer

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PCB Layout (4 layers)

Signal2 Layer

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UADC4 Performance

• All test done with the support of Leif SM5BSZ
• UADC4 proto3 has excellent flat noise response up to 192KHz
• Harmonics are aprox 85dB attenuated.
• Cross talk about -110dB
• Using the WSE converters the noise floor improve 10 to 15dB
• Using the IQ+ modified improve is 11dB
• Dynamic range in the range of 121dB

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UADC4 Performance

Comparative results with PC sound cards is available at: http://www.sm5bsz.com/linuxdsp/hware/ensemble.htm Videos in YouTube:

• https://www.youtube.com/watch?v=b13k78oERpI
• https://www.youtube.com/watch?v=YGF8dofRWO8
• https://www.youtube.com/watch?v=hS6MymYLh1Q

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Questions?