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Analog or Digital?

You should be pretty warmed up for “Ask The Experts” by now. Here’s the last of those three conundra. It’s the one that usually provokes the greatest debate.

People over-think this. In very many cases it really does not matter how a filter transfer function is implemented. You should be guided by what is a good fit on the system architecture that’s already winning your heart/mind on other grounds.

The reason is clear: Signal processing should ideally not be a source of signal path deterioration in your signal. An RF front end, for example, should have an SNR dominated by the first stage. What you do to the signal after that — amplify, sample, filter — should not degrade it. If you follow this guideline, then it simply does not matter in which domain the filter math gets carried out.

When you know that there will be some domain-crossing involved, there’s more of a choice to make. If you’re going to start analog and end digital, and some filtering is needed, you could do it in either domain. However, if the primary purpose of the filtering is to elevate the quality of the subsequent conversion to digital, then you just answered your own question — look at doing the filtering in the analog domain — or at least enough filtering that the conversion quality is good enough.

Likewise, if you’re going to start digital and end analog, consider whether the process of converting your signal back to analog is going to generate additional stuff you don’t want. The architecture of the DAC you use plays a role here. Delta-sigma DACs tend to produce much less “hash” around the sample rate than regular sampling DACs. But, then, that’s because the manufacturers of those delsig DACs already built the filtering in, so you don’t have to.

And that highlights another issue. You may not have to do any filtering yourself, because the very helpful manufacturers may have integrated it into one of the devices you plan to use. The most you have to do then is just feed the device some configuration parameters. Sometimes not even that. This is how the majority of audio filtering is done these days: a little farm of transistors grazing away on your signal inside a chip somewhere, with zero effort on your part.

Hopefully your gray matter is now alight with questions and comments about filtering. Let 'em rip! And see you on the 22nd!

Please join us on Wednesday, October 22nd, at 1:00 p.m. ET (10:00 a.m. PT) for a chat session in which we will discuss “Filter Design.”

Sign up now by clicking here to join or to leave an early message! Just click “Reply” or “Post Message” when you get to the site.

35 comments on “Analog or Digital?

  1. Myled
    October 21, 2014

    “Likewise, if you're going to start digital and end analog, consider whether the process of converting your signal back to analog is going to generate additional stuff you don't want.”

    Kendall, what are these additional stuffs? You meant about the spikes and noises.

  2. Netcrawl
    October 21, 2014

    @Myanalog for me the digital revolution has been notable in reshaping the nature of the analog market, in an analog world, analog ICs were largely assigned to signal processing roles and although some of the hottest new digital multimedia products involve audio/video signal processing. The growth of these digital equipments have boosted the interface and power management segement of the analog IC market at a faster rate than the analog processing segment.

    Analog still represents the largest single revenue category in digital mobile handsets. Baseband, RF, as well as power needs, are handled by analog ICs and the mobile handsets have been one of the most important drivers of the analog market.

  3. bjcoppa
    October 22, 2014

    I served as a patent examiner on many projects associated with this tech previously. There is still a lot of tweaks high power electronics companies are making to DACs and related components. Most of the innovation is in regards to schematic layouts and signal processing. However the components themselves vary only slightly from one generation to the next.

  4. samicksha
    October 23, 2014

    I agree you @Netcrawl,  analog power management chips continue to advance, improve performance and I am little curious to see how this analog market shall repond to IoT .

  5. Myled
    October 24, 2014

    “Analog still represents the largest single revenue category in digital mobile handsets. Baseband, RF, as well as power needs, are handled by analog ICs and the mobile handsets have been one of the most important drivers of the analog market.”

    Netcrawl,  thanks for this clarification.

  6. Myled
    October 24, 2014

    ” analog power management chips continue to advance, improve performance and I am little curious to see how this analog market shall repond to IoT .”

    Samicksha, but one day it has to be digitalized, am I right.

  7. samicksha
    October 24, 2014

    I cannot deny the fact but yes again we still have to wait for complete digital communication. As if now Analog is imporatant to survive.

  8. bjcoppa
    October 24, 2014

    Great job Kendall with the Chat Session this week. You covered many relevant topics to this post and others published recently. I have dealt with quite a bit of IP on DACs this past year as innovation continues but only incrementally.

  9. Netcrawl
    October 25, 2014

    @samicksha analog is here to stay, its everywhere, in fact two of the faster growing electronics products in the market- the handsets and digital TVs make extensive use of digital ICs, and they also use analog ICs in substantial volume.

    Another growth area for analog is the wireless-infrastructure market, WiFI base stations, etc. Analog provide the interface to these real-world applications as well as the digital world of processors and memory, wireless system use RF circuits these are considered part of analog world.

  10. PCR
    October 26, 2014

    Yes analoging, It was a very successful chat with covering all the key points and I really enjoyed it. 

  11. PCR
    October 26, 2014

    Netcrawl what about the mobile phone market which uses more wireless options?

  12. Myled
    October 29, 2014

    “I cannot deny the fact but yes again we still have to wait for complete digital communication. As if now Analog is imporatant to survive.”

    Samicksha, yes you are right. But tomorrow the scenario can be changed to digital communication.

  13. Myled
    October 29, 2014

    “Another growth area for analog is the wireless-infrastructure market, WiFI base stations, etc. Analog provide the interface to these real-world applications as well as the digital world of processors and memory, wireless system use RF circuits these are considered part of analog world.”

    Netcrawl, now a day's most of the communications are in analog mode but there is no doubt that one day it may be migrated to digital mode for better clarity and for other advantages.

  14. geek
    October 31, 2014

    “Another growth area for analog is the wireless-infrastructure market, WiFI base stations, etc. Analog provide the interface to these real-world applications as well as the digital world of processors and memory, wireless system use RF circuits these are considered part of analog world.”

    @Netcrawl: How exactly do you think the wireless communication be turned into digital? From what I know, wireless communication takes place through radio waves and by their nature they're analog and I don't think there's really a way to make them digital.

  15. Netcrawl
    October 31, 2014

    @tzubair analog signals are continous in both time and value, and that they are used in many systems, although their use has declined with advent of cheap digital signals. Analog will not disappear in a short time, but that's mainly because of some nontechnical reason such as the price, in the near future, all the drawbacks of the digital system will be overcomed, and more and more new technology will be available by applying digial technology.

  16. samicksha
    October 31, 2014

    I cannot deny the fact that future will move on with digital world, but i dont see this happening any time soon and more over still analog is considered to make good use of bandwidth.

  17. Sachin
    October 31, 2014

    I cannot deny the fact that future will move on with digital world, but i dont see this happening any time soon and more over still analog is considered to make good use of bandwidth.

    @samicksha, I agree with your opinion. I dont think digital will completely overtake analog. I think both analog and digital will co-exist because each of them have their own advantage.

  18. Sachin
    October 31, 2014

    Analog will not disappear in a short time

    @Netcrawl, I agree with you. We will still need analog circuits, such as a low-noise amplifier, to connect the sensors and output devices to the data converters. Moreover we will need analog circuits to interface with MEMS, optical circuitry (optoelectronics) etc.

  19. Netcrawl
    October 31, 2014

    @SachinEE Analog ICs are the perfect solution for smart power management in electronic products as they help electronics consume less power while maintaining power. Not just MEMS, we also witnessing the emerging applications of Analog ICs in LED lighting systems. Analog ICs are being increasingly used in LED applications because of their power-efficient functions, the demand for LED lighting systems is growing as they consume less power and provide more brightness. LEDs are widely used in industrial, commercial and household lighting solutions, they are also gaining ground in the automotive space. Thus, the growing demand for LEDs is leading to increasing usage of Analog ICs.

  20. Myled
    November 5, 2014

    “I cannot deny the fact that future will move on with digital world, but i dont see this happening any time soon and more over still analog is considered to make good use of bandwidth.”

    Samiksha, I hope it will happen soon because some of the state government started such initiatives, especially for police telecommunication.

  21. samicksha
    November 9, 2014

    I agree you here, but even in telecommunication most of towns / areas are getting served by Microwave links and Microwave Radio. May be where Fiber is not available.

  22. samicksha
    November 9, 2014

    You are right @Sachin, to add on more than advantage, it is about using services efficiently.

  23. Davidled
    November 9, 2014

    If manufacture integrates all functionality and parameters are tuned in the device, there might be potential limitation for redesigning the circuit which might be required for a special purpose.

  24. uchiha
    November 9, 2014

    @DaeJ: What sort of limitations are you referring to here? Also is the re-designing necessary?

  25. Davidled
    November 10, 2014

    At the condition that analog and digital circuit highly integrated, there would be a lot of limitation to change the integrated circuit itself except the interface circuit or signal conditional circuit. Then, engineer has a limitation for testing and troubleshooting of the integrated chip, unless there is a detail circuit diagram in the datasheet.

  26. Myled
    November 13, 2014

    “I agree you here, but even in telecommunication most of towns / areas are getting served by Microwave links and Microwave Radio. May be where Fiber is not available.”

    Samiksha, I think microwave links are using only as a redundancy channel, in case of disaster. 

  27. nasimson
    November 29, 2014

    @ Myanalog @Samiksha

    > I think microwave links are using only as a redundancy channel, in case of disaster. 

    That depends on network planning. 3G GSM network can run on microwave at the BTS level. At the hub BTS sites where traffic is aggregated, fiber will be needed.

  28. Myled
    December 3, 2014

    “That depends on network planning. 3G GSM network can run on microwave at the BTS level. At the hub BTS sites where traffic is aggregated, fiber will be needed.”

    Nasimson, thanks for this clarification and you are right. But I think they are not using microwaves for day to day basis.

  29. nasimson
    December 27, 2014

    @Myanalog:

    > But I think they are not using microwaves for day to day basis.

    If fiber is already laid out. Its the better model in terms of opex, speed, reliability and weather resilience.

  30. Myled
    December 29, 2014

    “If fiber is already laid out. Its the better model in terms of opex, speed, reliability and weather resilience.”

    Nasimson, I meant the same. Microwares are using as a redundant channel.

  31. Sachin
    December 31, 2014

    Not just MEMS, we also witnessing the emerging applications of Analog ICs in LED lighting systems.

    @Netcrawl, I totally agree with you. MEMS and LED lighting requirements will definitely help improve demand for Analog IC designs in future.

  32. Sachin
    December 31, 2014

    I hope it will happen soon because some of the state government started such initiatives, especially for police telecommunication.

    @Myanalog, is there any advantage if that process of moving to digital happens faster ?

  33. Sachin
    December 31, 2014

    May be where Fiber is not available.

    @samicksha, True but slowly but steadily fiber usage is becoming common. Telecom providers are putting lot of effort in building infrastructure by laying fiber cables.

  34. Myled
    January 2, 2015

    “is there any advantage if that process of moving to digital happens faster ?”

    SachinEE, yes. You can Google for it and see the results. Am unable to provide any links here because of the restrictions from our site. 

  35. Myled
    January 5, 2015

    “True but slowly but steadily fiber usage is becoming common. Telecom providers are putting lot of effort in building infrastructure by laying fiber cables.”

    SachinEE, fiber is the best and most of the communication/data transfer prefers optical fiber connectivity too.

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