A response to “4 Things I Noticed about Keysight’s New MXR Oscilloscope”

Recently, Tektronix Product Manager Brandon Gould posted a blog with his thoughts about how our all-new Infiniium MXR-Series oscilloscope falls short against their 5 Series and 6 Series B. If you look around Keysight’s website, you’ll notice a distinct lack of competitive comparisons for many of our new oscilloscopes – I believe that most consumers by now are weary of manufacturers self-claims of superiority in the internet. But, these comparisons do have their place, especially when there aren’t too many (or any) third party reviews.

But in light of Brandon’s assessment of our new Infiniium MXR-Series, perhaps some playful competitive banter is warranted. A fun history lesson – Keysight (then Agilent) and Tektronix had a public “duel” between product managers back in 2005, which you can read about here in EE Times. It was all in good spirit, and ultimately gave the engineering community more information and data to make informed decisions. It's worth a read if you are an unashamed oscilloscope fanboy like I am.

I’ll share my own thoughts on how our new MXR-Series stands up to Tektronix’ 5 Series and 6 Series B, in case you are lucky enough to be in the market for a new oscilloscope today! I say this with all sincerity – there has never been a better time to buy an oscilloscope. Whether it’s from Keysight, Tektronix, or anyone else – there are some fantastic tools with never before seen performance, and if this is your first time in the market in a while, then make sure you’re sitting down. These aren’t your grandfather’s oscilloscopes. And I know that firsthand, as my grandfather (former electrical engineer) barely recognized these, haha.

Please note that the contents of this blog are as of April 2021, and obviously contain a mixture of my personal opinion and hard data as appropriate. Also note that the MXR-Series and EXR-Series share many features and functions, and most of this analysis is applicable to either product. Check data sheets for specifics, as usual.

Usability

Brandon's first comments are dedicated to the audible noise of the MXR-Series. This is specifically due to the server-class power supply we use in the platform to maximize reliability and airflow. This audible noise is something we are acutely aware of and are working towards fixing with a new fanless design. We’ll ask Brandon to amend his review as soon as we implement the quieter power supply, and will remove this paragraph as well – but if you happen to catch this, consider yourself an early adopter of this blog article 😊. Throw a “whoosh” my way on Twitter (@KeysightMike) to stake your claim to history.

As far as the user interface goes – this is all subjective, of course. Brandon understandably wishes that Infiniium had some of the new usability features of the Tektronix user interface (UI), but I believe that our current Infiniium UI is much more flexible and scalable. Infiniium offers dynamic and user-definable scaling of menus and buttons that track with your use model (touch or mouse/keyboard), while offering a no-nonsense menu structure that makes tools easy to find and use. It also ensures 100% backwards compatibility and ease of adoption for the tens of thousands of satisfied Infiniium users worldwide. Here’s a short demo of things you can to with Infiniium’s UI.

Again, this is totally subjective, and of course I prefer Infiniium – I use it every day! I suggest that you contact your local Keysight Authorized Reseller or local Sales Engineer for a free evaluation of Infiniium and decide yourself.

There are some objective comparisons though – Infiniium offers Quick Setups for many features such as measurements, eye diagrams, jitter analysis, FFTs, and more. We also offer Setup Wizards for more complex measurements to aid in ease of use and measurement repeatability. Consider these tools as “Autoscales” for the most complex of signal analysis. Tektronix has not implemented any comparable usability feature yet, after nearly 4 years of updates. See this short video to learn more about our Quick Setups, Wizards, and built-in help:

Here is a short side by side video of getting a simple eye diagram and some basic jitter plots on screen with an EXR-Series and a Tektronix 5 Series. Let me know in the comments which is more usable, in your opinion. (note: After making the video, I realised the Tektronix box was able to lock on the data rate and create a stable eye easier after I manually made the memory depth deeper. But the point still stands that their software wasn't able to recover the clock without intervention from the user, or instruct the user on what to do next.)

Infiniium also offers the Fault Hunter tool, which takes advantage of our hardware triggering, fast waveform plotting, and automatic measurements to auto-detect faults in your signal. Below is a short primer on Fault Hunter, or check out this blog explaining some more background on the usefulness of such a tool. A feature like this isn’t possible on Tektronix’ architecture, perhaps because fast update rate (using FastAcq) has limitations, including the quality of the plotted waveform, or inability to use certain features like their visual trigger. Perhaps we will see a comparable feature in the future from Tektronix, but for now, it is only found on Keysight Infiniium oscilloscopes.

Below is a short video explaining how Fault Hunter works, as well as a side-by-side comparison of triggering tools and capabilities with the Tektronix 5 Series.

Acquisition Capability

Brandon notes that our MXR-Series has worse ENOB, SNR, and Noise than their 6 Series B, which is true. Let’s take a look at some basic specs of the MXR-Series, 5 Series and 6 Series B.

Table 1: A few basic signal integrity related specifications of Keysight and Tektronix oscilloscopes

As you can see, the MXR-Series perform much better than the 5 Series, while falling just short of the 6 Series B. Tektronix has made some impressive hardware in their new platform. Though if we quantify how much better, you’ll see that we’re splitting hairs. The MXR-Series sits in between the Tek 5 and Tek 6B, with a different of about 5-7% in ENOB either way. Noise is also pretty close as well – I’ve opted to represent it as a percentage of full scale since Keysight and Tektronix use different numbers of vertical divisions across the screen.

Brandon's blog was pretty short on this topic of ADC bits, basically pointing to the ADC resolution of 12 bits on their platforms vs. 10 bits on MXR-Series. Check out this blog and download the white paper to learn why it’s not always just about the bits – the entire system needs to be taken into account! In fact, our MXR-Series architecture allowed for up to 18 bit digitization, but we capped it at 16 bits, because the extra "glamour bits" would have not contributed to more measurement accuracy whatsoever - they were lost in the noise.

Honestly, all of these oscilloscopes have fantastic signal integrity, as you would expect from the top two oscilloscope manufacturers’ latest and greatest technology, and you’re not getting fired for selecting one or the other based on signal integrity alone.

Here is more data relating to acquisition performance – namely the basics of memory, sample rate, and bandwidth. The MXR-Series offers 6 GHz and 16 GSa/s across all 8 channels with no interleaving – perfect for leading applications such as 25GBASE-T, or pairing with our 6 GHz Power Rail Probes for checking signal integrity of your PDN. The MXR-Series also pairs well with our exclusive Power Integrity Application, which can show correlation between power rails and switching devices in your design. You can also use the 8 phase coherent channels to test 8x8 MIMO signals by exporting IQ data to Pathwave VSA software (in conjunction with the RTSA/DDC option).

The MXR-Series also offers an industry-leading 200 megapoints of memory per channel, standard – which saves you a ton of money vs. buying expensive memory upgrades, especially important when working with higher sample rates. Without deep memory, your high performance oscilloscope will chew through memory in milliseconds or less.

Table 2: Banner specification comparison between Keysight and Tektronix oscilloscopes

Triggering and Channel Flexibility

Brandon notes here how many advanced triggers are missing in the MXR-Series from channels 5 through 8. This was a tough engineering decision made due to the architecture of the MXR-Series platform, where dual threshold triggers would be limited to the first four channels. If you are one of the many folks who are just in the market for a 4 channel oscilloscope, this is a non-issue. For those with 8 channel needs, we simply ask you swap channels you need to trigger on to one of the first four. Hopefully a one-time setup consideration!

As far as channel flexibility - the MXR-Series offers 8 analog channels (that can also act as RF inputs, see the next section), and 16 dedicated digital channels. The key word here is "dedicated". With Keysight, you can have all 4 or 8 analog channels and 16 digital channels at once.

The Tektronix 5 Series and 6 Series B require users to sacrifice analog channels to use digital channels, to the tune of 8 per input. For the traditional 4 analog + 16 digital MSO setup, you need to opt for a 6 or 8 channel model and purchase two 8 channel MSO probes with Tektronix, as you will lose two analog channels to have 16 digital inputs. For customers who want more than 16 digital channels, the Tektronix architecture could be advantageous, as it allows for up to 64 digital channels (with zero analog channels), but at that point, I might recommend a dedicated logic analyzer depending on your workflow.

From an oscilloscope nerd's standpoint (i.e. me), the new Tek FlexProbe interface is definitely innovative, though I am not completely sold on it being an upgrade from the usual dedicated logic probe setup. If I were their product manager, I'd have pushed for a seperate 64 channel logic pod probe and left the analog channels alone, but I am sure there are other engineering considerations there with resource management and how their chips are designed.

Integrated Spectrum Analysis

This is a fun topic, as the idea of using oscilloscopes as wideband signal analyzers is a somewhat new concept that has been gaining more steam as of late. Tektronix introduced their MDO line of oscilloscopes nearly a decade ago, but at that point, IoT was more of a buzzword than a real industry need. That’s changed. Looking at the frequency domain is no longer relegated to special EMI labs, radar applications, or otherwise “separate” from the digital designer. Tektronix’ SpectrumVu mode on the 5 and 6B Series is clearly an evolution of the MDO concept. Our Infiniium UXR-Series, with 110 GHz of real time bandwidth, is often used as a way to affordably look at signals in the E-Band or mmWave band with four phase coherent channels. Much of this performance capability is thanks to the genius design of the UXR-Series analog front end (256 GSa/s on 4 channels at once… still blows my mind) as well as an all-new ASIC that acts as an oscilloscope on a chip.

Image1: Me, using my MXR-Series RTSA feature, to prove my ISP wrong... they claim my WiFi cutouts are due to "local interference" or "my microwave"... Little did they know, I have $250,000 of test equipment in my living room!

This groundbreaking ASIC technology has bled it’s way down to the MXR-Series. Today, this chip can manage acquisition memory, plotting, triggering, hardware FFT calculations, downconversion to IQ data, and more. This gives fantastic performance in the time domain, but also contains blocks in the design geared for RF analysis. The world’s first oscilloscope-based real time spectrum analyzer is the first feature we’ve released that leverages the awesome power of this ASIC, with more features to come. I’m personally excited about this ASIC, as it’s going to let the MXR-Series constantly evolve over the coming years as new features are unlocked and made available to our subscribing customers.

That being said, there are some limitations today to our DDC and RTSA features. Here’s a short explainer:

To view the time and frequency domains at once, you are limited to the traditional (and standard feature) FFT math function. But with 8 phase coherent, 2 GHz wide channels of IQ data being fed into Keysight’s Pathwave VSA software, 8x8 MIMO and other wireless tests can be done at a fraction of the cost and test time as the traditional methods of using spectrum analyzers. And a 320 MHz RTSA is an exclusive debugging tool that gives you 100% POI on 15 us signals at a fraction of the cost of a traditional spectrum analyzer, with all the added benefits of a real-time oscilloscope!

We also understand RTSA is a niche tool for a subset of power users today – don’t hesitate to reach out with questions, comments, or things you’d love to see oscilloscopes of the future help you with, so we can innovate right along side you for decades to come.

Conclusion

I’d like to thank everyone in our R&D labs for creating such a fun product to advocate for, and also to the folks at Tektronix for creating such awesome products for Keysight to compete with – iron sharpens iron, and the real winners here are the folks using our test equipment to make the world a safer and more connected place than ever before. Shoot me a tweet if you have any questions, comments, thoughts, rants, raves, or requests for future blogs. And I hope to see you all on a future episode of EEs Talk Tech once we’re allowed back in the office again 😊

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