Teardown & Analysis of a Keysight InfiniMax III N2802A 25GHz Active Probe - Page 1
Forum section: electronics / testgear

author: Hugoneus
author_rank: Frequent Contributor
timestamp: September 05, 2015, 04:11:19 pm
content: A close look at the Keysight 25GHz active probe!Watch the video here: [23 Minutes]youtu.be/jnFZR7UsIPEMore videos at The Signal Path:http://www.TheSignalPath.com

author: Lukas
author_rank: Frequent Contributor
timestamp: September 05, 2015, 04:32:23 pm
content: Just for comparison someone took apart a 7GHz active probe:https://www.eevblog.com/forum/testgear/ininiimax-7ghz-active-differential-probe-teardown/.For anyone interested in how the thickfilm microwave circuit is made:https://patents.google.com/patent/US20040257194A1/en.Seems like the different bandwidths (16/20/25/30 GHz) are more than just DSP, since an "upgrade" requires sending the probe back to Keysight. Maybe they're binning the probe amps?

author: HighVoltage
author_rank: Super Contributor
timestamp: September 05, 2015, 07:14:45 pm
content: That was an impressive tear down.Thank you

author: Hugoneus
author_rank: Frequent Contributor
timestamp: September 06, 2015, 12:37:09 am
content: Quote from: Lukas on September 05, 2015, 04:32:23 pmI am almost sure that they bin those amplifiers. They did the same for the scopes as well. Upgrade beyond a certain bandwidth has to have the acquisition board front-end replaced.

author: Berni
author_rank: Super Contributor
timestamp: September 06, 2015, 11:44:45 am
content: Very interesting teardown.Bears quite a few similarities to the 7GHz probe that i did a teardown of. Quite a bit more going on in this one rather than just a single ASIC solution. But as a result i don't think the 7GHz probe has as much common mode offset range.Even the old HP 1152A 2.5GHz active probes have some calibration data inside the eeprom. I noticed that that probe appears like it has zero signal delay since the scope reads the probes propagation delay and offsets your trace to match.(Or HP has used a coax cable that carries a signal faster than light speed, but i assume i would have heard about it)

author: Hugoneus
author_rank: Frequent Contributor
timestamp: September 06, 2015, 07:46:07 pm
content: Some really funny Google caption generator:Wow...

author: Bud
author_rank: Super Contributor
timestamp: September 06, 2015, 08:00:30 pm
content: Now you can have a good idea where google driverless car may take you

author: electr_peter
author_rank: Unknown
timestamp: September 06, 2015, 08:16:09 pm
content: Cable - amplifier connection is a bit dodgy for such kind of probe. Keysight at least could put some hot glue to make it more robust. Think about it - one small cable (power or bias) breaks and you have just lost $20k

author: AF6LJ
author_rank: Unknown
timestamp: September 06, 2015, 08:39:25 pm
content: Good video thanks.

author: AF6LJ
author_rank: Unknown
timestamp: September 06, 2015, 08:40:30 pm
content: Quote from: electr_peter on September 06, 2015, 08:16:09 pmThey might be relying on the possibility that lower order primates wouldn't be using this probe.

author: Berni
author_rank: Super Contributor
timestamp: September 06, 2015, 09:31:11 pm
content: Yeah the 7GHz probe i was looking at also had wires just stuffed in there all loosy goosy. But the cable strain relief covers it up. The part that looks more worrisome to me is the brunt of the force is carried by the naked piece of coax from where the cable is stripped up to where its joined in to the metal body. That seams to be the most bendy part of it.But then again when you know the probe in your hands costs 20 grand you do tend to handle it with a LOT of care. For most active probes the manual will also say to treat the amplifier end with care since these fancy ceramic hybrid modules are pretty fragile on there own (And even more fragile electrically).

author: AF6LJ
author_rank: Unknown
timestamp: September 06, 2015, 09:37:40 pm
content: Quote from: Berni on September 06, 2015, 09:31:11 pmThis is the case. and a solution for anchoring the cable better at the probe end may not have been possible without impairing the usability of the probe. (IDK maybe maybe not)Every time I would see a tech spin an N connector while attaching it to a piece of 50K gear I would cringe.Thankfully I found out later some of that gear was built to have the center pin of the N connectors replaced when the lower order primates had their way with them.

author: donmr
author_rank: Regular Contributor
timestamp: September 07, 2015, 04:09:23 pm
content: Good video, thanks.The terminator on the 2nd IC output (50 ohm resistor we assume) looked interesting. It appears to have some sort of plastic cover on it. Does that come off?

author: Berni
author_rank: Super Contributor
timestamp: September 07, 2015, 05:12:55 pm
content: Quote from: donmr on September 07, 2015, 04:09:23 pmIts not a cover. All the resistors are thick resistive material like that and then they are laser trimmed to the exact value, see a few others and you will see a similar thing at the edge of them where part of the resistor was etched away. Similar thing in my 7GHz probe but the laser trimming left some residue around it making it look like that resistor blew up.