Great disassembly job. There's yet another branch of the rabbit hole that Tom almost fell down:
... the multiplier is based on a classic form,
having a translinear core, supported by three
(X, Y, and Z) linearized voltage-to-current
converters, and the load driving output amplifier.
I have no clue how the thing works!
The 'translinear' school of design was founded (or at least popularized) by Barrie Gilbert at Analog Devices (https://en.wikipedia.org/wiki/Translinear_circuit , https://en.wikipedia.org/wiki/Barrie_Gilbert ). Gilbert was one of the undisputed GOATs in the analog field and a full-fledged Renaissance man in his own right. It's worth reading more about him if/when you have the time and inclination.
It would be interesting to benchmark this against consumer USB DACs that are marketed for sound. You can get 32-bit 192kHz bandwidth (384kHz sampling rate) DACs now for under $200. Obviously this is much lower bandwidth than the R&S, but I'd be interested to see the dynamic range of a modern DAC when approaching Nyquist; I don't have a strong belief one way or the other over which would win, given that 14-bits of dynamic range is about where the integrity of your analog path starts to matter a whole lot.
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Sound Blaster claims "up to" 130dB of dynamic range on theirs. Putting aside how much work the "up to" id doing, this would make the last 9 or 10 bits completely useless, even for undithered signals, but I was thinking of something cheaper, by one of those fly-by-night companies with names made of random letters.
I'm trying really hard not to want to turn this into a dac for my stereo system. They build really nice boxes..
I have a PSL-3 industrial controller (well, two, but one is broken) on the shelf behind me that I'm using for the noble purpose of playing Theme Hospital in Windows 98.
I'm amused that it's just a PC motherboard, and that it uses ISA to talk to the generator hardware itself. Makes perfect sense; nothing needs high data rates there, and it's really easy to interface with. I just wouldn't have necessarily predicted it before seeing the case open.
Wonderful article and I don't even know that this device existed perhaps due to Agilent/Keysight bias laboratory/shop.
R & S AMIQ Modulation Generator general specs is available here [1].
Fun facts, the venerable Silicon Valley was started by Hewlett-Packard (HP, then Agilent, now Keysight) that mainly supplying function/signal/waveform generator for the then booming radar and electronics industry.
HP Garage is now a designated landmark and marked with a plaque calling it the "Birthplace of 'Silicon Valley' " [2].
Rohde and Schwarz AMIQ Modulation Generator Teardown
(tomverbeure.github.io)64 points by iamsrp 8 June 2025 | 25 comments
Comments
[edit]
Sound Blaster claims "up to" 130dB of dynamic range on theirs. Putting aside how much work the "up to" id doing, this would make the last 9 or 10 bits completely useless, even for undithered signals, but I was thinking of something cheaper, by one of those fly-by-night companies with names made of random letters.
I have a PSL-3 industrial controller (well, two, but one is broken) on the shelf behind me that I'm using for the noble purpose of playing Theme Hospital in Windows 98.
There are probably only a few electrical engineers in the entire world that actually use this stuff on a day to day basis.
R & S AMIQ Modulation Generator general specs is available here [1].
Fun facts, the venerable Silicon Valley was started by Hewlett-Packard (HP, then Agilent, now Keysight) that mainly supplying function/signal/waveform generator for the then booming radar and electronics industry.
HP Garage is now a designated landmark and marked with a plaque calling it the "Birthplace of 'Silicon Valley' " [2].
[1] Rohde & Schwarz – AMIQ04 I/Q Modulation Generator:
https://testworld.com/product/rohde-schwarz-amiq04-iq-modula...
[2] Hewlett-Packard:
https://en.wikipedia.org/wiki/Hewlett-Packard