Mystery project?! Will post more info soon..... - Page 1
Forum section: electronics / projects

author: c4757p
author_rank: Super Contributor
timestamp: March 11, 2015, 07:27:03 pm
content: I've been working on this project for months now - any guesses what this thing does?(Genuinely curious - some of the hardware's pretty vague, unless you're quite good at figuring out what certain chips are, and then you might be able to get a pretty good guess!)Working on finalizing the hardware now... will be done in a few days, then fab time... I'll post about it then. We have a beautifully working prototype.Software and documentation are a couple months away.Development has been out in the open since the beginning - no snooping around the Web, or, no posting if you do!

author: max_torque
author_rank: Super Contributor
timestamp: March 11, 2015, 07:36:59 pm
content: USB oscilloscope / signal generator??

author: Stonent
author_rank: Super Contributor
timestamp: March 11, 2015, 07:37:34 pm
content: You reverse engineered an Atten scope?

author: c4757p
author_rank: Super Contributor
timestamp: March 11, 2015, 07:38:43 pm
content: "Signal generator" has shades of correctness, in that, there kinda-sorta is oneNot a scope.

author: Stonent
author_rank: Super Contributor
timestamp: March 11, 2015, 07:41:00 pm
content: Quote from: c4757p on March 11, 2015, 07:38:43 pmWell I'll take a stab at !(Frequency Counter)

author: krish2487
author_rank: Frequent Contributor
timestamp: March 11, 2015, 07:42:03 pm
content: I am guessing a fairly decently specced 2 channel oscilloscope with a waveform generator.The 2 INPUTS and OUTPUT are kind of a giveaway. Well, at any rate something around a similar functionality.U4 is the ADC (two sets of differential inputs are kind of a dead giveaway)U18 is a small to mid sized for FPGA for the glue logic of the scope.U6/U7 being a DAC / buffer combination.And I am kind of going out on a limb here, the bandwidth is likely to be more than 500 MHz, I m guessing about 1 ~ 1.5 Ghz.[The square box on the top layer kind of indicates a metal shield)So what did I win???

author: krivx
author_rank: Frequent Contributor
timestamp: March 11, 2015, 07:45:26 pm
content: The hole in the lower left is really close to a 5V trace, careful torquing down any screw that goes in there.edit: also the answer is on github for anyone interested

author: c4757p
author_rank: Super Contributor
timestamp: March 11, 2015, 07:46:59 pm
content: Quote from: krivx on March 11, 2015, 07:45:26 pmGood point, I'll move that. Thankskrish:Quote from: c4757p on March 11, 2015, 07:38:43 pm

author: jmole
author_rank: Regular Contributor
timestamp: March 11, 2015, 07:47:40 pm
content: looks like the two inputs are mixed together with some analog stuff, so I don't think it's a scope. I'll guess it's an SDR of some kind, although I don't know why two inputs would be necessary...

author: krish2487
author_rank: Frequent Contributor
timestamp: March 11, 2015, 07:48:42 pm
content: I am guessing a kind of spectrum analyzer then with a tracking gen!PS: About figuring out the functionality of the chips, was I anywhere close to the actual design or wat it just nonsense?

author: SeanB
author_rank: Super Contributor
timestamp: March 11, 2015, 07:50:02 pm
content: 2v inputs, shielded section around them, then a lot of filtering and what looks suspicously like a double balanced mixer, then a simple low pass filter leading off to what looks like a fairly high power MCU in one of 2 pinouts. Output looks like the tracking oscillator, or a second frequency output, 50R output impedance and so a good guess is it is a spectrum analyser with 2 selectable inputs, with the options being either an onboard LCD display, or to communicate via USB with a host computer for sweep and display.

author: babysitter
author_rank: Frequent Contributor
timestamp: March 11, 2015, 07:53:28 pm
content: Vector Signal Generator, taking I+Q Baseband?

author: kolbep
author_rank: Frequent Contributor
timestamp: March 11, 2015, 07:56:31 pm
content: Nope, I thought an Image search might have revealed something.But dropping your PCB onto google images only taught me 1 thing:your board design looks a lot like a slot machine :->

author: voja
author_rank: Contributor
timestamp: March 11, 2015, 08:07:41 pm
content: Not sure, but I think that I read "UNIFY GAIN" (pixelized text on the top)Maybe LATCH before it

author: teksturi
author_rank: Regular Contributor
timestamp: March 11, 2015, 08:08:49 pm
content: Maybe signal analyzer.

author: c4757p
author_rank: Super Contributor
timestamp: March 11, 2015, 08:13:12 pm
content: Quote from: voja on March 11, 2015, 08:07:41 pmI wondered how readable those would be - as, knowing what they do say, my eye tends to see readable words there.Apparently, not very readable.

author: voja
author_rank: Contributor
timestamp: March 11, 2015, 09:02:34 pm
content: QuoteIt's the power of suggestion. The only difference is that I suggested the wrong text to me

author: babysitter
author_rank: Frequent Contributor
timestamp: March 12, 2015, 05:22:26 am
content: Depixeling results in loss of data, but there had been news reports a few years ago about the sucessful deblurring of the face on photographs of some a**hole in canada who abused children. Why didnt you use that algorithm to hide the text

author: miguelvp
author_rank: Super Contributor
timestamp: March 12, 2015, 05:52:02 am
content: Your chan 1 input signal path is longer than the chan 2, so the differential signal input is going to be affected somewhat by that.Edit: I forgot to say it. Some kind of differential signal probe with it's own supply for the output signal.But not sure what the usb connector in there is for.

author: miguelvp
author_rank: Super Contributor
timestamp: March 12, 2015, 06:04:56 am
content: Also it seems U18 ad U12 are alternatives so only one is populated. with the small number of pins it can't be an FPGA, and they can handle USB so they have to be some MCU and the alternate is in case you don't find your preferred chip.

author: Liv
author_rank: Regular Contributor
timestamp: March 12, 2015, 08:02:50 am
content: AD9958 DDS? Clocked by conventional quartz resonator - frequency stability not required?.Differential to single-ended conversion done using OpAmps, no any input filtering?Note differential amplifier has unequal input impedances for its inputs.

author: Stonent
author_rank: Super Contributor
timestamp: March 12, 2015, 08:06:25 am
content: So nobody is speculating why it says ATTEN on it?

author: miguelvp
author_rank: Super Contributor
timestamp: March 12, 2015, 08:15:10 am
content: Attenuator for the output of the differential signal?

author: Liv
author_rank: Regular Contributor
timestamp: March 12, 2015, 08:44:22 am
content: ATTEN – attenuator enable (U8).7-pole elliptic filterU6 – amplifier with FB at pin 1 – AD8099?U7 – power OpAmp (THS3091 like?)R46-R51 - impedance matchingU11 – AD8307? Output connected to the MCU ADC input.LPF at detector’s input (after DDS and input signals mixing?)Q11 input signal emitter followerU9, U10 – switches to select input channel?Input protection DZ1..DZ7.

author: c4757p
author_rank: Super Contributor
timestamp: March 13, 2015, 01:31:49 pm
content: Okay, some of you werereallyclose.It's a gain/phase analyzer, meant for sweeping filters, amplifiers, control systems, etc. 1 kHz to 150 MHz. (200 MHz at a stretch). This is my BSEE capstone project, with a team of three other students. PCB design is mine.Generates a test signal using the AD9958 (good job guessing that). This can be attenuated by 15 dB by a switchable attenuator (control signal for this is the ATTEN test point) for sensitive or high-gain systems. This is fed into the DUT.Single-input mode of operation takes one of the two inputs, through a buffer, into a log detector. This is a very sensitive device - it's what is under the shield, as during prototyping, I was able to get over 90dB dynamic range when shielded from interference.Phase is measured by summing the input with a second signal locked to the first with variable phase offset. Phase is swept, finding the amplitude null. This is the reason for the buffer: keeps this phase reference signal from feeding back out the inputs.Dual-input mode samples at both the input and output of the DUT using the two inputs, which are switched. Input and output phase and amplitude are compared to compensate for the response of the analyzer itself.Plan is for this to be an open-source hardware device, with full documentation, targeted at use by students or hobbyists. We may look into selling either devices or kits.Dual microcontroller is due to the original selection of, in my opinion, a large, overkill microcontroller that unnecessarily raises the BOM cost and software complexity. It's rather late in the project to swap the chip in the current revision, but this opens the possibility of switching to a smaller one later without respinning the PCB.Target for full completion is late May.More renders and schematics.

author: krivx
author_rank: Frequent Contributor
timestamp: March 13, 2015, 03:32:35 pm
content: Very nice. Is the low frequency performance (1kHz) limited by the AD9958? I would definitely use this for audio if the frequency stability didn't go to crap...

author: c4757p
author_rank: Super Contributor
timestamp: March 13, 2015, 03:49:34 pm
content: Not visibly within our requirements. It appears to work quite well over its entire range. Its low frequency ability is a big part of why we selected it for this application.Catch is that it isveryparticular about how you take the outputs if you don't want the harmonic distortion to shoot through the roof. Meant to be transformer-coupled, naturally... Of course, you're welcome to steal my work

author: HackedFridgeMagnet
author_rank: Super Contributor
timestamp: March 14, 2015, 12:06:46 am
content: So to what extent are you carrying the team?

author: c4757p
author_rank: Super Contributor
timestamp: March 14, 2015, 12:14:32 am
content: Not as much as you'd think. The others working on it are computer engineering students, and they're working mostly on the embedded and PC side of things. I've definitely got a bit more work than they do, but they still have the usual full load.

author: marshallh
author_rank: Unknown
timestamp: March 14, 2015, 12:44:47 am
content: ( ?° ?? ?°)Sometime I will pick up "the project"... by then there should be new parts that make it easier.

author: c4757p
author_rank: Super Contributor
timestamp: March 26, 2015, 12:02:02 pm
content: Woohoo!

author: senso
author_rank: Frequent Contributor
timestamp: April 16, 2015, 11:27:35 pm
content: That silkscreen

author: c4757p
author_rank: Super Contributor
timestamp: April 16, 2015, 11:46:34 pm
content: Quote from: senso on April 16, 2015, 11:27:35 pm