Teardown & Analysis of an Agilent 86109B Optical/Electrical DCA-X Oscilloscope Module

In this episode Shahriar presents the inner workings of an Agilent 86109B optical/electrical DCA-X oscilloscope module. This particular model offers up to 50GHz of electrical bandwidth and an optical input capable of receiving up to 40Gb/s data rates. The differences between a real-time and sub-sampling oscilloscopes are presented with focus on ADC resolution, signal periodicity requirements and input bandwidth. The block diagram of the module as well as a sub-sampling oscilloscope is also presented.

The teardown of the module shows various components such as samplers, O/E conversion block, impulse generator as well as a step-recovery diode driver. I/O interfaces as well as various analog blocks are also shown. Several modules are further disassembled to observe the inner semiconductor designs under the microscope.


  1. James says:

    Hi Shahriar,

    I know this is an old episode, but if you still have the sampling module, it would be interesting to try to take a look under the microscope from the opposite side. The small rectangular die (visible at lower center in the image at 28:38 in the video) is almost certainly a soliton forming non-linear transmission line IC, with non-linearity provided by many Schottky diodes loading a coplanar strip transmission line. The output of this is a high amplitude pulse with much faster transitions than the SRD output, and the CPS line of the NLTL IC is transformed to slotline by the large tapered metal areas on the quartz(?) substrate. It looks like this version of sampler has a resistive tap from the end of the sampled signal CPW line, brought out by the long wirebond at the center of the image, and probably used to cancel low frequency feedthrough. A closeup of the coax to CPS balun at the bottom of that same image would also be interesting.

    Keep up the great videos.

  2. Bhavani sankar says:

    Dear Shahriar Shahramian,
    1.i have been following your videos and they are quite educational and very useful, i have a question ,currently i am testing a receiver chip (direct conversion receiver, baseband bandwidth is 0-2MHz)

    2.we have a noise source N4002A from keysight of range 10MHz to 26.5 GHz and my receiver IF is DC-2MHz can you suggest some method to measure noise figure @ 2MHz using the same noise source

    3.i am also using the above said noise source with MXA N9020A Spectrum Analyzer from keysight

    Thanks in Advance & Best Regards
    Bhavani Sankar Appalla
    Engineer Test & Measurement,
    Indian Institute of Science,

  3. حسین کرد شبستری says:

    I have a question about adc’s! could I achieve higher sample rate with using 4 of max1434 octal 50msps chip? like 1Gsps ?

  4. Jarek says:

    These short videos are great. Thanks.

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