Archive for Equipment Review

Teardown, Repair and Experiments of an Agilent 86120B Multi-Wavelength Meter


In this episode Shahriar repairs an Agilent 86120B Multi-Wavelength Meter. The instrument reports “E14 Data Acquisition Problem” which corresponds to a potential internal HeNe reference laser failure. After the instrument disassembly, the old HeNe laser is removed and its optical power is compared to that of a new laser. The measurements confirm that the old laser has significantly deteriorated in output light intensity. The new laser is fitted inside the unit and the error message is eliminated. The free-space optic portion of the instrument is revealed and the principle operation is reviewed. Various components of the Michelson Interferometer is examined.

To test the correct operation of the instrument, a single tone semiconductor laser is applied to the unit and the result is compared to a different wavelength meter. The concept behind the operation of a Fabry-Perot laser is also presented before the signal is applied to the wavelength meter.


Tektronix MDO4104B-6 Mixed Domain Oscilloscope (MDO4000B) Review and Experiments


In this episode Shahriar reviews and demos the second revision of the industry’s first Mixed Domain Oscilloscope from Tektronix. The MDO4000B series offers improved signal integrity and performance. The reviewed model is a MDO4104B-6 which offers 16-Channel Logic Analyzer, 4-Channel Oscilloscope with 1GHz of analog bandwidth as well a 6GHz Spectrum Analyzer with greater than 1GHz of instantaneous capture bandwidth with 65dB of dynamic range.

After an overview of the instrument’s interfaces and built quality, the block diagram and principle operation of the instrument is explained. The time-correlated digital, analog and RF capturing capability is described and its advantages for debugging complex mixed-domain systems is explored. Instrument probes, accessories and various modules are also presented.

The instrument is used to measure an ultra-pure single-tone signal at various frequencies for THD, SFDR and dynamic range measurements. For the main demonstration, a complete I/Q modulator system prototype is presented. The prototype includes a Maxim MAX2721 modulator, external PA, antenna diversity switch SW-277, digital control circuitry, power-grid DC-DC converters, external step attenuators, an Agilent E4342B synthesizer for LO generation and an Agilent N6020A arbitrary waveform generator for baseband signal generation. The Tektronix MDO is used to monitor RF, baseband, digital and power-supply analog waveforms. The system includes an array of problems including intermittent spurious tones, power supply dependent spectral noise, antenna switching glitches and 256-QAM constellation imperfections. The MDO is used to analyze, measure and solve all system problems. Tektronix SignalVu is used to analyze the system performance. As a final experiment, the MDO is used to demodulate a 1GHz bandwidth 32-QAM 500MS/s signal centered at a 3GHz carrier. The experiment documents can be downloaded here.


Experiments and Demo of an Agilent DSA-X 96204Q 160GS/s 62GHz Oscilloscope


In this episode Shahriar demos the world’s fastest oscilloscope! The Agilent DSA-X 96204Q offers 160GS/s of conversion rate  with a bandwidth of 62GHz on two dedicated ‘RealEdge’ channels. It can also provide 80GS/s conversion rate and 33GHz of bandwidth on four simultaneous channels. The unit demoed in this video is equipped with all available options and is valued at over 0.5 million US dollars. The block diagram of various sub-systems of the oscilloscope are presented and the principle operation of the instrument is explained. A 56Gb/s PRBS-15 signal is applied to the scope from a Centellax 2G2P5A (now Agilent N4975A) and the resulting data pattern is examined in real-time. Various scope functions are also presented as well as the capability to observer bit failures at baud-rate using this instrument.

As a second experiment, two 3.125Gb/s PRBS-7 data streams are simultaneously up-convered to 20GHz and 40GHz respectively by using a pair of MITEQ mm-wave DSB tripple balanced mixers and a pair of Avantek 20-40GHz YIG oscillators. The resulting two signals are combined by using a power-combiner and fed to the oscilloscope. The capability of the instrument to act as an ultra-broadband software-defined radio is demonstrated by recovering the two PRBS sequences simultaneously through DSP post processing. The block diagram of this setup can be downloaded from here.

I’d like to thank Mr. Neil Hoffman from Agilent for enabling this demo and Dr. Jeffery Lee for his help with the experiments.


Experiments and Teardown of an Agilent 11896A Polarization Controller


In this episode Shahriar demonstrates the functionality and applications of an Agilent 11896A Polarization Controller. Various fiber optic communication methods are presented. This includes the use of complex modulation schemes (such as PAM and QAM for coherent receivers), polarization division multiplexing (PDM), wavelength division multiplexing (WDM), and spatial division multiplexing (SDM). The concept of light polarization is demonstrated by using a pair lenses from a consumer theater 3D glasses and two blue LEDs with uncorrelated lighting patterns.

In order to test the polarization controller, a solid-state laser source, SMF fiber with APC/PC connectors as well as a polarization beam splitter is presented. By using a pair of optical power sensors, the functionality of the polarization controller is verified. Finally, the teardown of the unit is presented and the method to achieve polarization control is observed. 

The fiber optic communication overview document can be downloaded here. I’d also like to acknowledge my colleague and friend Dr. Timo Pfau for his expertise and consult on fiber optic communication methods.


Tutorial on the Theory, Design and Characterization of Nyquist Digital to Analog Converters


In this episode, Shahriar presents the theory, design and characterization of Nyquist Digital to Analog Converters (DACs). After a brief overview of DAC operation and theory, the schematic of an 8-Bit R-2R DAC is presented. The R-2R DAC, which is driven by a dsPIC30F6014A Microchip microcontroller  is capable of producing ramps and arbitrary waveforms uploaded through an RS232 interface. The static integral non-linearity (INL) and differential non-linearity (DNL) is measured by using a Rigol DM3068 Multimeter through a Matlab interface program. The dynamic performance of the DAC is characterized using an Analog Devices AD6645 105MSps 14-Bit ADC evaluation board coupled with a USB FIFO interface board. By using the ‘Visual Analog’ software, the spectrum of the DAC output as well as the signal to quantization and distortion ratio (SQNDR) is calculated. Finally, the impact of component mismatches, operational amplifier non-linearity and timing uncertainty on the INL/DNL and SQNDR (ENOB) of the DAC is examined.