In this episode Shahriar uses a few components to beyond what there were originally intended for in order to setup an optical link! By using a BlinkM RGB LED, a Color Sensor, and two PIC USB Boards from Sparkfun Electronics, a stand-alone optical link is established. Various theories of operation, including multilevel data transmission, signal constellation and detailed circuit diagrams are also presented. The final result is an 8-PAM, 3-Wavelength optical link with a colorful three-dimensional constellation graph. The code for the transmitter IC, receiver IC and Matlab functions are available to download from http://TheSignalPath.com

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In this episode Shahriar explores the world of filters! Starting from a simple lumped RC filter, he briefly covers the theory before moving onto measurement techniques. The bandwidth of the filter is verified experimentally in the time domain. A more complex RLC band-stop filter is also demonstrated with a tune-able inductor which is measured using an RLC meter. Using a Rigol spectrum analyzer with built in tracking generator and an active probe, the frequency response of the filter is measured. Several other packaged filters are also demonstrated and a microwave band-pass filter is disassembled to reveal its internal construction.

Moving onto "undesired filters", a Tyco backplane board is presented and the bandwidth limitation of the backplane traces are measured. A Xilinx FPGA board equipped with a Vertex II PRO is used to generate a 1.5Gbps PRBS data stream through the Tyco board. After observing the frequency composition of the date, pre-emphasis equalization is used to compensate the backplane frequency limitations. Eye diagram measurements verify the benefit of pre-emphasis equalization to combat inter-symbol-interference (ISI).

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In this episode Shahriar investigates the impact of linearity and distortion on analog circuits. The source of a non-linear input/output characteristic is presented in three different domains: mathematical, time domain and frequency domain. After the theoretical discussion, a sample circuit is built and tested to illustrate real time signal distortion. The criteria for measuring non-linearity is also presented. Furthermore, the importance of a two-tone test for bandwidth limited circuits is shown theoretically and experimentally. There is another quiz in this episode! Please discuss the answer on the forum or in the comment section.

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In this (experimental) episode Shahriar demonstrates two embedded-electronic circuits available for purchase from Sparkfun Electronics. The demos illustrate some of the capabilities of these circuits along with a short instruction on how to interface and operate them. All the code for the AHRS demo and the RGB Matrix demo are available to download on our website.

The first demo is of a 9-degree of freedom (9-DoF) sensor board equipped with three dimension of linear acceleration (accelerometer), angular acceleration (gyroscope) and magnetometer. Using the combined information from these sensors an Attitude and Heading Reference System (AHRS) data can be extracted. The demo shows this system in action using customized Matlab functions.

The second demo demonstrates the ease of use of an RGB LED Matrix equipped with an SPI interface. A sample C code written for a Microchip PIC18F2455 is used to draw some simple animations.

This is an experimental episode to judge the level of interest in these type of demo videos. Please leave feedback!

The Signal Path
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In this episode (Part 6/6) Shahriar reviews the brand new Rigol DP1116A and DP1308A programmable power supplies. Furthermore, the power supply features are compared against an Agilent dual output power supply.

"DP1308A & DP1116A are high-performance programmable linear DC power supply. They have excellent features including timed outputs and tracking capabilities; extremely clean ripple and noise, comprehensive over-voltage, over current, over-temperature protection, a large and clear user interface, super performance specifications,and multiple standard interfaces. The DP1308A & DP1116A meet the requirements of various forms desktop and integrated system testing. DP1308A & DP1116A are widely used in research and development, education, industrial control, mobile communication, and product testing, etc."

The MSRP for both products is $849. Rigol offers a 30 day no-questions-asked return policy and a 3 year warranty. They also provide an excellent local technical support out of tropical Cleveland, Ohio.