An introduction to why and when terminations are needed for transmission lines in both high speed digital applications and RF applications. 50 ohm termination examples are given, but the principles apply for other line impedances as well. The basic operating principles of signal propagation down a transmission line and the effects of reflections coming from improperly terminated are covered. Examples for digital-like signals as well as RF signals are given. A description and examples of what is meant by Standing Waves is also given. As a bonus, the properties of quarter wavelength transmission lines in RF applications is also presented.
Transmission Line Terminations for Digital and RF signals - [Link]
Convert square wave clock signals to low distortion sinewaves – [via]
This circuit derives a pure sinewave from a crystal-controlled clock source by using a ring counter to remove the highest-amplitude unwanted harmonics, and filtering the result with an 8th-order lowpass, switched-capacitor elliptic filter
Low-cost, low-distortion square to sinewave signal converter - [Link]
Dilshan developed a 8 channel USB digital signal generator and an open source Windows application called Kidgo Player to drive it. The hardware is basically just a PIC18F2550 USB breakout board used to provide 8 digital outputs for his software. The Kidgo Player’s source is available on GitHub, and has the following features – [via]
- Save waveforms and settings as binary file (KDF file) or export waveform as a text file
- Playback controls such as “Play to segment”, “Play from segment”, “Step back”, “Step next” and “Clear”
- Shifting and rotating waveforms
- Invert, Reset, Clocking and Binary Generator functions
- Copy and Paste waveforms
- Mute function to each individual channel
- Launch without any installation or configuration (design to work as portable Windows application)
Kidogo: 8 channel USB Digital Signal Injector - [Link]
It’s time for a lecture. I’ve been spending a lot of time creating a DIY dlectrocardiogram and it produces fairly noisy signals. I’ve spent some time and effort researching the best ways to clean-up these signals, and the results are incredibly useful! Therefore, I’ve decided to lightly document these results in a blog entry.
Here’s an example of my magic! I take a noisy recording and turn it into a beautiful trace. See the example figure with the blue traces. How is this possible? Well I’ll explain it for you. Mostly, it boils down to eliminating excess high-frequency sine waves which are in the original recording due to electromagnetic noise. A major source of noise can be from the alternating current passing through wires traveling through the walls of your house or building. My original ECG circuit was highly susceptible to this kind of interference, but my improved ECG circuit eliminates most of this noise. However, noise is still in the trace (see the figure to the left), and it needed to be removed.
Signal Filtering with Python - [Link]
There are many times where you would like to “stabilize” an input signal so that you don’t see the input value “jumping” so much. This is specially true on the MilliVolt Signal range, where nearby noise present can disturb the original signal. In this case, you always have the option of buying some kind of signal conditioner, which handles the filtering function of the raw signal. However, there are many times where the noise problem presents itself after the system is built, in which case a simple software solution is preferable to mitigate the problem.
Simple Software Filter - [Link]
When building AVR DDS2 signal generator there were lots of discussions about signal conditioning in analog part of device. First argument was that LM358 wasn’t the best choice for this purpose. Another one pointed to sine wave that weren’t smooth enough.
As you can see there are some dents on it. Other waveforms also are distorted especially when higher voltages are selected. This definitely asks for better analog part. Some people suggested to replace LM358 with OPA2134, but it seems to be quite expensive choice. In my opinion low noise general purpose op-amp can be great too. I’m gonna give a try to Texas Instruments TL074 low noise op-amp. It is low power, high slew rate (13V/us) IC – almost five times faster than LM358 and for same reasonable price.
Modeling of analog part for DDS3 signal generator - [Link]
IR protocol analyzer is a universal application for automatic decoding several types of infrared remote control protocol packets. The application uses microphone input of a soundcard to capture infrared signal from a remote control. As a consequence, the hardware receiver is minimalistic and easy to build; just plug a phototransistor to input of your soundcard, that’s all hardware you need.
Application processes IR signal from a remote control and compares it with its own database of known protocols. When a match is found, packet is decoded and its characteristic is displayed to user (including protocol name, description, decoded data and graph with timing).
IR protocol analyzer - [Link]
Saelig Company, Inc. announces availability of the Wave Standard series of advanced Arbitrary Function Generators from Tabor (Israel). Offering up to 350MHz in single and dual channels, WS8351 and WS8352, deliver fast, versatile, high-performance arbitrary waveform, function, and pulse generation.
Designed to fulfill the growing needs of todayʼs design and test engineers, these new models boast a 2GS/s clock with a 512k memory and up to 4Vpp output into 50 ohms. This allows the generation of a wide variety of complex waveforms at very high speeds. In addition to its function and arbitrary capabilities, these ultra-fast WS models can generate high-precision pulses with extensive pattern composition utilizing PulseComposerTM pulse/pattern composer application software. PulseComposerTM includes special modes such as: programmable transition times, multi-level patterns, arbitrary bit design and PAM(n), utilizing either NRZ or RZ modes with data rates reaching as high as 350MBit/s.
Saelig Announces Advanced 350MHz AFG Signal Generators - [Link]
Here a small project with an ATtiny45. Currently I was able to write some big characters in a VGA monitor. This is the first part, but the final result will be a bluetooth controlled scoreboard.
Scoreboard – VGA signal from an ATtiny45 - [Link]
Signal Wizard 3.0 is a very powerful audio signal processor that features multichannel synchronous processing. It can mix, amplify, filter, delay and adjust the phase of individual input signals, selected by using the included intuitive PC software. Signal Wizard 3.0 features a 24-bit, 96 kHz codec with six analog input and eight analog output channels, and an internal DSP processing speed of 0.6 GMACs. Signal Wizard 3.0 also incorporates two digital audio (S/PDIF) inputs and outputs. Like its two channel equivalent Signal Wizard 2.5, the software requires no knowledge of mathematics or programming.
Signal Wizard 3.0 includes very powerful mixer functions – any channel can be blended with any or all of the other channels in any proportion, since the system incorporates mixer units at the input and output signal stages. Signal Wizard 3.0ʼs unique filter design engine enables standard filter types to be created using the easy-to-use graphical software, but it also allows completely arbitrary frequency responses, both in amplitude and phase, to be realized via a simple text file import. Read the rest of this entry »
Here is my homemade function generator that can produce a square, triangle, and sign wave. This is all done with a few bucks worth of parts. The heart of the function generator is a LM324N quad OpAmp. I got the schematic off of a site where they were also selling kits to build the signal generator.
DIY Function (Signal) Generator – [Link]