Digital Signal Processing

Digital Signal Processors (DSPs) are used to process continuous data streams at high speed and under stringent real-time conditions. Typical measured parameters are sound, light, mechanical vibrations and electromagnetic fields. These are converted and digitized for processing, either by a DSP or a field programmable gate array (FPGA). Data processing is usually done by filtering, spectral analysis, correlation, compression, but may also be done using control and servo loops.

D.Modules are as a result of their architecture and interfaces perfecly suited for these tasks. The product concept supports any combination of data capturing, FPGA-preprocessing and DSP-analysis by combining modules, as well as the easy integration of DSP and/or FPGA-modules with existing data capture modules.

Measurement Technology

Particle Detector

An ultra-fast A/D converter on a FMC mezzanine card digitizes the output of an ionization- or semiconductor-based detector. The high-speed data stream is preprocessed in an FPGA and passed to a DSP for final analysis. Via a network interface the signal processing parametrization takes place as well as the DSP data output.

Railroad/Railway (brit. englisch) Track Optical Inspection

Optical mirrors and photodetectors are used to gather information about the track surfaces using DSP triangulation calculations. This system is mounted directly on the wheelset of the track recording vehicle. It is capable of measuring the amount of wear and detect anomalies like rail corrugations at high speeds.

Vibration Analysis

A DSP board and a D/A converter generate the shaker excitation, e.g. sinusoidal or noise. IEPE sensors are used to measure the generated vibrations, which are digitized by high-resolution A/D converters. The DSP uses this data for servo-control of the shaker excitation and passes the measured vibration data to a PC via an Ethernet network connection.


Dimensional Measurements and Material Characterization

This non-destructive measurement uses ultrasound in a frequency range up to 4 MHz. The transducer generates high energy pulses which travel through the material and are reflected by discontinuities and surfaces. A fast A/D converter measures the echoes and the DSP processes the delay time and signal strength. By comparison with a reference, material thickness and flaws can be detected.

Weld Inspection

The same technique as described above can be used to detect flaws like cracks and blow holes in welded joints, for example in pipelines.

Eddy Current

Metal Detection in Food Manufacturing Industry

Metal particles caused by wear and splintering in food manufacturing machinery can be detected using a balanced coil arrangement. A transmitter coil generates a high-frequency electromagnetic field. Metal particles passing through this field will cause a phase displacement in the two receiver coils, which is processed by a DSP system and induces the rejection of contaminated products. The signal processing algorithms must be adaptive to compensate for phase displacements caused by the product itself, e.g. by the packaging.


Railroad Crossing Monitoring

A radar scanner is activated prior to each train transit and generates a picture of the area between the gates. The baseband signal is digitized with a high-speed A/D converter and a DSP system compares the data with a reference picture to detect any obstacles, humans or vehicles, in the critical area. In contrast to camera systems, radar processing will reliably detect obstacles even in bad light conditions.

Driver Assistance and Autonomous Vehicles

Radar echoes, typically in the 24 or 77 GHz band, are used to measure the clearance zone in front of a vehicle. By taking into account the current velocity, a warning is generated, the speed is automatically reduced, or even an emergency stop is induced.
This technology is also used in lane changing and parling assistants. D.Module DSP boards are used for algorithm development in test vehicles.


Pipeline Leak Detection

The Multi-point Acoustic Sensing (MAS) technique uses hydrophones (underwater microphones), mounted at fixed distances along an underwater pipeline.
Leaks and damages will cause pressure fluctuations, which will propagate as acoustic waves through the surrounding medium. Analysis and interpretation is quite complex, since multiple parameters like pipeline material and geometry, temperature etc., modify the sound waves. A DSP system provides adequate processing power and bandwidth.

Barrier-free Traffic Lights

The audio signals generated by a barrier-free traffic light must adapt to the surrounding noise level. To determine this noise level, it is registered by a microphone, digitized, and aurally corrected by a DSP system.

Image Processing

Matrix Barcodes

DataMatrix Codes, like QR-Codes, are used in logistics to identify and track products during the manufacturing process. A CMOS camera is used to read the barcode, illuminated by a LED flash. The DSP system corrects optical distortions, normalizes and decodes the barcode. A network interface transmits the data to the inventory management and production control system. A HTTP server running on the DSP system provides configuration and adaptation.

Printing Quality Control

Cost-efficient CMOS image sensors can be used for various applications, and allow a direct connection to a DSP system. The DSP corrects image distortions caused by the optical system and the sensor. The quality parameters of the print products are evaluated by inspection of the print control strips. The results are used for quality control and automated process calibration.

Control Loops

Laser-Marking and Calibration

Laser technology enables extremely fast product marking and electronic devices calibration, for example LED brightness calibration for car vehicle lights. The laser is controlled by a DSP system with stringent real-time requirements, since delays or jitter will inevitably cause failures and inconsistencies. Matrix and vector calculus is used to control laser intensity deflectors.

Piezo Drive Controller

Piezo drives are used for high resolution positioning in 3D-lithography. Capacitive sensors and strain gauges are used for positional feedback. The servo control must be extremely fast and requires high resolution A/D converters. DSPs are capable of sustaining the high sampling rates, they apply linearization and corrections and control the piezo drive.


Software Defined Radio (SDR)

Data transmission techniques using frequency hopping or direct sequence spread spectrum modulation require digital signal processing at high sampling rates. Ideally the antenna and LNB is directly followed by an A/D converter operating at hundreds of MHz.
Off-the-shelf radio frontends are available as FMC mezzanine cards. An FPGA preprocesses the high-speed data stream and applies filters and downsampling. The final processing and demodulation is performed by a DSP.