Principles of construction and structural and circuit designs of direct digital synthesizers based on the method of direct digital frequency and signal synthesis are described. The block and circuit diagrams of the direct digital synthesizer of compound wideband signals are presented. This synthesizer is used to synthe size signals with the amplitude, frequency, and phase modulation in a frequency range from 0.001 to 200 MHz.

We discuss the potential of ultra-wideband (UWB) technology for realizing use cases in industry 4.0 and demonstrate the implementation of an UWB sensor network with off-the-shelf transceivers for machine vibration monitoring. We propose a flexible medium access layer tailored for industrial sensing and show how the choice of its parameters is affected by the propagation environment and hardware constraints. Our real-world experiments reveal that links up to 20 meters can be achieved in industrial environments with an average packet loss rate in the order of 10 −6 for typical links. A comparison with a commercial vibration monitoring system based on IEEE 802.15.4 spread spectrum shows that UWB attains a twenty-times higher throughput for similar link ranges. INDEX TERMS Wireless sensor network, industry 4.0, ultra-wideband, condition monitoring. 1 Not in our focus are applications in which only status data is transmitted or in which the acquired data changes only slowly (e.g., temperature monitoring); these are covered by low-power low-rate technologies, like LoRa and Sigfox [11].

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