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UWB SIGNAL GENERATION

Ultra-Wideband (UWB) Signal Generation Fast pulses and impulses make excellent UWB signal sources for characterizing antennae and other components of UWB systems (e.g. RADAR, communications, etc.). This application topic discusses using pulse generators for the generation of UWB signals and how they propagate within a system.

For this UWB signal generation discussion, pulse shapes have been classified into four categories:
1. Rectangular
2. Step
3. Impulse
4. Monocycle

Often there may be more than one way to create a particular waveform. The choice will depend upon the amplitude, risetime, pulse duration, and degree of computer control needed.

Rectangular pulses have equal or nearly equal rise and falltimes. Rectangular pulses are produced by PSPL generator models 10,050A, 10,060A, 10,070A, 10,300B, and 2600C. These products are very flexible and have adjustable amplitude and pulse duration. A computer with GPIB interface can control the 10,000A series models.

10,000 Series Programmable Pulse Generator
10,000 Series Programmable Pulse Generator

PSPL manufactures three pulse generators that directly produce impulse outputs: the models 1000D, 3500D, and 3600. Adding Impulse Forming Network (IFN) components to Rectangular Generators or Step Generators can also create impulses. Impulses are useful for simulating digital signals, impulse response testing, radar applications, and for measurements requiring a flat frequency spectrum such as EMI tests.

Adding an Impulse Forming Network (IFN) to an impulse source creates a monocycle. A monocycle has a narrower frequency spectrum than the other waveforms discussed here and has no DC component. It is often used with bandwidth-limited antennas.

Step generators are also often used as UWB sources. They have fast leading edges and long flat toplines. Generally, the durations are fixed. Models 4015C, 4015D, and 4016 produce negative steps with the fastest electrical edges that are commercially available. The very slow trailing edge makes them ideal for use with IFNs to produce impulses.

PSPL generator models 4020-TDT, 4022-TDT, 4050B, and 4500E produce large amplitude positive steps that are useful for some UWB applications. The shape of a pulse determines its spectral energy. The graphs presented in PSPL Application Note AN-9 show the time domain waveforms and frequency spectra for several PSPL pulse generators with added IFN’s.




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AN-14a : UWB Signal Sources...