Frequency Sweep

A swept sine wave, a wave that changes in frequency over a period of time is used to measure the frequency characteristics of an electronic device . The frequency change occurs linearly. It is either in Hz per seconds or logarithmically in Octaves per second. Advanced sweep generators support sweep sequences with selectable start frequency, hold frequency, stop frequency and associated times. A trigger signal is synchronously provided by the signal generator to the sweep for controlling an oscilloscope which measures the output response of the device.

Signal Generator Types

Signal Generators are broadly divided into the following:

• Analog and Mixed Signal Generators
  
  • Arbitrary Generators
    
    • Arbitrary/Function Generator (AFG)
    • Arbitrary Waveform Generator (AWG)

•  Logic Signal Sources (Pulse or pattern generators)

 Each of these types has unique strengths that may make it more or less suitable for specific applications. The arbitrary/function generator (AFG) offers fewer waveform variations than its AWG equivalent, but with excellent stability and fast response to frequency changes. Arbitrary generators answer almost any kind of signal generation needs. In the past, AFGs created their output signals using analog oscillators and signal conditioning. Now they use Direct Digital Synthesis (DDS) techniques to determine the rate at which samples are clocked out of their memory. The typical AFG has several standard waveforms stored in a preprogrammed part of its memory. In general, sine and square waves are the most widely used for many test applications.

Most AFGs offer some subset of the following familiar wave shapes:

• Sine
• Square
• Triangle
• Sweep
• Pulse
• Ramp
• Modulation
• Haversine

The arbitrary waveform generator (AWG) can produce any waveform you can imagine. Whether it is an RF signal to test a GSM or CDMA based telephone handset or a data stream for disk drive characterization. An arbitrary waveform generator (AWG) delivers waveforms based on stored digital data describing the constantly changing voltage levels of an AC signal. though the curve makes their spacing appear to vary. In an AWG, the sampled values are stored in binary form in a fast Random Access Memory (RAM). Some AWGs include separate digital outputs. These outputs fall into two categories: marker outputs and parallel data outputs.