What is a raster generator?

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A sweep generator is an electronic test generator that creates a periodic sawtooth waveform intended to modify the output of a second signal generator, which is usually a radio frequency (RF) generator. The periodic sawtooth waveform rises to a peak level, then quickly drops to a low level and repeats the process. A sweep generator output can be used to control the frequency output of a signal generator to generate a sweep frequency output. In general, a sweep generator allows a test setup to almost simultaneously measure the response of devices within a frequency range or frequency range.

Sweep generators are used to test frequency response over a range of frequencies. Whenever RF circuits or electrical circuits have a specific frequency response, the sweep generators can generate the test signal that will cover the specific frequency range. The basic sine wave or sine wave is a voltage that changes periodically in time, which flows smoothly from zero to the positive peak, then to zero, then to the negative peak, and back to zero. A complete cycle will have two zero points and two peak points, which are positive and negative.

The frequency domain description is used when the device being tested must operate in a certain frequency range. The frequency range of a device can be evaluated by a sweep generator and a spectrum analyzer, the corresponding test equipment. It has a two-dimensional display that shows vertical power levels and a horizontal frequency readout. When monitoring a signal with the spectrum analyzer, the vertical axis is still amplitude, in watts (W), but the horizontal axis is frequency, in hertz (Hz) rather than units of time.

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In an amplifier with transistor circuits, inductors and capacitors, there is an expected gain or net amplification over a range of frequencies. For an RF power amplifier, the gain is observed by measuring the input to the amplifier. If the output is 1 W while the input is 0.01 W, there is a gain of 100. Given that the center frequency is actually 150 megahertz (MHz), a usual parameter next to the question is bandwidth, which is the frequency range below and above the center, where the gain is half the gain at the center frequency. This is also known as “–3dB” points, where –3dB refers to half the power gain.

If the lower –3dB point is 148 MHz and the upper –3dB point is 152 MHz, the power amplifier is referred to as having a frequency range of 148–152 MHz. The sweep generator can then be configured so that its lowest frequency is 148 MHz. The high level of the sweep generator causes 152 MHz in the signal generator output. If the sawtooth generator inside the sweep generator is turned off, the signal generator output will stop sweeping the 148-152 MHz range. Without the sweep generator, the signal generator will output at the fixed frequency of about 150 MHz.

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