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AP3302 Pt3 Contents

AP3302 Pt3 Section 2Contents

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AP 3302 Pt. 3

Section 2


Square Waves

Amplitude and Polarity of Square Waves

The square wave of Fig 2b starts from zero and rises to +1.5V. Its amplitude is therefore 1.5V. To describe its polarity we say that it is positive-going with respect to earth.

Somewhat similar results would be obtained if the battery were reversed so that its positive terminal was earthed, but in this case the voltage applied to the bulb would be - 1.5V with respect to earth. The square wave of voltage produced by switching on and off would then be as shown in Fig 3. The voltage starts from zero and falls to -1.5V. The amplitude of the waveform is again 1.5V but its polarity is now negative-going with respect to earth.

The square waves we use in radar do not always start from zero but may vary between any two fixed voltage levels. Some examples are shown in Fig 4. In each case the amplitude of the


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