![]() The PWM pulse begins with the leading edge of the ramp signal and the width of the pulse is determined by the comparator circuit. The level of the comparator is so adjusted to have the intersection of the reference with the slope of the waveform. These two signals are added and compared with the reference voltage of the comparator circuit. This pulse amplitude modulated signal is fed to the non-inverting terminal of the comparator.Ī ramp signal generated by the sawtooth generator is fed to the inverting terminal of the comparator. The message signal and the carrier waveform is fed to a modulator which generates PAM signal. It is commonly known as an indirect method of PWM generation. The figure below shows the process of pulse width modulation. Generation of PWM signal Waveform representation Hence the immunity to the noise of a PWM system is better than the PAM system. ![]() Thus the noise factor does not cause much signal distortion. But that is totally easy removable at the receiver by making use of limiter circuit.Īs the width of the pulses contains information. However, during transmission channel noise introduces some variation in amplitude as it is additive in nature. Due to constant amplitude property, it gets less affected by noise. Thus, during signal transmission, the signal undergoes pulse width modulation. ![]() As the information component is present in width of the pulses. The duration of radio pulses ranges from fractions of a second to a nanosecond.In pulse duration modulation (PDM), the amplitude of the pulse is kept constant and only the variation in width is noticed. Radio pulses are used mainly in radio engineering and communications technology. The duration and amplitude of radio pulses correspond to the parameters of modulating video pulses the carrier frequency is an additional parameter. The duration and amplitude of such pulses depend on the parameters of the modulating oscillations. Radio pulses are intermittent, high-frequency or ultrahigh-frequency oscillations of electric current or voltage (Figure 1, e). Video pulses are used in television, computer technology, radar, experimental physics, and automation. The duration of video pulses ranges from fractions of a second to tenths of a nanosecond (10 −9 sec). A periodic sequence of video pulses is characterized by the repetition frequency and the off-on time ratio (the ratio of the repetition period to the duration of the electric pulse). Characteristic elements that determine the shape and quantitative parameters of a video pulse (Figure 2) are the amplitude A, front τ f, duration τ p, fall-off τ fo, and the slope of the pulse top (Δ A), usually expressed in percent of A. Video pulses may be square, sawtooth, trapezoidal, exponential, or bell-shaped (Figure 1, a-d). Current surges of large magnitude can have a shape analogous to that of high-voltage pulses.Įlectric current or voltage pulses (predominantly of the same polarity) are called video pulses if they have a nonzero direct component. Single pulses of similar shape are used to test high-voltage electrical equipment and installations they have an amplitude of several kilo-volts to several mega volts, a wave front of 0.5–2 microsec, and a duration of 10 to 10 −2 microsec. ![]() Lightning discharges are usually of the same shape. High-voltage pulses are usually observed during the discharge of a capacitor into an active load they have an aperiodic shape. Electric pulses may be classified as high-voltage pulses, pulses of high current intensity, video pulses, and radio pulses. Short duration is defined as a time interval comparable to the duration of transient processes in electric circuits. A change of short duration in voltage or in current intensity. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |