Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.) Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.) Expired - Fee Related Application number US08/719,755 Inventor Yoshihiro Ohtani Current Assignee (The listed assignees may be inaccurate.
#PULSE POSITION MODULATION PPM PDF#
The following table presents the comparison between three modulation techniques.- Google Patents US5691665A - PPM demodulation deviceĭownload PDF Info Publication number US5691665A US5691665A US08/719,755 US71975596A US5691665A US 5691665 A US5691665 A US 5691665A US 71975596 A US71975596 A US 71975596A US 5691665 A US5691665 A US 5691665A Authority US United States Prior art keywords pulse symbol ppm signal level Prior art date Legal status (The legal status is an assumption and is not a legal conclusion. The synchronization between the transmitter and the receiver is a must.
AdvantageĪs the amplitude and the width are constant, the power handled is also constant. Hence, the position of these pulses is proportional to the width of the PWM pulses. Each trailing edge of the pulse width modulated signal becomes the starting point for pulses in PPM signal. Pulse position modulation is done in accordance with the pulse width modulated signal. The following figures explain the Pulse Position Modulation. These sync pulses help to maintain the position of the pulses. The transmitter has to send synchronizing pulses (or simply sync pulses) to keep the transmitter and the receiver in sync. Pulse Position Modulation (PPM) is an analog modulation scheme in which, the amplitude and the width of the pulses are kept constant, while the position of each pulse, with reference to the position of a reference pulse varies according to the instantaneous sampled value of the message signal. The waveform for this type of PWM is denoted as (c) shown in the above figure. The center of the pulse being constant, the leading edge and the trailing edge varies according to the message signal. The waveform for this type of PWM is denoted as (b) in the above figure. The trailing edge of the pulse being constant, the leading edge varies according to the message signal. The waveform for this type of PWM is denoted as (a) in the above figure. The leading edge of the pulse being constant, the trailing edge varies according to the message signal. The following figure explains the types of Pulse Width Modulations. These circuits clip off the amplitude to a desired level, and hence the noise is limited. Amplitude limiters are used to make the amplitude of the signal constant. The width of the pulse varies in this method, but the amplitude of the signal remains constant. In Pulse Width Modulation (PWM) or Pulse Duration Modulation (PDM) or Pulse Time Modulation (PTM) technique, the width or the duration or the time of the pulse carrier varies, which is proportional to the instantaneous amplitude of the message signal. This process simplifies the circuit design. The flat-top PAM signal is shown in the following figure.įlat-top sampling is the process in which, the sampled signal can be represented in pulses for which the amplitude of the signal cannot be changed with respect to the analog signal, to be sampled. Hence, to avoid this noise, use flat-top sampling. Though the PAM signal is passed through a LPF, it cannot recover the signal without distortion. The following figures explain the Pulse Amplitude Modulation. In natural PAM, a signal sampled at Nyquist rate can be reconstructed, by passing it through an efficient Low Pass Filter (LPF) with exact cutoff frequency. The pulse amplitude modulated signal will follow the amplitude of the original signal, as the signal traces out the path of the whole wave. In Pulse Amplitude Modulation (PAM) technique, the amplitude of the pulse carrier varies, which is proportional to the instantaneous amplitude of the message signal. In this chapter, let us discuss the following analog pulse modulation techniques. After continuous wave modulation, the next division is Pulse modulation.
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