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Introduction to Interfacing
Published in Francis Rumsey, John Watkinson, Digital Interface Handbook, 2013
Francis Rumsey, John Watkinson
Pulse amplitude modulation (PAM) is a means of modulating an analog signal onto a series of pulses, such that the amplitude of the pulses varies according to the instantaneous amplitude of the analog signal (see Figure 1.3) and this is the basis of pulse code modulation (PCM) whereby the amplitude of PAM pulses is quantized, resulting in a binary signal that is exceptionally immune to noise and interference since it only has two states. This process normally takes place in the analog-to-digital (A/D) convertor of an audio or video system, described in more detail in Chapter 2. PCM is the basis of all current digital audio and video interfaces, and, as shown in Figure 1.4, the effects of unwanted noise and timing instability may be rejected by reclocking the binary signal and comparing it with a fixed threshold. Provided that the receiving device is able to distinguish between the two states, one and zero, and can determine the timing slot in which each binary digit (bit) resides, the system may be shown to be able to reject any adverse effects of the link. Over long links a digital signal may be reconstructed regularly, in order to prevent it from becoming impossibly distorted and difficult to decode. Of course there will be cases in which an interfering signal will cause a sufficiently large effect on the digital signal to prevent it from being correctly reconstructed, but below the threshold at which this happens there will be no effect at all.
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Published in Mário Marques da Silva, Cable and Wireless Networks, 2018
Other analog source encoding techniques exist, such as the pulse position modulation or the pulse duration modulation. While in the PAM, each sample presents the amplitude of the sampled analog signal, the pulse position modulation samples present constant amplitude, but the amplitude of the analog signal is encoded by varying the position of the pulse position modulation sample. In the case of the pulse duration modulation, the amplitude of the sample is also kept fixed, while the width of the pulse is used as a variable to encode the amplitude of the analog signal.
Visible Light Communication for Advanced Wireless 5G Light-Fidelity Networks
Published in Ashish Bagwari, Geetam Singh Tomar, Jyotshana Bagwari, Advanced Wireless Sensing Techniques for 5G Networks, 2018
G. Nagarajan, P. Magesh Kannan
Pulse Amplitude Modulation is one of the important modulation schemes employed in signal transmission. PAM has a very simple method of modulation in which analog to digital conversion has been performed and the information is encoded into the amplitude of the series of pulses. Pulse amplitude modulation is a method in which the amplitude of each pulse depends on the instantaneous value of the modulating signal. This technique transmits the data by encoding in the amplitude of a series of signal pulses.
Adaptive timing correction technique for pulse-amplitude and pulse-position modulation interface
Published in International Journal of Electronics, 2019
Waleed Madany, Mostafa Rashdan, El-Sayed Hasaneen
This paper proposes a timing correction approach for the PAM-PPM link. This approach minimizes the timing error mentioned above without restricting the number of the AM bits. The PAM-PPM serial data link is shown in Figure 3 where the total number of the transmitted bits is (M + N). A detection circuit is needed at the receiver side in order to detect and amplify the received data signal and clock signal. A PAM demodulator circuit is used to recover the transmitted AM bits from the received data signal. An adaptive comparator circuit that depends on the recovered AM bits is used to eliminate the timing error associated with the received data signal. The TDC circuit uses the received clock signal as a reference clock signal to retrieve the PPM code from the received data signal.
SVPWAM modulation strategy for back-to-back converters to reduce harmonic and common mode voltage
Published in International Journal of Electronics, 2023
Fazel Tavassoli, Jafar Adabi, Hoda Ghoreishy, Mohamad Rezanejad
In this case, the ability to change the pulse amplitude is added to the inverter like changing the pulse width, the quality of conventional PWM control methods will be further improved (Ghoreishy et al., 2010; Sharifzadeh et al., 2018). The proposed carrier-based control method, which combines two modulations of pulse width and amplitude, is investigated for two-level inverters used in medium voltage drives. In this way, the quality of the conventional control method will be further improved. However, the realisation of the pulse amplitude modulation (PAM) requires replacing the DC sources in the inverter with adjustable DC sources. Due to the variability of intermediate DC sources in the system, the design of converter parameters would be a challenge. Therefore, the control circuit of the inverter must be designed in such a way that it responds to the dynamic speed of a variable DC link voltage. In other words, the various DC link amplitudes have different effects in the whole range of the amplitude modulation index. For this purpose, a solution to select the optimal values from all the obtained values will be proposed. Moreover, thanks to utilisation of the proposed SVPWAM method, the CM voltage would be reduced. Hence, its destructive effects (shaft voltage, bearing current and electromagnetic interference) are expected to be reduced and controlled, compared to the conventional methods. Also, the motor torque ripple is reduced and a significant improvement in THD of output voltage and current is achieved, which leads to a decrease in THD and an improvement in the size of the output filter, without increasing the switching frequency (Ghoreishy et al., 2012). As shown in this figure, the PAM technique is accomplished by stabilising the amplitude modulation index at specific values and instead changing the DC link voltage. Thus,
UER of various modulation schemes over SC diversity with GGD noise for EMNC
Published in International Journal of Electronics, 2023
S Pratap Singh, Akanksha Gupta, Rajneesh Kumar Singh, Ankush Kansal, Vineet Kansal
Pulse amplitude modulation (PAM) is a type of analogue modulation scheme in which modulating signals vary according to the variation in the amplitude of the carrier pulse train, whereas multi-level PAM (M-PAM) is the generalisation of PAM.