advantages and disadvantages of pulse modulation

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From Wikipedia

Pulse-position modulation - Wikipedia, the free encyclopedia

The advantage of using PPM for this type of application is that the ...Pulse position modulation is also used for communication to the ISO/IEC 15693 ...


From Yahoo Answers

Question:PPM Pulse Position Modulation : "The amplitude and width of the pulse is kept constant in the system. The position of each pulse, in relation to the position of a recurrent reference pulse, is varied by each instantaneous sampled value of the modulating wave. PPM has the advantage of requiring constant transmitter power since the pulses are of constant amplitude and duration. It is widely used but has the big disadvantage that it needs a synchronization between transmitter and receiver." 1) what does it mean by "The position of each pulse, in relation to the position of a recurrent reference pulse, is varied by each instantaneous sampled value of the modulating wave?" 2) What does it mean by synchronization i.e "the big disadvantage of PPM that it needs a synchronization between transmitter and receiver" ? thanks

Answers:The transmitter puts out a stream of pulses called sync pulses which the receiver recognizes, in a special circuit called a phase locked loop(PLL). In the PLL it has an oscillator that generates pulses at about the same frequency as the transmitter (The frequency of the sync pulses is known ahead of time by standards.) a circuit called a phase detector decides whether the local generator is putting out its synch pulses at the the right frequency, it adjusts the oscillator to make it right. then it makes sure that the phase of the local pulses is adjusted so that the local sync pulse arrive exactly at the same time as the transmitted ones. This is known as being in synch. . in between each of the synch pulses, the transmitter will generate a data pulse,.These pulses do not confuse the PLL because they do not have exactly the same time between them. The receiver will will clear and start a counter when it receives a synch pulse and read it when it receives the data pulse. the value in the counter is passed through the receiver as the received data. Therefore the delay between the sync and data pulse conveys the value of the data to be transmitted. Clearly, I have oversimplified things a bit. periodically, systems have some housekeeping data they add to the data streams that make the data link more robust. and things like parity and error detection and error correction codes are sometimes sent with the data.

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Answers:cleaner transmission, less distance

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Answers:It's more resistant to noise than AM. It requires less bandwidth than FM. It's harder to encode/decode than both.

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Answers:From and audiophile's point of view, less distortion and a richer sound. From a radio tech's point of view, less atmospheric interference and lower incidence of bleed-over onto adjacent frequencies.

From Youtube

Omron MEMS Flow Sensor Product Training Module :This product training module offers a succinct, but tremendously informative presentation of Omron's MEMS flow sensor line-up, as well as their superior MEMS technology. - video developed and released by Omron Electronic Components LLC, Americas "The main feature of the MEMS Flow Sensor is its ability to measure flow speed from 1 mm to 40 m/s, which covers the range from the fluttering of a butterfly's wings to the roar of a typhoon. At the heart of the MEMS Flow Sensor, there is a tiny sensor element. That is the MEMS Flow Sensor chip which is only 1.5 mm square. Conventional flow sensors use a resistance measurement method based on a natural characteristic that causes the electrical resistance of a material to change due to changes in temperature. This method has a number of disadvantages, though, such as the high cost required for the extremely time-consuming adjustment of the resistance balance. (See Figure 1.) In contrast, the MEMS Flow Sensor was the industry's first to apply the thermopile method, which uses an element called a thermopile that converts thermal energy into electrical energy. This new method offered a variety of previously nonexistent advantages, including low-cost operation because there are few adjustments required, low power consumption, and high sensitivity." - comments by: Sasaki, Omron MEMS Flow Sensor chip Developer

H-Bridge Microchip PIC Microcontroller PWM Motor Controller :One of the advantages using the Microchip PIC microcontroller Pulse Width Modulation or PWM for short is; this PWM peripheral circuit is designed to control the DC motor using the full bridge mode PWM feature. The PWM peripheral works by supplying the correct signal to the H-Bridge DC motor circuit such as speed controlling and changing the DC motor direction. For more information please visit www.ermicro.com