Modulation and Demodulation - Revision history

Yash: /* Some Pros and Cons of General Modulation Schemes */

2018-02-19T20:08:28Z

‎Some Pros and Cons of General Modulation Schemes

Yash: /* Some Pros and Cons of General Modulation Schemes */

2018-02-19T20:04:54Z

‎Some Pros and Cons of General Modulation Schemes

Yash at 19:52, 6 February 2018

2018-02-06T19:52:17Z

Yash at 17:28, 1 February 2018

2018-02-01T17:28:39Z

Yash at 16:37, 1 February 2018

2018-02-01T16:37:56Z

Yash at 18:09, 22 January 2018

2018-01-22T18:09:56Z

10.101.202.237: Created page with "Modulation is very important step in the transmission of signal. Our message signal is generally a low frequency signal and path loss of signal is proportional to the square o..."

2018-01-22T18:03:49Z

Created page with "Modulation is very important step in the transmission of signal. Our message signal is generally a low frequency signal and path loss of signal is proportional to the square o..."

New page

Modulation is very important step in the transmission of signal. Our message signal is generally a low frequency signal and path loss of signal is proportional to the square of the wavelength (and hence inversely proportional to the square of the frequency). <br \>
So, we have to find a method to devise a way to encode our message signal to higher frequency signal. We can tinker with different properties of carrier signal like frequency, phase, amplitude to encode our message signal on carrier signal.

== Reasons for Modulation ==
* Modulation of signal is important to prevent mixing of message signals from different transmitters and makes it easier to tune to the desired signal.
* Without modulation, size of the antenna will become very large and it will make antenna size in order of km for message signal of kHz order.
* For reliable and effective communication over long distance i.e. minimizing the signal losses during transmission.
* As signal band is limited (from few MHz to maybe some GHz) we have to use as low bandwidth of signal as low as possible. (i.e. maximizing the use of bandwidth allocated) <br \><br \><br \>

If you are done reading this page, you can go back to [[Communications Subsystem]]

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 == Some Pros and Cons of General Modulation Schemes ==
 For digital communication in general:
-* ASK is very inefficient and susceptible to interference for wireless (but can be useful over fiber optics or copper).
+* [https://en.wikipedia.org/wiki/Amplitude-shift_keying Amplitude Shift Keying (ASK)] is very inefficient and susceptible to interference for wireless (but can be useful over fiber optics or copper).
-* FSK is less susceptible to errors and interference than ASK because interference is often confined to a specific frequency.
+* [https://en.wikipedia.org/wiki/Frequency-shift_keying Frequncy Shift Keying (FSK)] is less susceptible to errors and interference than ASK because interference is often confined to a specific frequency.
-* PSK is the least susceptible to error of these three. In terms of bit error rate (BER), binary PSK is about twice as good as ASK and FSK in the presence of noise, and the BER can be significantly improved through other techniques.
+* [https://en.wikipedia.org/wiki/Phase-shift_keying Phase Shift Keying (PSK)] is the least susceptible to error of these three. In terms of bit error rate (BER), binary PSK is about twice as good as ASK and FSK in the presence of noise, and the BER can be significantly improved through other techniques.
-*[https://en.wikipedia.org/wiki/Orthogonal_frequency-division_multiplexing Orthogonal frequency-division multipleing OFDM] can also be used. It is very spectrally efficient. <ref>https://space.stackexchange.com/questions/15428/what-is-the-advantage-of-qpsk-over-fsk-or-ask-for-satellite-data-transmission</ref>
+*[https://en.wikipedia.org/wiki/Orthogonal_frequency-division_multiplexing Orthogonal frequency-division multipleing (OFDM)] can also be used. It is very spectrally efficient. <ref>https://space.stackexchange.com/questions/15428/what-is-the-advantage-of-qpsk-over-fsk-or-ask-for-satellite-data-transmission</ref>
 For analog communication in general:
-* AM is efficient in terms of bandwidth and has simple receiver circuit but subjected to amplitude variations due to noise and interference
+* [https://en.wikipedia.org/wiki/Amplitude_modulation Amplitude Modulation (AM)] is efficient in terms of bandwidth and has simple receiver circuit but subjected to amplitude variations due to noise and interference
-* FM is less susceptible to interference and noises. But has complex circuits and requires large bandwidth.
+* [https://en.wikipedia.org/wiki/Frequency_modulation Frequency Modulation (FM)] is less susceptible to interference and noises. But has complex circuits and requires large bandwidth.
-* PM is not affected by channel noise but on the other hand it has complex circuit as compare to AM and FM.
+* [https://en.wikipedia.org/wiki/Phase_modulation Phase Modulation (PM)] is not affected by channel noise but on the other hand it has complex circuit as compare to AM and FM.
 For in-depth detail of various modulation schemes you can refer to [http://berk.tc/habsis/mod1.pdf this document].

@@ Line 20: / Line 20: @@
 * FSK is less susceptible to errors and interference than ASK because interference is often confined to a specific frequency.
 * PSK is the least susceptible to error of these three. In terms of bit error rate (BER), binary PSK is about twice as good as ASK and FSK in the presence of noise, and the BER can be significantly improved through other techniques.
-*OFDM can also be used. It is very spectrally efficient. <ref>https://space.stackexchange.com/questions/15428/what-is-the-advantage-of-qpsk-over-fsk-or-ask-for-satellite-data-transmission</ref>
+*[https://en.wikipedia.org/wiki/Orthogonal_frequency-division_multiplexing Orthogonal frequency-division multipleing OFDM] can also be used. It is very spectrally efficient. <ref>https://space.stackexchange.com/questions/15428/what-is-the-advantage-of-qpsk-over-fsk-or-ask-for-satellite-data-transmission</ref>
 For analog communication in general:

@@ Line 20: / Line 20: @@
 * FSK is less susceptible to errors and interference than ASK because interference is often confined to a specific frequency.
 * PSK is the least susceptible to error of these three. In terms of bit error rate (BER), binary PSK is about twice as good as ASK and FSK in the presence of noise, and the BER can be significantly improved through other techniques.
-*OFDM can also be used. It is very spectrally efficient.
+*OFDM can also be used. It is very spectrally efficient. <ref>https://space.stackexchange.com/questions/15428/what-is-the-advantage-of-qpsk-over-fsk-or-ask-for-satellite-data-transmission</ref>
 For analog communication in general:
@@ Line 35: / Line 35: @@
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 If you are done reading this page, you can go back to [[Communications Subsystem]]

← Older revision		Revision as of 17:28, 1 February 2018
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	== Some Pros and Cons of General Modulation Schemes ==		== Some Pros and Cons of General Modulation Schemes ==
		+	For digital communication in general:
		+	* ASK is very inefficient and susceptible to interference for wireless (but can be useful over fiber optics or copper).
		+	* FSK is less susceptible to errors and interference than ASK because interference is often confined to a specific frequency.
		+	* PSK is the least susceptible to error of these three. In terms of bit error rate (BER), binary PSK is about twice as good as ASK and FSK in the presence of noise, and the BER can be significantly improved through other techniques.
		+	*OFDM can also be used. It is very spectrally efficient.

		+	For analog communication in general:
		+	* AM is efficient in terms of bandwidth and has simple receiver circuit but subjected to amplitude variations due to noise and interference
		+	* FM is less susceptible to interference and noises. But has complex circuits and requires large bandwidth.
		+	* PM is not affected by channel noise but on the other hand it has complex circuit as compare to AM and FM.
		+	For in-depth detail of various modulation schemes you can refer to [http://berk.tc/habsis/mod1.pdf this document].

		+	== Demodulation ==
		+	Demodulation is technique to obtain message signal from the receive signal. Modulation and demodulation go hand in hand. Following block diagram gives a general idea:
		+
		+	[[File:Modulation.png\|frame\|center]]
		+
		+	----
	If you are done reading this page, you can go back to [[Communications Subsystem]]		If you are done reading this page, you can go back to [[Communications Subsystem]]

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 * Without modulation, size of the antenna will become very large and it will make antenna size in order of km for message signal of kHz order.
 * For reliable and effective communication over long distance i.e. minimizing the signal losses during transmission.
-* As signal band is limited (from few MHz to maybe some GHz) we have to use as low bandwidth of signal as low as possible. (i.e. maximizing the use of bandwidth allocated) <br \><br \><br \>
+* As signal band is limited (from few MHz to maybe some GHz) we have to use as low bandwidth of signal as low as possible. (i.e. maximizing the use of bandwidth allocated) <br \>
 == How to decide type of Modulation? ==