am independent sideband and vestigial sideband

Introduction

It is known from previous exercises and examination that the carrier seems to occupy about two-thirds of the total power, thus leaving a third to the sidebands. However, we are aware that the sidebands are the ones that carry the information. This would mean that the carrier is wasting power and it would be better transmit the intelligence in the sidebands.

In previous discussions, the carrier is either suppressed or reduced to attend to this matter. It has been explained that the DSBFC is the one that still contains the sideband and is wasting two-thirds of the total power. Also, the DSBSC is where the carriers are already suppressed to save power while using both of the sidebands. In a SSBFC, only one sideband is used while retaining the carrier. Finally, in SSBSC, the carrier is suppressed while using only one sideband.

AM Independent Sideband

Definition:

In Independent Sideband (ISB) modulation, the carrier and a sideband is suppressed from the signal pretty much like the SSBSC only that the suppressed signal can also be replaced by a different sideband from a different input signal of the same carrier. The manner is adding two single sideband (SSB) channels carrying different intelligences to form two sidebands around a suppressed carrier.

As can be seen in the figure above, each balanced modulator gets modulating signal from the separate audio amplifier whereas the carrier signal is fed from common crystal oscillator. The carrier is suppressed in the balanced modulator. The filters connected at the outputs of balanced modulators remove unwanted sideband, as in all other SSB systems. The difference here is that while one filter

[1] Analog Communication by Uday A. Bakshi[2] http://dictionary.reference.com/browse/telegraphy[3] http://dictionary.reference.com/browse/telephony?s=t[4]https://www.google.com.ph/webhp?sourceid=chrome-instant&ion=1&espv=2&ie=UTF-

8#q=vestige%20meaning[5]Communication Engineering by A.P. Godse and U.A. Bakshi[6] http://whatis.techtarget.com/definition/vestigial-sideband-VSB

suppresses the lower sideband, the other suppresses the upper sideband. The output of both the balanced modulators are then combined in the adder with the -26dB carrier to get two independent sidebands with reduced carrier. The up conversion is achieved by balanced mixer and high frequency crystal oscillators. For high frequency transmission additional mixer stage may be required to up convert frequency, up to the transmission frequency as shown in the figure. The resulting FR ISB signal is then amplified by the linear power amplifiers before transmission. [1]

Advantages:

Disadvantages:

Applications:

Telegraphy - a system of telecommunications involving any process providing reproduction at a distance of written, printed, or pictorial matter[2]

Telephony - a system of telecommunications in which telephonic equipment is employed in the transmission of speech or other sound between points, with or without the use of wires.[3]

AM Vestigial Sideband

Definition and Application:

From the word vestige, which means a trace of something that is disappearing or no longer existing [4], Vestigial Sideband (VSB) is a type of amplitude modulation technique that encodes data by varying the amplitude of a single carrier frequency. In VSB, the transmission is similar to SSB wherein one of the sidebands are removed however, the “removed” sideband is not actually completely removed but is rather filtered to do away with unwanted frequencies.[6]



To get a better grip of this explanation, it would be better if we present the most widely used application of this technique and explain the process. Television broadcasting is the primary application of VSB.

(Referring to the figure on the next page) A TV signal consists of the picture

(video) signal and the audio signal both having different carrier frequencies. The audio carrier is frequency modulated whereas the picture carrier is amplitude modulated. The video information typically contains frequencies as high as 4.2 MHz. A fully amplitude modulated television single would then occupy 4.2x2= 8.4 MHz. Bearing in mind filter characteristics, a transmitted bandwidth of 9 MHz would be the minimum required. This is excessive amount of bandwidth. To reduce the bandwidth to the 6 MHz maximum allowed by FCC for TV signal, a portion of the lower sideband of the TV signal is suppressed leaving only a small vestige of the lower sideband, carrier and upper sideband. The portion of the lower sideband and the carrier signal improves the response of filters near the edges of the flat pass band. As shown in the figure above, video signal is below 1.25MHz of the lower sideband (the first 0.75<Hz of it undiminished), is transmitted. This saves around 3MHz of frequency spectrum for every TV channel. The video signal from the upper sideband is completely transmitted. [5]

Advantages:



VSB enables TV signal transmission to conform to the requirements of authorities if there are any as stated above.

Relaxed Filter design

Disadvantages:

Traded bandwidth is 25% to 33% greater than SSB Demodulation system is still complex

Conclusion

There are different techniques that can be used in order to transmit the necessary information from the source to the receiver. Among these methods are ISB and VSB. Below is an illustration that can help us remember the difference between these methods for us to be able to learn when to use one and when not to.



Remarks

This is a paper is to be used as a supplement for the report to be presented by the following:

Dumagpi, Joanna KazzandraRafaela, Cristine JoyFortuna, Sean AdamCastillo, Clark Edgar JonesSombrio, Aaron ChristianGailanan, Dionisio III

Assignments:

Dumagpi – Intro and conclusion ug assist pod

Sean – Definition sa VSB

Denden – Applications sa VSB

Kring – Application sa ISB

Clark – Advantage ug disadvantages sa VSB

Aaron – Definition sa ISB

Ako na mag explain sa mga block diagrams

If naa moy dili masabtan sa akoang draft kay pangutana lang OL ko whole night salamat guys

Wala koy mahanap na summary sa advantages ug disadvantages ng ISB please help me with this kapoy naman gud basa. Hahaha. Kailangan pa man gud basahon unya ikaw pa magsummarize sa adv ud disadv thanks daan

Ako na maghimog powerpoint sabta lang gyud ninyo inyong ireport



am independent sideband and vestigial sideband

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