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What are the advantage and disadvantage of SSB sc modulating signal?
The advantages of DSB-SC are that power consumption is nominal, the power from the signal can be contained in four sidebands, and the bandwidth is double the amount in the signal.
What is narrow band FM and how a narrow band FM generate?
If the modulation index of FM is kept under 1, then the FM produced is regarded as narrow band FM. Lower the modulation index, lower the no. of significant sidebands are produced (with reference to bessel function). So lower the no. of significant sideband, lowerer will be the bandwidth of the resulting FM prduced. Sometimes, Narrow Band FM is regarded as, when the significant energy in FM occupies the same bandwidth as ordinary AM with the same modulating signal.
How does a high-power FM transmitter work?
Summary: An FM transmitter has an oscillator that generates the carrier RF signal. Frequency modulation takes place at the oscillator stage. The modulated signal is then sent through some filters and then finally amplified by a class C power amplifier, and then delivered to the antenna. An FM transmitter has an oscillator that generates a carrier signal on a desired frequency. But something like a voltage controlled oscillator is used so that the oscillating frequency can be changed by a modulating signal. When there is no modulation, the oscillator runs at it assigned frequency (called a center frequency). The voltage that is controlling the frequency at which it is running is constant. By applying the volage of a modulating signal to that "controlling" voltage, the frequency of the signal can be caused to vary above and below its assigned center frequency in a way that is directly proportional to the modulating signal. It is shifted above and below its assigned center at a rate proportional to the frequency of the modulating signal and at an amount proportional to the amplitude of the modulating signal. This takes up a bit of what is called bandwidth on the electromagnetic spectrum. The modulated FM signal appears as a "group" of frequencies around that center frequency with the sub-group of frequencies about the center being called the upper sideband, and that sub-group below the center being called the lower sideband. Almost all of the power in the generated signal is carried in these sidebands. This RF signal is them amplified by a high power RF amp, and the (now) high-powered FM signal is then sent via a transmission line to an antenna, from where the signal radiates into space. A link is provided to the Wikipedia article on FM modulation. Surf on over and check out the drawings and the little "moving pictures" to get a handle on FM. (No static at all!)
What is the difference between am-dsb and am-ssb?
Am- DSB stands for Double or Duplex Side Band Am- SSB- amplitude modulation, which is what Am means, Single-Side-Band, sideband sometimes written as one word but abbreviated phonetically as SSB. SSb is widely used in amateur radio and some forms of CB as well. the concept is related to the much older, and still viable idea of Bandspreading, or Bandspread where the tuning is split over two dials or a subdial for the fine-tuning harmonics. applied to receivers only. Get some old electronics magazines from the thirties from Lindsay"s publications, angled at the hobbyist they explain things as they go along. the Gernsback l934 Short wave manual is good technical theory and also has reviews and circuit diagrams of many then current radio gear, great fun for browsing.=and technically correct. ********************************************************** Normal a.m. transmission has a carrier and two identical sidebands, the upper and lower. That's a.m. d.s.b. (double sideband). The sum of the power in the two sidebands can't exceed half that of the carrier. For example, a 100W carrier modulated to 100% will have 25W in each sideband. It is possible to achive better efficiency by suppressing the carrier, which means that half the transmitted power will be in each sideband. That's still d.s.b., with the addition of s.c. to indicate the difference. A further increase in efficiency can be achived by also suppressing one of the sidebands, so all of the transmitted power is in that sideband. That is what is normally referred to as s.s.b., but more correctly it's s.s.b. s.c.
What is the generation of Single Sideband?
It is the separation of the inverted bands of signals which are formed when an audio signal is mixed with a carrier. This was once thought to be Amplitude Modulation but in fact results in the original carrier plus 2 bands of signals translated from audio to Radio Freq. when they were mixed. They lie on either side of the carrier freq, with the lows adjacent to the carrier and heading away in both directions, LF or HF from carrier frequency to higher tones. For Single Side Band (SSB) use, the carrier is suppressed at generation, as far as is possible, by the use of a balanced modulator in order not to be present in the final signal, in order not to radiate. The side-band chosen for suppression is then attenuated by various methods, modern systems using a crystal filter no wider than the audio band width required for the purpose in hand. It can also be achieved by phasing in the generation stage. Speech is often tailored to as low as 1.8 khz band width, 2.4 khz at the most, for comms. purposes. The advantages of this system over the original double side-band plus carrier, erroneously named AMPLITUDE modulation, are many. Economies of :- Spectrum occupation: Although inverted, both side-bands contain identical information. We really don't need to send it twice in order to reproduce the original sound at the other end. Saves valuable space in the spectrum. Narrow Receive filters will get rid of the next-door neighbours when the system takes advantage and packs more stations into the newly available space. Power: The suppression of the unnecessary side-band reduces the power used and /or the power handling requirements of the device needed to generate the transmitted signal. Alternatively the saved power can be devoted to the wanted side-band, thus increasing the signal at the far end. Similarly, suppressing the carrier will save even higher levels of power, with all the same benefits. The carrier is crucial in the final signal but very easy to re-insert at the receiver end for microscopic amounts of power, ironically in a similar circuit to that which suppressed it in the first. Yet another significant power saving is the removal of the need for a high power audio amplifier used to modulate (mix really) the audio onto the transmitter at very high levels. With the high level "modulation" audio power of 50% of the transmitter power is needed. A 1kW transmitter needs 500 watts of audio whereas done in the early stages of the transmiiter, it needs micro-watts. Outcome: Either lower power consumed or more "talk power" (with the associated increase in signal strength at the far end) for a given amount of power. The original power level had to include 3 sets of signals..Two sidebands, only one of which is needed and an enormous carrier, which isn't needed at all. This shows that it wasn't a carrier after all. How you know that the carrier is on the correct frequency, as you tune your receiver? The other fellow stops sounding like Donald Duck, when you get it right.............easy!
How are side bands produced?
Sidebands are produced when a carrier signal is modulated, typically through amplitude modulation (AM) or frequency modulation (FM). In AM, variations in the amplitude of the carrier signal create additional frequency components above and below the carrier frequency, known as sidebands. In FM, changes in the frequency of the carrier induce sidebands at varying distances from the carrier frequency, depending on the modulation index. These sidebands contain the information being transmitted and are essential for demodulating the signal at the receiver.
What are the frequency components at the output of the modulator?
The frequency components at the output of a modulator typically include the carrier frequency and the sidebands generated by the modulation process. For amplitude modulation (AM), the output contains the carrier frequency along with upper and lower sidebands, which are spaced from the carrier by the modulating frequency. In frequency modulation (FM), the output consists of the carrier frequency and a series of sidebands determined by Bessel functions, reflecting the modulation index. The specific frequencies present depend on the modulation scheme and the characteristics of the input signal.
A modulated waveform that contains a carrier plus two sidebands for each modulation frequency is a description of?
Both AM and narrow-band-FM.
What are the frequency components in an am wave?
An AM wave consists of two frequency components: a carrier wave at the original frequency of the transmitted signal, and two sidebands that are located just above and below the carrier frequency. The sidebands contain the original signal information and are responsible for carrying the actual audio content.
What is the meaning of suppressed carrier in am?
radio an amplitude-modulated wave in which only the sidebands are transmitted, the carrier being removedhttp://dictionary.reference.com/browse/suppressed+carrier+modulation
Mathematical expression for side band amplitudes in FM signal?
In frequency modulation (FM), the sideband amplitudes can be expressed using Bessel functions. For an FM signal with a modulation index ( \beta ) (the ratio of the frequency deviation to the modulation frequency), the amplitudes of the sidebands are given by ( J_n(\beta) ), where ( J_n ) is the Bessel function of the first kind of order ( n ). The sideband amplitudes corresponding to the carrier frequency will have values of ( J_n(\beta) ) for ( n = 0, \pm 1, \pm 2, \ldots ). Thus, the total signal can be represented as a sum of these sidebands, modulated around the carrier frequency.
How transmitted power is related to modulation index in am?
In amplitude modulation (AM), the modulation index (m) represents the ratio of the peak amplitude of the modulating signal to the peak amplitude of the carrier signal. The transmitted power in an AM signal increases with the modulation index, as higher modulation indices lead to greater variations in the carrier's amplitude. Specifically, the total transmitted power can be expressed as a function of the carrier power and the modulation index, with more power being allocated to sidebands as m increases. However, beyond a certain point, further increasing the modulation index can lead to distortion, as the signal may exceed the linear range of the amplifier.
Is ferquency modulation a linear modulations?
Frequency modulation (FM) is considered a form of nonlinear modulation. In FM, the frequency of the carrier wave varies in accordance with the amplitude of the input signal, which can lead to a complex relationship between the input and output signals. This nonlinearity is characterized by the generation of sidebands and additional frequency components that are not present in the original signal. Thus, FM does not maintain a direct proportionality between input and output, distinguishing it from linear modulations like amplitude modulation (AM).
How does the frequency change in a FM transmitter?
-- the modulation index varies -- the instantaneous deviation varies -- the amplitude of the carrier component varies -- the spectrum of sidebands varies -- the total occupied bandwidth varies
In frequency modulation what happens to the bandwidth when you increase the modulating frequency?
Bandwidth increases as a function of both modulating frequencyand deviation. As deviation increases, pairs of sidebands are generated, each equal to fc+m and fc-m, fc+2m, fc-2m etc. where fc = the carrier frequency and m = the modulating frequency. Increasing modulation (frequency deviation) will change the level of each of the sideband pairs - and the carrier, which at times falls to zero.
AM power content of the carrier is maximum when modulation index is?
The AM power content of the carrier is maximum when the modulation index is zero. At this point, there is no modulation applied to the carrier signal, meaning the entire power is concentrated in the carrier frequency itself. As the modulation index increases, the power is distributed between the carrier and the sidebands, resulting in a decrease in the carrier's power content. Thus, maximum carrier power occurs at zero modulation.
What is standard AM sideband?
Standard AM sideband refers to the amplitude modulation (AM) technique where a carrier wave is modulated by an audio signal, producing two sidebands: the upper sideband (USB) and the lower sideband (LSB). In traditional AM broadcasting, both sidebands and the carrier are transmitted, resulting in a wider bandwidth and potentially more power usage. However, sideband modulation techniques like single sideband (SSB) can transmit only one of the sidebands and the carrier can be suppressed, allowing for more efficient use of bandwidth and power. Standard AM is commonly used in AM radio broadcasting.
