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Is The carrier frequency is usually lower than the modulating frequency?
Wiki User
∙ 8y ago
when the frequency is low , energy will be obviously low. To increase the energy of the signal we need to increase the frequency. This is achieved by multiplying the message signal with the carrier signal (with high frequency).
Abdullah Firas Salma...
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If the frequency in AM does not change then how are these sidebands formed?
The process of changing the amplitude of the "carrier" so as to add information to it (modulation) doesn't change the frequency of the carrier. But it does create energy at two other newfrequencies.The new frequencies are equal to (carrier frequency) plus and minus (the modulating frequency). These are referred to as the upper and lower sidebands.The upper sideband is an exact copy of the modulating signal, but with every component of it shifted up by an amount equal to the carrier frequency. The lower sideband is a mirror image of the upper sideband, with every frequency component in it reflected about the carrier frequency.
The relationship of the bandwidth required for double-sideband emitted carrier AM to the bandwidth of the modulating signal of?
In Amplitude Modulation (AM), specifically in the case of Double Sideband Suppressed Carrier (DSB-SC) or Full Carrier (DSB-FC) AM, the required bandwidth is twice the bandwidth of the modulating signal. If the modulating signal has a bandwidth of B Hz, the bandwidth required for AM would be 2B Hz. This is because both the upper and lower sidebands of the carrier wave are utilized in the modulation process, each consuming bandwidth equivalent to the original signal.
What property of modulating frequency is varied for frequency deviation?
FM is the carrier property when terms like `frequency deviation' are used. Unlike AM, which has a single frequency, and the frequency is modulated by increasing the amplitude of the frequency, with FM, it's the frequency itself that is changed, either by making the frequency a bit higher or lower from the actual stated frequency. For instance, a FM radio station located at 100.00 on the dial will have the frequency deviate by plus or minus 75 kilohertz (+100.075 HZ or - 99.925 HZ.) or more commonly referred to as a bandwidth of 150 KHZ. for 100% modulation.
When you do modulation in time domain you get modulated waveform of modulating signal information and carrier. How can you recognize the upper and lower side bands in time domain modulated waveform?
You need modulation signal(carrier) which is a required signal in order to make envelope of time domained signal(target signal). The modulating signal is imposed on modulation signal.This creates envelope of waveform which is modulated(desired) signal. Now, the desired signals uper and lower sideband of signal strictly depends on modulation signal's bandwidth. Max. peak of that signal is uper sideband and min. peak is lower sideband for this modulated signal.
How does the intelligence signal modulates the carrier?
There are three major types of modulation:AM, Amplitude Modulation, where the modulation signal is altering the amplitude of the carrier according to its own amplitude, normally this is done in the output stage. Therefor a strong audio signal is necessary at the same or a little less than the power of the carrier, never higher, because that will over modulate the carrier that will resort in distortion of the receiver output. AM is used in the lower band of the RF spectrum.FM, Frequency Modulation, where the frequency of the carrier is altered by the audio signal. When the amplitude of the audio is going higher the frequency go lower. Modulation happen at the oscillator stage, therefor a small audio signal is used to modulate the frequency. FM is normally used in the higher frequency range of the RF spectrum, 50MHz and up.FSK, Frequency-shift keying, used for data transmission, this type of modulation is simply, switching the carrier on and of, a high bit will switch the oscillator on and a low bit will switch it off, in some designs a low will be on and a high off.
If the frequency in AM does not change then how are these sidebands formed?
The process of changing the amplitude of the "carrier" so as to add information to it (modulation) doesn't change the frequency of the carrier. But it does create energy at two other newfrequencies.The new frequencies are equal to (carrier frequency) plus and minus (the modulating frequency). These are referred to as the upper and lower sidebands.The upper sideband is an exact copy of the modulating signal, but with every component of it shifted up by an amount equal to the carrier frequency. The lower sideband is a mirror image of the upper sideband, with every frequency component in it reflected about the carrier frequency.
How are electrical signals turned into data in microwave transmission?
This is usually done by modulating a much lower frequency carrier with the signal, then superheterodyning this carrier upconverting it into the desired microwave band. A corresponding superheterodyne receiver downconverts the microwave signal to a lower intermediate frequency which is then demodulated to recover the original signal.
What causes sideband frequency?
If you subtract from the carrier frequency the frequency of the tone that modulates it, then filter out the carrier frequency, then you have a lower sideband frequency. If you add to the carrier frequency, filter out the carrier, then you have an upper sideband frequency.
The relationship of the bandwidth required for double-sideband emitted carrier AM to the bandwidth of the modulating signal of?
In Amplitude Modulation (AM), specifically in the case of Double Sideband Suppressed Carrier (DSB-SC) or Full Carrier (DSB-FC) AM, the required bandwidth is twice the bandwidth of the modulating signal. If the modulating signal has a bandwidth of B Hz, the bandwidth required for AM would be 2B Hz. This is because both the upper and lower sidebands of the carrier wave are utilized in the modulation process, each consuming bandwidth equivalent to the original signal.
What are the parameters of high frequency carrier that may be varied by a lower frequency intelligence?
Following are the 3 parameter by which high Frequency carrier can be varied by low frequency intelligence signal 1) Amplitude 2) Phase 3) Frequency
What factor determines the spacing of the sidebands in an amplitude modulated signal?
Its a function of the signal bandwidth. If you modulate a 1 MHz carrier with a 1 KHz sine wave, you will see three peaks in the frequency domain - the carrier - the carrier minus 1 KHz - and the carrier plus 1 KHz. If the carrier is 100 MHz, the spacing is still the same, unless you consider spacing to be proportional to the carrier frequency - but that does not seem to be the question. Improved. Bandwidth is a function of modulating frequency in simple Amplitude Modulation. As described above, 1 MHz signal with 1 kHz modulation creates a lower side frequency (1000 - 1) = 999 kHz, the carrier = 1000 kHz and the upper side frequency 1001 kHz. These two side frequencies exist up to the point of 100% modulation. Over 100% modualtion, large numbers of extra side frequencies ("Splatter") will exist. Since we rarely use single-tone modualtion, but a spectrum of modulating frequencies, the upper and lower energy appears within the two side bands - commonly called sidebands. The composite signal now comprises a lower sideband, which (for a maximum modulating frequency Fm) extends "down" to Fc-Fm, the carrier (Fc), and the upper sideband, which extends "up" to Fc+Fm. Be aware that advanced AM techniques, such as SSB-SC and VSB may use half the bandwidth of full-carrier, both-sidebands AM. Also, be aware that AM techniques used in digital data (QAM, Trellis coding, etc) processing differ from the "audio/broadcast" descriptions above.
What property of modulating frequency is varied for frequency deviation?
FM is the carrier property when terms like `frequency deviation' are used. Unlike AM, which has a single frequency, and the frequency is modulated by increasing the amplitude of the frequency, with FM, it's the frequency itself that is changed, either by making the frequency a bit higher or lower from the actual stated frequency. For instance, a FM radio station located at 100.00 on the dial will have the frequency deviate by plus or minus 75 kilohertz (+100.075 HZ or - 99.925 HZ.) or more commonly referred to as a bandwidth of 150 KHZ. for 100% modulation.
Why FM have infinte number of sidebands?
It can't. FM (like broadcast AM) has two *sidebands*, one at a higher frequency than the transmitter's carrier, one at a lower frequency. The modulating signal (voice, music, etc) of any trasnmitter creates one or more pairs of side frequencies within the two sidebands. A broadcast AM signal can only produce two side frequencies, so an AM transmitter at 1.5 MHz, with a 1 kHz modulating tone (fm), would put out its carrier (fc) at 1.5 MHz, a lower side frequncy at (1.5 - 0.001) = 1.499 MHz, then its carrier at 1.5 MHz, and then the upper side frequency at (1.5 + 0.001) = 1.501 MHz. The AM signal can never be wider than twice the highest modulating frequency (fm), spanning from (fc - fm) to (fc + fm), a span of 2 x fm. Be aware that special-purpose AM systems can generate just *one* sideband - we won't go into that amount of detail apart from noting it. FM signals can be wider than twice the highest modulating frequency. The complete analysis needs the mathematical Fourier Transform, but we can think of it this way. Stronger frequency modulation shows up as a larger change in the transmitted signal frequency. An FM signal at 100 MHz, modulated by a 1 KHz tone, *can* put out a lower side frequency at (100 - 0.001) = 99.999 MHz and an upper side frequency at (100 + 0.001) = 100.001 MHz. You could receive this just fine, but it would sound "weak" compared to normal broadcasts. It's possible to increase the frequency shift to (say) five times. Now, the sidebands must extend from (100 - 5x0.001) = 99.995 MHz to (100 + 5x0.001) = 100.005 MHz. How do we account for the original 1 KHz tone creating a bandwidth of 2x5 kHz? The answer is that we actually have *five* lower side frequencies, at -5, -4, -3, -2, -1 kHz below the carrier, and *five* upper side frequencies at +1, +2, +3 +4 and +5 kHz above the carrier. Notice that they are multiples of the original 1 kHz modulating frequency. These can, in fact, be shown on the instrument called a spectrum analyser. Your question? As with broadcast AM, an FM signal has only two sidebands. In FM, the strength of modulation (the modulation index) controls the number of individual side frequencies, and thus the total bandwidth of the signal. Can an FM signal have *infinite* numbers of side frequencies? Not really. It can have a *very large* number of side frequencies with very great modulation strength. In practice, this would take up *a lot* of the FM radio band, so broadcast FM commonly uses a maximum modulation index of 5.0. This means that a fully-modulating 15 kHz signal would give a bandwidth of -(15 x 5) to +(15 x 5) kHz, which is +/- 75 kHz.
When you do modulation in time domain you get modulated waveform of modulating signal information and carrier. How can you recognize the upper and lower side bands in time domain modulated waveform?
You need modulation signal(carrier) which is a required signal in order to make envelope of time domained signal(target signal). The modulating signal is imposed on modulation signal.This creates envelope of waveform which is modulated(desired) signal. Now, the desired signals uper and lower sideband of signal strictly depends on modulation signal's bandwidth. Max. peak of that signal is uper sideband and min. peak is lower sideband for this modulated signal.
Do waves with longer wavelengths have higher or lower frequency's?
Speed (of the wave) = wavelength x frequency. Therefore, since the speed usually doesn't change much, longer wavelength means lower frequency.
What are the frequency limits for carrier signals used by other AM stations in that area?
No higher than 1090 kHz and no lower than 1110 kHz
What is difference between modulator and demodulator?
Modulation is used when information is available in analog form that varies the frequency and/or amplitude of a lower frequency wave, depending on the information it carries. The role of modulation is to place this information onto a carrier frequency that can be transmitted more readily and with least loss of information. There are three fundamental types of modulation - frequency modulation, amplitude modulation and phase modulation. In each of these, a carrier frequency is modulated by a lower frequency, to form a modulated carrier wave. A modulator modulates the carrier frequency, while a demodulator detects the modulation on the carrier wave and recovers the original lower frequency waveform at the destination. For many years the modulated carrier wave was converted to a radio signal. Now it is often an electrical signal which is sent down a teleohone line; the information is usually a set of pulses going between computers. When computers are connected to each other in a two-way conversation, the MOdulator and DEModulator are combined into a single device called a MODEM.
