Modulation index is used to describe the ratio of maximum frequency deviation of the RF carrier to the maximum frequency deviation of the modulating signal.
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The modulation index for phase modulation is simply the peak phase deviation.
The maximum deviation is +/- 90 degrees, regardless of frequency.
https://en.m.wikipedia.org/wiki/Phase_modulation
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Simply divide the deviation by the modulation frequency to arrive at the correct answer:
\begin{align} \text{modulation index} &= \frac{\text{deviation}}{\text{modulation frequency}} \\ &= \frac{3000 \text{ Hz}}{1000 \text{ Hz}} \\ &= 3 \end{align}
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The FM modulation index is equal to the ratio of the frequency deviation to the modulating frequency.
\begin{align} \text{modulation index} &= \frac{\text{frequency deviation}}{\text{modulation frequency}} \\ &= \frac{6\text{ kHz}}{2 \text{ kHz}}\\ &= 3 \end{align}
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The deviation ratio is the maximum carrier frequency deviation divided by the highest (maximum) audio modulating frequency: \[\text{deviation ratio}=\frac{\text{max. carrier frequency swing}}{\text{max. modulation frequency}}\]
The carrier frequency deviation is defined by the frequency swing relative to the carrier, in this case \(+5\) kHz or \(-5\) kHz, the maximum being \(5\) kHz. Therefore, the deviation ratio is:
\begin{align} \text{deviation ratio}&=\frac{5 \text{ kHz}}{3\text{ kHz}}\\ &=1.666...\approx1.67 \end{align}
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\begin{align} \text{deviation} &= \frac{\text{frequency swing}}{\text{frequency}}\\ &= \frac{7.5 \text{ kHz}}{3.5 \text{ kHz}}=2.142857...\\ &\approx 2.14 \end{align}
Thus the deviation ratio is calculated by dividing the maximum deviation by the maximum modulation: \[ \frac{\text{maximum deviation}}{\text{maximum modulation frequency}}\]
The deviation ratio of an FM-phone signal having a maximum frequency swing of \(\pm\) 7.5 kHz when the maximum modulation frequency is 3.5 kHz is 2.14.
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OFDM is capable of such high speeds by effectively combining the speeds of several digital streams. The individual signals work in parallel to communicate the information. Any type of modulation can be used on the individual signal members, known as subcarriers.
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Orthogonal Frequency Division Multiplexing is a digital modulation technique using subcarriers at frequencies chosen to avoid intersymbol interference.
Orthogonal Frequency Division Multiplexing (OFDM) is a frequency-division multiplexing (FDM) scheme used as a digital multi-carrier modulation method. A large number of closely spaced orthogonal sub-carrier signals are used to carry data on several parallel data streams or channels.
Hint: The correct answer is the one that deals with subcarriers and frequencies
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TIP: It is the only answer that has 'deviation' in it.
In FM modulation, the two primary parameters of interest are deviation ratio and modulation index. Deviation ratio is the ratio of the maximum carrier frequency deviation to the highest audio modulating frequency.
The deviation ratio of an FM-phone signal having a maximum frequency swing of plus-or-minus 5 kHz when the maximum modulation frequency is 3 kHz is 1.67.
The deviation ratio of an FM-phone signal having a maximum frequency swing of plus or minus 7.5 kHz when the maximum modulation frequency is 3.5 kHz is 2.14.
K4AGO
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http://en.wikipedia.org/wiki/Frequency-division_multiplexing
In frequency division multiplexing, a communication medium is divided into non-overlapping frequency sub-bands, which can be used to independently transmit separate information streams, or to dependently transmit a single information stream in parallel.
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Time division multiplexing (TDM) is a communications process that transmits two or more streaming digital signals over a common channel. In TDM, incoming signals are divided into equal fixed-length time slots. After multiplexing, these signals are transmitted over a shared medium and reassembled into their original format after de-multiplexing. Time slot selection is directly proportional to overall system efficiency.
Time division multiplexing (TDM) is also known as a digital circuit switched.
per https://www.techopedia.com/definition/9669/time-division-multiplexing-tdm
W5ZAP
Hint: The answer has time slot in it.
-KE0IPR
Hint: time division --> time slots
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