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Questions and Answers
What is the output impedance of the RF amplifier if the antenna impedance is 502 and the impedance of the antenna matching network is 6500?
What is the output impedance of the RF amplifier if the antenna impedance is 502 and the impedance of the antenna matching network is 6500?
- 6000
- 6500 (correct)
- 500
- 7000
If 90% of an RF power amplifier's output power is transferred to the antenna, what is the antenna power if the input power to the amplifier with a gain of 2000 is 3W?
If 90% of an RF power amplifier's output power is transferred to the antenna, what is the antenna power if the input power to the amplifier with a gain of 2000 is 3W?
- 6666W
- 6000W
- 5400W (correct)
- 1800W
If an antenna with an impedance of 1051 has a 20 V voltage drop, what is the antenna's power?
If an antenna with an impedance of 1051 has a 20 V voltage drop, what is the antenna's power?
2W
If the total AM signal power is 600W and the transmission efficiency is 0.25, what is the carrier signal power (PC)?
If the total AM signal power is 600W and the transmission efficiency is 0.25, what is the carrier signal power (PC)?
In the equation Po = Pr - (Pr x MI), what does (Pr x MI) represent?
In the equation Po = Pr - (Pr x MI), what does (Pr x MI) represent?
In FM, the carrier frequency deviates with changes in what parameter(s) of the message signal?
In FM, the carrier frequency deviates with changes in what parameter(s) of the message signal?
In PM, the carrier frequency deviates with changes in what parameter(s) of the message signal?
In PM, the carrier frequency deviates with changes in what parameter(s) of the message signal?
Why can a limiter circuit be used to cut off the peaks and valleys of an FM or PM signal?
Why can a limiter circuit be used to cut off the peaks and valleys of an FM or PM signal?
What frequencies are contained in the AM radio signal when a 3 kHz message signal modulates an 800 kHz carrier signal?
What frequencies are contained in the AM radio signal when a 3 kHz message signal modulates an 800 kHz carrier signal?
What is the transmission efficiency (u) if the sideband power (PSB) of an AM signal is 3.3W and the total power (PT) is 10W?
What is the transmission efficiency (u) if the sideband power (PSB) of an AM signal is 3.3W and the total power (PT) is 10W?
In AM transmission, what is the optimum percentage of modulation?
In AM transmission, what is the optimum percentage of modulation?
If the antenna matching network of an RF power amplifier is adjusted to an impedance of 650Ω and the antenna impedance is 500Ω, what is the output impedance of the RF amplifier?
If the antenna matching network of an RF power amplifier is adjusted to an impedance of 650Ω and the antenna impedance is 500Ω, what is the output impedance of the RF amplifier?
What is the antenna power when 90% of an RF power amplifier's output power is transferred to the antenna, given the input power to the amplifier is 3W with a gain of 2000?
What is the antenna power when 90% of an RF power amplifier's output power is transferred to the antenna, given the input power to the amplifier is 3W with a gain of 2000?
An antenna with an impedance of 100Ω has a 20V peak voltage drop. What is the antenna's power?
An antenna with an impedance of 100Ω has a 20V peak voltage drop. What is the antenna's power?
If the transmission efficiency (µ) of an AM transmitter is 0.25 and the total AM signal power (PT) is 600W, what is the carrier signal power (PC)?
If the transmission efficiency (µ) of an AM transmitter is 0.25 and the total AM signal power (PT) is 600W, what is the carrier signal power (PC)?
In the equation Pc = PT - (PT x µ), what does (PT x µ) represent in relation to the carrier signal power (PC) in AM transmission?
In the equation Pc = PT - (PT x µ), what does (PT x µ) represent in relation to the carrier signal power (PC) in AM transmission?
What is true at the resonant frequency (f0) when an RF filter (an LC circuit) is tuned for an AM frequency?
What is true at the resonant frequency (f0) when an RF filter (an LC circuit) is tuned for an AM frequency?
What is the bandwidth requirement of the RF filter in an AM radio system with a 10 kHz bandwidth when commercial AM broadcasting stations operate in the frequency range from 540 kHz to 1600 kHz?
What is the bandwidth requirement of the RF filter in an AM radio system with a 10 kHz bandwidth when commercial AM broadcasting stations operate in the frequency range from 540 kHz to 1600 kHz?
Why is it necessary to tune the RLC network in the Q3 collector circuit of the RF amplifier to the frequency selected by the RF filter?
Why is it necessary to tune the RLC network in the Q3 collector circuit of the RF amplifier to the frequency selected by the RF filter?
What is the power gain of an RF stage when the power at the input is -90 dBm and the output power is -20 dBm?
What is the power gain of an RF stage when the power at the input is -90 dBm and the output power is -20 dBm?
At the RF amplifier output where the carrier signal is 250 mVrms and the output impedance is 3 kΩ, what is the rms power of the carrier signal?
At the RF amplifier output where the carrier signal is 250 mVrms and the output impedance is 3 kΩ, what is the rms power of the carrier signal?
In FM, the carrier frequency deviates with changes in what parameter(s) of the message signal?
In FM, the carrier frequency deviates with changes in what parameter(s) of the message signal?
In PM, the carrier frequency deviates with changes in what parameter(s) of the message signal?
In PM, the carrier frequency deviates with changes in what parameter(s) of the message signal?
Why can a limiter circuit be used to cut off the peaks and valleys of an FM or PM signal?
Why can a limiter circuit be used to cut off the peaks and valleys of an FM or PM signal?
A 4 kHz message signal causes an FM carrier signal to have a frequency deviation of +20 kHz. What is the MI? MI = fcd/fm
A 4 kHz message signal causes an FM carrier signal to have a frequency deviation of +20 kHz. What is the MI? MI = fcd/fm
An FM carrier signal with a MI of 4 contains a 3 kHz message signal. Determine the number of significant sideband pairs, and then calculate the bandwidth of the FM carrier.
An FM carrier signal with a MI of 4 contains a 3 kHz message signal. Determine the number of significant sideband pairs, and then calculate the bandwidth of the FM carrier.
What function does a discriminator or frequency detector perform?
What function does a discriminator or frequency detector perform?
What does the term quadrature mean?
What does the term quadrature mean?
Frequency modulation (FM) and phase modulation (PM) are subcategories of what type of modulation?
Frequency modulation (FM) and phase modulation (PM) are subcategories of what type of modulation?
When the message signal amplitude is zero, the FM carrier signal is at what frequency?
When the message signal amplitude is zero, the FM carrier signal is at what frequency?
For an FM signal, what does the term frequency deviation mean?
For an FM signal, what does the term frequency deviation mean?
Changes in the message signal amplitude and frequency cause frequency deviations in what type of modulation?
Changes in the message signal amplitude and frequency cause frequency deviations in what type of modulation?
Study Notes
Angle Modulation
- Angle modulation is a type of modulation that includes Frequency Modulation (FM) and Phase Modulation (PM)
- In FM, the carrier frequency deviates with changes in the frequency of the message signal
- In PM, the carrier frequency deviates with changes in the phase of the message signal
Frequency Modulation (FM)
- FM is a type of angle modulation
- The carrier frequency deviates with changes in the frequency of the message signal
- Frequency deviation is the change in frequency from the center frequency
- Modulation index (MI) is the ratio of frequency deviation to the message signal frequency
Phase Modulation (PM)
- PM is a type of angle modulation
- The carrier frequency deviates with changes in the phase of the message signal
- The modulation index (MI) is used to calculate the frequency deviation
Demodulation
- Demodulation is the process of recovering the original message signal from the modulated carrier signal
- A discriminator or frequency detector is used to demodulate FM signals
- A quadrature detector is used to demodulate FM signals
Quadrature Detector
- The quadrature detector shifts the phase of the FM signal by 90°
- The output of the quadrature detector is a signal that is proportional to the message signal
- The quadrature detector is used in FM demodulation
FM Signal Characteristics
- FM signals have a constant amplitude
- FM signals have a varying frequency
- FM signals are less susceptible to noise and interference
FM Applications
- FM is used in commercial broadcasts
- FM is used in radio communication systems
Communication Systems
- A communication system consists of a sender (transmitter), a transmission line or channel, and a receiver
- The transmitter modulates the message signal onto the carrier signal
- The receiver demodulates the modulated carrier signal to recover the original message signal
Amplitude Modulation (AM)
- AM is a type of modulation that involves varying the amplitude of the carrier signal
- AM signals have a constant frequency
- AM signals are more susceptible to noise and interference
AM Signal Characteristics
- AM signals have a varying amplitude
- AM signals have a constant frequency
- AM signals are more susceptible to noise and interference
AM Applications
- AM is used in radio communication systems
- AM is used in telecommunications
Antenna Matching Network
- The antenna matching network is used to match the impedance of the RF power amplifier to the antenna
- The antenna matching network is used to maximize the power transfer to the antenna
RF Power Amplifier
- The RF power amplifier is used to amplify the modulated carrier signal
- The RF power amplifier is used to increase the power of the signal transmitted to the antenna
Transmission Efficiency
- Transmission efficiency is the ratio of the output power of the RF power amplifier to the input power
- Transmission efficiency is used to calculate the power output of the RF power amplifier.### Communication Systems
- A communication system consists of a sender (transmitter), transmission line or channel (frequency), and a receiver.
Modulation and Demodulation
- Modulation is the process of changing a characteristic of a high-frequency carrier signal based on the low-frequency message signal.
- Demodulation is the reverse process of modulation, extracting the original message signal from the modulated carrier signal.
- A product detector, quadrature detector, and envelope detector are devices that perform demodulation.
Balanced Modulator
- A balanced modulator is a device that removes the lower sideband (LSB) from a double sideband (DSB) signal, producing a single sideband (SSB) signal.
- A balanced modulator can also be used to remove the carrier signal from a modulated signal, producing an SSB signal.
Frequency Modulation
- Frequency modulation is a type of angle modulation where the frequency of the carrier signal is varied in accordance with the message signal.
- The frequency range of the sidebands around a carrier frequency is called the bandwidth.
AM Signal Characteristics
- An AM signal has a carrier signal frequency and two sideband frequencies (upper sideband and lower sideband).
- The envelope of an AM signal has an irregular waveform if the message signal is a voice signal.
- The transmission efficiency (μ) of an AM transmitter is the ratio of the sideband power to the total power.
AM Transmission
- The optimum percentage of modulation for AM transmission is 100%.
- The total power of an AM signal (PT) is the sum of the carrier power (PC) and the sideband power (PSB).
Antenna and RF Power Amplifier
- The RF power amplifier provides power amplification for the antenna to radiate the RF signals over long distances.
- The antenna matching network matches the RF power amplifier's output impedance with the antenna impedance.
- The power gain of an RF amplifier is the ratio of the output power to the input power.
Filter and Resonance
- An RF filter is used to select the desired frequency and reject other frequencies.
- At the resonant frequency, the inductive reactance (X₁) equals the capacitive reactance (Xc) in an LC circuit.
Power Amplifier and Antenna
- The power amplifier output power is transferred to the antenna through the antenna matching network.
- The antenna power is determined by the output impedance of the RF amplifier and the antenna impedance.
Efficiency and Power Gain
- The transmission efficiency (μ) is the ratio of the sideband power to the total power.
- The power gain of an RF amplifier is the ratio of the output power to the input power.
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Description
This quiz tests your understanding of Frequency Modulation (FM) and Phase Modulation (PM) in communication systems, covering carrier frequency deviation and message signal parameters.
