CHAPTER 1 BLAKE
equipment that sparks
"Man-made" noise can come from:
equal power per octave
"Pink" noise has:
1.5
A microwave receiver has a noise temperature of 145 K. Find its noise figure.
wavelength
A radio signal's ____________________ is the distance it travels in one cycle of the carrier.
noise blanking blanking
Disabling a receiver during a burst of atmospheric noise is called ____________________.
- creation of harmonics of baseband frequencies - baseband frequencies "mixing" with each other - shift in phase relationships between baseband frequencies "all of the above"
Distortion is caused by: - creation of harmonics of baseband frequencies - baseband frequencies "mixing" with each other - shift in phase relationships between baseband frequencies - all of the above
When current flows through a diode, it generates shot noise that can be represented as a current source, the output of which is a noise current. The equation for the noise current is very similar to the equation for thermal noise voltage. Since the power in the shot noise is proportional to the diode current, controlling the diode current controls the noise power.
Explain why you could use a diode as a noise source with a spectrum close to that of pure thermal noise. How would you control the amount of noise generated?\
Frequency-Division Multiplexing
FDM stands for:
solar
For satellite communications, ____________________ noise can be a serious problem.
TDM
In ____________________, multiple signal streams take turns using the channel.
FDM
In ____________________, you split the bandwidth of a channel into sub-channels to carry multiple signals.
300 million
In free space, radio signals travel at approximately ____________________ meters per second.
Fourier
Mathematically, a spectrum is represented by a ____________________ series.
Thermal, Shot, Partition, 1/f, transit-time
Name five types of internal noise.
Source, Transmitter, Channel, Receiver, Destination
Name the five elements in a block diagram of a communications system.
how much noise an amplifier adds to a signal
Noise Figure is a measure of:
a. the sender b. the channel c. the receiver
Noise in a communication system originates in:
a. the sender b. the channel c. the receiver d. all of the above***
Noise in a communication system originates in:
2π × f
Radians per second is equal to:
1901
Radio signals first were sent across the Atlantic in the year ____________________.
a. signal voltage divided by noise voltage b. signal power divided by noise power c. first add the signal power to the noise power, then divide by noise power "d. none of the above"
SINAD is calculated as: a. signal voltage divided by noise voltage b. signal power divided by noise power c. first add the signal power to the noise power, then divide by noise power d. none of the above
transistors and diodes
Shot noise is generated in:
signal power divided by noise power
Signal-to-Noise ratio is calculated as:
pink noise
So called "1/f" noise is also called:
Time-Division Multiplexing
TDM stands for:
bandwidth
The 'B' in Hartley's Law stands for ____________________.
300
The UHF band starts at ____________________ MHz.
30
The VHF band starts at ____________________ MHz.
zero
The bandwidth of an unmodulated carrier is ____________________.
approximately 3 kHz
The baseband bandwidth for a voice-grade (telephone) signal is:
- frequency-domain representation - spectrum - Fourier series "all of the above"
The collection of sinusoidal frequencies present in a modulated carrier is called its:
- frequency-domain representation - spectrum - Fourier series "all of the above"
The collection of sinusoidal frequencies present in a modulated carrier is called its: - frequency-domain representation - spectrum - Fourier series - all of the above
- frequency-domain representation - spectrum - Fourier series "all of the above"
The collection of sinusoidal frequencies present in a modulated carrier is called its: a. frequency-domain representation b. spectrum c. Fourier series "all of the above"
spectrum analyzer
The equipment used to show signals in the frequency domain is the _________________________.
base
The frequency band used to modulate the carrier is called the ____________________ band.
20 dB, NF = 100
The input to an amplifier has a signal-to-noise ratio of 100 dB and an output signal-to-noise ratio of 80 dB. Find NF, both in dB and as a ratio.
channel
The job of the carrier is to get the information through the ____________________.
its amplitude, frequency, and phase angle
The part, or parts, of a sinusoidal carrier that can be modulated are:
Marconi
The person who sent the first radio signal across the Atlantic ocean was:
greater at low frequencies
The power density of "flicker" noise is:
1863
The telephone was invented in the year ____________________.
Maxwell
The theory of radio waves was originated by:
Hertz
The transmission of radio waves was first done by:
the distance a wave travels in one period
The wavelength of a radio signal is:
electrons
Thermal noise is caused by the random motions of ____________________ in a conductor.
transistors and diodes ; copper wire ; resistors "all of the above"
Thermal noise is generated in:
transistors and diodes ; copper wire ; resistors "all of the above"
Thermal noise is generated in: a. transistors and diodes b. copper wire c. resistors d. all of the above
5.4
Two cascaded amplifiers each have a noise figure of 5 and a gain of 10. Find the total NF for the pair.
very high
VHF stands for the ____________________ frequency band.
Light is pink when it contains more red than it does other colors, and red is at the low end of the visible spectrum. Likewise, pink noise has higher power density at lower frequencies.
What is "pink noise"?
VT = sqrt(V1 × V1 + V2 × V2)
When two noise voltages, V1 and V2, are combined, the total voltage VT is:
multiplexing
When two or more signals share a common channel, it is called:
White light is composed of equal amounts of light at all visible frequencies. Likewise, thermal noise has equal power density over a wide range of frequencies.
Why is thermal noise called "white noise"?