Microwave Communication Basics Flashcards
Can be ____ when, in digital applications, the signal is demodulated and re-modulated before transmission to the next radio hop.
regenerative
For standard refractivity conditions, k = __ =___
1.33 = 4/3
Microwave radio provides a transmission medium for digital traffic of standard capacities typically ranging from 1.544 Mbps (1T1) to 45 Mbps (1DS3) in North America, and from 2.048 Mbps (1E1) to 34 Mbps (16E1) based on ITU standards.
Plesiochronous Digital Hierarchy (PDH)
Lowering the system gain will reduce the ___.
fade margin
The Earth’s radius model is most useful for __.
terrestrial paths
Makes it possible to utilize a common antenna for both the transmitter and receiver.
antenna-coupling unit
a calculation involving the gain and loss factors associated with the antennas, transmitters, receivers, transmission lines, and propagation environment, used to determine the maximum distance at which a transmitter and receiver can successfully operate.
link budget
The higher the frequency, the ____
narrower the Fresnel zone
Radio link typical distance can be up to ___.
25 mi (40 km)
defined as the factor that is multiplied by the actual Earth radius
effective Earth radius factor (k)
amplifies the received signal (which is at this point much weaker than when it was transmitted), filters out any undesirable signals (interfering signals)
receiver
can be described as any criterion to ensure sufficient antenna heights so that, in the worst case of refraction (for which k is minimum), the receiver antenna is not placed in the diffraction region.
Clearance
Radio stations between two terminal stations are called ___.
Repeater stations (active or passive)
lower k-values will lower the ___
LOS
The purpose of _____ to generate the carrier frequency that is to be used for the communication, to modulate this carrier frequency with the desired information, and finally, to amplify the signal
transmitter
microwave radios are typically used for high-capacity backbone systems.
Synchronous Digital Hierarchy (SDH) / Synchronous Optical Network (SONET)
Transmitted information can be ____.
Voice
data
video
to interconnect the antenna with the transmitter/receiver
transmission lines
antenna must have clearance of ___ percent or greater at k=4/3
100
Made by a number of intermediate repeaters with or without partial payload drop-insert.
Single connection links
Combination of these three components is called ____.
Radio terminal
A functionality provided in analog and digital repeaters, where only radio-system specific control and service channels, and possibly part of the payload, are made available for local traffic and system management and maintenance.
Drop-insert
the difference between the received signal and receiver threshold value (or sensitivity) for given Bit Error Rate (BER)
fade margin
Active repeaters can be ____ when signal is only filtered and amplified.
nonregenerative
Using the effective Earth’s radius model, ray paths between transmitters and receivers near the Earth’s surface can be __.
approximated by straight lines over a spherical Earth.
defined as the difference between the transmitter output power and the receiver threshold.
System gain
antenna must have clearance of ____ percent at the minimum k suggested for the certain path.
60
___ the signal level at which the radio runs continuous errors at a specified bit rate.
receiver sensitivity threshold
Together, feeder cable losses, antenna-coupling losses, and any additional losses (depending on the radio configuration) constitute ____.
branching losses
Radio links may be established between any two points within ___.
Line of sight
frequency
geographical region
rain statistics
implemented without any active radio components.
Passive repeaters
Three basic components of typical digital microwave radio.
- Digital modem for interfacing with digital terminal equipment
- Radio Frequency (RF) unit for converting a carrier signal from the modem to a microwave signal.
- Antenna used to transmit and receive the signal.
___ adapts the generated signal to the surrounding environment (to the propagation medium) and directs the radio waves that are to be transmitted towards the receiving station.
antenna
Sent using a highly directive parabolic shaped antenna
Microwave
The mean Earth radius is in average __.
6, 371 km
