1A Flashcards
Frequency =
cycles per second
Bandwidth =
bits per second
This time is based off the apparent location of the sun.
Apparent Solar Time
Instruments, such as ___, help us use the location of the sun to give us the time of day.
sundials
The least accurate timing measure, it is still used in some parts of the world today.
Apparent Solar Time
Quartz Oscillators are also known as?
Crystal Oscillators
These function by resonating a tuned voltage through a crystal and the result is a resonated frequency that we use for timing.
Quartz Oscillators
Quartz oscillators function by resonating a tuned voltage through
a crystal and the result is a resonated frequency that we use for timing. This process is called the…?
piezoelectric effect
While quartz oscillators are widely used in everything from wrist watches to laboratory equipment, their accuracy and stability are affected by ___ and ___, causing them to drift in frequency.
temperature
age
Quartz oscillators are the least ___ of the oscillators.
accurate
Quartz oscillators require ___ ___ to stay precise.
periodic calibration
These oscillators take advantage of atom molecules.
Atomic oscillators
At certain frequencies, atoms release ___ that can be utilized as timing.
radiation
Also, atoms are not subject to the aging process or impacted by temperature, so they consistently stay at a ___ ___.
stable rate
Other kinds of atomic clocks have also been developed for various applications; those based on ___ offer exceptional stability, for example.
hydrogen
Today, two of the most common types of atomic oscillators are
the…?
cesium beam oscillator and the rubidium gas cell oscillator
A cesium beam oscillator’s atomic resonance is
9,192,631,770 Hertz (Hz) (9.192 GHz)
The beam is created by passing ___ metal through high heat creating the beam. The beam is put through a cavity, charging the atoms, and producing a current.
Cesium
Cesium beam oscillators are highly stable and drift only ___ nanoseconds (ns) in 24 hours.
200
Due to their high stability, they are considered primary frequency standards.
Cesium Standard
Rubidium oscillators use a “gas cell” containing rubidium gas whose atomic resonance is at
6,834,682,608 Hz (6.384 GHz)
Rubidium oscillators drift approximately ___ microsecond (μs)
every 24 hours, which means it must be calibrated periodically.
1
The secondary frequency standard.
Rubidium Standard
Rubidium has advantages over cesium, such as…?
more compact
lower in cost
more power efficient
In SATCOM ___ can be used to provide a timing standard to our equipment.
GPS
GPS timing is accomplished generally by deploying a ___ ___ whose job is to collect timing data from satellites.
passive antenna
When being created, the GPS constellation was designed to provide ___-___ visibility from anywhere in the world. However, the more satellites that the antenna can pick-up the more accurate
the timing will be.
four-satellite
The four standards for synchronization are:
plesiochronous, mutual, master clock, and master-slave.
This synchronization technique does not require synchronization between nodes. Instead, it provides a highly stable clock at each station, eliminating the need distribute time across the network.
Plesiochronous
This synchronization technique requires all network nodes have their own clocks for timing. However, the clocks are not required to be as precise. Instead, average clock data is collected from all the nodes so that all stations can operate off the same clock frequency. Network
timing continues to adjust as network nodes connect and disconnect from the network. While ____ timing requires all nodes to be connected, it does not pin a single point of failure on an unreliable node.
Mutual
This technique requires one node to be the master station. The master stating distributes timing to all other stations. A small network can benefit from this method, but it does not scale well. In a
larger network, too many nodes can create issues with too many connections. There is also a single point of failure in the master station. If the master station fails, the entire network goes down.
Master Clock
This is the most reliable synchronization technique. This method functions similar to a domino effect; one node is still required to be the master station, but after the clock signal has been distributed to the first set of subordinate nodes, it is then passed to the next level by those nodes. This method is the most robust due to the redundancy of higher subordinate nodes providing timing, and because all nodes are expected to have back-up clocks.
Master-Slave
