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DAS fiber systems accept usually 0dBm input levels but there are variations depending on the manufacturer. A multi-carrier scenario may show different input signals levels. If one carrier delivers a significantly higher signal level, it will occupy most of the available RF energy. This leads to insufficient RF levels of the remaining carriers. Equalizing will eliminate this problem; all carriers are set to an even distribution scheme.
Rx signals, delivered from the fiber system to the RF network, may be too high for the network receivers. This scenario would distort the signal and reduce overall receiver sensitivity. It is not necessary to equalize Rx signals, but signal levels need to be set to a range that meets the actual network receiver requirements
In general, the answer is yes. Wilkinson, Reactive (Airline) and Hybrid circuits are all reciprocal devices, meaning that the insertion loss from port A to port B is the same as the insertion loss measured from port B to port A. The difference is in the level of performance that your system requires.
Both combine signals to a common path but, do so in different ways.
Combiner loss is a term that refers to the theoretical loss that is incurred in a power combining situation. In a 2:1 combine, the loss is 3dB or 50% of the total input power. In a 3:1 combine, the loss is 4.8dB or ~67%. In a 4:1 combine, the loss is 6dB or 75%, and so on. Insertion loss is the theoretical combiner loss plus the dissipative loss.
Directional couplers are directional in the sense that the coupled port only couples the signal going from the input port to the output port. This is defined as “coupling.” When the return signal goes from output port to input port, the coupled port sees a very low level of that signal. This is defined as “isolation.” The directivity is defined as the “isolation” minus “coupling.” However, designers should note that directional couplers are bi-directional in the sense that the signal loss from the input port to the coupled port is the same as signal loss from the coupled port to the input port, under the law of reciprocity.
System designers have a choice in the use of directional couplers, tappers or unequal splitters in the “main spine” of a DAS.
A cross band coupler refers to the same type of device as a diplexer or filter combiner. These devices allow the combination and separation of signals in different wireless bands with higher isolation (to minimize band interaction) and without the combining loss incurred in other types of combining technologies.
Each type of filter design has its strengths and weaknesses, so here is a brief overview:
The IP (Ingress Protection) Rating is a measure of a device’s ability to withstand solid objects and liquids. In-door applications typically call for a modest rating of IP64. Outdoor ratings are typically IP65 to IP68. For a more in depth look at what these ratings actually mean, view the following website: http://www.aquatext.com/tables/ip_ratings.htm
PIM (passive intermodulation) occurs when 2 or more signals are present in a passive device that exhibits a non-linear response. The nonlinearity is caused by dissimilar metals, anodic effects, or loose connections. This nonlinearity does not manifest itself at low input signal levels and is therefore also a function of the high-power level transmit signals in the system. The resultant products are referred to as 3rd, 5th, order intermodulation products, etc. The 3rd order products are typically the focus in most system design. The real problem occurs if the 3rd order PIM products generated by the transmitter channels fall within adjacent receiver channels. This upsets the adaptive settings of the receiver and desensitization will occur. The result is typically a dropped call.
RoHS means: Restriction of Hazardous Substances. The RoHS standards have been established to control/eliminate the use of identified hazardous substances in the manufacture of products used in our market. All M2 Global’s Wireless products are RoHS compliant.
T-configuration splitters offer several advantages over in-line splitters in certain applications. They are particularly useful in leaky (radiating) cable DAS where it is necessary to separate the cables as quickly as possible in order to prevent coupling between the cables. Additionally, many installers find it easier to secure their connections when there is more space between connectors, and a torque wrench can be applied.
This is an age-old question with many different answers, depending on who you ask. And for those of you who may be confused, go ahead, and stay confused. Because there really are numerous meanings of “Calibration”.A simple definition of ‘Calibration’ when speaking of measuring instruments is to measure the accuracy of your instrument against instruments of known and higher accuracy, and adjust it as needed, to assure that it conforms to its specifications over its full range of operation.Whenever an instrument makes a measurement of an internationally accepted value (such as volts DC or AC, Ohms, Hertz, centimeters, degrees Celsius, PSI, kilograms, etc.), calibration compares the accuracy of the measured or generated value of the instrument against those international units. And if your instrument does not match those units, it is adjusted until they match (although some instruments do not have the ability to be adjusted).This is an important detail that many do not well understand. Whether you are measuring lengths to install a window, weighing produce at a grocer, pumping gasoline, monitoring steam pressure at a power plant, torqueing lug nuts on a tire of a car, or so many other examples, the instrument making the measurement must be right.For all the measured things we all use every day to work together, they must match. You measure a window frame with a ruler or tape measure to make sure its dimensions are correct, so that when you install a pre-fabbed window, it fits correctly. The manufacturer of the window at some point used calibrated instruments to make it the right size. And your tape measure or ruler were at some point compared to the same internationally accepted units to make sure they measure accurately – to make sure they matched the window.This is what calibration really is. It is making everyone’s measurements match. The accuracy of all instruments drift over time. In electronic instruments, components that make the measurements right gradually change. That means the readings made by that meter gradually wander away from their match with internationally accepted values, so it needs to be periodically checked and adjusted to make the measurement right again.
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