Core Architecture of DAS 2.0
We talked about the common components of a DAS 2.0 system and in the last post we introduced RF Signal Source.
It’s time to bring them all together and create the core architecture of DAS 2.0. Following is a simple description of the architecture of a DAS 2.0.
Our goal is to take the RF signal from the signal source located in a central area of the building like MDF room and reach that signal to all over the building’s rooms and floors so that the customer’s phones get that signal.
Core architecture of DAS 2.0 (shown with a horizontal layout)
We will start with RF Signal Source all the way to the left of the diagram. We mentioned that RF signal travels through coaxial cable; so the output of the signal source are fed into a DAS via coaxial cable.
Signal will be fed into a collection of DAS electronics commonly known as DAS Head-end. Different manufacturers have different names for the individual pieces of electronics, but essentially they all take care of a basic function: prepare the signal for distribution which also includes converting the RF signal to optical for distribution via fiber. So the first converter of the DAS will be among the head-end electronics cluster.
Let’s introduce 2 more elements which is typical among the head-end electronics.
DAS Tray: if the output of the signal source is too high we need something to lower the power of the signal. In most cases, RF Interface Unit has a defined input range, and this input is low power RF – which is a few milli watts to 3-5 watts. This is specially the case when the signal source is a base station. Base station usually have high output power and having 20 watt to 60 watt output is not unusual. We use a DAS tray in these cases. DAS Tray takes the high input from base station and brings it down to the much lower level that DAS can take.
RF Interface Unit: this is quite common for all fiber based DAS or DAS 2.0. Essentially, this unit receives the signal from the signal source and feeds into the converter and distributor. Different manufacturers have different names for this unit.
The converter(s) mentioned above in the head-end will distribute optical signal to multiple converters which are strategically located at different parts of the building. This second set of converters are known as ‘remotes’.
A software like iBwave helps the engineers going through the calculations and figure out the best locations of these remotes. Fiber length between these converters can be anywhere from a few feet to several hundred or thousands of feet. In most cases this fiber will be a single mode fiber with SC/APC or LC/APC connectors.
Remote converts the optical signal back to RF signal and sends the RF to antennas via coaxial cable. These coaxial cables will be ½” in diameter in most cases. Depending on how engineers want to split the RF we may have splitter or coupler between the remote and antennas. In most cases multiple antennas will be connected to a single remote.
In the above diagram, I have laid out the elements of DAS 2.0 horizontally. In the diagram below, I am showing essentially the same diagram (although little simplified) and vertically.
That is basically the core architecture of a DAS 2.0. In the next post we will show some of the popular DAS used in DAS and you will see how similar their core architecture are.
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