Shunt Capacitance for Remote Radio Head Power Delivery
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Solution Overview
Problem
The use of remote radio heads at the top of antenna towers faces challenges due to voltage drops in power cables, which can lead to insufficient power supply, increased costs, and performance degradation from both I*R and dl/dt voltage drops, especially with long cable lengths and rapid current changes.
Innovation Solution
Incorporating shunt capacitance units into power cables and using programmable power supplies to maintain voltage levels and reduce voltage drops, with shunt capacitance units sized based on cable length and resistance, and programmable power supplies adjusting output voltage to compensate for current variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the radio is located at the top of the antenna tower as a remote radio head, then signal quality is improved, but voltage drops in power cables cause insufficient power supply
Solution Approach 1:
The patent changes the electrical parameters of the power delivery system by introducing shunt capacitance units that alter the voltage and current characteristics along the power cable. The capacitance values are specifically selected based on cable length and resistance to compensate for voltage drops, transforming the electrical parameter profile to maintain adequate power delivery to the remote radio head.
Solution Approach 2:
The patent introduces shunt capacitance units as intermediary elements along the power cable between the power supply and the remote radio head. These capacitance units act as mediators that store and release electrical energy to counteract voltage drops caused by cable resistance and inductance, particularly during current spikes.
2Length of moving object
If longer power cables are used to reach remote radio heads, then coverage is extended, but voltage drops increase due to cable resistance
Solution Approach 1:
The patent applies parameter changes by selecting shunt capacitance values that are directly related to the cable length and resistance characteristics. Longer cables with higher resistance are compensated by larger capacitance values, creating a scaled relationship that maintains voltage levels regardless of cable length.
Solution Approach 2:
The shunt capacitance units are pre-calculated and installed based on the specific cable length and resistance parameters before the system operates. This preliminary configuration ensures that the capacitance is optimally sized to compensate for the specific voltage drops that will occur in that cable, rather than attempting to adjust after installation.
3Productivity
If rapid current changes occur in remote radio heads, then power delivery responds to demand, but dl/dt voltage drops cause performance degradation
Solution Approach 1:
The shunt capacitance units provide beforehand cushioning by storing electrical energy in advance during normal operation. When rapid current spikes occur, the pre-charged capacitance immediately discharges to counteract the voltage drop, cushioning the remote radio head against the harmful effects of dl/dt voltage drops before they can cause performance degradation.
Solution Approach 2:
The system employs feedback mechanisms where the power supply monitors current draw and adjusts its output accordingly. The shunt capacitance units work in conjunction with this feedback control to maintain voltage stability, as the capacitance requirements are determined based on feedback regarding cable resistance and expected current variations.
4Ease of manufacture
If standard power cables are used for long distances, then installation is simple, but power losses increase and require larger cable sizes
Solution Approach 1:
The patent changes the electrical parameters of the existing standard power cable system by adding shunt capacitance units. This allows the use of standard cable sizes and installation methods while fundamentally altering the voltage and power loss characteristics through the introduced capacitance, avoiding the need for larger, more expensive cables.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach effectively maintains voltage levels during current spikes, reduces power losses, and prevents remote radio head malfunctions, allowing for longer cable runs with less material and lower installation costs while improving overall performance.
Implementation Method 1
a shunt capacitance unit may be provided between the conductors of the power cable. The shunt capacitance unit may help to reduce the magnitude of the voltage spike that might otherwise result
Implementation Method 2
V Drop may be determined according to Ohm's Law as follows: where R Cable is the cumulative electrical resistance (in Ohms) along the power supply and the return conductors
Implementation Method 3
Another physical property of the conductors of the power cable is the inductance per unit length of the conductors. In particular, the cumulative inductance of the conductors of the power cable can produce a voltage drop that is expressed as: V dI/dt Drop=L(dl/dt)
Data Source
Figure 1~2B
Figure 3A~4
Figure 5A~5C
AI summary
Tower systems suitable for use at cellular base stations include a tower, an antenna mounted on the tower, a remote radio head mounted on the tower and a power supply. A power cable having a power supply conductor and a return conductor is connected between the power supply and the remote radio head. A shunt capacitance unit that is separate from the remote radio head that is electrically coupled between the power supply conductor and the return conductor of the power cable.