Wireless networks are typically realized using point-to-multipoint radios. Also, some Internet service providers (ISPs) provide Internet connectivity to remote locations by installing radio towers that use point-to-point antennas to relay the network connection to the remote location. Some radio towers include both point-to-point and point-to-multipoint radios that are driven by a ground-level base station at the base of the tower.
Space in radio towers is often at a premium, and may be expensive. In general antenna assemblies, including point-to-point and point-to-multipoint antennas assemblies typically include a single radio that operate over the full bandwidth, and transmit and receive all RF data through the antenna. Each antenna requires space and separation from other antenna to prevent undesirable interference, requiring a significant amount of tower space and therefore expense. Although antenna systems in which more than one radio may be used, these systems typically require a great deal of coordination and communication between each radio of the system, resulting a slowing and inefficiencies of the resulting antenna system and also increased cost. Further, such systems are not well able to adapt to changes in the transmission rate (or disruption of) one or more of the radios. What is needed are antenna systems that may use multiple radios connected to the same antenna assembly in a scalable (e.g., linearly scalable) manner without requiring direct communication between the multiple radios.
In any multiple-radio apparatus it may be useful to split/combine RF signals transmitted. Combiner-splitters for RF systems are known. For example, the Wilkinson divider splitter/Wilkinson combiner is a form of power splitter/power combiner that is used in microwave applications and uses quarter wave transformers, which may be fabricated as quarter wave lines on printed circuit boards. These apparatuses may provide a cheap and simple splitter/divider/combiner. The Wilkinson splitter/combiner may be formed entirely of printed circuit board transmission line components, or it may include other forms of transmission lines (e.g. coaxial cable) or lumped circuit elements (inductors and capacitors).
A Wilkinson power divider is a passive electronic device that splits a single RF input signal into two (n=2) or more (n≧3) in-phase output RF signals. Such devices can also be used in the opposite direction to combine multiple in-phase RF signals into a single RF output. The details of design and operation for these devices are well known. Such devices are typically realized using resistors and impedance-transformer sections of RF transmission line (such as coaxial line, microstrip, stripline, etc.) in various configurations.
Thus, a Wilkinson power divider or Wilkinson splitter may be used as a multiple port device, including as a two way divider. Wilkinson splitter/combiners have known benefits and problems. Advantages include: Simplicity, low cost, relatively low loss, and reasonable isolation. For example a Wilkinson divider/splitter/combiner can be realized using printed components on a printed circuit board. It is also possible to use lumped inductor and capacitor elements, but this complicates the overall design. Although the cost may otherwise be very low, to reduce losses, a low-loss PCB substrate may be used, which may increase the cost. Loss may arise from the division of the power between the different ports, though components used for a Wilkinson splitter can be relatively low loss, especially when PCB transmission lines are used along with low-loss PCB substrate materials. Disadvantages of traditional Wilkinson splitters may include a reduction in frequency response. As the Wilkinson splitter is based around the use of quarter wave transmission lines, it has a limited bandwidth.
Described herein are apparatuses (systems and methods) that my address the issues raised above, and may take advantage of simple system of splitter/combiners (including chains of splitter/combiners) while enhancing performance, e.g., throughput, of the overall antenna apparatus.