BACKGROUND

Distributed antenna systems (DAS) are frequently used to improve wireless coverage provided by one or more base stations. A remote unit of a DAS typically handles multiple technologies and frequency bands by using active and passive components in a single construction. The remote unit includes or is coupled to one or more antennas and is also referred to as a remote antenna unit.

In previous designs for remote units of a DAS supporting multiple frequency bands, the remote unit assembly includes two or more customized duplexers and a combiner. These components are integrated into a single block to enable bi-directional wireless communications on multiple frequency bands using a single antenna system. The integrated blocks are generally designed and manufactured to meet individual customer requests. Modification of the blocks after manufacture is generally not feasible. If changes are desired for the remote unit after deployment (such as adding a frequency band) an entirely new integrated block is typically designed and manufactured. This increases the cost and time to market for the design. Further, if a component in the integrated block fails, it is often the case that the entire integrated block must be replaced.

SUMMARY

In some aspects, a modular filter system includes a front panel, a back panel, and a multiband combiner coupled to the front panel, wherein the multiband combiner includes an antenna connector and a plurality of filter connectors. The modular filter further includes a plurality of filter modules separate from the multiband combiner. Each filter module of the plurality of filter modules includes a first connector to pass a first frequency band, a second connector to pass a second frequency band, and a combiner connector to pass the first frequency band and the second frequency band. Each filter module of the plurality of filter modules is configured to duplex, combine, or split first signals in the first frequency band and second signals in the second frequency band. The combiner connector of each filter module of the plurality of filter modules is coupled to a respective filter connector of the plurality of filter connectors using a respective cable. The modular filter system further includes a fixing system that includes a plurality of bars and a plurality of plates, wherein the plurality of bars is coupled to the front panel and the back panel using fasteners, wherein the plurality of bars and the plurality of plates are configured to secure the plurality of filter modules between the combiner and the back panel.

