Reducing leaked downlink interference signals in a remote unit uplink path(s) in a distributed antenna system (das)

Abstract

Methods and systems for reducing leaked downlink interference signals in a remote unit uplink path(s) in a distributed antenna system (DAS) are provided. In a remote antenna unit (RAU) disclosed herein, a downlink interference signal may be leaked from a downlink path to an uplink path in the RAU. In this regard, an adjustment circuit is provided in the downlink path of the RAU to suppress the downlink interference signal. A control system is provided in the DAS to monitor the leaked downlink interference signal and control the adjustment circuit in the RAU to minimize the leaked downlink interference signal in the uplink path. By providing the adjustment circuit in the RAU and the control system in the DAS to minimize the leaked downlink interference signal in the uplink path, it is possible to reduce interferences between downlink and uplink communications signals without increasing costs of the RAU.

What is claimed is: 
     
         1 . A remote unit in a wireless communications system, comprising:
 a coupling device coupled to a downlink path and an uplink path, the coupling device configured to:
 receive a downlink signal from the downlink path and provide the downlink signal to an antenna, wherein the downlink signal comprises at least one downlink communications signal and at least one downlink interference signal; and 
 provide an uplink signal to the uplink path, wherein the uplink signal comprises an uplink communications signal received from the antenna and the at least one downlink interference signal leaked from the downlink path to the uplink path; 
   an adjustment circuit comprising a local controller communicatively coupled to a process controller in an interference reduction control system, the local controller configured to suppress the at least one downlink interference signal in the downlink signal based on an adjustment control signal received from the interference reduction control system that is communicatively coupled to the adjustment circuit; and   a first downlink signal amplifier and a second downlink signal amplifier disposed according to a serial arrangement in the downlink path before the coupling device, wherein   the adjustment circuit comprises an adjustable matching circuit disposed between the first downlink signal amplifier and the second downlink signal amplifier.   
     
     
         2 . The remote unit of  claim 1 , wherein the adjustable matching circuit comprises a capacitor circuit disposed between the first downlink signal amplifier and the second downlink signal amplifier, the capacitor circuit comprising a capacitor and an adjustable capacitor disposed in a parallel arrangement. 
     
     
         3 . The remote unit of  claim 2 , further comprising a switch disposed between the coupling device and the antenna, wherein the switch is controlled by the local controller to couple the coupling device to the antenna or decouple the coupling device from the antenna. 
     
     
         4 . The remote unit of  claim 2 , further comprising at least one optical-to-electrical converter configured to convert the downlink signal to an electrical signal. 
     
     
         5 . The remote unit of  claim 4 , wherein the adjustable matching circuit further comprises an inductor comprising a first end coupled to the first downlink signal amplifier before the capacitor circuit and a second end coupled to a ground. 
     
     
         6 . The remote unit of  claim 5 , wherein the local controller is configured to set the adjustable capacitor to a capacitance value among a plurality of capacitance values of the adjustable capacitor in response to receiving an adjustment control signal indicative of matching circuit adjustment, wherein the capacitance value is different from a present capacitance value of the adjustable capacitor. 
     
     
         7 . The remote unit of  claim 6 , wherein the local controller is configured to store the present capacitance value of the adjustable capacitor as a preferred capacitance value in a local storage media in response to receiving an adjustment control signal indicative of matching circuit settlement. 
     
     
         8 . The remote unit of  claim 7 , wherein the local controller is further configured to configure an remote unit for an operating mode operation by controlling the switch to couple the coupling device to the antenna. 
     
     
         9 . The remote unit of  claim 8 , wherein the local controller is further configured to configure a remote unit for a commissioning mode operation by controlling the switch to decouple the coupling device from the antenna. 
     
     
         10 . The remote unit of  claim 7 , wherein the local controller is further configured to configure a remote unit for a commissioning mode operation by controlling the switch to decouple the coupling device from the antenna. 
     
     
         11 . The remote unit of  claim 1 , further comprising at least one optical-to-electrical converter configured to convert the downlink signal to an electrical signal, and at least one electrical-to-optical converter. 
     
     
         12 . The remote unit of  claim 11 , further comprising a switch disposed between the coupling device and the antenna, wherein the switch is controlled by the local controller to couple the coupling device to the antenna or decouple the coupling device from the antenna. 
     
     
         13 . The remote unit of  claim 12 , wherein the local controller is further configured to configure a remote unit for a commissioning mode operation by controlling the switch to decouple the coupling device from the antenna. 
     
     
         14 . The remote unit of  claim 13 , wherein the adjustable matching circuit comprises a capacitor circuit disposed between the first downlink signal amplifier and the second downlink signal amplifier, the capacitor circuit comprising a capacitor and a capacitor disposed in a parallel arrangement. 
     
     
         15 . The remote unit of  claim 12 , wherein the local controller is further configured to configure a remote unit for a commissioning mode operation by controlling the switch to decouple the coupling device from the antenna. 
     
     
         16 . The remote unit of  claim 15 , wherein the adjustable matching circuit comprises a capacitor circuit disposed between the first downlink signal amplifier and the second downlink signal amplifier, the capacitor circuit comprising a capacitor and a capacitor disposed in a parallel arrangement. 
     
     
         17 . The remote unit of  claim 12 , wherein the adjustable matching circuit comprises a capacitor circuit disposed between the first downlink signal amplifier and the second downlink signal amplifier, the capacitor circuit comprising a capacitor and a capacitor disposed in a parallel arrangement.