Determining distance to source of passive intermodulation product (pim) in a distributed base station

Abstract

A method for determining the distance to source of a passive intermodulation (PIM) product for a distributed base station is provided. The method includes generating a test signal; transmitting the test signal on a front haul communication link between a baseband unit and a remote radio head of the distributed base station; receiving the PIM product as a reflected signal at the remote radio head; multiplying the reflected signal by a conjugate of the test signal to create a sinewave; determining a frequency of the sinewave; and determining the distance to the source of the PIM based on the determined frequency of the sinewave.

1 . A method for determining the distance to a source of a passive intermodulation (PIM) product for a distributed base station, the method comprising:
 transmitting a plurality of test signals on a front haul communication link between a baseband unit and a remote radio head of the distributed base station;   determining a relative timing for the PIM product;   determining a relative timing of a signal path internal to the remote radio head; and   determining the distance to the source of the PIM product based on the relative timing of the PIM product and the relative timing of an internal signal path of the distributed base station.   
     
     
         2 . The method of  claim 1 , and further comprising varying the signal level of the plurality of test signals when the remote radio head implements a low sampling rate. 
     
     
         3 . The method of  claim 1 , wherein varying the signal level of the plurality of test signals comprises:
 transmitting a plurality of first test signals at a first level to determine the relative timing of the PIM product; and   transmitting a plurality of second test signals at a second, higher level to determine the relative timing of the signal path internal to the remote radio head by inducing an intermodulation (IM) signal.   
     
     
         4 . The method of  claim 2 , wherein the low sampling rate has a sampling rate is below 24 MHz. 
     
     
         5 . The method of  claim 1 , wherein transmitting a plurality of test signal comprises transmitting a chirp signal and a continuous wave (CW) signal. 
     
     
         6 . A method for determining the distance to a source of a passive intermodulation (PIM) product for a distributed base station, the method comprising:
 transmitting at least one first test signal on a front haul communication link between a baseband unit and a remote radio head of the distributed base station;   determining a coarse timing for the PIM product based on a reflection of the at least one first test signal;   transmitting at least one second test signal on the front haul communication link at a power level that does not saturate circuitry in the remote radio head;   determining a relative timing for the PIM product based on a reflection of the at least one second test signal;   transmitting at least one third test signal on the front haul communication link at a power level that causes at least some circuitry of the remote radio head to saturate;   determining a relative timing of an intermodulation (IM) product based on the IM product caused by the at least one third test signal; and   determining the distance to the source of the PIM product based on the coarse timing, the relative timing for the PIM product and the relative timing for the IM product.   
     
     
         7 . The method of  claim 6 , wherein transmitting at least one first test signal comprises transmitting a chirp and a continuous wave (CW) signal. 
     
     
         8 . The method of  claim 7 , wherein transmitting the at least one second test signal comprises transmitting the at least one second test signal at a level that is less than a level of the at least one third test signal. 
     
     
         9 . The method of  claim 6 , wherein determining a relative timing of the IM product comprises applying a canceler or DC blocker to eliminate the PIM product to enable determination of the relative timing of the IM product. 
     
     
         10 . A method for determining the distance to a source of a passive intermodulation (PIM) product for a distributed base station, the method comprising:
 transmitting at least one first test signal on a front haul communication link between a baseband unit and a remote radio head of the distributed base station;   determining a coarse timing for the PIM product based on a reflection of the at least one first test signal;   transmitting at least one second test signal on the front haul communication link;   determining a relative timing for the PIM product based on a reflection of the at least one second test signal;   transmitting at least one third test signal on the front haul communication link at a power level that causes at least some circuitry of the remote radio head to saturate;   determining a relative timing of an intermodulation (IM) product based on the IM product caused by the at least one third test signal; and   determining the distance to the source of the PIM product based on the coarse timing, the relative timing for the PIM product and the relative timing for the IM product.   
     
     
         11 . The method of  claim 10 , wherein transmitting at least one first test signal comprises transmitting a chirp and a continuous wave (CW) signal. 
     
     
         12 . The method of  claim 11 , wherein transmitting the at least one second test signal comprises transmitting the at least one second test signal at a level that is less than a level of the at least one third test signal. 
     
     
         13 . The method of  claim 10 , wherein determining a relative timing of the IM product comprises applying a canceler or DC blocker to eliminate the PIM product to enable determination of the relative timing of the IM product.