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Code acquisition device and method using two-step search process in DS-CDMA UWB modem

  • US 20060093021A1
  • Filed: 02/24/2005
  • Published: 05/04/2006
  • Est. Priority Date: 11/03/2004
  • Status: Active Grant
First Claim
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1. A code acquisition device using a two-step search process in a Direct Sequence-Code Division Multiple Access (DS-CDMA) Ultra Wide Band (UWB) modem, the device comprising:

  • an I/Q channel symbol generating unit for, in a first search process, generating a plurality (i) of nth I/Q channel symbols (YI,n(i), YQ,n(i)) consistent with a plurality (i) of code phases for a multi-path reception signal (r(t)) by using six spread code sequences, and in a second search process, generating a plurality of nth I/Q channel symbols (YI,n(i), YQ,n(i)) consistent with a plurality (i) of code phases for the multi-path reception signal (r(t)) by using a spread code having a maximal value among six spread codes acquired in the first search process;

    a spread code selecting unit for, in the first search process, receiving the plurality of nth I/Q channel symbols (YI,n(i), YQ,n(i)) from the I/Q channel symbol generating unit to respectively combine the received channel symbols (YI,n(i), YQ,n(i)) at NNC1 times, and summing the combined result value (Zi) at each of the six spread codes to generate six symbol energies (Em, m=1,2, . . . ,

         6) consistent with the six spread codes, and deciding the spread code having the maximal value among the six symbol energies (Em, m=1,2, . . . ,

         6), as a spread code of a piconet coordinator;

    an NNC2NS tap I/Q channel symbol matched filter unit having an Ns-length tap and for, in the second search process, receiving the plurality (i) of nth I/Q channel symbols (YI,n(i), YQ,n(i)) from the I/Q channel symbol generating unit to generate a result value (Sn,k(i)) through a predetermined arithmetic operation, and performing a noncoherent combining to the result value (Sn,k(i)) at NNC2 times to output an arbitrary result value (Xn(i));

    a switching unit disposed between the I/Q channel symbol generating unit and the NNC2NS tap I/Q channel symbol matched filter unit, for changing an opened state of the first search process to a closed state of the second search process to connect the I/Q channel symbol generating unit with the NNC2NS tap I/Q channel symbol matched filter unit; and

    a super frame and symbol boundary time deciding unit for deciding a super frame time (packet synchronization) and a symbol boundary time (firstly received path) by using the output values (Xn(i)) of the plurality of NNC2NS tap I/Q channel symbol matched filters in the second search process.

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