| 摘要 |
PURPOSE: A fast code searcher is provided to perform energy searching processes relating to many pseudo-noise(PN) virtual hypotheses by a one-time energy calculation, and to perform a detailed serial searching process when the searched PN virtual hypotheses have big energies, so as to easily carry out a fast code searching process. CONSTITUTION: A decimator(11) inputs an in-phase(I) signal, a quadrature-phase(Q) signal, and an output of a pseudo-noise(PN) generator(18), and selects a PN period. A parallel correlator(12) inputs an output of the decimator(11) and a signal of the PN generator(18) to perform a parallel searching process, and carries out a correlation process to supply correlations relating to many PN virtual hypotheses. An accumulator(13) accumulates the correlations to supply the accumulated correlations. An energy calculator(14) inputs the accumulated correlations to convert the correlations into energies of the I signal/the Q signal, and supplies the converted correlations. A threshold energy examiner(15) inputs the converted energies to examine the converted energies with a threshold energy. A non-coherent accumulator(16) inputs the energies of the accumulated correlations to accumulate the inputted energies with predetermined frequencies. If the energies calculated from the energy examiner(15) is smaller than the threshold energy, a searching window controller(17) directs a moving command to the PN generator(18) and repeatedly progresses relating to a virtual hypothesis. If an output of the energy calculator(14) is bigger than the threshold energy, the controller(17) converts a parallel virtual hypothesis searching mode into a serial searching mode, and repeatedly performs from the process of accumulating the correlations to a process of selecting a highest energy relating to individual PN virtual hypotheses. A highest energy detector(19) inputs the accumulated values from the non-coherent accumulator(16) to arrange the correlations according to highest energy-possessing rates, and detects the highest energy. |
