RECEPTION DEVICE FOR CAR NAVIGATION DEVICE AND ITS FREQUENCY SWITCHING METHOD

摘要

PROBLEM TO BE SOLVED: To effectively use road traffic information supplied from an information broadcast station by comparing the information sizes of respective reception frequencies and switching the detection frequency of a reception means into the reception frequency of the largest information size. SOLUTION: An information size update part 8 and an update history processing part 9 calculate the size of a data block stored in DRAM 5, generate the information size table of respective frequencies and respective mesh codes and store/update it in SRAM 6. When an error rate exceeds a thresholdεfor prescribed time in an error rate comparison/switching part 12 and a switching judgment part 13, the detection frequency of a PLL frequency demodulator 3 is switched to the frequency of an FM broadcast station which is adjacent to a selected FM broadcast station and whose error rate is the smallest. An information size comparison switching part 11 and the switching judgment part 13 compare the information sizes of the respective frequencies of a mesh area to which the present position of a self-vehicle belongs and the detection frequency of the PLL frequency demodulator 3 is switched to the frequency of the largest information size.