a plurality of packet detection units, each packet detection unit corresponding to a time frequency code for detecting packets according to a preamble sequence of the time frequency code, each packet detection unit comprising:

a signal receiving end for receiving signals;

a series of delay units comprising a plurality of delay units connected in a sequence, each delay unit being utilized for delaying signals by a clock cycle, and a first delay unit in the plurality of delay units being coupled to the signal receiving end;

a matched filter coupled to the signal receiving end and the series of delay units for generating a matched value according to the preamble sequence, the signals received by the signal receiving end and a correlation value between the signals outputted by each delay unit;

a power meter coupled to the signal receiving end and the series of delay units for generating a total power value according to the signals received by the signal receiving end and power of the signals outputted by each delay unit; and

a division unit coupled to the matched filter and the power meter for calculating a correlation value of the matched value and the total power value;

a comparison unit for comparing the correlation values outputted by the division units of the plurality of packet detection units; and

a packet decision module for determining a timing position of the time frequency code and a fast Fourier transform sampling window for the packet received by the packet detection system according to the signal outputted by the packet detection system.