Fig. 2 | Nature Communications

Fig. 2

From: Partially coherent radar unties range resolution from bandwidth limitations

Fig. 2

Illustration of the proposed detection method. The transmitted signal consists of a CW wave with a phase that is switched randomly every τm seconds, corresponding to opening a coherent window of length \({{c\tau }}_{{m}}\). If a target exists within the coherent window, the reflected signal will be delayed by time τ and can be divided into two parts—the first is of duration \(({{\tau }}_{{m}} - {{\tau }})\), which is correlated with the still transmitting signal (i.e., the same phase), the other part is of duration τ and is uncorrelated with the transmitting signal. By switching the phase N times and averaging the product of the reflected and transmitting signal over a window of length \({{N\tau }}_{{ m}}\), the cross-correlation Cm, which is the cross-correlation for coherence time interval τm, is measured. The cross-correlation averages to 0 if the target is not within the coherence length. For a target within the coherent window, however, the average increases as the target becomes closer. By increasing the coherent window and repeating the process, the cross-correlation as a function of coherence length can be obtained (see Fig. 3).

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