A radar liquid level measuring apparatus (10) includes a first oscillation module (102), a second oscillation module (104), a frequency comparator (106) and a control module (107). The first oscillation module (102) has a first oscillation frequency. The first oscillation module (102) generates a first pulse signal (10202). The second oscillation module (104) has a second oscillation frequency. The second oscillation module (104) generates a second pulse signal (10402). The frequency comparator (106) converts the first pulse signal (10202) and the second pulse signal (10402) into an adjusted signal (10602). The control module (107) compares the adjusted signal (10602) with an expectation value (10818) to obtain a comparative result signal. According to the comparative result signal, the control module (107) adjusts the second oscillation frequency, so that the second oscillation frequency and the first oscillation frequency have a constant frequency difference.
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