Abstract: The transmit signal model and receive signal model of multiple-carrier frequency MIMO radars are constructed first.Then the multiple-dimensional ambiguity functions(AF) of MIMO radars with the array aperture are derived based on the theory of matched filter and are simplified using the orthogonal characteristics between the transmit signals of MIMO radars.And the AF can be further factored into separable space and time components when the target appears in the far-field of the array and the waveforms are considered as narrowband.The range resolution is commonly decided by the bandwidth of the transmit signal and the bandwidth among the transmit antennas simultaneously.Take an uniform linear array(ULA) as an example,the characteristics of AF and the resolution of LFM signal using multiple carrier frequency are analyzed in the case of monostatic and bistatic radars.And the range and azimuth resolution change with the difference of the target’s position for a bistatic MIMO radar.