This paper proposes a new transmitted-reference (TR) FMCW-UWB radar for use as a gasoline tank level gauge. We analyze coherent receivers with emphasis on unwanted frequencies such as Doppler frequencies. The proposed TR-FMCW-UWB radar is composed of an FFT block a delay block a multiplier, and an integrator block The system model is verified through analysis and simulation. Degradation of detection performance occurs in the coherent receiver, in contrast to the proposed radar. The proposed receiver requires about 1dB more SNR than the ideal coherent receiver at the PD of 0.5. However, the performance of the coherent receiver has an effect on unwanted frequency. For PD of 0.5, the coherent receiver requires a higher SNR than does the proposed receiver when the unwanted frequency is 140 Hz.