Focusing bistatic SAR data in frequency domain requires the two dimensional (2D) point target reference spectrum (PTRS). In this paper, a 2D PTRS is derived based on Loffeld’s bistatic formula (LBF). The spectrum in this paper combines the in uence of the Doppler centroids and frequency modulated rates of the transmitter and receiver on the total Doppler contributions. The essential of this paper is to model the Doppler contributions of the transmitter and the receiver using power series. It can be used in extreme bistatic (like hybrid spaceborne/airborne) and high squint (like bistatic forward-looking) cases. The accuracy of the PTRS is veri ed using numerical simulation of point target.