Fig. 1. Geometric relationship between diffractive primary mirror and focal length under focusing condition

Fig. 2. Phase variation curve of diffractive primary mirror when focal length is 20 m

Fig. 3. Continuous phase-shifting and corresponding beam patterns of primary mirror. (a) Continuous phase-shifting at center of primary mirror; (b) continuous phase-shifting near mirror edge of primary mirror; (c) beam pattern of 460 km near field; (d) enlargement of main lobe corresponding to Fig. 3(c); (e) beam pattern of far field; (f) enlargement of main lobe corresponding to Fig. 3(e)

Fig. 4. Phase-shifting and beam patterns of four quantization bits of primary mirror. (a) Phase-shifting of four quantization bits at center of primary mirror; (b) phase-shifting of four quantization bits near mirror edge of primary mirror; (c) beam pattern of 460 km near field; (d) enlargement of main lobe corresponding to Fig. 4(c); (e) beam pattern of far field; (f) enlargement of main lobe corresponding to Fig. 4(e)

Fig. 5. Pulse compression results of echo signal from different positions of diffractive primary mirror to focal point. (a) With aperture transition; (b) without aperture transition

Fig. 6. Pulse compression results of summed echo signals at focal point. (a) With aperture transition; (b) without aperture transition

Fig. 7. Echo signals. (a) Amplitude-frequency characteristic; (b) phase-frequency characteristic

Fig. 8. Matched filter functions. (a) Amplitude-frequency characteristic; (b) phase-frequency characteristic

Fig. 9. Characteristics of echo signals after matched filtering. (a) Amplitude-frequency characteristic; (b) phase-frequency characteristic; (c) time domain signal

Fig. 10. Echo signals after amplitude-frequency correction. (a) Amplitude-frequency characteristic; (b) phase-frequency characteristic; (c) time domain waveform

Fig. 11. Geometric relationship in ground-range direction

Fig. 12. Time domain echo signal after aperture transition compensation (without segmented compensation). (a) Target at down edge of beam; (b) target at center of beam; (c) target at upper edge of beam

Fig. 13. Time domain echo signal after aperture transition compensation (with segmented compensation). (a) Target at down edge of beam; (b) target at center of beam; (c) target at upper edge of beam