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In this paper, the space-and-time structure of the output signal of the antenna array (AA) of a chirp pulse radar is investigated in dependence on the frequency sweep range of the probe signal. Expressions are derived for calculating the output signals of the AA of a chirp pulse radar after optimal filtering in the case of beamforming using phase shifters and/or time-delay lines. Distortions of the space-time power pattern pertaining to the phase scanning method are analyzed in dependence on the frequency chirp range and scan angle. It is shown that these distortions are similar to the effects observed in the case of using taper windows for sidelobe suppression in the time and space (angular) domains. Based on the results obtained an applicability condition is suggested for the phase scanning in AAs of chirp pulse radars. It is shown that minor violations of this condition result in decreasing the amplitude and broadening of the main lobe and sidelobes in the AA space-time power pattern. In the case of strong violations of the applicability condition for the phase scanning the sidelobes of the angular directional pattern degrade, merging with the main one into a single quite broad maximum. The considered effects lead to deterioration of the range and azimuth resolution capabilities of radars and should be taken into account when selecting the taper window parameters.