In most of the papers, authors have not given H-plane patterns of Vivaldi antennas rather all explained E-plane patterns. Is there any need to show H-plane patterns or E-plane patterns are sufficient.
In the far field in space , the electromagnetic waves are transverse ellectromagnetic in the sense E and H are perpendicular and their plane is normal to the propagation direction. Also there is a relation ship between H and E such that H= E/za , where Za is the air impedance Za= sqr (mu0/epsilon0)
So as you see if E is known one can get H as Za is known
Please refer to the site: https://en.wikipedia.org/wiki/Impedance_of_free_space