  A low cross-polarization periodic-slotted ridged substrate-integrated
waveguide (RSIW) leaky wave antenna (LWA) array is presented. Parametric
constraints of the structure were investigated to realize a periodic leaky wave
antenna (PLWA) with the ability of scanning from backward endfire into the
forward quadrant. An appropriate multimode transverse equivalent network (TEN)
is presented for the proposed antenna and values of leakage rate and phase
constant for different parameters of the structure were extracted using the
transverse resonance technique (TRT). The obtained results were compared to
those achieved from HFSS software simulations. The open stopband in the
broadside is eliminated using certain dimensions for the structure. By
simultaneously manipulating a number of parameters, a variable {\alpha} and
constant \b{eta} are resulted so that the desired sidelobe level (SLL) can be
realized. The proposed structure was simulated and then manufactured.
Simulation results show good agreement with measurement results.
