  A periodic long slot leaky-wave antenna (LWA) based on a ridged substrate
integrated waveguide (RSIW) is proposed. To reduce the cross polarization, the
long slot is placed on the SIW centerline, and a sinusoidal ridge is used to
produce a controllable asymmetric electric field around the long slot. Also,
only a small stopband occurs when the beam is scanned through the broadside.
Varying the amplitude and width of the sinusoidal ridge provides a fixed phase
constant and controllable leakage rate to achieve the desired sidelobe level of
less than 30 dB. Measurement results are consistent with the simulation
results.
