Broadside Radiation Equalization Through Mode Coupling Balancing in Periodic Leaky-Wave Antennas

Periodic leaky-wave antennas (P-LWAs) may be optimized by equalizing the resonance frequencies of the two radiation modes and their quality factors, i.e., by full-filling the frequency-balancing and Q-balancing conditions. These conditions may be achieved by introducing a proper amount of asymmetry in the unit cell of the P-LWA. This paper extends the previously reported circuital perspective to a full-wave electromagnetic perspective. Specifically, it shows that the required Q-balancing condition corresponds to complete coupling between the longitudinal and transverse modes, which leads to their perfect coalescence. Finally, it illustrates the theory by the numerical example of a series-fed patch (SFP) P-LWA.