High scanning-rate periodic leak-wave antennas using complementary microstrip-slotline stubs

A series-fed patch (SFP) array leaky-wave antenna can realize the frequency scanning. To increase the scanning rate, we add complementary microstrip-slotline stubs between the patches. The complementary microstrip-slotline stub is an all-pass filter and its group delay is smooth and continuous, and it maintains a flat magnitude response within an ultra-wide bandwidth. It significantly increases the slope of phase versus frequency and hence the scanning rate when cascading with the series-fed patch leaky-wave antennas. Three examples are provided in comparison with the conventional one. The results show that the new leaky-wave antennas increase the scanning rate by 42%-72%.