  A periodic leaky-wave antenna (LWA) with tuning capability and enhanced
scanning sensitivity is introduced in this paper. This antenna leverages the
concept of active Gain-Loss C-section pairs to tune the group delay of each
antenna unit cell without affecting its magnitude response. This in turn
changes the scanning angle versus frequency rate in the periodic LWA. The
proposed concept is well-suited for the application to real-time spectrum
analysis, where it allows the frequency resolution to be tuned or significantly
enhanced even with a low-permittivity substrate.
