Electrical engineering

Physics

Band-pass filter

Topology (electrical circuits)

Optics

Engineering

Coupling (piping)

Metallurgy

Materials science

Computer science

Phase (matter)

Quantum mechanics

X band

IEEE Transactions on Antennas and Propagation

Compact, low-profile, linearly polarized (LP), and circularly polarized (CP) patch-based filtennas are realized with a custom-designed coupling probe. It introduces a deep null at both the lower and upper band edges of the filter response. These two nulls facilitate a quasi-elliptic bandpass behavior and can be independently controlled to achieve sharp band-edge skirts and high out-of-band suppression levels. The CP version evolves from the LP design by introducing a T-shaped nearfield resonant parasitic (NFRP) element near the probe to create two transmission paths with an inherent 90° phase difference. Its presence facilitates the simultaneous excitation of the TM 10 and TM 01 modes of the patch without the need for any power divider or phase delay line, reducing the design complexity and lowering the insertion loss. Prototypes were fabricated, assembled, and tested. The measured results agree well with their simulated values. They are low profile (0.03 λ 0 height) and compact in size (0.04 λ 0 2 footprint). The LP and CP prototypes exhibit, respectively, a -10-dB fractional impedance bandwidth of 7% and an overlapping axial ratio fractional bandwidth of 4.5%. Excellent measured performance characteristics are demonstrated, including flat passband realized gain values and filter responses with sharp roll-off rates and high out-of-band suppression levels.

Compact, Low-Profile, Linearly and Circularly Polarized Filtennas Enabled With Custom-Designed Feed-Probe Structures