Broadband sub-array decoupling for tightly coupled arrays to radiate ultrawideband pulses based on surface-wave-induced absorption method

In this article, a broadband sub-array decoupling method based on a surface-wave-induced absorption mechanism is proposed to enable the compact design of two-dimensional (2D) tightly coupled arrays (TCAs) for the radiation of ultrawideband (UWB) pulses. Decoupling of UWB pulsed antenna arrays is more complicated than that of conventional narrowband arrays, since the mutual coupling itself occurs over a rather broad frequency range. Moreover, for a UWB pulse radiation system, significant gain loss within the decoupling band is undesirable, because it should maintain high waveform fidelity in the radiation fields. Thus, the mutual coupling mechanism between subarrays in the 2D TCA should be studied, and novel decoupling methods should be proposed. It indicates that the sub-array mutual coupling is caused by the surface wave between them, whose polarization direction is along the sub-array axis. Therefore, a resistive decoupling chain (RDC) is arranged along the sub-array direction between them to induce and absorb the coupling energy through the metal leads and the resistors, respectively. The former act as receiving antennas, while the latter act as loads. Therefore, the isolation between the subarrays and the bandwidth of the 2D TCA is improved. Finally, a 4 × 8-element TCA loaded with RDC is developed, and the sub-array mutual coupling is significantly reduced. The operating bandwidth of the developed TCA has been extended to 0.35-3.93 GHz. In terms of the time-domain performance, the pulse fidelity of the radiating fields after loading the RDC reaches 0.998. Moreover, the measured effective potential of the developed TCA with RDC is 4.61 kV, and the effective potential gain is 1.44, which is almost the same as that without RDC. It demonstrates that the proposed RDC can achieve broadband decoupling without noticeable loss in both frequency- and time-domain gains for the radiation of UWB pulses, compared with the existing decoupling methods.