Multiple Points Fed Patch Filtennas With High Out-of-Band Suppression Levels

This paper proposes a series of multiple points fed (MPF) patch filtennas. The MPF patch has a single combined feed port. The signal passes through multiple parallel feed networks (FNs) and then is connected to the patch at discrete feed points. One notable technical feature of the MPF patches is that the discrete feed positions are critical to filtering characteristics, directly influencing the RNs in the frequency spectrum. Another characteristic of MPF is its scalability: additional FNs introduce more in-band transmission poles (TPs), aiming to provide higher out-of-band suppression levels. Accordingly, two-point fed (2PF), 3-point fed (3PF), and 4-point fed (4PF) patches were systematically designed and analyzed, together with their dual-port equivalent circuit models. The working principle of FN with a multi-path to the radiator is exhibited by analyzing the 2PF patches. A filtenna with dual RNs flanking the passband is realized by 3PF patch. It works in 5.65–6.01 GHz, which can cover the 5.725–5.85 GHz band of Wi-Fi 6. The finally designed 4PF filtenna has four TPs within the passband of 6.01–6.45 GHz and three RNs out-of-band. It is designed to target the lower half of the sub-7 GHz new frequency band. Both simulations and measurements indicate that the benefits brought by the multiple TPs include a favorable rectangular coefficient (0.22/0.38), and high out-of-band suppression levels in the 5G n79, Wi-Fi 6, and the new 6G communication band (54.35/45.24/37.97 dB from simulation, 37.41/37.51/37.97 dB from measurement).