Flexible printed two-element antenna array with enhanced isolation performance

A 3D compact antenna array printed on package was proposed for RF powered battery-less device operating at 900MHz. The array-integrated package has size of 33 mm by 56 mm by 12 mm, whose largest dimension is only 0.2λ at 900 MHz. Each radiating element is connected to a circuitry on PCB through inductive coupling and hence no direct electrical contact between PCB and the package is needed, which greatly simplifies the assembly process. An isolation structure is added to minimize the coupling between closely spaced array elements. The prototype was fabricated by printing the antenna array on 0.1 mm thick PET sheet and by folding the sheet into a rectangular package. A maximum isolation of 30 dB between the two array elements was demonstrated for the proposed design. The measured radiation pattern also reveals the importance of the isolation component. It shows maximum gain of 1.1 dBi and 0.7 dBi is achieved for each array element of the proposed design, which is significantly higher than that of the reference design without any isolation.