The Flexible RF Technology Research Center's paper "A Strain-Insensitive Stretchable and Flexible Wideband Vivaldi Endfire Filtenna" published in the journal IEEE Transactions on Microwave Theory and Techniques

In 2025, the Flexible Radio Frequency Technology Research Center of Southeast University published a research paper entitled "A Strain-Insensitive Stretchable and Flexible Wideband Vivaldi Endfire Filtenna" in the journal IEEE Transactions on Microwave Theory and Techniques (impact factor: 4.5). The following is a detailed introduction.

Broadband radio features wide bandwidth, low power spectrum, high data rate, good phase linearity, and good radiation performance. It is extremely useful for high-data-rate transmission in applications such as high-precision radar, sensor data acquisition, imaging, and indoor positioning systems.

Current research on flexible broadband antennas focuses only on their bendability. However, in fields such as wearable devices, it is inevitable to consider the antenna's performance under stretching conditions. Research in this area, both domestically and internationally, still has some shortcomings. How to achieve low profile and stretchability of broadband antennas is an urgent problem to be solved.

Against this background, this study proposes a stretchable broadband Vivaldi filter antenna based on a serpentine-loaded substrate integrated dual plasma waveguide (S-SIDPW). By utilizing the unique electromagnetic propagation modes of the substrate integrated waveguide and SSPP, the filter achieves bandpass characteristics. Dispersion curve analysis shows that the cutoff frequency can be independently controlled by these two structures. Periodic grooves are etched on the SIW surface to form SSPP modes, which are then combined with a serpentine interconnect via an "island-bridge" mechanism. The equivalent medium parameters of the S-SIW are extracted using a transmission-reflection method, demonstrating that the serpentine microstructure extends the surface current path, thereby enhancing the slow-wave effect. Therefore, the lateral dimension is effectively reduced. To balance the tradeoff between stretchability and impedance matching stability, an innovative activation strategy is proposed, placing the stretchable microstructure in a deformation-insensitive region while retaining the non-stretchable characteristics of the sensitive region. Thanks to the unique electromagnetic transmission mode and specialized structural design of the hybrid SSPP/SIW design, the fabricated stretchable filter antenna maintains relatively stable RF performance in the operating frequency band (4-6 GHz) under various deformation conditions, demonstrating the application potential of the proposed filter antenna in stretchable electronic systems.

Figure 1 Integrated dual plasma waveguide (S-SIDPW) based on a serpentine-loaded substrate

Paper Information

[1] Z.-H. Chen et al., “A Strain-Insensitive Stretchable and Flexible Wideband Vivaldi Endfire Filtenna,” IEEE Trans. Microwave Theory Techn., pp. 1–12, 2025.