3-D-Corrugated Ground Structure: A Microstrip Antenna Miniaturization Technique

A 3-D-corrugated ground structure is proposed as miniaturization technique for microstrip antennas and applied to wearable antennas. The corrugated ground structure in a textile embodiment is realized by folding the full ground plane to locally raise it underneath each of the two radiating edges of a microstrip antenna. The corrugated structure introduces additional reactive loading, which slows the wave propagation. This makes the antenna appear electrically longer and consequently reduces the resonance frequency. The technique is applied to a basic microstrip antenna operating at 8 GHz. The use of corrugation heights of 3.2 and 4.0 mm on a 4.8 mm thick substrate results in a reduction of the resonance frequency by 2.2 and 3.5 GHz, resulting in antenna miniaturization of 27.5% and 43.8%, respectively. Importantly, this technique does not lead to significant reduction in the antenna operation bandwidth. The proposed method is straightforward to apply and can be realized with a standard fabrication process. It can be in principle applied to any existing microstrip antenna with a full ground plane. Moreover, the proposed method preserves the original shape of the radiator, avoiding significant changes in radiation performance and reducing the cross-polarization level—qualities desirable for wireless communications. The miniaturized textile antenna with corrugation height of 3.2 mm demonstrated here operates at the industrial, scientific, and medical (ISM) band of 5.8 GHz and is suitable for wireless body area network (WBAN) applications.