In this paper, a compact antenna design method is proposed for microstrip patch antennas using a double-layered defected ground structure (DGS) configuration. While a conventional single-layered defected ground structure yields a lower resonant frequency and Q-factor, a smaller circuit size can be achieved using an additional substrate with a higher dielectric constant. The size reduction obtained from the additional resonant LC elements is analytically explained using the equivalent circuit model. The characteristics of the additional substrates are investigated for various dielectric constants and thicknesses. From the experimental results, the proposed design method leads to a total size reduction of up to 51.7% and a miniaturized design for planar antennas with ground apertures. The proposed design method can be applied to various antenna designs with any DGS pattern. Furthermore, the size reduction method can maintain the structure of the resonant patch element and its radiation characteristics. Therefore, the proposed method is applicable to the design of microwave devices on microstrip-based configurations.

A new co-simulation method is proposed for active devices and electromagnetic resonant circuits at microwave frequency range. For the measured and extracted device parameters, three steps of equivalent circuit models are processed of the general, simplified, and EM RLC models. To overcome the limited lumped element simulation in an electromagnetic simulator, the simplified equivalent circuit model is established by mathematical computation. The co-simulation procedures are described and experimentally verified for commercial diodes. The application circuit is designed and implemented using the proposed co-simulation method. The experimental results verify that design using the proposed co-simulated method presented excellent agreement for a wideband frequency range of 0–4 GHz, compared with that using a conventional design method. The proposed co-simulation method can be applied to any commercial EM simulation tools without active model error.