ABSTRACT
A novel ultra-compact four-port multiple-input-multiple-output (MIMO) cylindrical dielectric resonator antenna (DRA) with improved isolation is proposed for WLAN applications in this paper. The antenna is originally radiated with the assistance of two different excitation mechanisms to generate decoupled orthogonal modes. To further diminish the coupling field and improve the isolation, a suitable U-shaped slot is created on the common ground plane. Two additional rectangular slits are also etched to adjust the impedance matching of other ports. To better reveal the operating mechanism of the decoupling scheme, the common mode (CM) and differential mode (DM) impedance analysis methods between DRA ports are presented. The etched U-shaped slot can tune the impedance of CM and DM to be consistent to realize the decoupling. The antenna is simulated, fabricated, and tested to verify the decoupling mechanism. The results demonstrate that the isolation between ports 1 and 2 is enhanced from 5 dB to 23 dB, and other ports exhibit low coupling of better than 12 dB. Moreover, the antenna with the full size of 30 × 30 × 8.1 mm3 can be used either as a four-port DRA with a bandwidth of 300 MHz or as a two-port DRA with a bandwidth of 700 MHz, at a center frequency of 5.6 GHz.
ABSTRACT
A novel compact tapered-slot-fed antenna (TSA) with anti-spiral shape and lumped resistors is presented for ultra-wideband (UWB) applications. Unique coplanar waveguide (CPW) to coplanar strip (CPS) feeding structure and exponential slot are designed to ensure the continuous current propagation and good impedance matching. With a pair of anti-spiral-shaped structure loadings at the end of the antenna, the radiation performance in lower operating band can be enhanced obviously. The typical resistor loading technique is applied to improve the time domain characteristics and expand the bandwidth. The fabricated prototype of this proposed antenna with a size of 53 × 63.5 mm2 was measured to confirm simulated results. The proposed antenna has S11 less than -10 dB in the range of 1.2-9.8 GHz, and the group delay result is only 0.4 ns. These findings indicate the proposed antenna can be taken as a promising candidate in UWB communication field.
