The purpose of this letter is to introduce a compact ultrawideband (UWB) diversity antenna with a very low envelope correlation coefficient (ECC). The design employs a hybrid isolation enhancing and miniaturization technique. The antenna consists of two counter facing monopoles, and is miniaturized by using not only inverted-L stubs but also a complementary split-ring resonator (CSRR) on the ground plane. The added components enhance isolation and enable tighter packing of the antennas. The result is a very compact multiple-input-multiple-output (MIMO) array with an overall size of 23 × 29 mm ² , which covers the entire UWB spectrum from 3 to 12 GHz, with mutual coupling lower than -15 dB. Moreover, the CSRR unit that acts as a resonator is applied for the first time to suppress the interference of RF currents flowing through the ground plane of this UWB-MIMO/diversity antenna. The performance of the fabricated prototype in terms of scattering parameters, broadside (peak) gain, radiation patterns, efficiency, and ECC is presented and discussed.

The system design of an integrated microwave imaging radar for the diagnostic screening of breasts cancer is presented. A custom integrated circuit implemented in a 65-nm CMOS technology and a pair of patch antennas realized on a planar laminate are proposed as the basic module of the imaging antenna array. The radar operates on the broad frequency range from 2 to 16 GHz with a dynamic range of 107 dB. Imaging experiments carried out on a realistic breast phantom show that the system is capable of detecting tumor targets with a resolution of 3 mm.

A compact planar ultra‐wideband (UWB) multiple‐input–multiple‐output antenna array with two radiating elements is proposed in this work. Elements separation is kept at 5.5 mm and the isolation is achieved with a floating parasitic decoupling structure not known for UWB diversity antennas previously. The antenna system performs very well over the entire UWB frequency range of 3.1–10.6 GHz. The mutual coupling between the radiating elements is below −20 dB in most of the band. The decoupling structure is investigated in detail and the diversity analysis of the antenna in Rayleigh fading environment for indoor and outdoor propagations is also presented by computing envelope correlation coefficients. The proposed antenna array measures 33 × 45.5 mm ² only and it is suitable for handheld devices, personal digital assistant (PDA)s, next generation home entertainment systems and robots.

An ultra‐compact dual‐polarised ultra‐wideband multi‐input multi‐output antenna made with a single‐shared‐radiating element and two meandered feeding lines are proposed. Miniaturisation is achieved by using a combination of techniques, including a resonant stub connected to the ground through which shorts the excessive coupled energy before it reaches the other port and minimises coupling, slots etched in the radiator that also help minimise mutual coupling, while the meandered lines allow to bring the antenna closer to the greatly reduce the overall size of the antenna. Slots etched in the radiator and the use of a stub connected to the ground through, help to minimise the mutual coupling. The formation of orthogonal surface currents provides the necessary dual polarisation. Simulated and measured results demonstrate the wideband impedance matching, low mutual coupling and low envelope correlation coefficient. This antenna has an extremely compact size (22 × 24.3 mm ² , including the ground plane) that makes it an excellent candidate for portable and handheld devices.

A compact planar UWB‐MIMO antenna array with WLAN band rejection is presented. The array consists of four monopole radiators and a common ground plane. These monopoles are placed in such a way that the polarisation diversity of nearly placed radiators is exploited, resulting in high isolation. The proposed MIMO antenna array is electrically small (50 × 39.8 mm ² ), printed on a low loss 1.524 mm thick Rogers TMM4 laminate with a dielectric constant of 4.5 and a loss tangent of 0.002. A band‐stop design was inserted on the ground plane to behave similar to a LC band‐stop filter and reject the WLAN band. Simulation and measurement results satisfy the return loss requirement of better than 10 dB and isolation better than 17 dB over the entire 2.7–5.1 and 5.9–12 GHz bandwidths.