M. Farhan Shafique

Compact UWB-MIMO antenna array with a novel decoupling structure

In this paper, a compact planar Ultra-Wideband (UWB) Multiple-input Multiple-output (MIMO) antenna array is proposed. This UWB-MIMO antenna array consists of two identical monopole antenna elements with a novel decoupling structure etched on the ground plane. The antenna performs very well over the UWB frequency range of 3.1-10.6 GHz. The decoupling structure improves the isolation between the antennas over the complete frequency band which can only be achieved otherwise by increasing the separation between the antenna elements. The analysis of antenna performance with and without stub is provided to demonstrate the significance of adding the decoupling stub to the design. The proposed compact and cost efficient antenna array system measures 27 × 47 mm2 only.

Mutual Coupling Reduction for High-Performance Densely Packed Patch Antenna Arrays on Finite Substrate

This paper reports on an effective mutual coupling suppression technique in which a metamaterial superstrate is placed in between the elements of densely packed microstrip phased array. Modified complementary split ring resonators are printed on the decoupling superstrate slab which caters for both surface and space wave effects. A detailed analysis of this proposed scheme is carried out on a low as well as on a high-permittivity substrate. Coupling suppression of 27 and 11 dB is achieved experimentally on the low- and high-permittivity substrates, respectively, with an element separation of λo/8. The design is compact and easy to realize and it removes drawback of poor front-to-back ratio previously reported in other decoupling techniques. In addition to high-coupling suppression, the decoupling slab can be added or removed in real time which makes this technique versatile for various applications having stringent performance requirements.

Performance Degradation of Cavity Backed Patch Antenna Due to Dielectric Coating and Its Improvement

The cavity backed patch antenna embedded in dielectric coated structure is presented. The patch antenna is backed by a substrate integrated cavity. The aperture of antenna is surrounded by a thick dielectric material which acts as dielectric coating and significantly deteriorates impedance matching and radiation pattern of antenna. The radiation pattern of antenna is severely degraded due to excitation of surface waves in the surrounding dielectric coating. The proposed electromagnetic bandgap (EBG) structure in the form of via less metallic patches is placed on the surrounding dielectric coating. The EBG structure reduces the propagation of surface waves in the dielectric coating causing improvement in the radiation pattern of antenna. The input impedance matching of antenna is also improved. The simulated results are in good agreement with experimental results.

Design of highly compact reconfigurable filters with tunable reactive loading

Abstract A compact and electronically tunable substrate integrated waveguide cavity resonator is presented in this work. The SIW cavity resonator is loaded symmetrically with stubs on the two sides which are terminated through varactors. By changing the capacitance along the loaded stubs the resonant frequency has been varied. Parametric analyses carried out in this work show a large potential tuning range along with the total resonator size of less than 3/4 λg. The resonator is created on a single layer printed circuit board with integrated biasing network. A two pole filter is realized using the tunable resonator and measured tuning bandwidth of 8.51% at center frequency of 2.55 GHz is demonstrated. The insertion loss is measured between 2.7 and 4.8 dB for the whole range and the return loss is less than 13.5 dB. The technique also allows the real-time fine tuning of coupling coefficient of the two resonators which can easily be extended to the realization of higher order filters. The proposed filter is an excellent candidate for miniaturized RF front-ends where tuning is essential for better spectrum control.

A single layer reflectarray with octagonal-ring delay line for X-band applications

In this paper, a low cost broadband single layer reflectarray is proposed for X-band applications. The proposed reflectarray consists of truncated circular patch coupled to octagonalring delay line. The unit element is optimized to work at X-band with the center frequency of 10 GHz. A broad reflection phase range of more than 600° is obtained by varying the length of delay line. The reflectarray is designed on a low cost FR-4 substrate having size of 0.5λo. A 15 × 15 elements reflectarray with F/D = 1 is simulated to obtain the radiation characteristics. The design achieves 20 dB gain, low side-lobe-levels and broad phase range.

Dual port UWB-MIMO antenna with ring decoupling structure

A miniaturized dual port multiple-input multiple-output (MIMO) antenna, operating in ultrawideband (UWB) frequency band communication is presented in this paper. The antenna elements are located in side-by-side configuration. The suggested antenna exhibits a good impedance match (VSWR ≤ 2) covering frequency band of 2.5 GHz-10.4 GHz, while exhibiting high isolation. A structure consisting of a strip line and a slotted circular ring at the center of ground plane is placed between both antenna elements to achieve enhanced isolation between antennas. The antenna design is realized on FR4 substrate. The antenna is compact with dimensions of 40mm×23 mm. The MIMO parameters like ECC, CCL and TARC are also analyzed and the results suggests that the proposed antenna design is appropriate candidate for the UWB-MIMO applications.

Dual port UWB diversity/MIMO antenna with dual band-notch characteristics

A compact two-port diversity/MIMO antenna with dual band-notch characteristics for ultra wideband (UWB) applications is presented in this paper. The antennas exhibit a good impedance match over frequency band of 3.1 GHz–12 GHz, while exhibiting high isolation. Enhanced isolation is achieved with a decoupling structure having circular slots. The decoupling structure provides isolation of more than 20 dB for whole UWB spectrum. By introducing U-shaped slot in the main radiator and horizontal stubs in ground plane, band-notch characteristic is achieved in proposed MIMO design. Two notches are achieved at 5.150–5.825 GHz (WLAN) and 7.25–7.75 GHz (downlink of X-band satellite). The antenna is miniaturized having dimensions of 22mm × 36mm. The results suggests that the proposed diversity/MIMO antenna design can be suitable for portable UWB applications.

A low-profile CPW-fed broadband antenna for WLAN and RFID applications

This paper presents a novel compact broadband circularly polarized slot antenna fed by a co-planar waveguide (CPW), suitable for use in WLAN and RFID applications. The antenna is only 20 × 24 mm in size. Measured impedance bandwidth (VSWR < 2) at center frequency of 5.8 GHz is 24% and the 3 dB axial-ratio (AR) bandwidth is 3.1%. The antenna has an omnidirectional radiation pattern with a maximum gain of −0.5 dB.