Highly Efficient Impulse-Radio Ultra-Wideband Cavity-Backed Slot Antenna in Stacked Air-Filled Substrate Integrated Waveguide Technology

Abstract

An Impulse-Radio Ultra-Wideband (IR-UWB) cavitybacked slot antenna covering the [5.9803; 6.9989] GHz frequency band of the IEEE 802.15.4a-2011 standard is designed and implemented in airfilled substrate-integrated-waveguide (AFSIW) technology for localization applications with an accuracy of at least 3 cm. By relying on both frequency-and time-domain optimization, the antenna achieves excellent IR-UWB characteristics. In free-space conditions, an impedance bandwidth of 1.92 GHz (or 29.4%), a total efficiency higher than 89%, a front-to-back-ratio of at least 12.1 dB and a gain higher than 6.3 dBi are measured in the frequency domain. Furthermore, a system fidelity factor larger than 98% and a relative group delay smaller than 100 ps are measured in the time domain within the 3dB-beamwidth of the antenna. As a result, the measured time-of-arrival of a transmitted Gaussian pulse, for different angles of arrival, exhibits variations smaller than 100 ps, corresponding to a maximum distance estimation error of 3 cm. Additionally, the antenna is validated in a real-life worst-case deployment scenario, showing that its characteristics remain stable in a large variety of deployment scenarios. Finally, the difference in frequency-domain and time-domain performance is studied between the antenna implemented in AFSIW and in dielectric-filled SIW (DFSIW) technology. We conclude that DFSIW technology is less suitable for the envisaged precision IR-UWB localization application. Index Terms-Cavity-backed slot antenna, air-filled substrateintegrated-waveguide, impulse-radio ultra-wideband, high efficiency, indoor localization.

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“…In [8], the cavity-backed slot antenna is implemented in AFSIW technology. The advantages of the conventional cavity-backed slot antenna, including a high gain, FTBR, and radiation efficiency are retained, while achieving a planar, low profile antenna.…”

“…This radiating slot has a length comparable to that of the SIW cavity, thereby splitting the cavity into two coupled sub-cavities. By letting both coupled sub-cavities resonate at a different frequency, a considerable impedance bandwidth is achieved [8]. The application of an air substrate further increases the impedance bandwidth and maximizes the radiation efficiency, at the cost of a slight increase in physical dimensions.…”

“…The waveguide is formed by covering the edge-plated cavity on both sides with a conducting layer to form the top and bottom walls. Accurate alignment is ensured by using alignment holes, while electrical contact is achieved by soldering [7] or tightening alignment pins [8]. Transitions from other waveguides, such as microstrip, toward AFSIWs have been reported [7], [9].…”

“…Transitions from other waveguides, such as microstrip, toward AFSIWs have been reported [7], [9]. Furthermore, several devices originally implemented in rectangular waveguide were realized in AFSIW technology, including filters [7], phase shifters [10], and antennas [8], [11]. These AFSIW implementations preserve the benefits of a rectangular waveguide, in particular its low propagation loss, high quality factor, and high electrical shielding between different devices.…”

“…Moreover, they remain fully compatible with standard PCB fabrication processes. The AFSIW cavitybacked slot antenna topology proposed in [8] is adopted, which relies on a rectangular aperture in the bottom or top conducting wall for radiation. Its low profile and planar structure enable a close integration with the optoelectronic circuitry, while preserving a high isolation between both.…”