Stefano Maddio

A New Design Method for Single-Feed Circular Polarization Microstrip Antenna With an Arbitrary Impedance Matching Condition

This paper introduces a new analytical method suitable for the design of the single-feed circular polarization (CP) microstrip patch antenna. Specifically, the proposed method imposes simultaneously the circular polarization condition as well as an arbitrary input impedance matching condition. The two conditions are enforced by an analytical method derived from an equivalent circuit model of a quasi-symmetrical patch antenna, and manipulated to control the modal detuning. This method can be used as an aid to speed up the design procedure for CP antennas even working with a numeric CAD tool. The validation of this approach is proven designing and fabricating a prototype implementing an original design, which consists of a circular disc slotted by a concentric elliptical cut with coaxial feed and operating at the center frequency of 2.45 GHz. The fabricated prototype exhibited a return loss of about 19 dB, within an impedance bandwidth of 130 MHz, a measured gain of 3.85 dB and a 0 dB axial ratio at 2.45 GHz with a corresponding modal phase difference of 87 degrees.

Analysis and Performance of a Smart Antenna for 2.45-GHz Single-Anchor Indoor Positioning

This paper presents the theoretical analysis and the experimental evaluation of a new switched beam antenna designed to operate at 2.45 GHz. The antenna enables direction of arrival estimation using six directional planar elements arranged to form a platonic solid geometry. It also supports polarization diversity, and it is suitable for single-anchor indoor positioning applications. We adopt the Cramer-Rao bound to study the estimation accuracy of the proposed antenna in absolute 2-D target positioning using received signal strength measurements. First, we describe the design principles for the radiators, we provide an extensive characterization of the switched antenna prototype, and we discuss positioning applications. We then report experimental data that support the results of the theoretical analysis and show consistency between theoretical expectation and the measurements. Finally, we discuss results from proof-of-concept operative indoor positioning example, showing an average localization error as low as 1.7 m.

A Compact Wideband Circularly Polarized Antenna Array for

In this letter, we present a compact single-layer microstrip antenna array for applications in the C-band. The device is designed and fabricated with an overall volume of 45 mm × 45 mm × 1.6 mm, (0.86 λ0 × 0.86 λ0 × 0.03 λ0 at a frequency of 5.75 GHz), a suitable dimension for compact handhelds. The proposed array is based on a modified sequential phase network, composed of nonuniform curved transmission lines, feeding a set of 2 × 2 disc based patch elements. The proposed network has space-filling properties, and is arranged in the unoccupied area between the elements, minimizing the overall dimensions without sacrificing the operating bandwidth. Adequate agreements between the simulated and measured results validate the proposed design: a 3-dB axial ratio band of 900 MHz, meaning 15.5%, a peak gain of 8.25 dB maintained within 3 dB for 1.2 GHz, and a very wide 10-dB return loss bandwidth of 29%. This performance is unmatched for the given dimensional constraint with a single-layer via-less technology .

C

This paper presents a distributed localization system for indoor environment based on a network of compact anchor nodes. The system is based on available low-cost commercial components and it is capable of standard WiFi connectivity at 2.45 GHz. The basic node is equipped with a switch-beam antenna, which is the enabling technology for a Direction of Arrival (DoA) estimation based on Maximum-Likelihood criteria. The adopted DoA estimation procedure is tolerant to noisy power measurements, making it suitable for low-cost effective solutions based on RSSI measurements. The node is designed to be placed in an unobtrusive area for the movement of a mobile target node and is capable to operating as an independent anchor, but it is optimized to cooperate with other identical nodes to form a coordinated network of anchors, capable to monitor an extended indoor area. An experimental characterization demonstrates the DoA performance of the single node.

-band Applications

In this paper a design method for a circular polarized small-size microstrip antenna on a short dielectric layer is presented. Its known that exciting two detuned modes with a single coaxial probe makes possible circular polarization (CP) but as yet little efforts were made in order to control CP frequency and exact 50 ohm matching. A straight forward circuital model for the device can solve both this issues and gives hint for the best radiator design; our prototype is a circular disc slotted by a concentric elliptical cut in order to slightly perturb the central symmetry and obtain the modal degeneration. It includes a SPDT to allow the switching between the two CP. The prototype is designed for 2.44 GHz and exhibits a return loss of 19 dB, an impedance BW of 120 MHz a directivity of 6 dB and an estimated gain of 1.8 dB.

A scalable distributed positioning system augmenting WiFi technology

This paper proposes a new switched beam array optimized for 2.45 GHz wireless indoor applications. The antenna supports directional communication to enable spatial reusability, and polarization diversity to mitigate multipath propagation. It also supports absolute 2D target localization using measurements from a single anchor node. The paper describes the antenna design, the implementation and the experimental characterization, along with its positioning applications. The localization results obtained with data collected from indoor measurements, showing an average localization error as low as 1.7 m.

A design method for single-feed wideband microstrip patch antenna for switchable circular polarization

This paper describes the design principles for a real-time adaptive transmitter leakage canceller and introduces its training algorithm for fast adaptation. The canceller implements the active feed-forward analog cancelling technique, which considers the injection at the receiving input of the self-interfering antiphase signal. An extensive characterization carried out on a prototype designed to operate at the center frequency of 5.8 GHz demonstrates the performance of the prototype in term of cancellation and tracking convergence speed, and confirms the validity of the canceller design principles. Measurements at 5.8 GHz show that for isolation between the transmitting and receiving antenna up to 35 dB with arbitrary phase, an isolation above 60 dB is obtained in 98.5% of the tests and this result is reached in six steps. When applied to a wireless transceiver for electronic-toll collection system operating in full duplex at 5.8 GHz under regulation European Telecommunications Standards Institute ES200674, the prototype permits a signal-to-noise-ratio enhancement of 8.3 dB.

A 2.45 GHz smart antenna for location-aware single-anchor indoor applications

In this paper, we present a distributed positioning system for indoor environment based on a mesh of compact independent anchor nodes. Each node is built of low-cost off-the-shelf components and operates as specialized access points capable of standard connectivity at 2.45 GHz. The key technology for the localization strategy is the switched beam antenna (SBA), which enables a space division multiple access (SDMA) paradigm. The coordinated operation of SBA-equipped anchor nodes constitutes a legacy unmodified IEEE 802.11 network which can exploit the multiplexing mechanism. The latter is the driving force of the estimation strategy, with the positional information obtained as the result of a maximum likelihood algorithm driven by the comparison of a real-time received signal strength indicator (RSSI) with the predicted signal level distribution, which can be estimated and stored without the need of lengthy offline measurement. The signal level prediction is based on a simple propagation model which is effective because benefits of both the elementary antenna radiation beams directivity and the circular polarization operation, two strong aids for the mitigation of the multipath impairment. In turn, these feature make the estimation procedure tolerant to noisy power measurements, hence particularly suitable for cost-effective solutions based on RSSI. Experimental validations demonstrate the performance of a network composed of four anchors arranged in a 2.6 × 3.8 m 2 mesh in a 6 × 7 m 2 office room, and dealing with a single target node. The mean error inside the mesh area is 63 cm while the mean error in the entire room is 1.1 m. Focusing on the cumulative distribution of the error, the 90th percentile value is 1 m considering only the mesh and 1.9 m for the entire room.

Real-Time Adaptive Transmitter Leakage Cancelling in 5.8-GHz Full-Duplex Transceivers

We discuss the development of a wideband LDMOS Doherty PA (DPA) with optimized peak power and efficiency over 550 MHz to 770 MHz of bandwidth. The design was enabled by a wideband output combiner which involves multisection impedance transformation. The DPA delivers more than 46% average efficiency across the band at 48 dBm average power supporting DVB-T signal with 8 MHz bandwidth and PAPR of 10.5 dB. The DPA prototype achieves the target ACPR of - 50 dBc at the upper limit of the bandwidth if digital predistortion is applied.

A Distributed Positioning System Based on a Predictive Fingerprinting Method Enabling Sub-Metric Precision in IEEE 802.11 Networks

This letter presents a signal probability distribution function conscious characterization technique, suitable for the optimization of envelope tracking (ET) power amplifiers. The method and its validation rely on pulsed harmonic load-pull measurements. The analytical treatment permitted to understand the impact of the peak-to-average power ratio on the load termination, and the experimental characterization revealed the sensitivity of the ET performance with respect to the load termination. The technique was applied to a GaN HEMT device at the carrier frequency of 870 MHz.