Anna Papio Toda

60-GHz Substrate Materials Characterization Using the Covered Transmission-Line Method

At millimeter-wave (mm-wave) frequencies, antennas and systems are highly influenced by the electromagnetic characteristics of packaging materials. Accurate knowledge of the complex permittivity of packaging materials is vital for the optimal and robust design of such systems. In this paper, the covered transmission-line method is used to determine the complex permittivity at 60 GHz for several common FR-4 and FR-5 packaging materials. Measurements show that packaging materials must be accurately characterized at high frequencies because their properties can appreciably differ from those at lower frequencies. Moreover, depending on the fabrication process, different thickness samples of the same material can have different permittivity values. The complex permittivity variation versus temperature is also analyzed. We show that, at low frequencies, this variation is negligible, but at mm-wave frequencies, it can represent up to a 5% variation in the relative permittivity and have a severe impact on the loss tangent. The covered transmission-line method is explained in detail and its accuracy and measurable permittivity range are also discussed.

A Compact 60-GHz Wireless Power Transfer System

The first reported full-system 60-GHz wireless power transfer (WPT) solution that can power batteryless and charge coil-free compact WPT devices is presented. The system is fabricated in a 40-nm digital CMOS process and an inexpensive packaging material. In the rectenna (RX), a grid antenna is integrated with a complementary cross-coupled oscillator-like rectifier. At a 4-cm spacing from the transmitter (TX), the RX harvests energy at a rate of 1.22 mW with a 32.8% efficiency, which is significantly higher than the prior state of the art. A novel theoretical analysis of the rectifier operation is presented that formulates all key specifications. The TX is equipped with a quad-core PA that produces a saturated output power (Psat) of 24.6 dBm, which is the highest power delivery in digital CMOS at millimeter-wave bands. The TX peak power-added efficiency is 9.4%. In the TX, a 4 × 8-way differential power combining and a binary-tree architecture are implemented. The designed 2 × 2 grid array antenna helps the TX produce 35.3-dBm peak equivalent isotropically radiated power. The results of the performance characterizations of the full-system and all individually fabricated blocks are reported. The quadcore PA supports power control and beam steering. A four-port TX antenna is designed that shows a 70° steering range in simulations.

On the Projection of Curved AMC Reflectors From Physically Planar Surfaces

We develop a new class of planar low-profile artificial magnetic conductors (AMC) that act as curved magnetic mirrors, i.e., they project the AMC functionality on a curved surface, even though they are geometrically flat. We show that these curved AMCs, despite their thin profile, focus electromagnetic waves similarly to curved metallic reflectors, while, as magnetic mirrors, having a focal region extremely close to their textured surface. An appropriately designed dipole antenna integrated in the focal region of such a curved AMC shows superdirectivity commensurate with a physically curved metallic reflector surrounding the corresponding dipole. These curved AMCs are ideal for new low-profile high-directivity antennas, integrable within standard packaging technologies. We focus our analysis on curved AMCs integrated with dipole antennas embedded on a multi-layer packaging technology for the 60-GHz technology platform. However, the approach is quite general and scalable in frequency. We base our analysis on unit cells composed of metallic spirals, but our approach holds for any other AMC unit cell design. As an application, two packaged 300 μm-thick 60-GHz systems are designed occupying quite small areas, 4.6×3.2 mm2 and 4.7×4.5 mm2 respectively and obeying typical packaging technology layout rules. The corresponding antenna elements have gains, including return loss, of more than 9 and 10 dBi, respectively. Prototypes have been fabricated and measured indicating excellent agreement with theoretical expectations. Impedance bandwidths are 13-15 GHz, making this technology ideal for broadband, high-directivity 60 GHz radio applications.

60GHz printed grid array antenna on low cost packaging substrate

In this paper, a printed grid array antenna on a low cost packaging substrate is presented. Simulation and measurement results of the antenna return losses and radiation patterns are provided. Simulations show that the antenna is matched on the frequency band from 57 to 64GHz and has a broadside gain of over 11dB all over the band. Measurement results show that the antenna performance is shifted 2GHz upwards in frequency but is not degraded. The difference between the simulated and the real substrate permittivity has been identified as the source of the frequency response shift.

60GHz waveguide array design for MIMO channel characterization

From a theoretical point of view, the multiple input multiple output (MIMO) approach seems to be one of the best solutions to characterize the communication channel in the 60GHz frequency range. This paper describes the design of a high-gain antenna array with beamforming capabilities working in the millimeter-wave region suitable for such channel measurements. The array consists on 8 horn antennas, separated half wavelength and independently fed by individual transceivers. A simulated gain around 15dB is achieved over the bandwidth from 57–63GHz. The antenna can also provide beamforming with tilt from broadside up to +/− 60deg.

Mm-wave motion tracking system using beamforming antennas

In this paper we analyze the benefit of using beamforming arrays as opposed to using omnidirectional antennas as the receiving antennas of motion tracking systems. A 60 GHz carrier-based ultra-wide band positioning system for the simultaneous location of diverse markers is considered. Two targets simultaneously moving in a realistic indoor environment are tracked using both antenna systems. Results show that the tracking precision is greatly improved with the use of beamforming arrays meanwhile for omnidirectional antennas the error is in the range of meters.

60 GHz beam selection grid antenna on low cost packaging substrate

In this paper, a grid antenna with beam selection capability is presented. The antenna covers the entire 60GHz band, from 57 to 64 GHz, and has a gain greater than 11dB over the whole band. With only 3 different feeding points, fed by in-phase and quadrature signals, the antenna can generate 5 beams between -14° to 14° from broadside in steps of 7°. The antenna, fabricated on a low cost packaging substrate, satisfies the requirements of low cost and small size for mass production and is a good candidate for 60GHz LOS communication systems.

60 GHz Waveguide Array

To characterize the 60GHz channel dynamics and provide data on the beamforming capabilities 60GHz wireless systems should include, high gain antennas are required. The design of a 60GHz array of metallic waveguides with flare horns covering the range from 57 to 63GHz is described. Provided simulations show greater than 15dB gain in the whole bandwidth and beam scanning capability up to ± 60deg. The array meets all the specifications and should prove useful in multibeam reception and beam formation. A calibration technique is also proposed. This allows for detection of transceivers malfunctioning, phase shifters deviations and waveguide fabrication length errors and enables phase correction by addition of a phase shifter before each antenna input.