U. Johannsen

Axial Ratio Enhancement for Circularly-Polarized Millimeter-Wave Phased-Arrays Using a Sequential Rotation Technique

Circular polarization is indispensable for robust wireless communication between mobile devices that operate at mm-wave frequencies. Additionally, phased-array solutions are required to cope with the associated free space path loss. In view of the size constraints for antennas integrated on (Bi)CMOS chips, an array of linearly polarized dipoles using a sequential rotation scheme is an attractive approach to comply with all mentioned requirements. When steering such an array off broadside, however, the axial ratio will severely degrade. It is the purpose of this communication to demonstrate how the axial ratio can be retained by compensating the amplitudes and phases of the individual antenna elements. Measured results on a 6 GHz test-bed show that the axial ratio with the proposed calibration scheme remains below 3 dB within the 3 dB beamwidth of the scanned beam. Results from a 60 GHz test-bed confirm the effectiveness of the method.

Substrate loss reduction in antenna-on-chip design

We have explained the effect of the silicon substrate on the off-chip radiation of an integrated antenna on chip. From this consideration a low-cost approach for an enhanced antenna-on-chip design has been derived and its improved radiation effciency has been confirmed by measurements.

A 71GHz RF energy harvesting tag with 8% efficiency for wireless temperature sensors in 65nm CMOS

This paper presents the first monolithically integrated RF-power harvesting 71 GHz wireless temperature sensor node in 65nm CMOS technology, containing a monopole antenna, a 71 GHz RF power harvesting unit with storage capacitor array, an End-of-Burst monitor, a temperature sensor and an ultra-low-power transmitter at 79 GHz. At 71 GHz, the RF to DC converter achieves a power conversion efficiency of 8% for 5 dBm input power.

On the Yield of Millimeter-Wave Bond-Wire-Antennas in High Volume Production

For the development of highly integrated millimeter-wave front-end modules, a low-cost and high-performance antenna technology is of paramount importance. Here, standard wire-bond technology is a very attractive candidate due to its widespread availability, computationally efficient modeling options, and promising performance as an antenna. A concern often stated with respect to antennas in this technology, however, is its expected low yield in high volume production. This concern is addressed in this communication by means of a dedicated, computationally efficient antenna model in conjunction with standard deviations of state-of-the-art wire-bonders. The results indicate a possible yield of larger than 99.9% for operating frequencies of up to 250 GHz.

Measurement and calibration challenges of microwave and millimeter-wave phased-arrays

The effect of amplitude and phase errors on the radiation properties of phased array can be reduced by using a proper calibration scheme. Based on a brief review of microwave phased-arrays we derived the key requirements for a new anechoic millimeter-wave (mm-wave) antenna set-up which was constructed. The residual measurement errors obtained with this new set-up are low enough for the calibration of low-sidelobe mm-wave phased arrays.

A hairpin Antenna-in-Package concept for RFID tag applications

Antenna integration is a relative new concept for the miniaturization of Radio Frequency (RF) transceivers where a key problem is to achieve a small size at low cost. Traditional solutions, using ceramic materials, are too costly. Additionally, the current trend in RFID applications is the development of smaller and cheaper tags. In this paper, we present an elegant and low-cost Antenna-in-Package (AiP) solution for RFID tag applications. A printed dipole antenna that integrates the balun function with improved filtering characteristics is designed on a low-cost dielectric material. Simulation and measurement results verify the performance of the proposed antenna.

On-Chip Antenna Integration for Millimeter-Wave Single-Chip FMCW Radar, Providing High Efficiency and Isolation

A complete functional 60-GHz BiCMOS single-chip millimeter-wave frequency-modulated continuous wave (FMCW) radar with on-chip integrated antennas is designed, realized, and experimentally validated. The chip is configured with one transmitting and two receiving antennas. A high antenna efficiency and isolation between the transmitting and receiving antennas is achieved by using a cavity-backed on-chip monopole and by optimizing the package environment. Surface-wave losses and back radiation are reduced, and a high antenna gain is obtained with small ripples in the antenna pattern by implementing special structures on the PCB of the integrated circuit package. The experimental results from the single-chip radar show that the on-chip antennas provide a gain of 2 dBi with very low back radiation. The realized antennas achieve an impedance bandwidth of more than 50% with a corresponding simulated efficiency of 45%. In addition, the proposed approach suppresses surface waves and meets the specific FMCW radar requirements, such as a more than 25-dB isolation between the transmitting and receiving antennas.

The effect of phase and amplitude quantization on the axial ratio quality of mm-wave phased-arrays with sequential rotation

Several future portable/mobile applications operating at mm-wave frequencies will require circular polarization. At the same time, these applications need to use a phased-array concept in order to cope with the associated free space path loss. By sequentially rotating linearly-polarized antenna elements, circular polarization can be obtained in a phased-array. Calibration is required to obtain a low axial ratio when scanning the beam off-broadside. The purpose of this paper is to show the effect of phase and amplitude quantization on the calibration accuracy of the axial ratio. Measured results from a 60 GHz demonstrator are used to investigate the required accuracy of the phase- and amplitude setting of each of the array elements. It is found that an accuracy of 4 bits results in an axial ratio of 0.73 dB rms for scanning between +/− 30°.

Differential 60 GHz Antenna-on-Chip in mainstream 65 nm CMOS technology

The integration of a differential antenna in mainstream 65 nm CMOS was investigated. A 60 GHz prototype integrated circuit (IC) was developed, including a seal-ring and on-chip calibration structures. Measured results show excellent impedance matching properties over a 10 GHz bandwidth and a moderate antenna gain of -1.5 dBi. However, this is still a significant improvement as compared to state-of-the-art in mainstream CMOS.

A 60-GHz rectenna for monolithic wireless sensor tags

This paper presents the design of a 60-GHz rectenna with an on-chip antenna and rectifier in 65nm CMOS technology. The rectenna is often the bottleneck in realizing a fully-integrated monolithic wireless sensor tag. In this paper, problems of the mm-wave rectifier are discussed, and the self-threshold voltage modulation method is proposed for better sensitivity and efficiency. Based on this discussion, the design of a 60 GHz rectenna is provided. The designed on-chip antenna has 2 dBi gain at 60 GHz. The designed rectifier reaches 4.4% efficiency with 7 dBm input power with a 1.5 kΩ load in simulation.