This article addresses basic issues regarding the design and development of wireless access and wireless LAN systems that will operate in the 60 GHz band as part of the fourth-generation (4G) system. The 60 GHz band is of much interest since this is the band in which a massive amount of spectral space (5 GHz) has been allocated worldwide for dense wireless local communications. The article gives an overview of 60 GHz channel characteristics and puts them in their true perspective. In addition, we discuss how to achieve the exploitation of the abundant bandwidth resource for all kinds of short-range communications. The main tenor is that an overall system architecture should be worked out that provides industry with plenty of scope for product differentiation. This architecture should feature affordability, scalability, modularity, extendibility, and interoperability. In addition, user convenience and easy and efficient network deployment are important prerequisites for market success. This article discusses these features and indicates a number of key research topics.

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Exploiting the 60 GHz band for local wireless multimedia access: prospects and future directions

Antenna-on-chip (AoC) and antenna-in-package (AiP) solutions are studied for highly integrated millimeter-wave (mmWave) devices in wireless communications. First, the background, regulations, standard, and applications of 60-GHz wireless communications are briefly introduced. Then, highly integrated 60-GHz radios are overviewed as a basis for the link budget analysis to derive the antenna gain requirement. Next, in order to have deep physical insight into the AoC solution, the silicon substrate's high permittivity and low resistivity effects on the AoC efficiency are examined. It is shown that the AoC solution has low efficiency, less than 12% due to large ohmic losses and surface waves, which requires the development of techniques to improve the AoC efficiency. After that, the AiP solution and associated challenges such as how to realize low-loss interconnection between the chip and antenna are addressed. It is shown that wire-bonding interconnects, although inferior to the flip-chip, are still feasible in the 60-GHz band if proper compensation schemes are utilized. An example of the AiP solution in a low-temperature cofired ceramic (LTCC) process is presented in the 60-GHz band showing an efficiency better than 90%. A major concern with both AoC and AiP solutions is electromagnetic interference (EMI), which is also discussed. Finally, the systems level pros and cons of both AoC and AiP solutions are highlighted from the electrical and economic perspectives for system designers.

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Antenna-on-Chip and Antenna-in-Package Solutions to Highly Integrated Millimeter-Wave Devices for Wireless Communications

The design and measured results of a single-substrate transceiver module suitable for 76-77-GHz pulsed-Doppler radar applications are presented. Emphasis on ease of manufacture and cost reduction of commercial millimeter-wave systems is employed throughout as a design parameter. The importance of using predictive modeling techniques in understanding the robustness of the circuit design is stressed. Manufacturing techniques that conform to standard high-volume assembly constraints have been used. The packaged transceiver module, including three waveguide ports and intermediate-frequency output, measures 20 mm/spl times/22 mm/spl times/8 mm. The circuit is implemented using discrete GaAs/AlGaAs pseudomorphic high electron mobility transistors (pHEMTs), GaAs Schottky diodes, and varactor diodes, as well as GaAs p-i-n and pHEMT monolithic microwave integrated circuits mounted on a low-cost 127-/spl mu/m-thick glass substrate. A novel microstrip-to-waveguide transition is described to transform the planar microstrip signal into the waveguide launch. The module is integrated with a quasi-optical antenna. The measured performance of both the component parts and the complete radar transceiver module is described.

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A compact manufacturable 76-77-GHz radar module for commercial ACC applications

This paper first presents a quasi-cavity-backed, guard-ring-directed, substrate-material-modulated slot antenna. The antenna, intended for use in highly integrated 60-GHz radios, is deliberately designed to exhibit capacitive input impedance to suit low-cost wire-bonding packaging and assembly technique. The antenna implemented in a thin cavity-down ceramic ball grid array (CBGA) package in low-temperature cofired ceramic (LTCC) technology has achieved an acceptable impedance bandwidth from 59 to 65 GHz with an estimated efficiency of 94%. At millimeter-wave (mm-wave) frequency 60 GHz, one of key challenges is how to realize low-loss interconnection between a radio chip and an antenna using wire-bonding technique. This paper then addresses this issue in the framework of antenna-in-package (AiP) design at 60 GHz and proposes a new solution to the challenge. Detailed wirebond design method and results are given. A major concern with AiP is the risk of the antenna coupling to the radio chip. This paper also evaluates this unwanted coupling and shows that the coupling from the in-package antenna to the on-chip inductor is lower than 30 dB for the worst case. These results clearly demonstrate the feasibility and promise of the elegant AiP technology for emerging high-speed short-range 60-GHz wireless communications.

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Antenna-in-Package Design for Wirebond Interconnection to Highly Integrated 60-GHz Radios

The performances of two different interconnection techniques for coplanar MMICs, wire bonding and flip chip, are investigated at millimeter-wave frequencies. By developing an accurate model for the interconnections, which is validated with experimental data up to 120 GHz, the limitations with respect to frequency and interconnection distance of either technique are pointed out, yielding useful data for the design of hybrid MMW-subsystems.

Millimeter-wave performance of chip interconnections using wire bonding and flip chip

The electrical properties of uniform coplanar lines on GaAs have been investigated, using a finite element simulator. Experimental results, extracted from on-wafer measurements to 120 GHz, are in good agreement with the simulated results. Frequency dependent models were developed for all characteristic parameters of the coplanar lines, such as impedance, effective relative dielectric constant and attenuation, describing the behavior of coplanar lines of different geometries over the entire frequency range from 0-120 GHz. Similarly, exact models applicable over the same frequency range have been developed for a number of coplanar elements, such as air bridges, 90 degree corners and probing pads. These models have been implemented in our HP-MDS data base, resulting in accurate designs of a number of millimeter wave circuits.

Models of coplanar lines and elements over the frequency range 0-120 GHz

The impact of the packaging configuration on cross talk and feed back effects caused by parasitic substrate modes is investigated for coplanar millimeter-wave circuits. It is demonstrated theoretically and by means of several circuit examples that both the mounting configuration and the thickness of the semiconductor substrate of coplanar MIMICs have to be chosen appropriately, in order to avoid circuit degradation or even failure.

Avoiding cross talk and feed back effects in packaging coplanar millimeter-wave circuits

Power leakage into surface waves in monolithically integrated millimeter-wave circuits is to a great extent determined by the applied packaging technology. In this presentation it is shown that properly designed flip chip packages will not suffer from surface wave leakage. Coplanar waveguides on GaAs substrates are used to demonstrate the decisive differences in the leakage behavior of flip chip mounted MMICs and more conventional MMW packages, featuring surface mounted MMICs connected by wire bonds. All results are based on full wave spectral domain analysis and measurement data in the frequency range from 10 to 120 GHz.

Advantages of flip chip technology in millimeter-wave packaging

A low-cost 94-GHz monolithically integrated coplanar FMCW radar chip has been developed, using 0.15-/spl mu/m AlGaAs-InGaAs-GaAs PM-HEMT technology. The chip includes a VCO, electrically tunable over several gigahertz, transmit and receive amplifiers, a mixer, and a directional coupler. The monolithic microwave integrated circuits (MMICs) are as small as 8 mm/sup 2/, delivering up to 10 mW of radio frequency (RF) power at a DC power consumption of 0.7 W. The receiver noise figure is 6-7 dB, and the conversion gain is 10 dB.

T. Krems

Papers

Millimeter-wave performance of chip interconnections using wire bonding and flip chip

Models of coplanar lines and elements over the frequency range 0-120 GHz

Avoiding cross talk and feed back effects in packaging coplanar millimeter-wave circuits

Advantages of flip chip technology in millimeter-wave packaging

Single-chip coplanar 94-GHz FMCW radar sensors