Combined differential-mode and common-mode (mixedmode) scattering parameters (s-parameters) are well adapted to accurate measurements of linear networks at RF and microwave frequencies. The relationships between standard s-parameters with two-port vector network analyzer (VNA) and mixed-mode s-parameters with four-port VNA are derived in this paper. An example differential structure was measured with standard two-port VNA and mixed-mode four-port VNA. The correlation of standard s-parameters and mixed-mode s-parameters is presented as well.

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. Index Terms-Antenna in package (AiP), low-temperature cofired ceramic (LTCC), 60-GHz radio. I. INTRODUCTIONA N IEEE standards group, 802.15.3c, is defining specifications for 60-GHz radios to use a few gigahertz of unlicensed spectrum to enable very high-data-rate applications such as high-speed Internet access, streaming content downloads, and wireless data bus for cable replacement. The targeted data rate for these applications is greater than 2 Gb/s [1].The 60-GHz radios have been typically designed as an assembly of several microwave monolithic integrated circuits (MMICs) in gallium arsenide (GaAs) semiconductor technology. They have been used for Gigabit Ethernet (1.25 Gb/s) bridges between local area networks [2]. A recent work has Manuscript

A Yagi antenna implemented in a thin cavity-down ceramic ball grid array package in low temperature cofired ceramic (LTCC) technology is reported. The antenna, intended for use in highly integrated differential 60-GHz radios, has achieved a 10-dB impedance bandwidth of 2.3 GHz from 60.6 to 62.9 GHz and a peak gain of 6 dBi at 62 GHz.Index Terms-60-GHz radio, antenna-in-package (AiP), low temperature cofired ceramic (LTCC).

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