The Future of High Frequency Circuit Design

The cut-off wavelengths of integrated silicon transistors have exceeded the die sizes of the chips being fabricated with them. Combined with the ability to integrate billions of transistors on the same die, this size-wavelength cross-over has produced a unique opportunity for a completely new class of holistic circuit design combining electromagnetics, device physics, circuits, and communication system theory in one place. In this paper, we discuss some of these opportunities and their associated challenges in greater detail and provide a few of examples of how they can be used in practice

A Directly Matched PA-Integrated K-band Antenna for Efficient mm-Wave High-Power Generation

A K-band slot antenna element with integrated GaN (Gallium nitride) power amplifier (PA) is presented. It has been optimized through a circuit-EM co-design methodology to directly match the transistor drain output to its optimal load impedance (\ua0Zopt=17+j46Ω\ua0) while accounting for the over-the-air coupling effects in the vicinity of the transition between the PA and antenna. This obviates the need for using a potentially lossy and bandwidth-limiting output impedance matching network. The measured PA-integrated antenna gain of 15 dBi with a 40% total efficiency at 28 dBm output power agrees well with the theoretically achievable performance targets. The proposed element is compact (\ua00.6 70.5 70.3\ua0λ3\ua0), and thus well-suited to meet the high-performance demands of future emerging beamforming active antenna array applications

Millimeter-Wave and Terahertz Transceivers in SiGe BiCMOS Technologies

This invited paper reviews the progress of silicon–germanium (SiGe) bipolar-complementary metal–oxide–semiconductor (BiCMOS) technology-based integrated circuits (ICs) during the last two decades. Focus is set on various transceiver (TRX) realizations in the millimeter-wave range from 60 GHz and at terahertz (THz) frequencies above 300 GHz. This article discusses the development of SiGe technologies and ICs with the latter focusing on the commercially most important applications of radar and beyond 5G wireless communications. A variety of examples ranging from 77-GHz automotive radar to THz sensing as well as the beginnings of 60-GHz wireless communication up to THz chipsets for 100-Gb/s data transmission are recapitulated. This article closes with an outlook on emerging fields of research for future advancement of SiGe TRX performance

Millimeter-Wave Active Array Antennas Integrating Power Amplifier MMICs through Contactless Interconnects

Next-generation mobile wireless technologies demand higher data capacity than the modern sub-6 GHz technologies can provide. With abundantly available bandwidth, millimeter waves (e.g., Ka/K bands) can offer data rates of around 10 Gbit/s; however, this shift to higher frequency bands also leads to at least 20 dB more free-space path loss. Active integrated antennas have drawn much attention to compensate for this increased power loss with high-power, energy- efficient, highly integrated array transmitters. Traditionally, amplifiers and antennas are designed separately and interconnected with 50 Ohm intermediate impedance matching networks. The design process typically de-emphasizes the correlation between antenna mutual coupling effects and amplifier nonlinearity, rendering high power consumption and poor linearity. This research aims to overcome the technical challenges of millimeter-wave active integrated array antennas on delivering high power (15–25 dBm) and high energy efficiency (≥25%) with above 10% bandwidth. A co-design methodology was proposed to maximize the output power, power efficiency, bandwidth, and linearity with defined optimal interface impedances. Contrary to conventional approaches, this methodology accounts for the correlation between mutual coupling effects and nonlinearity. A metallic cavity-backed bowtie slot antenna, with sufficient degrees of freedom in synthesizing a non 50 Ohm complex-valued optimal impedance, was adopted for high radiation efficiency and enhanced bandwidth. To overcome interconnection’s bandwidth and power loss limitations, an on-chip E-plane probe contactless transition be- tween the antenna and amplifier was proposed. An array of such antennas be- comes connected bowtie slots, allowing for wideband and wide-scan array performance. An infinite array active integrated unit cell approach was introduced for large-scale (aperture area ≈100 λ2) active array designs. The proposed co-design flow is applied in designing a Ka-band wideband, wide scan angle (\ub155\ub0/\ub140\ub0) active array antenna, consisting of the connected bowtie slot radiator fed through the on-chip probe integrated onto the output of a class AB GaAs pHEMT MMIC PA. The infinite array performance of such elements is experimentally verified, presenting a 11.3% bandwidth with a peak 40% power efficiency, 28 dBm EIRP, and 22 dBm saturated power

Co-Design and Validation Approach for Beam-Steerable Phased Arrays of Active Antenna Elements with Integrated Power Amplifiers

An approach for designing a beam-steering active phased array of antenna elements with integrated power amplifiers (PAs) is presented. It is based on an amplifying active integrated unit cell (AiUC) concept, where the AiUC comprises a radiating slot element, a GaN high electron mobility transistor (HEMT), its input matching and DC biasing/feeding circuitry. The HEMT is embedded in the antenna element, being directly impedance-matched to HEMT’s drain output, i.e. without using any intermediate and potentially lossy impedance matching network. The proposed co-design approach involves a full-wave analysis of the AiUC passive part (naturally including elements mutual coupling effects) along with the subsequent full system harmonic balance simulations. Furthermore, we extend the standard definition of the scan element pattern (SEP) to the active scan element pattern (ASEP) that accounts for nonlinear effects of PAs on AiUC performance. We show that the ASEP is, in general, power-dependent and has a different shape as compared to the SEP. The proposed approach has been demonstrated for a K-band AiUC design example. It was verified through an active waveguide simulator, which is equivalent to the 23.7\ub0 H-plane beam-steering case. Measurements are in good agreement with simulations, revealing AiUC 47% peak drain efficiency and 33 dBm maximum radiated power. The predicted scan range is \ub160\ub0 and \ub137\ub0 in the E- and H-plane, respectively