This year has shown increased innovation, integration, and technical maturity across RF frequency bands. This document outlines emerging RF trends that will be covered at ISSCC 2013.
ISSCC 2013 authors will present an ongoing drive toward increasing levels of integration. This trend can be seen in all areas of RF design from mm-Wave, to cellular, to imaging, to wireless sensors. In mm-Wave designs, higher system complexity (front-end, synthesizer, and baseband) is increasingly being integrated onto a single die. In cellular, the push for integration has led to a strong trend of architectures allowing better linearity and co-existence of these multiple bands and standards. In a related trend, there has been much research the last few years into various ways to remove costly and bulky SAW filters and duplexers. Some of these research areas include highly linear blocker-tolerant receivers, mixer-first receivers, feedback blocker cancellation, feed-forward blocker cancellation, N-path filters, and electrical balance of hybrid transformers. Strong work continues in the effort to integrate CMOS PAs while delivering viable power/efficiency performance. Finally, a clear trend this year was a significant number of chips demonstrated in 65nm CMOS compared to other technology nodes. This observation was noted across all frequency ranges and circuit topologies. The chips presented at ISSCC 2013 confirm that RF devices will continue to see larger levels of integration at the chip- and package level for years to come.
Over the past decade, the papers submitted to ISSCC have indicated clear trends in the continuing push to higher frequencies of operation in CMOS and BiCMOS. This trend has continued this year for oscillators, mm-Wave amplifiers, and PAs. An emerging trend is the increasing complexity of systems operating in the 60-to-200GHz range. The push to ever-higher frequencies is being pursued by both industry and academia for various applications. An important application is high-data-rate communication. With the low-GHz frequency spectrum already overcrowded, researchers are continuing to target frequencies above 60GHz. Two other applications for products operating in these frequency bands are imaging and radar. These frequencies are desirable for such products due to their high spatial resolution and enablement of small antenna dimensions, allowing efficient beam-forming arrays. Another continuing trend is the integration of mm-Wave antennas into silicon substrates.
The combination of these two trends (that is, increased integration and the push to higher frequencies) has enabled a new class of fully-integrated application-driven systems. With the availability of many RF and mm-Wave building blocks in CMOS and BiCMOS, fully integrated solutions for specific emerging domains are appearing, both in the RF and the mm- Wave frequency range. These systems are built on a foundation of circuit-block innovations that have been developed over the past few years. Single-chip radars in RF and mm-Wave frequencies with improved resolution, improved efficiency, showing increasing levels of integration are being demonstrated. Similarly, new systems are being developed for ultra-wideband radar and mm-Wave wireless sensing. Demonstrations in the biomedical field are clearly moving from simple electrical measurements towards real medical measurements in realistic environments using systems-in-package (SiP).
We now discuss these two trends supported with data from chips to be presented at ISSCC 2013.
Complexity and maturity in the mm-Wave and sub-mm-Wave ranges
The high cutoff frequency of bipolar transistors and highly downscaled MOS transistors enables the realization of circuits and systems operating in the mm-Wave range. In the last few years, high-data-rate communication in the 60GHz band and car radar around 77GHz have garnered much attention. While the integration level in these domains is already quite high, we see an improvement of the performance of the building blocks (e.g. output power of PAs, spectral purity and tuning range of VCOs).
The 100GHz barrier for the operating frequency of silicon circuits has been broken a few years ago. Whereas initially elementary building blocks like a VCO and an amplifier operating above 100GHz have been realized, we now witness the trend of increasing complexity in circuits operating above 100GHz. Meanwhile, the electrical performances at the building block level improve: the output power of mm-Wave and sub-mm-Wave sources and PAs increases and VCOs can operate at ever-increasing frequencies with a higher tuning range.
Co-existence and efficiency for cellular applications
RX and TX linearization: In the past few years there has been increasing interest in techniques to improve the linearity of transmitters and receivers. Improved linearity in the receivers will ease the requirements on the RF filtering of out-of-band blockers that can be accomplished, for instance, by placing a programmable notch filter in the RF path. TX linearity improvements will benefit performance parameters such as error-vector magnitude (EVM), ACLR and spectral purity.
Efficiency: PA efficiency improvements demonstrated this year will directly impact the battery life in portable applications. These efficiency improvement techniques include analog and digital pre-distortion, dynamic biasing and envelope tracking.
Digitally-assisted RF: The trend towards digitally-assisted RF continues and is increasingly applied to mm-Wave chips. More digitally assisted calibration techniques are being demonstrated in order to improve the overall performance of the transceiver by reducing the impact of analog impairments at the system level. These techniques include: spur cancelation/reduction, IIP2 improvements, and digital pre-distortion.
VCOs: There is a continuing trend toward improvements in phase-noise figure-of-merit (FOM) and power consumption due to circuit techniques like Class-C and Class-D VCOs. This year’s ISSCC shows clear contributions to this field.
This and other related topics will be discussed at length at ISSCC 2013, the foremost global forum for new developments in the integrated-circuit industry. ISSCC, the International Solid-State Circuits Conference, will be held on February 17-21, 2013, at the San Francisco Marriott Marquis Hotel.