Custom designed wireless links: what the 2012 VLSI Symposia had on offer

September 05, 2012 //By Julien Happich
Custom designed wireless links: what the 2012 VLSI Symposia had on offer
Sponsored by the electron devices Society, the Solid State Circuits Society and the Japan Society of Applied Physics, the 2012 VLSI Symposia which took place last summer in Honolulu came as an opportunity for researchers to unveil new short-range wireless links and design concepts. Striking examples include inductive RF coupling solutions for in-chip communications or through-skull neural sensing data collection.

A team of researchers from the Department of Electrical Engineering and Computer Sciences at the University of California, Berkeley, presented a 260 GHz fully integrated CMOS transceiver for wireless chip-to-chip communication. Designed in 65 nm CMOS, the OOK modulation (On/Off Key) transceiver was demonstrated to transmit 10 Gb/s over a range of 40 mm.

The Tx/Rx dual on-chip antenna array is implemented with half-width leaky wave antennas. Each transmitter consists of a quadrupler driven by a class-D-1 PA with a distributed OOK modulator, and outputs +5 dBm of EIRP. The receiver uses a double balanced mixer to down-convert to a Vband IF signal that is amplified with a wideband IF driver and demodulated on-chip.

Figure 1: Sub THz wireless data-link setup.

Another team from the same department presented a 65 nm CMOS-integrated wireless neural sensor with a footprint of 0.125 mm 2 for minimally invasive surgery, drawing only 10.5 μW.

This brain-machine interface consists of an array of electrodes that extend vertically to reach relevant neurons, the wirelessly powered 65 nm CMOS IC integrating four 1.5 μW amplifiers (6.5 μVrms input-referred noise for a 10 kHz bandwidth) with power conditioning and communication circuitry, and an inductive coupling receiver (RX) coil placed on top of the active circuitry to minimize the device’s total footprint.

Figure 2: Conceptual system diagram of a
wireless neural sensor.

This neural sensor is claimed to be able to record action potentials with enough resolution to control a complex robotic prothesis. Data is then transmitted through the brain’s dura to a subcutaneous interrogator.

The four 10-bit, 20 kHz ADCs generate 800 kbps of neural data, which is backscattered after each sample is taken. The interrogator initiates sampling and communication by sending a 20 kHz beacon.

A paper from the Keio University, Japan, disclosed the use of inductive coupling, dubbed ThruChip Interface (TCI) for inter-chip communication. In effect, the idea is to use near-field wireless connections between different

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