Woo Yul Choi

Abstract Driven by advances in signal processing and multiuser detection (MUD) technologies, it has become possible for a wireless node to simultaneously receive multiple signals from other transmitters. In order to take full advantage of MUD in multi-packet reception (MPR) capable wireless networks, it is highly desirable to make the compound signals from multiple transmitters more separable on its constellation at the receiver by coordinating both the transmit power level and carrier phase off

Recent advances in signal processing have demonstrated in-band full-duplex capability at WiFi ranges. In addition to simultaneous two-way exchange between two nodes, full-duplex access points can potentially support simultaneous uplink and downlink flows. However, the atomic three-node topology, which allows simultaneous uplink and downlink, leads to inter-client interference. In this paper, we propose a random-access medium access control protocol using distributed power control to manage inter

A beam-forming antenna module is demonstrated using an integrated CMOS beam-former chip and a simple two-metal layer printed circuit board at <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$V$</tex></formula> -band. The beam-former circuit integrates an absorptive single-pole four-throw switch together with a 4 <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> An accurate scalable small-signal RF CMOS model applicable to high frequencies is developed using 3-D electromagnetic (EM)-based extraction of parasitic elements. Due to multimetal layers, vertical interconnects, substrate loss and substrate-contact rings, the extrinsic parasitic network of CMOS field-effect transistor (FET) is more complicated than GaAs FETs and does not follow simple scaling rules.

A 410-GHz imager consisting of a 4 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">th</sup> sub-harmonic mixer formed with an anti-parallel diode-connected NMOS transistor pair, and an on-chip antenna with 4.4-dB simulated gain is demonstrated in 65-nm CMOS. At −1.6-dBm power delivered to the LO input bond pad, the imager achieves 16.8-dB voltage conversion loss and 34.1-dB DSB noise figure. When the noise bandwidth is 1 kHz, sensitivity is −110 dBm

In multihop wireless networks, data packets are forwarded from a source node to a destination node through intermediate relay nodes. With half-duplex relay nodes, the end-to-end delay performance of a multihop network degrades as the number of hops increases, because the relay nodes cannot receive and transmit at the same time. Full-duplex relay nodes can reduce their per-hop delay by starting to forward a packet before the whole packet is received. In this paper, we propose a pipelined medium a

A transceiver pixel for active imaging incorporating a transmitter (TX) and a coherent receiver (RX) is demonstrated in 65 nm CMOS at 260 GHz. The pixel occupies an area of 450 × 580µm 2 and is the first demonstration of pixels incorporating a TX and a coherent RX which are smaller than λ /2 × λ /2. The pixel exhibits −21.3 dBm total radiated power and −79.5 dBm sensitivity at a 1 kHz noise bandwidth. This sensitivity is about 10 dB better than the state‐of‐the‐art pixel with only a coherent RX.

In this paper, a v-band MMIC self oscillating mixer active integrated antenna using a push-pull patch antenna is presented. The SOM AIA is based on the coupled active parallel feedback oscillator. By using a push-pull patch antenna, the isolation between balanced RF input and in-phase local oscillation is established. Furthermore, since the push-pull patch antenna has very low radiation efficiency for the in phase signal injection, the LO radiation was efficiently suppressed. The circuit is fabr

Over the past 15 years, the output power of silicon submillimeter-wave electronics has increased by a factor greater than 1000 reaching -3.9 dBm at 440 GHz for a single unit in CMOS and -10.7 dBm at 1.01 THz for a 42-element array in SiGe BiCMOS. The smallest power of a 1 kHz bandwidth signal at 420 GHz that can be detected has improved by 100 million times. These and the expected improvements from the ongoing activities should be sufficient to support high resolution imaging with a range of up

This paper addresses the power control problem in wireless multiple access communication systems with a multi-packet reception (MPR) channel. Driven by advances in signal processing and multiuser detection (MUD) technologies such as UWB and MIMO, it has become possible for a wireless node to simultaneously receive several packets from other transmitters. In this case, the receiver node can determine the set of transmitters from which it wants to receive data and instruct them to adjust their tra

A frequency divider with a very low dc power consumption of 3 mW is demonstrated using 0.15 <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\mu{\rm m}$</tex></formula> GaAs pHEMT technology at W-band. The frequency divider is based on an injection lock topology using a cascode field effect transistor (FET) structure. For low-power operation, the oscillator is configured in series-feedback topology using

We proposed an antenna allocation scheme for a full-duplex communication in IEEE 802.11ac WLAN. In the proposed scheme, an access point (AP) with multiple antennas finds the optimal number of the antennas for transmitting and receiving signals to maximize the sum capacity of the uplink and downlink transmissions. We carry out a simulation and show that the proposed scheme can improve the sum capacity in the full-duplex wireless networks.

Kelvin measurements of series inductance and resistance of an on-chip inductor at frequencies from 5 to 10 GHz is demonstrated using a CMOS process. The measurements require 3 DC voltage meters, 3 DC current sources, an AC signal source, and one high frequency probe. The resistance is lower and within 0.5 O of that from a calibrated measurement using a vector network analyzer (VNA), while the inductance is 10% (50 pH) lower. Due to the reduction of the variability of contacts, the range of serie

Driven by advances in the signal processing and antenna technology, it has become possible for wireless nodes to simultaneously transmit and receive a packet through self-interference cancellation using multiple antennas. This is known as a full-duplex communication. In this paper, we propose a MAC protocol with immediate acknowledgement (ACK) for single-channel full-duplex wireless networks. The proposed scheme in a full-duplex communication can solve the hidden terminal problem by using the im

Pixels integrating a transmitter and a coherent receiver in an area of half-wavelength square are proposed for terahertz active imaging. 300- and 427-GHz transceiver pixels are demonstrated using a 65-nm CMOS process. The 300-GHz pixel employs a push-push stacked cross-coupled VCO, which doubles as a transmitter and an LO, and a pair of diode-connected NMOS transistors for mixing. The pixel occupies an area of 450×580µm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.