Korkut Kaan Tokgöz

• Doctor of Philosophy
• Professor (Assistant) at Sabancı University

Frequency up-conversion is an essential step in wireless communication systems. Meanwhile, frequency multipliers are increasingly becoming an integral part of communication chains operating at millimeter-wave (mmWave) and sub-terahertz (sub-THz) frequencies. They offer a viable alternative to traditional mixers, which are highly constrained by thei...

Wireless Network-on-Chip (WNoC) systems, which interconnect chips using wireless links, face significant challenges in area and power consumption. To tackle these constraints, behavioral models (BMs) are crucial for assessing system performance under various conditions and optimizing parameters like data throughput and power consumption. Building t...

This work presents a neural network DPD for mmWave RF-PAs. Differently from existing neural network-based DPDs, the neural network in the proposed DPD does not reside in the forward data path. Instead, it estimates the polynomial coefficients from the complex Fourier amplitudes of harmonics during a calibration sweep. It can compensate for PA nonli...

A signal flow graph (SFG) representation of small-signal responses of nonlinear microwave circuits around a large-signal operating point is developed using the X-parameters. It is shown that, unlike the SFGs for linear circuits, negative-frequency nodes need to be included explicitly. The development elucidates the circuit-operational meaning of th...

The growth of Artificial Intelligence (AI) and Internet of Things (IoT) sensors has given rise to a synergistic paradigm known as AIoT, wherein AI functions as the decision-maker and sensors collect information. However, a substantial proportion of AIoT rely on cloud-based AI, which process wirelessly transmitted raw data, increasing power consumpt...

p>Signal flow graph (SFG) representation of small-signal responses of nonlinear microwave circuits around a large-signal operating point is developed using the X-parameters. It is shown that, unlike the SFGs for linear circuits, negative-frequency nodes need to be included explicitly. The development elucidates the circuit-operational meaning of th...

The behavioral monitoring of farmed animals such as cattle is a fundamental element of precision farming in that it enables unobtrusive ongoing health monitoring. This application presents two ubiquitous challenges typical of sensing applications of internet-of-things: limited dataset size and dataset imbalance. Recently, data augmentation has emer...

This article introduces a four-element 300-GHz-band bi-directional phased-array transceiver (TRX). The TRX utilizes the same antenna, signal path, and local oscillator (LO) circuitry to operate either in transmitter (TX) mode or receiver (RX) mode. The TX mode adopts the outphasing technique to increase the average output power for higher order mod...

Signal flow graph (SFG) representation of small- signal responses of nonlinear microwave circuits around a large-signal operating point is developed using the X-parameters. It is shown that, unlike the SFGs for linear circuits, negative-frequency nodes need to be included explicitly. The development elucidates the circuit-operational meaning of the...

Signal flow graph (SFG) representation of small- signal responses of nonlinear microwave circuits around a large-signal operating point is developed using the X-parameters. It is shown that, unlike the SFGs for linear circuits, negative-frequency nodes need to be included explicitly. The development elucidates the circuit-operational meaning of the...

An electronic chaos generator involving cross-coupled inverter rings with lengths equal to the smallest odd prime numbers is considered, and a spatiotemporally-varying control parameter, hypothetically corresponding to a physical variable to be sensed, is introduced akin to a baseband signal. It is shown that, owing to the fine-grained structure of...

Precision livestock farming promises substantial advantages in terms of animal welfare, product quality and reducing methane emissions, but requires continuous and reliable data on the animal's behavior. While systems suitable for use within the barn exist, grazing over long distances poses challenges. Here, we address this issue by proposing an ul...

Cattle behavior monitoring is critical for understanding cattle welfare and health status. One of the most powerful and cost-effective monitoring methods is a neural network-based monitoring system that analyzes time series data from inertial sensors attached to cows. However, while deep learning has achieved many successes in pattern recognition,...

Cow behavior monitoring is critical for understanding the current state of cow welfare and developing an effective planning strategy for pasture management, such as early detection of disease and estrus. One of the most powerful and cost-effective methods is a neural-network-based monitoring system that analyzes time series data from inertial senso...

This paper introduces several design techniques to improve the performance of CMOS frequency multipliers that operate at the sub-THz band without increasing the complexity and the power consumption of the circuit. The proposed techniques are applied to a device nonlinearity-based frequency tripler and to a push-push frequency doubler. By utilizing...

This article presents a low-cost and area-efficient 28-GHz CMOS phased-array beamformer chip for 5G millimeter-wave dual-polarized multiple-in-multiple-out (MIMO) (DP-MIMO) systems. A neutralized bi-directional technique is introduced in this work to reduce the chip area significantly. With the proposed technique, completely the same circuit chain...

Emerging applications across environmental, biomedical, and structural monitoring require the measurement of physical variables over extended regions. Because addressing many sensors individually can result in impractical bandwidth and power requirements, there is a need for distributed sensing approaches wherein readouts are obtained directly at t...

This article presents a 60-GHz CMOS transceiver designed for IEEE 802.11ay. To reduce the manufacturing cost, an area-efficient bidirectional technique is utilized in this work. The proposed bidirectional amplifier allows the sharing of interstage passive components. A five-stage power-amplifier (PA)-low-noise-amplifier (PA-LNA) designed based on t...

This letter presents a world-first 300-GHz amplifier in 65-nm standard bulk CMOS (1P9M GP). The amplifier has gain from 273 to 301 GHz, and the peak gain is 21 dB at 298 GHz. The amplifier has 16-stage positive-feedback common-source topology. The power consumption is 35.4 mW from a 1.2-V supply. Transistor ( $1\,\,\mu \text{m}\,\,\times 8\,\,\mu \...

This paper presents a 60-GHz CMOS transceiver targeting the IEEE 802.11ay standard. A calibration block for local oscillator feedthrough (LOFT) and I/Q imbalance featuring high accuracy and low power consumption is integrated with the transceiver. With the help of the proposed calibration, this paper is capable of boosting the data rate with higher...

A 60 GHz antenna switching architecture is presented for millimeter-wave transceivers. This circuit topology re-uses the last stage’s transistor of power amplifier (PA) and the first stage’s transistor of low-noise amplifier (LNA) as switches, and the matching blocks. A two-stage LNA and a two-stage PA are designed considering antenna switching ope...

This paper presents 64-quadrature amplitude modulation (QAM) 60-GHz CMOS transceivers with four-channel bonding capability, which can be categorized into a one-stream transceiver and a two-stream frequency-interleaved (FI) transceiver. The transceivers are both fabricated in a standard 65-nm CMOS technology. For the proposed one-stream transceiver,...

This paper proposes accurate CMOS device de-embedding and modeling methods. For millimeter-wave circuit design, accurate simulation models are required. For this reason, an accurate measurement is a key technique for device characterization, and de-embedding and modeling methods are also very important. In this work, a three-parameter pad model bas...

A fractional- N sub-sampling PLL architecture based on pipelined phase-interpolator and Digital-to-Time-Converter (DTC) is presented in this paper. The combination of pipelined phase-interpolator and DTC enables efficient design of the multi-phase generation mechanism required for the fractional operation. This technique can be used for designing a...

Cross-line, a four-port device, used for capacitive cross coupling in differential millimeter-wave amplifiers is modeled and characterized up to 110 GHz using two-port vector network analyzer measurement results. This passive component is electrically symmetrical to be used in differential amplifiers for decreased amplitude and phase mismatch. Two...

An electrically symmetric cross-line and its characterization are proposed for capacitive cross coupling in differential amplifiers. The characterization of the device is done using two structures. L-2L method is applied to achieve virtual-thru connection of Ground-Signal-Signal-Ground (GSSG) pads and fixtures used in cross-line characterization st...

For millimeter-wave CMOS circuit design, accurate device models are necessary. Especially an accurate de-embedding method is very important. Hence, precise deembedding of pad parasitics is the first and valuable step to achieve accurate device models. In this work, a new pad modeling based on an L-2L de-embedding is proposed. The pad model is deriv...

A shunt characterization method is proposed to characterize a very low impedance transmission line (TL), which is used for decoupling of DC and RF in millimeter-wave CMOS circuits. Since metal-insulator-metal (MIM) capacitors are used to achieve very low impedance the TL named as MIM TL. Two structures are used for this method. S-parameters of MIM...

A multi-port device is characterized using measurement results of a two-port Vector Network Analyzer (VNA) with four different structures. The loads used as terminations are open-, or short-circuited transmission lines (TLs), which are characterized along with Ground-Signal-Ground pads based on L-2L de-embedding method. A new characterization metho...

An Ultra-wideband (UWB), 1-to-6 GHz, 4-bit phase shifter design is presented. The proposed phase shifter utilizes lumped-element, three-stage all-pass network to achieve UWB phase characteristics. Ideal predesign of the phase shifter is done successfully by following the three-stage all-pass network design procedure described in this paper. Followi...