On-chip Amplitude Research Articles

Frequency comb generation via synchronous pumped χ(3) resonator on thin-film lithium niobate

Resonator-based optical frequency comb generation is an enabling technology for a myriad of applications ranging from communications to precision spectroscopy. These frequency combs can be generated in nonlinear resonators driven using either continuous-wave (CW) light, which requires alignment of the pump frequency with the cavity resonance, or pulsed light, which also mandates that the pulse repetition rate and cavity free spectral range (FSR) are carefully matched. Advancements in nanophotonics have ignited interest in chip-scale optical frequency combs. However, realizing pulse-driven on-chip Kerr combs remains challenging, as microresonator cavities have limited tuning range in their FSR and resonance frequency. Here, we take steps to overcome this limitation and demonstrate broadband frequency comb generation using a χ(3) resonator synchronously pumped by a tunable femtosecond pulse generator with on-chip amplitude and phase modulators. Notably, employing pulsed pumping overcomes limitations in Kerr comb generation typically seen in crystalline resonators from stimulated Raman scattering.

On-chip Mach Zehnder interferometer-based all-optical amplitude regenerator for optical 16-QAM signals.

We propose an on-chip all-optical multilevel amplitude regenerator scheme over a Mach Zehnder interferometer (MZI) configuration, enabling multiple amplitude-noise suppression on 16-QAM signals. Joint parameter optimization is carried out based on the general nonlinear model of the proposed scheme to significantly reduce the phase distortion caused by the nonlinear interferometer, which is the key to perform the phase preserving operation. The full function of the phase-preserving amplitude regeneration (PPAR) is verified by an experiment on an on-chip nonlinear waveguide with the length of the 2.31 cm. Furthermore, we perform thoughtful investigations on the oscillatory behavior achieved by the silicon MZI regenerator, enabling the full PPAR on 16-QAM signals through the optimized multiple power plateaus. A maximum 1.6 dB improvement of signal quality is achieved by the proposed on-chip amplitude regenerator at the input signal-to-noise ratio (SNR) of 25 dB. The impact from the two-photon absorption (TPA) effect as an positive role in the regenerator is also well discussed.

A 1.5–5-GHz Integrated RF Transmitter Front End for Active Matching of an Antenna Cluster

A recently proposed method for realizing frequency-reconfigurable antennas across a wideband is based on adjusting the feed amplitudes and phases of a multiport antenna. In this article, we demonstrate the feasibility of the method, for the first time, with a conjunction of an integrated RF transmitter and a four-element antenna cluster. The implementation performs on-chip amplitude and phase tuning with supply scaling and delay tuning circuits to tune the antenna cluster without requirement of matching network. The antenna cluster is built with four closely spaced antenna elements implemented on a printed circuit board. The transmitter integrated circuit (IC) is implemented in a 28-nm CMOS process with the chip size of 0.85 mm $\times0.95$ mm, including pads. The proof-of-concept implementation demonstrates tunability across a wideband from 1.5 to 5 GHz.

Amplitude and frequency sensing of microwave fields with a superconducting transmon qudit

Experiments with superconducting circuits require careful calibration of the applied pulses and fields over a large frequency range. This remains an ongoing challenge as commercial semiconductor electronics are not able to probe signals arriving at the chip due to its cryogenic environment. Here, we demonstrate how the on-chip amplitude and frequency of a microwave signal can be inferred from the ac Stark shifts of higher transmon levels. In our time-resolved measurements we employ Ramsey fringes, allowing us to detect the amplitude of the systems transfer function over a range of several hundreds of MHz with an energy sensitivity on the order of 10−4. Combined with similar measurements for the phase of the transfer function, our sensing method can facilitate pulse correction for high fidelity quantum gates in superconducting circuits. Additionally, the potential to characterize arbitrary microwave fields promotes applications in related areas of research, such as quantum optics or hybrid microwave systems including photonic, mechanical or magnonic subsystems.

Low‐power amplitude modulator for wireless application using underlap double‐gate metal–oxide–semiconductor field‐effect transistor

In this study, a design guideline for a modified low-power wideband on-chip amplitude modulator (AM) based on independently driven double-gate metal–oxide–semiconductor field-effect transistor (IDDGMOS) is proposed. The AM performance is then analysed for three different types of underlap engineered IDDGMOS devices. It is observed that the modulator designed with IDDGMOS presents a higher gain and bandwidth for lower power input signals. For analysing the gain–bandwidth performance of the modulator circuit, a small signal model for the devices is considered. The linearity and noise performance of the modulator circuit for different IDDGMOS structures is analysed by studying the 1 dB compression point and the signal-to-noise ratio. The analysis suggested that the most efficient AM circuit performance is achieved for the symmetric underlap IDDGMOS device. The symmetric underlap IDDGMOS AM circuit yields a gain of 11 dB, a bandwidth of 5.5 GHz and a 47.2% efficiency with a distortion less input signal power range of −60 to −33.5 dB. Moreover, the reduced power loss is about 0.047% of the power loss obtained for the conventional complementary metal–oxide–semiconductor device, whereas the bandwidth of the circuit almost triplicates.

Built-in Self Test of RF Subsystems with Integrated Detectors

This paper describes a built-in self test technique for RF subsystems, using low-overhead on-chip detectors to calculate circuit specifications. A novel on-chip amplitude detector has been designed and optimized for RF circuit specification test. The detector has small area overhead with a low-frequency output. A test chip was fabricated in a commercial 0.18 μm CMOS process. By using on-chip detectors in a loopback setup, both the system performance and specifications of the individual components can be accurately measured. Measurements show accurate prediction of system and component specifications.

A 10-MHz Signal Bandwidth Cartesian Loop Transmitter Capable of Off-Chip PA Linearization

This paper presents a wide signal bandwidth Cartesian loop transmitter (CLT) IC for off-chip PA linearization. The CLT can linearize a 10 MHz bandwidth signal by using a feedforward technique to avoid instability caused by a time delay of an RF path. The transmitter is fabricated in 0.13 m CMOS technology. ACLR is improved from 30.2 dB to 38.4 dB and EVM is improved from 5.9% to 1.6% by using the feedback loop when 10 MHz OFDM signal is applied. The fabricated IC also realizes automatic phase and amplitude calibration by using on-chip amplitude and phase difference detector and external controller and result storage. The controller and result storage are realized by the FPGA. The calibration can be finished in 14 sec.

RF detector for on-chip amplitude measurements

A novel on-chip amplitude detector that allows for efficient debugging of complex RF circuits is proposed. The simplicity, low power consumption, flat frequency response, minimal loading of the tested circuit and possibility of multiplexing makes this detector suitable for on-chip RF amplitude measurements. Simulations and measurements confirm the detector operation.