Annick Penarier

Near-Field Electromagnetic Characterization and Perturbation of Logic Circuits

We propose here a nondestructive electromagnetic (EM) near-field test bench for both EM compatibility and susceptibility of circuits. This setup permits both the collection of the near field and injection without contact of a disturbing EM field, all through a probe. Exhaustive characterizations of probes are undertaken via simulations and experiments. According to their design, they are supposedly linked more to the electric or the magnetic field. Simulations of their EM behavior are undergone to fix their optimal geometries, leading to the best measurement performances. It is shown by both the simulations and the S-parameter measurements that their presence does not interfere with the electric behavior of the device under test. Then, logic circuits are characterized from the EM point of view, with the help of this test bench. Circuits are placed on three different printed boards: one double-sided low-frequency board without a ground plane and two single-sided boards with a ground plane and a design that is more or less optimized. EM near-field mappings highlight the strong field areas of the circuits. The need for a ground plane is highlighted. Field patterns on the traces are linked with those observed on microstrip lines. Then, an EM aggression is injected over a supposed sensitive zone of the circuit. Whichever printed board is considered, a parasitic signal superimposes itself on the output signal of the gates. Deepened studies are undergone to exhaustively explain the phenomena observed.

Linear to radial polarization conversion in the THz domain using a passive system

This paper addresses a passive system capable of converting a linearly polarized THz beam into a radially polarized one. This is obtained by extending to THz frequencies and waveguides an already proven concept based on mode selection in optical fibers. The approach is validated at 0.1 THz owing to the realization of a prototype involving a circular waveguide and two tapers that exhibits a radially polarized beam at its output. By a simple homothetic size reduction, the system can be easily adapted to higher THz frequencies.

Plasma-Wave Detectors for Terahertz Wireless Communication

We report on terahertz wireless communication experiments at 0.3 THz using 250-nm gate-length GaAs/AlGaAs field-effect transistor (FET) as a detector and unitraveling-carrier photodiode as a source. The physical mechanism of the detection process is terahertz wave rectification on nonlinearities related to overdamped plasma oscillations in the transistor channel. We present an experimental study of rectification bandwidth and show for the first time that room-temperature direct detection with modulation bandwidth of up to 8 GHz can be achieved, thus showing that nanometer-sized FETs can be used as valuable detectors in all-solid-state terahertz wireless communication systems.

Wireless communication at 310 GHz using GaAs high-electron-mobility transistors for detection

We report on the first error-free terahertz (THz) wireless communication at 0.310 THz for data rates up to 8.2 Gbps using a 18-GHz-bandwidth GaAs/AlGaAs field-effect transistor as a detector. This result demonstrates that low-cost commercially-available plasma-wave transistors whose cut-off frequency is far below THz frequencies can be employed in THz communication. Wireless communication over 50 cm is presented at 1.4 Gbps using a uni-travelling-carrier photodiode as a source. Transistor integration is detailed, as it is essential to avoid any deleterious signals that would prevent successful communication. We observed an improvement of the bit error rate with increasing input THz power, followed by a degradation at high input power. Such a degradation appears at lower powers if the photodiode bias is smaller. Higher-data-rate communication is demonstrated using a frequency-multiplied source thanksto higher output power. Bit-error-rate measurements at data rates up to 10 Gbps are performed for different input THz powers. As expected, bit error rates degrade as data rate increases. However, degraded communication is observed at some specific data rates. This effect is probably due to deleterious cavity effects and/or impedance mismatches. Using such a system, realtime uncompressed high-definition video signal is successfully and robustly transmitted.

Room temperature coherent and voltage tunable terahertz emission from nanometer-sized field effect transistors

We report on reflective electro-optic sampling measurements of terahertz emission from nanometer-gate-length InGaAs-based high electron mobility transistors. The room temperature coherent gate-voltage tunable emission is demonstrated. We establish that the physical mechanism of the coherent terahertz emission is related to the plasma waves driven by simultaneous current and optical excitation. A significant shift of the plasma frequency and the narrowing of the emission with increasing channel’s current are observed and explained as due to the increase in the carriers’ density and drift velocity.

Near-field wire-based passive probe antenna for the selective detection of the longitudinal electric field at terahertz frequencies

A passive probe antenna for cw near-field microscopy at millimeter and submillimeter wavelengths is defined. It is based on the coupling between a free-space linearly polarized propagating beam to a wire mode. This is obtained efficiently owing to a discontinuous phase plate. This passive “optical” structure allows either the generation of a subwavelength confinement of the longitudinal electric field (polarized along the wire antenna) or, due to reciprocity, the collection of the longitudinal component of the electric field (along the wire antenna) with subwavelength resolution. The emission and collection properties of the proposed antenna have been demonstrated experimentally using a preliminary realization designed to work at 0.1 THz. Experimental results are well supported by calculations.

Investigations of room temperature bolometers for THz applications

We investigate in this work the performance of two configurations of room temperature bolometers dedicated to THz applications. Fabrication processes, noise level, sensitivity and resolution characterizations are presented. Results emphasize the efficiency of the proposed approach.

Terahertz Heterodyne Communication Using GaAs Field-Effect Transistor Receiver

We report the first successful terahertz heterodyne communication using a field-effect transistor for detection. The communication is a real-time transmission of an uncompressed high-definition TV signal at a data rate of 1.5 Gbps with a 307-GHz carrier frequency. The emitter is a frequency-multiplied amplifier chain whose last stage is a second harmonic mixer that multiplies the carrier signal by the data. The receiver only consists of a GaAs high-electron-mobility transistor that acts as a quadratic receiver, and two 20-dB-gain amplifiers, no limiting amplifier or forward error correction were used. A direct communication would be impossible with such a combination of modulation scheme at emission and quadratic detection at reception, while it is possible in a heterodyne configuration. In addition, for the same source power, the heterodyne scheme allows to increase the communication bandwidth from 80 MHz to more than 2 GHz for a local oscillator power of -8 dBm.

Characterization of integrated antenna-coupled plasma-wave detectors with wide bandwidth amplification in 130nm CMOS

A fully integrated 0.3 THz antenna-coupled plasma-wave detector with 10 GHz (measured) bandwidth is presented. Fabricated in 130nm CMOS technology, the chip is formed of an E-shaped patch antenna, plasmonic based Field Effect Transistor (FET) detector and a wide bandwidth amplifier employing inductive shunt peaking. The open drain mode of operation of the detector achieves an absolute responsivity of 10 V/W with a minimum signal to noise ratio (SNR) of 40 dB over the entire bandwidth. With a drain current of 0.24 mA, the responsivity increases by 10X with a decrease in bandwidth to 3 GHz. The detector is also characterized without the on chip amplifier for imaging applications and shows a measured absolute responsivity of 150 V/W for a drain current of 5 μA at 0.3 THz.

Signal-to-noise ratio in terahertz wireless communication using field-effect-transistors as detectors

We report on terahertz wireless communication experiments at 0.2 THz, using a commercial GaAs field-effect-transistor as detector. For the first time, we will present the transmission of pseudo-random bit sequence at 0.2 THz using this commercial transistor and demonstrate open eye-patterns up to 1.5 Gbps. This transistor is integrated into a machined horn, so that its sensitivity is improved to 1 V/W, and has a 10 GHz cut-off frequency. We will discuss signal-to-noise ratio in the terahertz wireless data transmission.