Abstract- Broadband Oscillator-Free THz Pulse Generation and Radiation Based on Direct Digital-to-Impulse Architecture

M. Mahdi Assefzadeh,  Aydin Babakhani,

http://ieeexplore.ieee.org/document/8022938/

Broadband 0.03-1.1 THz signal generation and radiation are demonstrated based on an oscillator-free direct digital-to-impulse architecture with a 1.9-ps full width at half maximum and 130-GHz 3-dB bandwidth (BW) (200-GHz 10-dB BW) centered at 160 GHz. The radiated pulse achieves a peak pulse effective isotropic-radiated power of 19.2 dBm and peak pulse-radiated power of 2.6 mW. An ON/OFF impulse-shaping technique is introduced and implemented to suppress undesired ringing and to increase dc-to-radiated efficiency. The frequency-comb spectrum of the radiated pulse train with 5.2-GHz repetition rate is measured up to 1.1 THz. At a distance of 4 cm, the measured received SNR at 1 and 1.1 THz is 28 and 22 dB, respectively. A 1.1-THz tone is measured with a 10-dB spectral width of 2 Hz, demonstrating an extremely narrow spectral line width (two parts per trillion). Time-domain picosecond pulses are characterized using a custom femtosecond-laser-based terahertz time-domain spectroscopy system. Coherent spatial combining from two widely spaced chips is demonstrated. It is shown that the starting time of the radiated pulses is locked to the edge of the input digital trigger with a timing jitter of 270 fs. The chip is fabricated in a 130-nm SiGe BiCMOS process technology.

Abstract- Laser-Free THz pulse sources

M. Mahdi Assefzadeh,  Aydin Babakhani

http://ieeexplore.ieee.org/document/8067089/

Laser-free 0.03-1.1 THz signal generation and radiation in silicon is presented based on an oscillator-free direct digital-to-impulse architecture that is capable of generating and radiating pulses with a FWHM of 1.9 ps and a 3dB-BW of 130 GHz centered at 160 GHz. A peak pulse radiated power of 2.6 mW and a peak pulse EIRP of 19.2 dBm are achieved. To suppress ringing after the impulse and increase DC-to-radiated efficiency, an ON/OFF impulse-shaping technique is designed and implemented in the circuit level. Frequency-domain measurements are performed up to 1.1 THz, where the received SNR at 1.0 THz and 1.1 THz is 28 dB and 22 dB, respectively. An extremely narrow spectral line width is demonstrated with a 10-dB spectral width of only 2 Hz at 1.1 THz (two parts per trillion). Time-domain pulses are characterized using a novel fsec-laser-based THz-TDS measurement technique. The chip is fabricated in a 130-nm SiGe BiCMOS process technology.

Abstract-Time-Domain Characterization of Silicon-Based Integrated Picosecond Impulse Radiators

Peiyu Chen, M. Mahdi Assefzadeh,  Aydin Babakhani,

http://ieeexplore.ieee.org/document/7990525/

A direct time-domain characterization of silicon-based integrated picosecond impulse radiators using a femtosecond laser-gated optoelectronic sampling technique is developed. In the proposed system, a 1550 nm femtosecond laser source is used to generate an electrical trigger signal fed to a picosecond impulse radiator, and another synchronized 1550 nm femtosecond laser source is used to gate a photoconductive detector. Technical challenges are addressed to synchronize the silicon radiators with the optoelectronic sampling system. This paper presents the details of the proposed technique and characterization of 4.8 ps impulses radiated by a custom silicon chip.