Broadband Comb-Based Spectrum Sensing

Summary

Researchers at the UCLA Department of Electrical & Computer Engineering have developed a millimeter-wave spectrum analyzer that uses a non-linear fast switch to generate a broadband frequency comb local oscillator (LO) with a tunable repetition rate.

Background

Broadband integrated circuits in millimeter-wave and terahertz (THz) frequencies provide low-cost and compact solutions for high-resolution hyper-spectral imaging and molecular spectroscopy.  Non-linearity of the direct CMOS THz detectors based on the plasma-wave effect in MOS transistors recovers the power of the millimeter-wave/THz signal for building imaging arrays.  However, in order to develop hyper-spectral imaging systems or trace-gas spectrometers, coherent receivers are required to extract the frequency content.  Sub-harmonic mixers have been used in to coherently receive the sub-THz signals.  High-power LO signals are needed in these mixers to down-convert the received signal to low frequencies and multiple VCOs need to be implemented to cover a wide LO frequency range.

Innovation

Researchers at UCLA have developed a millimeter-wave spectrum analyzer that uses a non-linear fast switch to generate a broadband frequency comb LO with a tunable repetition rate.  A broadband frequency comb with a frequency spacing of frep is used to detect the spectrum of any received signal within the same bandwidth.  An NFET is used as a broadband heterodyne plasma-wave detector to down-convert the received tones to distinguishable low frequency tones.  The receiver is operated from 30 to 160 GHz, where the maximum frequency is limited by measurement equipment.

Applications

• High-resolution hyper-spectral imaging
• Molecular spectroscopy

Advantages

• The receiver operates at a wide frequency range, thus no longer require to down-convert the received signal

State Of Development

The described millimeter-wave spectrum analyzer was tested experimentally.

Patent Status

Related Materials

• Aggrawal, H., Chen, P., Assefzadeh, M.M., Jamali, B. and Babakhani, A., 2016. Gone in a picosecond: Techniques for the generation and detection of picosecond pulses and their applications. IEEE Microwave Magazine, 17(12), pp.24-38.
• Jamali, B. and Babakhani, A., 2018. A Self-Mixing Picosecond Impulse Receiver With an On-Chip Antenna for High-Speed Wireless Clock Synchronization. IEEE Transactions on Microwave Theory and Techniques, 66(5), pp.2313-2324.
• Jamali, B. and Babakhani, A., 2016, May. Sub-picosecond wireless synchronization based on a millimeter-wave impulse receiver with an on-chip antenna in 0.13 µm SiGe BiCMOS. In Microwave Symposium (IMS), 2016 IEEE MTT-S International (pp. 1-4). IEEE.