Browsing by Author "Jamali, Babak"

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    Integrated Millimeter-Wave and Sub-Terahertz Pulse Receivers for Wireless Time Transfer and Broadband Sensing
    (2019-12-03) Jamali, Babak; Babakhani, Aydin; Knightly, Edward W.
    Broadband sensing and spectroscopy in millimeter-wave and sub-THz frequencies can be facilitated with CMOS integrated circuits as low-cost, compact solutions. Wireless integrated systems in the mm-wave/THz regime pave the path for various novel applications, such as high-resolution imaging, broadband spectroscopy, and high-speed communication. Particularly, generation and detection of ultra-short picosecond pulses on silicon platforms have been of interest to researchers due to enhanced tunability and bandwidth of such signals. In this dissertation, silicon-based ultra-short pulse detectors are studied with special focus on two primary applications: wireless time transfer with sub-picosecond accuracy and broadband spectroscopy and sensing. First, a self-mixing mm-wave impulse detector is introduced for high-accuracy wireless clock synchronization. Measurement results of the fabricated silicon chip demonstrate that a low-jitter sub-10GHz clock signal can be distributed among widely spaced nodes in a large-aperture array. Such a synchronized large-aperture array can enhance the angular resolution in imaging radars. Secondly, a CMOS impulse detector with center frequency of 77 GHz is presented to achieve low-jitter inter-chip wireless time transfer. This impulse detector, which includes an on-chip slot planar inverted cone antenna, is based on a three-stage divide-by-8 injection-locked frequency divider. It is shown that a three-stage divider has better input sensitivity than a single-stage divide-by-8 divider. The output of the receiver is locked to the input repetition rate with an rms jitter of 0.29 ps. A wireless time transfer test with two impulse detector chips demonstrates that a low-jitter 9.5-GHz clock is distributed among widely spaced nodes in a large-aperture array. Finally, a fully integrated coherent detector is introduced which uses a broadband frequency comb as a reference to detect mm-wave and sub-THz signals. The tunable frequency comb, which is generated by high-speed current switches, drives a passive field-effect transistor mixer to down-convert signals captured by an on-chip antenna. This system is capable of detecting any arbitrary spectrum from 50 to 280 GHz with a minimum resolution of 2 Hz. The detector circuit consumes a dc power of 34 mW, which makes it a low-power solution in comparison with conventional mm-wave/THz systems. This detector is utilized as a spectroscopic sensor to characterize different materials based on their responses to mm-wave signals.
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    Methods and related systems of ultra-short pulse detection
    (2019-01-29) Babakhani, Aydin; Jamali, Babak; Rice University; United States Patent and Trademark Office
    Ultra-short pulse detection. At least some example embodiments are methods including: receiving by an antenna a series of ultra-short pulses of electromagnetic energy at a repetition frequency, the receiving creates a pulse signal; self-mixing or intermodulating the pulse signal by applying the pulse signal to a non-linear electrical device, thereby creating a modulated signal; and filtering the modulated signal to recover a filtered signal having an intermodulated frequency being the repetition frequency.
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    Sub-picosecond Wireless Synchronization and Instantaneous Frequency Detection for Agile RF/mm-Wave Receivers
    (2016-04-21) Jamali, Babak; Babakhani, Aydin
    Wireless synchronization of a distributed array with widely spaced sparse elements is a key enabler in the coherent combining of signals in space. The angular resolution of an imaging array can be enhanced by increasing the aperture size of the array, which demands a precision synchronization link with a small timing jitter among the array elements. A wireless method for synchronizing multiple chips will ease the scalability of the array. Millimeter-wave Continuous Wave (CW) sources have been used for this purpose, but they usually suffer from high phase and amplitude jitters due to Non-Line-of-Sight (NLOS) reflections caused by time-varying channels in a multi-path environment. In this work, I present a wireless synchronization receiver using sub-8psec pulses. A novel self-mixing technique is introduced to detect low-power picosecond impulses and to extract the repetition rate (1-10 GHz) with a low timing jitter. Fast spectrum sensing is another key challenge in radio-frequency (RF) systems. Smart reconfigurable systems and sensors that can detect the operating frequency of the received electromagnetic waves are needed for developing cognitive radio systems that can sense used RF channels in the environment and allocate unused frequency bands for their operation. A frequency detector circuit is a key enabler for the front-end of such systems that can be used to build frequency-locked loops, as well as self-tuned reconfigurable receivers. The output settling time in such circuits needs to be short so that fast spectrum sensing can be achieved for frequency-hopping purpose. A high-speed frequency-to-voltage converter (FVC) is presented here that can detect the instantaneous frequency of the input signal with a 2.6 GHz bandwidth.