2019-897 THz Impulse and Frequency Comb Generation Using Reverse Recovery of PIN Diode
Background: Broadband pulse generation has a wide range of applications such as high-speed communication, high-resolution radars, spectroscopy, and remote sensing. Techniques to increase bandwidth and radiation power have generated great interest in terahertz (THz) and mm-wave research but are hindered by the limitations of silicon-based technologies. Methods to overcome these limitations have included the use of dynamic pulse generation but programming the phase and amplitude of tones at mm-wave/THz frequencies requires complex circuit blocks. Step-Recovery-Diodes (SRD) are popular for harmonic generation and frequency multipliers due to their ultra-sharp reverse recovery, yet SRDs are not available in silicon processes typically used in THz frequency generation devices. There is a need for SRD available in silicon processes for THz and mm-wave generation.
Innovation: UCLA researchers have demonstrated a PIN diode-based THz pulse radiator implemented in a silicon-based process for broadband pulse generation. In this invention the reverse-recovery of a PIN diode is used to generate THz-pulses (wideband frequency comb), which are radiated through a wideband on-chip antenna. When used in an on-chip slot bow-tie antenna the THz pulse radiator demonstrated an efficiency above 60% over the band of radiation. The disclosed invention demonstrates higher radiation power at frequencies above 300 GHz, a flatter average ERIP spectrum, and lower power consumption (<50x) compared to the current state of the art THz broadband pulse generation.
Potential Applications:
- High-speed communication
- High-resolution radars
- Spectroscopy
- Remote sensing
Advantages:
- Higher radiation power at frequencies above 300 GHz
- Flatter average ERIP spectrum
- Lower power consumption
2019-608 Vibration Sensing and Long-Distance Sounding with THz Waves
Background: Terahertz (THz) detectors can play a key role in a diverse range of applications including measuring the speed of large moving objects and detecting and reconstructing sound over long distances. To be widely used in these areas, these detectors require additional hardware which decreases sensitivity. There is a need for improved THz detector technology to improve sensitivity and expand the potential applications for THz detectors.
Innovation: UCLA researchers have built a terahertz (THz) detector with improved sensitivity. The custom picosecond pulse radiator uses the micro-Doppler phenomenon in the THz regime to improve the sensitivity of detection and accuracy of reconstruction of THz waves. The device was tested in the transmission and reconstruction through micro-Doppler of a ten-second music track and multiple frequency tones. The researchers used sound vibrations over a long frequency range (Hz to KHz) to modulate a carrier signal radiated from a digital-to-impulse silicon chip and the sound waves were recovered via frequency demodulation at the receiver.
Potential Applications:
- THz detectors
- Radars
- Medical devices
- Materials identification/detection
- Imaging
Advantages:
- Utilizes micro-Doppler effect
- Detects vibration signals in THz
- Detects sound waves in THz
Related Materials:
Development-To-Date: A prototype silicon-based picosecond pulse radiator was used to detect and reconstruct a ten-second music track. The device can detect and distinguish between sound tones from 100-400Hz and can use sound vibrations over the frequency ranges of 50 Hz to 1 KHz to modulate a 395.2 GHz carrier signal radiated from a digital-to-impulse (D2I) silicon chip.
2019-266 Broadband Comb-Based Spectrum Sensing
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.
Potential 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
Development-To-Date: The described millimeter-wave spectrum analyzer was tested experimentally.
2022-109 Methods and Apparatus for Intercoupled THZ Radiating Arrays
Background: Efficient THz generation in silicon technologies has been of great interest over the recent years, as it enables an integrated low-cost solution for sensing, radar, communication, and spectroscopy. Due to the limitation of transistors, direct THz generation using a fundamental oscillator is not feasible. Therefore, various approaches have been developed based on harmonic extraction and the frequency multiplication of a fundamental oscillator. In these techniques, the nonlinearity of transistors is utilized to generate higher harmonics from a fundamental oscillator or frequency-multiplier cells. However, such systems have a poor efficiency and low radiated power due to device limitations. Therefore, there is a need for improved THz-generating systems that are efficient and reliable.
Innovation: UCLA researchers in the Department of Electrical and Computer Engineering have developed a technique for THz continuous-wave (CW). Instead of relying on transistor nonlinearity, the UCLA researchers developed a PIN-based technique for efficient THz CW generation, which enables a wide frequency-tuning range and a large phase shift between elements. Compared to previous THz-generating systems, the PIN-based array can achieve a much high radiated power, with the lowest reported phase noise and highest frequency tuning range vs. the state-of-the-art. This invention can be of great value when applied in THz radiation devices and systems in the future, including high-speed wireless communication.
Potential Applications:
Advantages:
- Wide frequency-tuning range
- Low power consumption
- Improved phase-noise performance
Development to Date: Invention has been successfully demonstrated.
Related Papers:
S. Razavian and A. Babakhani, "A Highly Power Efficient 2×3 PIN-Diode-Based Intercoupled THz Radiating Array at 425GHz with 18.1dBm EIRP in 90nm SiGe BiCMOS," 2022 IEEE International Solid- State Circuits Conference (ISSCC), 2022, pp. 1-3, doi: 10.1109/ISSCC42614.2022.9731731.