Kenneth K. O

A 280-GHz Schottky Diode Detector in 130-nm Digital CMOS

A 2×2 array of Schottky-barrier diode detectors with an on-chip patch antenna and a preamplifier is fabricated in a 130-nm logic CMOS process. Each detector cell can detect the 25-kHz modulated 280-GHz radiation signal with a measured responsivity and noise equivalent power (NEP) of 21kV/W and 360pW/ √Hz, respectively. At 4-MHz modulation frequency, NEP should be about 40pW/ √Hz. At supply voltage of 1.2V, the detector consumes 1.6mW. By utilizing the detector, a millimeter-wave image is constructed, demonstrating its potential application in millimeter-wave and THz imaging.

Towards terahertz operation of CMOS

The electromagnetic spectrum between 300GHz and 3THz is broadly referred as terahertz [1]. The utility of this portion of spectrum for detection of chemicals and bio agents, for imaging of concealed weapons, cancer cells and manufacturing defects [1, 2], and for studying chemical species using electron paramagnetic resonance, as well as, in short range radars and secured high data rate communications has been demonstrated. However, high cost and low level of integration for III–V devices needed for the systems have limited their wide use. The improvements in the high frequency capability of CMOS have made it possible to consider CMOS as a lower cost alternative for realizing the systems that can greatly expand the use of this spectrum range.

280-GHz schottky diode detector in 130-nm digital CMOS

A 2×2 array of 280-GHz Schottky-barrier diode detectors with an on-chip patch antenna (255 × 250 μm2) is fabricated in a 130-nm logic CMOS process. The series resistance of diode is minimized using poly-gate separation (PGS), and exhibits a cut-off frequency of 2 THz. Each detector unit can detect an incident carrier with 100-Hz ~ 2-MHz amplitude modulation. At 1-MHz modulation frequency, the estimated voltage responsivity and noise equivalent power (NEP) of the detector unit are 250 V/W and 33 pW/Hz1/2, respectively. An integrated low-noise amplifier further boosts the responsivity to 80 kV/W. At supply voltage of 1.2 V, the entire chip consumes 1.6 mW. The array occupies 1.5 × 0.8 mm2. A set of millimeter-wave images with a signal-noise ratio of 48 dB is formed using the detector. These suggest potential utility of Schottky diode detectors fabricated in CMOS for millimeter wave and sub-millimeter wave imaging.

Sub-millimeter wave signal generation and detection in CMOS

Feasibility of CMOS circuits operating at frequencies in the upper millimeter wave and low sub-millimeter frequency regions has been demonstrated. A 140-GHz fundamental mode VCO and a 324-GHz quadruple pushed VCO in 90-nm CMOS, a 410-GHz push-push VCO in 45-nm CMOS, and 180-GHz Schottky diode and 780-GHz plasma wave detectors in 130-nm CMOS have been demonstrated. With the continued scaling of MOS transistors, 1-THz CMOS circuits will be possible.

Design and Demonstration of 820-GHz Array Using Diode-Connected NMOS Transistors in 130-nm CMOS for Active Imaging

An 820-GHz 8 × 8 diode-connected NMOS transistor active imaging array with an on-chip pixel selection circuit was demonstrated in a 130-nm CMOS technology. The noise performance of this architecture is comparable to the state-of-the-art MOSFET and Schottky diode detector arrays. The imaging array consists of a row and column selector, an array of diode-connected NMOS transistor passive pixels, an analog multiplexer, and a low-noise amplifier bank. At 823 GHz, it achieves 2.56 kV/W of measured mean responsivity with a standard deviation of 18% and 36.2 pW/Hz1/2 of measured mean noise equivalent power (NEP) at 1-MHz modulation frequency with a standard deviation of 67%. The mean responsivity is greater than ~ 2 kV/W between 815 to 835 GHz. The minimum NEP of 12.6 pW/Hz1/2 is the lowest for CMOS based detectors at ~ 1 THz. The 8 × 8 imaging array occupies 2.0 × 1.7 mm2 and consumes 9.6 mW of power. Reducing device sizes to support the increase of operating frequency is expected to increase the variability and mitigation approaches will be required. The measured access time for the pixel is ~ 40 nS. The number of elements that can be connected in a row is determined by the modulation frequency and can be more than 1000 elements while supporting a frame rate greater than 1000 per second. Lastly, the expressions of responsivity and NEP including 1/f noise that can be used for the detector optimization are derived and presented .

9.74-THz electronic Far-Infrared detection using Schottky barrier diodes in CMOS

9.74-THz fundamental electronic detection of Far-Infrared (FIR) radiation is demonstrated. The detection along with that at 4.92THz was realized using Schottky-barrier diode detection structures formed without any process modifications in CMOS. Peak optical responsivity (Rv) of 383 and ~14V/W at 4.92 and 9.74THz have been measured. The Rv at 9.74THz is 14X of that for the previously reported highest frequency electronic detection. The shot noise limited NEP at 4.92 and 9.74THz is ~0.43 and ~2nW/√Hz, respectively.

21.5-to-33.4 GHz Voltage-Controlled Oscillator Using NMOS Switched Inductors in CMOS

To demonstrate the applicability of NMOS switched variable inductors in the millimeter wave frequencies, a 21.5 to 33.4 GHz wide tuning range LC voltage-controlled oscillator (LC-VCO) with frequency tunable output buffers that uses variable inductors is reported. The measured phase noise at 10 MHz offset of VCO fabricated in a 65 nm bulk CMOS process varies from -117 to -109 dBc/Hz. The oscillator core consumes 4 or 6 mA from a 1.2 V power supply. These correspond to a record 43.3% tuning range. FOMT ranges from -191.7 to -181.9 dBc/Hz. With tunable output buffers, the measured signal output power is above -15 dBm across the entire frequencies.

Components for generating and phase locking 390-GHz signal in 45-nm CMOS

Components for generating and phase locking 390-GHz signal are demonstrated using low leakage transistors in 45-nm CMOS. An integrated chain of circuits composed of an 195-GHz oscillator with frequency doubled output at ~390 GHz followed by two cascaded ÷2 injection locked frequency dividers with output frequency of ~49 GHz is demonstrated. The peak power radiated at ~390 GHz by an on-chip antenna is ~2 μW. The oscillator and frequency divider consumes 21 and 6 mW, respectively.

25.2 A 210-to-305GHz CMOS receiver for rotational spectroscopy

Electromagnetic waves in the millimeter- and sub-millimeter-wave frequency ranges are used in fast-scan rotational spectroscopy to detect gas molecules and measure their concentrations [1]. This technique can be used for indoor air quality monitoring, detection of toxic gas leaks, breath analyses for monitoring bodily conditions and many others. This paper reports a 210-to-305GHz receiver (RX) front-end for a rotational spectrometer that achieves SSB noise figure (NF) of 13.9 to 19dB by incorporating an on-chip antenna with a reflector formed using a phase-compensated artificial magnetic conductor (PC-AMC) instead a metal reflector to improve the bandwidth of the antenna, a single balanced subharmonic mixer using a pair of floating-body NMOS anti-parallel diode pairs (FB-APDPs), a hybrid-based broadband port-isolation structure, and a 20-GHz low-noise intermediate frequency (IF) amplifier (Fig. 25.2.1). The front-end is fabricated in a 65nm CMOS process that supports isolated p-wells and 10 copper layers with a ~3μm thick 10th metal layer.

High-Efficiency Power Amplifier Using an Active Second-Harmonic Injection Technique Under Optimized Third-Harmonic Termination

This brief presents an active second-harmonic injection technique to improve the efficiency and bandwidth for high-efficiency power amplifiers (PAs). An optimum third-harmonic termination condition was examined for higher efficiency after the second-harmonic injection using a multiharmonic load-pull simulation. It was determined that the optimum third-harmonic termination is the same as that of the inverse class-F PA. Based on this result, a high-efficiency PA with an optimized third-harmonic termination for the second-harmonic injection was designed for a center frequency of 1 GHz as a main amplifier. The overall system requires an auxiliary second-harmonic amplifier and a diplexer between the main and auxiliary PAs. The PA with an optimized third-harmonic termination for the second-harmonic injection was implemented using a 10-W GaN high-electron-mobility transistor for both the main and auxiliary power stages. Compared with the PA without second-harmonic injection, the bandwidth with a power-added efficiency of more than 80% is extended from 60 (960-1020 MHz) to 180 MHz (880-1060 MHz) after the second-harmonic injection.