HEMT Oscillator Research Articles

An X-Band GaN HEMT Oscillator with Four-Path Inductors

An X-band GaN HEMT oscillator implemented with the WIN 0.25 μm GaN HEMT technology is proposed. The oscillator consists of a HEMT amplifier with an LC feedback network with four-path inductors. With the supply voltage of VDD = 2 V, the GaN VCO current and power consumption of the oscillator are 10.8 mA and 21.6mW, respectively. The oscillator can generate single-ended signal at 8.82 GHz and it also supplies output power 1.24 dBm. At 1MHz frequency offset from the carrier the phase noise is 124.95 dBc/Hz. The die area of the GaN HEMT oscillator is 2×1 mm2.

A low-phase noise D-band signal source based on 130 nm SiGe BiCMOS and 0.15 µm AlGaN/GaN HEMT technologies

AbstractThis paper reports on a record-low-phase noise D-band signal source with 5 dBm output power, and 1.3 GHz tuning range. The source is based on the unconventional combination of a fundamental frequency 23 GHz oscillator in 150 nm AlGaN/GaN HEMT technology followed by a 130 nm SiGe BiCMOS MMIC including a sixtupler and an amplifier. The amplifier operates in compression mode as power-limiting amplifier, to equalize the source output power so that it is nearly independent of the oscillator's gate and drain bias voltages used for tuning the frequency of the source. The choice of using a GaN HEMT oscillator is motivated by the need for a low oscillator noise floor, which recently has been demonstrated as a bottle-neck for data rates in wideband millimeter-wave communication systems. The phase noise performance of this signal source is −128 dBc/Hz at 10 MHz-offset. To the best of the authors’ knowledge, this result is the lowest reported phase noise of D-band signal source.

An 4.7 GHz low‐power cross‐coupled GaN HEMT oscillator

AbstractA GaN HEMT oscillator implemented with the WIN 0.25 μm GaN HEMT technology is designed. The oscillator consists of two HEMT amplifiers with cross‐coupled feedback topology. With the supply voltage of VDD = 0.4 V, the GaN VCO current and power consumption of the oscillator are 6.673 mA and 2.669 mW, respectively. The oscillator can generate differential signal at 4.7 GHz and it also supplies output power − 5.3 dBm. At 1 MHz frequency offset from the carrier the phase noise is −121.77 dBc/Hz. The die area of the GaN HEMT oscillator is 2 × 1 mm2.

TUNABLE MICROWAVE INTEGRATED CIRCUITS USING BST THIN FILM CAPACITORS WITH DEVICE STRUCTURE OPTIMIZATION

ABSTRACT The mechanism of losses in barium strontium titanate (BST) thin film capacitors is analyzed at the device level. A geometry dependent RF model is used to minimize the electrode loss. Results show the capacitors' RF quality factors can be further optimized through geometry. A tunable filter and a phase shifter are demonstrated using these design techniques. Successful integration of the BST process with GaN HEMT circuits in the form of a 5 GHz GaN HEMT oscillator is presented. BST thin film technology is shown to be useful for the design of frequency agile circuits and reduction of layout areas in various microwave applications.

Phase Noise Reduction of Microwave HEMT Oscillators Using a Dielectric Resonator Coupled by a High Impedance Inverter

The phase noise reduction in a configuration of the HEMT oscillator with a dielectric resonator coupled by a quarter-wavelength impedance inverter is investigated. Two HEMT oscillators for a satellite payload system are manufactured in the same configuration except for the coupling configuration of the dielectric resonator (DR) in order to empirically demonstrate the phase noise reduction. Experimental result shows that a phase noise reduction by 14 dB can be enhanced by increasing the characteristic impedance of a coupling microstrip impedance inverter.

A microwave HEMT oscillator with a directly coupled port at 4.2 K

AbstractAn X‐band HEMT oscillator is designed and tested at the cryogenic temperature of liquid helium. The designed oscillator has a directly coupled port in addition to an output port to obtain circuit simplicity. For the novel oscillator configuration, an analytic design formula of the feedback network is derived. The measured data at cryogenic temperature show a significantly improved phase noise and output power compared to the performance of an oscillator operating at room temperature. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 31: 159–162, 2001.

An asymmetric feeding X-band active frequency-scanning leaky-wave antenna

An asymmetric feeding X-band active leaky-wave antennas is developed, to excite the first high order mode of the microstrip leaky wave antenna. One is the asymmetric feeding leaky-wave antenna which integrated with a HEMT oscillator, and the other is the frequency-tuned leaky-wave antenna which integrated with a varactortuned HEMT VCO. The microstrip leaky-wave antenna is operated in the first higher mode. To excite the first higher mode, the microstrip leaky-wave antenna is fed asymmetrically. The dominant mode excitation has been successfully suppressed by adding a sequence of covered wire in the center of the microstrip leaky wave antenna. The design of these active leaky-wave antennas is discussed and the beam scanning phenomena of the antenna is presented. The HEMT oscillator frequency is controlled by tuning the varactor DC bias and the beam scanning is demonstrated. The measured scanning angle agree with prediction, it is close to 30°as the VCO frequency tuned from 8.06 GHz to 9GHz.

Tl/sub 2/Ba/sub 2/CaCu/sub 2/O/sub 8/ films: Growth and applications in dc SQUIDs and microwave devices

Tl-2212 thin films were grown ex situ in a two step process on a variety of substrates, including ones with artificially introduced high angle steps. Grain boundary weak links were formed on LaAlO/sub 3/ substrates with steps and on bicrystal substrates and were employed in dc SQUIDs. The white noise level of the SQUIDs was 50/spl mu//spl Phi//sub 0///spl radic/(Hz) at 77 K. A 12.5 GHz HEMT oscillator stabilized with a Tl-2212 resonator gave 8-10 dB lower phase noise than using a gold resonator.

Monolithic coplanar, varactor tunable V-band HEMToscillator with injection locking capability

The authors present a V-band coplanar, varactor tunable HEMT oscillator, which can be injection locked. The phase noise of the locked oscillator is –75 dBc/Hz at 100 kHz offset. The oscillator has a large tuning range of 6 GHz (centre frequency 59 GHz) and an output power of 5.2 dBm.

Large-signal optically controlled HEMT model and oscillator design

A new large-signal equivalent circuit model of a pHEMT with and without illumination has been developed. A HEMT oscillator operating at approximately 31 GHz has been designed and tested, based on this model. The optical tuning frequency range of 31 MHz under a halogen lamp and 60MHz under a GaAs laser illumination has been observed.

A 100-GHz monolithic cascode InAlAs/InGaAs HEMT oscillator

The design, fabrication, and experimental characteristics of a 100-GHz monolithic cascode HEMT oscillator are presented. A cascode pair of InAlAs/InGaAs HEMT's has been used as the active cell to enhance the negative resistance so that more process tolerance can be achieved. The monolithic circuit oscillates around 100 GHz with an output power of 2 dBm at a drain bias voltage as small as 0.9 V. This is the first demonstration of cascode HEMT oscillators at W-band. >

Phase noise in cryogenic microwave HEMT and MESFET oscillators

The influence of cooling on the phase noise of HEMT and MESFET oscillators is addressed. The initial measurements of the device DC characteristics and low-frequency noise (0.1 kHZ-100 kHz) under cooling give indications on the suitability of a given device for use in low-phase-noise cooled oscillators. Cooled pseudomorphic AlGaAs-GaInAs-GaAs HEMTs (PHEMTs) turn out to be particularly well-suited as they are free of collapse and they are free of g-r noise in the frequency range of interest. The authors report on 4 GHz oscillators operated at 110 K and featuring a phase noise below -100 dBc/Hz at 10 kHz from the carrier in spite of a very modest loaded Q

Correction to “wavelength dependence of the optical control of a hemt oscillator”

Correction to “wavelength dependence of the optical control of a hemt oscillator”

A general approach for the S-parameter design of oscillators with 1 and 2-port active devices

A circular function that serves as a basis for deciding if a circuit will continuously oscillate is introduced. The circular function is derived from the signal flow graph of the circuit including the external load. Any node in the flow graph can be split into two nodes, one of which contains incoming branches and the other of which contains outgoing branches. The circular function is then the transfer function between the two nodes, and it can be measured or simulated by looking at the reflection coefficient of a circulator inserted at the node that was originally split. Oscillations occur when the circular function is unity. The stability of these oscillations is determined by considering the behavior of the circular function as the circuit saturates. The circular function can be applied to one-port oscillators that use negative resistance devices and to feedback oscillators containing transistors, and it reduces to previously published results for specific circuit topologies. To verify the practicality of this approach two 30 GHz HEMT oscillators were designed and tested. >

Wavelength dependence of the optical control of a hemt oscillator

AbstractThe direct optical control, tuning, FM modulation, and injection locking of a 2–GHz HEMT oscillator using a semiconductor laser (α = 0.85 μm) is reported. An optical tuning range of 4.3 MHz and an optical injection locking range of more than 0.55 MHz at fundamental frequency were achieved. For the first time an experimental study relating the photoresponse mechanisms in the HEMT to the wavelength of the incident light is presented. It is shown that for the 0.85–μ‐wavelength illumination the photoconductive effect dominates the optical response of the device, while for 0.633–μm illumination the photovoltaic effect prevails [1]. The photoconductive mechanism, which is smaller but faster, is more suitable for high frequency applications such as direct optical injection locking.

An evaluation of HEMT potential for millimeter-wave signal sources using interpolation and harmonic balance techniques

A large-signal analysis method based on an harmonic balance technique and a 2-D cubic spline interpolation function has been developed and applied to the prediction of InP-based InAlAs/InGaAs heterostructure HEMT oscillator performance for frequencies extending up to the submillimeter-wave range. The large-signal analysis method uses a limited number of DC and small-signal S-parameter data and allows the accurate characterization of HEMT large-signal behavior. The method has been validated experimentally using load-pull measurement. Oscillation frequency, power performance, and load requirements are discussed, with an operation capability of 300 GHz predicted using state-of-the-art devices (f/sub max/ approximately 450 GHz).< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Al/sub 0.3/Ga/sub 0.7/As/GaAs HEMT's under optical illumination

Theoretical and experimental work for the DC and RF performance of depletion mode Al/sub 0.3/Ga/sub 0.7/As/GaAs HEMTs under optical illumination is presented. The photoconductive effect increasing the 2-DEG channel electron concentration and photovoltaic effect in the gate junction are considered. Optical tuning of a 2 GHz HEMT oscillator and optical control of the gain of a 2 to 6 GHz HEMT amplifier are presented and potential applications are described. >

Optical control of microwave semiconductor devices

The use of optically controlled devices to perform a range of circuit functions is reviewed. The optical control of amplifier performance is discussed. The optical control of two- and three-terminal oscillators and optically pumped mixers is discussed. Among the active devices treated are Gunn and IMPATT oscillators; MESFET and HEMT amplifiers, oscillators, and mixtures; and diode mixers. Future directions for research in this area are discussed.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>