Measurements of the sideband conversion gain ratio of a millimeter-wave heterodyne sub-harmonic mixer using a fourier transform spectrometer

A Fourier transform spectrometer, based on a Martin-Puplett polarisation rotation interferometer and using broad-band blackbody noise sources, has been used to study the sideband response i.e., conversion gain, of a room temperature Schottky diode sub-harmonic mixer operating at 300 GHz. The technique enables the response of the mixer to be characterised and preferentially tuned to one sideband, thereby improving the rejection of unwanted spectral components which can be present in the mixer image sideband.     

Silicon slow-light-based photonic mixer for microwave-frequency conversion applications

We describe and demonstrate experimentally a method for photonic mixing of microwave signals by using a silicon electro-optical Mach-Zehnder modulator enhanced via slow-light propagation. Slow light with a group index of ~11, achieved in a one-dimensional periodic structure, is exploited to improve the upconversion performance of an input frequency signal from 1 to 10.25 GHz. A minimum transmission point is used to successfully demonstrate the upconversion with very low conversion losses of ~7 dB and excellent quality of the received I/Q modulated QPSK signal with an optimum EVM of ~8%.     

High linearity AlGaN/GaN HEMT with double-Vth coupling for millimeter-wave applications

We demonstrated an AlGaN/GaN high electron mobility transistor(HEMT)namely double-Vthcoupling HEMT(DVC-HEMT)fabricated by connecting different threshold voltage(Vth)values including the slant recess element and planar element in parallel along the gate width with N;O plasma treatment on the gate region.The comparative studies of DVC-HEMT and Fin-like HEMT fabricated on the same wafer show significantly improved linearity of transconductance(Gm)and radio frequency(RF)output signal characteristics in DVC-HEMT.The fabricated device shows the transconductance plateau larger than 7 V,which yields a flattened fT/fmax-gate bias dependence.At the operating frequency of 30 GHz,the peak power-added efficiency(PAE)of 41%accompanied by the power density(Pout)of 5.3 W/mm.Furthermore,the proposed architecture also features an exceptional linearity performance with 1-d B compression point(P1 d B)of 28 d Bm,whereas that of the Fin-like HEMT is 25.2 d Bm.The device demonstrated in this article has great potential to be a new paradigm for millimeter-wave application where high linearity is essential.     

High process gain opto-electronic matched filters for communications applications

This paper is concerned with the application of opto-electronic signal processing to a certain class of interference-resistant communications techniques. The processing techniques are applicable to spread spectrum digital transmissions which are processed by a matched filter at the receiver. The analysis of optical delay line matched filters of the diffraction type is discussed. The analysis considers the basic ultrasonic light modulator, that is, the modulation of a light source by a sonic wave. The sonic wave may represent a received spread spectrum signal or received noise or a combination of both. Two ultrasonic modulators in cascade perform the desired correlation or matched filter function. The analysis considers the effects of intermodulation of signal and noise and also the effects of the beamspreading and attenuation of the sonic signal in the delay lines. Finally, the design of a matched filter having 40 dB process gain is presented together with an estimate of its communications performance.Notation angular frequency of light source - wavelength of light source - t time - velocity of sonic wave - s ₁(t)+ ₁ phase of signal input to first delay line - n(t) phase of noise input to first delay line - s ₂(t)+ ₂ phase of signal input to second delay line - ₁, ₂, _n angular frequencies of the carriers ofs ₁(t),s ₂(t) andn(t) respectively - ₁, ₂, _n wavelength, in quartz, corresponding to ₁, ₂ and _n respectively - ₁, ₂, _n maximum change in refractive index due to signals corresponding tos ₁(t),s ₂(t) andn(t), respectively - J _r(X) Bessel function of first kind, orderr and argumentX - L width of sonic beam in direction of incident light - SNR signal-to-noise ratio - IM intermodulation - IMN intermodulation noise - M process gain factor - f _c,_c frequency and wavelength of sonic carrier - 2f _d bandwidth of sonic signal - m f _d/f_c - Kbps kilo-bits-per-second - Mbps mega-bits-per-second - Kpps kilo-pulses-per-second The studies reported in this paper were performed under contract AF30 (602)-4268, Optical Signal Processing, under the direction of Mr R. R. Menard of Rome Air Development Center, Rome, New York, USA.Presented at AGARD (NATO) Avionics Panels, XVIIth Technical Symposium, Tonsberg, Norway, 1969.     

EAM-SOA millimeter-wave frequency up-converter for radio-over-fiber applications

We present an optical scheme for photonic frequency up-conversion at the millimeter-wave bands based on Semiconductor Optical Amplifier. The proposed scheme modulates the bias current with the Intermediate Frequency in order to achieve frequency mixing of an incoming optical signal modulated with the Local Oscillator. Theory indicates that the proposed scheme supports data bandwidths in the tens of GHz for LO values above 10 GHz. This scheme allows for photonic integration of the considered optical devices. A laboratory demonstration of the scheme for up-conversion to the 40 GHz band, using narrow-band IF signals, showed relatively low thresholds for the optical input power and bias current level to achieve error free operation: − 14.5 dBm 100 mA for a 64-QAM signal. Spurious-Free Dynamic Range showed an acceptable performance, with a linearity about 52.5 dB·Hz^2/3 for an optical input power of − 6 dBm.     

Optimized wideband horn antenna for millimeter-wave spectroscopy applications

In the paper, an influence of antennas transmitting the electromagnetic wave to the sample cell of a millimeter-wave molecular spectrometer on the properties of the whole device is discussed. A conventional rectangular horn antenna is considered as the reference antenna, and a double ridge horn antenna is designed, modeled and optimized in order to improve parameters of the spectrometer potentially. A detailed comparison of the reference antenna and the double ridge horn shows that a wider frequency band can be covered by the designed antenna, but the gain achieved is lower.     

Carrier suppression in quadruple frequency modulation by cascaded optical external modulators for millimeter-wave generation

The optical carrier suppression in optical quadruple frequency modulation by cascaded external modulators is investigated theoretically and experimentally. Theoretical analysis demonstrates that the optical carrier suppression ratio is related with not only the initial phase difference of electrical signals applied on the two modulators, but also the optical phase shift between the two modulators. The maximum suppression ratio can be achieved when the total phase difference is equal to nπ＋π/2 （n = 1, 2,…）, which is verified by experiments. By properly controlling the total phase shift, 40-GHz millimeter-wave is generated by using a 10-GHz radio frequency （RF） source and the modulators.     

毫米波频段下MOSFET漏极电流噪声的统一模型

纳米级金属氧化物半导体场效应晶体管(MOSFET)精确的高频噪声模型是毫米波集成电路低功耗设计的重要基础,而现有的高频漏极噪声模型不仅没有融合器件的衬底效应和栅电阻效应,也没有充分考虑器件的频率和偏置依赖性。针对上述问题,基于纳米MOSFET器件的物理特性,并结合漂移扩散方程和有效栅极过载,建立统一表征强反区到弱反区的频率和偏置依赖性的漏极噪声模型,使之便于移植到先进设计系统(ADS)仿真设计。通过所建模型的仿真结果与实验测试结果进行比较,验证所建模型的准确性。同时比较所建模型对130 nm和40 nm MOSFET两种不同工艺器件的实用性,验证其对表征40 nm MOSFET的毫米波噪声特性的优越性。     

毫米波频段下MOSFET漏极电流噪声的统一模型

纳米级金属氧化物半导体场效应晶体管(MOSFET)精确的高频噪声模型是毫米波集成电路低功耗设计的重要基础,而现有的高频漏极噪声模型不仅没有融合器件的衬底效应和栅电阻效应,也没有充分考虑器件的频率和偏置依赖性。针对上述问题,基于纳米MOSFET器件的物理特性,并结合漂移扩散方程和有效栅极过载,建立统一表征强反区到弱反区的频率和偏置依赖性的漏极噪声模型,使之便于移植到先进设计系统(ADS)仿真设计。通过所建模型的仿真结果与实验测试结果进行比较,验证所建模型的准确性。同时比较所建模型对130 nm和40 nm MOSFET两种不同工艺器件的实用性,验证其对表征40 nm MOSFET的毫米波噪声特性的优越性。     

Broadband phase modulators in integrated fin-line technique for millimeter-wave applications

Three structures of broadband reflection type phase modulators in unilateral fin-line are presented.The circuits have been analysed assuming ideal transmission line equivalent circuits for the fin-line sections, while the switching element, a pin-diode, is represented by a typical equivalent circuit at Ka-band.The insertion loss in all three cases is better than 1.5 dB and the phase error for a 180 degrees phase shift is less than 4 degrees over a 12% bandwidth, while a 16% bandwidth is achieved for a 90 degrees modulator at a phase error of 2 degrees.     

Competition between subharmonic and signal beams for photorefractive gain in BSO with two pump beams

It is shown that two pump beams incident upon a bismuth silicon oxide crystal give rise to a subharmonic beam bisecting the pump beam. Simultaneously a signal beam injected between the pump beams may be strongly amplified at the expense of the pump beams. It is shown that the amplified signal beam grows with a faster time constant than the subharmonic beam and that there is competition for gain in the steady state regime.     

Infrared and millimeter-wave sensors for military special operations and law enforcement applications

We consider the application of infrared and millimeter-wave sensors, developed for the most part during the Cold War, to the solution of problems encountered by military special operations units and law enforcement personnel. These problems include detection of weapons concealed beneath clothing, through-the-wall surveillance, and wide-area surveillance under poor lighting conditions. Key sensors used in these applications are infrared cameras, millimeter-wave passive and active cameras, and millimeter-wave real-aperture and holographic radars. This paper discusses each type of sensor, describes its operation, and gives an example of its output, except in those cases where the device is early in its development phase and thus no outputs are available. All of these sensors form images, but the images are of varying quality. We conclude with a brief discussion of methods of using multiple sensors to improve performance.N. C. Currie and R. W. McMillan are permanently employed by the Georgia Institute of Technology, Georgia Tech Research Institute. They are working at Rome Laboratory supported by the Air Force Office of Scientific Research University Resident Research Program.     

High gain predictions for Ni-like Gd ion

Atomic structure data and effective collision strengths for 1s² 2s² 2p⁶ 3s² 3p⁶3d¹⁰ and 54 fine-structure levels contained in the configurations 1s² 2s² 2p⁶ 3s² 3p⁶3d⁹4l (l = s, p, d, f) for the nickel-like Gd ion. These data are used in the determination of the reduced population for the 55 fine structure levels over a wide range of electron densities (from 10²¹ to 10²³) and at various electron plasma temperatures. The gain coefficient for those transitions with positive population inversion factor are determined and plotted against the electron density.     

Compact standing wave thermoacoustic generator for power conversion applications

In the past decade, a variety of thermoacoustic engines (TAEs) were devised to convert thermal energy to acoustic power. In this paper, we optimized the design of a standing wave thermoacoustic generator that can provide high intensity acoustic pressure and convert it into electrical power output using a low cost alternator. Three prototypes of standing wave thermoacoustic generator (TAG) were designed to optimize the overall efficiency. The first prototype of standing wave TAG could produce an acoustic pressure of 0.9 kPa (153 dB) with an input thermal power of 210 W. Further, the maximum heat to electrical conversion efficiency was 0.045% with an input thermal power of 250 W. However, the performance of this system was not fully optimized. The performance of TAE depends upon various parameters including stack position, stack length and resonator length. Hence, a new second prototype of tunable TAG was developed to tune these critical parameters in order to improve the overall efficiency. A compact third prototype of TAG was successfully built with optimized parameters and has been tested. In the improved design, high intensity acoustic pressure of 2.9 kPa (163.5 dB) was observed for the same 210 W input thermal power. The maximum heat to electrical energy conversion efficiency was 0.084% with an input of 250 W which is 87% higher as compared to the first prototype. The major reason for the lower conversion efficiency is due to the low efficiency of the alternator. In future, high efficiency alternator designs can be employed along with careful impedance matching to obtain higher conversion efficiencies. The results described in this paper demonstrate the potential of developing compact portable acoustic power and electricity generators for decentralized power applications.     

High repetition-rate pulse generation for millimeter-wave pulse signal by two cascaded Gires-Tournois Interferometers

A simple optical approach is proposed to obtain millimeter-wave (MMW) pulse signal by the high repetition-rate pulse generation in two cascaded Gires-Tournois Interferometers (GTIs). Compared with single GTI, the cascaded GTIs can optimize the MMW pulse envelope and improve the performance of radio frequency (RF) signal by adjusting the space of cascaded GTIs to change the reflection times of optical propagating signal. The primary influences for the cascaded GTIs on MMW pulse are analyzed theoretically and measured experimentally. It is shown that the good agreement between experimental results and theoretical simulations verifies the feasibility and flexibility of the proposed scheme.     

A novel Si-rich SiN bilayer passivation with thin-barrier AlGaN/GaN HEMTs for high performance millimeter-wave applications

We demonstrate a novel Si-rich SiN bilayer passivation technology for AlGaN/GaN high electron mobility transistors (HEMTs) with thin-barrier to minimize surface leakage current to enhance the breakdown voltage. The bilayer SiN with 20-nm Si-rich SiN and 100-nm Si$_{3}$N$_{4}$ was deposited by plasma-enhanced chemical vapor deposition (PECVD) after removing 20-nm SiO$_{2}$ pre-deposition layer. Compared to traditional Si$_{3}$N$_{4}$ passivation for thin-barrier AlGaN/GaN HEMTs, Si-rich SiN bilayer passivation can suppress the current collapse ratio from 18.54% to 8.40%. However, Si-rich bilayer passivation leads to a severer surface leakage current, so that it has a low breakdown voltage. The 20-nm SiO$_{2}$ pre-deposition layer can protect the surface of HEMTs in fabrication process and decrease Ga-O bonds, resulting in a lower surface leakage current. In contrast to passivating Si-rich SiN directly, devices with the novel Si-rich SiN bilayer passivation increase the breakdown voltage from 29 V to 85 V. Radio frequency (RF) small-signal characteristics show that HEMTs with the novel bilayer SiN passivation leads to $f_{\rm T}/f_{\rm max}$ of 68 GHz/102 GHz. At 30 GHz and $V_{\rm DS} = 20$ V, devices achieve a maximum $P_{\rm out}$ of 5.2 W/mm and a peak power-added efficiency (PAE) of 42.2%. These results indicate that HEMTs with the novel bilayer SiN passivation can have potential applications in the millimeter-wave range.     

FWM conversion with pump suppression for filterless optical packet switching applications

The use of a Pump-Suppressed Four Wave Mixing PS-FWM wavelength converter in a wavelength conversion and selection switching scheme is examined and demonstrated. The scheme requires a single 2 × 1 Mach Zenhder Interferometer (MZI) and offers substantial pump suppression and efficiency improvement in terms of optical signal-to-noise ratio. Performance measurements on the combination of PS-FWM wavelength converter with an Arrayed Waveguide Grating (AWG) for passive routing, shows the potentially successful use of the scheme in an ultra-fast wavelength routed optical packet switching scheme where the use of optical filters for the separation of the converted signal from the pump is avoided.     

Study of gain flatness for multi-channel amplification in single stage EDFA for WDM applications

In this paper, gain flatness is studied for simultaneous 16-ITU-T channel amplifications at C-band (1,532–1,558 nm) in a single stage EDFA for WDM application at different average inversion levels. The inversion levels are varied due to the change of the input signal levels from the targeted operating point and also for dropping few numbers of channels. Specially designed gain flattening filter (GFF) is used in order to get the flat gain with gain variation ±0.5 dB for −20 dBm/ch input signal power (total input signal power is −8.0 dBm) at a fixed average inversion level which is maintained by proper selection of optimum fibre length and pump power. A specific loss spectrum of GFF is obtained by writing a chirped fibre Bragg grating of length 20 mm. Gain variations are studied by changing the total input signal levels from −8.0 dBm to −20.0 dBm and maintained within 20.0 ± 0.5 dB by using automatic gain control (AGC) circuit. About 15 out of 16 channels are dropped and observed ± 0.5 dB gain-variation which is an important parameter in optical network system.