Microwave analysis of SiGe heterojunction double‐gate tunneling field‐effect transistor through its small‐signal equivalent circuit

In this study, Si_0.5Ge_0.5 was used as a source junction material in a tunneling field‐effect transistor (TFET), which was analyzed using technology computer‐aided design (TCAD) simulation and a small‐signal non‐quasi static (NQS) equivalent circuit. The NQS equivalent circuit with additional tunneling resistance (R_tunnel) enables more accurate analyses. By using a de‐embedding process, small‐signal parameters in the intrinsic area were obtained. This process was used to analyze the resistance and capacitance in each section, the tendencies of the materials, and the voltage. The error between the NQS equivalent circuit and TCAD device simulation was within 1.9% in the 400‐GHz regime. A cut‐off frequency (f_T) of up to 0.876 GHz and maximum oscillation frequency (f_max) of 146 GHz were obtained.     

A HEMT large‐signal model for use in the design of microwave switching circuits

The nonlinear sources of switch‐HEMTs have been well analyzed by using the measured data. The small signal intrinsic capacitances (under both positive and negative V _ds operation) have been extracted by an extended small signal model. one‐dimension capacitance model has been effectively applied to model the small signal incremental capacitances directly extracted from the key operation region, which has also automatically taken into account the surface trapping effects. A new capacitance model has been effectively proposed to well fit the key nonlinear source (the deep subthreshold capacitance) of switch‐HEMTs. Simple switching function and additional voltage dependence have been applied to model the wide linear‐region (from high‐ V _gs region to deep subthreshold region) of channel current. On/off state small signal insertion loss, small signal isolation, weak harmonics, and power carrying capabilities are accurately predicted by the large signal model. The model shows very good convergence of circuit simulation. Meanwhile, the simple equations and distinguishing among the capacitances accurately make the scaling rules simple and accurate.     

A de‐embedding method with matrix rectification and influences of residual errors on model parameters extraction of InP HEMTs

As the cutoff frequency of InP HEMTs enters the terahertz band, high frequency measurement and modeling techniques in hundreds of gigahertz become urgent needs for further millimeter monolithic integrated circuits design. We proposed a new de‐embedding method linking device measurements and modeling based on full EM simulation data acquired from HFSS and advanced design system (ADS). The simulation results for passive dummy structures are well consistent with experiments, and the de‐embedding method is proved very effective for a resistive passive device with high distributed embedding surroundings in frequency range below 40 GHz. Based on these experimental facts, the EM simulations were extended up to 300 GHz and corresponding de‐embedding deviation was further investigated. Results show that the proposed de‐embedding method has very high accuracy in the whole frequency region with a maximum S‐parameters deviation of only 2.58%. However, further analysis proves that the small residual errors still significantly affect extracted small signal model parameters of InP HEMTs especially for transit time τ. Thus, further improvements on de‐embedding accuracy or careful considerations of more error functions in modeling process are necessary for obtaining physically meaningful model parameters.     

A parameter extraction method of the PIN diode for physics‐based circuit simulation over a wide frequency range

The accurate physical parameters of the semiconductor devices are critical to the physics‐based circuit simulation, which solves the carrier transport equations to model the semiconductor devices. However, the conventional method extracts physical parameters from low‐frequency measurements such as the DC I‐V curve, which cannot work at high frequencies. To overcome this problem, we propose a physical parameter extraction method of the PIN diode working well from DC to microwave frequencies. Specifically, because the transit‐time effects are dependent on the working frequencies and input power levels, the operation modes of the PIN diode can be divided into three cases from DC to microwave frequencies; therefore, the proposed method extracts the parameters from three measured curves, including the DC I‐V curve, a small‐signal, and a large‐signal voltage waveform both at a microwave frequency. Experiments of a PIN diode SMP1330 circuit show that the error of the conventional method is about 45% at frequencies above 300 MHz, but the maximum error of the proposed method is only 9.5% from DC to 2 GHz. Moreover, the conventional method is unable to characterize the conductance modulation phenomenon, which leads to unexpected signal reflections in PIN limiter circuits and the missing of information in radio transceivers.     

An improved millimeter‐wave small‐signal modeling approach for HEMTs

An improved method to determine the small‐signal equivalent circuit model for HEMTs is presented in this study, which is combination of the analytical approach and empirical optimization procedure. The parasitic inductances and resistances are extracted under pinch‐off condition. The initial intrinsic elements are determined by conventional analytical method. Advanced design system (agilent commercial circuit simulator) is used to optimize the whole model parameters with small deviation of initial values. An excellent agreement between measured and simulated S‐parameters is obtained for 2 × 20 μm² gate width HEMT up to 40 GHz. © 2013 Wiley Periodicals, Inc. Int J RF and Microwave CAE 24:464–469, 2014.     

Machine learning technique based extremely broadband small‐signal behavioral model for InP DHBTs

A novel modeling methodology for indium phosphide (InP) double heterojunction bipolar transistors (DHBTs) based on the theory of Bayesian inference, a well‐known method from the field of machine learning, is presented in this article. An extremely broadband small‐signal behavioral model, from 200 MHz to 325 GHz, is built, tested, and validated in this work, with excellent agreement obtained between the extracted model and the experimental data in the form of S‐parameters. A single finger InP DHBT device, with emitter size of 0.5 × 5 μm² exhibiting an ft of over 550 GHz, is used in the verification example. Taking advantage of regression techniques based on machine learning concepts, the proposed black‐box behavioral model can more accurately predict the behavior of the device compared with the traditional equivalent circuit modeling method. Several sets of measured vs modeled data are shown, indicating the efficacy of the method.     

Application of data mining methods to efficient microwave active device modeling

In this work, the signal and noise behaviors of a microwave transistor within its operation domain (voltage drain to source–V_DS, current of drain to source—I_DS, frequency—f) are modeled by data mining techniques (DMT) without using any information on the microwave circuit theory. The device is modeled by a black box whose small signal (S) and noise parameters are evaluated through data mining techniques, based on the fitting of both of these parameters for multiple bias and configuration. It has been shown that DMT have a high potential of faithful and efficient device modeling. © 2012 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2013.     

Wide stopband harmonic suppressed low‐pass filter with novel DGS

In this article, a wide stopband 20 dB harmonically suppressed low‐pass filter (LPF) using novel defected ground structures (DGSs) is proposed. The DGSs has been analyzed as a low pass filter which shows a significant harmonics suppression in the stopband. The lumped parameter equivalent of the DGSs has been developed to show its effectiveness. The modified equivalent circuit model of the filter helps in placing the transmission zero near ?3 dB cutoff frequency. The LPF is designed on a 0.10 λ_g× 0.09 λ_g substrate size where λ_g is guided wavelength at ?3 dB cut‐off frequency (f_c) equal to1 GHz. The simulation shows a 20 dB harmonic suppression up to 50 f_c. The prototype of the LPF has been developed and with the available vector network analyser, the S‐parameters have been measured upto 20 GHz (20 f_c).The state of the art comparison of the LPF shows a high figure of merit equal to 26 250 which is higher than many recently published works.     

Multiple design approach of dual‐band Wilkinson power divider with arbitrary transmission line ratio

A dual‐band (DB) Wilkinson power divider with multiple design approach is proposed in this article, which consists of two‐section transmission lines (TLs) with arbitrary length ratio, one parallel LC circuit, and one resistor. Compared with the former works with equal physical lengths, the total physical size of the two‐section TLs can be decreased effectively. For a given DB frequency ratio, the maximum size reduction can be newly summarized as (n‐1)/(2n), where n indicates the length ratio of two‐section TLs. From the close‐formed design equations, multiple solutions of circuit parameters are newly summarized for DB operation, thus circuit design could be much more flexible and more efficient. Furthermore, in order to compact the proposed circuit size, compensation technology for two coupled‐line sections is also considered in circuit fabrication. Finally, design charts and an experimental circuit show good agreement with the theoretical simulation. Compared with the former work under the same design conditions: f₂/f₁ = 3.2, f₁ = 1 GHz and f₂ = 3.2 GHz, the proposed work provides compact circuit size and the size reduction is 25% with n = 2, m = 1.     

Compact wideband microstrip‐to‐microstrip vertical transition with extended upper stopband

In this article, a compact wideband microstrip‐to‐microstrip (MS‐to‐MS) vertical transition designed with a slotline stepped‐impedance resonator (SIR) is first presented. Compared with the existing wideband transitions, this proposed transition centered at f₀ can tremendously extend its upper stopband via two introduced transmission zeros around 3f₀ and 5f₀. With the designed equivalent circuit, the working principle is theoretically discussed. To realize the size compactness of this proposed wideband transition, the slotline SIR is replaced by two back‐to‐back connected slotline Y‐junctions. Finally, a prototype wideband transition is simulated and fabricated. A wideband filtering response with its upper stopband up to 6.06 GHz under attenuation better than 15 dB is experimentally achieved as expected in the simulation.     

Bayesian inference‐based small‐signal modeling technique for GaN HEMTs

A new modeling methodology for gallium nitride (GaN) high‐electron‐mobility transistors (HEMTs) based on Bayesian inference theory, a core method of machine learning, is presented in this article. Gaussian distribution kernel functions are utilized for the Bayesian‐based modeling technique. A new small‐signal model of a GaN HEMT device is proposed based on combining a machine learning technique with a conventional equivalent circuit model topology. This new modeling approach takes advantage of machine learning methods while retaining the physical interpretation inherent in the equivalent circuit topology. The new small‐signal model is tested and validated in this article, and excellent agreement is obtained between the extracted model and the experimental data in the form of dc I–V curves and S‐parameters. This verification is carried out on an 8 × 125 μm GaN HEMT with a 0.25 μm gate feature size, over a wide range of operating conditions. The dc I–V curves from an artificial neural network (ANN) model are also provided and compared with the proposed new model, with the latter displaying a more accurate prediction benefiting, in particular, from the absence of overfitting that may be observed in the ANN‐derived I–V curves.     

On the thru‐reflect‐line (TRL) numerical calibration and error analysis for parameter extraction of circuit model

In this work, a resistor standard is introduced into our previously proposed numerical thru‐reflect‐line (TRL) calibration procedure in order to determine the characteristic impedance of the line standard of calibration on the basis of a deterministic method of moments (MoM) algorithm. A comprehensive analytical derivation is presented with regards to electrical properties of such a resistor standard in comparison to other standards. In addition, an error analysis is detailed, which reveals correlations of characteristic parameters in connection with equivalent circuit model development from the conversions from field‐based S‐parameters to circuit‐based Y‐ or Z‐parameters. Interesting properties and criteria are derived, allowing accurate parameter extractions. To validate the proposed numerical TRL calibration procedure with this new resistor standard concept and the developed error analysis, the characteristic impedance of a microstrip line is extracted from a commercial software. In addition, a further example with microstrip discontinuity is shown and the effectiveness of the proposed technique is verified. © 2006 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2006.     

A compact dual band short ended metamaterial antenna with extended bandwidth

A compact dual‐band CPW–fed metamaterial inspired antenna using Composite Right/Left Handed (CRLH) resonant approach is presented in this article. The antenna is designed such that it can be operated in series resonant mode where resonance behavior is characterized by series LC parameters. Proposed antenna comprises two annular ring resonators connected with the signal patch intended to excite the higher order modes. This results extension of second band from 51.4% (f_c = 6.92 GHz) to 69.2% (f_c = 7.35 GHz). In addition to that proposed antenna shows compact nature with an electrical size of 0.14 λ₀ × 0.21 λ0 × 0.01 λ₀ at f₀ = 2.18 GHz. The antenna is operating over 2.14–2.23 GHz, 4.81–9.90 GHz with simulated peak gain of 0.66 and 4.44 dB, respectively. Simulated radiation efficiencies of proposed antenna are 69.8 and 94.1% throughout first and second band, respectively. To examine the resonance and radiation characteristics prototype is fabricated and measured. Observed experimental results are in good agreement with those simulated one. These characteristics makes this antenna is a good candidate for modern wireless communication systems such as Bluetooth, WLAN/Wi‐Fi band. © 2016 Wiley Periodicals, Inc. Int J RF and Microwave CAE 26:435–441, 2016.     

Harmonics and size reduced microstrip branch‐line baluns using shunt open‐stubs

This article presents the design of harmonic suppressed compact microstrip balun, using shunt open‐stubs. Two approaches using Π‐shaped and T‐shaped open‐stub configurations are investigated. Because of the stopband effect of the open‐stubs, the harmonic passband responses are suppressed effectively. A compact‐size balun is realized because both kinds of structures have slow wave characteristics. To validate theoretical predictions, two prototype baluns operating at f₀ = 1 GHz, showing size reduction up to 75% and no spurious passband up to 4f₀ compared with the conventional design are fabricated in microstrip form. © 2011 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2011.     

Bias‐dependent small‐signal modeling of GaAs PIN diodes

A new bias‐dependent small‐signal GaAs PIN diode model is described that is suitable for use in design of circuits like variable attenuators and limiters. The equivalent circuit parameters are extracted from bias‐dependent S‐parameters measured from 1 to 26 GHz for 35 bias currents. Bias‐dependent equations are then curve fitted, and then incorporated into a commercially available computer‐aided design (CAD) simulator. Measured and modeled data track each other very well over a range of bias conditions. © 2001 John Wiley & Sons, Inc. Int J RF and Microwave CAE 11: 99–106, 2001.     

Dual‐wideband filtering power divider based on center‐fed three‐line coupled structure

In this article, a dual‐wideband filtering power divider is proposed by using a center‐fed three‐line coupled structure with three open stubs and two isolation resistors. The center‐fed three‐line coupled structure can generate two wide passbands separated by a transmission zero (TZ). The three open stubs can achieve four TZs around the two passbands, which is conducive to the frequency selectivity. Compared with the reported designs, the bandwidth is extended and the performance of isolation, insertion loss and circuit size can reach balance. The proposed design is implemented with size of 0.22 λ_g × 0.39 λ_g (λ_g is the guided wavelength at the center frequency of the lower passband) which exhibits the 3‐dB fractional bandwidths of 56.5%/24.27% and the insertion loss of 0.51/0.68 dB at the center frequency of two passband (f₁/ f₂) of 1.94/4.2 GHz, while the isolation at f₁/f₂ are higher than 22.5/20.1 dB.     

A metallic 3D printed K‐band quasi‐pyramidal‐horn antenna array

A K‐band (18‐27 GHz) antenna array is presented in this article. By deposing the quasi‐pyramidal‐horn upon a print circuit board (PCB), a traveling‐wave quasi‐pyramidal‐horn antenna is formed. Parasitic rings are introduced to decrease the quality factor for an extended bandwidth. The antenna element demonstrates impedance bandwidth 18.6 to 23.3 GHz. The gain is 10.3 dBi at 20.4 GHz with a stable radiation pattern. The impedance bandwidth of a 2 × 2 array is 18.3 to 22.7 GHz, with a maximum gain of 15.2 dBi at 20.4 GHz. The simulated and measured radiation patterns on E‐ and H‐planes at 20.4 GHz agree well. Taking advantage of the 3D printing technology, the quasi‐pyramidal horn is fabricated by selective laser melting using aluminum alloy for time‐saving and process simplicity. The proposed design highlights the hybrid usage of PCB and metallic 3D printing technology in fabricating microwave devices. It is a capable candidate for wireless communication.     

Radiation pattern of modified box‐horn antenna

The expression for radiation field of modified box‐horn antenna is derived using plane wave spectra for three‐dimensional fields. Modified box‐horn is a modified version of conventional box‐horn, in which the horn exciting the box is flared in both E‐ and H‐planes to increase its aperture size. It supports TE₁₀‐ and TE₃₀‐modes at its aperture. The radiation patterns of modified box‐horn antenna in E‐ and H‐planes are computed at 10 GHz and corresponding radiation parameters are extracted from the plots and compared for different flare angles in E‐plane of pyramidal horn exciting the box. The results for half power beam‐widths in E‐plane demonstrate that the radiation pattern of modified box‐horn in E‐plane can be made narrower by increasing the flare angle in E‐plane of pyramidal horn exciting the box. The radiation patterns of modified box‐horn are also compared with those for TE₁₀‐mode open ended waveguide of same aperture size and it is found that the former is narrower beam in H‐plane than the latter. The analysis has been validated against the experimental results available in the literature. The antenna presented here may find potential application as an element in a phased array for microwave wireless communication/radar beam steering, a feed for reflectors in point‐to‐point microwave communication/satellite communication. © 2008 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2008.     

Stability investigation for InP DHBT mm‐wave power amplifier

In this article, we discuss stability issues for mm‐wave monolithic integrated power amplifiers using InP double heterojunction bipolar transistor (DHBT) technology targeting E‐band applications at 71–76 GHz and 81–86 GHz. Different stability detection methods based on the classical two‐port K‐Δ_s pair, linear three‐port graphical analysis, system identifications, circuit modal analysis, and normalized determinant function are all reviewed. The corresponding techniques are employed to predict the occurrence of instability at 15 GHz observed during measurements on a fabricated monolithic microwave integrated circuit power amplifier. Experimental results from a redesigned power amplifier with improved stability are presented to confirm that the previously detected oscillation loop is removed using odd‐mode stabilization resistors with the correct choice of values and locations. © 2012 Wiley Periodicals, Inc. Int J RF and Microwave CAE 23: 662–674, 2013.