Showing papers presented at "European Microwave Integrated Circuit Conference in 2011"

A highly efficient octave bandwidth high power amplifier in GaN technology

Abstract: This contribution describes the design and validation of a L-band hybrid high power amplifier for radar application with high power added efficiency (PAE). The HPA is designed using a commercial GaN device by Cree, in a single ended configuration, starting from a simulated load-pull approach. Pulsed measurements of the designed PA demonstrate 90 W of saturated output power across the desired bandwidth with an average PAE of 50%.

A 245 GHz CB LNA in SiGe

Abstract: The paper presents a four stage 245 GHz LNA in SiGe technology Common base (CB) topology is chosen for each stage The amplifier takes advantage of passives like transmission lines and MIM capacitors to realize the input, output and inter-stage matching for the LNAs The LNA has 12 dB gain at 245 GHz, a 3 dB bandwidth of 26 GHz It has a supply voltage of 2V and power dissipation of 28mW The amplifier is intended for the use in ISM band radar systems for consumer application and imaging radar

An integrated harmonic transmitter front-end for 122 GHz FMCW/CW radar sensor

Abstract: This paper presents an integrated harmonic transmitter front-end for a single-chip 122 GHz FMCW/CW radar sensor It consists of two building blocks, a frequency doubler and a two-directional power detector The frequency doubler employs a push-push frequency doubling core and a common-base stage It exhibits a 25 dB conversion gain and a 5 dBm output power The two-directional power detector is used for self testing, which utilizes a single directional coupler to save chip area and to reduce insertion loss It can detect the output power of the transmitter and can detect any antenna mismatch of above −20 dB This transmitter front-end can be fully characterized by DC measurement after integrated into a single-chip 122 GHz transceiver

Novel realisation of a broadband high-efficiency continuous class-F power amplifier

Abstract: This work outlines the analysis and design procedure employed for the realisation of a broadband Continuous Class-F power amplifier. Waveform analysis is used in determining the most sensitive parameters for maintaining high efficiency over a desired bandwidth. A design methodology is then employed for control of the dominant parameters over the band of interest, while preserving maximum fundamental output power. By using a commercially available GaN Cree 10W HEMT transistor, an amplifier was fabricated which is operational over a 20% bandwidth. Greater than 11.4W of output power is found with efficiencies between 65–76% measured over the band from 2.152.65GHz. An average drain efficiency of 70.5% and PAE of 65% is obtained with a corresponding average output power of 13.5W.

A compact L-band broadband 6-bit MMIC phase shifter with low phase error

Abstract: This paper discusses the design and test performance of a compact L-band 6-bit phase shifter monolithic microwave integrated circuit (MMIC). Each bit of this phase shifter design is based on an optimum topology to reach balanced and optimal insertion loss, phase shifting accuracy, gain variation, and bandwidth performance. Extensive electromagnetic simulation is performed in the circuit design to ensure first-pass success. This MMIC is fabricated with the commercially available M/A-COM technology solutions' 0.5μm GaAs pHEMT technology. The chip size of this MMIC is 2.45 mm × 1.35 mm (3.3 mm2). Test results of this phase shifter exhibits 3.8 dB ±0.75 dB insertion loss and state-of-the-art phase error performance of 4° rms phase error over a 53% bandwidth and 2° over a 40% bandwidth.

Balanced active frequency multipliers for W-band signal sources

Abstract: The design and performance of millimeter-wave monolithic integrated circuits implementing active balanced frequency multipliers for the W-band (75–110 GHz) is presented. The multipliers by eight and twelve are realized in a 100 nm gatelength metamorphic high electron mobility transistor technology. A novel circuit architecture using a cascade of active balanced frequency doubler and tripler stages in combination with active unbalanced-to-balanced converters is adopted in order to combine very broadband operation with high spectral purity of the output signal. On the module level, the multiplier by twelve achieves an output power of −1.5 dBm and associated conversion gain of 2.5 dB in the frequency range from 78 to 100 GHz, corresponding to a relative bandwidth of 24.7%. Within this frequency range, unwanted harmonics are suppressed by at least 12 dB with respect to the twelfth harmonic. The multiplier by eight achieves an output power of 6.9 dBm, associated conversion gain of 8.9 dB and harmonic suppression of 13 dBc in the frequency range from 84 to 101 GHz.

Wide band high-efficiency power amplifier design

Abstract: This paper presents a hybrid (passive & active) power amplifier concept for a wideband high drain efficiency power amplifier design. The proposed design integrates for the first time a dual-band PA with an active second harmonic injection to achieve high efficiency across a continuous wideband frequency range of two octaves. The design utilizes a resistively loaded class B at the lower frequencies and a class J mode of operation at the upper frequency band. To maintain high efficiency during the transition between the two PA modes an active second harmonic injection at the output of the main transistor is employed through an addition of an auxiliary low power amplifier. To demonstrate the validity of the novel concept a demonstrator is realized around a 10 W GaN transistor with an average efficiency of 63% across 0.6–2.4 GHz at only modest gain compression of 1dB.

Wideband time-delay circuit

Abstract: Limitations of the delay bandwidth in active delay circuits can be significantly improved in high-order transfer functions In this paper, a flat wideband delay circuit is presented using the 2nd-order form of the Pade approximant The delay circuit is designed and implemented in 018 μm CMOS technology The measured results show that the circuit achieves a delay time of 49 psec in the GHz frequency range The power consumption of the core circuit is 788 mW from 18 V supply voltage The entire die occupies an area of 520×820 μm2

Ruggedness and reliability of GaN HEMT

Abstract: In this paper, we reported evaluation results of our L/S-band GaN HEMT, especially focusing on ruggedness and reliability. In terms of ruggedness, we demonstrated GaN HEMT had 3-terminal breakdown voltage of 250 V and sufficiently wide area of safe operation (ASO) at 200 degC. Simulated peak drain-source voltage of an inverse class-F operation reached 160 V, and 3-terminal breakdown voltage was good enough at 250 V to cope with simulated maximum drain-source voltage. In addition, we carried out 2-type RF stress tests to evaluate ruggedness of GaN HEMT. One is VSWR ruggedness, the other is RF step stress test at stress level from 5 dB to 13 dB gain compression level. No destructive failures and degradations have been observed under both tests. In terms of reliability, we carried out DC-HTOL test for 5000 hours, MTTF was estimated 1.07 × 106 hours at 200 degC. These results show our GaN HEMT has good enough ruggedness and reliability for high power applications.

A scalable X-parameter model for GaAs and GaN FETs

Abstract: A new nonlinear FET model formulation is proposed which comprises an X-parameter (S-function or Poly Harmonic Distortion) intrinsic model combined with lumped extrinsic circuit model shells This enables the correct gate width scaling of the intrinsic and extrinsic model by finger number and unit gate width. An extraction technique is described based on de-embedding the X-parameters to the intrinsic plane. A verification example of scaling of a 10×90um 0.15um pHEMT X-parameter model (generated from a scalable compact model) down to a 4×50um device (a factor of 4.5), is shown without loss of accuracy in power sweep and loadpull contour results compared to the reference compact model simulation.

An enhanced modulated waveform measurement system for the robust characterization of microwave devices under modulated excitation

Abstract: This paper presents a refined modulated waveform measurement system for the robust characterization of nonlinear microwave devices when driven by broadband multi-tone stimuli. This enhanced system has the ability to present specific, constant impedances, not only to a large number of baseband (IF) components, but also to signals located around the carrier and significant harmonic frequencies. Achieving such comprehensive impedance control across wide modulation bandwidths is critical in allowing the ‘emulation’ of new power amplifier modes and architectures, and the subsequent waveform characterization of devices operating in these complex and often dynamic impedance environments. The enhanced system is demonstrated through a number of applications: firstly the experimental investigation and baseband optimization of a 10W GaN HEMT under nine-tone excitation, and secondly, the emulation of a modulated Class-J impedance environment that interestingly highlights the presence of separate optimum baseband impedance conditions necessary for the reduction of individual IM products.

A 100-GHz balanced FET frequency doubler in 65-nm CMOS

Abstract: This paper demonstrates a W-band CMOS frequency doubler which utilizes a balanced topology in order to achieve a wideband fundamental suppression. The required 180-degree phase shift is obtained by employing a spiral transmission line balun. At 100 GHz the measured conversion loss of the frequency doubler is 16 dB using an input power of +5 dBm. The fundamental suppression is better than 25 dB from 42 to 55 GHz.

Wide band high-efficiency power amplifier design

Abstract: This paper presents a hybrid (passive & active) power amplifier concept for a wideband high drain efficiency power amplifier design. The proposed design integrates for the first time a dual-band PA with an active second harmonic injection to achieve high efficiency across a continuous wideband frequency range of two octaves. The design utilizes a resistively loaded class B at the lower frequencies and a class J mode of operation at the upper frequency band. To maintain high efficiency during the transition between the two PA modes an active second harmonic injection at the output of the main transistor is employed through an addition of an auxiliary low power amplifier. To demonstrate the validity of the novel concept a demonstrator is realized around a 10 W GaN transistor with an average efficiency of 63% across 0.6–2.4 GHz at only modest gain compression of 1dB.

Stabilisation approach for multi-device parallel power amplifiers under large-signal regime

Abstract: This paper describes a method for the detection of instabilities and their stabilisation under large-signal regime in multi-device paralleled power amplifiers. The symmetry of the amplifier is exploited for a simple and effective characterisation of odd- and even-order modes, and their reduction to equivalent single-transistor amplifiers. The nonlinear stability is then assessed by use of the conversion matrix. Examples of application are also given.

DC (10 Hz) to RF (40 GHz) output conduction extraction by S-parameters measurements for in-depth characterization of AlInN/GaN HEMTS, focusing on low frequency dispersion effects

Abstract: A test bench allowing S-parameters measurements from 10 Hz to 40 GHz has been set-up, this set-up has been used to investigate the DC to RF behavior of AlInN/GaN HEMTS. The measurement performed have demonstrated the dispersion effects observed on GaN HEMTS due to trapping effects and proved very useful for in-depth characterization of RF devices.

Advanced RF characterization of new planar high sensitive zero-bias Schottky diodes

Abstract: New zero-bias Schottky diodes with low junction capacitance and low differential resistance are characterized by applying DC and S-parameter measurements from 65–110 GHz. Diode versions with short and open circuits at the diode's anode as well as biased measurements of the diode allow an advanced investigation to model the diode's equivalent circuit. The extracted parameters provide an accurate RF model for nonlinear circuit simulations to design and realize diode detectors for direct detection receivers.

I-DLTS, electrical lag and low frequency noise measurements of trapping effects in AlGaN/GaN HEMT for reliability studies

Abstract: GaN technologies have penetrated the microelectronic markets, proving the high potential of this technology for a wide variety of applications (optoLEDs and Laser, power and RF electronics). However, robustness of these widebandgap technologies still needs to be improved: a large number of studies have addressed the main different roots provoking degradation of RF, DC or thermal performances of transistors dedicated to high frequency applications. Experiencing reliability studies mechanisms on a given technology cannot be carried out to another one, depending on changes of the doping, passivation layer thickness or material, content of Al or In in the ternary composition of the channel… Among the more problematic causes of degradation for high electron mobility transistors (HEMT), traps need to be accurately identified: this paper proposes the jointed expertise using three different experimental workbenches to identify trapping-detrapping effects and free charges effects in AlGaN/GaN HEMT devices over samples from a European foundry. Different samples have been stressed using DC biased devices at ambient temperatures of 25°C and 150°C, and using HTRB stresses at 150°C. Stressed devices and virgin samples are measured using pulsed I-V characterizations, current Deep Level Transient Spectroscopy (I-DLTS) measurements and low frequency noise (LFN) measurements. Each experimental setup has its own specificities, and allows the determination of activation energies and capture sections of the traps, or how these traps or charges affect the transistor performance under realistic HF conditions. Drain-Lag and Gate-lag signatures evidence the large stress effect on the devices, but with different nuances partially correlated to gate leakage currents. Traps measured with I-DTLS and LFN techniques evidence partially correlated origins, and thermally activated traps can be discriminated from electrically activated ones.

Analysis and design of dual-band GaN HEMT based Doherty amplifier

Abstract: A dual-band Doherty amplifier architecture is proposed and analysed. The amplifier architecture comprises a modified output combining network which results in a compact and effective design. For verification, a dual-band Doherty power amplifier (PA) was designed and implemented. Large-signal measurements highlighted the dual-band Doherty behavior of the designed PA with 6-dB output back-off efficiencies of η=49 % and η=44 %, measured at 2.0 GHz and 2.72 GHz, respectively. The designed Doherty PA was also tested with Universal Mobile Telecommunications System (UMTS) and Long Term Evolution (LTE) signals. Adjacent-channel leakage ratio (ACLR) levels of −44 dBc and −40 dBc were achieved at 2.0 GHz and 2.72 GHz, respectively, using digital pre-distortion (DPD) linearization. The corresponding efficiencies at 2.0 GHz and 2.72 GHz were η=46 % and η=37 %, respectively, with average output power of 36 dBm.

High performance GaN front-end MMICs

Abstract: Key GaN HEMT front-end circuits for next generation AESA radar/EW applications are presented. The circuits are an S-band 20 W MMIC HPA reaching 50 % measured PAE, a two-stage S-band MMIC LNA showing a measured NF of 1.3 dB, and a DC-18 GHz SPDTs showing a measured insertion loss of less than 2 dB at 18 GHz. Furthermore, a 2–18 GHz front-end circuit with a co-integrated two-stage LNA and a T/R-switch has been designed as an example of an integrated multi-functional GaN front-end circuit. The circuits were manufactured in the Chalmers AlGaN HEMT on SiC MMIC process. The process includes both 0.25 μm and 0.15 μm gate-length devices.

X-band 200W AlGaN/GaN HEMT for high power application

Abstract: A 200 Watts GaN high electron mobility transistor (HEMT) has been developed for X-band applications The device consists of four dies of 035 um-gate GaN HEMT of 16 mm gate periphery together with input and output 2-stage impedance transformers assembled into a low thermal resistance package The developed GaN HEMT provides 204W output power and 12dB small signal gain at 93 GHz with power added efficiency of 32% under pulse condition at a duty of 10% with a pulse width of 100 usec

Harmonically tuned GaN-HEMT Doherty power amplifier for 6 GHz applications

Abstract: In this paper a GaN-HEMT Doherty amplifier targeted for vehicular applications at 6 GHz is presented. The harmonic tuning of the selected bare-die transistors was investigated and implemented in order to improve the overall large-signal performance. The Doherty amplifier was studied and optimized on device reference plane level using two equally sized 8-Watt GaN devices for the main class-AB and the peaking class-C amplifiers. The measured maximum output power was 41.5 dBm with 63 % peak drain efficiency (50 % power added efficiency). At 6 dB output power back-off a drain efficiency of 49 % (42 % power added efficiency) was obtained. The linearity of the amplifier was tested by applying modulated signals according to the IEEE 802.11p standard. At 34 dBm average output power a drain efficiency of 43 % was achieved for this high dynamic range OFDM signal. After digital pre-distortion, the related adjacent channel power ratio could be reduced from −31 dBc to values below −43 dBc without significant impact on the efficiency performance.

Low phase noise 77-GHz fractional-N PLL with DLL-based reference frequency multiplier for FMCW radars

Abstract: Two architectures of 77-GHz fractional-N phase-locked loops (PLLs) for FMCW radars are presented. Both architectures show good performance in terms of phase noise with −79 dBc/Hz at 100 kHz offset frequency. To achieve this, the integration of a delay-locked loop-based frequency multiplier for the reference signal in the PLL is proposed. It exhibits very low phase noise and proves to be an excellent alternative to other types of multipliers for lower frequencies.

Comparison of low-frequency and microwave frequency capacitance determination techniques for mm-wave Schottky diodes

Abstract: The differences of low-frequency (1.0 MHz) and high frequency (3–10 GHz) capacitance determination techniques are compared in this work. The low-frequency measurements are direct capacitance measurements performed with an LCR meter and the capacitance determination at microwave frequencies is done by extracting the capacitance from S-parameter measurement results. Several discrete and monolithically integrated Schottky diodes are measured with both techniques and the differences of the techniques are discussed in the view of the obtained results. An evaluation is made on which technique is better suited for building a valid capacitance model for a Schottky diode operating at millimeter wave frequencies.

Figures of merit and performance measurements for RF and microwave tunable matching networks

Abstract: RF and microwave tunable matching networks (TMNs) development is quickly growing as increasing their interest and demand for applications in wireless and mobile communication systems. Although this topic has been extensively reported in the literature in the last years, there are still some unclear issues regarding the performance measurements and the best figures of merit to accurately characterize these circuits. In this paper, we present an overview of some usual metrics with their pros and cons, focusing mainly in the Smith chart coverage concept and in the losses definition. We also introduce the concept of TMN gain. To illustrate this study, we will use a fabricated and measured TMN based on silicon-glass PIN diodes as switching elements.

Linearization of two-way Doherty amplifier

Abstract: In this paper two-way Doherty amplifier with the additional circuit for linearization has been realized and measurements of the linearization influence to the third-and fifth-order intermodulation products have been carried out. The linearization approach uses the fundamental signals' second harmonics and fourth-order nonlinear signals that are extracted at the output of peaking cell, adjusted in amplitude and phase and injected at the output of the carrier cell in Doherty amplifier.

300 GHz active frequency-tripler MMICs

Abstract: An active frequency-tripler MMIC achieving an output frequency of 315 GHz is presented. Without the use of post-amplification the frequency-tripler generates an average output power of −10.1 dBm in the output frequency range from 285 to 315 GHz. At 303 GHz the measured output power is −9.3 dBm with an input power of 10 dBm. The comparison to the simulated results shows the quality of the underlying large-signal mHEMT models. The MMIC is realized in a metamorphic HEMT technology with 50 nm gate-length and uses only 0.5 × 0.75 mm2 of chip space for convenient integration into multifunctional MMIC circuits. An integrated version with output buffer amplifier is presented generating −0.5 dBm of output power at 288 GHz.