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This paper presents a universal hardware platform (UHP) based on software defined radio (SDR) technology and developed to accelerate the prototyping and testing new hardware and algorithmic solutions for modern radio systems. There are two integrated transceivers and a baseband processor on the board. Thus, four complete RF transmitting and receiving channels, with observation paths for transmitted signals monitoring could be supported. Our platform can be operated in both time-division (TDD) and frequency-division (FDD) duplex schemes over a 300 MHz to 6 GHz frequency range with simultaneous synthesis and analysis in the bandwidth of up to 100 MHz. The radio system is formed by attaching an appropriate RF front-end to the UHP and uploading standard-specific software. As examples of possible UHP applications, two LTE-Advanced micro base stations for private networks with standard-defined RF front-ends operating in the LTE band B43 (3.6 GHz) with time duplex and the band B31 (450 MHz) in FDD mode are presented.

The paper presents the results of studies on the effect of transistor DC operating conditions on GaN power amplifiers’ (PAs) power efficiency and linearity improved by digital predistortion (DPD). The single-ended 10 W (ISM2.45 GHz) and 150 W (3.4/3.6 GHz) GaN HEMT PAs excited by wideband LTE20 E-TM1.1 signal were tested. To check the applicability of the small-signal approach for designing of LTE signals’ PAs, the 150 W PA using transistor model extracted from S-parameters measured at the properly selected operating points was designed. The conventional DPD based on the indirect learning architecture and the memory polynomial model of PA non-linearity was implemented. The results of the research show that in case of class A and B PAs operating up to several dozen watts, an additional improvement in adjacent channel leakage ratio (ACLR) of the order of a few dB only by an increase in the quiescent drain current of PA transistor can be achieved. However, a noticeable ACLR improvement with a coincident increase in power-added efficiency (PAE) can be obtained by choosing the compromise DC operating point and using DPD. In the case of high-PAs, the linearity and efficiency are strongly dependent on the load of a transistor, thus the role of DPD is significantly increased.

This paper describes the development of a power amplifier operating over a 2.4–2.5 GHz frequency range with the output power level more than 15 W and 60% PAE. The transistor applied was the 10 W (13 W Psat) power GaN HEMT (CGH40010F from Wolfspeed) recommended up to 6 GHz. A harmonic tuning method was used to achieve even 30% more output power than the CGH40010 transistor was specified to deliver while maintaining high gain and high efficiency. Furthermore, an accuracy analysis of amplifier design was also conducted. It included validation and correction of the available transistor models as well as validation of the models of microstrip circuits implemented in ADS. Finally, it was concluded that both the mentioned sources of errors contributed at a similar level.

In the paper RF performances and thermal features of GaN HEMTs grown on Si substrate for the design of microwave high-power amplifiers have been briefly presented referring also to the state of the art of the dominant GaN-on-SiC HEMT technology. As GaN-on-Si HEMT application examples driver and final stage amplifiers with high-voltage NPT2018 and NPT2022 transistors made by MACOM were designed and experimentally verified. The amplifiers operate over a 1.2 GHz to 1.4 GHz frequency range with saturated output power nearly 42 dBm and 51 dBm, respectively, at the power added efficiency more than 60%.

High performance GaN-based high electron mobility transistors (HEMTs) on SiC require low-miscut (~0.45°), resistive substrates, which are very expensive. A cost-effective solution is to use resistive SiC template i.e., grow a thick resistive SiC epitaxial layer on cheap, conductive SiC substrate. However, this approach requires much higher miscut (2–8°). In the present work we show a lateral patterning technology capable to locally decrease the high miscut of the resistive SiC template, down to a level acceptable for GaN epitaxy. On such patterned SiC templates we grew smooth AlGaN/GaN structures. The maximum width of flat regions available for device fabrication was nearly 100 µm. In these flat regions AlGaN-based HEMTs were fabricated and characterized.

Gallium Nitride and Related Wide-Bandgap Semiconductors (WBS) have constantly received a great amount of attention in recent years [...]

Power amplifiers applied in modern active electronically scanned array (AESA) radars and 5G radios should have similar features, especially in terms of phase distortion, which dramatically affects the spectral regrowth and, moreover, they are difficult to be compensated by predistortion algorithms. This paper presents a GaN-based power amplifier design with a reduced level of transmittance distortions, varying in time, without significantly worsening other key features such as output power, efficiency and gain. The test amplifier with GaN-on-Si high electron mobility transistors (HEMT) NPT2018 from MACOM provides more than 17 W of output power at the 62% PAE over a 1.0 GHz to 1.1 GHz frequency range. By applying a proposed design approach, it was possible to decrease phase changes on test pulses from 0.5&deg, to 0.2&deg, and amplitude variation from 0.8 dB to 0.2 dB during the pulse width of 40 &micro, s and 40% duty cycle.

The paper presents the test results of transmittance deviation during pulses of GaN HEMT and GaAs MESFET power amplifiers designed for T/R modules of Active Electronically Scanned Array (AESA). The study is based on pulsed measurements of transmittance deviation using Vector Network Analyzer (VNA) triggered by external signal generator. As an example of power amplifier for T/R module, the X-band 9W amplifier with GaN HEMT chip was designed.

The paper presents the results of laboratory studies on influence of DC transistor operating conditions both on power amplifier (PA) linearity and effectiveness of digital predistortion procedure. The impact of DC operating conditions of 10 W GaN HEMT power amplifier on nonlinearity factors without and with digital predistortion (DPD) were investigated. The obtained results show that there is an additional improvement in adjacent channel leakage ratio (ACLR) of the order of a few dB only by an increase in the quiescent drain current of PA transistor. However, some noticeable improvement of ACLR with significant increase in PA power added efficiency (PAE) is obtained for PA with digital predistortion.

The paper presents the amplifier for application in an active electronically scanned array (AESA). For design purposes both time- and frequency domain simulations were carried out. The developed amplifier achieved more than 9W of output power at a maximum efficiency of 57% for 9.5 GHz and small-signal gain |S21|>11dB over 9-10 GHz frequency range. Furthermore, the potential of Polish GaN HEMT technology based on domestic, semi-insulating, bulk GaN substrate fabricated by Ammono.

This paper is related to the project of an ultrawideband radio receiver operating between 1 and 6 GHz with instantaneous bandwidth of 500 MHz. A single frequency conversion (0-IF) architecture is based on analog I/Q demodulator (ADL5380) and two channel 14-bit analog-to-digital converter (AD9680). Preliminary measurements of the receiver have been performed and presented in the paper. Key results include: noise figure NF 21 dBm.

The paper presents the results of a project leading to design and fabrication of a transmitting-receiving module destined for application in an active electronically scanned array (AESA). The module is supposed to operate in the band from 9 GHz to 10 GHz. GaAs technology core chip is applied and it is used to drive power amplifiers based on GaN technology. The shape of the module enclosure follows the requirements of limited space available in an X-band AESA.

This paper presents a microstrip dual-band bandpass filter (BPF) based on cross-shaped resonator and spurline. It is shown that spurlines added into input/output ports of a cross-shaped resonator generate an additional notch band. Using even and odd-mode analysis the proposed structure is realized and designed. The proposed bandpass filter has dual passband from 1.9 GHz to 2.4 GHz and 9.5 GHz to 11.5 GHz.

An ultra-wideband (UWB) bandpass filter (BPF) with two reconfigurable notch bands is proposed, based on cross-shaped resonator (CSR) without using coupled line structure. With the use of even and odd-mode approaches, the proposed UWB bandpass filter bandwidth is from 2.8–10.9 GHz, with 118% fractional bandwidth (FBW), and the dual reconfigurable notch bands is tuned from 4–5.3 GHz, and 7.9–8.8GHz.

A Computer-controlled System of High-power Microwave Sources The paper presents the design and hardware implementation of a computer controlled system composed of up to four high-power microwave sources. Each source provides up to 200 W of continuous wave power. Frequency of each source is stabilized within ±0.5 ppm of the nominal frequency adjustable within 2.35 ÷ 2.6 GHz range. All four sources can be synchronized to the same frequency with computer-controlled phase shift between the signals generated by each of them. The paper concentrates on the choice of components for such a system and the properties of the realized hardware implementation.

A 100 W SiC MESFET Amplifier for L-band T/R Module of APAR In the paper, a 100W SiC MESFET amplifier design dedicated for a L-band T/R module of APAR is presented. The output power higher than 100 W has been achieved by combining in a balanced configuration two single stages with Cree's 60 W CRF24060 SiC MESFETs. The amplifier design methodology is based on the small-signal model and DC characteristics of SiC MESFET. The model is extracted using the transistor S-parameters at three operating points for On-state, Off-state and normally biased. The measurements and simulations prove usefulness of the proposed design method. The amplifier was excited with pulsed and cw signals for the case temperature ranging from 60°C to 140°C. As a result of the case temperature changes the output power drop was lower than 0.5 dB at the level of 150 W.

27 dBm Microwave Amplifiers with Adaptive Matching Networks The paper describes adaptive amplifier design with varactors and pin diodes as regulators of matching networks. As examples the two amplifiers with SHF-0189 HFET transistor and different matching sections were designed and manufactured. The output power level of 27 dBm and gain higher than 13 dB within L and S-band have been achieved. The amplifier design methodology is based on the small-signal approach and DC characteristics of transistors and regulators. Amplifier adaptivity allows us to remotely control the chosen parameters such as: frequency range, output power level, gain and etc.

AlGaN/GaN high electron mobility transistors on semi-insulating bulk ammonothermal GaN have been investigated. By application of regrown ohmic contacts, the problem with obtaining low resistance ohmic contacts to low-dislocation high electron mobility transistor (HEMT) structures was solved. The maximum output current was about 1 A/mm and contact resistances was in the range of 0.3&ndash, 0.6 &Omega, &middot, mm. Good microwave performance was obtained due to the absence of parasitic elements such as high access resistance.

In this paper a 250W solid state RF Pulse Power Source (PPS) operating over a 2995MHz to 3001MHz frequency range with only 100Hz frequency step and from 5.6μs to 8.4μs pulse width at the duty cycle below 0.5% is presented. The device was optimized to deliver the synchronized high-frequency-stability RF pulse for Linear Accelerator processing. The pulse power level can be controlled within 18dB dynamic range with power drop during the pulse less than 0.3dB. The phase noise level and long-term stability including VCO pulling effect of the synthesized RF signal is below -85dBc/Hz@1kHz and less than 0.2ppm, respectively. The advanced reconfiguration, diagnostic and protection features built into the RF pulse source are remotely controlled via Ethernet.

AlGaN/GaN high electron mobility transistors (HEMTs) seem to dominate the market and research in the area of high-power RF technology. The dominant substrate material for GaN epitaxy is SiC. The 3.5% lattice mismatch between GaN and SiC is relatively small but still may be a considerable source of lattice defects. The main reason for use of foreign substrates was for years, lack of high quality GaN wafers. However, recently it came a breakthrough in this field. A leading GaN substrates manufacturer, Ammono S.A., has shown 2” truly bulk highly-resistive GaN wafers grown by ammonothermal method. The next key problem related to the use of foreign substrates is a management of the heat transfer inside multilayer epitaxial structure of GaN HEMTs. Due to the reliability and performance issues, this aspect is especially important for high power devices. While the thermal conductivity of 4H-SiC is higher than for GaN, the heat flow inside typical GaN HEMT on SiC substrate is significantly limited because of presence of buffer or nucleation layers (e.g. AlN) between epilayers and SiC substrate. That effect is commonly called thermal boundary resistance (TBR). Dislocations at the interfaces have a large share in the TBR. It can be generalized, that buffer layers grown on the other substrates that GaN have a significant contribution to total thermal resistance of GaN HEMT. In case of AlGaN/GaN structure grown on the bulk gallium nitride, the thermal resistance of GaN HEMT is only determined by the conductivity of bulk GaN. This paper presents first AlGaN/GaN HEMT structures prepared on novel generation Ammono-GaN semi-insulating substrates. Such substrates characterized by FWHM value of X-ray rocking curve 20 arcsec, curvature radius of several tens of meters, and dislocation density 2x104 cm-2 were chosen for epitaxial growth of GaN-based semiconducting thin film materials by MOCVD method on c-plane. The HEMT epitaxial structure consisted of 1 nm GaN-cap, 27 nm Al0.27Ga0.73N barrier layer, 0.8 nm AlN spacer, and 3 μm unintentionally doped GaN layers. High resolution 2θ-ω and rocking curve XRD scans of HEMT structure prove excellent crystal quality of epilayers grown on Ammono-GaN with FWHM=0,0090o. Sheet resistivity, sheet carrier concentration and Hall mobility were 417 Ω/□, 1.23×1013 cm-2, 1308 cm2/Vs, respectively. Fabrication of transistors starts by formation of ohmic contacts by using the regrown n+-GaN:Si layers. Isolation of adjacent devices was done by using Al+ double ion implantation. By this approach the contact resistance Rc of 0.3-0.6 Ωmm was obtained. The fabricated transistors had rectangular Ni/Au gate with 0.8µm length and 2x200 µm width. The source to gate and gate to drain distance was 1.2 and 4 µm respectively. The devices were passivated by 100 nm SiNxlayer deposited by PECVD. Finally, contact pads were opened and thickened by Au deposition. The transistor was designed as a test fixture and its topology was adapted to requirements of the "on-wafer" measurement station Cascade M150. The measurements performed have shown that the maximum output current density of fabricated transistors reaches 1000 mA/mm at VGS=2V. The extracted on-state resistance Ron is 4.4 Ω/mm. Transistor transconductance is about 220 mS/mm and reaches maximum value for the expected range of operating points of transistors. No measurable leakage current through the buffer layers or the substrate has been observed. The frequency performances of fabricated transistors were evaluated by measuring the S-matrix parameters over 45 MHz to 24 GHz frequency range at quiescent point VDSQ=28V and IDSQ=46 mA. The maximum frequency (fmax) and cut-off frequency (fT) was 30 GHz and 21 GHz as obtained by linear extrapolation with -20dB/dec slope of unilateral gain (U) and small-signal current gain |H21| characteristics. The insertion gain |S21| attain 0dB for frequency (fs) of 22 GHz. The maximum available gain (MAG) and |S21| was 22.7 dB and 15.3 dB at 2GHz and 19.8 and 12.7 dB at 4 GHz. The microwave measurements indicate the lack of significant parasitic elements and confirm the high quality of fabricated HEMTs. In overall the GaN HEMT transistor manufactured on a truly bulk monocrystalline GaN wafer was shown to have similar parameters as the ones manufactured on a SiC wafer available from a leading commercial manufacturer. In particular we have obtained similar current densities and thermal resistivity. The frequency characteristics were limited mostly by a relatively long gate resulting from application of the photolithography. That limitation is expected to vanish in the planned next round of experiments were electron-lithography is to be applied. The research was supported by the National Centre for Research and Development PolHEMT Project, Contract Number PBS1/A3/9/2012.

Split post dielectric resonators (SPDR) are commonly used for measurements of complex permittivity and losses measurements of many materials. The permittivity of the sample is calculated basing on the change in a resonance curve of the loaded and unloaded SPDR. The paper presents an inexpensive replacement for Vector Network Analyser normally used to determine the resonator's Q-factor. The proposed system is recommended for those customers, who don't need such rich-featured equipment as VNAs.

In this paper an approach to modeling of TO-39 packages employed for IR detectors wirebonded to the package leads is discussed. The presented approach is based on measurements of a real package in which the detector chip was replaced with a 2-port of known parameters (a microstrip line of length equall to that of the original chip) and connected to the package leads with wirebonds. In this respect the presented procedure differs from the literature reports, which concentrate mostly on indirect package characterization based solely on full-wave EM models of the packages. The sensitivity of the approach to varying lengths of the wirebonds used to connect the known 2-port to the package is analyzed. To this end, the structure was wirebonded several times. Each time it was measured so that the discrepancy in extracted parameters of the package equivalent circuit could be observed.

This paper describes the development and implementation of a Programmable RF (Radio Frequency) Transmitter operating with quadrature obtained modulation schemes over a 2 GHz-2.4 GHz frequency range. The transmitter based on SDR (Software Defined Radio) architecture with Zero-IF up-conversion method is designed for testing wireless system transmission paths. The RF measurement methods and features used for evaluation of modern radio devices in particular P-MP (Point to Multipoint) communication system along with related ETSI standards are considered. The measurements results of 2.4 GHz PAs (Power Amplifiers) and 2.4 GHzharr3.5 GHz Transverter are presented.

This paper describes project of 4 W and 30 W power amplifiers worked out for Top Amplifier Research in European Team (TARGET) project in the confines of Sixth Framework of Programme Network of Excellence (NoE). The amplifiers based on the pHEMT and LDMOS transistors were designed over 890 to 915 MHz and 1850 to 1880 MHz respectively. The main aim of the project is to investigate and evaluate the existing skills basis and resources for designing and prototyping of complete power amplifiers.

The paper describes development of a technique and equipment to convert signals from TDD or FDD radio systems operating over popular ISM 2.4 GHz-band up to the less crowded, licensed 3.5GHz or 4.4GHz bands. The technique of bands conversion consists in a connection to the existing infrastructures RF up/down converter modules (transverter) with T/R switches or duplexer for TDD or FDD systems, respectively. Currently, the 3.5GHz FDD transverters cooperate in 17 locations with the IRT2000 digital radio access system used by El-net NETIA group and 4.4GHz TDD transverters work together with 802.11b WLAN AP utilized by Military Communication Institute.

The paper presents the concept and the performances of the L- and C-band T/R module for an active phased array radar (APAR). The transmitters were optimized for minimum transmittance distortions and maximum output power level. The method used was based on a self-invented electro-thermal MESFET model. The receivers were optimized with respect to the minimum noise figure and maximum resistance for the input power. The most important parameters of the T/R modules are as follows: L-band with P/sub out/ = 100 W, /spl Delta/|T

This paper describes development of thermal LDMOS model based on the solution of heat conducting equation (HCE) by means of 3D FDTD thermal method. This thermal analysis co-operates with electrical LDMOS model implemented in Agilent's program (ADS). The elaborated temperature-dependent microwave LDMOS model will be used to design high power amplifiers for transmitters of radar (APAR) and radiocommunication systems.

This paper describes the structure and the performance of a 300 W compact solid-state transmitter operating over 2.9 to 3.1 GHz, for radar and medical applications. The transmitter consists of three major parts: PLL-DDS synthesizer, pulse shaping circuit and multi-stage class-C amplifier. A 300 W peak power with a pulse width up to 50 /spl mu/s and 5% duty cycle was achieved by combining two 160 W amplifiers with Si-BJT using a balanced configuration. The output power level is controlled in 6 dB dynamic range by means of a DC supply block. The power droop during RF-pulse is less than 0.2 dB for 5% duty operation in the whole output power dynamic range. The synthesized VCO achieves more than 10/sup -7/ long-term stability including pulling effect and -75 dBc/Hz@1 kHz phase noise. In addition the spectrum requirements are also satisfied.

In the paper a high power amplifier with gain of 11 dB and output power of 46.5 dBm for an L-band T/R module is described. Use of a class A amplifier with silicon bipolar transistors reduces nonlinear distortion of the signal.

High power noise sources for L and S band with controlled power level were designed. The source output power for L-band is P=12 W and for S-band P=10 W in wide 14% band. The dynamic of power control exceeds 20 dB and flatness is 1 dB. The drop of power outside band is 5 dB/10 MHz for the L-band source and 3 dB/10 MHz for the S-band source.

A method of limitation of the transmittance deviation during the RF pulse of power amplifiers for the T/R module of active phase array radar is described. The method is based on the load-pull technique and is examined using a GaAs MESFET transistor.

A balanced high-power amplifier with class A silicon bipolar transistors for an L-band T/R module for active phased array radar is described. The amplifier was designed for maximum power and minimum transmittance distortion. The obtained parameters of the amplifier are as follow: output power at 1dB compression P/sub 1 dB/>49 dBm, linear gain |S21|>10 dB, and transmittance deviations during the RF pulse: phase /spl Delta/arg(S21)

The design and performance of a waveguide-to-microstrip transition is presented. The optimum bilateral finline taper has been used to match the fundamental mode waveguide characteristic impedance to a 50-ohm micro-strip mounted on a low dielectric substrate. The transverse resonance method has been applied to calculate characteristic impedance of bilateral finline taking into consideration the finite metallization thickness and substrate holding grooves. The experimental results of X-band transition are also given.

This paper describes development of solid-state microwave power test system (MPTS) operating over 2.3 to 2.6 GHz with the output power level of 100 W for industrial applications in material processing, and for designing of microwave power industrial equipment. The MPTS unit consists of four major parts: PLL synthesizer, high power solid-state amplifier, detector probes for return losses and leakage measurement and microcontroller. The MPTS system is able to operate in either single fixed-frequency regime, or in swept mode with self-tuning for minimum reflection of a heated load.