In this paper, an extended version of the continuous class-F-1 mode power amplifier (PA) design approach is presented. A new formulation describing the current waveform in terms of just two additional parameters, while maintaining a constant half-wave rectified sinusoidal voltage waveform, allows multiple solutions of fundamental and second-harmonic impedances that provide optimum performance to be computed. By varying only the imaginary parts of fundamental and second-harmonic impedances, it is shown that output performance in terms of power and efficiency is maintained constant and equal to that achievable from the standard class-F-1 . Indeed, when presenting resistive second-harmonic impedances, it will be demonstrated that the fundamental load can be adjusted to maintain satisfactory output performances greater than a certain predetermined target value. The measurements, conducted on a GaAs pHEMT device at 1 GHz, show a good agreement with the theoretical analysis, revealing drain efficiencies greater than 70% for a very large range of load solutions, which can translate to an ability to accommodate reactive impedance variations with frequency when designing broadband PAs.

The Continuous Inverse Class-F Mode With Resistive Second-Harmonic Impedance

This paper presents an X-band bi-directional T/R chipset in 0.13 m CMOS. The T/R chipset consists of a bi-directional gain amplifier (BDGA), a 5-bit digital step attenuator with two BDGAs for compensating the switch losses, and a 6-bit phase shifter using DPDT switches. The phase and attenuation coverage is 360 with the LSB of 5.625°, and 31 dB with the LSB of 1 dB, respectively. The circuit has a reference state gain of >;3.5 db, and the return losses of >;11 db at 8.5-10.5 GHz. The T/R chipset has a phase shift accuracy with the RMS phase error of ;6.5 dBm and the noise figure is <;7.5 db at 8.5-10 GHz. The chip size is 2.06 × 0.58 mm2 including pads, and the DC power consumption is 154 mW only in the BDGAs. To authors' knowledge, this is the X-band CMOS T/R chipset with the competitive RF performance compared to other device technologies, which has the smallest size and the lowest power consumption to-date.

A Compact X-Band Bi-Directional Phased-Array T/R Chipset in 0.13 $\mu{\hbox {m}}$ CMOS Technology

A MMIC process in AlGaN/GaN technology for advanced transceiver design has been developed. The process is based on microstrip technology with a complete model library of passive elements and AlGaN/GaN HEMTs. The transistor technology in this process is suitable for both power and low noise design, demonstrated with a power density of 5 W/mm, and an NFmin of 1.4 dB at X-band. Process stability of subcircuits, complementary to power amplifiers and LNAs, in a transceiver system have been investigated. The results indicate that an all AlGaN/GaN MMIC transceiver is realizable using this technology.

An AlGaN/GaN HEMT-Based Microstrip MMIC Process for Advanced Transceiver Design

The high-frequency noise performance of the GaN HEMT is studied for temperatures between 297-398 K. The access resistances RS and RD have a limiting effect on the noise performance, and in this paper, their temperature dependence is studied in detail for a 2 times 100 mum GaN HEMT. RS and RD show an increase of 0.71 and 0.86 %/K, respectively. The self-heating effect due to dissipated power is also studied to allow accurate intrinsic small-signal and noise parameter extraction. The thermal resistance is measured by infrared microscopy. Based on these results, a temperature dependent noise model including self-heating and temperature-dependent access resistances is derived and verified with measurements.

Thermal Study of the High-Frequency Noise in GaN HEMTs

This paper presents a monolithic microwave integrated circuit multifunction chip implemented using a 0.25- $\mu \text{m}$ gallium arsenide pseudomorphic high-electron-mobility transistor process for use in a phased array jammer transmitter. This chip, which operates in the frequency range of 6–18 GHz, provides several functions including 8-bit true time delay (TTD), 7-bit attenuation, wideband amplification, and digital serial-to-parallel conversion for 15-bit control. The TTD and attenuation coverage are 255 ps with a step of 1 ps and 31.75 dB with a step of 0.25 dB, respectively. The TTD employing an artificial transmission line configuration demonstrates a root-mean-square delay error of less than 1.7 ps in the operating frequency range. The chip has a compact size of $4\,\,\hbox {mm} \times 5$ mm and exhibits a typical gain of 12 dB and an output P1dB of 16.5 dBm over a frequency range of 6–18 GHz.

A 6–18-GHz GaAs Multifunction Chip With 8-bit True Time Delay and 7-bit Amplitude Control

This paper presents measurement results of a monolithic microwave integrated circuit (MMIC) chip set and of an ultra-wideband high power amplifier (HPA) transmit module for multi-functional next-generation active electronically scanned antenna radar/electronic warfare/communication applications targeting the frequency range from 6 to 18 GHz. The reported chip set consists of a driver amplifier (DA) MMIC and an HPA MMIC on a high-power gallium-nitride process with high electronic-mobility transistors. The DA reaches a power gain of 11 dB and maximum output power of 2 W, which is sufficient to drive a final stage in a balanced configuration. The HPA reaches a typical output power of 12.5 and 10.6 W in pulsed and continuous wave (CW) operation, respectively. Measurements on the module level indicate 18.5-W typical output power in both pulsed and CW operation.

Ultra-Wideband GaN MMIC Chip Set and High Power Amplifier Module for Multi-Function Defense AESA Applications

Amplifiers for a next generation of T/R-modules in future active array antennas are realized as monolithically integrated circuits (MMIC) on the bases of novel AlGaN/GaN HEMT structures. Both, low noise and power amplifiers are designed for X-band frequencies. The MMICs are designed, simulated and fabricated using a novel via-hole microstrip technology. Output power levels of 6.8 W (38 dBm) for the driver amplifier (DA) and 20 W (43 dBm) for the high power amplifier (HPA) are measured. The measured noise figure of the low noise amplifier (LNA) is in the range of 1.5 dB. A T/R-module front-end with mounted GaN MMICs is designed based on a multilayer LTCC technology.

GaN MMIC based T/R-Module Front-End for X-Band Applications

High power amplifiers for a next generation of T/R-modules for future X-band active array antennas are realized on the bases of novel AlGaN/GaN HEMT structures, which are epitaxially grown on SiC wafer substrates. Both, hybrid and monolithically integrated circuits are designed and realized as key elements for transmit chains. Based on hybrid designs excellent peak power levels of 23 W (43.6 dBm) with an associated power added efficiency (PAE) of 29% are realized. Over a bandwidth of 2 GHz (X-band) the output power levels are above 20 W. In a more sophisticated approach first monolithically integrated circuits (MMICs) are designed, simulated and fabricated using a novel via-hole microstrip technology. Output power levels of 20 W (43 dBm) with an associated PAE of 30% are measured on small size 12 mm2 chips. Highest ever reported maximum power added efficiency values of up to 36.5% are achieved

20W GaN HPAs for Next Generation X-Band T/R-Modules

After many years of development the active electronically scanned array (AESA) radar technology has reached a mature technology level. Many of today's and future radar systems will be equipped with the ASEA technology. T/R-modules are key elements in active phased array antennas for radar and electronic warfare applications. Meanwhile T/R-modules using GaAs MMICs are in mass production with high quantities. Top priority is on continuous improvement of yield figures by optimizing the spread of key performance parameters to come down with cost. To fulfill future demands on power, bandwidth, robustness, weight, multifunctional sensor capability, and overall sensor cost, new emerging semiconductor and packaging technologies have to be implemented for the next generation T/R-modules. Using GaN MMICs as HPAs and also as robust LNAs is a promising approach. Higher integration at the amplitude and phase setting section of the T/R-module is realized with GaAs core chips or even with SiGe multifunction chips. With increasing digital signal processing capability the digital beam forming will get more importance with a high impact on the T/R-modules. For lower production costs but also for sensor integration new packaging concepts are necessary. This includes the transition towards organic packages and using low cost surface-mount soldering technology.

http://ieeexplore.ieee.org/iel5/5606055/5614756/05616412.pdf

T/R-module technologies today and future trends

The next generation of AESA antennas will be challenged with the need for enabling a combination of different operating modes within the same antenna front end, including radar, communication (data links), and jamming (electronic warfare, EW). This leads to enhanced demands especially with regard to the usable RF bandwidth. One main step to overcome this is the use of disruptive semiconductor materials for RF MMICs. As the RF section of today's T/R modules for AESA applications is typically based on GaAs technology, GaN and SiGe BiCMOS will challenge or even replace it, here. This paper will describe the design of a GaN-based T/R module using all-European MMICs and covering the X-band from 8 to 12 GHz and its realisation at Airbus Defence and Space in Ulm. It will show some measurement results and give an impression on achieved performance. Further this paper shall describe potential next steps and give an outlook towards future developments.

P. Schuh

Papers

Ultra-Wideband GaN MMIC Chip Set and High Power Amplifier Module for Multi-Function Defense AESA Applications

GaN MMIC based T/R-Module Front-End for X-Band Applications

20W GaN HPAs for Next Generation X-Band T/R-Modules

T/R-module technologies today and future trends

GaN based wideband T/R module for multi-function applications