http://www.acsu.buffalo.edu/~jmjornet/papers/2014/j1.pdf

Full length article: Terahertz band: Next frontier for wireless communications

This paper reports on state-of-the-art millimeter-wave power performance of N-polar GaN-based metal–insulator–semiconductor high-electron-mobility transistors at 30 and 94 GHz. The performance is enabled by our N-polar deep recess structure, whereby a GaN cap layer is added in the access regions of the transistor to simultaneously enhance the access region conductivity while mitigating dc-to-RF dispersion. The impact of lateral scaling of the drain access region length is examined using the tradeoff between breakdown voltage and small-signal gain. Load-pull measurements are presented at 94 GHz, corresponding to the target device operating frequency in W-band, where the device demonstrated a peak power-added efficiency (PAE) of 28.8% at 16 V and record-high maximum output power density of 8 W/mm at 20 V. Additional load-pull measurements at 30 and 10 GHz demonstrate the viability of this device across a wide frequency range where the peak power remained constant at 8 W/mm and with peak PAEs of 56% and 58%, respectively.

Demonstration of Constant 8 W/mm Power Density at 10, 30, and 94 GHz in State-of-the-Art Millimeter-Wave N-Polar GaN MISHEMTs

This article reviews the state-of-the-art millimeter-wave (mm-wave) power amplifiers (PAs), focusing on broadband design techniques. An overview of the main solid-state technologies is provided, including Si, gallium arsenide (GaAs), GaN, and other III–V materials, and both field-effect and bipolar transistors. The most popular broadband design techniques are introduced, before critically comparing through the most relevant design examples found in the scientific literature. Given the wide breadth of applications that are foreseen to exploit the mm-wave spectrum, this contribution will represent a valuable guide for designers who need a single reference before adventuring in the challenging task of the mm-wave PA design.

/pdf/a-review-of-technologies-and-design-techniques-of-millimeter-wekhp9uz17.pdf

A Review of Technologies and Design Techniques of Millimeter-Wave Power Amplifiers

A method of using low-loss waveguide septum combiners is developed into a high-power -band (31-36 GHz) amplifier producing 50 W at 33 GHz (Ka-band) using 32 low-power (>2 W) solid-state amplifier modules. By using low-loss waveguide combining and a packaged monolithic microwave integrated circuit with a low-loss microstrip-to-waveguide launcher, the output loss is minimized, allowing for the overall power-combining efficiency to remain high, 80% (average insertion loss of combiner < 0.7 dB and average insertion loss of launcher <0.3 dB) over 31-36 GHz. In the past, lower power-combining efficiencies have limited the number of modules that can be combined at -band, and hence, have limited the power output. The approach demonstrated in this paper, with high power-combining efficiency, allows a very large number (32) of solid-state amplifier modules to be combined to produce high powers. Greater than 50 W was demonstrated with low power modules, but even higher powers 120 W are possible. The current approach is based on corporate combining, using low-loss waveguide septum combiners that provide isolation, maintaining the true graceful degradation of a modular solid-state amplifier system.

A High-Power $Ka$ -Band (31–36 GHz) Solid-State Amplifier Based on Low-Loss Corporate Waveguide Combining

This paper presents an octave-bandwidth load modulated balanced amplifier (LMBA) that operates directly on a single modulated RF input. The architecture is based on the recently proposed LMBA technique, in which a control signal applied at the output isolation port of a balanced amplifier is used to modulate the apparent load impedance of the two devices comprising the balanced amplifier. In our approach, the injected control signal is used both as an active match and to dynamically load modulate the main devices to provide efficiency enhancement at back-off, thus extending the dynamic range compared to the original LMBA formulation. In this paper, we introduce a phase-compensation technique through which the active matching and load modulation tracks the frequency-dependent optimal loading trajectory of a packaged device. The result is a load-modulation power amplifier architecture able to perform an active, modulated match over an octave bandwidth. The technique is demonstrated over 1.8–3.8 GHz using packaged devices and an off-the-shelf hybrid coupler. The proof-of-concept octave RF-input LMBA has a peak CW output power of 44 dBm, with power added efficiency (PAE) over the 1.8–3.8 GHz operating frequency range of 37%–59% at peak power and 29%–45% at 6-dB output backoff. The RF-input nature of this architecture enables straightforward measurement with modulated signals; a W-CDMA signal at 3.8 GHz with 9-dB (measured) peak to average power ratio is demonstrated with adjacent channel leakage ratio of −30 dBc and average PAE of 18% for a 31-dBm average output power (2-dB backoff).

RF-Input Load Modulated Balanced Amplifier With Octave Bandwidth

The design and performance of a K-Band Doherty amplifier MMIC is presented. The monolithic 2-stage amplifier was fabricated with a dual field plate 0.15um GaN on SiC HEMT process technology. Measured continuous wave results at 23GHz demonstrate over 5W of saturated output power and up to 48% power added efficiency. Peak efficiency occurs at approximately 1dB of gain compression and the amplifier maintains 25% power added efficiency at 8dB of input power back off from P1dB.

A K-Band 5W Doherty Amplifier MMIC Utilizing 0.15µm GaN on SiC HEMT Technology

The design and performance of two high efficiency Ka-band power amplifier MMICs utilizing a 0.15µm GaN HEMT process technology is presented. Measured in-fixture continuous wave (CW) results for the 3-stage amplifiers demonstrates 8–9W of output power for the balanced MMIC and 4.5–6W for the single-ended configuration. The associated power added (PAE) efficiency of both amplifiers exceeds 25% at Ka-band. The die sizes for the balanced and single-ended MMICs are 2.55×3.80mm2 and 1.39×3.42mm2 respectively.

High efficiency Ka-band power amplifier MMICs fabricated with a 0.15µm GaN on SiC HEMT process

The design and performance of two high efficiency Ka-band power amplifier MMICs utilizing a 0.15μm GaN HEMT process technology is presented. Measured in-fixture continuous wave (CW) results for the 3-stage balanced amplifier demonstrates up to 11W of output power and 30% power added efficiency (PAE) at 30GHz. The 3-stage single-ended design produced over 6W of output power and up to 34% PAE. The die size for the balanced and single-ended MMICs are 3.24×3.60mm2 and 1.74×3.24mm2 respectively.

/pdf/high-efficiency-ka-band-gallium-nitride-power-amplifier-59cwu0ixhx.pdf

High efficiency Ka-band Gallium Nitride power amplifier MMICs

This paper describes the design and measured performance of 16–40GHz power amplifier MMICs fabricated with an advanced state of the art 0.15µm Gallium Nitride (GaN) process technology. The process features a 50µm thick Silicon Carbide (SiC) substrate and compact transistor layouts with individual source grounding vias (ISV). The designs utilize a non-uniform distributed power amplifier (NDPA) topology with Ruthroff connected output transformers. The 3-stage single-ended amplifier demonstrates 4.1–8.7 W of output power over a 16–40GHz bandwidth. For the second MMIC two of the single-ended amplifiers are balanced to produce 7.0–16.0 W over the same frequency range.

Design and performance of 16–40GHz GaN distributed power amplifier MMICs utilizing an advanced 0.15µm GaN process

This paper describes the design and measured performance of two high efficiency Ka-band 32 - 38 GHz power amplifier MMICs fabricated with an advanced 0.15μm Gallium Nitride (GaN) HEMT technology process. The process features a 50μm thin Silicon Carbide (SiC) substrate and compact transistor layouts with individual source via (ISV) grounding. The designs utilize an optimum transistor arrangement with both single-ended and balanced approaches. The 2-stage single-ended power amplifier MMIC demonstrates 4.5 - 5.2 W of output power with 25 - 34% PAE over 32 - 38 GHz band. For the second MMIC, two 3-stage power amplifiers are combined to achieve 9.0 - 11.2 W output power with 30 - 35% PAE over the same frequency range. A benchmark of 1.45W/mm2 FOM (output power to die area ratio) with high efficiency is reported at this frequency band.

Sabyasachi Nayak

Papers

A K-Band 5W Doherty Amplifier MMIC Utilizing 0.15µm GaN on SiC HEMT Technology

High efficiency Ka-band power amplifier MMICs fabricated with a 0.15µm GaN on SiC HEMT process

High efficiency Ka-band Gallium Nitride power amplifier MMICs

Design and performance of 16–40GHz GaN distributed power amplifier MMICs utilizing an advanced 0.15µm GaN process

High Efficiency 5W/10W 32 - 38GHz Power Amplifier MMICs Utilizing Advanced 0.15µm GaN HEMT Technology