Before the emergence of ultra-wideband (UWB) radios, widely used wireless communications were based on sinusoidal carriers, and impulse technologies were employed only in specific applications (e.g. radar). In 2002, the Federal Communication Commission (FCC) allowed unlicensed operation between 3.1–10.6 GHz for UWB communication, using a wideband signal format with a low EIRP level (−41.3dBm/MHz). UWB communication systems then emerged as an alternative to narrowband systems and significant effort in this area has been invested at the regulatory, commercial, and research levels.

IEEE Transactions on Microwave Theory and Techniques and Antennas and Propagation Announce a Joint Special Issue on Ultra-Wideband (UWB) Technology

This paper reports a W-band solid-state power amplifier with an output power of 5.2W at 95 GHz and greater than 3 watts over the 94 to 98.5 GHz band. These SOA results were achieved by combining 12 GaN MMICs in a low-loss radial-line combiner network. The 12-way combiner demonstrates an overall combining efficiency of 87.5%, and excluding combiner conductor losses (0.3 dB), exhibits a combining efficiency of 93.7% at 95GHz. The size of the 12-way amplifier/combiner is only 2.39″ dia. × 1.5″ length. This work represents the first application of the radial-line combiner configuration to applications at W-band frequencies, and establishes new levels of performance for solid-state power amplifiers operating at these frequencies.

W-band, 5W solid-state power amplifier/combiner

A $Ka$ -band isolated radial power divider via circular waveguide ${\rm TE}_{01}$ -mode converter is presented in this paper. By redesigning and using the circular waveguide ${\rm TE}_{01}$ -mode transducer to feed the 20-way radial power divider–combiner, the overall structure is miniaturized. Moreover, the resistive septum is inserted into the waveguide to improve the return loss and the isolation of the output ports. A measured return loss at the output port has improved by around 15 dB, while the worst case isolation is more than 12 dB over 28–36 GHz after using the resistive septum.

An Isolated Radial Power Divider via Circular Waveguide ${\rm TE}_{01}$ -Mode Transducer

A Ka-band traveling-wave power divider/combiner, which is based on double ridge-waveguide couplers, is presented. The in-phase output, which is a challenge of the waveguide-based traveling-wave power divider, is achieved by optimizing the equivalent circuit of the proposed structure. The novel ridge-waveguide coupler has advantages of low loss, high power capability, and easy assembly. Finally, the proposed power divider/combiner is simulated, fabricated, and measured. A 15-dB measured return-loss bandwidth at the center frequency of 35 GHz is over 28%, a maximum transmission coefficients amplitude imbalance of ±1 dB is achieved, and the phase deviation is less than ± 12° from 32 to 39 GHz.

An In-Phase Output $K\!a$ -Band Traveling-Wave Power Divider/Combiner Using Double Ridge-Waveguide Couplers

Several different microwave circuits, including beamforming networks and balanced amplifiers, make use of 3-dB power dividers and combiners. A well-known architecture able to work over large bandwidths, a critical request for many applications, is based on E-plane three-port waveguide structures, where a lossy element is added to overcome the inherently poor isolation given by lossless three-port junctions. While a standard implementation based on normal rectangular waveguides often results in large and heavy structures, an implementation based on substrate-integrated-waveguide (SIW) technology offers advantages in terms of compactness, weight reduction, cost minimization, and integration possibilities with active stages. This paper presents the design, fabrication, and characterization of two SIW E-plane 3-dB power divider/combiners where the lossy element is realized using a resistive layer. The prototypes cover the entire $X$ -band from 8 to 12 GHz, and the resistive layers are realized according to two different manufacturing techniques to investigate the potentials of both approaches. The optimization of the resistive layer geometry and resistivity, a critical aspect for low-profile SIW circuits, is discussed in detail. In particular, an analytical formula is derived, which allows to determine the optimum values for the resistive layers’ principal parameters, namely the length and resistivity, without the use of full-wave numerical solvers.

Substrate-Integrated-Waveguide E-Plane 3-dB Power-Divider/Combiner Based on Resistive Layers

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.

S.L. Stride

Papers

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