Filtering attenuators (filtenuators) combine the frequency selectivity of filters with the controlled loss of an attenuator in a single component. Often, the filtenuator is made of three resonators or less to minimize the complexity of the design and the resistive π-network distribution is straightforward. However, the resistive network distribution is less clear for high-order filtenuator designs. This paper presents an alternative method of loading a filtenuator that has more than three resonators and is compared to the traditional π-network method of loading a resonating circuit. A detailed analysis of the resistive network distribution is conducted to optimize the filter shape using a fifth-order Chebyshev bandpass filter topology. A 900 MHz fifth-order filtenuator with 6.5 dB of passband loss is designed using the optimized distribution method, and the measured results are compared to simulation.
This paper presents for the first time a temperature dependent ASM-HEMT model extracted from a gallium nitride (GaN) high electron mobility transistor (HEMT) validated with Ka-band on-wafer large-signal measurements. Modifications are made to the standard ASM-HEMT model to accurately model the DC, small-signal, and large-signal measurements collected as a function of ambient temperature. This work could shed light on the temperature dependence of GaN HEMTs and could enable the rapid design of high temperature integrated circuits.
We present a method for computing the input impedance of a rectangular waveguide-backed metasurface array excited by a common feed network. The metasurface array consists of rectangular waveguides loaded with subwavelength metamaterial radiators fed by the guided modes, excited with the feed. Thus, computation of the impedance at the input feed requires considering the electromagnetic interaction of the metasurfaces with its feed. Recently, semi-analytical models of metasurfaces using a coupled dipole framework have been proposed as efficient analysis tools. However, the models assume ideal waveguide ports for excitation and do not incorporate the response of feed networks, thus creating a gap in analyzing the overall response of the antenna. This paper addresses this gap by presenting a method using the coupled dipole framework and segmentation technique, which utilizes the impedance matrices for cascading multiport networks representing the metasurfaces and feed. The proposed method is verified via full-wave simulations.
The promises of 5G for high-speed internet and complete connectivity, anytime, anywhere and for anyone within a consumer electronics sector, rises concerns for possible signal interference and imposes the need for EM shielding solutions. We present the design and fabrication of a 3D printed hexagonal mesh (13 x 9 x 0.05) cm3 with unit cell maximal diameter 2.7 mm to reduce EM penetration at 2.4 GHz and 5 GHz. The mesh was characterized in an anechoic chamber adapting the MIL-STD-285 standard to vary the mesh-receiver antenna separation distance. The results show that the mesh exhibits a high SEA with a low SER for both frequencies and a total SE of 15 dB for 5 GHz, 23.66% higher than for 2.4 GHz. The closer the mesh to the receiver, the superior the absorption capacity. Attenuation could be explained by the destructive interference associated to the combination of composite filament in a concentric structure.
In modern conflicts, Electronic Warfare (EW) and signal sensing technology is becoming increasingly important to maneuver commanders in multi-domain operations. One of the challenges in integrating EW, electronic support, and direction finding into combined arms operations is the ability to simulate threat emitters, such as enemy tactical Very High Frequency (VHF) radios, in a manner that allows for integrating with live fire operations. Current simulators or commercial radios are cost prohibitive and not made for one-time use. Use of commercial radios often requires close proximity of operation. A low cost and consumable RF Threat emitter design is presented as a solution to train direction finding and electronic support in a sensor to shooter environment. An interface between a single board processor and Software Defined Radio (SDR) is developed. Battery, amplifier, and user interface is considered. Frequency Hopping, raw IQ, audio file playback, and other modulation schemes are achievable with SDR flexibility. The overall threat emitter system is tested in line of sight (LOS) environment. Received signal power is compared to multiple path loss and radio wave propagation models. The system performance and overall build cost are evaluated and shown to successfully emulate desired radio transmissions in the VHF band.
