We model a linear EZ antenna array for HPEM applications. Equivalent circuit models of the single element EZ antenna and two element array antenna are presented, relating antenna performance and field coupling to physical parameters. This fully parameterized circuit model can be used to load the transmission line or waveguide feed and design a particular aperture field configuration, which can then be synthesized through the physical model.

For high-power electromagnetic (HPEM) applications at high-repetition rate, conventional microwave inverters based on pulse transformers are not practical. At high-repetition rates, the magnetic materials used in the inductive coupling saturate. In this paper, we present an alternate concept for an inverter based on the technology used for ultrawideband baluns which provides isolation through capacitive coupling. Design of the device is discussed through numerical modeling, and two implementations are built and demonstrated: a circuit element version and a transmission line version. The devices are demonstrated at charge voltages of 6 kV and repetition rates up to 100 Hz, with excellent performance between 20 MHz and 2.5 GHz. The circuit element device has a rise time of 445 ps with an insertion loss of less than 3 dB, while the transmission line device has a rise time of 240 ps with an insertion loss of less than 2 dB for most frequencies. The inverter is demonstrated as part of the feed network for a hyperband HPEM antenna with a differential input.

A mesoband, high-power microwave source system is presented that couples a compact standing-wave oscillator operating near 500 MHz to a compact helical antenna. The antenna has a turn length that is on the order of $3\lambda /4$ with a pitch of 46 $^\circ$, and the ground plane that is $\lambda /6$ in diameter. The system radiates in the axial mode in the backward direction with a front-to-back ratio of $-$ 4.6 dB. Numerical analysis of the antenna is presented to understand the design constraints, and a prototype system is built and tested to verify the numerical results. The source and antenna combination are verified at a charge voltage of 23 kV, and radiated fields in excess of 10 kV/m are measured at a range of 1 m with circular polarization.

The efficacy of the three-dimensional, rectangular magnetic EZ antenna for use with mesoband high-power microwave (HPM) sources has been demonstrated previously. It overcomes the typical bulky and massive impedance-matching components found currently in most HPM systems, making it an attractive option when space is very limited. However, its extremely compact nature presents practical challenges when dealing with extremely high-power sources due to the associated local field enhancements near the feed and the near-field resonant parasitic element. This letter presents a fully integrated, high-voltage source and radiating system that has several improvements in the antenna, source, and power system that have not before been demonstrated. The full system includes a ferroelectric generator, standing wave oscillator source, and electrically small antenna ( ka = 0.37) operating at 510 MHz that can be packaged inside a 15-cm-diameter tube. This small diameter results in a quarter-wavelength-diameter ground plane, and the effects of this small ground plane on the radiation characteristics are explored. The development of a pressurized radome allows for operation at 73.6 kV, significantly higher than previous studies.

One major challenge associated with high power microwave systems is being able to produce high voltages and fields in a compact space. In this paper, we discuss two options for extremely compact mesoband HPM systems operating in the UHF (near 500 MHz). These systems fit into a cylindrical volume of diameter 10-cm, and are designed to be able to include the prime power, pulsed power, and antenna radiation. The pulsed power is based on a well-established quarter- wave oscillator, and here we consider the extremely electrically small EZ antenna as well as a compact, non-conventional helical antenna.

High power microwave (HPM) sources are typically bulky and massive in order to be able to radiate the extremely high source powers with a good impedance match and low losses. For this reason, it is sometimes difficult to incorporate an HPM antenna onto a desired platform when the available space is small. In previous work, we have adapted an electrically small EZ antenna to operate with a mesoband, quarter-wave oscillator source. The EZ antenna operates over a ground plane, but is conformal and low profile in that the electrical size is on the order of λ/12, making it attractive for applications where there is sufficient internal space to place a full source, but only limited space outside the platform for the radiating subsystem. Here we extend the capabilities of the oscillator/EZ antenna combination by introducing a dual band design for the antenna and altering the oscillator to produce multiple resonant frequencies. Designs are shown here that operate in the UHF (500-800 MHz) and L-band (1.5-1.8 GHz), but the operation frequencies are essentially arbitrary. This paper shows modeling results that predict high antenna efficiency with electrical sizes of at Ka <; f = 500 MHz.

High-power microwave (HPM) moderate-band (MB) sources combine simple design concepts seen in ultrawideband (UWB) sources, but with longer pulses to produces higher energy spectral densities. These factors allow the designs to be more compact and less complicated than many narrowband HPM sources. In this letter, we will demonstrate from both simulation and experimental results the operation of a electrically small, tunable, self-resonant, mesoband source utilizing a conical folded dipole antenna as the energy storage and radiating element. The system is based on a previous design for an HPM folded helix antenna that has a resonant frequency of 46 MHz and is charged to 70 kV. The design presented here utilizes a tunable capacitance that allows the resonant frequency to be tuned between 52 and 87 MHz with ka = 0.58 at the lowest resonant frequency.

Previously, we demonstrated the integration of an electrically small EZ antenna with a mesoband high power microwave (HPM) quarter-wave oscillator source. This design was confirmed with both computer modeling and experimental results for an EZ antenna with ka = 0.47. We also have reported results from computer simulations of a dual-band HPM EZ antenna system with resonances near 500 MHz and 1.5 GHz. In this paper we discuss the design of an EZ antenna array fed via the same mesoband source through a radial waveguide designed for handling high power levels.

We have previously considered the use of a modified, conical, folded helix antennas as the energy storage and radiation mechanism for an electrically-small, high power microwave (HPM) system. Our previous results allowed us to integrate the antenna with a HPM switch to achieve a resonance of below 40 MHz for an overall antenna dimension of 101.3 cm (ka = 0.42). In this paper, we consider other folded helix geometries in order to analyze the best one for compact, low-frequency HPM applications. The antennas were modeled using CST Microwave Studio, and each antenna type was evaluated for its resonant frequency, local field enhancement, and radiation properties.

Previously we reported on the integration of an electrically small EZ antenna with a mesoband HPM source based on a coaxial, quarter-wave oscillator. In our previous work, we demonstrated through modeling and experiment the use of an antenna with ka = 0.47 for radiation of HPM signals. In the present paper, we present a design that allows the oscillator to function as a dual-frequency source by including multiple trigger points. We further adapt the EZ-antenna to be dually resonant with no increase in size through the use of orthogonal polarization coupling.

Metamaterial (MTM)-inspired antennas leverage techniques that have been developed over the past decade for designing artificial materials whose electromagnetic properties can be tailored to specific applications. One of the key features of the MTM-inspired antennas is their ability to motivate electrically small antenna designs through planar and volumetric loadings of space with resonant parasitic capacitive and inductive structures. In a previous work, we developed the magnetic EZ antenna as a resonant antenna that operates below ka = 0.5. In this paper, we adapt the magnetic EZ antenna concept for use with high-power mesoband quarter-wave oscillator microwave sources that can operate with hundreds of megawatts of peak power and charge voltages in excess of 100 kV in the ultrahigh frequency (500-650 MHz) and demonstrate their performance with charge voltages up to 10 kV. The principal challenges that were overcome in this effort include field management to prevent undesired breakdown and capacitive isolation to decouple the EZ antenna from the source during the charge phase. Antenna design, modeling, and experimental verification are presented here, demonstrating an operating EZ antenna/source system at 510 MHz with antenna ka = 0.436 . The results demonstrate that the EZ antenna is a viable antenna to consider when traditional high-power microwave antennas are too large to be integrated into a given platform.

We report here on the modeling and experimental verification of a metamaterials-inspired, electrically small antenna developed for use in mesoband HPM applications. The antenna is an adaption of the previously reported magnetic EZ Antenna. The primary adaptations needed for use in this HPM application is the alteration of the feed impedance, control of field enhancement, and - most importantly - the electrical decoupling of the antenna from the HPM source. Preliminary results from the driven antenna operating at 510 MHz are presented.

Quarter-wave switched oscillators (SWOs), sometimes referred to as MATRIX oscillators, are an important technology for the generation of high-power, moderate bandwidth (mesoband) waveforms. The use of SWOs in high power microwave sources has been discussed for the past 10 years but a detailed discussion of the design of this type of oscillators for particular waveforms has been lacking. In this work a design methodology for a realization of SWOs is developed. A key element in the design of SWOs is the self-breakdown switch, which is created by a large electric field. In order for the switch to close as expected from the design, it is essential to manage the electrostatic field distribution inside the oscillator during the charging time. This enforces geometric constraints on the shape of the conductors inside the oscillator. At the same time, the electrodynamic operation of the system is dependent on the geometry of the structure. In order to generate a geometry that satisfies both the electrostatic and electrodynamic constraints, a new approach is developed to generate this geometry using iterative solutions to the 2-D static Laplace equation, subject to a particular set of boundary conditions. These boundary conditions are manipulated to generate equipotential lines with specific dimensions that satisfy the electrodynamic constraints. Meanwhile, these equipotential lines naturally support an electrostatic field distribution that meets the requirements for the field enhancement.To study the electrodynamic aspects of SWOs, three different (but inter-related) numerical models are built. Depending on the assumptions made in each model, different information about the electrodynamic properties of the designed SWO are obtained. In addition, the agreement and consistency between the different models, validate and give confidence in the calculated results.

In this paper, the problem of designing switched oscillators at four different frequencies (200, 300, 400, and 500 MHz) has been addressed. These oscillators are quarter-wavelength long coaxial transmission lines with a nitrogen spark gap switch at one end. Two of these switched oscillators at 200 and 500 MHz with a charge voltage of 30 kV have also been fabricated. These two oscillators are modeled using PSpice and their output into a 100 Ω load is estimated and tested by fabricating a 100 Ω transmission line. Use is made of a modified commercial helical antenna with a bandwidth of 400-600 MHz and a switched oscillator has been integrated into this helical antenna. Measurements have been made of the S 11 , the voltage into the antenna, and also the transient fields at two distances. Indeed, starting from electrical power from a 12 V battery, electrical field strengths in excess of 10 kV/m with damped sinusoidal waveforms at 500 MHz (for example) have been demonstrated.

We present system considerations for the design of a tunable mesoband source based on a parallel-plate Blumlein architecture. Here, we discuss the switching characteristics, electrode shaping, and tunability of a system designed to operate from 100 MHz to 1.5 GHz with charge voltages up to 100 kV. The first prototypes that have been tested and are reported on here have been tested at charge voltages up to 50 kV for operating frequencies of 500 MHz and 1.4 GHz. The requirements of the high-voltage system necessitated a high-pressure switch that is fully integrated into the Blumlein, requiring detailed mechanical design. A full system design is presented, which will be constructed and tested in future work.

Quarter-wave switched oscillators (SWOs) are an important technology for the generation of high-power mesoband waveforms. The operation of these SWOs has been discussed for the past several years, but a detailed discussion of the design of these sources for particular waveforms has been lacking. In this paper, we relate several important parameters such as gap spacing, oscillator shape, and antenna to the properties of the radiated waveform.

Transmission line oscillators are widely used for high power mesoband sources. These devices have high voltage handling capability on the order of 100s of kV, with moderate bandwidths on the order of 5 – 25% at frequencies of about 200 MHz. Transmission line oscillators are particularly easy to design to a specific resonant frequency, and in many cases can even be dynamically tuned. Two common topologies are parallel-plate Blumlein geometries and quarter-wave coaxial oscillators. In this paper we explore the fundamental limits among the peak charge voltage (V0), resonant frequency (fr), and resonator quality factor (Q). We find that there are empirical limits of the product of V0frQn, where n is an exponent ∼1 that depends on the specific resonator geometry.