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.

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.

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.

To achieve a dispersionless channel, the receiver must counteract the dispersion caused by the transmitter, assuming that the propagating medium is dispersionless. If identical antennas are used for transmission and reception, constraints are placed on the antenna of interest, since the temporal transmit and receive responses of an antenna are linked through reciprocity and related by a time derivative. By invoking the concept of a half-derivative, it was proposed in Tyo's 2008 paper, that a half-differentiator transmitter in the time domain (TD) will operate as a half-integrator receiver over some range of frequencies. In the frequency domain (FD) this corresponds to a transfer function that behaves in a similar fashion as the 2D Green's function due to a line source. The required antenna should transmit and receive cylindrical waves efficiently. When used in UWB applications, a receiving antenna with this property will counteract its dispersion effect as a transmitter, providing a flat overall channel gain. In this work, a numerical model for a rotationally symmetric structure with a dielectric lens is used as a transmitter to verify the above proposition. We start by a brief explanation of the principle on which the antenna works as cylindrical source. A study of FD and TD parameters of the model are provided. The limitations due to the dielectric lens are also addressed, and other geometries of similar characteristics are modeled. In these examples, we demonstrate how the information contained in the radiated fields can help in predicting the flatness of channel gain.

We recently proposed that a monocone antenna on a ground plane with an embedded dielectric lens could be designed to have a frequency domain (FD) transfer function that is proportional to Hankel function of the second kind H 0 (2) (betarho). Such an antenna would radiate a half-derivative in the time domain (TD). Since an antennapsilas transient transmit response is the derivative of its receive response, such an antenna would be self-compensating if used as both the transmitter and receiver in a communications link. In this work, the shape of the lens that produces this result is determined, and the effect of the lens on the radiated field is discussed. A full EM numerical model based on the FEM is developed using the PDE toolbox in Matlab. The input impedance and the gain of the modeled antenna are calculated over a wide frequency range. In section IV, fast Fourier transform is utilized to observe the radiated field in the TD. We see that the general properties of the self-compensating antenna are in fact observed, namely a channel response that is flat over a broad frequency range. However, the flatness of the response is hurt in the current design due to resonances associated with the finite size of the monocone and the dielectric discontinuity of the lens. Future work will seek to reduce these effects.

In this paper we present antenna design concepts that produce a flat UWB channel when identical antennas are used on the transmit and receive ends of the system. We have shown previously that an antenna that has a half-derivative impulse response on transmit will have a half-integral impulse response on receive. The receive antenna therefore compensates for the dispersion introduced on transmit. Here we consider the performance of partially focused monocone antennas that approximate ideal pulsed line current sources.

Recently we proposed a general framework for designing an antenna that, when used on both the transmit and receive ends of an UWB link, provide dispersion-free propagation. In order to achieve this performance, the antenna should radiate a half-derivitive of the applied voltage, which corresponds to the time-domain Green's function of an infinite line source. In this paper we consider topologies based on conical symmetry that approximate the infinite line source, analyze the fields in the vicinity of the antenna to understand performance, and assess their performance and utility as antennas in UWB systems.