Electromagnetic Metamaterials: Transmission Line Theory and Microwave Applications. By Christophe Caloz and Tatsuo Itoh.

In general, Micropower Impulse Radar (MIR) depends on Ultra-Wideband (UWB) transmission systems. UWB technology can supply innovative new systems and products that have an obvious value for radar and communications uses. Important applications include bridge-deck inspection systems, ground penetrating radar, mine detection, and precise distance resolution for such things as liquid level measurement. Most of these UWB inspection and measurement methods have some unique qualities, which need to be pursued. Therefore, in considering changes to Part 15 the FCC needs to take into account the unique features of UWB technology. MIR is applicable to two general types of UWB systems: radar systems and communications systems. Currently LLNL and its licensees are focusing on radar or radar type systems. LLNL is evaluating MIR for specialized communication systems. MIR is a relatively low power technology. Therefore, MIR systems seem to have a low potential for causing harmful interference to other users of the spectrum since the transmitted signal is spread over a wide bandwidth, which results in a relatively low spectral power density.

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Response to FCC 98-208 notice of inquiry in the matter of revision of part 15 of the commission's rules regarding ultra-wideband transmission systems

Foundations For Microwave Engineering

We describe the saturation properties and power scaling of large-aperture planar photoconducting antennas. These antennas have been used to emit and detect electromagnetic pulses with terahertz bandwidth. At high optical fluences, the amplitude of the radiated electric field saturates, at a value comparable to the bias field in agreement with a simple model of the radiation. We also discuss the saturation properties of the large-aperture photoconducting antennas with different semiconductor materials.

Saturation properties of large-aperture photoconducting antennas

A frequency-selective power combiner/divider in single-layer substrate integrated waveguide (SIW) technology is introduced. The basic building block consists of a planar four cavity structure with three of them operated in SIW TE101 modes and one in SIW TE201 mode. Each cavity is coupled to one port of the unit. In addition the overall configuration considers couplings of each resonator to the two adjacent ones. Due to the coupling transformation properties of the TE201 mode cavity, second order 3 dB transfer functions are obtained from each port to two adjacent ones while the fourth port is almost isolated. The novel combiner/divider is designed for 11 GHz and prototyped on RT/Duroid 5870 substrate. Measurements verify the design process and operation of the device.

A Novel Frequency-Selective Power Combiner/Divider in Single-Layer Substrate Integrated Waveguide Technology

The terahertz (THz) antennas, which have features of small size, wide frequency bandwidth and high data rate, are important devices for transmitting and receiving THz electromagnetic waves in the emerging THz systems. However, most of THz antennas suffer from relatively high loss and low fabrication precision due to their small sizes in high frequency bands of THz waves. Therefore, this paper presents a detailed overview of the most recent research on the performance improvement of THz antennas. Firstly, the development of THz antennas is briefly reviewed and the basic design ideas of THz antennas are introduced. Then, THz antennas are categorized as metallic antennas, dielectric antennas and new material antennas. After that, the latest research progress in THz photoconductive antennas, THz horn antennas, THz lens antennas, THz microstrip antennas and THz on-chip antennas are discussed. In particular, the practical difficulties for the development of THz antennas are discussed with promising approaches. In addition, this paper also presents a short review of the process technology of THz antennas. Finally, the vital challenges and the future research directions for THz antennas are presented.

An overview of terahertz antennas

A wideband fifth-order bandpass filter (BPF) is proposed and designed using the U-slotted substrate integrated waveguide (SIW) cavities. The U-shape slots, etched on the SIW cavity, are used to form up a new multiple-mode resonator (MMR) in order to achieve a wide passband of operation while keeping the overall size of the filter circuit to be much compact. The proposed fifth-order SIW filter is 2.5 times in size reduction compared with the traditional fifth-order SIW filters using the single-mode SIW cavities. In order to prove the validity, one wideband SIW BPF on a single layer printed circuit board (PCB) is designed and experimentally examined. The measured results show that the filter achieves an insertion loss of 1.1 dB at 8.5 GHz, return loss of higher than 11 dB and 3 dB fractional bandwidth of 42%. The measured results are in good agreement with the simulated results.

Wideband Bandpass Filter Using U-Slotted Substrate Integrated Waveguide (SIW) Cavities

In this brief, a dual-mode dual-band filter based on half-mode substrate integrated waveguide (HMSIW) is presented. The proposed filter has the capability to tune the two pass-bands independently. The proposed filter consists of two HMSIW resonators coupled through a pair of ${E}$ -shaped coupling slots. Two resonating modes ( TE 101 and TE 102) are excited in each resonator. A varactor diode is used in the proposed filter for tuning purpose. The varactor diode is placed in the structure in such a way that both bands can be tuned independently. The lower passband can be tuned from 3.26 to 3.47 GHz with insertion loss of 0.2–2.9 dB. The higher passband can be tuned from 5.47 to 6.13 GHz with low insertion loss of 0.1–2.1 dB. The presented results show the flexibility of the filter to achieve desired responses and its suitability for integration with any tunable planar structure. A good agreement between the simulated and measured results is observed.

Dual-Band Half Mode Substrate Integrated Waveguide Filter With Independently Tunable Bands

In this letter, a printed planar filtering antenna composed of the stepped-impedance dipole (SID), stepped-impedance resonator (SIR), and low-pass filter (LPF) is presented. The SIR is used as a parasitic element in proximity to the SID radiator to improve its upper band-edge selectivity and to widen its operation bandwidth. Our extensive study is at first conducted to exhibit that the upper harmonic band of radiation can be tremendously pushed upward by appropriately replacing the main dipole radiator and the parasitic resonant element with the SID and SIR. Next, a stepped-impedance LPF is employed to further effectively suppress the high-order harmonic band of radiation as quantitatively demonstrated. The measured reflection coefficient has achieved a wide fractional bandwidth up to 27.5%, covering a frequency range of 2.5–3.3 GHz, with $\vert{ S}_{11}\vert . In particular, its first harmonic band for radiation has been significantly extended from 7.2 GHz beyond 14.0 GHz as confirmed in simulation and experiment.

A Compact Printed Filtering Antenna With Good Suppression of Upper Harmonic Band

This paper proposes a novel diplexer based on triple-mode dielectric-loaded cylindrical cavities. Such two metal cavities are designed to achieve two different frequency bands, while three resonant modes of a single cavity are classified as a TM mode and a pair of hybrid (HE) degeneration modes. An off-centered dielectric resonator instead of a traditional corner cuts perturbation or screws perturbation properly perturbs the two degenerate modes in the same cavity. Extensive study is then conducted to design this proposed diplexer. Finally, a diplexer prototype is fabricated using a brass cavity and it is tested for experimental verification of the predicted results. Good agreement between measurement and simulation is achieved.

Sai-Wai Wong

Papers

An overview of terahertz antennas

Wideband Bandpass Filter Using U-Slotted Substrate Integrated Waveguide (SIW) Cavities

Dual-Band Half Mode Substrate Integrated Waveguide Filter With Independently Tunable Bands

A Compact Printed Filtering Antenna With Good Suppression of Upper Harmonic Band

Triple-Mode Dielectric Resonator Diplexer for Base-Station Applications