Michael Hoft

Design and Analysis of Vertical Split Ring Resonator and Its Application to Unbalanced–Balanced Filter

We present a design method and analysis for a vertical split ring resonator (SRR). Furthermore, we propose an unbalanced-balanced filter using vertical SRRs. First, we explain vertical SRR with a stepped impedance resonator (SIR) using virtual ground. The resonance frequency is theoretically derived based on asymmetric coupled transmission lines. The resonance frequencies of vertical SRRs, calculated by our derived equation, are in good agreement with those of 3-D simulations and measurements. Next, this resonator is applied to an unbalanced-balanced filter based on low-temperature co-fired ceramic (LTCC). The attenuation poles of this filter are controlled by coupling between high-impedance lines similar to a two-pole filter with a SIR. The dimensions of the measured filter implemented with LTCC are 2.0 × 1.2 × 0.60 mm. The insertion loss is 2.80 dB in a 2.4-GHz band. Good agreement between measured and computed results is obtained.

Quasi-optical 150-GHz power combining oscillator

A quasi-optical power combiner for a five-element in-line oscillator array is experimentally investigated at 150 GHz. The combiner consists of a periodic dielectric phase grating (hologram) which transforms the near-field of a rectangular horn antenna array into a pseudo-plane wave. The horn array is excited by IMPATT oscillators operating uniformly in both amplitude and phase. A dual offset reflector set-up transforms the pseudo-plane wave to a Gaussian beam which matches the field pattern of a dual mode receiving antenna. Even though an inter-element spacing of 9.5 /spl lambda/ has been chosen, the passive structure gives a power combining efficiency of 74.1%. The power combining oscillator has been operated in both free-running and injection-locked mode. A CW output power of 78.0 mW and 83.5 mW was measured for the free-running and injection-locked oscillator, respectively, which is corresponding to a power combining efficiency of 66.5% and 71.2%, respectively.

Design of Symmetric Trisection Filters for Compact Low-Temperature Co-Fired Ceramic Realization

In this paper, the design of symmetric bandpass filters with cross-coupled trisections is discussed. The analysis and synthesis is done by well-known matrix manipulation of the lumped element equivalent circuit. The susceptance of the admittance matrix is split up into two separate matrices for capacitive and inductive contributions, which gives more insight into the manipulation of the matrix. Emphasis is put on design of a three-pole bandpass filter with two transmission zeros at the lower side of the passband. Novel solutions for the symmetric topology are derived, having either resonant main coupling or resonant cross-coupling. The potential of the novel topology is demonstrated by a compact realization of a wireless local area network filter at 2450 MHz in low-temperature co-fired ceramic technology. Good agreement between measured and computed results is obtained.

A two-dimensional quasi-optical power combining oscillator array with external injection locking

A quasi-optical power combiner for a 4/spl times/4 IMPATT oscillator array has been designed and experimentally investigated. The combiner consists of a bi-periodic dielectric phase grating which transforms the near field of a rectangular horn array into a pseudoplane wave. The horn array is excited by oscillators which operate uniformly in both amplitude and phase. A parabolic mirror with a superimposed surface relief couples the pseudoplane wave into a rectangular output horn antenna. In principle, the combiner has no restriction in inter-element spacing and is hence scalable up to submillimeter wavelengths without degradation of power combining efficiency. The quasi-optical design has been verified by scalar field measurements in several planes. The oscillator matrix is injection-locked by a master oscillator from the output port. A continuous wave output power of 1.3 W with an overall power combining efficiency of 70% has been measured at 65 GHz.

Broadband Analysis of Holographic Power Combining Circuits

Holography is a promising technique for power combining applications in the frequency range of short millimeter and submillimeter waves. In this paper, quasi-optical holographic power combining circuits are investigated. An equivalent network is utilized which rigorously models horn arrays and biperiodic dielectric structures in order to design computer-generated holograms. We apply the network model to a 5-element quasi-optical power combiner and demonstrate its capability. The hologram is designed for 150 GHz and has an efficiency of 92.5 % with a 90 % bandwidth of 5.3 %. With the aid of a broadband waveguide power divider and a vector field measurement system, the circuit is analyzed.

Electrically modulated magnetoelectric sensors

Magnetoelectric thin film composites have demonstrated their potential to detect sub-pT magnetic fields if mechanical resonances (typically few hundred Hz to a few kHz) are utilized. At low frequencies (1–100 Hz), magnetic field-induced frequency conversion has enabled wideband measurements with resonance-enhanced sensitivities by using the nonlinear characteristics of the magnetostriction curve. Nevertheless, the modulation with a magnetic field with a frequency close to the mechanical resonance results in a number of drawbacks, which are, e.g., size and energy consumption of the sensor as well as potential crosstalk in sensor arrays. In this work, we demonstrate the feasibility of an electric frequency conversion of a magnetoelectric sensor which would overcome the drawbacks of magnetic frequency conversion. This magnetoelectric sensor consists of three functional layers: an exchange biased magnetostrictive multilayer showing a high piezomagnetic coefficient without applying a magnetic bias field, a non...

Bandpass filter using TM-mode dielectric rod resonators with novel input coupling

In this paper a bandpass filter is presented, which is based on TM-mode operation in dielectric rods. The bandpass filter consists of 7 resonators, has a center frequency of 1950 MHz, a bandwidth of 60MHz and two cross-couplings by cascaded quadruplet configurations for improved blocking performance. The layout will be discussed. A novel input coupling assembly is introduced. Parametric study for the coupling performance is presented. Furthermore, measurement results are shown.

Inverse bilayer magnetoelectric thin film sensor

Prior investigations on magnetoelectric (ME) thin film sensors using amorphous FeCoSiB as a magnetostrictive layer and AlN as a piezoelectric layer revealed a limit of detection (LOD) in the range of a few pT/Hz1/2 in the mechanical resonance. These sensors are comprised of a Si/SiO2/Pt/AlN/FeCoSiB layer stack, as dictated by the temperatures required for the deposition of the layers. A low temperature deposition route of very high quality AlN allows the reversal of the deposition sequence, thus allowing the amorphous FeCoSiB to be deposited on the very smooth Si substrate. As a consequence, the LOD could be enhanced by almost an order of magnitude reaching 400 fT/Hz1/2 at the mechanical resonance of the sensor. Giant ME coefficients (αME) as high as 5 kV/cm Oe were measured. Transmission electron microscopy investigations revealed highly c-axis oriented growth of the AlN starting from the Pt-AlN interface with local epitaxy.

Y-Shape Dielectric Dual-Mode Resonator

In this paper, a new concept for a dual-mode dielectric resonator is presented, which is based on TM-mode operation in dielectric rods. By arranging the dielectric rods in Y-shape configuration, new fundamental eigenmode resonances are found to be present. The eigenmodes are coupled parallel to the input and output of the filter to result in a doublet coupling scheme. The filter was laid out by the global eigenmode approach. For filter configurations showing E-plane/H-plane mirror symmetry, the required parameters are determined and optimized by an eigenmode solver. A nonplanar Y-shape monoblock ceramic was constructed to achieve bandpass operation at 2 GHz. Measurement results of the constructed dual-mode filters are presented for the first time. The setup is suitable to demonstrate the zero-shifting property of the doublet by slightly adjusting the position of the ceramic inside the cavity. An unloaded quality factor of 4000 was extracted from the measurements. Good agreement between measured and computed results is obtained.

A multi-element 150/300 GHz spatial power dividing/combining frequency doubler

A five-element frequency doubler at 300 GHz in a quasi-optical spatial power dividing/combining circuitry has been investigated. The individual frequency doublers are realized with GaAs-Schottky-diodes in waveguide technique with 4% efficiency. Holography is applied to achieve efficient power transfer to/from the active devices. Preliminary measurements are in good agreement with the expected system performance.