Paul D. Laforge

Diplexer Design Implementing Highly Miniaturized Multilayer Superconducting Hybrids and Filters

Multilayer superconducting quadrature hybrids for diplexer applications are reported for the first time in this paper. The hybrids employ highly miniature lumped element components embedded within four metal layers. The thin dielectric layers between the metal layers and the small feature size of the process allow for the miniaturization of lumped element capacitors and inductors. Hybrid-coupled diplexers using lumped element hybrids and filters have been developed, fabricated, and tested. A novel filter configuration that employs inter-resonator tap connections is also demonstrated for implementation in wideband filter applications. The whole integrated high Q (quality factor) diplexer is highly miniaturized being approximately lambda0 /60 in size at a frequency of 1.0 GHz. The diplexer structures are amenable to superconductor microelectronics technology and can be integrated monolithically with a superconducting receiver on a single chip.

Realization of a Highly Miniaturized Wideband Bandpass Filter at the UHF Band

A niobium-based low temperature superconducting 7-pole bandpass filter with a wide bandwidth at the UHF band is designed and tested. The filter has a relative bandwidth of 80% and is extremely miniaturized with a total dimension of less than 3 mm × 1 mm. The filter topology is that of the bandpass transformed lowpass prototype filter with alternating shunt and series resonators. The filter has a wide spurious free stopband up to 4 GHz. The measured results are in very good agreement with theoretical design predictions.

The Design of Miniaturized Superconducting Filters With the Reflected Group Delay Method

The reflected group delay method can be used to design higher-order superconducting filters. A correction factor is introduced to ensure that the reflected group delay response is symmetric about the center frequency. The method is demonstrated through the design of an eight-pole lumped-element filter using a circuit simulator. A miniaturized high-temperature superconducting eight-pole filter and a highly miniaturized lumped-element low-temperature superconducting eight-pole filter are designed using this method, and their measured results are reported.

Design of a chebyshev microstrip filter using the reflected group delay method and the aggressive space mapping technique

The aggressive space mapping technique is implemented as the optimization algorithm for the reflected group delay method in designing a 5-pole microstrip hairpin filter. The optimization routine using the reflected group delay method is represented mathematically and a design procedure is proposed for the integration of the space mapping technique and the reflected group delay method. The design steps are summarized and the filter is fabricated and tested. The optimization time is significantly reduced. The proposed method is proven to be very efficient and accurate for EM-based Chebyshev filter design.

Highly Miniaturized Multilayer Superconducting Filter

A multilayer superconducting filter is reported for the first time in this paper. The filter employs highly miniature lumped element components embedded within four metal layers. The 150 nm thick dielectric layer between metal layers of the process allows for the realization of capacitors with high values of capacitance. A 3-pole filter has been developed, fabricated, and tested. This filter has a measured center frequency of 1.28 GHz, and is only 2.0 mm by 0.6 mm in size. The filter structure is amenable to superconductor microelectronics technology and can be integrated monolithically with a superconducting receiver on a single chip

Design of a four pole quasi-elliptic microstrip filter using the reflected group delay method

The reflected group delay method of designing filters is demonstrated for the first time on a four pole quasi-elliptic filter requiring cross coupling. A design procedure is proposed that involves creating optimization curves from a lumped element filter and involves using these curves to design a microstrip filter. To validate the proposed design procedure, a microstrip filter with a center frequency of 1 GHz and 5% bandwidth is designed, fabricated and tested. The limits of the proposed design method are investigated by determining the maximum absolute bandwidth this filter can have using this method.

Low Temperature Superconducting Tunable Bandstop Resonator and Filter Using Superconducting RF MEMS Varactors

A novel niobium-based superconducting RF microelectromechanical system (MEMS) varactor is presented, and its mechanical performance is characterized at both room and cryogenic temperatures. The device is amenable to integration with superconducting microelectronics (SME) technology. The RF performance of the varactor at cryogenic (4 K) temperatures indicates capacitance variations from 40 fF to 0.46 pF. Hence, the varactor is used to design a monolithically integrated tunable resonator, whose measured results at cryogenic temperature show a sweep of frequency from 2.62 to 2.54 GHz and a discrete shift from 2.54 to 1.95 GHz, when the biasing voltage varies from 0 to 58 V. Using the same fabrication process, a fixed niobium-based three-pole bandstop filter is designed with a center frequency of 2 GHz and a size of 5 mm × 0.85 mm. Tunable versions of the three-pole filter using semiconductor varactors and monolithically integrated MEMS varactors are also designed and characterized at 4 K. The results of the tunable bandstop filters are analyzed both theoretically and experimentally.

Manifold-coupled switched filter bank implementing filters with embedded switches

A switched filter bank with 2N states for an N channel system is designed, fabricated, and tested. The design implements input and output manifold-coupled multiplexers with tunable filters. The bandwidth associated with a channel filter can be added or removed by actuating switches placed within the filter itself. This type of tuning allows for the switching of channel filters without affecting the other filters connected to the manifold. The concept is demonstrated using coplanar waveguide filters and diplexers.

Multiband superconducting filters

This paper discusses design techniques for multiband filters presenting two miniature configurations for a triple-band high temperature superconductor filter designed to meet the requirements of the Link 16 system. The first design employs a triplexer approach while the second design integrates a dual-band reject filter with a wideband bandpass filter. Simulation and measurement results are presented for both designs with a discussion on the suitability of multiband design techniques for implementation in high temperature superconductor technology. The measurement results demonstrate the feasibility of realizing more than 60 dB rejections between the three bands.

Automated EM-based design of bandpass filter by sequential parameter extraction and space mapping technique

A fully automated direct EM design approach for all-pole filters is proposed by integrating the reflected group delay design procedure with a novel sequential parameter extraction method. This approach contains a number of design stages in which 2-3 resonance frequencies of individual resonators or adjacent couplings are extracted from the simulated reflected group delay response of a one-port network separated from the entire filter. The space mapping technique is used to estimate geometric parameters from the extracted elements. Lagrange interpolation is exploited during the design process to estimate a few design parameters using mapping information from previous stages. A Matlab program is created to automate the design of a 6-pole interdigital microstrip band pass filter.