A novel three-line-microstrip compact impedance tuner is presented. It is based on a multimodal structure wherein six variable capacitances, implemented with two parallel-connected varactors each, create multiple interactions among the three-line-microstrip modes in a reduced circuit area. Experimental results show better-than-70% coverage of the Smith chart in an 85% frequency bandwidth from 1.4 to 3.2 GHz.

In this paper, new RF-MEMS switch configurations are proposed to enable control of the propagating (even and odd) modes in multimodal CPW transmission structures. Specifically, a switchable air bridge (a switchable short-circuit for the CPW odd mode) and switchable asymmetric shunt impedances (for transferring energy between modes) are studied and implemented using bridge-type and cantilever-type ohmic-contact switches, respectively. The switchable air bridge is based in a novel double ohmic-contact bridge-type structure. Optimized-shape suspension configurations, namely folded-beam or diagonal-beam for bridge-type switches, and straight-shaped or semicircular-shaped for cantilever-type switches, are used to obtain robust structures against fabrication-stress gradients. The switches are modelled using a coupled-field 3D finite-element mechanical analysis showing a low to moderate pull-in voltage. The fabricated switches are experimentally characterized using S-parameter and DC measurements. The measured pull-in voltages agree well with the simulated values. From S-parameter measurements, an electrical model with a very good agreement for both switch states (ON and OFF) has been obtained. The model is used in the design of reconfigurable CPW multimodal microwave filters.

In coplanar waveguide (CPW) circuits, printed balanced antennas must be excited through baluns. These baluns often feature coplanar-to-slot-line transitions that must be tuned and matched by electromagnetic optimisation, and may interfere with the antenna backward radiation. A new CPW balun for printed balanced antennas is presented and modelled. As its multimodal circuit model makes clear, it integrates an impedance-matching network within its structure that can be analytically designed. The balun has been experimentally tested, exhibiting good agreement with its circuit model and a weak electromagnetic interaction with the antenna radiation.

In this letter, a new compact two‐pole band‐pass filter (BPF) based on an asymmetric short‐circuited spurline resonator is presented. The filter is modeled by means of a new multimodal circuit model for a microstrip to three‐line‐microstrip cross, which allows a rigorous study of a very generic new family of filters. A BPF centered at 1.9 GHz has been designed, measured, and simulated using this multimodal model. A good agreement between measurements and simulations has been obtained. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1328–1331, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25161

A typical power-line filter is composed, essentially, by common-mode chokes, X-class and Y-class capacitors. A good characterization of these components is needed to develop a technique to design the optimal power-line filter for an electric or electronic device by finding their best values. In this paper, a new methodology to characterize the behavior of power-line filter capacitors is presented. This methodology is based on a model where common-mode and differential-mode interference are separated into different ports in order to facilitate the study of the propagation phenomena. The methodology is used to explain modal conversion inside impedance networks with X-class and Y-class capacitors, to predict the common-mode and differential-mode emissions when these capacitors are connected to electric or electronic devices, and to improve the classical methodology of power-line filter implementation finding the optimal capacitances of the impedance networks. This new methodology has been successfully tested by using real measurements from capacitors and electric devices.

A passive internal handset antenna for FM reception is presented using electromagnetic simulations as well as laboratory experiments. Received signal for the antennas have been demodulated and the quality of the audio signal evaluated Results have been compared with a long antenna (lambda/4) confirming that the proposed solution is et good candidate to migrate to a full wireless FM system that may he integrated into a handset phone. (C) 2008 Wiley Periodicals, Inc.

Guard traces are used in PCB implementations to avoid interferences between signal strips. These guard traces can affect the integrity of high harmonic content signals such as clock or wideband RF signals. In this paper, the effect of guard traces is analyzed from a multimodal point of view. A multimodal analysis allows a simple interpretation of the phenomena involved in the loss of integrity of signals propagating through strips close to the guard traces. Two guard trace configurations are analyzed, circuitally simulated and measured in order to test the adequacy of the multimodal approach to describe the behavior of signal strips close to guard traces, showing good agreement between theory and experiment.

Clock signal paths are often routed near other signal strips over a ground plane. These situations generate configurations of strips involving coupled microstrip sections interacting with non coupled microstrip sections, and generating transitions between coupled and uncoupled microstrip sections that heavily modify the propagations of both clock and information signals. These transitions usually cause a degradation of the signal integrity. The transitions generated by typical configurations of strips are: a microstrip-coupled microstrip tee and a coupled microstrip-microstrip cross. In this paper, rigorous circuit models for these transitions are presented and applied to the prediction of the behavior of a clock distribution near a signal path. The models presented are multimodal: they split the contribution of even (common) and odd (differential) signals (modes) into different ports, and allow the analysis of circuits that present different responses to either mode. The good agreement between circuit simulation and measurements validates the models

Signal paths are often routed with their ground ones. These ground paths are usually connected through a via-hole to the ground plane. This grounded strip creates a transition: a via-hole common-to-differential mode transition. Although these transitions behave in an ideal way at low frequencies, they can show significant effects at higher frequencies, due to their multimode behavior. These effects can cause a degradation of the signal integrity. A rigorous circuit model for via-hole common-to-differential mode transitions is presented and tested. The model splits the contribution of common and differential signals (modes) into different ports, and allows the analysis of circuits that present different responses to either mode. The model is tested in several PCB configurations. The good agreement between circuit simulation and measurements validates the model and demonstrates its utility as a design tool.

A new technique to predict the small signal behavior of EMI power-line filters is presented. This technique is based on S-parameter measurements performed at all the terminals of the power-line filter. These measured S-parameters are converted to a set of modal S-parameters using the presented analytical matrix expressions. The modal S-parameter matrix completely models the small signal behavior of the power-line filter in terms of line and load common and differential modes. From this matrix, information such as common and differential mode insertion loss, modal behavior of the filter at different line and load impedances, and energy transfer between any combination of modes can be obtained.

Common-to-differential mode PCB transitions are present in most PCB implementations. Although they behave in an ideal way at low frequencies, they can show significant effects at higher frequencies, due to their multimode behavior. These effects can cause a degradation of the signal integrity. In this paper, a rigorous circuit model for common-to-differential mode PCB transitions is presented and tested. The model splits the contribution of common and differential signals (modes) ports, and allows analysis of circuits that present different responses to either mode. The model is tested in several PCB configurations. The good agreement between circuit simulation and measurements validates the model and demonstrates its utility as a design tool.

A novel method for predicting the equivalent OATS radiated emissions of a DUT from anechoic chamber measurements is presented. This method allows the use of a single environment (the anechoic chamber) for both radiated emissions and immunity tests. It is based on the substitution of the DUT by an equivalent set of elemental dipoles (using a hybrid genetic algorithm-gradient method) which radiates the same anechoic field. Since the field generated by an elemental dipole is known, OATS equivalent radiated emissions can be calculated using image theory. Simulations show the viability and usefulness of the new method.