Search

This paper shows a study of a new ferrite low-temperature cofired ceramic (LTCC) circulator with integrated winding. The external magnets used in traditional circulators must be strong to overcome the ferrite’s demagnetization factor. The novel circulator presented herein uses an embedded winding within the ferrite to magnetize the material from the inside, thereby significantly reducing the demagnetization effects. Because of the controllability of the bias field, the resulting device is also multifunctional: when the windings are energized by a current, the device operates as a dynamic circulator in which the circulation direction can be changed by switching the direction of the current. If an external magnet is placed on the circulator, its operating frequency can be changed by adjusting the bias current. Unlike other LTCC circulators with external magnets, the proposed device can even operate as a power splitter by removing the bias current. A circulator prototype has been characterized in three states: unbiased, biased by windings, and biased by windings and external magnets. When no current is applied, the transmission of each port is about −5 dB with a return loss better than 20 dB at 14.8 GHz. When a current of 300 mA is injected into the windings, the measured insertion loss and isolation of the circulator are approximately 3 and 8 dB, respectively, whereas the return loss is better than 20 dB at 14.2 GHz. When external magnets are added in addition to a current of 200 mA, the insertion loss and isolation improve to 1.6 and 23 dB, respectively, at 14.2 GHz. The variation of the circulator’s working frequency is 0.6 GHz. This is achieved first by the change of internal magnetization \boldsymbol M when current is less than 120 mA, then the heat due to the winding increases the ferrite’s \mu \textrm {eff} , leading to more frequency shifting. The total size ( $L \times W \times H$ ) is 8~\textrm {mm} \times 8~\textrm {mm} \times 1.1 mm. [ABSTRACT FROM PUBLISHER]

The system-on-package (SoP) approach to design wireless front ends has proven to optimize the tradeoff between performance and size. In this paper, two new and highly compact bandpass filters are presented that show the greatest degree of miniaturization of any bandpass filters presented to date when their volume is measured in guided wavelengths. A novel packaging technique where most of the filter components are folded beneath the resonator inductors allows for this level of miniaturization. The filters are designed as lumped-element equivalent circuits and fabricated in standard low-permittivity low-temperature cofired ceramic technology that makes them suitable for embedding within a mass-producible SoP solution. In addition, electric and magnetic couplings are used to create finite transmission zeros that enhance the selectivity of these filters. The second-order filter demonstrates an insertion loss of 2.2 dB and a 3-dB bandwidth of 11% at a center frequency of 1.524 GHz. Meanwhile, the fourth-order implementation shows an insertion loss of 4.92 dB and a 3-dB bandwidth of 6.6% at a center frequency of 1.521 GHz. In both cases, the agreement between simulations and measurements is excellent. Careful analysis of individual capacitors and inductors comprising the filters is provided to explain the link between process parameters and actual measured performances. [ABSTRACT FROM PUBLISHER]

This paper first presents cylindrical low-temperature co-fired ceramic (LTCC) resonator configurations as a means of achieving high-Q values at millimetric frequencies in a reduced-size structure. The resonator contains a rectangular air cavity that only partially fills its volume. Simple analytical expressions are derived, which relate the via waveguide (VWG) heterogeneous structures to their conventional cylindrical resonator counterparts through the use of effective radius and dielectric constant (aeff and ∈eff). A parametric analysis is then carried out showing the effects of the available design parameters on resonant frequency and Q. Excellent agreement between measured and analytical results is obtained. Finally, a low-cost miniaturized low phase-noise free-running oscillator is proposed by employing the novel high-Q VWG resonator in the same LTCC package that houses the monolithic oscillator active circuit. A 24-GHz low phase-noise oscillator is then carried out with an output power of 13.3 dBm and a phase noise of -106 dBc/Hz at 100-kHz offset, which is among the best results ever published for a free-running K/K a-band oscillator. [ABSTRACT FROM AUTHOR]

An experimental-low temperature cofired ceramic (LTCC) ferrite tape system is characterized using circuits that are fabricated from the very material under test. Such in situ circuits provide data that are thought to be more representative of the performance obtainable by more complicated circuitry that will eventually be made from the same material using the same fabrication method. Emphasis is placed on simple measurements that can be performed using a minimum amount of equipment. For the first time, a compact in situ LTCC solenoid transformer is used to measure the magnetostatic properties of the ferrite, yielding a measured saturation flux density of 230 mT, a remanence of 136 mT, and a coercivity of 688 Aim. The peak linear relative permeability of the ferrite is 97 and its Curie temperature is low, only 117 °C. A novel two-port line-connected ring resonator is used to characterize the material in the 6-40 GHz range. At frequencies above 20 Gift, the relative permittivity of the ferrite is 11.0, whereas its loss tangent ranges from 0.002 to 0.004, demonstrating the ferrite's suitability for use in microwave and millimeter-wave circuitry. [ABSTRACT FROM AUTHOR]