Unloaded Q-factor Research Articles

A Flip-Chip Assembled Millimeter-Wave Oscillator Stabilized with a Micromachined Cavity on a Thin-Film Substrate

A low-cost 47 GHz microwave integrated circuit (MIC) oscillator stabilized with a micromachined cavity is presented using a thin-film substrate with a flip-chip interconnection. A GaAs pseudomorphic high electron-mobility transistor (pHEMT) was flip-chip assembled on the thin-film substrate as an active device to generate negative resistance. A micromachined cavity, which is employed to stabilize a 47-GHz MIC oscillator as a series-feedback element, is fabricated using a low-cost silicon micromachining technique and flip-chip assembled on the thin-film substrate with integrated passives. The fabricated cavity shows an unloaded Q-factor of 671 with a resonant frequency of 46.91 GHz. The cavity oscillator developed shows an output power of about 11.5 dBm and a low phase noise of -95 dBc/Hz at 1 MHz offset with an oscillation frequency at 47.06 GHz, which is a 17-dB improvement over a free running MIC oscillator. This work demonstrates the great potential of a thin-film substrate with a flip-chip interconnection for a low-cost and high-performance mm-wave system-on-package (SOP) technology.

Broadband Dielectric Properties of the Ba<sub>3</sub>MnTa<sub>2</sub>O<sub>9 </sub>Complex Perovskites

We report the results of the broadband dielectric constant and loss tangent of the new complex perovskites Ba3MnTa2O9 with the test frequency f in different ranges from 1 kHz to 15 GHz. For the test frequency f below 1 MHz, the dielectric constant and loss tangent of the specimens were measured using a LCR meter with four-terminal configuration. The measurements at frequencies between 50 MHz and 1 GHz were performed by the lumped impedance method, which uses an impedance analyzer to measure the complex impedance of the specimen. At frequencies above 1 GHz, two samples with diameter 9 mm and different thicknesses (2.73 mm and 5.42 mm) were measured by a home-made Hakki-Coleman resonator. The TE011 resonant peaks were found and identified with an Agilent PNA net-work analyzer. The dielectric constants were found to remain almost constant with the test frequency at room temperature. The calculated values of the real part dielectric constants are 17.74 and 17.53 at 9.86 GHz and 15.43 GHz, respectively. The unloaded Q factors deduced from curve fitting of the peaks are both around 200.

MEASUREMENT OF RF PCB DIELECTRIC PROPERTIES AND LOSSES

This paper presents the calculations of transmission line loss factor by extracting from the Q-factor measurement of the quarterwavelength open stub resonators over the designed frequency and other resonant frequencies. A comparison of the loss factor of the design frequency with other resonant frequencies of each of the stub’s quarter-wave resonances is provided in this paper. The radiation and discontinuity losses are undesirably included in the unloaded Q-factor measurement and it shows that the unloaded Q-factor is not repeatable at different designed frequency. The implementation of the loss factor measurement by quarter-wavelength open stub resonators is becoming more and more important to be considered with the increase of using the electronic circuits operating at high frequencies. † This author is also with Department of Electronic Engineering, Tam Kang University, 151 Ying-chuan Road, Tamsui, Taipei County, Taiwan 25137, R.O.C.

APPLYING CRITICAL-POINTS METHOD IN THE PRESENCE OF PHASE SHIFT DUE TO FEED LINE

The critical-points method is adopted for measuring unloaded Q-factor of microwave resonators in the presence of phase shift caused by the feed line. The result is calculated from four frequencies of three points in the resonator’s impedance trace. In fact, the resonator’s impedance trace rotates in Smith Chart by the phase shift. If Q-factor were gotten directly from the measured impedance including feed line rather than the equivalent impedance of the resonator without feed line, the performance of measurement will be impaired. To de-embed the phase shift, objective function was introduced to find the proper rotation angle caused by the feed line instead of calibration using extra measurement. Another advantage of the proposed method lies in the fact that no special attention is needed to distinguish magnetic coupling and electric coupling. The effectiveness of the proposed method was demonstrated by one set of simulation data and two measurement examples, namely, a low Q dielectric resonator and a high Q hollow cylindrical cavity.

High q-factor distributed bragg reflector resonators with reflectors of arbitrary thickness

The Bragg reflection technique improves the Q-factor of a resonator by reducing conductor and dielectric losses. This is achieved by designing a low-loss inner resonant region (usually free space) surrounded by an outer anti-resonant region made of distributed Bragg reflector layers. In this paper we develop a simple non-Maxwellian model and apply it to design three distinct cylindrical Bragg resonators based on the same set of single-crystal sapphire plates and rings by changing only the dimension of the cavity that supports the structure. To accomplish this, the simple model allows an arbitrary thickness for either the horizontal or the cylindrical dielectric reflectors by relaxing the condition that they must be lambda/4 thick. The model also allows for higher-order field variations in both the resonant and the anti-resonant regions. The resonators were constructed and experimental results were compared with the simple model and the rigorous method of lines analysis. For the fundamental mode, an unloaded Q-factor of 234,000 at 9.7 GHz was obtained. This is larger than that for a whispering gallery mode resonator. The resonator also exhibited a greatly reduced spurious mode density when compared to an overmoded whispering gallery mode resonator.

HTS split open-ring resonators with improved power-handling capability for reaction-type transmitting filters

Novel planar construction of high-temperature superconducting (HTS) filters that improve power-handling capability is proposed. Split open-ring resonators are developed to be used in reaction-type transmitting filters that have very sharp bandstop characteristics. Resonator structures to achieve high-unloaded Q-factors and low radiation as well as low surface current densities in the passband are numerically investigated for 5 GHz band operation. Low surface current densities reduce the generation of intermodulation distortions. Measurements confirm an unloaded Q-factor of 68 000 and third intermodulation-distortion of −82 dBc at 30 dBm input power.

Exciting traveling waves in high Q structures using microstrip

Exciting traveling waves in high- Q resonant structures can simplify low noise oscillator designs and also has applications for newly proposed Lorentz invariance tests. In this work we use microstrip probes to excite traveling waves in a sapphire dielectric resonator. Previous work has indicated that matching microstrip probes to a sapphire resonator can be a difficult requirement. A model has been developed, which takes into account leakage of the microstrip line in the reverse direction to which we excite the traveling wave. From such a model we can define the standing wave ratio (SWR). By comparing the model with experiment we find that we can excite a traveling wave with an SWR of 0.35 and an unloaded Q-factor of 1.5 × 1 0 5 in a WGH 12 , 0 , 2 mode at 9.997 GHz, in a sapphire cylinder of 5 cm diameter and 3 cm height. From the model, we also propose new oscillator designs for low noise applications.

Microstrip Slow-Wave Open-Loop Resonator Filters with Reduced Size and Improved Stopband Characteristics

This paper presents a new class of microstrip slow-wave open-loop resonator filters with reduced size and improved stopband characteristics. A comprehensive treatment of both ends loaded with triangular and rectangular ends is described, leading to the invention of a microstrip slow-wave open-loop resonator. Two-resonator and four-resonator bandpass filters are designed at the operating frequency of about 2 GHz, and a bandwidth of 60 MHz. The size of the slow-wave open-loop resonator is optimized from the standpoint of the unloaded Q-factor. The filters are not only compact in size due to the slow-wave effect, but also have a wider upper stopband resulting from the dispersion effect. The filter designs of this type are described in details. The experimental results are demonstrated and discussed.

On the electrical characteristics of complementary metamaterial resonators

In this letter, a method to obtain the electrical characteristics of complementary split ring resonators (CSRRs) coupled to planar transmission lines is presented. CSRRs have been recently proposed by some of the authors as new constitutive elements for the synthesis of metamaterials with negative effective permittivity, and they have been applied to the fabrication of metamaterial-based circuits in planar technology. The method provides the electrical characteristics of CSRRs (including the intrinsic resonant frequency and the unloaded Q-factor), as well as the coupling capacitance between line and CSRRs, and the parameters of the host line. Parameter extraction from the proposed method is applied to two different structures corresponding to the basic cells of left handed (LH) and negative permittivity lines. The method is of actual interest for the design of microwave circuits and metamaterials based on these complementary resonant particles

Dielectric characterisation of Barium Fluoride at cryogenic temperatures using TE 011 and quasi TE 0mn mode dielectric resonators

Barium Fluoride (BaF 2), mainly used in optical applications, has similar properties to those of CaF 2 but better stability under environmental conditions. In this paper, we report measurements of loss tangent and the real part of the relative permittivity ε r of single crystal BaF 2 in the temperature range from 14 to 290 K at frequencies of 8, 10.4, 12.1, 17.6, 21.1 and 24.4 GHz. Microwave properties of BaF 2 were determined by measurements of the resonance frequency and the unloaded Q-factor of TE 011 and quasi TE 0mn modes cylindrical cavities containing the sample under test. Two techniques namely Hakki–Coleman Dielectric Resonator and dielectric post resonators have been used for characterizing the dielectric material. Losses due to the uncalibrated cables and adaptors inside the cryocooler are accounted in the calculation of unloaded Q-factor using the Transmission Mode Q-Factor data processing technique. The permittivity of BaF 2 exhibited a 5% increase from 6.9 (14 K) to 7.35 (290 K). The loss tangent increased from 1 × 10 −5 to 1.1 × 10 −4 over the measured temperature range, 14–290 K at a frequency of 10.4 GHz. The measured microwave properties show that BaF 2 can be used in many microwave devices.

RF HBT oscillators with low-phase noise and high-power performance utilizing a (/spl lambda//4/spl plusmn//spl delta/) open-stubs resonator

This paper presents a new type of transmission-line resonator and its application to RF (microwave and millimeter-wave) heterojunction bipolar transistor (HBT) oscillators. The resonator is a parallel combination of two open stubs having length of lambda/4plusmndelta(deltaLtlambda), where lambda is a wavelength at a resonant frequency. The most important feature of this resonator is that the coupling coefficient (betaC) can be controlled by changing delta while maintaining unloaded Q-factor (Q u) constant. Choosing a small value of delta allows us to reduce betaC or equivalently to increase loaded Q-factor (Q L). Since coupling elements such as capacitors or electromagnetic gaps are not needed, betaC and QL can be precisely controlled based on mature lithography technology. This feature of the resonator proves useful in reducing phase noise and also in enhancing output power of microwave oscillators. The proposed resonator is applied to 18-GHz and 38-GHz HBT oscillators, leading to the phase noise of -96-dBc/Hz at 100-kHz offset with 10.3-dBm output power (18-GHz oscillator) and -104-dBc/Hz at 1-MHz offset with 11.9 dBm (38-GHz oscillator). These performances are comparable to or better than state-of-the-art values for GaAs- or InP-based planar-circuit fundamental-frequency oscillators at the same frequency bands

Permittivity measurements at millimeter wave frequencies using dielectric rod resonator excited by NRD-guide

A method of measuring the relative complex permittivity ( ɛ r = ɛ′ – jɛ″, tan δ = ɛ″/ ɛ′) for low-loss dielectric materials at millimeter wave frequencies has been developed, using a dielectric rod resonator excited by the nonradiative dielectric waveguide (NRD-guide). Relative permittivity ( ɛ′) and loss factor (tan δ) of the rod specimen are determined by the resonant frequency ( f 0) and unloaded Q-factor ( Q u) of a TE 0m1 mode resonator. The effective conductivity ( σ) of conducting plates for short-circuiting the rod resonator is determined using TE 021 and TE 02 δ mode sapphire resonators. Temperature dependence of ɛ′ and tan δ of sapphire and cordierite ceramics were evaluated at 60 GHz. This method has been adopted as the Japanese Industrial Standard (JIS R 1660-3) and is being prepared for the IEC international standard. Several standardized specifications are presented.

Self-assembled screen-printed microwave inductors

The fabrication and measured performance of a self-assembled microwave inductor, created using a novel screen-printing technology, is reported for the first time. Real surface micromachining is performed using screen printing, by introducing a unique sacrificial layer. The self-assembled inductor demonstrated a significantly increased unloaded Q-factor and first self-resonant frequency.

Provisional model technique in the FDTD analysis of high-Q resonators

We propose A technique for extracting Q-factors and resonant frequencies of resonators from signal models constructed using samples provided by a time-domain simulator. The method involves two models. The first model is a provisional one and serves one to generate additional samples that prevent the original sequence from being corrupted during signal processing. The second model is the final one and gives directly the quality factors and the resonant frequencies for the structures of interest. We show the application of the new technique to the fast time domain analysis of structures with the unloaded Q-factor exceeding 106.

Microwave dielectric properties of BaO−2CeO 2− nTiO 2 ceramics

The BaO–2CeO 2– nTiO 2 ceramics with n = 3 , 4 and 5 have been prepared with CeO 2 as starting material. The ceramics have been characterized using scanning electron microscopy, X-ray diffraction, Raman and X-ray photoelectron spectroscopy techniques. The microwave dielectric properties have been measured using standard dielectric resonator techniques. BaO–2CeO 2–3TiO 2 (123), BaO–2CeO 2–4TiO 2 (124) and BaO–2CeO 2–5TiO 2 (125) ceramics showed dielectric constants of 38, 27 and 32, respectively. All the ceramics showed fairly good unloaded Q-factors. 124 and 125 compounds exhibited low τ f values, while 123 showed a high τ f value.

Computations of unloaded Q0-Factor and resonant frequency of the TE011 mode Hakki–Coleman dielectric resonators with coupling structures using ANSOFT HFSS

Microwave characterization of materials using dielectric resonators is based on measurements of the Q-factor of the resonator containing a sample under test and on the loss equation for the test structure. The loss equation contains geometrical factors, which are calculated assuming an ideal metallic cavity of the resonator. In this paper a rigorous analysis of cylindrical parallel plate dielectric resonators has been performed to assess the influence of the presence of coupling holes and cables on the unloaded Q-factor and resonant frequency. Calculations have been done for the TE011 mode resonators with differing cavity to dielectric diameter ratio, conductivity of the cavity material, loss tangent and relative permittivity of the dielectric rod, position of the coupling loops and size of the coupling cables. Results have shown that Qo-factors calculated for real resonators were smaller than Qo-factors for ideal resonators. Also this paper presents a brief history of analysis of dielectric resonators.

High-Q sapphire resonator with distributed Bragg reflectors

A new ring resonator design based on Bragg reflectors is presented. The resonator implements the fundamental TE01γ mode in a cylindrical sapphire dielectric, which is confined by the addition of radial and axial sapphire Bragg reflectors. It is shown that an unloaded Q-factor of 187 000 can be obtained for a frequency near 9 GHz.

Dual-mode filters with grooved/splitted dielectric resonators for cellular-radio base stations

Dual-mode filters for cellular-radio base stations require resonators with a high unloaded Q-factor, a wide spurious-free operating window and the possibility of high coupling values either to input or between resonators. These features are obtained by employing a cavity resonator loaded by grooved/split ceramic disks, which allows insertion of probes and/or tuning/coupling screws where the field is highly concentrated. In this paper, cavity resonator behavior, intercavity couplings, and filter computer-aided tuning are discussed in detail. Experimental results of an eight-pole transmit filter confirm the suitability of the proposed resonator for realizing cellular-radio base stations filters for UNITS and IMT-2000 applications.

Miniaturized hairpin superconducting filters for telecommunications applications

AbstractUsing miniaturized hairpin resonators and following the Chebychev model, we have designed and fabricated superconducting filters with a centre frequency of 2.2 GHz and a bandwidth of 5 MHz. The measured unloaded Q‐factor of the resonator fabricated on LaAlO3 using YBCO thin film is 47,000 at 60 K. Prototype filters with three and four poles have been realized by using Nb thin films. The measured performances do not show appreciable degradations up to 10 dBm. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 35: 360–362, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10607

A micromachined cavity resonator for millimeter-wave oscillator applications

High stability and low phase noise oscillators are key components in millimeter-wave (MMW) systems. Using microelectromechanical system (MEMS) technology, the silicon cavity resonator has been developed for MMW oscillator applications. Thanks to the superior Q-factor of the cavity over planar resonators, low phase noise and high stability is expected. The fabricated, micromachined cavity showed an unloaded Q-factor of 120 and Ka-band voltage controlled oscillator (VCO) coupled with the cavity resonators showed a phase noise improvement of more than 15 dB over free-running oscillators (FROs). To the best of our knowledge, this is the first experimental demonstration of a high electron mobility transistor (HEMT) microwave monolithic integrated circuit (MMIC) oscillator combined with a micromachined cavity resonator.