Measured Center Frequency Research Articles

Multilayer cross‐coupled resonator bandpass filters fabricated on low temperature cofired ceramic substrates

AbstractMultilayer cross‐coupled open‐loop resonator bandpass filters have been developed on low temperature cofired ceramic substrates. The center frequency of the designed bandpass filter is at 5.2 GHz and the fractional bandwidth is 4%. The measured center frequency is 5.2 GHz, passband insertion loss is 1.46 dB, and fraction bandwidth is 2%. The measured frequency responses of the fabricated bandpass filters are in agreement with simulated results. By constructing multilayer structure, a compact bandpass filter can be realized. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1977–1979, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22580

PMN-PT single crystal, high-frequency ultrasonic needle transducers for pulsed-wave Doppler application

High-frequency needle ultrasound transducers with an aperture size of 0.4 mm were fabricated using lead magnesium niobate-lead titanate (PMN-33% PT) as the active piezoelectric material. The active element was bonded to a conductive silver particle matching layer and a conductive epoxy backing through direct contact curing. An outer matching layer of parylene was formed by vapor deposition. The active element was housed within a polyimide tube and a 20-gauge needle housing. The magnitude and phase of the electrical impedance of the transducer were 47 omega and -38 degrees, respectively. The measured center frequency and -6 dB fractional bandwidth of the PMN-PT needle transducer were 44 MHz and 45%, respectively. The two-way insertion loss was approximately 15 dB. In vivo high-frequency, pulsed-wave Doppler patterns of blood flow in the posterior portion and in vitro ultrasonic backscatter microscope (UBM) images of the rabbit eye were obtained with the 44-MHz needle transducer.

A Low-Noise $K$-Band VCO Based on Room-Temperature Ferroelectric Varactors

This paper reports a K-band voltage-controlled oscillator based on room-temperature ferroelectric varactors. The circuit is realized as a hybrid module where flip-chip transistors are mounted on a silicon substrate with integrated ferroelectric varactors and passive circuitry. The size of the module is 4.7times2.2 mm2. The measured center frequency is 16.5 GHz with a linear tunability of 6.7% and an output power of 3 dBmplusmn1 dB over the tuning range. The measured phase noise at center frequency is -95 dBc/Hz at 100-kHz offset. Another version of the oscillator is measured operating at 19.6 GHz with a tunability of 3.3% and a phase noise of -102 dBc/Hz at 100-kHz offset

Novel compact low-loss millimeter-wave filters using micromachined overlay and inverted overlay coplanar waveguide transmission lines with defected ground structures

This paper describes two types of novel compact low-loss millimeter-wave filters using an overlay coplanar waveguide (OCPW) line for lowpass filters and an inverted overlay coplanar waveguide (IOCPW) line for bandpass filters with periodic defected ground structures (DGSs). The OCPW and IOCPW lines are utilized to reduce the conductor and the substrate dielectric loss of the transmission lines. Also, these lines can provide a wide impedance range by controlling the overlapped area. The DGSs implemented on the transmission line have the role of size reduction and harmonic suppression of the filters. The combination of transmission lines having suspended structures and DGSs can provide great potential in terms of compact size, band rejection property and low-loss characteristics. The proposed filters are fabricated by using a micromachining technology and their RF performances are measured and analyzed. One of the proposed filters is a lowpass filter with a five-section stepped impedance topology having a periodic high–low impedance section. In this filter, the low impedance section is composed of the OCPW line with dumbbell-shaped DGSs and its length can be reduced by 52.7% compared to the OCPW line without DGSs. The measured insertion loss of this filter is lower than 0.2 dB up to 9 GHz, and significant spurious bands are not observed up to 40 GHz, resulting in a wide stop band. The other work that is presented here deals with a pi-shaped bandpass filter. This filter consists of three high impedance sections and two low impedance sections, and the line length of the high impedance section can be reduced by using the IOCPW line with spiral-shaped DGSs. The measured center frequency of the fabricated filter is 19 GHz, and the passband loss is 2.3 dB at the measured center frequency. The use of DGSs on the transmission line also enables us to suppress effectively the third-order harmonic component at 57 GHz.

Ray-based acoustic localization applied in a highly reverberant environment

Acoustic localization techniques for finding and identifying broadband sound sources is of interest for studying low event rate cavitation, and other hydroacoustic noise sources, in water tunnels and other reverberant environments. The measured center frequency and bandwidth of the acoustic pulse from the collapse of a small isolated cavitation bubble are both approximately 100 kHz, and the measured pulse duration is ∼15−20 μs. Here, a sound projector is used to mimic such a pulse, and 16 receiving hydrophones are used to estimate the source location in the test section of a laboratory water tunnel when neither the timing of the event nor the exact signal waveform is presumed known. Fortunately, the direct-path signal arrival is generally distinct enough at each receiver for acoustic localization. The signal coda is not used in the present effort. The received direct-path signals are cross correlated between hydrophones to obtain arrival time differences. These arrival time differences are used in conjunction with a simple, straight-ray acoustic model to estimate the source location in three dimensions. Extension of this effort to use of first reflections and frequency domain modeling of the water tunnel for matched-field processing will be discussed as well. [Sponsored by ONR codes 333, 321.]

Real-Time 3D Laparoscopic Ultrasonography

We have previously described 2D array ultrasound transducers operating up to 10 MHz for applications including real time 3D transthoracic imaging, real time volumetric intracardiac echocardiography (ICE), real time 3D intravascular ultrasound (IVUS) imaging, and real time 3D transesophageal echocardiography (TEE). We have recently built a pair of 2D array transducers for real time 3D laparoscopic ultrasonography (3D LUS). These transducers are intended to be placed down a trocar during minimally invasive surgery. The first is a forward viewing 5 MHz, 11 x 19 array with 198 operating elements. It was built on an 8 layer multilayer flex circuit. The interelement spacing is 0.20 mm yielding an aperture that is 2.2 mm x 3.8 mm. The O.D. of the completed transducer is 10.2 mm and includes a 2 mm tool port. The average measured center frequency is 4.5 MHz, and the -6 dB bandwidth ranges from 15% to 30%. The 50 omega insertion loss, including Gore MicroFlat cabling, is -81.2 dB. The second transducer is a 7 MHz, 36 x 36 array with 504 operating elements. It was built upon a 10 layer multilayer flex circuit. This transducer is in the forward viewing configuration and the interelement spacing is 0.18 mm. The total aperture size is 6.48 mm x 6.48 mm. The O.D. of the completed transducer is 11.4 mm. The average measured center frequency is 7.2 MHz, and the -6 dB bandwidth ranges from 18% to 33%. The 50 omega insertion loss is -79.5 dB, including Gore MicroFlat cable. Real-time in vivo 3D images of canine hearts have been made including an apical 4-chamber view from a substernal access with the first transducer to monitor cardiac function. In addition, we produced real time 3D rendered images of the right pulmonary veins from a right parastemal access with the second transducer, which would be valuable in the guidance of cardiac ablation catheters for treatment of atrial fibrillation.

A 44-MHz wideband switched-capacitor bandpass filter using double-sampling pseudo-two-path techniques

A fully differential wideband sixth-order switched-capacitor bandpass filter is designed for channel selection in cable TV applications. A modified double-sampling pseudo-two-path technique is proposed to achieve a second-order wideband bandpass filter with a single opamp. Implemented in a standard double-poly four-metal 0.35-/spl mu/m CMOS process and operated at 176-MHz sampling frequency, the filter achieves a measured center frequency of 44 MHz with a bandwidth of 6.28 MHz and a dynamic range of 58.3 dB at 3% IM3. The filter consumes 92.5mW at a single 3.0-V supply and occupies a chip area of 0.52 mm /sup 2/.

Development of superconducting bandpass delta-sigma analog-to-digital converter

This paper recounts the development of a superconducting bandpass delta-sigma (ΔΣ) modulator for direct analog-to-digital conversion of radio frequency signals in the GHz range. The modulator design benefits from several advantages of superconducting electronics: high-Q resonators, fast Josephson comparators, naturally quantized single flux quantum pulses, and high circuit sensitivity. The measured center frequency (2.23 GHz), sampling rate (up to 45 GHz), dynamic range (greater than 57 dB over a 19.6 MHz bandwidth), and input sensitivity (−17.4 dBm full-scale) of the bandpass modulator are the highest reported to date in any technology. The SNR (49 dB over a 20.8 MHz bandwidth) is limited by the frequency resolution of the measurement but still exceeds the SNRs of semiconductor modulators with comparable center frequencies. The design of the modulator test chip and the high speed testing methodology are reviewed. Finally, the paper examines the prospects for improved performance with more advanced modulator architectures.

GaAs 기판을 이용한 5.8 GHz 소형 필터제작

A microstrip filter has been designed and fabricated in hairpin form on a GaAs substrate and its characteristics such as the insertion loss, return loss, and bandwidth have been investigated. The presented filter is realized with relatively small size, 4.5 by 3.6 mm. The insertion loss and return loss of the filter are 1.17 dB and 30 dB, respectively. The filter exhibits 3 dB-bandwidth of 350 MHz at the center frequency, 5.890 GHz. The experimental results show good agreement with the numerical ones. However, the measured center frequency is about 100 MHz higher than the designed one.

Metallic tunable photonic crystal filter for terahertz frequencies

A tunable metallic photonic crystal filter has been fabricated by deep reactive ion etching of a silicon substrate followed by metallization. The filter plate’s two-layer orthogonal grid structure and integrated mounting lugs were fabricated from a single silicon wafer in two etching steps. A three-step metallization process (evaporation, sputtering, and electroplating) ensured all surfaces were coated with gold to greater than 4.6 times the skin depth at the frequencies of interest. The filter employs a mechanical tuning mechanism, the performance of which was predicted with rigorous full-vector electromagnetic simulations (finite-difference time domain). The prototype has been characterized at frequencies of 70–150 GHz using free-space measurement techniques. Its measured center frequency shifts from 144 to 137 GHz for 300 μm lateral shift of one of the plates, and it has an insertion loss of less than 1 dB.

Superconducting microstrip hairpin filter with BaTiO/sub 3/ patches

A high temperature superconducting microstrip line hairpin filter with BaTiO/sub 3/ has been designed and fabricated. The design and the filter simulation were done using Genesys software from Eagleware. In order to maximize the quality factor of the filter, the microstrip lines were made of superconducting YBa/sub 2/Cu/sub 3/O/sub 7/. A YBa/sub 2/Cu/sub 3/O/sub 7/ thin film was deposited on a LaAlO/sub 3/ single crystal substrate using pulsed laser deposition. The microstrip line hairpin filter was then patterned and tested at cryogenic temperatures. A BaTiO/sub 3/ thin film was then deposited and patterned to form patches between the resonators. Microwave tests of the filter with and without the BaTiO/sub 3/ patches were performed at low temperatures. The filter has measured center frequency of 1.65 GHz with a bandwidth of 20 MHz. The results show the effect of using BaTiO/sub 3/ patches on top of YBa/sub 2/Cu/sub 3/O/sub 7/. The most current results on the performance of the filter will be presented.

Triple-push oscillator approach: theory and experiments

This paper presents the theory and experiments of the triple-push oscillator approach. This oscillator architecture is combined with three identical oscillator subcircuits. An analytical mode analysis is used to describe the behavior of all modes. As will be shown, odd-mode currents in each oscillator subcircuit have a 120/spl deg/ phase shift to one another and thus produce in-phase combining for the third harmonic. The time domain analysis was performed to simulate a triple-push oscillator, showing that the phenomenon of 120/spl deg/ phase shift exists among each oscillator subcircuit. To prove this concept, a 4.9-GHz hybrid bipolar junction transistor (BJT) circuit and a 28.4-GHz heterojunction bipolar transistor (BJT) MMIC chip were demonstrated. The measured results showed that the 4.9-GHz BJT triple-push oscillator delivered an output power of 1.0 dBm at 4.9 GHz with 12.0-dB fundamental rejection, and the 28.4-GHz HBT MMIC chip exhibited a measured center frequency at 28.4 GHz with an output power of -15.4 dBm, while the output powers of the fundamental and the second harmonic signals were suppressed to -21 and -34 dBm.

CMOS microelectromechanical bandpass filters

This work fabricates a laminated-suspension microelectromechanical filter, respectively, by a fully compatible CMOS 0.6 μm single poly triple metal (SPTM) process and CMOS 0.35 μm single poly quadri-metal (SPQM) process. Experimentally, due to the top metal layer being used as the etch-resistant mask during the subsequent dry etching. Therefore, this study performs maskless etching with plasma and obtains excellent results including high selectivity and full release of the structure. Additionally, the microelectromechanical filter can be driven by applying low-voltage of around 5 V and a measured center frequency of around 13.1 kHz and a quality factor of around 1871 were obtained for a single-comb resonator operated in air. The filter successful proposed herein has a monolithic integration capability with the relative electric circuits in the standard CMOS 0.35 μm process.

HTS microstrip filters using H-type resonators

We report the characteristics of a high-T/sub c/ superconductor (HTS) bandpass filter with the designed center frequency of 16.5 GHz. A YBa/sub 2/Cu/sub 3/O/sub 7-x/ (YBCO) superconducting thin film was prepared using the rf-magnetron sputtering deposition technique. The filter used in this work was composed of the "H"-type resonator (non-uniform microstrip lines). This approach has advantages for a considerably high Q-value and the compact filter structure. The impedance ratio of the "H"-type resonator was 0.5 in this work. In the measured responses, this HTS filter showed the insertion loss of -0.4 dB at maximum. The measured center frequency of our HTS bandpass filter was 16.44 GHz and the passband was from 15.91 GHz to 16.97 GHz, a bandwidth of 6.86% with 3 dB in band Chebyshev ripple. Experimental results of our filters were reported in terms of insertion loss, return loss and other various characteristics.

Experimental demonstration of a W-band (94 GHz) gyrotwystron amplifier

A four section, TE/sub 01/ mode W-band gyrotwystron amplifier has been designed, built, and tested. The circuit consists of three cavities followed by a traveling wave output section, each operating near the fundamental cyclotron frequency. The gyrotwystron has produced 50 kW peak output power, corresponding to 17.5% efficiency for a 57 kV, 5 A electron beam; the amplifier is zero drive stable at the operating point. The measured center frequency is 93.9 GHz with a full width half maximum instantaneous bandwidth of 925 MHz. These results represent a substantial improvement in the power-bandwidth product over previously demonstrated gyro amplifiers in this band. The small signal and saturated gains were 39 and 30 dB, respectively. The measured results are in good agreement with theoretical predictions.

Microelectromechanical filters for signal processing

Microelectromechanical filters based on coupled lateral microresonators are demonstrated. This new class of microelectromechanical systems (MEMS) has potential signal-processing applications for filters which require narrow bandwidth (high Q), good signal-to-noise ratio, and stable temperature and aging characteristics. Microfilters presented in this paper are made by surface-micromachining technologies and tested by using an off-chip modulation technique. The frequency range of these filters is from approximately 5 kHz to on the order of 1 MHz for polysilicon microstructures with suspension beams having a 2-/spl mu/m-square cross section. A series-coupled resonator pair, designed for operation at atmospheric pressure, has a measured center frequency of 18.7 kHz and a pass bandwidth of 1.2 kHz. A planar hermetic sealing process has been developed to enable high quality factors for these mechanical filters and make possible wafer-level vacuum encapsulations. This process uses a low-stress silicon nitride shell for vacuum sealing, and experimental results show that a measured quality factor of 2200 for comb-shape microresonators can be achieved.

Microwave measurements of effective dielectric constant of semiconductor waveguides via periodic-structure photoexcitation

In this paper a new method for measurements of the effective dielectric constant of layered or full-substrate semiconductor waveguides at microwave frequencies is presented. The light-induced generation of a photoconductivity grating within the excited waveguide section is utilized. Incoming swept-frequency signals produce a stop-band reflection spectrum which exhibits a dominant major-lobe peak value at the grating center frequency. The effective dielectric constant is calculated from a simple analytical expression by substituting the measured center frequency. Theoretical background, error estimation, and an example are presented.

The design of a 3-V 900-MHz CMOS bandpass amplifier

A new bandpass amplifier which performs both functions of low-noise amplifier (LNA) and bandpass filter (BPF) is proposed for the application of 900-MHz RF front-end in wireless receivers. In the proposed amplifier, the positive-feedback Q-enhancement technique is used to overcome the low-gain low-Q characteristics of the CMOS tuned amplifier. The Miller-capacitance tuning scheme is used to compensate for the process variations of center frequency. Using the high-Q bandpass amplifier in the receivers, the conventional bulky off-chip filter is not required. An experimental chip fabricated by 0.8-/spl mu/m N-well double-poly-double-metal CMOS technology occupies 2.6/spl times/2.0 mm/sup 2/ chip area. Under a 3 V supply voltage, the measured quality factor is tunable between 2.2 and 44. When the quality factor is tuned at Q=30, the measured center frequency of the amplifier is tunable between 869-893 MHz with power gain 17 dB, noise figure 6.0 dB, output 1 dB compression point at -30 dBm, third-order input intercept point at -14 dBm, and power dissipation 78 mW.

Design techniques for tunable transresistance-C VHF bandpass filters

In this paper, a tunable wideband linear transresistance (R/sub m/) amplifier is proposed and analyzed. Using the tunable R/sub m/ amplifier, a new transresistance-capacitor (R/sub m/-C) differentiator is designed. Considering the intrinsic capacitances of the MOS transistors as filter elements, this R/sub m/-C configuration can he regarded as a very high frequency (VHF) bandpass biquadratic filter. The proposed biquad has a simple structure and thus occupies a small chip area and consumes little power. Moreover, higher-order VHF bandpass filters can be realized by directly cascading the biquads. Experimental results have successfully proven the capability of the proposed new filter implementation method in realizing VHF bandpass filters with the center frequency higher than 100 MHz when C/sub d/=1 pF. The deviations of the measured center frequency f/sub o/ and quality factor Q of the fabricated bandpass filter from the simulated results are less than 8%. The deviation of the center frequency can be post-tuned by adjusting the control voltages V/sub CN/ and V/sub CP/ of the tunable R/sub m/ amplifier. With 1 pF differentiating capacitor, the center frequency of the fabricated VHF R/sub m/-C bandpass filters can be tuned in a wide range larger than 30 MHz. The measured maximum signal level is 25 mV/sub rms/ and the dynamic range is 47 dB. The chip area is 0.05 mm/sup 2/ and power consumption is 5.05 mW with /spl plusmn/2.5 V power supply.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Quasi-optical millimeter-wave band-pass filters using high-T/sub c/ superconductors

Quasioptical millimeter-wave band-pass filters using YBa/sub 2/Cu/sub 3/O/sub 7/ high-T/sub c/ superconducting films were fabricated on MgO and LaAlO/sub 3/ substrates. Transmitted power through the filter was investigated in the 75 GHz to 110 GHz frequency range at temperatures ranging from 15 to 300 K. At 15 K the measured center frequency and the bandwidth of the superconducting filter were 92 GHz and 0.85 GHz, respectively. Measurements of YBa/sub 2/Cu/sub 3/O/sub 7/ filters were compared with similar filters fabricated using gold. At 15 K and 92 GHz, an improvement of 75% in the quality factor of the superconducting filter was obtained compared with a similar gold filter.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>