Showing papers on "Center frequency published in 2009"
TL;DR: In this paper, a multistage narrowband optical pole-zero notch filter is presented, which allows for reconfigurable and independent tuning of the center frequency, null depth, and bandwidth for one or more notches simultaneously.
Abstract: We present a fully tunable multistage narrowband optical pole-zero notch filter that is fabricated in a silicon complementary metal oxide semiconductor (CMOS) foundry. The filter allows for the reconfigurable and independent tuning of the center frequency, null depth, and bandwidth for one or more notches simultaneously. It is constructed using a Mach-Zehnder interferometer (MZI) with cascaded tunable all-pass filter (APF) ring resonators in its arms. Measured filter nulling response exhibits ultranarrow notch 3 dB BW of 0.6350 GHz, and nulling depth of 33 dB. This filter is compact and integrated in an area of 1.75 mm2. Using this device, a novel method to cancel undesired bands of 3 dB bandwidth of < 910 MHz in microwave-photonic systems is demonstrated. The ultranarrow filter response properties have been realized based on our developed low-propagation loss silicon channel waveguide and tunable ring-resonator designs. Experimentally, they yielded a loss of 0.25 dB/cm and 0.18 dB/round trip, respectively.
160 citations
TL;DR: In this article, two different slot resonators are embedded into the arc shaped ground plane of the circular disk patch antennas in order to obtain the desired band-rejection around 5.8 GHz.
Abstract: Planar ultrawideband (UWB) antennas with on-ground band-notched structures are studied in this paper. Two different slot resonators, which feature quarter-wavelength and half-wavelength configurations, are embedded into the arc shaped ground plane of the circular disk patch antennas in order to obtain the desired band-rejection around 5.8 GHz. Their principles and characteristics are analyzed and compared in detail providing designers with in-depth understanding and useful design information. By choosing the quarter-wavelength slot resonator, the first spurious stopband can be pushed up to 3 f 0 (f 0 stands for the center frequency of the notch) and this antenna retains a super wide working band which spans from 1.62 GHz to 17.43 GHz. Performance in both the frequency domain and time domain for this antenna has been investigated carefully. The transmission response of a transceiving antenna system and their corresponding transient analysis are discussed at the end of this paper.
134 citations
TL;DR: In this article, a frequency-doubling optoelectronic oscillator (OEO) using a polarization modulator (PolM) was proposed and experimentally demonstrated.
Abstract: A novel realization of a frequency-doubling optoelectronic oscillator (OEO) using a polarization modulator (PolM) is proposed and experimentally demonstrated. In the proposed system, the PolM in combination with two optical polarizers connected via two polarization controllers (PCs) is operating as a two-output intensity modulator. One output of the intensity modulator is connected to the radio-frequency port of the PolM, to form an optoelectronic loop for the generation of a microwave signal with the fundamental frequency determined by the center frequency of a narrowband electronic filter. The other output of the intensity modulator provides a fundamental or frequency-doubled optically modulated microwave signal depending on the static phase term introduced by the PC before the polarizer. The proposed OEO is experimentally demonstrated. A fundamental microwave signal at 10 GHz or a frequency-doubled microwave signal at 20 GHz is generated. The phase noise performance of the generated microwave signal is also investigated.
117 citations
TL;DR: In this paper, an all-digital, non-coherent, pulsed-UWB transmitter is presented, which uses an energy-efficient, single-ended digital ring oscillator.
Abstract: This paper presents an all-digital, non-coherent, pulsed-UWB transmitter. By exploiting relaxed center frequency tolerances in non-coherent wideband communication, the transmitter synthesizes UWB pulses from an energy-efficient, single-ended digital ring oscillator. Dual capacitively coupled digital power amplifiers (PAs) are used in tandem to attenuate low frequency content typically associated with single-ended digital circuits driving single-ended antennas. Furthermore, four level digital pulse shaping is employed to attenuate RF sidelobes, resulting in FCC compliant operation in the 3.5, 4.0, and 4.5 GHz IEEE 802.15.4a bands without the use of any off-chip filters or large passive components. The transmitter is fabricated in a 90 nm CMOS process and occupies a core area of 0.07 mm2 . The entirely digital architecture consumes zero static bias current, resulting in an energy efficiency of 17.5 pJ/pulse at data rates up to 15.6 Mb/s.
108 citations
TL;DR: An all-digital RF signal generator using DeltaSigma modulation and targeted at transmitters for mobile communication terminals has been implemented in 90 nm CMOS, providing a 50 MHz bandwidth at a 1 GHz center frequency.
Abstract: An all-digital RF signal generator using DeltaSigma modulation and targeted at transmitters for mobile communication terminals has been implemented in 90 nm CMOS. Techniques such as redundant logic and non-exact quantization allow operation at up to 4 GHz sample rate, providing a 50 MHz bandwidth at a 1 GHz center frequency. The peak output power into a 100 Omega diff. load is 3.1 dBm with 53.6 dB SNDR. By adjusting the sample rate, carriers from 50 MHz to 1 GHz can be synthesized. RF signals up to 3 GHz can be synthesized when using the first image band. As an example, UMTS standard can be addressed by using a 2.6 GHz clock frequency. The measured ACPR is then 44 dB for a 5 MHz WCDMA channel at 1.95 GHz with output power of -16 dBm and 3.4% EVM. At 4 GHz clock frequency the total power consumption is 120 mW (49 mW for DeltaSigma modulator core) on a 1 V supply voltage, total die area is 3.2 mm2 (0.15 mm2 for the active area).
99 citations
TL;DR: The basic reasons for the limitation of the tuning range in millimeter-wave VCOs are shown and the improvement by using two (instead of one) varactor pairs is demonstrated.
Abstract: A SiGe millimeter-wave VCO with a center frequency around 80 GHz and an extremely wide (continuous) tuning range of 24.5 GHz ( ap 30%) is presented. The phase noise at 1 MHz offset is -97 dBc/Hz at the center frequency (and less than -94 dBc/Hz in a frequency range of 21 GHz). The maximum total output power is about 12 dBm. A cascode buffer improves decoupling from the output load at reasonable VCO power consumption (240 mW at 5 V supply voltage). A low-power frequency divider (operating up to 100 GHz) provides, in addition, a divided-by-four signal. As a further intention of this paper, the basic reasons for the limitation of the tuning range in millimeter-wave VCOs are shown and the improvement by using two (instead of one) varactor pairs is demonstrated.
96 citations
TL;DR: In this paper, a quad-mode dielectric resonator filter using a simple cylinder resonator is proposed for both wireless and satellite applications using a four-pole single cavity filter.
Abstract: This paper introduces for the first time a quad-mode dielectric resonator filter, using a simple cylinder resonator A four-pole single cavity filter is designed, simulated, and fabricated based on this quadruple mode resonator Additionally, a new type of dual-mode dielectric resonator filters is introduced, using the same cylindrical resonator cut in half along its axis Center frequency control, intra/inter/input-coupling mechanisms, tuning, and spurious improvement methods are discussed, showing versatility of the proposed structures to realize different filtering functions and specifications Measured results are presented for practical filters, employing the proposed quad-mode and dual-mode resonators The dielectric resonator filters presented in this paper offer a significant size and mass reduction in comparison with conventional dielectric resonator filters They promise to be useful for both wireless and satellite applications
90 citations
TL;DR: In this paper, a reconfigurable miniaturized-element frequency-selective surface (FSS) is presented, which consists of two periodic arrays of metallic loops on either side of a very thin dielectric substrate.
Abstract: A reconfigurable miniaturized-element frequency-selective surface (FSS) is presented in this paper. A standard waveguide measurement setup is used to evaluate the performance of the design. The proposed FSS consists of two periodic arrays of metallic loops, with the same periodicity, on either side of a very thin dielectric substrate. The tuning of the reconfigurable surface is shown numerically to be possible by incorporating tuning varactors into the structure. Using varactors on both layers, a reconfigurable frequency response is achieved, which has two modes of operation: bandstop and bandpass. In addition to two completely different modes of operation, the center frequency, as well as the bandwidth of the response can be tuned independently. Frequency tunability with a constant bandwidth over 3-3.5 GHz is shown. A bandwidth tuning at a fixed center frequency is also demonstrated. Simulation results are verified experimentally by fabricating prototypes of the design at S-band loaded with lumped capacitors. To demonstrate the tunability, different pairs of fixed-valued capacitors, as opposed to varactors, are used in a waveguide measurement setup to avoid difficulties associated with biasing varactors in the waveguide.
89 citations
TL;DR: A 7-GHz CMOS voltage controlled ring oscillator that employs multiloop technique for frequency boosting is presented in this paper, which permits lower tuning gain through the use of coarse/fine frequency control.
Abstract: A 7-GHz CMOS voltage controlled ring oscillator that employs multiloop technique for frequency boosting is presented in this paper. The circuit permits lower tuning gain through the use of coarse/fine frequency control. The lower tuning gain also translates into a lower sensitivity to the voltage at the control lines. Fabricated in a standard 0.13-mum CMOS process, the proposed voltage-controlled ring oscillator exhibits a low phase noise of -103.4 dBc/Hz at 1 MHz offset from the center frequency of 7.64 GHz, while consuming a current of 40 mA excluding the buffer.
86 citations
01 Nov 2009
TL;DR: A sixth-order RF bandpass DeltaSigma ADC operating on the 2.4 GHz ISM band, which is suitable forRF digitization is presented, and paves a possible way towards direct RF digitization receiver architectures.
Abstract: A sixth-order RF bandpass DeltaSigma ADC operating on the 2.4 GHz ISM band, which is suitable for RF digitization is presented. The bandpass loop filter is based on digitally programmable Gm-LC resonators that can be calibrated online to adjust the RF center frequency. By sampling below the input Nyquist frequency, the clock in the system was reduced to 3 GHz, allowing a large reduction of the power consumption. Implemented in a standard 90 nm CMOS process, the IC achieves 40 dB and 62 dB of SNDR and SFDR, respectively, on a 60 MHz bandwidth with 40 mW of power consumption leading to a FoM of 245 GHz/W (4.1 pJ/conversion step). This implementation paves a possible way towards direct RF digitization receiver architectures.
71 citations
TL;DR: The design and performance evaluation of a new analog CMOS cochlea channel of increased biorealism that implements a recently proposed transfer function, namely the One-Zero Gammatone filter (or OZGF), and a new low-power automatic gain control circuit that adapts the gain of the channel according to the input signal strength, thereby extending significantly its input dynamic range.
Abstract: This paper deals with the design and performance evaluation of a new analog CMOS cochlea channel of increased biorealism. The design implements a recently proposed transfer function, namely the One-Zero Gammatone filter (or OZGF), which provides a robust foundation for modeling a variety of auditory data such as realistic passband asymmetry, linear low-frequency tail and level-dependent gain. Moreover, the OZGF is attractive because it can be implemented efficiently in any technological medium-analog or digital-using standard building blocks. The channel was synthesized using novel, low-power, class-AB, log-domain, biquadratic filters employing MOS transistors operating in their weak inversion regime. Furthermore, the paper details the design of a new low-power automatic gain control circuit that adapts the gain of the channel according to the input signal strength, thereby extending significantly its input dynamic range. We evaluate the performance of a fourth-order OZGF channel (equivalent to an 8th-order cascaded filter structure) through both detailed simulations and measurements from a fabricated chip using the commercially available 0.35 mum AMS CMOS process. The whole system is tuned at 3 kHz, dissipates a mere 4.46 muW of static power, accommodates 124 dB (at < 5% THD) of input dynamic range at the center frequency and is set to provide up to 70 dB of amplification for small signals.
TL;DR: In this article, a phase-locked-loop (PLL)-based power system harmonic estimation algorithm is proposed, which uses an analysis filter bank and multirate processing, and the filter bank is composed of bandpass filters.
Abstract: This paper describes a phase-locked-loop (PLL)-based power systems harmonic estimation algorithm, which uses an analysis filter bank and multirate processing. The filter bank is composed of bandpass filters. The initial center frequency of each filter is purposely chosen to be equal to harmonic frequencies. However, an adaptation strategy makes it possible to track time-varying frequencies as well as interharmonic components. A downsampler device follows the filtering stage, reducing the computational burden, especially because undersampling operations are performed. Finally, the last stage is composed of a PLL estimator which provides estimates for amplitude, phase, and frequency of the input signal. The proposed method improves the accuracy, computational effort, and convergence time of the previous harmonic estimator based on cascade PLL configuration.
TL;DR: In this paper, a dual-mode dual-bandpass filter for the U-NII bands is proposed and demonstrated by using a multilayer configuration, where the first and the third layers incorporate microstrip dualmode bandpass filters with operating center-frequencies of f1 = 5.2 GHz and f2 =5.8 GHz, respectively.
Abstract: A dual-mode dual-bandpass filter for the U-NII bands is proposed and demonstrated. Its effective size reduction is achieved by using a multilayer configuration. The first and the third layers incorporate microstrip dual-mode bandpass filters with operating center-frequencies of f1 =5.2 GHz and f2 =5.8 GHz, respectively. The second layer is used as a common ground plane for both filters, which also serves as a decoupling interface. Capacitive coupling transition is used to connect both filters to I/O coplanar waveguide (CPW) ports. Single and dual-band passband filter prototypes are designed, fabricated, and measured in this work, thus validating the design principle. Designed topologies of single passband filters with center frequencies of 5.2 and 5.8 GHz exhibit an out-of-band rejection better than 40 dB with a 3 dB bandwidth of 5.8% and 6%, respectively. The proposed multilayer dual-passband response with center frequencies of 5.2 and 5.8 GHz provide band-to-band isolation better than 30 dB. Measured insertion losses are lower than 2.76 dB, with 3 dB bandwidth lower than 5%.
TL;DR: In this article, a dual-band bandpass filter is presented, which is composed of generalized negative-refractive-index transmission lines realized in microstrip, and the filtering mechanism relies on all four of the generalized NRI-TLs' left-handed and right-handed passbands.
Abstract: A dual-band bandpass filter is presented. The filter is composed of generalized negative-refractive-index transmission-lines (NRI-TL) realized in microstrip. The filtering mechanism relies on all four of the generalized NRI-TLs' left-handed and right-handed passbands. Under the closed stopband condition, two passbands are achieved. A complete design procedure is described. A fabricated example measures 0.25lambdao0.25lambdao, where omegao is the wavelength of the center frequency of the stopband. Maximum insertion loss in the passbands (centered around 4 GHz) is measured at 1.5 dB.
07 Jun 2009
TL;DR: In this paper, a broadband compensating phase shifter is presented based on the substrate integrated waveguide (SIW) technology, which is a dispersive guided-wave structure, but the phase shifts generated by two different structures (the delay line and the equal-length unequal width phase shifters) have just reverse varying tendencies versus frequency.
Abstract: In this paper, a broadband compensating phase shifter is presented based on the substrate integrated waveguide (SIW) technology. The SIW is a dispersive guided-wave structure, but the phase shifts generated by two different structures (the delay line and the equal-length unequal-width phase shifter) have just reverse varying tendencies versus frequency. Thus, the complementing combination of them will make phase shift almost constant over a wide band. Detailed design equations are given following a mathematical analysis. The limitation of variation of SIW width and the tolerance issue are investigated as well. As an example, a 90° compensating phase shifter is designed on a single-layer substrate with normal PCB process at the center frequency of 30 GHz. The amplitude imbalance between the two paths is within 0.2 dB while the phase error is less than 2.5° over the frequency band from 25.1125 to 39.75 GHz, or around 49% relative bandwidth. The return loss is found to be better than 12 dB over the whole frequency band. Measured and simulated results of the proposed structure are in a good agreement. This type of SIW phase shifter is superior to all of its counterparts and increases the relative bandwidth of early designs about five times.
IBM1
TL;DR: A wideband LC PLL in 45-nm SOI CMOS technology is presented that has a center frequency of 12.4 GHz and 1.2 octave locking range and has a power consumption of 25 mW at the highest oscillation frequency.
Abstract: A wideband LC PLL in 45-nm SOI CMOS technology is presented that has a center frequency of 12.4 GHz and 1.2 octave locking range. The wideband operation is achieved by switching mutual inductances within the inductor coil of the LC oscillator. To minimize resistive switching losses, the inductor coil consists of a non-switchable primary coil and two isolated secondary coils with series switches. When the switches are closed, the overall inductance reduces because of the switched mutual inductances. Three inductor bands, each consisting of 16 switched capacitor sub-bands, span a frequency range from 7.3 to 17.5 GHz. The in-band phase noise measured after a 1/4 divider is better than -107 dBc/Hz at 1 MHz offset frequency in the entire locking range. The PLL is fully differential and its core has a power consumption of 25 mW at the highest oscillation frequency.
TL;DR: In this paper, a compact dual-band bandpass filter using short stub loaded resonators is presented, the proposed resonator possesses the advantage that its center frequency of the even mode can be flexibly controlled, whereas that of the odd mode is fixed.
Abstract: Compact dual-band bandpass filter using short stub loaded resonators is presented in this letter, the proposed resonator possesses the advantage that its center frequency of the even mode can be flexibly controlled, whereas that of the odd-mode is fixed. A dual-band filter using pseudo-interdigital SSLR is implemented with three transmission zeros. Meandering SSLR is proposed to obtain independently controlled bandwidth at each band. Two experimental examples of filters have been designed and fabricated, good agreements are shown between the simulation and the measurement. The bandpass filters have very smaller area in comparison of previous works. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 959–963, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24209
TL;DR: In this paper, a switchable thin film bulk acoustic wave resonator (FBAR) filter based on barium titanate (BTO) thin films is reported for the first time.
Abstract: A switchable thin film bulk acoustic wave resonator (FBAR) filter based on barium titanate (BTO) thin films is reported for the first time. BTO is a ferroelectric material which possesses electrostriction, giving the filter the ability to be placed in either an on state or an off state by changing the applied dc bias voltage. A 1.5 stage ladder type bandpass filter using BTO FBARs has been designed, fabricated, and measured. The application of a 15 V dc bias results in the filter being place in an on state with a center frequency of 2.14 GHz, a 40 MHz bandwidth and 6.2 dB of insertion loss. Conversely, the application of a - 3 V dc bias results in the filter being placed in an off state with 15 dB of rejection. This filter is very compact with dimensions of 40 mum by 80 mum.
TL;DR: In this article, a compact high quality factor four-pole X-band tunable quasi-elliptic bandpass filter is presented, enabled by high-Q ferroelectric barium strontium titanate capacitors and open-loop resonators.
Abstract: A compact high quality factor four-pole X-band tunable quasi-elliptic bandpass filter is presented in this letter. The filter is enabled by high-Q ferroelectric barium strontium titanate capacitors and open-loop resonators. The central frequency of 8.35 GHz and the frequency tuning range of 500 MHz (6%) are achieved with a dc bias voltage of 30 V. The selective filter has a fractional 1 dB bandwidth ranging from 5.5% up to 7.3%. The measured insertion loss and return loss are 5.7-3.5 dB and 10.2-7.9 dB, respectively, with a dc bias range of 0 to 30 V. To the best of our knowledge, this is the best analog tunable performance and selectivity in X-band.
TL;DR: Heterodyne spectro-radiometry is demonstrated for two local oscillator tuning modes: broadband tuning for transmission and emission spectroscopy of broadband absorbers (Freon 12), and broadband frequency selection in combination with fine continuous frequency tuning for high-resolution transmission spectroscope (N(2)O).
Abstract: Broadband thermal infrared heterodyne spectro-radiometry using an external cavity quantum cascade laser as a tunable local oscillator has been performed over a frequency range of more than 100 cm(-1) at a central frequency of 1190 cm(-1). Heterodyne spectro-radiometry is demonstrated for two local oscillator tuning modes: broadband tuning for transmission and emission spectroscopy of broadband absorbers (Freon 12), and broadband frequency selection in combination with fine continuous frequency tuning for high-resolution (0.021 cm(-1)) transmission spectroscopy (N(2)O). In each case concentration retrievals are performed and analyzed. The spectroradiometer noise level is demonstrated to be twenty two and eight times the fundamental shot-noise limit in the two scanning modes respectively.
07 Jun 2009
TL;DR: In this paper, a broad-band class E power amplifier (PA) is designed, manufactured and measured using a GaN HEMT device, achieving a maximum output power of 49 W with 16.3 dB power gain at the 1 dB compression point.
Abstract: In this work a broad-band class E power amplifier (PA) is designed, manufactured and measured. 400 MHz bandwidth with a center frequency of 800 MHz was realized using a GaN HEMT device. A novel and easy circuit topology is proposed for broad-band bandpass filter with integrated output matching network. Different filter types are discussed, suitable topology is chosen and design equations are shown. A maximum drain efficiency of 87.8 % (PAE = 80.6 %) is observed. Maximum output power of 49 W is measured with 16.3 dB power gain at the 1 dB compression point.
01 Jun 2009
TL;DR: In this article, an effective setup is developed to preserve the parasitic return path in EF-IBC, which shows a bandpass profile with a center frequency around 42MHz, and the body appears to be a uniform attenuator with about 15dB loss at the distance of 15cm between TX and RX.
Abstract: In this work, the experiment setup of EF-IBC is studied. An effective setup is developed to preserve the parasitic return path in EF-IBC. Characteristics of every component in an EF-IBC system are measured or derived through a combination of experiments. The measured EF-IBC channel shows a bandpass profile with a center frequency around 42MHz. The channel bandpass profile is mainly determined by the capacitive parasitic return path and the capacitive PCB leakage path. Below 100MHz, the body appears to be a uniform attenuator with about 15dB loss at the distance of 15cm between TX and RX. The channel characteristics are recombined by all the components, and match well with the direct measurement results, which verifies the decomposition method.
TL;DR: A computationally efficient numerical approach is developed to predict the mean intensity and the corresponding broadband transmission loss of a fluctuating, range-dependent ocean waveguide by range and depth averaging the output of a time-harmonic stochastic propagation model.
Abstract: The scintillation statistics of broadband acoustic transmissions are determined as a function of signal bandwidth B, center frequency fc, and range with experimental data in the New Jersey continental shelf. The received signal intensity is shown to follow the Gamma distribution implying that the central limit theorem has led to a fully saturated field from independent multimodal propagation contributions. The Gamma distribution depends on the mean intensity and the number of independent statistical fluctuations or coherent cells μ of the received signal. The latter is calculated for the matched filter, the Parseval sum, and the bandpassed center frequency, all of which are standard ocean acoustic receivers. The number of fluctuations μ of the received signal is found to be an order of magnitude smaller than the time-bandwidth product TB of the transmitted signal, and to increase monotonically with relative bandwidth B∕fc. A computationally efficient numerical approach is developed to predict the mean int...
TL;DR: In this paper, a 12-pole superconducting microstrip bandpass filter with a fractional bandwidth of 38% and a center frequency of 1455 MHz is presented for the Miyun 50m radio astronomy telescope, Beijing, China.
Abstract: A 12-pole wideband superconducting microstrip bandpass filter, which has a fractional bandwidth of 38% and a center frequency of 1455 MHz, is presented for the Miyun 50-m radio astronomy telescope, Beijing, China. A novel resonator, which can not only generate very large coupling, but also push its first spurious resonant peak away from the passband, is introduced. A new style interleaved coupling structure is proposed and successfully used in this study to realize the remarkably required strong coupling. To achieve high edge slope on the high side of the passband, as required, a single transmission zero was introduced. The filter was fabricated on a 36 mm times 30 mm times 0.5 mm double-sided YBa2Cu3O7 film deposited on an MgO substrate. The measured results showed that the filter had 0.05-dB minimum insertion loss, 0.08-dB passband ripple, and 23-dB return loss at a temperature of 40 K. The first spurious peak did not appear until 2632 MHz. The overall measured performance showed good agreement with the simulation.
07 Jun 2009
TL;DR: In this paper, a digital controlled artificial dielectric (DiCAD) differential transmission line is embedded in 90nm CMOS to digitally tune a 58-64GHz DCO.
Abstract: A digital controlled artificial dielectric (DiCAD) differential transmission line is embedded in 90nm CMOS to digitally tune a 58–64GHz DCO. DiCAD varies e r,eff from 18.8 to 32.5. A shunt open stub DiCAD provides discrete capacitive tuning with 13.1° S11 phase variation. The core oscillator is an inductively loaded differential, cross-coupled NMOS pair. Large nonlinear varactors are avoided, and the phase noise is better than −90dBc/Hz at 1MHz offset. Linear tuning bandwidth of 9.3% with a 61GHz center frequency occupying 0.01mm2 is achieved. Power consumption is 8.52mW with 1.2V.
TL;DR: In this paper, a microstrip lambda/4 interdigital stepped-impedance resonator whose impedance ratio can be low and coupling strength between adjacent resonators can be very large is proposed.
Abstract: This letter proposes a microstrip lambda/4 interdigital stepped-impedance resonator whose impedance ratio can be very low and coupling strength between adjacent resonators can be very large. On the basis of the proposed structure, one four-pole Chebyshev and one four-pole generalized Chebyshev filter with 0.05 dB equal-ripple bandwidths of 48% and 46%, respectively, are designed and fabricated. Both implemented filters have a compact size, a wide passband, a wide upper stopband, and a high spurious passband at near 5.1 times the center frequency. Good agreement between measurements and simulations is observed.
TL;DR: In this article, a 14-resonator quasi-elliptic function response with three pairs of transmission zeros (one pair for high selectivity and two pairs for flat group delay) in the cascaded quadruplet coupling structure was proposed.
Abstract: This paper reports a development of a narrowband high-temperature superconducting filter with both high selectivity and flat group delay. The filter has a center frequency of 8.625 GHz and a 3-dB bandwidth of 42 MHz (a fractional bandwidth of 0.49%). In order to achieve both high band-edge steepness and excellent group-delay flatness, we introduce a 14-resonator quasi-elliptic function response with three pairs of transmission zeros (one pair for high selectivity and two pairs for flat group delay) in the cascaded quadruplet coupling structure. We also develop a novel low radiation resonator (double-folded resonator) to reduce the parasitic coupling and meet other requirements for the 8-GHz filter. The filter was fabricated on a 2-in-diameter 0.5-mm-thick MgO wafer with double-sided YBCO films. The measured results show a midband insertion loss of 1.6 dB and a return loss better than 15.5 dB. Band-edge steepness reaches over 11.7 dB/MHz at both the high- and low-frequency edges. The 60-dB rectangle ratio is less than 1.25. The out-of-band rejection is over 70 dB at 5.98 MHz from the 3-dB band edge. The variation of group delay is less than 23 ns over 33 MHz (78.5% of 3-dB bandwidth), and less than 30 ns over 34.5 MHz (82% of 3-dB bandwidth).
TL;DR: In this article, the spontaneous decay of a multilevel atom interacting with the electromagnetic field in free space is investigated with a unitary transformation method, which is introduced in order to include all rotating and counter-rotating terms in the Hamiltonian.
Abstract: The spontaneous decay of a multilevel atom interacting with the electromagnetic field in free space is investigated with a unitary transformation method, which is introduced in order to include all rotating and counter-rotating terms in the Hamiltonian. By using the ground state of the total Hamiltonian, the evolution of the effective decay rate and the energy shift are calculated. When the atomic transition frequency is smaller than the central frequency of the spectrum, the Zeno effect dominates, and if the atomic transition frequency is larger than the central frequency, the anti-Zeno effect will dominate. The time evolution of the energy shift is obtained. The counter-rotating terms lead to a shift toward the low frequency region for the frequency distribution of the emitted photon.
Proceedings Article•
16 Jun 2009TL;DR: In this article, a highly reconfigurable radio-frequency-to-digital signal converter is presented, where the center frequency is precisely defined by a local oscillator signal, while baseband bandwidth is defined in the digital domain.
Abstract: A highly reconfigurable radio-frequency-to-digital signal converter is presented. Center frequency is precisely defined by a local- oscillator signal, while baseband bandwidth is defined in the digital domain. An SNR of greater than 59 dB across a 4-MHz bandwidth is measured across center frequencies ranging from 400MHz to 1.7GHz. An IIP3 of greater than +19dBm is measured, with an out-of-band 3-dB desensitization level of greater than +1dBm.