Search

Voltage controlled crystal oscillators (VCXO) using CMOS varactors are investigated. The varactor is operated in the so-called inversion mode (I-Mode) with source and drain bounded together. Its capacitance is evaluated by the HSPICS-Fourier methodology. The performances of capacitance under small-signal and large-signal operations are classified. Then the frequency tuning and the related phase noise are explored. It is found that the larger the tuning coefficient has, the worse the phase noise has in I-mode varactor. The chip is fabricated by the TSMC 0.35um CMOS process. The total area including pad is 1.358 × 1.350 mm and the current consumption in the core circuit is 300uA. [ABSTRACT FROM PUBLISHER]

Design and analysis of a terahertz frequency tripler whose band ranges from 106GHz to 114GHz are reported in this paper. The tripler uses single commercially available MA46H146 GaAs Flip-Chip multiplier varactor. The circuit design, simulation and optimization of the frequency tripler are carried out with HFSS and ADS. When the input power is 20dBm, the simulated conversion efficiency of the tripler is greater than 10% in the entire bandwidth, reaches 23% at 110.1GHz and has a peak value of 29.7%. [ABSTRACT FROM PUBLISHER]

A design of divide-by-2 injection-locked frequency divider (ILFD) and LC_VCO is presented in this work. The ILFD circuit is realized with a differential CMOS LC-tank oscillator with an injection MOS. The proposed design accomplishes wide tuning range frequency by using binary weighted switched varactor in addition to a linearly varying varactor. It can be applied for multi-standard wireless applications. The tuning range of the ILFD carrier frequency is from 1.2 to 1.75GHz. At the injection signal power of 0 dBm, the locking range is about 1.1 GHz from the incident frequency 2.4 to 3.5 GHz. The phase noise of the locked output is −123.4 dBc/Hz at 1 MHz offset frequency. The power consumption of total circuit is 22.98mW. Only 6.19 mW is consumed by the ILFD. [ABSTRACT FROM PUBLISHER]

In this paper, a novel end-loaded quarter-wavelength resonator is investigated for the designs of wideband tunable bandstop filter (BSF). The novelty of the resonator lies in that two tunable capacitors are added to the two ends of the resonator, and then its resonant frequency can be bi-directionally tuned. As a result, the theoretical frequency tuning range can be significantly extended to approximately twice that of the conventional tunable quarter-wavelength resonator. For demonstration, the proposed resonator is employed to design a wideband tunable BSF. As expected, the tuning range is 53.5% for the BSF. Both the simulated and measured results are presented, good agreement has been observed. [ABSTRACT FROM PUBLISHER]

A passive 480-GHz frequency doubler based on accumulation-mode MOS varactor in CMOS process is reported. Using a compact partially-coupled ring structure, the doubler achieves a simultaneous broadband matching for fundamental and 2nd-harmonic signals. With optimized gate length and oxide thickness, the MOS varactor achieves a dynamic cutoff frequency of 870GHz while sustaining large voltage swing for high power generation. At 480-GHz output frequency, the doubler has a measured minimum conversion loss of 14.3dB and an unsaturated output power of 0.23mW. The simulated 3-dB output bandwidth is 70GHz (14.6%). The doubler is fabricated using 65-nm low power bulk CMOS technology and consumes zero DC power. [ABSTRACT FROM PUBLISHER]

A digital tuning approach for adjusting the frequency of a resonator in a bandpass integrated transmission-line based SDM (BP-ITLSDM) is presented. The resonators are tuned by switching the length of an integrated transmission line (ITL) instead of the conventional varactor tuning. It makes the compensation process for the finite gain bandwidth (GBW) of transconductances independent from the tuning process of the resonator. Additionally, the same resonator gain is achieved at different tuned frequencies. To reduce the effect of parasitics and digital control patterns, common mode signal switching (CMS) is employed. The simulations are performed for a 2.5GHz resonator using a 16-segmented switchable ITL with unit length of 430um. A frequency tuning range of 1.5GHz and a finite GBW compensating range up to half of the sampling rate 10GHz is achieved in a 0.25um BiCMOS SiGe technology. [ABSTRACT FROM PUBLISHER]

In this paper, we realized a steering antenna using a type of active metamaterial with tunable refractive index in L-band. The controllable left-handed metamaterial is based on periodically printed sub-wavelength metallic resonant patterns with embedded microwave varactors. By controlling the phase properties of the radome, the antenna exhibits continuous scanning capability in a range of ±30° under very simple DC voltage control that does not exceed 10 volts. Simulation results on such structure are given, which agrees well with the theoretical analysis. This antenna has a simple structure, is very easy to configure the beam direction, and has a low cost. [ABSTRACT FROM PUBLISHER]

In this paper, we realized a steering antenna using a type of active metamaterial with tunable refractive index in L-band. The controllable left-handed metamaterial is based on periodically printed sub-wavelength metallic resonant patterns with embedded microwave varactors. By controlling the phase properties of the radome, the antenna exhibits continuous scanning capability in a range of ±30° under very simple DC voltage control that does not exceed 10 volts. Simulation results on such structure are given, which agrees well with the theoretical analysis. This antenna has a simple structure, is very easy to configure the beam direction, and has a low cost. [ABSTRACT FROM PUBLISHER]

High-Q factor voltage controlled oscillators (VCO) need a wide tuning range and low phase noise over gigahertz ranges of frequency which depends on the tunability of the capacitors in the LC tank circuit. The reasons behind the development of a micro electro mechanical (MEM) varactor were the difficulties encountered in the realization of on-chip variable capacitors having low phase noise and high quality factors with a wide tuning range in the span of frequencies over process and temperature variations. This paper presents an efficient closed-form model for determination of the pull-in voltage in a surface micro machined MEM varactor which is a factor directly affecting the tunability of the device. The nonlinear spring hardening effects associated with proper load-deflection characteristics of clamped plates and the electrostatic spring softening effects due to the parallel-plate and fringing field capacitances have been taken into account with the dimensions of the device optimized through finite element analysis (FEA). [ABSTRACT FROM PUBLISHER]

A novel thin film Barium-Strontium-Titanate(BST) varactor-tuned single spiral notch filter is presented. The thin film BST varactor device operation is based on the nonlinear dielectric tunability of the BST thin film sandwiched between two metal layers in a conductor-backed coplanar waveguide (CBCPW) transmission line configuration. The considered spiral-structured tunable inductors of different sizes in the bottom metal layer are designed for integration into the notch filters. A schematic model is created to extract the electrical parameters. The s-parameters measured from fabricated devices have a reasonable agreement with the results extracted from the schematic model. The fabricated notch filter can reach 20.52dB rejection while the insertion loss at pass-band is less than 5dB with a tunable center frequency from 10.83GHz to 12.96GHz as the dc bias increases from 0V to 4V. [ABSTRACT FROM PUBLISHER]

The main objective for this research is to develop an antenna that can shift its frequency over a broadband. A coplanar waveguide (CPW) antenna was designed with the center conductor of the CPW transmission line connected to a bowtie patch. The size of the antenna is 6mm × 6 mm. The antenna is tuned with a barium strontium titanate (BST) thin film varactor which can tune the device from 5.75 GHz to 6.1937 GHz by adjusting the DC bias from 0 to 10V. [ABSTRACT FROM PUBLISHER]

This paper presents a novel electronically tunable half mode substrate integrated waveguide (HMSIW) cavity resonator at microwave frequency. The resonant frequency of the cavity is tuned with different DC biasing voltages applied over a varactor coupled to the cavity. This structure has been analyzed with a full-wave software Ansoft-HFSS12. To validate our analyses, an X-band reflective tunable HMSIW cavity resonator is designed and fabricated as an experimental example. According to simulated and measured results, an equivalent circuit of the resonator with the varactor is obtained. Measured results show that the tuning range of the resonator is about 360 MHz with the loaded QL of 85 and the unloaded QU of 150. The proposed resonator can be used to design tunable devices such as microwave and millimeter-wave voltage controlled oscillator (VCO). [ABSTRACT FROM PUBLISHER]

This paper proposes the method of varactor cross-coupling with adaptive bias. The capacitive cross-coupling neutralization contributes to improve power gain and reverse isolation. The optimized capacitance of cross-coupled PA depends heavily on the input power. Thus, the varacter is used and adaptive bias is obtained by the feedback of the input power. The 2-stage differential power amplifier is fabricated in a 65nm CMOS process. It achieves the PAE at P1dB of 7.7% and peak PAE of 12.5% from a 1.2V power supply. The effect of varactor cross-coupling neutralization with adaptive bias is validated. [ABSTRACT FROM PUBLISHER]

Latest technologies in wireless communications present new challenges on antenna design. Reduced size antennas with self reconfigurable ability are characteristical of smart antennas. This paper presents the practical implementation issues of making an automatic smart antenna tuning system varying the resonant frequency of the antenna using a varactor. The primary parameter for changing varactor’s value is antenna’s VSWR which is monitored by a uC. Additionally, the uC also controls the varactor’s value. [ABSTRACT FROM AUTHOR]

This paper presents a novel structure for tunable dielectric resonator (DR) filters using varactor tuning. The varactor is mounted outside the filter housing while interacting with the resonator through a PCB circuit board. The concept is analyzed both theoretically and experimentally. A prototype tunable DR filter employing this concept is designed, implemented and tested. The filter operates at 5 GHz with a bandwidth of 60 MHz demonstrating a tuning range of more than 300 MHz and a spurious free window larger than 1.0 GHz. [ABSTRACT FROM PUBLISHER]

Transmission lines with time-varying reactance exhibit interesting behaviors such as parametric amplification and mixing [1]. In this paper, such a transmission line realized with distributedly modulated capacitors (DMC) is demonstrated with its active conversion gain, low noise figure as well as non-reciprocity. DMC is offered a great potential to operate in an RF front-end either as a broadband low-noise amplifier (LNA) or an integrated circulator. A practical implementation is presented with varactors and microstrip lines connected in double-balanced fashion. DMC shows in simulations that 9 dB gain with below 0.5 dB noise figure over the input signal frequency of 1 to 6 GHz is achievable when it is optimized for gain and noise performance. Alternatively when the circuit is optimized for isolation, greater than 13 dB isolation can be achieved from 500 MHz to 1.8 GHz, which has been verified with the experiment. [ABSTRACT FROM PUBLISHER]

A tunable bandpass filter with a wide tuning range is presented. The proposed filter is composed of two modified parallel-coupled lines and one varactor-loaded stub. The measured results show that a broad tuning range of 41.7%, from 0.95 to 1.45 GHz, was achieved. Within the tuning range, the insertion loss is from 2.4 to 2.9 dB and the return loss is greater than 15dB. [ABSTRACT FROM PUBLISHER]

This paper proposed a novel varactor-tuned dual-band filter with constant absolute bandwidth. It is composed of a pair of half-wavelength open-ended resonators and a pair of quarter-wavelength short-ended resonators. The resonators utilized two different methods to control the electric and magnetic coupling so as to achieve constant absolute bandwidth. A dual-band tunable filter is designed, and the measured results of the filter illustrate the effectiveness of this design method. [ABSTRACT FROM PUBLISHER]

In this paper, a Half Mode Substrate Integrated Waveguide (HMSIW) phase shifter is proposed, designed, fabricated and measured. The proposed phase shifter employs a HMSIW hybrid junction and provides continuous control of phase shifting by using varactor diodes. Good agreement between measured and simulated results indicate that the proposed structure has a wide phase tuning range, flat insertion loss and low reflection coefficient over a wide band frequency. [ABSTRACT FROM PUBLISHER]

This letter presents the design and implementation of a continuous phase shifter MMIC using a 0.18-μm standard CMOS process. It consists of five stages of reflection-type phase shifter (RTPS), where each stage contains a over-coupling broadside coupler loaded with accumulation-mode MOSFET varactors. The measured maximum phase tuning range reaches 302° at 40 GHz and remains greater than 180° up to 100 GHz. Within 40–100 GHz, the average insertion loss is 13 dB, while the loss variation across the phase tuning range is ±4.3 dB at 40 GHz, and decreases to ± 2.5 dB at frequencies beyond 60 GHz. This chip has a compact size of 0.36×0.5 mm2 and consumes zero DC power. [ABSTRACT FROM PUBLISHER]

Metamaterials are artificial structures that can be designed to exhibit specific electromagnetic properties not commonly found in nature. In recent years metamaterials with simultaneously negative permeability and permittivity otherwise known as left handed materials (LHM) or double negative materials, have attracted the attention of scientific and engineering communities. This paper reports active reconfigurable ion implanted left-handed metamaterials for radio frequency and microwave nonlinear circuit applications, demonstrating the advantage of the ion implantation technology in making low-cost pulse shaping, harmonic generation and tunable filters for wireless communication systems. [ABSTRACT FROM AUTHOR]