Digital frequency tuning technique based on current division for integrated active RC filters

A novel digital frequency tuning technique is presented for integrated active RC filters. Instead of varying the values of the capacitors or resistors as in traditional approaches, the proposed technique achieves frequency tuning by dividing the currents that flow from resistors to virtual grounds. Current division is performed through a digitally programmable current division network added at each virtual ground. The technique features compact size, wide tuning range and high linearity. Transistor level simulation results are presented to demonstrate the technique.     

为传感器测量提供灵活的频率调谐功能的数字波形发生器

可变电阻传感器可以将一个固定的直流激励电压或电流变换成一个被测量直接函数的电流或电压，在另一类传感器中移动物体或流体可以通过改变一个LC电路的电感值或电容值来产生一个传感器信号，图1示出了一个基本的交流驱动调谐电路接近式传感器1即L和C)以及采样电阻器R。     

A low-voltage 40-GHz complementary VCO with 15% frequency tuning range in SOI CMOS technology

The design of a low-voltage 40-GHz complementary voltage-controlled oscillator (VCO) with 15% frequency tuning range fabricated in 0.13-/spl mu/m partially depleted silicon-on-insulator (SOI) CMOS technology is reported. Technological advantages of SOI over bulk CMOS are demonstrated, and the accumulation MOS (AMOS) varactor limitations on frequency tuning range are addressed. At 1.5-V supply, the VCO core and each output buffer consumes 11.25 mW and 3 mW of power, respectively. The measured phase noise at 40-GHz is -109.73 dBc/Hz at 4-MHz offset from the carrier, and the output power is -8 dBm. VCO performance using high resistivity substrate (/spl sim/300-/spl Omega//spl middot/cm) has the same frequency tuning range but 2 dB better phase noise compared with using low resistivity substrate (10 /spl Omega//spl middot/cm). The VCO occupies a chip area of only 100 /spl mu/m by 100 /spl mu/m (excluding pads).     

Design of low-voltage CMOS continuous-time filter with on-chipautomatic tuning

A technique for designing a low-voltage continuous-time active filter is presented in this paper. In this technique, current sources are added to the inverting or noninverting op-amp terminals such that the op-amp input common-mode voltages can be set close to one of the supply rails to allow low-voltage operation. An automatic frequency and Q tuning technique is proposed for tuning the active filter using programmable capacitor arrays (PCAs). The proposed tuning technique does not require any peak detectors, which are difficult to implement at a low supply voltage. Instead, it uses a few analog comparators, a digital comparator, and a few binary counters to adjust the PCAs. To demonstrate the proposed techniques, a 1-V 1-MHz second-order filter fabricated in a conventional 1.2-μm CMOS process is presented. For a 5-kHz input signal, the filter achieves a THD of -60.2 dB for a peak-to-peak output voltage of 600 mV. The frequency tuning range is between 585 kHz and 1.325 MHz. The measured power consumption for the filter alone consumes about 0.52 mW and for the entire system consumes about 1.6 mW for a supply voltage of ±0.5 V     

Frequency tuning technique for Gm-C filters

A frequency tuning technique based on an envelope locked loop is proposed for Gm-C filters. A degenerated integrator is used as the master circuit to eliminate the problems associated with the DC offset of the operational transconductance amplifier (OTA)     

Flicker noise cancellation technique for low-voltage direct-conversion mixers

A technique to reduce the low-frequency noise figure of direct-conversion mixers is presented. Unlike previous techniques, the proposed method is suitable for low-voltage and low-power applications. The results presented demonstrate that the proposed technique can significantly improve the low-frequency noise figure of the mixer, while other performance parameters remain intact.     

Bitline GND sensing technique for low-voltage operation FeRAM

In this sensing technique, pMOS charge transfer maintains the bitline level near the GND when the plate line goes high. It gives 0.5-V higher readout voltages across the cell capacitors and enables a 0.4-V higher differential amplitude in a 512-cell per bitline structure compared with the conventional high-impedance bitline sensing technique. Using the shifted bias plate line layout, only eight cells and eight sense amplifiers per cell mat are activated, and simulations show 8.06 mW at 3 V and 5 MHz, which is about the same power consumption as the conventional device     

Positive feedback frequency compensation for low-voltage low-power three-stage amplifier

The use of a new frequency compensation scheme for a three-stage operational amplifier is presented. The use of a positive feedback compensation (PFC) is employed to improve frequency response when compared to nested Miller compensation. A set of design equations is derived to give insight into the sizing of the amplifier. In addition, some characteristics relevant to the low-voltage low-power circuits using operational amplifiers have been modeled. Finally, an optimization algorithm was used with the purpose of extracting the most efficient solution. The PFC is especially suitable for driving large capacitance loads. It improves frequency response, slew rate (SR), and settling time. Small compensation capacitors make it appropriate for integration in commercial CMOS processes. With an active area of 0.03 mm/sup 2/ and working at 1.5 V, the circuit dissipates 275 /spl mu/W, has more than a 100-dB gain, a gain bandwidth of 2.7 MHz, and 1.0 V/spl mu/s average SR while driving a 130-pF load. Both measured frequency and transient step response show that the amplifier is stable.     

Digital I and Q generation for OFDM

The amplitude and phase distortions introduced by analogue inphase and quadrature generation in an orthogonal frequency division multiplexing (OFDM) transmitter or receiver are analysed. These results are then used in the development of an optimum digital generation system which offers very good performance with low complexity     

A low-power low-voltage OTA-C sinusoidal oscillator with a large tuning range

A new operational transconductance amplifier and capacitor based sinusoidal voltage controlled oscillator is presented. The transconductor uses two cross-coupled class-AB pseudo-differential pairs biased by a flipped voltage follower, and it exhibits a wide transconductance range with low power consumption and high linearity. The oscillator has been fabricated in a standard 0.8-/spl mu/m CMOS process. Experimental results show a frequency tuning range from 1 to 25 MHz. The amplitude is controlled by the transconductor nonlinear characteristic. The circuit is operated at 2-V supply voltage with only 1.58 mW of maximum quiescent power consumption.     

Macro-micro frequency tuning antenna for reconfigurable wireless communication systems

A small-sized (radiator sime10times8 mm) microstrip monopole antenna for reconfigurable macro-micro frequency tuning is presented. The proposed antenna operates in WiBro (2.3-2.4 GHz) and WLAN 802.11a/b (2.4-2.48 GHz/5.15-5.35 GHz) service bands with a constant antenna gain. Two frequency tuning diodes, a pin diode and a varactor, are incorporated into a meander type radiator. The pin diode is used for frequency switching (macro-tuning) between 2 GHz band and 5 GHz band. In addition, the varactor is used for frequency tuning (micro-tuning) within wireless service bands (2.3-2.48 GHz and 5.15-5.35 GHz) to produce constant antenna gain     

一种数字调频系统专用频率合成芯片的设计

针对汽车音响收音数字调谐系统的实例,介绍了一种广播用双波段锁相环频率合成芯片的设计方法。设计采用串行端口按位传输数据的方式,在程序分频器部分使用了吞脉冲技术,不仅简化了控制器的操作,同时也获得了较高的频率分辨力,实际产品具有广泛的市场前景。     

Fiber-birefringence tuning technique for an erbium-doped fiber ringlaser

A method of tuning fiber lasers is described and demonstrated. The state of polarization in the fiber is controlled using the strain-induced birefringence of several fiber coils. The fiber laser was tuned over a 33-nm tuning range by rotating a single fiber-coil halfwave plate     

A self-calibration technique for wide tuning range PLLs

This paper presents a new calibration technique applicable for wide tuning range phase locked loops (PLLs) using very low gain voltage controlled oscillators (VCO). This technique uses the PLL main loop for the coarse and fine tuning of the VCO. Instead of using two loops which has been reported in previous works, in this work the VCO tuning voltage is used to calibrate the VCO switch capacitor array. Since the proposed calibration circuit operates in a closed loop form, it can be used for channel selection as well as adjusting for process, voltage and temperature variations. In addition, the calibration circuit has been used to set the VCO tail current in order to optimize VCO phase noise. A prototype frequency synthesizer has been designed in 0.18-μm CMOS process to work for a frequency range from 2.4 to 2.72 GHz. Simulation results show that using the proposed technique, a spur level of ?60 dB at 5 MHz offset from carrier was achieved while having negligible power overhead.     

Electron tuning of frequency in gyrotrons

Formulas for shifts of gyrotron autooscillation frequency due to change of electron beam parameters are presented. The frequency shifts can be commensurable with the frequency band of the beam-unloaded cavity. The autooscillation frequency is most sensitive to the change of the magnetic field, less to the change of the anode voltage and least to the the change of the beam voltage. Experiments presented are in satisfactory agreement with the theory.     

Electronic frequency tuning of TRAPATT oscillators

Experimental results of a novel electronically tunable microstrip Trapatt oscillator employing varactor diodes arc presented. A tuning range of 20 MHz, limited by the low voltage breakdown of the varactor diodes and the number of tuning stages used, for an oscillator with a centre frequency of 1.6 GHz and an output power of 9 W, was observed and found to be in good agreement with theory.     

New Q enhancement technique of low pole frequency bandpass filter using single-ended operational amplifiers

A new bandpass filter with low pole frequency (ω_p) and high selectivity (Q) derived from state variable technique is described. Design equations and sensitivity figures are also presented.     

具有频率调谐的GNSS接收机双模复数滤波器

A fifth/seventh order dual-mode OTA-C complex filter for global navigation satellite system receivers is implemented in a 0.18μm CMOS process.This filter can be configured as the narrow mode of a 4.4 MHz bandwidth center at 4.1 MHz or the wide mode of a 22 MHz bandwidth center at 15.42 MHz.A fully differential OTA with source degeneration is used to provide sufficient linearity.Furthermore,a ring CCO based frequency tuning scheme is proposed to reduce frequency variation.The measured results show that in narrow-band mode the image rejection ratio（IMRR）is 35 dB,the filter dissipates 0.8 mA from the 1.8 V power supply,and the out-of-band rejection is 50 dB at 6 MHz offset.In wide-band mode,IMRR is 28 dB and the filter dissipates 3.2 mA.The frequency tuning error is less than±2%.     

A dual-mode complex filter for GNSS receivers with frequency tuning

A fifth/seventh order dual-mode OTA-C complex filter for global navigation satellite system receivers is implemented in a 0.18 fxm CMOS process. This filter can be configured as the narrow mode of a 4.4 MHz bandwidth center at 4.1 MHz or the wide mode of a 22 MHz bandwidth center at 15.42 MHz. A fully differential OTA with source degeneration is used to provide sufficient linearity. Furthermore, a ring CCO based frequency tuning scheme is proposed to reduce frequency variation. The measured results show that in narrow-band mode the image rejection ratio (IMRR) is 35 dB, the filter dissipates 0.8 mA from the 1.8 V power supply, and the out-of-band rejection is 50 dB at 6 MHz offset. In wide-band mode, IMRR is 28 dB and the filter dissipates 3.2 mA. The frequency tuning error is less than ±2%.     

An analytical procedure for critical frequency tuning of FIR filters

A novel analytical procedure for the tuning of finite-impulse response (FIR) filters is introduced. The tuning procedure adjusts a single frequency of the frequency response to the desired value while preserving the nature of the filter. The impulse responses of the original and of the final filter are related by the transformation matrix. Two examples in the analytical design of notch FIR filters demonstrate the usefulness of the proposed tuning procedure.