Design of a low-power ZigBee receiver front-end for wireless sensors

This paper describes the design of a low cost, low-power ZigBee receiver for wireless sensor networks. The receiver consists of a low-noise amplifier, a pair of down-conversion mixers, and a pair of variable-gain low-pass filters. The LNA has a single-ended input, eliminating the need for an off-chip balun, a differential output, allowing it to drive a double-balanced mixer, and it uses noise cancellation to improve its noise performance. The mixers are double-balanced passive mixers to improve the receiver linearity and decrease its power consumption and flicker noise. Finally, the filter is a third-order Butterworth G_m-C filter with a variable input transconductor to provide gain programmability for the receiver. The design is made using 130 nm CMOS technology with 1.2 V supply. Simulation results show that the receiver can achieve a sensitivity level of −97 dBm while consuming only 6 mA.     

A 20-Gb/s wideband AGC amplifier with 26-dB dynamic range in 0.18-μm SiGe BiCMOS

This paper presents a 20-Gb/s automatic gain control (AGC) amplifier in a 0.18-μm SiGe BiCMOS for high-speed applications. The proposed AGC amplifier compactly consists of a folded Gilbert variable-gain amplifier (VGA), a post amplifier (PA), a 50-Ω output buffer, and AGC loop including an open-loop peak detector (PD), a RC low-pass filter (LPF), and an error amplifier (EA). The AGC amplifier achieves the broadband characteristic by utilizing inductive peaking and capacitive degeneration as well as f_T-doubler techniques to overcome the large parasitic capacitances. The proposed AGC circuits together with a linear VGA exhibits a wide gain control range of 45 dB for the received signal strength indication (RSSI). The measured AGC amplifier achieves a maximum gain of 21 dB and a -3-dB bandwidth (BW) of 20.6 GHz, which can support up to 25.4-Gb/s data rate. For the pseudorandom bit sequence (PRBS) length 2³¹–1 with a bit-error rate (BER) of 10⁻¹² at 20 Gb/s, the measured input dynamic range is 26 dB (20–400mV_pp) and the peak-to-peak data jitter is less than 8 ps. The AGC amplifier consumes a power of 160 mW from a 3.3-V supply voltage and occupies an area of 850 μm × 850 μm.     

A low-distortion CMOS IF VGA with linear-in-dB control and temperature compensation

A CMOS intermediate-frequency (IF) variable-gain amplifier (VGA) is presented in this paper. A transconductance linearization scheme is proposed for the VGA core based on a signal-subtracting structure to achieve low distortion. Temperature-independent decibel-linear gain control characteristic is achieved by an exponential voltage generator based on transfer characteristics of differential pair. The whole VGA, including a highly-linear output stage, is fabricated in 0.25 μm CMOS technology. Measurements show that the VGA provides a total gain control range of 43 dB with less than 1.2 dB error over 0–80°C, and a constant 3-dB bandwidth of 100 MHz. The third-order intermodulation (IM3) distortion at differential output of 2 V_PP is better than −55 dB. The VGA dissipates 22.6 mA averagely from 3.3 V supply, and occupies approximately 0.53 mm².     

一种新型的5GHz自适应偏置及可变增益低噪声放大器

该文提出了一种新型的自适应偏置及可变增益低噪声放大器(LNA),利用电荷泵(亦称电压倍增器)将LNA输出信号转换成与LNA射频输入信号功率成比例变化的直流信号,以此信号同时反馈控制LNA的偏置和增益,来实现自适应偏置以及可变增益低噪声放大器, 从而极大地改善了LNA的输入线性范围。鉴于5GHz频率下,Bipolar相对于CMOS更好的频率特性和低噪声特性,该项研究采用了BiCMOS工艺,实现了低于3.0dB的噪声系数(高增益状态下)和大约13dBm的输入三阶交调点IIP3的控制范围以及大于15dB的增益控制范围。     

Performance of convergence-based variable-gain control of optical storage drives

In this paper, a method for the performance assessment of a variable-gain control design for optical storage drives is proposed. The variable-gain strategy is used to overcome well-known linear control design trade-offs between low-frequency tracking properties and high-frequency noise sensitivity. A convergence-based control design is proposed that guarantees stability of the closed-loop system and a unique bounded steady-state response for any bounded disturbance. These favourable properties, guaranteed by virtue of convergence, allow for a unique performance evaluation of the control system. Moreover, technical conditions for convergence are derived for the variable-gain controlled system and a quantitative performance measure, taking into account both low-frequency tracking properties and high-frequency measurement noise sensitivity, is proposed. The convergence conditions together with the performance measure jointly constitute a design tool for tuning the parameters of the variable-gain controller. The resulting design is shown to outperform linear control designs.