Ahmed A. Helmy

A 2.8-mW Sub-2-dB Noise-Figure Inductorless Wideband CMOS LNA Employing Multiple Feedback

A wideband low-noise amplifier (LNA), which is a key block in the design of broadband receivers for multiband wireless communication standards, is presented in this paper. The LNA is a fully differential common-gate structure. It uses multiple feedback paths, which add degrees of freedom in the choice of the LNA transconductance to reduce the noise figure (NF) and increase the amplification. The proposed LNA avoids the use of bulky inductors that leads to area and cost saving. A prototype is implemented in IBM 90-nm CMOS technology. It covers the frequency range of 100 MHz to 1.77 GHz. The core consumes 2.8 mW from a 2-V supply occupying an area of 0.03 mm2. Measurements show a gain of 23 dB with a 3-dB bandwidth of 1.76 GHz. The minimum NF is 1.85 dB, while the average NF is 2 dB across the whole band. The LNA achieves a return loss greater than 10 dB across the entire band and a third-order input intercept point IIP3 of - 2.85 dBm at the maximum gain frequency.

An Inductor-Less Noise-Cancelling Broadband Low Noise Amplifier With Composite Transistor Pair in 90 nm CMOS Technology

A new broadband low-noise amplifier (LNA) is proposed in this paper. The LNA utilizes a composite NMOS/PMOS cross-coupled transistor pair to increase the amplification while reducing the noise figure. The introduced approach provides partial cancellation of noise generated by the input transistors, hence, lowering the overall noise figure. Theory, simulation and measurement results are shown in the paper. An implemented prototype using IBM 90 nm CMOS technology is evaluated using on-wafer probing and packaging. Measurements show a conversion gain of 21 dB across 2-2300 MHz frequency range, an IIP3 of -1.5 dBm at 100 MHz, and minimum and maximum noise figure of 1.4 dB and 1.7 dB from 100 MHz to 2.3 GHz for the on-wafer prototype. The LNA consumes 18 mW from 1.8 V supply and occupies an area of 0.06 mm2.

A Self-Sustained CMOS Microwave Chemical Sensor Using a Frequency Synthesizer

In this paper, a CMOS on-chip sensor is presented to detect dielectric constant of organic chemicals. The dielectric constant of these chemicals is measured using the oscillation frequency shift of an LC voltage-controlled oscillator (VCO) upon the change of the tank capacitance when exposed to the liquid. To make the system self-sustained, the VCO is embedded inside a frequency synthesizer to convert the frequency shift into voltage that can be digitized using an on-chip analog-to-digital converter. The dielectric constant is then estimated using a detection procedure including the calibration of the sensor. The dielectric constants of different organic liquids have been detected in the frequency range of 7-9 GHz with an accuracy of 3.7% compared with theoretical values for sample volumes of 10-20 μL. The sensor is also applicable for binary mixture detection and estimation of the fractional volume of the constituting materials with an accuracy of 1%-2%.

CMOS Distributed Amplifiers With Extended Flat Bandwidth and Improved Input Matching Using Gate Line With Coupled Inductors

This paper presents a state-of-the-art distributed amplifier with coupled inductors in the gate line. The proposed coupled inductors, in conjunction with series-peaking inductors in cascode gain stages, provide bandwidth extension with flat gain response for the amplifier without any additional power consumption. On the other hand, gate-inductor coupling improves the input matching of the amplifier considerably. The detailed analysis and design methodology for the proposed distributed amplifier are presented. The new four-stage distributed amplifier, fabricated using an IBM 0.18-¿m complementary-metal-oxide-semiconductor process, achieves a power gain of around 10 dB, input and output return losses better than 16 and 18 dB, respectively, a noise figure of 3.6-4.9 dB, and a power consumption of 21 mW over a 16-GHz flat 1-dB bandwidth. The measured IIP3 of the amplifier is between 0.1 and 3.75 dBm across the entire band.

A CMOS Fractional-

A highly sensitive CMOS-based sensing system is proposed for permittivity detection and mixture characterization of organic chemicals at microwave frequencies. The system determines permittivity by measuring the frequency difference between two voltage-controlled oscillators (VCOs); a sensor oscillator with an operating frequency that shifts with the change in tank capacitance due to exposure to the material under test (MUT) and a reference oscillator insensitive to the MUT. This relative measurement approach improves sensor accuracy by tracking frequency drifts due to environmental variations. Embedding the sensor and reference VCOs in a fractional- N phase-locked loop (PLL) frequency synthesizer enables material characterization at a precise frequency and provides an efficient material-induced frequency shift read-out mechanism with a low-complexity bang-bang control loop that adjusts a fractional frequency divider. The majority of the PLL-based sensor system, except for an external fractional frequency divider, is implemented with a 90-nm CMOS prototype that consumes 22 mW when characterizing material near 10 GHz. Material-induced frequency shifts are detected at an accuracy level of 15 ppmrms and binary mixture characterization of organic chemicals yield maximum errors in permittivity of 1.5%.

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In this paper, a miniaturized broadband dielectric spectroscopy system is presented for permittivity detection, chemical sensing, and mixture characterization for 1-8-GHz frequency range. A sensing capacitor exposed to the material under test (MUT) is part of a true time-delay (TTD) cell excited by a microwave signal at the sensing frequency of interest. The phase shift of the microwave signal at the output of the TTD cell compared to its input is a measure of the permittivity of MUTs. For wideband and accurate sensing, TTD cells are cascaded in a reconfigurable fashion to increase the detected phase shift, especially at low frequencies. TTD cells are designed to detect permittivities within the range of 1-30 considering nonideal effects, such as electromagnetic coupling between adjacent TTD cells. Calibration using reference liquids is applied to the fabricated sensor and sensor characteristics are extracted. Permittivity detection of organic chemicals is performed in the range of 1-8 GHz with an error less than 2%. The measured permittivities in the 1-8-GHz range are used to estimate the sub-1-GHz permittivities of MUTs using extrapolation. The sensing system is also used for mixture characterization to find the mixing ratios in binary mixtures with an accuracy of 1%.

PLL-Based Microwave Chemical Sensor With 1.5% Permittivity Accuracy

A CMOS wideband dielectric spectroscopy system is proposed for chemical and biological material characterization. The complex permittivity detection is performed using a configurable harmonic-rejecting receiver capable of indirectly measuring the complex admittance of sensing capacitor exposed to the material-under-test (MUT) and subject to RF signal excitation with a frequency range of 0.62-10GHz. The sensing capacitor is embedded in a voltage divider topology with a fixed capacitor and the relative variations in the magnitude and phase of the voltages across the capacitors are used to find the real and imaginary parts of the permittivity. The sensor achieves an rms permittivity error of less than 1% over the entire operation bandwidth.

A 1–8-GHz Miniaturized Spectroscopy System for Permittivity Detection and Mixture Characterization of Organic Chemicals

In this paper, a miniaturized broadband dielectric spectroscopy system is presented for complex permittivity detection of organic chemicals in the 0.5-3-GHz frequency range. A sensing capacitor exposed to a material under test exhibits changes in its capacitance and resistance according to the complex permittivity. The sensing capacitor is embedded inside a wideband impedance divider circuit excited by an external microwave signal at the sensing frequency. The amplitude and phase variation of the microwave signal across the impedance divider is a function of the complex permittivity. Wideband in-phase and quadrautre mixers are used to measure the resulting amplitude and phase variations. A unique calibration algorithm using reference liquids is applied to the fabricated sensor and sensor characteristics are extracted using 2-D surface fitting. Complex permittivity detection of pure organic chemicals is performed with an error less than 1.5% in the 0.5-3-GHz frequency range. The measured points of the permittivity versus frequency are used to estimate the static permittivity using extrapolation with an error less than 1.5% compared to theoretical values. The sensor is also applied to measure the permittivities of binary mixtures with a mixing ratio accuracy of 1%.

A 0.62–10GHz CMOS dielectric spectroscopy system for chemical/biological material characterization

This paper presents a miniaturized broadband dielectric spectroscopy system for dielectric characterization and chemical sensing for 1-to-8 GHz frequency range. Sensor operation is based on detecting the phase shift of a signal passing through a true-time-delay (TTD) cell at the presence of an organic chemical. Cascaded TTD cells are used to improve the detection accuracy and the sensing bandwidth. Measurements with calibration show accurate detection of frequency-dependent permittivity for organic chemicals with permittivities up to 20.

Complex Permittivity Detection of Organic Chemicals and Mixtures Using a 0.5–3-GHz Miniaturized Spectroscopy System

A new wideband low noise amplifier (LNA) is proposed in this paper. The LNA utilizes a composite NMOS/PMOS cross-coupled transistor pair to increase the amplification while reducing the noise figure. The introduced approach provides partial cancellation of noise generated by the input transistors, hence, lowering the overall noise figure. An implemented prototype using IBM 90 nm CMOS technology shows a measured conversion gain of 20 dB across 2-1100 MHz frequency range, an IIP3 of -1.5 dBm at 100 MHz, and minimum and maximum noise figure of 1.43 dB and 1.9 dB from 100 MHz to 1.1 GHz. The LNA consumes 18 mW from 1.8 V supply and occupies an area of 0.06 mm2.