A receiver with in-band IIP3>20dBm, exploiting cancelling of OpAmp finite-gain-induced distortion via negative conductance

Highly linear CMOS radio receivers increasingly exploit linear RF V-I conversion and passive down-mixing, followed by an OpAmp based Transimpedance Amplifier at baseband. Due to the finite OpAmp gain in wideband receivers operating with large signals, virtual ground is imperfect, inducing distortion currents. We propose to apply a negative conductance to cancel this distortion. In an RF receiver, this increases In-Band IIP3 from 9dBm to >20dBm, at the cost of 1.5dB extra NF and <10% power penalty. In 1MHz bandwidth, a Spurious-Free Dynamic Range of 85dB is achieved at <27mA up to 2GHz for 1.2V supply voltage

Cancellation of OpAmp virtual ground imperfections by a negative conductance applied to improve RF receiver linearity

High linearity CMOS radio receivers often exploit linear V-I conversion at RF, followed by passive down-mixing and an OpAmp-based Transimpedance Amplifier at baseband. Due to nonlinearity and finite gain in the OpAmp, virtual ground is imperfect, inducing distortion currents. This paper proposes a negative conductance concept to cancel such distortion currents. Through a simple intuitive analysis, the basic operation of the technique is explained. By mathematical analysis the optimum negative conductance value is derived and related to feedback theory. In- and out-of-band linearity, stability and Noise Figure are also analyzed. The technique is applied to linearize an RF receiver, and a prototype is implemented in 65 nm technology. Measurement results show an increase of in-band IIP3 from 9dBm to >20dBm, and IIP2 from 51 to 61dBm, at the cost of increasing the noise figure from 6 to 7.5dB and <10% power penalty. In 1MHz bandwidth, a Spurious-Free Dynamic Range of 85dB is achieved at <27mA up to 2GHz for 1.2V supply voltage

A CMOS spectrum analyzer frontend for cognitive radio achieving +25dBm IIP3 and −169 dBm/Hz DANL

A dual RF-receiver preceded by discrete-step attenuators is implemented in 65nm CMOS and operates from 0.3– 1.0 GHz. The noise of the receivers is reduced by cross-correlating the two receiver outputs in the digital baseband, allowing attenuation of the RF input signal to increase linearity. With this technique a displayed average noise level below -169 dBm/Hz is obtained with +25 dBm IIP3, giving a spurious-free dynamic range of 89 dB in 1 MHz resolution bandwidth

The Use of Sound as Context on Wearable Devices

In this paper we will describe an experiment held to investigate the influence of different types of sound support used as context in an environment where users are not able to pay (enough) visual attention to their device. Both auditory icons and spoken text were tested against a reference group which had no sound to support them. In spite of the low number of participants it seems very likely auditory icons are a great improvement used as context. Spoken text however did not give any difference compared to the reference group

Densely Interleaved Arrays for Dual-Tone Transmitters

Power amplifier nonlinearity introduces intermodulation distortion when transmitting dual-tone signals from an antenna array. To reduce distortion levels and increase output power for dual-tone systems we propose to densely interleave two antenna arrays without increasing the antenna aperture. Each array is excited with a different tone, resulting in a single-tone input for the power amplifiers, thereby reducing intermodulation distortion. In order to compare the performance of the densely interleaved array with a regular, planar array, when excited by two-tone signals, a procedure for evaluating the S-parameters matrix of an interleaved dipole array is presented. Simulations with a realistic RF power amplifier model show 13 to 31 dB intermodulation reduction for the same output power and total antenna aperture

Datos para la flora liquenica de CataluÑa. Liquenes epifilos

Se citan los táxones encontrados sobre hojas de Buxus sempervirens, haciendo un intento de clasificación según los trabajos de SANTESSON, 1952 y SERUSIAUX, 1977; a I d vez proponemos una relación-clasificación de los términos: epífito, foliícola, corticlcola y muscícola

Reverse Intermodulation in Multi-Tone Array Transmitters

The modern spectral, and thereby linearity, requirements force 5G phased-array transmitter systems to operate at reduced power efficiency, as they can no longer use voluminous filtering. To reduce the linearity requirements of the transmitter, we consider the case of an array consisting of closely spaced radiating elements operating at different frequencies. The coupled tones from one element to another create reverse intermodulation distortion (RIMD). We explain how RIMD is created within a power amplifier (PA), and derive an estimate for the power of the RIMD components. We provide a set of measurements for an X-Band GaAs PA and draw a direct comparison between RIMD and IMD. We show that RIMD has a third-order behaviour up to very high reverse power levels, opening up the perspective for higher output power operation as well as simpler and lower-power predistortion in multi-tone array systems such as 5G and rada

Digital-to-Frequency Converters with a DTC: Theoretical Analysis of the Output SFDR

In this paper, we propose and analyze a pulse-output digital-to-frequency converter (DFC) generating square waves, which uses a digital-to-time converter (DTC) to correct the spurious tones (spurs) in the output spectrum. We focus on high-level architectural potential, discuss the design features of a DTC suitable for the proposed system, and explore possibilities and limits of this approach in terms of cleanness of the output spectrum. The behavioral model simulations confirm the theoretical analysis presented. Besides an analytical description of the output spurs, we derive a closed-form estimate of the worst-case spur, which leads to a simple design equation. This is useful to determine the DTC requirements [number of bits and integral non-linearity (INL)], given a certain spurious-free dynamic range (SFDR) target. We show that the maximum spur strength (in dBc) depends exclusively on the ratio between the output frequency and the clock frequency and the DTC features (number of bits, INL, and other impairments) and increases with the ratio by 6 dB/octave