Dusan Milosevic

Explicit design equations for class-E power amplifiers with small DC-feed inductance

This paper presents novel, explicit design equations for class-E power amplifiers with finite DC-feed inductance. A mathematically exact analysis of the idealized class-E power amplifier with small DC-feed inductance shows that the circuit element values are transcendent functions of the input parameters. Therefore, the designer needs to perform a long iterative procedure in order to find these values. We have solved the circuit operation for a certain number of cases, and performed a Lagrange polynomial interpolation in order to obtain explicit, directly usable design equations. The proposed design method is verified by simulation and the agreement with the theory is excellent.

Co-Integration of an RF Energy Harvester Into a 2.4 GHz Transceiver

This paper presents an RF energy harvester embedded in a low-power transceiver (TRX) front-end. Both the harvester and the TRX use the same antenna and operate at the same frequency of 2.4 GHz. To decouple the harvester from the TRX, different concepts are proposed regarding the transmitter (TX) and receiver (RX). To avoid loading the TX, the harvester is decoupled with an nMOS switch that can be enabled with a start-up rectifier. Concerning the RX, the decoupling mechanism relies on the nonlinear input impedance of the main RF-DC converter. The harvester also includes a supply management circuit for over-voltage protection and charging energy storage devices with a constant current or voltage. The energy harvester has been co-integrated with the low power TRX in a 130 nm CMOS process and achieves a measured peak power conversion efficiency of 15.9%. For input power levels of at least -9 dBm, it is able to charge up a supply capacitor to a regulated voltage of 1.34 V. The impact of the harvester on the TRX performance is measured with respect to an identical TRX front-end without harvester, showing little impact on the TRX performance. Both TX output power and RX noise figure are degraded by less than 0.5 dB. As an additional feature, the start-up rectifier is also used for demodulation of On-Off-Keying (OOK) signaling, which can be used as a secondary wake-up channel. Since the required area for the harvester is only 0.019 mm2 (≈ 2% of the total active TRX area), it can be added to the TRX at almost no cost.

Ultra-low power FSK Wake-up Receiver front-end for body area networks

In this paper, we present an ultra low-power Wake-up Receiver front-end operating in the 868/915MHz ISM band. It targets short distance body area networks. Its power consumption is only 126uW, including a low-power on-chip ring oscillator. Since the receiver targets small transmission distances, up to 10m, sensitivity is traded against power consumption. This is achieved by removing the LNA and making all the gain at the low IF frequencies. The receiver sensitivity is −65dBm at a BER of 0.1%.

Analytical Models for the Wake-Up Receiver Power Budget for Wireless Sensor Networks

In this paper analytical models of the energy consumption are presented which uses a real world radio model with two different low power modes. This model is used to compare energy consumption of different MAC protocols. The MAC protocols used for the comparison are chosen with sensor networks is mind. The energy consumption of the nodes in a sensor network needs to be minimized to maximize the lifetime of the network. Emphasis is placed on MAC protocols, since they have a big influence on the energy consumption. One of the MAC protocols uses a low power Wake Up Receiver (WURx) which is used to decrease the total energy dissipation. The WURx MAC protocol is compared with two other low power MAC protocols, namely the asynchronous X-MAC and synchronous TDMA protocol. The obtained model is used to derive the WURx power budget. The response time of the nodes is used as the main design requirement and the important application parameters are given that determine the WURx power budget.

A 3µW fully-differential RF envelope detector for ultra-low power receivers

A fully differential envelope detector (ED) operating at 2.4GHz is designed in 90nm CMOS technology. The new design uses the common-gate topology to deal with large common-mode input signals through first-order current cancellation. Thereby, a fully differential ultra-low power super-regenerative front-end is enabled. It has a measured output voltage swing of 2.8–127mV and achieves 19.6dB output SNR at sensitivity input level. The circuit consumes 3µW from a 1.2V power supply.

On the feasibility of application of class E RF power amplifiers in UMTS

This paper investigates the feasibility of the application of class E RF power amplifiers in UMTS. A typical class E circuit has been designed and simulated, in conjunction with a linearization scheme based on the EER principle. The EER testbench uses ideal building blocks, since the emphasis is on the operation of the amplifier itself. Three different technologies have been used for the active device (Si BJT, GaAs HBT and CMOS) in order to examine the influence of the device technology on the PA performance. Relevant parameters have been monitored and put in the table form, for comparison of technologies. The simulation results indicate that class E PAs can successfully be used for power amplification of WCDMA RF signal and that GaAs technology is offering the highest efficiency.

A 71GHz RF energy harvesting tag with 8% efficiency for wireless temperature sensors in 65nm CMOS

This paper presents the first monolithically integrated RF-power harvesting 71 GHz wireless temperature sensor node in 65nm CMOS technology, containing a monopole antenna, a 71 GHz RF power harvesting unit with storage capacitor array, an End-of-Burst monitor, a temperature sensor and an ultra-low-power transmitter at 79 GHz. At 71 GHz, the RF to DC converter achieves a power conversion efficiency of 8% for 5 dBm input power.

Wireless wire-the 60 GHz ultra-low power radio system

This article presents basic issues regarding design and development of a 60 GHz ultra-low power radio system for Ambient Intelligence (AmI) applications. It demonstrates the validity of choosing the 60 GHz frequency band to design low power radios by a mathematical model, and proposes an overview of a cross-layer optimization flow to minimize power dissipation. Moreover, a completed RF front-end architecture, i.e. the transmitter and the receiver, is simulated according to the proposed methodology. Crucial concerns, challenges and solutions are discussed based on it. Simulation results are given, which verify the theoretical conclusions of 120 pJ/bit power consumption.

A 62 GHz inductor-peaked rectifier with 7% efficiency

This paper presents the first 62 GHz fully onchip RF-DC rectifier in 65nm CMOS technology. The rectifier is the bottleneck in realizing on-chip wireless power receivers. In this paper, efficiency problems of the mm-wave rectifier are discussed and the inductor-peaked rectifier structure is proposed and realized. By using an inductor-peaked diode connected transistor, self-threshold voltage modulation, and an output filter, the measured rectifier reaches 7% efficiency with 1 mA current load. Compared to previous state-of-art 45 GHz rectifier with 1.2% efficiency [1], our solution achieves a higher efficiency at a higher frequency, providing a better solution for mm-wave wireless power receivers.

Requirement driven low-power LC and ring oscillator design

Receiver power consumption should be kept as low as possible in applications such as sensor networks. Zero-IF detection is preferred over the interferer-sensitive and modulation-restricted envelope-detection receiver. However, a disadvantage of the zero-IF topology is that it requires a power consuming oscillator. Therefore, minimal-power oscillator design is desired. This paper shows that the ring type of oscillator becomes more power efficient than the LC type when the maximal tolerated phase noise increases. Which is due to required impedance levels and thus related to technological limitations. This conclusion is contradictory to what is usually assumed, based on fundamental reasoning.