Highly sensitive CMOS passive wake-up circuit

The design of a ultra-low power RF wakeup sensor for wireless sensor networks

“…I. INTRODUCTION Idle listening, which is the state of monitoring communication media to check potential traffic, is the dominant source of energy consumption in WSNs. Duty cycling, which makes nodes periodically turn off their RF communication module, can effectively reduce the energy consumptionduetoidlelistening.Butitintroducessleepdelay due to the sleep state of a receiver. High duty cycle reduces sleep delay but increases energy consumption due to more frequent wakeups while low duty cycle reduces energy consumptionbutincreasessleepdelayduetoalongsleepstate. Todealwiththistradeoffbetweentheenergyconsumptionand the sleep delay, the existing WSN studies focuses on MAC protocols to support energy efficient yet high performance communications. To mitigate the impact of sleep delay on packet latency, many MAC protocols exploit dynamic duty cycling [1,2,3]orwakeupscheduling [4,5,6]. However, these optimizations are not a fundamental solution for eliminating idle listening since they still require dutycycling.Afewstudies [7,8]haveinvestigatedthedesign of a radio wave sensor, which is a dedicated RF module to checkforpotentialcommunications.Sincearadiowavesensor doesn'tdecodeanincomingsignal,itrequiresonlyasubsetof components from the RF communication module. Therefore, mostoftheconventionalradiowavesensorsareimplemented withoutamplifiers that consume heavy energy. However, it is hard to detect a signal weaker than the minimum signal strengthrequiredforpassingthroughasilicondiode.Therefore, Therefore,RFsensingrangesoftheexistingschemesaremuch shorterthanRFcommunicationranges [7,8]. Toprovidearadiowavesensorwiththesamesensitivityas theunderlyingRFcommunicationmodule,wepropose anew design of radio wave sensor called RF wakeup sensor. To equalize RF sensing range to communication range, the RF wakeup sensor uses a dedicated amplifier for input signal. Since the RF wakeup sensor does not have to extract information from a received signal, the amplifier in the RF wakeupsensorisindifferenttophasedistortion.Therefore,we can simplify conventional amplifier that consist of complex circuitsforprovidinghighlinearity.Consequently,weareable to design an ultralow power amplifier with the minimum circuitelements. If the RF wakeup sensor has no frequency filtering technique, the number of falsepositive wakeups due to unrelated signals willbe increased. Forthis purpose we use a frequency filter that requires neither mixer nor oscillator to selectively sense signal on the predefined frequency band. Since the frequency used for a communication is higher than intermediate frequency, RF wakeup sensor requires a precise frequencyfilterwithhighqualityfactor(Qfactor). The rest of this paper is organized as follows. Section 2 discusses the related works. Section 3 presents our design procedures and methodologies used for RF wakeup sensor design. Section 4 analyzes the detailed simulation results for theproposedRFwakeupsensor.And,Section5concludesthe paper. II. RELATEDWORK There have been a few studies [7, 8] for a radio wave sensor. However, it is hard to apply the existing radio wave sensorstowirelesssensornodessincethesensorsdesignedso far have shortcomings: additional wakeup channel and insufficient sensitivity. PRFW …”

“…AccordingtotheEq.(2),a69dBmdifferenceinsensitivity implies a range difference of 3000 times. While CC1000 can transmit a packet over 150 meters, the maximum distance of HWC [8]isonly5cmaccordingtotheFriisequation.…”