Reconfigurable Ultra Low Power LNA for 2.4GHz Wireless Sensor Networks

1. Reconfigurable Ultra Low Power LNA for 2.4GHz Wireless Sensor Networks TarisT., Mabrouki A., Kraïmia H., Deval Y., Begueret J-B. Bordeaux, France

2. OUTLINE • Context • RF Front End Specifications • Circuit design • Conclusion & Perspectives

3. OUTLINE • Context • RF Front End Specifications • Circuit design • Conclusion & Perspectives

4. Context MicroElectronicMilestones • Computers in the seventies • Low cost Si technologies • Digital processing • The Cellular phone in the 90’s • Telecommunication network • RF circuits and systems • Wireless Sensor Network & RFID in the early 21th century • Gate reduction • Energy (scavenging, management…)

5. Context Wireless Sensor Network Configuration • Reduce the node power consumption… Wireless Sensor Network B A RF link 1 C RF link 2 …by matching the RF link budget to the communication scenario

6. OUTLINE • Context • RF Front End Specifications • Circuit design • Conclusion & Perspectives

7. RF Front End Specifications Node Top-down • Node at system level Memory RF Link Budget 2 µController ADC Sensor RF Tx/Rx • Node Rx at system level RF Link Budget 1 NFRx2 Power unit PRx RFFE Demodulator NFRx1 SNRdem NFRx = PRx - SNRdem+(174-10 log BW)

8. RF Front End Specifications RF Link Parameters BFSK modulation Channel Characteristic Attenuation L(R) PTx PRx BER~10-3 distance R node B node A SNRdem~10 dB BW = 10MHz NFRx= PRx– SNRdem+ (174-10 log BW) PRx = PTx - Lpath(R) 2.4 GHz ISM Band

9. RF Front End Specifications RFFE and NF specification • Node Rx at system level NFRx2 PRx RFFE Demodulator NFRx1 SNRdem • RFFE and system specification Mixer LNA NFRx2 LO NFRx1 NFRxismainlysupported by the LNA !

10. RF Front End Specifications RFFE and NF specification • Node Rx at system level NFRx2 PRx RFFE Demodulator NFRx1 SNRdem • RFFE and system specification Mixer LNA NFRx2 LO NFRx1 NFRxismainlysupported by the LNA !

11. OUTLINE • Context • RF Front End Specifications • Circuit design • Conclusion & Perspectives

12. Circuit Design Low Power RF Metric Optimized biasing! • Optimization of RF performances versus power consumption in the transistor… RF skills Current consumption …by maximizing the FOMLP Vth ~ Vth+ 100mV

13. Circuit Design Amplifier Configurations • To compensate for the low gm in MI region… Id Id Id MP MP MP bias OR ? RF RF RF out in out out MN MN MN in in Single Transistor Stage (STS) Self Biased Inverter (SBI) …active load configurations are preferred!

14. Circuit Design Amplifier Configuration • Comparison of the Gain BandWidth (GBW) product… 30 Self Biased Inverter (SBI) 20 Gain (dB) 10 Single Transistor Stage (STS) Frequency (Hz) 0 100G 1G 10G GBWSTS …the one of self biased inverter is the largest ! GBWSBI

15. Circuit Design LNA topology LNA 2.4GHz – CMOS 0.13µm 0.8V VDD Digital Control 3 VCC DAC Id Cdec Lpk 50 @ 2.4GHz Off-chip M2 Cm2 Rin/buffer RF out 50 @ 2.4GHz M3 Cm3 Lg Cl Cm1 in M1 Rpol2 Rpol1 Vpol2 Vpol1 Currentreuse with feedback buffer LNA core

16. Circuit Design Post Layout Performances S21 NF 900µm S11 700µm

17. OUTLINE • Context • RF Front End Specifications • Circuit design • Conclusion & Perspectives

18. Conclusion & Perspectives System Considerations • Match the radio performances with the RF link budget to reduce the power consumption of nodes in WSN • A matter of Noise Figure/Gain reconfiguration in the LNA Requirement Circuit analysis • Best tradeoff between RF skills and current consumption in MI region • Select the topology providing the largest GBW Good agreement

19. Conclusion & Perspectives Done Next step NFRx2 NFRx1 Last step • A mixer to be designed in MI region • Gilbert Cell with current bleeding topology Mixer LNA LO • A VCO with low power techniques • Negative resistance topology

20. Thank you for your Attention