A Low-Pass Filter with Automatic Frequency Tuning for a Bluetooth Receiver

1. M. Pedro1, J. Galán1, T. Sánchez-Rodríguez1, F. Muñoz2, R. G. Carvajal2 and A. López-Martín3 1 Dpto. de Ingeniería Electrónica, de Sistemas Informáticos y Automática,University of Huelva, Spain 2 Dpto. de Ingeniería Electrónica, Escuela Superior de Ingenieros de Sevilla, University of Sevilla, Spain 2 Dpto. de Ingeniería Eléctrica y Electrónica, PublicUniversity of Navarra, Spaintrinidad.sanchez@gie.esi.us.es A Low-Pass Filter with Automatic Frequency Tuning for a Bluetooth Receiver

2. Outline System overview Filter architecture Transconductor Topology Transconductor Simulation Results Frequency Tuning Circuit Filter Simulation Results Conclusions

3. 1. System Overview • Short range • Low power • Low cost • Available in almost any mobile phone • Supports voice and data • Uses an unregulated frequency BLUETOOTH System Overview Filter Architecture Transconductor Topology OTA Simulation Results Frequency Tuning Circuit Filter Post-Layout Simulation Results Conclusions

4. 1. System Overview Zero-IF Bluetooth Receiver Filterunderdesign System Overview Filter Architecture Transconductor Topology OTA Simulation Results Frequency Tuning Circuit Filter Post-Layout Simulation Results Conclusions

5. 2. Filter Architecture FilterSpecifications System Overview Filter Architecture Transconductor Topology OTA Simulation Results Frequency Tuning Circuit Filter Post-Layout Simulation Results Conclusions

6. 2. Filter Architecture SelectedArchitecture Gm-C implementation System Overview Filter Architecture Transconductor Topology OTA Simulation Results Frequency Tuning Circuit Filter Post-Layout Simulation Results Conclusions

7. 3. Transconductor Topology • Linearity is highly dependant on VDS of M1-M2 • Regulated-cascode transistors must ensure that M1,2 drain voltage remains practically constant despite large input current variations System Overview Filter Architecture Transconductor Topology OTA Simulation Results Frequency Tuning Circuit Filter Post-Layout Simulation Results Conclusions

8. 3. Transconductor Topology • M1 and M2 are in triode region System Overview Filter Architecture Transconductor Topology OTA Simulation Results Frequency Tuning Circuit Filter Post-Layout Simulation Results Conclusions

9. 3. Transconductor Topology • M3 and M4 are used to fix the drain voltage of M1 and M2 System Overview Filter Architecture Transconductor Topology OTA Simulation Results Frequency Tuning Circuit Filter Post-Layout Simulation Results Conclusions

10. 3. Transconductor Topology • M5-M6 and M8-M6 formed a feedback loop System Overview Filter Architecture Transconductor Topology OTA Simulation Results Frequency Tuning Circuit Filter Post-Layout Simulation Results Conclusions

11. 3. Transconductor Topology • M6-M7 implement a very low impedance node System Overview Filter Architecture Transconductor Topology OTA Simulation Results Frequency Tuning Circuit Filter Post-Layout Simulation Results Conclusions

12. 4. Transconductor Simulation Results Transconductor ProgramabilityRange • Gm from 15 to 165 uA/V System Overview Filter Architecture Transconductor Topology OTA Simulation Results Frequency Tuning Circuit Filter Post-Layout Simulation Results Conclusions

13. 5. Frequency Tuning Circuit PHASE Ф1 PHASE Ф2 PHASE Ф3 Charge transfer happens between C1, C2 and C3. Capacitor C1 is reset It is used to eliminate the possible ripple of the tuning voltage System Overview Filter Architecture Transconductor Topology OTA Simulation Results Frequency Tuning Circuit Filter Post-Layout Simulation Results Conclusions

14. 5. Frequency Tuning Circuit In quiescent conditions System Overview Filter Architecture Transconductor Topology OTA Simulation Results Frequency Tuning Circuit Filter Post-Layout Simulation Results Conclusions

15. 6. Filter Post-Layout Simulation Results Layout System Overview Filter Architecture Transconductor Topology OTA Simulation Results Frequency Tuning Circuit Filter Post-Layout Simulation Results Conclusions

16. 6. Filter Post-Layout Simulation Results System Overview Filter Architecture Transconductor Topology OTA Simulation Results Frequency Tuning Circuit Filter Post-Layout Simulation Results Conclusions

17. 6. Filter Post-Layout Simulation Results System Overview Filter Architecture Transconductor Topology OTA Simulation Results Frequency Tuning Circuit Filter Post-Layout Simulation Results Conclusions

18. 7. Conclusions • A Gm-C filter for a zero-IF Bluetooth receiver has been presented. • The transconductor used in the filter is a pseudo-differential one suitable for low voltage operation and with good performances regarding linearity and consumption. • An automatic frequency tuning circuit has been also used with the filter in order to overcome process variations. • The filter has been designed in a 0.5 µm CMOS technology, laid out and sent to fabrication. • Some simulations results of the filter have been provided. System Overview Filter Architecture Transconductor Topology OTA Simulation Results Frequency Tuning Circuit Filter Post-Layout Simulation Results Conclusions

19. Thank you very much for your attention