A Novel 1.5V CMFB CMOS Down-Conversion Mixer Design for IEEE 802.11a WLAN Systems

1. A Novel 1.5V CMFB CMOS Down-Conversion Mixer Design for IEEE 802.11a WLAN Systems Xuezhen Wang, Robert Weber, and Degang Chen Dept. of Electrical and Computer Engineering Iowa State University, U. S. A.

2. Outline • Introduction • Mixer circuit design • Simulation results • Conclusions

3. Introduction • The growing wireless LAN market has generated increasing interest in technologies that will enable higher data rates and capacity than initially deployed systems • The IEEE 802.11a standard provides nearly five times the data rate and as much as ten times the overall system capacity as currently available 802.11b wireless LAN systems

4. Introduction (cont. ) • Fast growth of personal communication market highly demands to produce low cost and low power transceivers for wireless applications • As a low cost alternative, CMOS is becoming a contender for RF front-end IC applications • In low-voltage RF IC design, high LO drives are difficult to generate

5. MOS version of Gilbert-type mixer • Cannot operate at near 1V supply due to the stack of the three saturated transistors • Designing a CMOS mixer that can operate at 5-6 GHz with low voltage becomes a challenging task

6. Cheng et al. designed a 1.2 V, 900 MHz CMOS mixer circuit using current mode multiplication method (ISCAS 02) However, the conversion gain is only -9 dB. Kathiresan et al. proposed a CMOS mixer core, operating at 1GHz, where the RF signal is input via the bulk (ISCAS 99) But their conversion gain is only 2.09 dB State-of-the-art research

7. Motivation and goal • Due to the limitations of the existing research work, Wang et al. proposed a low-voltage 5.8 GHz mixer design in a TSMC 0.18 µm CMOS process (RAWCON 03) • This paper is a further improvement of the design in RAWCON 03

8. Complete schematic of the 5.8GHz mixer with common mode feedback structure

9. Features of the new design • PMOS transistors M1 and M2 are used for the RF input stage to convert the RF input voltage to current, which is coupled to the core of Gilbert Cell using current mirror (transistors M9-M10 and M11-M12) • This implementation eliminates the current source transistor at bottom and furthermore reduces the supply voltage • The proposed design has common-mode feedback (CMFB) structure

10. Advantages: Guarantee that there is only Vds voltage drop from Vdd, which make the circuit work at a low voltage condition and also enlarges the output swing at the same time Disadvantages: Increase the power dissipation compared to the design in RAWCON 03 May suffer from large flick noise Common-mode feedback (CMFB) structure tradeoffs

11. Conversion gain of the mixer

12. Noise figure of the mixer

13. IIP3 of the mixer

14. S11 of the Mixer

15. S22 of the Mixer

16. Performance summary of mixer

17. Conclusions • This paper has described a low-voltage 5.8 GHz mixer design integrated in a TSMC 0.18 um CMOS process • The proposed method features that an RF input stage converts the RF input voltage to current, which is coupled to the core of Gilbert Cell using current mirror • Common-mode feedback is used for the active load of the mixer • This mixer can be used for low voltage and low power wireless applications