RF Design Magazine


Multimode RF transceiver advances WEDGE radio system
Jan 1, 2007 12:00 PM  By James A. Crawford

Wireless communications are evolving at an ever-increasing rate. Systems such as GSM, EDGE and CDMA are being augmented with 3G and Wi-Fi capabilities, making an efficient and cost-effective multimode solution essential. The RF transceiver is a key ingredient of any multimode solution. Its design presents several challenges that are magnified when distinctly different modes such as GSM and WCDMA must be hosted.

Integrated GSM-EDGE-WCDMA solution

A high-level block diagram of Sequoia's SEQ7400 GSM-EDGE-WCDMA tri-band solution is shown in Figure 8. It uses direct-conversion for receive with integrated filtering at RF thereby easing board-level integration issues substantially. No SAW filters between the LNA and mixer are required, and all GSM-EDGE-WCDMA LNAs are fully integrated on chip. The transmitter is based on Sequoia's patented FullSpectra common architecture that addresses all of the key issues discussed earlier. It eliminates many of the redundancies commonly found in other transceiver solutions that use separate transmit paths for WCDMA and GSM-EDGE. The high level of integration eases PCB integration with its concomitant low parts count while also reducing the cost of the overall solution.

References

  1. Crawford, J.A., Frequency Synthesizer Design Handbook, Norwood, MA: Artech House, 1994.

  2. “Advanced Manpack Radio Concept for UHF DAMA Satellite Communications,” SBIR Phase I Final Technical Report Topic AF91-030, Contract No. F19628-91-C-0154, http://www.am1.us/Papers/U11585%20AF91%20Main.pdf.

  3. Razavi, B., “A Study of Phase Noise in CMOS Oscillators,” IEEE J. Solid-State Circuits, March 1996.

  4. Hung, C., R. Bogdan, et al., “A Digitally Controlled Oscillator System for SAW-Less Transmitters in Cellular Handsets,” IEEE J. Solid-State Circuits, May 2006.

  5. Rabaey, J.M., Digital Integrated Circuits, Upper Saddle River, NJ: Prentice-Hall, 1996.

ABOUT THE AUTHOR

James A. Crawford is a senior fellow at Sequoia Communications in San Diego, CA. He is the author of Frequency Synthesizer Design Handbook (1994). He has contributed to 15 issued U.S. patents plus additional filings in areas ranging from frequency synthesis to baseband modem algorithms and high-density non-volatile data storage techniques. He co-founded Magis Networks in 1999 as its vice president of engineering and later served as its CTO. Prior to 1999, he held senior staff positions at Hughes Aircraft Co., TRW, and Linkabit, and also had his own consulting firm through much of the 1990s. He holds an MSEE in quantum electronics from USC.

Table 1. VCO LC resonator suppression of harmonic and subharmonic contaminations.
Harmonic / subharmonic Q=5
dB		 Q=10
dB		 Q=20
dB
2 17.6 23.5 29.5
3 22.5 28.5 34.5
4 25.5 31.5 37.5
1/2 17.6 23.5 29.5
1/3 22.5 28.5 34.5
1/4 25.5 31.5 37.5

Previous 1 2 3 4 5



June 2011 Military Defense Electronics Supplement
 
Back to Top