CX74017

On the Direct Conversion Receiver

8

Skyworks Solutions, Inc., Proprietary and Confidential

101735A

Preliminary Data Subject to Change

July 20, 2001

Figure 14 and Figure 15 sketch how this affects a given

constellation diagram. In DCR systems however, the IQ

matching is not as critical as in image-rejection architectures.

Rather, it is only important insofar as the accuracy of the

modulation is concerned.

Analog and digital (DSP based) calibration and adaptation

methods have been described so as to correct for these

imbalances, for example in [15].

101735A 14_071801

I

Q

gain

imbalance

ideal

constellation

Figure 14. IQ Demodulator Imperfections (Gain Imbalance)

101735A 15_071801

I

Q

phase

imbalance

Figure 15. IQ Demodulator Imperfections (Phase Imbalance)

Conclusion

The direct conversion receiver is an attractive yet challenging

receiving technique. It has recently been applied successfully to

devices such as pagers, mobile phones, PC and internet

wireless connectivity cards, satellite receivers etc. in a variety of

process technologies and increasing integration levels. It is

poised to appear in many more applications in the near future.

References

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L. Lessing, “Man of High Fidelity: Edwin Howard

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[2]

F.M. Colebrook, “Homodyne”, Wireless World and Radio

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[3]

D.G. Tucker, “The Synchrodyne”, Electronic Engng, 19, p.

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[4]

D.G. Tucker, “The History of the Homodyne and the

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[5]

A.A. Abidi, “Direct-Conversion Radio transceivers for

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[6]

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[7]

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[8]

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[9]

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[12] D.K. Weaver, “A Third Method of Generation and

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[15] J.K. Cavers, M. W. Liao, “Adaptive Compensation for

Imbalance and Offset Losses in Direct Conversion

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Technology, vol. 42, p. 581-588, November 1993.