ETTC'2003 - SEE
ETTC'2003 - SEE ETTC'2003 - SEE
Photo-oscillator active device Optical power at the end of the fiber Oscillator dynamic synchronization bandwidth Free running oscillator phase noise at 100 kHz InP HEMT 8 dBm 20 kHz -108 dBc/Hz InP Photo-HBT -2 dBm 80 kHz -105 dBc/Hz InGaAs Photodiode + SiGe HBT oscillator -2 dBm 80 kHz -127 dBc/Hz Table 2 Synchronization bandwidth of the 3.5 GHz optically synchronized oscillators, and phase noise of the free running oscillator at 100 kHz offset. The amplitude modulation factor of the optical signal is about 0.25. Phase Noise (dBc/Hz) 20 0 -20 -40 -60 -80 -100 -120 -140 Residual phase noise of the optical link Free running oscillator -160 1 10 100 1000 10000 100000 Frequency (Hz) Optical transmission of a synthesized signal (Anristu 69147A) Figure 3 Phase noise of a 3.5 GHz optical link realized with a photo-diode + an SiGe HBT synchronized oscillator, and featuring 10 dB optical losses. Three different spectra are plotted : 1) free running oscillator phase noise 2) residual phase noise of the optical link 3) transmitted spectrum of an Anritsu synthesizer Concerning the phase noise, the optical power does not too much modify the phase noise of the free running oscillators, even if a strong change is observed on the DC current. The best results far from the carrier are obtained with the photodiode + SiGe HBT oscillator configuration, because of the low 1/f noise properties of the SiGe device. However, at higher frequencies (millimeter wave range) the silicon devices may be difficult to use and the compacity of the photo-HBT approach is particularly interesting. VI. CONCLUSION Different RF and microwave optical links using optically synchronized oscillators as receivers have been presented. The advantage of this approach for the transmission of pure sinusoidal signals (reference signals) is clearly underlined. At 10 MHz, a strong improvement of the optical link phase noise has been obtained. At higher frequencies, the improvement is much based on the filtering of the signal far from the carrier and on the constant output power imposed by the oscillator. At microwave frequencies, the photodiode has been replaced successively by two different types of light sensitive devices. Good results have been obtained with the photo- HBT approach, while the illumination of the gate region of an InP HEMT device has been found to be less efficient. ACKNOWLEDGEMENT This work has been partly supported by the French National Space Agency (CNES). REFERENCES [1] A. S. DARYOUSH, « Optical synchronization of millimetre-wave oscillators for distributed architectures» IEEE trans. on MTT, vol 38, n° 5, mai 1990, pp. 467-476. [2] R. D. ESMAN, L. GOLDBERG, J. F. WELLER, “Optical phase control of an optically injection locked FET microwave oscillator” IEEE trans. on MTT, vol 37, n° 10, oct. 1989, pp. 1512-1518. [3] M. MULLER, M. RIET, C. FORTIN, S. WITHITSOONTHORN, J. D’ORGEVAL and C. GONZALEZ, “Millimeter –wave InP/InGaAs photo- HBT and its application to a double stage cascode optoelectronic mixer”, 2002 Int. Topical Meeting on Microwave Photonics, MWP 2002 Digest pp. 345-348. [4] T. PARENTY, S. BOLLAERT, J. MATEOS, X. WALLART, A. CAPPY, "Design and realization of sub-100nm gate length HEMTs" Indium Phosphide and Related Material (IPRM), Nara Japan, pp. 626-629, may 2001. [5] A. J. SEEDS, “Microwave Photonics”, IEEE trans on MTT, vol 50, n° 3, march 2002, pp. 877-887. [6] G. P. AGRAWAL, “Fiber optic communication systems”, Wiley Edition, 1997. [7] R. ADLER, “A study of locking phenomena in oscillator”, Proc. IRE, vol. 34, n° 6, june 1946, pp. 351-357. [8] K. KUROKAWA, “Noise in synchronised oscillators” , IEEE Trans. on Microwave Theory and Tech., vol 16, n° 4, avril 1968, pp. 234-240. [9] M.B. BIBEY, F. DEBORGIES, M. KRAKOWSKI, D. MONGARDIEN “Very low phase noise optical links - experiments and theory” IEEE trans. on Microwave Theory and Tech., vol 47, n° 12, dec. 1999. [10] H. FURUTA et al., « Optical injection locking of a 38 GHz Band InP Based HEMT oscillator using a 1.55 µm DSB- SC modulated lightwave » IEEE Microwave and Wireless Components Letters, vol 11, n° 01, Jan. 2001, pp. 19-21.
BACK Quasi-synchronous multiuser detection technique used in telemetry System Jin shubo Electronics Engineering Institute of China Academy of Engineering Physics. P.O Box 919-517 Mianyan,Sichuan 621900,P.R.China, E-mail: jsb_caep@21cn.com. Abstract: The performance of a DS/CDMA system degrades due to Multiple Access Interference (MAI), when the asynchronous multiuser detection technique is used to remove the MAI, its matrix order is larger than the number of users, resulting in larger computational intensive. In some specific asynchronous DS/CDMA system, the quasi-synchronous multiuser detection algorithm, whose matrix order is equal to the number of users, needn’t estimate MAI power levels, thereby resulting in lower computational complexity and high “near-far” resistance. In this paper the performance of quasi-synchronous multiuser detection algorithm is analysized theoretically, and the numerical results are presented. Keywords: Quasi-synchronous, Multiuser Detection, DS/CDMA, MAI, Telemetry System. 1. Introduction DS/CDMA system is used in many communication systems because it has the capability of anti-jamming. Some results indicate that the CDMA system has larger system capacity than the TDMA system, but this result is based the hypothesis that the PN sequences are orthogonal with each other. If the DS/CDMA receiver use traditional single-user detector ( correlator or matched filter), the performance of a DS/CDMA system degrades due to Multiple Access Interference (MAI). In order to increase the system capacity of DS/CDMA system, Some researchers proposed the use of smart antenna or the power control in the DS/CDMA system to abate the effect of MAI, Others resort to the suboptimal multiuser detection such as linear decorrelation, successive interference cancellation and parallel interference cancellation. Most communication systems are asynchronous system. The DS/CDMA system in some telemetry System is a special asynchronous system. It has following specialties: 1) the mobile users have the inner timer, 2) the distance from the mobile users to base station are almost equal, 3) the mobile users in the system are fixedness, 4) the system work in simplex system. Considering these specialty and based the theory of synchronous decorrelation multiuser detection, Quasi-synchronous multiuser detection was used in the system to reduce the computation complexity. This paper analysis the performance of the quasi-synchronous multiuser detector theoretically, and compare with the synchronous decorrelation multiuser detection and the conventional detection. The numerical results are present. 2. Quasi-synchronous DS/CDMA system S.Verdu proposed the optimal multiuser detector that is too complex for practical implementation. R.Lupas put forward the decorrelation multiuser detection, for synchronous case,
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BACK<br />
Quasi-synchronous multiuser detection technique<br />
used in telemetry System<br />
Jin shubo<br />
Electronics Engineering Institute of China Academy of Engineering Physics.<br />
P.O Box 919-517 Mianyan,Sichuan 621900,P.R.China, E-mail: jsb_caep@21cn.com.<br />
Abstract: The performance of a DS/CDMA system degrades due to Multiple Access Interference<br />
(MAI), when the asynchronous multiuser detection technique is used to remove the MAI, its<br />
matrix order is larger than the number of users, resulting in larger computational intensive. In<br />
some specific asynchronous DS/CDMA system, the quasi-synchronous multiuser detection<br />
algorithm, whose matrix order is equal to the number of users, needn’t estimate MAI power levels,<br />
thereby resulting in lower computational complexity and high “near-far” resistance. In this paper<br />
the performance of quasi-synchronous multiuser detection algorithm is analysized theoretically,<br />
and the numerical results are presented.<br />
Keywords: Quasi-synchronous, Multiuser Detection, DS/CDMA, MAI, Telemetry System.<br />
1. Introduction<br />
DS/CDMA system is used in many communication systems because it has the capability of<br />
anti-jamming. Some results indicate that the CDMA system has larger system capacity than the<br />
TDMA system, but this result is based the hypothesis that the PN sequences are orthogonal with<br />
each other. If the DS/CDMA receiver use traditional single-user detector ( correlator or matched<br />
filter), the performance of a DS/CDMA system degrades due to Multiple Access Interference<br />
(MAI).<br />
In order to increase the system capacity of DS/CDMA system, Some researchers proposed the<br />
use of smart antenna or the power control in the DS/CDMA system to abate the effect of MAI,<br />
Others resort to the suboptimal multiuser detection such as linear decorrelation, successive<br />
interference cancellation and parallel interference cancellation.<br />
Most communication systems are asynchronous system. The DS/CDMA system in some<br />
telemetry System is a special asynchronous system. It has following specialties: 1) the mobile<br />
users have the inner timer, 2) the distance from the mobile users to base station are almost equal, 3)<br />
the mobile users in the system are fixedness, 4) the system work in simplex system. Considering<br />
these specialty and based the theory of synchronous decorrelation multiuser detection,<br />
Quasi-synchronous multiuser detection was used in the system to reduce the computation<br />
complexity. This paper analysis the performance of the quasi-synchronous multiuser detector<br />
theoretically, and compare with the synchronous decorrelation multiuser detection and the<br />
conventional detection. The numerical results are present.<br />
2. Quasi-synchronous DS/CDMA system<br />
S.Verdu proposed the optimal multiuser detector that is too complex for practical<br />
implementation. R.Lupas put forward the decorrelation multiuser detection, for synchronous case,