notched frequency band, the antenna gain is about the same for both antennas. 4. CONCLUSIONS Two printed elliptical antennas are proposed. The first antenna is a printed elliptical antenna with notch cut fed by a microstrip line. They are designed for UWB applications. To obtain sufficient matching bandwidth, a partial ground plane and notch cut are used. The antenna is then modified to obtain frequency band notch function of 5.2/5.8 GHz by inserting a U-shaped slot beneath the notch cut in the elliptical patch. A parametric study is carried out to optimize the proposed structures. The measured bandwidth, defined by VSWR  2, for the designed antenna without U-shaped slot is 8.35 GHz. For the antenna with U-like slot, the measured bandwidth from 3.08 to 11.00 GHz with band rejection from 4.70 to 5.84 GHz is attained. The results indicate that simply by inserting a half-wavelength U-like slot beneath the notch cut in the radiator, the desired rejected frequency band can be obtained. The proposed simple-shaped antennas provide good radiation patterns and relatively flat gains over the entire frequency band excluding the rejected band. REFERENCES 1. S.H. Choi, J.K. Park, S.K. Kim, and J.Y. Park, A new ultra-wideband antenna for UWB applications, Microwave Opt Technol Lett 40 (2004), 399 – 401. 2. C.Y. Huang and W. C. Hsia, Planar elliptical antenna for ultrawide- band communications, Electron Lett 41 (2005), 296 –297. 3. S.W. Su, K.L. Wong, and C.L. Tang, Ultra-wideband square planar monopole antenna for IEEE 802.16a operation in the 2-11GHz band, Microw Opt Technol Lett 42 (2004), 463– 466. 4. Z.N. Chen, T.S. See, and X. Qing, Small printed ultrawideband an- tenna with reduced ground plane effect, IEEE Trans Antennas Propag 55 (2007), 383–388. 5. M.J. Ammann and Z.N. Chen, Wideband monopole antennas for multi-band wireless systems, IEEE Antennas Propag Mag 45 (2003), 146 –150. 6. W. Wang, S.S. Zhong, and S.B. Chen, A novel wideband coplanar-fed monopole antenna, Microwave Opt Technol Lett 43 (2004), 50 –52. 7. H.G. Schantz, and G.P. Wolenec, Ultra-wideband antenna having frequency selectivity, U.S. Patent Publication No. 2003/0090436 A1, 2003. 8. H.G. Schantz, G. Wolenec, and E.M. Myszka, III, Frequency notched UWB antennas, In: Proceedings IEEE Conference on Ultra Wideband Systems and Technol, Reston, Virginia, 2003, pp. 214 –218. 9. A. Kerkhoff and H. Ling, A parametric study of band-notched UWB planar monopole antennas, In: IEEE Antennas Propagation-Society International Symposium Monterey, California, 2004, pp. 1768 –1771. 10. H. Yoon, H. Kim, K. Chang, Y.J. Yoon, and Y.H. Kim, A study on the UWB antenna with band-rejection characteristic, In: IEEE Antennas Propagation-Society International Symposium, Monterey, California, 2004, pp. 1784 –1787. 11. HFSS™, v10, Ansoft Corporation Software, Pittsburgh, PA, USA. © 2009 Wiley Periodicals, Inc. OPTICALLY ENVELOPE DETECTED QAM AND QPSK RF MODULATED SIGNALS IN HYBRID WIRELESS-FIBER SYSTEMS Idelfonso Tafur Monroy, Kamau Prince, Jorge Seoane, and Xianbin Yu Department of Photonics Engineering, Technical University of Denmark, DK-2800, Kgs. Lyngby, Denmark; Corresponding author: idtm@fotonik.dtu.dk Received 20 July 2008 ABSTRACT: We experimentally demonstrate optical envelope detection of 40 Mbaud 16-QAM and QPSK RF modulated signals. The proposed system employs an electro-absorption modulator performing the function of an optical halfwave rectifier. In this experiment, the QAM and QPSK signals are frequency down converted from a 1.6 GHz carrier frequency to an IF at 500 MHz, requiring no high frequency local oscillator and mixer at the remote base station. This result proves the feasibility of optical envelope detection for complex modulation formats of RF signals for hybrid wireless-fiber transmission links. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 864 – 866, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop. 24182 Key words: envelope detection; optical halfwave rectification; hybrid wireless-fiber systems; radio-over-fiber 1. INTRODUCTION Hybrid optical wireless systems are foreseen to play an important role in future high capacity access networks [1]. By combining the advantages of high capacity optical fiber transmission and the flexibility of wireless technologies, hybrid optical-wireless net- works will pave the way for a seamless broadband service expe- rience for the end-user. However, to make reality the promises of these systems, simplified and cost-efficient signal generation and detection methods are indispensable. Moreover, for system con- vergence purposes, it is interesting to share photonic building blocks and use common technologies for both systems. Further- more, simplifying the equipment at the base antenna stations and wireless access points will further improve the cost/performance ratio of hybrid optical wireless systems. Optical envelope detection of wireless signals has been recently proposed by the authors as a method to detect and demodulate wireless signals by avoiding the use of complex radio frequency (RF) mixers and local oscillator stages [2]. In [2], optical envelope detection of an ASK modulated RF signal was demonstrated. However, wireless systems com- monly employ advanced modulation formats. In this article, we experimentally demonstrate successful demodulation of 16 QAM and QPSK modulation formats by optical envelope detection. The proposed envelope detection systems use common photonic tech- nologies with optical access systems. Figure 9 Simulated gains. [Color figure can be viewed in the online issue, which is available at www.interscience.wiley.com] 864 MICROWAVE AND OPTICAL TECHNOLOGY LETTERS / Vol. 51, No. 3, March 2009 DOI 10.1002/mop