crostrip side-feeding and the lower aperture coupling are respec- tively adopted to excite the vertical and horizontal polarizations of the array, which bring about high isolation, low cross-polarization, and broad-bandwidth operation. On the other hand, based on the new LH-TL, the series network with the CRLH-TL is employed to feed the above array. Compared with the traditional design, this array possesses the advantages of simple fabrication, small size, low insertion loss, and high efficiency, which are easily applicable to larger-scale planar arrays. REFERENCES 1. R. Pokuls, J. Uher, and D.M. Pozar, Dual-frequency and dual-polar- ization microstrip antennas for SAR applications, IEEE Trans Anten- nas Propagat 46 (1998), 1289 –1296. 2. L.L. Shafai, W.A. Chamma, M. Baraket, P.C. Strickland, and G. Seguin, Dual-band dual-polarized perforated microstrip antennas for SAR applications, IEEE Trans Antennas Propagat 48 (2000), 58 – 66. 3. X.-L. Liang, S.-S. Zhong, and W. Wang, Cross-polarization suppres- sion of dual-polarization linear microstrip antenna arrays, Microwave Opt Technol Lett 42 (2004), 448 – 451. 4. T.S.P. See and Z.N. Chen, Design of dual-polarization stacked array for ISM band applications, Microwave J Opt Technol Lett 38 (2003), 142–147. 5. W. Choi, J.M. Kim, J.H. Bae, and C. Pyo, High-gain and broadband microstrip array antenna using combined structure of corporate and series feeding, IEEE Antennas Propagat Soc Int Symp Dig 3 (2004), 2484 – 2487. 6. Q. Zhu, Z. Zhang, S. Xu, and W. Ding, Millimeter-wave microstrip array design with CRLH-TL as feeding line, IEEE Antennas Propagat Soc Int Symp Dig 3 (2004), 3413–3416. © 2006 Wiley Periodicals, Inc. NOVEL DISTORTION RESILIENT OSNR MONITORING TECHNIQUE BASED ON EVALUATION OF ASYNCHRONOUS HISTOGRAMS R. Luı ´s, 1,2 A. Teixeira, 2 P. Andre ´, 2 and P. Monteiro 1,2 1 Siemens Portugal R. Irma ˜ os Siemens 1 2720-093 Amadora, Portugal 2 Instituto de Telecomunicac ¸o ˜ es University of Aveiro 3810-193 Aveiro, Portugal Received 3 January 2006 ABSTRACT: This paper presents a novel technique to evaluate OSNR using asynchronous histograms. The technique is based on a comparison between a numerically estimated asynchronous histogram of the signal to be measured and the monitored signal. Experimental validation of proposed technique is presented. Measurement errors below 1 dB are achieved for OSNR values below 32 dB. The proposed technique is also validated for cases where the monitored signal presents significant dispersion-induced distortion, without presenting significant loss of accuracy. The principal limitations of the proposed technique are also investigated. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 1369 –1372, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21648 Key words: optical monitoring; amplitude histogram; asynchronous histogram; optical signal-to-noise ratio The work presented in this paper was supported by Siemens Portugal, Department of Wired and Optical Networks, Optical Research Group. Figure 6 Performance of the planar linear array (400  20 mm 2 ): (a) S-parameters; (b) VSWR; (c) 2D radiation pattern of horizon polarization; (d) 2D radiation pattern of vertical polarization DOI 10.1002/mop MICROWAVE AND OPTICAL TECHNOLOGY LETTERS / Vol. 48, No. 7, July 2006 1369