REFERENCES 1. M. Danesh, F. Gruson, P. Abele, and H. Schumacher, Differential VCO and frequency tripler using SiGe HBTs for the 24 GHz ISM band, IEEE Radio Frequency Integrated Circuits (RFIC) Symp Digest, (2003), 277–280. 2. A. Boudiaf, D. Bachelet, and C. Rumelhard, A high-efﬁciency and low-phase- noise 38-GHz pHEMT MMIC tripler, IEEE Trans Micro- wave Theory Tech 48 (2000), 2546 –2553. 3. M.D. Tsai, Y.H. Cho, and H. Wang, A 5-GHz low phase noise differ- ential colpitts CMOS VCO, IEEE Microwave Wireless Compon Lett 15 (2005), 327–329. 4. D.M. Klymyshyn and Z. Ma, Active frequency-multiplier design using CAD, IEEE Trans Microwave Theory Tech 51 (2003), 1377–1385. 5. D. Ozis, N.M. Neihart, and D.J. Allstot, Differential VCO and passive frequency doubler in 0.18m CMOS for 24 GHz applications, IEEE Radio Frequency Integrated Circuits Symp Digest, (2006). 6. C.-H. Chiu, K.-H. Liang, H.-Y. Chang and Y.-J. Chan, A low phase noise 26- GHz push-push VCO with a wide tuning range in 0.18-m CMOS technology, IEEE APMC Digest, (2006), 1128 –1131. 7. T.-P. Wang, R.-C. Liu, H.-Y. Chang, L.-H. Lu, and H. Wang, A 22-GHz push- push CMOS oscillator using micromachined inductors, IEEE Microwave Wireless Compon Lett 15 (2005), 859 – 861. 8. J.-H.C. Zhan, J.S. Duster, and K.T. Kornegay, A 25-GHz emitter degenerated LC VCO, IEEE JSSC 39 (2004), 2062–2064. 9. K. Kwok and J.R. Long, A 23-to-29 GHz Transconductor-Tuned VCO MMIC in 0.13 m CMOS, IEEE JSSC 42 (2007), 2878 –2886. © 2009 Wiley Periodicals, Inc. A SIMPLE DUAL-BAND FREQUENCY SELECTIVE SURFACE L. M. Arau ´ jo, 1 R. H. C. Manic ¸ oba, 1 A. L. P. S. Campos, 2 and A. G. d’Assunc ¸a ˜o 1 1 Electrical Engineering Department, Federal University of Rio Grande do Norte (UFRN), Natal, RN, Brazil 2 Departamento Acade ˆ mico de Tecnologia da Informac ¸a ˜ o e Indu ´ stria, Centro Federal de Educac ¸a ˜ o Tecnolo ´ gica do Rio Grande do Norte, Unidade de Ensino Descentralizada da Zona Norte de Natal, Rua Brusque, 2926, Conj. Santa Catarina-Potengi. CEP: 59112-490 Natal, Rio Grande do Norte, Brazil; Corresponding author: antonioluiz@cefetrn.br Received 14 August 2008 ABSTRACT: Design and experimental investigations are presented for a dual-band frequency selective surface (FSS) with perfectly conducting rectangular patch elements. The work was developed in two steps. In the ﬁrst step, two single-band FSS screens were designed to obtain resonant frequencies at 9.5 GHz and 10.5 GHz, each one with about 1.5 GHz band- width. In the second step, these single FSS screens were cascaded and sep- arated by an air gap layer to achieve a dual-band response. The proposed dual-band FSS screen is easy to analyze and to fabricate with low cost ma- terials and exhibits a low weight and easy to handle structure. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 942–944, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24236 Key words: dual-band FSS; frequency selective surface; simple FSS 1. INTRODUCTION The use of frequency selective surfaces (FSS) has been success- fully proven as a mean to increase the communication capabilities of satellite platforms. In space missions such as Voyager, Galileo, and Cassini, the use of dual-reﬂector antennas with FSS subreﬂec- tors has made it possible to share the main reﬂector among differ- ent frequency bands. Furthermore, the increasing demand on the multifunctional antennas for communication systems has required the development of FSS with multiband characteristics [1]. Therefore, frequency selective surfaces with dual-band and multiband responses have been studied by several researchers [1– 8]. Hill and Munk in [2] used a perturbation technique in a single-band FSS to obtain a single-layer dual-band FSS, but atten- uation lower than -10 dB was obtained. Huang et al. in [3] used a dual-layer FSS with circular elements to obtain a tri-band FSS. Double and single screens were used to reﬂect the X-band signal and transmit the S- and Ku-band signals, but they did not use a FSS to reﬂect two frequency bands simul- taneously. Besides, a little complex structure was presented. Wu in [4] designed and measured a four-band FSS with double square loop patch elements. The designed structure was complex with two layers separated by a honey comb. The structure was designed to reﬂect the Ka-band signal and transmit the S-, X-, and Ku-band signals. In [5], Wu and Lee designed a FSS with a similar response to that shown in [4] but with circular concentric nonsym- metric rings. A very complex structure was developed, with three layers and with cells out of phase. Parker and El Sheikh in [6] and Parker et al. in [7] used convoluted elements derived from linear and crossed dipoles in Figure 1 FSS geometry: (a) cascade structure and (b) unit cell TABLE 1 Dimensions of the Isolated FSS Structures 1 and 2 Parameter Structure 1 Structure 2 W 7 mm 8 mm L 10 mm 8 mm T x 22 mm 22 mm T y 22 mm 22 mm 942 MICROWAVE AND OPTICAL TECHNOLOGY LETTERS / Vol. 51, No. 4, April 2009 DOI 10.1002/mop