Ultra Wideband 234 1 bond wire transition equivalent model distributed capacitor on the carrier WB pad_die pad_carrier 2 MIM capacitor on the die On chip LNA Off chip antenna Fig. 17. Third order low pass filter embedding the bond wire transition. 7. Some results Many LNA prototypes have been implemented in a standard 0.13m CMOS technology. All the LNA outputs are loaded by a 60fF capacitor in order to emulate an ADC or a pulse detector load. The measurements instruments (spectrum analyser for the noise characterization and network analyser for scattering parameters measurements) are isolated at LNA output by using an on chip capacitance divider. For accurate characterization of the prototypes, the on chip capacitance divider has been also characterized on the same wafer to retrieve the output voltage from S parameters. The noise figure measurements are made with a spectrum analyzer and a noise source taking into account the mismatch at LNA output. The measurement results are summarized in Table 2 and compared to other published UWB LNAs. Tech. m BW GHz A re a mm 2 P DC mW Gain dB NF dB S 11 dB IIP3 dBm (Yu et al., 2007) 0.18 2.7-9.1 1.57 7 10 3.8-6.9 <-10 +1 (Heydari, 2007) 0.18 0.1-11 0.76 21.6 8 2.9 <-12 -3.5 (Chen, 2007) 0.18 2-11.5 0.33 13.4 14.8 3.1-4 <-10 +3 (Chen & Huang, 2007) 0.18 2.8-7.2 1.63 32 19.1 3-3.8 <-5 -1 (Reiha & Long, 2007) 0.13 3.1-10.6 0.87 9 15.1 2.1-2.8 <-10 -8.5 (Liao & Liu, 2007) 0.18 1.2-11.9 0.59 20 9.7 4.5-5.1 <-11 -6.2 (Shim et al., 2007) 0.18 0.4-10 0.42 12 12.4 4.4-6.5 <-10 -6 (Bevilacqua & Nikenejad, 2007) 0.18 2.9-11 0.98 9.5 16 3.8-4.4 <-10 - This work 0.13 6.8-8.8 1 0.4 15 29.5 3 4-5.2 <-10 -8.5 4 This work 5 0.13 6.8-8.8 1 0.5 21 30.6 3 - <-7.8 -8 4 This work 0.13 6-10 2 0.4 21.6 26.5 3 3.5- 4.6 <-12 -8 4 This work 5 0.13 6-10 2 0.5 22 28 3 - < -8 -8 4 This work 0.13 3.1-10.6 1 0.4 18 22 3 2.8-3.7 <-10 -7 4 This work 4 0.13 6.4-7.8 1 0.4 14 31 3 3.3-4.7 <-8 - 8 This work 4,5 0.13 6.4-7.8 1 0.5 20 34 3 3.4-4.7 <-8 -8 This work 4,6 0 .13 6.4-7.8 1 0.77 28 35 3 3.2-4.4 <-7 - 1 1dB bandwidth ; 2 0.5dB bandwidth ; 3 voltage gain ; 4 simulated value; 5 differential output, 6 fully differential Table 2. Summary of several published CMOS UWB LNA 8. Conclusion The design of Ultra-Wide-Band LC filters LNA has been presented in this chapter. Architectures for both small fractional bandwidths such as the 6-8.5 GHz ECC frequency band and for large fractional bandwidths such as 3.1-10.6 GHz FCC frequency band have been proposed. Based on an analytical modelling of the LC filters LNA architecture, a design methodology allowing the noise figure minimization and the voltage gain maximization has been presented. The LNA implementation in standard CMOS technologies in the context of integrated receivers has been considered. Simple layout rules allowing reliable designs have been proposed. Several LNA prototypes for different fractional bandwidths have been fabricated in a 0.13 m CMOS technology. Measurement results agree well with the simulations and compare favourably with other published LNA. 9. References Battista M., Gaubert J., Egels M., Bourdel S., Barthélemy H., 6-10 GHz Ultra Wide-Band CMOS LNA, Electronics Letters, February 2008, 44, (5), pp. 343-344. Battista M., Gaubert J., Egels M., Bourdel S., Barthélémy H., High Voltage Gain CMOS LNA For 6-8.5 GHz UWB Receivers, Transactions on Circuits And Systems—II, Vol. 55, N° 8, August 2008, pp. 713, 717. Battista M., Gaubert J., Fanei A., Bachelet Y., Egels M., Pannier Ph., Bourdel S., Barthelemy H., Bas G., Design and implementation of UWB CMOS LC filters LNA for carrier less impulse radio receivers, Analog Integr Circ Sig Process, February 2010, DOI 10.1007/s10470-009-9401-z Bevilacqua A., Niknejad A. M., An Ultrawideband CMOS Low Noise Amplifier for 3.1-10.6- GHz Wireless Receivers, IEEE Journal of Solid-State Circuits, 2004, 39, (12), pp. 2259- 2268. Bevilacqua A., Sandner C., Gerosa A., Neviani A., A Fully Integrated Differential CMOS LNA for 3–5-GHz Ultrawideband Wireless Receivers, IEEE Microwave and Wireless Components Letters, 2006, 16, (3) pp. 134-136. Chen H-K., Chang D-C., Juang Y-Z., Lu S-S., A Compact Wideband CMOS Low-Noise Amplifier Using Shunt Resistive-Feedback and Series Inductive-Peaking Techniques, IEEE Microwave and Wireless Components letters, 2007, 17, (8), pp. 616- 618. Chen Y-J E, Huang Y-I, Development of Integrated Broad-Band CMOS Low-Noise Amplifiers, IEEE Transactions on Circuits and Systems -I: regular papers, 2007, 54, (10), pp 2120-2127. Cubillo, J. R.; Gaubert, J.; Bourdel, S.; Barthelemy, H.; RF Low-Pass Design Guiding Rules to Improve PCB to Die Transition Applied to Different Types of Low-Cost Packages; Advanced Packaging, IEEE Transactions on; Volume 31, Issue 3, Aug. 2008, pp 527 – 535. Fanei A., Pannier Ph., Gaubert J., Battista M., Bachelet Y., Substrate noise in LC-matched ultra wide-band amplifier of UWB systems, IEEE Conference on Electron Devices and Solid State Circuits, EDSSC 2007, 20-22 December 2007, pp 469 – 472. Gaubert J., Egels M., Pannier Ph., Bourdel S., Design Method For broadband CMOS RF LNA, Electronics Letters, 2005, 41, (7), pp. 383-384. Design and implementation of ultra-wide-band CMOS LC lter LNA 235 1 bond wire transition equivalent model distributed capacitor on the carrier WB pad_die pad_carrier 2 MIM capacitor on the die On chip LNA Off chip antenna Fig. 17. Third order low pass filter embedding the bond wire transition. 7. Some results Many LNA prototypes have been implemented in a standard 0.13m CMOS technology. All the LNA outputs are loaded by a 60fF capacitor in order to emulate an ADC or a pulse detector load. The measurements instruments (spectrum analyser for the noise characterization and network analyser for scattering parameters measurements) are isolated at LNA output by using an on chip capacitance divider. For accurate characterization of the prototypes, the on chip capacitance divider has been also characterized on the same wafer to retrieve the output voltage from S parameters. The noise figure measurements are made with a spectrum analyzer and a noise source taking into account the mismatch at LNA output. The measurement results are summarized in Table 2 and compared to other published UWB LNAs. Tech. m BW GHz A re a m m 2 P DC mW Gain dB NF dB S 11 dB IIP3 dBm (Yu et al., 2007) 0.18 2.7-9.1 1.57 7 10 3.8-6.9 <-10 +1 (Heydari, 2007) 0.18 0.1-11 0.76 21.6 8 2.9 <-12 -3.5 (Chen, 2007) 0.18 2-11.5 0.33 13.4 14.8 3.1-4 <-10 +3 (Chen & Huang, 2007) 0.18 2.8-7.2 1.63 32 19.1 3-3.8 <-5 -1 (Reiha & Long, 2007) 0.13 3.1-10.6 0.87 9 15.1 2.1-2.8 <-10 -8.5 (Liao & Liu, 2007) 0.18 1.2-11.9 0.59 20 9.7 4.5-5.1 <-11 -6.2 (Shim et al., 2007) 0.18 0.4-10 0.42 12 12.4 4.4-6.5 <-10 -6 (Bevilacqua & Nikenejad, 2007) 0.18 2.9-11 0.98 9.5 16 3.8-4.4 <-10 - This work 0.13 6.8-8.8 1 0.4 15 29.5 3 4-5.2 <-10 -8.5 4 This work 5 0.13 6.8-8.8 1 0.5 21 30.6 3 - <-7.8 -8 4 This work 0.13 6-10 2 0.4 21.6 26.5 3 3.5- 4.6 <-12 -8 4 This work 5 0.13 6-10 2 0.5 22 28 3 - < -8 -8 4 This work 0.13 3.1-10.6 1 0.4 18 22 3 2.8-3.7 <-10 -7 4 This work 4 0.13 6.4-7.8 1 0.4 14 31 3 3.3-4.7 <-8 - 8 This work 4,5 0.13 6.4-7.8 1 0.5 20 34 3 3.4-4.7 <-8 -8 This work 4,6 0 .13 6.4-7.8 1 0.77 28 35 3 3.2-4.4 <-7 - 1 1dB bandwidth ; 2 0.5dB bandwidth ; 3 voltage gain ; 4 simulated value; 5 differential output, 6 fully differential Table 2. Summary of several published CMOS UWB LNA 8. Conclusion The design of Ultra-Wide-Band LC filters LNA has been presented in this chapter. Architectures for both small fractional bandwidths such as the 6-8.5 GHz ECC frequency band and for large fractional bandwidths such as 3.1-10.6 GHz FCC frequency band have been proposed. Based on an analytical modelling of the LC filters LNA architecture, a design methodology allowing the noise figure minimization and the voltage gain maximization has been presented. The LNA implementation in standard CMOS technologies in the context of integrated receivers has been considered. Simple layout rules allowing reliable designs have been proposed. Several LNA prototypes for different fractional bandwidths have been fabricated in a 0.13 m CMOS technology. Measurement results agree well with the simulations and compare favourably with other published LNA. 9. References Battista M., Gaubert J., Egels M., Bourdel S., Barthélemy H., 6-10 GHz Ultra Wide-Band CMOS LNA, Electronics Letters, February 2008, 44, (5), pp. 343-344. Battista M., Gaubert J., Egels M., Bourdel S., Barthélémy H., High Voltage Gain CMOS LNA For 6-8.5 GHz UWB Receivers, Transactions on Circuits And Systems—II, Vol. 55, N° 8, August 2008, pp. 713, 717. Battista M., Gaubert J., Fanei A., Bachelet Y., Egels M., Pannier Ph., Bourdel S., Barthelemy H., Bas G., Design and implementation of UWB CMOS LC filters LNA for carrier less impulse radio receivers, Analog Integr Circ Sig Process, February 2010, DOI 10.1007/s10470-009-9401-z Bevilacqua A., Niknejad A. M., An Ultrawideband CMOS Low Noise Amplifier for 3.1-10.6- GHz Wireless Receivers, IEEE Journal of Solid-State Circuits, 2004, 39, (12), pp. 2259- 2268. Bevilacqua A., Sandner C., Gerosa A., Neviani A., A Fully Integrated Differential CMOS LNA for 3–5-GHz Ultrawideband Wireless Receivers, IEEE Microwave and Wireless Components Letters, 2006, 16, (3) pp. 134-136. Chen H-K., Chang D-C., Juang Y-Z., Lu S-S., A Compact Wideband CMOS Low-Noise Amplifier Using Shunt Resistive-Feedback and Series Inductive-Peaking Techniques, IEEE Microwave and Wireless Components letters, 2007, 17, (8), pp. 616- 618. Chen Y-J E, Huang Y-I, Development of Integrated Broad-Band CMOS Low-Noise Amplifiers, IEEE Transactions on Circuits and Systems -I: regular papers, 2007, 54, (10), pp 2120-2127. Cubillo, J. R.; Gaubert, J.; Bourdel, S.; Barthelemy, H.; RF Low-Pass Design Guiding Rules to Improve PCB to Die Transition Applied to Different Types of Low-Cost Packages; Advanced Packaging, IEEE Transactions on; Volume 31, Issue 3, Aug. 2008, pp 527 – 535. Fanei A., Pannier Ph., Gaubert J., Battista M., Bachelet Y., Substrate noise in LC-matched ultra wide-band amplifier of UWB systems, IEEE Conference on Electron Devices and Solid State Circuits, EDSSC 2007, 20-22 December 2007, pp 469 – 472. Gaubert J., Egels M., Pannier Ph., Bourdel S., Design Method For broadband CMOS RF LNA, Electronics Letters, 2005, 41, (7), pp. 383-384. Ultra Wideband 236 Ginzton E. L., Hewlett W. R., Jasberg J. H., and Noe J. D., Distributed amplification, Proc. IRE, vol. 36, pp. 956–969, (Aug. 1948). Heydari P., Design Considerations for Low-Power Ultra Wideband Receivers, Proceedings of the Sixth International Symposium on Quality Electronic Design (ISQED’05), 2005, pp. 668-673. Heydari P., Design and Analysis of a Performance-Optimized CMOS UWB Distributed LNA, IEEE Journal of Solid-State Circuits, 2007, 42, (9), pp. 1892-1905. Kim, C W., Jung, M S. Lee, S G.: Ultra-wideband CMOS low noise amplifier, Electronics Letters, 2005, 41, (7), pp. 384-385. Liao C-F, Liu S-I, A Broadband Noise-Canceling CMOS LNA for 3.1–10.6-GHz UWB Receivers, IEEE Journal of Solid-State Circuits, 2007, 42, (2), pp 329-339. Nguyen T-K., Kim C-H, Ihm G-J, Yang M-S, Lee S-G, CMOS Low-Noise Amplifier Design Optimization Techniques, IEEE Transactions on Microwave Theory and Techniques, 2004, 52, (5), pp 1433-1442. Reiha M. T., Long J. R., A 1.2 V Reactive-Feedback 3.1–10.6 GHz Low-Noise Amplifier in 0.13 _m CMOS, IEEE Journal of Solid-State Circuits, 2007, 42, (5), pp. 1023-1033. Shim Y., Kim C-W., Lee J., Lee S-G., Design of Full Band UWB Common-Gate LNA, IEEE Microwave and Wireless Components letters, 2007, 17, (10), pp 721-723. Yu Y-H., Emery Chen Y-J., Heo D., A 0.6-V Low Power UWB CMOS LNA, IEEE Microwave and Wireless Components letters, 2007, 17, (3), pp. 229-231. Zhang F. and Kinget P., Low power programmable-gain CMOS distributed LNA for ultra- wideband applications, Symp. VLSI Circuits Dig. Tech. Papers, Jun. 2005, pp. 78–81. Zverev Anatol I., Handbook of Filter Synthesis, John Willey & Sons (New York, 1967), chapter. 6.10. CPW ultra-wideband circuits for wireless communications 237 CPW ultra-wideband circuits for wireless communications Mourad Nedil, Azzeddine Djaiz, Mohamed Adnane Habib and Tayeb Ahmed Denidni X CPW ultra-wideband circuits for wireless communications Mourad Nedil (1) , Azzeddine Djaiz (1) , Mohamed Adnane Habib (1) and Tayeb Ahmed Denidni (2) (1): UQAT-LRCS, University of Quebec in Abbitibi-Témiscaminque Canada (2): INRS-EMT, University of Quebec Canada 1. Introduction Wireless communications represent one of the highest growing markets, especially on the development of mobile communications and wireless local area networks (WLANs), where high capacity transmission systems are required. These concern new wideband RF wireless components such as antennas, filters and so on. Recently Ultra-Wideband (UWB) radio technology has been getting more popular for high- speed wireless connectivity applications, since the Federal Communications Commission (FCC)’s decision to permit the unlicensed operation band from 3.1 to 10.6 GHz in 2002 (Stutzman et al., 1998). The UWB radio system is very promising, since transmission data rates greater than those of the other wireless LAN systems can be obtainable with less power dissipation. In this area, various studies are under progress, especially in UWB filters, which is one of the key passive components in the design of microwave circuits for UWB systems. The requirements of an UWB filter are: low insertion loss over the operating band, good performances at low frequency and outside the operating band to meet FCC’s limits. Moreover, it is necessary to have a good group delay performance, which is strongly important to impulse-radio UWB systems. The conventional RF circuits design procedures are adequate only for relatively narrowband, but they are not suitable for wideband application. In addition, the most major challenge is to design an ultra-wideband RF circuit with about 110 % percent fractional- bandwidth requirement, which makes some widely used techniques for UWB designs inefficient. In this chapter, some UWB RF circuits will be presented and detailed. The chapter is organized as follows. After this introduction, the UWB transition and filters will be described in section II and III. In section IV, an analysis and design of a wideband directional coupler will be described. Section V, will present the UWB technique for an antenna. In the section VI, the UWB RF system will be presented. Finally, the last section presents the conclusion. 11 Ultra Wideband 238 2. Ultra-wideband Transitions Planar transmission lines such as microstrip and coplanar waveguide (CPW) have been applied in various microwave and millimeter-wave circuits. In some multilayered structures, these transmission lines coexist and are even combined to develop new circuit components (Nerguezian et al., 2005). For instance, multilayer microwave integrated circuits require more flexibility to use both microstrip and CPW circuit technologies. To ensure the compatibility between these technologies, low-loss, wideband, and compact transitions between microstrip and CPW lines are necessary. 2.1 Microstrip to CB-CPW transition There are two main techniques for the transition between a microstrip and CPW. One is by electrical contact, and the other electromagnetic coupling (Tanaka et al., 1988; Theodorou et al., 1995). One type uses vias to connect the top layer CPW ground planes with the lower microstrip ground plane and the other does not. The transitions with via holes are compact and broadband, but the vias cause parasitic inductance and are difficult to fabricate. Existing via-less transitions are narrow band and large. Transitions by electromagnetic coupling require no wire bonds or via holes, but most of them suffer from narrow bandwidth and larger size. Fig. 1. Layout of the microstrip-to-CB-CPW transition. Various approaches for transitions between microstrip and CPW lines on separate layers have been introduced such as electromagnetic coupling (Chen et al., 1996; Tran et al., 1993). In practice, additional conducting planes are often present below the substrate in order to electromagnetically separate the circuit from its environment (Tran et al., 1993). Vialess CBCPW-to-MSL transitions using electromagnetic (EM) coupling of three-line couplers have been reported (Burke et al., 1989; Zhu et al., 1999). However, the broadside CB-CPW to microstrip transition has never been proposed. L s W W 1 G e 1 2 W 2 S S G Bottom la y e r h h W 1 Top layer Common slot in g round p lane Fig. 2. Simulated and measured results of the UWB transition. In this section, an ultra-wideband microstrip to a CB-CPW transition using the frequency- dependent behavior of surface-to-surface slot coupling is proposed. Fig. 1 shows the geometrical layout of the proposed two-port microstrip-to-CB-CPW transition. This transition is characterized by an aperture formed on the common ground plane of the two-layered structures to provide a fed-through coupling between the upper microstrip and the lower CB-CPW lines. In this structure, the upper microstrip conductor is vertically coupled with the central strip conductor of the lower CB-CPW via a slot-coupled located in the common ground plane. To validate the proposed approach, a prototype circuit was designed, fabricated and measured. Simulation and experimental results of the transition are shown in Fig. 2. From these curves, it can be seen that a good agreement is observed and the microstrip to CB- CPW transition offers a very wide bandwidth of ~ 12 GHz. 2.2 Back-to-Back CB-CPW to CB-CPW Transition Some applications, such as multilayer microwave integrated circuits, require the flexibility to use the CPW circuits in deferent layers. Therefore, low-loss, wideband, and compact transitions between these layers are necessary to ensure good compatibility. In this area, vertical interconnections between various signal lines in different layers are often needed in a multilayer circuit environment. In this area, printed slots have been suggested to be versatile for vertical transitions. They can be implemented to couple electromagnetic energy from one side of a circuit module to another separated by a common conductor. The conductor backed coplanar waveguide (CBCPW) technology is an attractive option because it provides the benefit of added mechanical support and heat sinking ability compared to conventional CPW. Few works on CBCPW-to-CBCPW transitions have been done. However, these transitions are based only on via connections. In this subsection, a new type of CBCPW-to-CBCPW transition based on the concept of slot coupling in the common ground plane will be presented. This transition is characterized by 2 4 6 8 10 12 14 16 -60 -50 -40 -30 -20 -10 0 Magnitude (dB) Frequency (GHz) Simulated Measured CPW ultra-wideband circuits for wireless communications 239 2. Ultra-wideband Transitions Planar transmission lines such as microstrip and coplanar waveguide (CPW) have been applied in various microwave and millimeter-wave circuits. In some multilayered structures, these transmission lines coexist and are even combined to develop new circuit components (Nerguezian et al., 2005). For instance, multilayer microwave integrated circuits require more flexibility to use both microstrip and CPW circuit technologies. To ensure the compatibility between these technologies, low-loss, wideband, and compact transitions between microstrip and CPW lines are necessary. 2.1 Microstrip to CB-CPW transition There are two main techniques for the transition between a microstrip and CPW. One is by electrical contact, and the other electromagnetic coupling (Tanaka et al., 1988; Theodorou et al., 1995). One type uses vias to connect the top layer CPW ground planes with the lower microstrip ground plane and the other does not. The transitions with via holes are compact and broadband, but the vias cause parasitic inductance and are difficult to fabricate. Existing via-less transitions are narrow band and large. Transitions by electromagnetic coupling require no wire bonds or via holes, but most of them suffer from narrow bandwidth and larger size. Fig. 1. Layout of the microstrip-to-CB-CPW transition. Various approaches for transitions between microstrip and CPW lines on separate layers have been introduced such as electromagnetic coupling (Chen et al., 1996; Tran et al., 1993). In practice, additional conducting planes are often present below the substrate in order to electromagnetically separate the circuit from its environment (Tran et al., 1993). Vialess CBCPW-to-MSL transitions using electromagnetic (EM) coupling of three-line couplers have been reported (Burke et al., 1989; Zhu et al., 1999). However, the broadside CB-CPW to microstrip transition has never been proposed. L s W W 1 G e 1 2 W 2 S S G Bottom la y e r h h W 1 Top layer Common slot in g round p lane Fig. 2. Simulated and measured results of the UWB transition. In this section, an ultra-wideband microstrip to a CB-CPW transition using the frequency- dependent behavior of surface-to-surface slot coupling is proposed. Fig. 1 shows the geometrical layout of the proposed two-port microstrip-to-CB-CPW transition. This transition is characterized by an aperture formed on the common ground plane of the two-layered structures to provide a fed-through coupling between the upper microstrip and the lower CB-CPW lines. In this structure, the upper microstrip conductor is vertically coupled with the central strip conductor of the lower CB-CPW via a slot-coupled located in the common ground plane. To validate the proposed approach, a prototype circuit was designed, fabricated and measured. Simulation and experimental results of the transition are shown in Fig. 2. From these curves, it can be seen that a good agreement is observed and the microstrip to CB- CPW transition offers a very wide bandwidth of ~ 12 GHz. 2.2 Back-to-Back CB-CPW to CB-CPW Transition Some applications, such as multilayer microwave integrated circuits, require the flexibility to use the CPW circuits in deferent layers. Therefore, low-loss, wideband, and compact transitions between these layers are necessary to ensure good compatibility. In this area, vertical interconnections between various signal lines in different layers are often needed in a multilayer circuit environment. In this area, printed slots have been suggested to be versatile for vertical transitions. They can be implemented to couple electromagnetic energy from one side of a circuit module to another separated by a common conductor. The conductor backed coplanar waveguide (CBCPW) technology is an attractive option because it provides the benefit of added mechanical support and heat sinking ability compared to conventional CPW. Few works on CBCPW-to-CBCPW transitions have been done. However, these transitions are based only on via connections. In this subsection, a new type of CBCPW-to-CBCPW transition based on the concept of slot coupling in the common ground plane will be presented. This transition is characterized by 2 4 6 8 10 12 14 16 -60 -50 -40 -30 -20 -10 0 Magnitude (dB) Frequency (GHz) Simulated Measured Ultra Wideband 240 an aperture etched on the common ground plane of the two stacked layer CBCPW lines to provide a fed-through coupling between the upper CBCPW line and the lower CB-CPW line. This transition can offer advantages of broad bandwidth, compact size, low fabrication cost, and high reliability. Fig. 3. Layout of the CB-CPW-to-CB-CPW transition. Fig. 3 shows the geometrical layout of the proposed two-port CBCPW-to-CBCPW transition. This arrangement of the back-to-back CBCPW transition allows the both transmission lines to share a common ground plane. Each CBCPW line is formed by abruptly ending the slots as shown in Fig. 3. As a result, an RF current flows around the end of the slot, and therefore magnetic energy is stored behind the termination. Then, this energy is coupled via a rectangular slot located in the common ground plane from the top layer line to second line located in the bottom layer. CBCPW line Slot on ground plane CBCPW line P1 P2 W S L W 1 W 2 L g W g (a) (b) Top la y er Bottom la y er Slot on common ground plane To verify the performances of the proposed design, a back-to-back prototype transition was fabricated, and the scattering parameters were measured. Simulation and experimental results of the transition are shown in Fig. 4. From these curves, it can be seen that the comparison between simulated and experimental data shows a good agreement, and the CBCPW-to-CBCPW transition offers a very wide bandwidth of ~ 12 GHz, which operates well over almost the entire band of 3-15 GHz. Fig. 4. Simulated and measured results of the CB-CPW transition. 3. Ultra-Wideband Filters The conventional filter synthesis procedure is adequate only for the relatively narrowband filters, and it is not suitable for the wideband filters. In addition, the most difficult problem is to design ultra-wideband filter with about 110 % percent fractional-bandwidth requirement, which makes some widely used techniques for UWB designs inapplicable. 3.1 Ultra-Wideband Filter Design Based on CPW-to-Microstrip transition As mentioned, the most challenging problem in the design of UWB filter is the 110 % bandwidth requirement. For this issue, an UWB filter design is introduced. Fig. 5 shows the layout of the proposed filter. The filter structure is based on the back-to-back microstrip-to- CB-CPW transition described in the previous section. The filter is composed of two CBCPW to microstrip transitions and a microstrip line section, which is used as a multiple-mode (MMR) resonator between the two transitions. At the center frequency of the concerned UWB passband, both side sections of this MMR (CBCPW to microstrip transitions) are 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 -60 -50 -40 -30 -20 -10 0 Magnitude (dB) Frequency (GHz) Simulated Meassured S 12 S 11 CPW ultra-wideband circuits for wireless communications 241 an aperture etched on the common ground plane of the two stacked layer CBCPW lines to provide a fed-through coupling between the upper CBCPW line and the lower CB-CPW line. This transition can offer advantages of broad bandwidth, compact size, low fabrication cost, and high reliability. Fig. 3. Layout of the CB-CPW-to-CB-CPW transition. Fig. 3 shows the geometrical layout of the proposed two-port CBCPW-to-CBCPW transition. This arrangement of the back-to-back CBCPW transition allows the both transmission lines to share a common ground plane. Each CBCPW line is formed by abruptly ending the slots as shown in Fig. 3. As a result, an RF current flows around the end of the slot, and therefore magnetic energy is stored behind the termination. Then, this energy is coupled via a rectangular slot located in the common ground plane from the top layer line to second line located in the bottom layer. CBCPW line Slot on g round plane CBCPW line P1 P2 W S L W 1 W 2 L g W g (a) (b) Top la y er Bottom la y er Slot on common ground plane To verify the performances of the proposed design, a back-to-back prototype transition was fabricated, and the scattering parameters were measured. Simulation and experimental results of the transition are shown in Fig. 4. From these curves, it can be seen that the comparison between simulated and experimental data shows a good agreement, and the CBCPW-to-CBCPW transition offers a very wide bandwidth of ~ 12 GHz, which operates well over almost the entire band of 3-15 GHz. Fig. 4. Simulated and measured results of the CB-CPW transition. 3. Ultra-Wideband Filters The conventional filter synthesis procedure is adequate only for the relatively narrowband filters, and it is not suitable for the wideband filters. In addition, the most difficult problem is to design ultra-wideband filter with about 110 % percent fractional-bandwidth requirement, which makes some widely used techniques for UWB designs inapplicable. 3.1 Ultra-Wideband Filter Design Based on CPW-to-Microstrip transition As mentioned, the most challenging problem in the design of UWB filter is the 110 % bandwidth requirement. For this issue, an UWB filter design is introduced. Fig. 5 shows the layout of the proposed filter. The filter structure is based on the back-to-back microstrip-to- CB-CPW transition described in the previous section. The filter is composed of two CBCPW to microstrip transitions and a microstrip line section, which is used as a multiple-mode (MMR) resonator between the two transitions. At the center frequency of the concerned UWB passband, both side sections of this MMR (CBCPW to microstrip transitions) are 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 -60 -50 -40 -30 -20 -10 0 Magnitude (dB) Frequency (GHz) Simulated Meassured S 12 S 11 Ultra Wideband 242 identical, and they are chosen as one quarter-wavelength (λ g /4) while the middle section is set as one half-wavelength (λ g /2). Fig. 5. Layout of the CBCPW fed UWB filter Numerical simulations on the filter were carried out with the electromagnetic simulator ADS MOMENTUM. In these simulations, it is found that the out-of-band rejection at high frequencies can be improved by optimizing both CB-CPW and microstrip line of the transitions. To optimize the performance of the proposed filter, a parametric study was also performed and the optimal dimensions of the proposed filter are determined, in which L microstrip = 15.5 mm, L = 7.8 mm, L S = 8.1 mm, W = 1.4 mm, W 1 = 3.13 mm, W 2 = 2.68 mm, G = 1.83 mm, e = 0.15mm. Fig. 6. Photograph of the fabricated UWB filter. The fabricated filter was measured using a network analyzer HP8720, and its photograph is shown in Fig. 6. The simulated and measured results are shown in Fig. 7. It can be seen that the measured results agree well with the simulated ones. Both the measured and the simulated results show that, the proposed filter has a small insertion loss. Fig. 8 shows the simulated and measured results of the group delay. The group delay varies between 0.3 and 0.50 ns with a maximum variation of 0.2 ns, which leads to good linearity of the proposed UWB filter. The group delay of the proposed filter is found to be lower than that of the hybrid microstrip/CPW filter. From these results, it can be concluded that the proposed filter satisfies the requirements of a small and flat group delay over the operating band, which is strongly required for impulse radio systems to minimize the distortion in short pulse transmission system. L microstrip P2 S Bottom layer h h W 1 To p la y e r Common slot in ground plane CB-CPW to microstrip transition Side View G S Fig. 7. Simulated and measured results of the UWB filter. Fig. 8. Simulated and measured results of the group delay of the UWB filter. 3.2 Microstrip fed Ultra-Wideband Filter Similarly with the UWB filter introduced earlier, the second filter is composed of two microstrip–CBCPW transitions and a section of CBCPW transmission line is designed. The CBCPW feed line and the microstrip line are replaced by microstrip feed line and a section 1 2 3 4 5 6 7 8 9 10 11 12 13 0,0 0,2 0,4 0,6 0,8 1,0 Group delay (nS) Frequency (GHz) Simulated Measured  S 12 1 2 3 4 5 6 7 8 9 10 11 12 13 -70 -60 -50 -40 -30 -20 -10 0 Magnitude (dB) Frequency (GHz) Simulated Measured [...]... instance, needs to be combined with antenna array for beamswitching applications Such a feeding network must present ultra- wideband abilities An example of ultra- wideband butler matrix has been described based on ultra- wideband couplers and transitions Other passive devices such as ultra- wideband filters are connected to the antenna system in a complete receiver structure This interesting filed of research... radiation pattern at 5.8 GHz 7 Conclusion A non exhaustive overview of passive high frequency ultra- wideband devices has been presented In order to achieve ultra- wideband systems for high data rate transferring and ultra- short time performances, a complete beam-switching antenna system is requested Ultra- wideband antennas can be obtained through certain techniques such as thick impedance matching planar... been proposed (Lim et al., 199 9) Moreover, to improve directional coupler performances, the conductor-backed coplanar waveguide technology was also proposed to reduce the coupler size and to avoid air bridges used to connect ground planes of the conventional CPW technology (Lim et al., 199 9) In this area, few works on CB-CPW couplers have been reported in literature [6 -9] A 3-dB CBCPW coupled-line... operating bandwidth for impedance matching and high-gain radiation in desired directions CPW ultra- wideband circuits for wireless communications 255 5.1 Ultra- Wideband Monopole Xg n Y m Yg (a) (b) Fig 21 UWB monopole-like antenna (a): Antenna layout, (b): Antenna photograph Fig 21 shows a monopole-like ultra- wideband antenna The lower metallic surface represents the ground, and the upper arm is a quarter-wavelength... H-plane A good agreement between simulated and measured radiation patterns is observed CPW ultra- wideband circuits for wireless communications 0 0 330 300 60 90 -40 270 90 -30 -20 240 -20 120 Simulations Measurements -10 210 0 150 0 240 210 (b) 0 30 -10 0 330 30 -10 300 -20 60 300 -20 -30 60 -30 270 90 -30 -40 270 90 -30 -20 240 -20 120 Simulations Measurements -10 210 0 150 240 210 (d) 0 0 30 -10 150... ( k 1 ) (7)  a  tanh 1   2h  k1   b1  tanh   2h  (8) CoT = Co2 + Co1 (9) with a1 = tA and b1 = tB The total capacitance CoT is obtained as: The odd-mode permittivity oeff is defined as [9] ,  o , eff  C oT ( r ) C oT ( r ) (10) 250 Ultra Wideband The odd-mode characteristic impedance is given by [9] : Zo ,0   o , eff 60  K( k0 ) K( k1 )      K ( k'0 ) K ( k '1 )  (11) c)... be improved especially in low frequencies CPW ultra- wideband circuits for wireless communications 245 0 -10 -20 -30 M agnitude (d B ) -40 -50 -60 1 2 3 4 5 6 7 8 9 10 11 12 Frequency (GHz) Fig 10 Simulated and measured results of the proposed UWB filter   1,0 0 ,9 0,8 Simulated Measured Group delay (nS) 0,7 0,6 0,5 0,4 0,3 0,2 0,1 0,0 1 2 3 4 5 6 7 8 9 10 11 12 Frequency (GHz) Fig 11 Simulated and... (b) Fig 24 Antenna structure (a) UWB Antenna layout, (b) notched UWB antenna photograph 258 Ultra Wideband Variable Rs Rp Rn P 1 P2 w g wn Dimension (mm) 20 9 6 10.5 2 0.35 0.25 Table 1 Antenna dimensions Fig 25a shows that the real part of the antenna impedance fluctuates around 50Ω, while its imaginary part remains with small values and oscillates around zero; this is mainly because a continuous... Bialkowsky, M E (2008) Design of Ultrawideband Planar Monopole Antennas of Circular and Elliptical Shape, IEEE Trans Antenna and propagat., Vol 56, No 1, (Jan 2008) pp 2473-24 79, 0018 -92 6X Abbosh, M & Bialkowsky, M E (2006) A Planar UWB Antenna with Signal Rejection Capability in the 4-6GHz Band, IEEE Microw Wirel Comp Lett., Vol 54, No 6, (May 2006) pp 278-280, 1531-13 09 ... 0,8 Simulated Measured Group delay (nS) 0,7 0,6 0,5 0,4 0,3 0,2 0,1 0,0 1 2 3 4 5 6 7 8 9 10 11 12 Frequency (GHz) Fig 11 Simulated and measured results of group delay of the UWB filter 246 Ultra Wideband 4 Ultra- Wideband Directional Coupler Directional couplers are fundamental and indispensable components used in microwave integrated circuits applications Indeed, these components are often used in . environment (Tran et al., 199 3). Vialess CBCPW-to-MSL transitions using electromagnetic (EM) coupling of three-line couplers have been reported (Burke et al., 198 9; Zhu et al., 199 9). However, the broadside. environment (Tran et al., 199 3). Vialess CBCPW-to-MSL transitions using electromagnetic (EM) coupling of three-line couplers have been reported (Burke et al., 198 9; Zhu et al., 199 9). However, the broadside. 41, (7), pp. 383-384. Ultra Wideband 236 Ginzton E. L., Hewlett W. R., Jasberg J. H., and Noe J. D., Distributed amplification, Proc. IRE, vol. 36, pp. 95 6 96 9, (Aug. 194 8). Heydari P., Design