**4.3. Generic architecture**

With the proposed antenna topology and FSD-architectures, we obtained a generic configuration that can be used as a configurative template for finding the perfect antenna configuration (shape + dimension) which fulfills the constraints place on sizes, bandwidth, and dispersion (pattern, gain flatness, linear phase).

Figure 6 shown typically some of the many possible UWB/SWB antenna configurations, which are all generated by varying just some of the design parameters of the same original generic architecture, proposed in Figure 5. Note that all of these antennas are UWB/SWB, and although they are subsets of the generic configuration, but only one third of them worth to be called UWB/SWB antennas when their usable UWB/SWB patterns are considered. It is worthy to note that the antennas (2, 3, 4, 5, 6, 7, 9, 10, 11, 13) generated by our generic architecture have been intended/published/patented by other researchers several years ago. Our generic architecture generalized, showed the connections between them, and proved that they are just particular cases of the introduced architecture.

**Figure 6.** Proposed configuration: a) Architecture and parameters, b) logical functional sections.

#### **4.4. Parameter identification and optimizations**

164 Ultra Wideband – Current Status and Future Trends

• Then to the *internal transition section*—this section is intentionally inserted between the feed and the patch for the purpose of impedance matching, its shape was logically chosen so that it able to serve the design-properties: resonance shifting, impedance matching, and also enable parameter to serve as independent optimized parameter. • In addition to the *radiating section*, we divided it in to two sub-sections, which are the *patch section* and the *external transition*. The patch section creates an extra degree of freedom to ease the optimization process, and the radiating section provides parameter for shaping radiation patterns. Two round areas had been added to the top corners of the patch for the purpose of 1) diminishing of diffraction at the antenna's top vertices (deformation of sharp corner in to circular edge) and, 2) controlling and retaining the shaped of the radiation patterns at high frequency band of the spectrum, and, 3) subduing the number of parameters to accelerate the optimization process. These four

• Start orderly from section I, II, IIIA and IIIB (this bottom-up strategy prefers matching

• Identify the parameters associate with that section, select the parameter that

• Isolate the effect of that parameter so that an optimization only on that parameter can be undergone, without affecting too much the performance of other sections.

Based on the FSD approach the prototype 1 was first designed and evaluated (Tran et al. 2007). Its designed parameters are used as *start values* for the optimization process of all the later prototypes. Four prototypes (1, 2, 3, 4 shown in fig.4) were successful designed and evaluated, the prototype 4 proved to be a radiator which is superior to the others in that

With the proposed antenna topology and FSD-architectures, we obtained a generic configuration that can be used as a configurative template for finding the perfect antenna configuration (shape + dimension) which fulfills the constraints place on sizes, bandwidth,

Figure 6 shown typically some of the many possible UWB/SWB antenna configurations, which are all generated by varying just some of the design parameters of the same original generic architecture, proposed in Figure 5. Note that all of these antennas are UWB/SWB, and although they are subsets of the generic configuration, but only one third of them worth to be called UWB/SWB antennas when their usable UWB/SWB patterns are considered. It is worthy to note that the antennas (2, 3, 4, 5, 6, 7, 9, 10, 11, 13) generated by our generic architecture have been intended/published/patented by other researchers several years ago.

both of its impedance bandwidth and radiation pattern are SWB-sustainable.

sections are orderly numerated as I, II, IIIA, and IIIB in Figure 5b.

In summary, the FSD approach assumed the following steps:

impedance bandwidth in prior of pattern bandwidth);

predominantly influences the function of that section.

• Keep the antenna's overall dimension small and fixed;

• Separate and understand the role of each section;

and dispersion (pattern, gain flatness, linear phase).

**4.3. Generic architecture** 

**Prototype 1**: elaborated by (Tran et al. op. cit.), formed a basis for the designs of the later prototypes. Its 10GHz impedance bandwidth and designed parameters are plotted in fig.9 and listed in table 2, respectively. For the detailed works and the measurement results, the reader should refer to (Tran et al., op. cit). The other prototypes all took the designed parameters of prototype 1 as start-values, and used the FSD to identify the significant parameter for its SVO process of bandwidth broadening.

**Prototype 2**: is obtained by taking the start values of the prototype 1, and using FSD to identify the LT as its significant parameter for SVO process. The resulting designed parameters and the impedance bandwidth are listed in 2nd column of table 2, and Fig.9, respectively. The SVO demonstrated the solidity of the FSD approach that the bandwidth can be doubled (from 10GH to 20 GHz) by optimization of just a single parameter LT. For details of the elaborated work, please refer to (Tanyer et al., 2009a, op cit.)

**Prototype 3**: by keeping LT fixed, the prototype 3 is obtained by optimizing the lower part of the radiation section which comprised of two parameters LR2 and WT, the first make the total length of the radiator shorter ( thus affects the higher frequency), whist the second parameter provide an better match (i.e., lower reflection coefficient). By doing two SVO sequentially (first with parameters LR2, then WT) we again doubled the nominal BW (form 20GHz to 45GHz), in term of ratio bandwidth it is of BR = 9:1 as shown in Fig. 10. The resulting parameters are listed in column 3rd table 2. Further details of measurements and other properties of this prototype 3, are detailed in (Tanyer et al., 2009b, op. cit).

**Prototype 4**: is obtained by the combined optimization of the FSD-identified parameters WT and WC, By keeping the optimized parameters of the previous optimization steps (LT of prototype 3, all others of prototype 1) fixed, and doing 2 SVO sequences, we obtain the SWB impedance bandwidth of BR greater than 30:1, the result is plotted in Figure 9, the corresponding design parameters are listed in table 2. We noted here that by controlling radii-separation distance WC we are able to keep the radiation pattern of this prototype less distorted till 50GHz as shown in Figure 8.

Architecture and Design Procedure of a Generic SWB Antenna with Superb Performances for Tactical Commands and Ubiquitous Communications 167

• **Dimensional flexibility**: the width of the signal line, and hence the corresponding gaps, can be freely designed to accordingly support the physical dimension of the

• **Dielectric support**: The dielectric thickness exerts negligible weight on the economy of

The tapered transition has been inserted between the CPW-feed and the radiating patch, this section responsible for a smooth transition between the feed and the antenna, and because the current distribution is denser in this region than the others, this property indicated that this section must have strongest influence in matching the impedance bandwidth. This section has two parameters (LT, WT), which are described in details in §4.6.1 and §4.6.2

The length LT of the tapered transition (section II) is responsible for the smooth transition between the feed and antenna, and proved to be the most sensitive parameter in the design of our prototypes. Anticipation from the theory and design of micro-strip antenna (MSA), it is well-known that the length of the MSA determines the resonance frequency (by lengthen or shorten this parameter, one can shift the resonance frequency to lower or higher band,

The antenna's resonance is affected by its length, this length is composed by LT + LR1 + LR2, when this composed length is changed, and the resonance will presumably change

It is observed, from the results plotted in Fig.9, that when LT is longer the resonance will shift to lower frequency (as shown by prototype 1, LT = 3.64, Fig.9), and when LT is shorter

The width WT of the taper transition section (section II), is also a "share-parameter" with lower radiating section (section IIIA); this width provides, as similar role as the width in microstrip patch antenna, a fine-tune mechanism for impedance matching as its nominal value varies. This enhanced matching mechanism are numerically demonstrated with the reflection coefficients of the prototypes 3 and 4 as plotted in Fig. 10, in which they shown a

This section comprise of six parameters LR1, LR2, WT, WR, WC, and RC, in which WT is the share parameter described in §4.6.2, we divided this section into sub-sections IIA and IIB

the radiator's resonance will shift to higher frequency (prototype 2, LT= 1.64, Fig.9)

transition region and the antenna.

**4.6. Section II: The tapered transition** 

*4.6.1. The internal Transition Length LT* 

*4.6.2. The internal Transition Width WT* 

lower reflection coefficient, i.e., a better match.

**4.7. Section III: The radiation section** 

the CPW-impedance

below.

respectively).

accordingly.

The created parameters, their functions, their effects and their usages are discussed in greater details in the next sub-sections. The FSD is detailed in §4.5-4.7, the resulted SWBperformances are given in §4.8 and in §4.9, the optimizations of all the prototypes are discussed in details.
