- •Contents
- •Preface
- •Chapter 1 Introduction (K. Fujimoto)
- •Chapter 2 Small antennas (K. Fujimoto)
- •Chapter 3 Properties of small antennas (K. Fujimoto and Y. Kim)
- •Chapter 4 Fundamental limitation of small antennas (K. Fujimoto)
- •Chapter 5 Subjects related with small antennas (K. Fujimoto)
- •Chapter 6 Principles and techniques for making antennas small (H. Morishita and K. Fujimoto)
- •Chapter 7 Design and practice of small antennas I (K. Fujimoto)
- •Chapter 8 Design and practice of small antennas II (K. Fujimoto)
- •Chapter 9 Evaluation of small antenna performance (H. Morishita)
- •Chapter 10 Electromagnetic simulation (H. Morishita and Y. Kim)
- •Chapter 11 Glossary (K. Fujimoto and N. T. Hung)
- •Acknowledgements
- •1 Introduction
- •2 Small antennas
- •3 Properties of small antennas
- •3.1 Performance of small antennas
- •3.1.1 Input impedance
- •3.1.4 Gain
- •3.2 Importance of impedance matching in small antennas
- •3.3 Problems of environmental effect in small antennas
- •4 Fundamental limitations of small antennas
- •4.1 Fundamental limitations
- •4.2 Brief review of some typical work on small antennas
- •5 Subjects related with small antennas
- •5.1 Major subjects and topics
- •5.1.1 Investigation of fundamentals of small antennas
- •5.1.2 Realization of small antennas
- •5.2 Practical design problems
- •5.3 General topics
- •6 Principles and techniques for making antennas small
- •6.1 Principles for making antennas small
- •6.2 Techniques and methods for producing ESA
- •6.2.1 Lowering the antenna resonance frequency
- •6.2.1.1 SW structure
- •6.2.1.1.1 Periodic structures
- •6.2.1.1.3 Material loading on an antenna structure
- •6.2.2 Full use of volume/space circumscribing antenna
- •6.2.3 Arrangement of current distributions uniformly
- •6.2.4 Increase of radiation modes
- •6.2.4.2 Use of conjugate structure
- •6.2.4.3 Compose with different types of antennas
- •6.2.5 Applications of metamaterials to make antennas small
- •6.2.5.1 Application of SNG to small antennas
- •6.2.5.1.1 Matching in space
- •6.2.5.1.2 Matching at the load terminals
- •6.2.5.2 DNG applications
- •6.3 Techniques and methods to produce FSA
- •6.3.1 FSA composed by integration of components
- •6.3.2 FSA composed by integration of functions
- •6.3.3 FSA of composite structure
- •6.4 Techniques and methods for producing PCSA
- •6.4.2 PCSA employing a high impedance surface
- •6.5 Techniques and methods for making PSA
- •6.5.2 Simple PSA
- •6.6 Optimization techniques
- •6.6.1 Genetic algorithm
- •6.6.2 Particle swarm optimization
- •6.6.3 Topology optimization
- •6.6.4 Volumetric material optimization
- •6.6.5 Practice of optimization
- •6.6.5.1 Outline of particle swarm optimization
- •6.6.5.2 PSO application method and result
- •7 Design and practice of small antennas I
- •7.1 Design and practice
- •7.2 Design and practice of ESA
- •7.2.1 Lowering the resonance frequency
- •7.2.1.1 Use of slow wave structure
- •7.2.1.1.1 Periodic structure
- •7.2.1.1.1.1 Meander line antennas (MLA)
- •7.2.1.1.1.1.1 Dipole-type meander line antenna
- •7.2.1.1.1.1.2 Monopole-type meander line antenna
- •7.2.1.1.1.1.3 Folded-type meander line antenna
- •7.2.1.1.1.1.4 Meander line antenna mounted on a rectangular conducting box
- •7.2.1.1.1.1.5 Small meander line antennas of less than 0.1 wavelength [13]
- •7.2.1.1.1.1.6 MLAs of length L = 0.05 λ [13, 14]
- •7.2.1.1.1.2 Zigzag antennas
- •7.2.1.1.1.3 Normal mode helical antennas (NMHA)
- •7.2.1.1.1.4 Discussions on small NMHA and meander line antennas pertaining to the antenna performances
- •7.2.1.2 Extension of current path
- •7.2.2 Full use of volume/space
- •7.2.2.1.1 Meander line
- •7.2.2.1.4 Spiral antennas
- •7.2.2.1.4.1 Equiangular spiral antenna
- •7.2.2.1.4.2 Archimedean spiral antenna
- •7.2.2.1.4.3.2 Gain
- •7.2.2.1.4.4 Radiation patterns
- •7.2.2.1.4.5 Unidirectional pattern
- •7.2.2.1.4.6 Miniaturization of spiral antenna
- •7.2.2.1.4.6.1 Slot spiral antenna
- •7.2.2.1.4.6.2 Spiral antenna loaded with capacitance
- •7.2.2.1.4.6.3 Archimedean spiral antennas
- •7.2.2.1.4.6.4 Spiral antenna loaded with inductance
- •7.2.2.2 Three-dimensional (3D) structure
- •7.2.2.2.1 Koch trees
- •7.2.2.2.2 3D spiral antenna
- •7.2.2.2.3 Spherical helix
- •7.2.2.2.3.1 Folded semi-spherical monopole antennas
- •7.2.2.2.3.2 Spherical dipole antenna
- •7.2.2.2.3.3 Spherical wire antenna
- •7.2.2.2.3.4 Spherical magnetic (TE mode) dipoles
- •7.2.2.2.3.5 Hemispherical helical antenna
- •7.2.3 Uniform current distribution
- •7.2.3.1 Loading techniques
- •7.2.3.1.1 Monopole with top loading
- •7.2.3.1.2 Cross-T-wire top-loaded monopole with four open sleeves
- •7.2.3.1.3 Slot loaded with spiral
- •7.2.4 Increase of excitation mode
- •7.2.4.1.1 L-shaped quasi-self-complementary antenna
- •7.2.4.1.2 H-shaped quasi-self-complementary antenna
- •7.2.4.1.3 A half-circular disk quasi-self-complementary antenna
- •7.2.4.1.4 Sinuous spiral antenna
- •7.2.4.2 Conjugate structure
- •7.2.4.2.1 Electrically small complementary paired antenna
- •7.2.4.2.2 A combined electric-magnetic type antenna
- •7.2.4.3 Composite structure
- •7.2.4.3.1 Slot-monopole hybrid antenna
- •7.2.4.3.2 Spiral-slots loaded with inductive element
- •7.2.5 Applications of metamaterials
- •7.2.5.1 Applications of SNG (Single Negative) materials
- •7.2.5.1.1.2 Elliptical patch antenna
- •7.2.5.1.1.3 Small loop loaded with CLL
- •7.2.5.1.2 Epsilon-Negative Metamaterials (ENG MM)
- •7.2.5.2 Applications of DNG (Double Negative Materials)
- •7.2.5.2.1 Leaky wave antenna [116]
- •7.2.5.2.3 NRI (Negative Refractive Index) TL MM antennas
- •7.2.6 Active circuit applications to impedance matching
- •7.2.6.1 Antenna matching in transmitter/receiver
- •7.2.6.2 Monopole antenna
- •7.2.6.3 Loop and planar antenna
- •7.2.6.4 Microstrip antenna
- •8 Design and practice of small antennas II
- •8.1 FSA (Functionally Small Antennas)
- •8.1.1 Introduction
- •8.1.2 Integration technique
- •8.1.2.1 Enhancement/improvement of antenna performances
- •8.1.2.1.1 Bandwidth enhancement and multiband operation
- •8.1.2.1.1.1.1 E-shaped microstrip antenna
- •8.1.2.1.1.1.2 -shaped microstrip antenna
- •8.1.2.1.1.1.3 H-shaped microstrip antenna
- •8.1.2.1.1.1.4 S-shaped-slot patch antenna
- •8.1.2.1.1.2.1 Microstrip slot antennas
- •8.1.2.1.1.2.2.2 Rectangular patch with square slot
- •8.1.2.1.2.1.1 A printed λ/8 PIFA operating at penta-band
- •8.1.2.1.2.1.2 Bent-monopole penta-band antenna
- •8.1.2.1.2.1.3 Loop antenna with a U-shaped tuning element for hepta-band operation
- •8.1.2.1.2.1.4 Planar printed strip monopole for eight-band operation
- •8.1.2.1.2.2.2 Folded loop antenna
- •8.1.2.1.2.3.2 Monopole UWB antennas
- •8.1.2.1.2.3.2.1 Binomial-curved patch antenna
- •8.1.2.1.2.3.2.2 Spline-shaped antenna
- •8.1.2.1.2.3.3 UWB antennas with slot/slit embedded on the patch surface
- •8.1.2.1.2.3.3.1 A beveled square monopole patch with U-slot
- •8.1.2.1.2.3.3.2 Circular/Elliptical slot UWB antennas
- •8.1.2.1.2.3.3.3 A rectangular monopole patch with a notch and a strip
- •8.1.2.1.2.3.4.1 Pentagon-shape microstrip slot antenna
- •8.1.2.1.2.3.4.2 Sectorial loop antenna (SLA)
- •8.1.3 Integration of functions into antenna
- •8.2 Design and practice of PCSA (Physically Constrained Small Antennas)
- •8.2.2 Application of HIS (High Impedance Surface)
- •8.2.3 Applications of EBG (Electromagnetic Band Gap)
- •8.2.3.1 Miniaturization
- •8.2.3.2 Enhancement of gain
- •8.2.3.3 Enhancement of bandwidth
- •8.2.3.4 Reduction of mutual coupling
- •8.2.4 Application of DGS (Defected Ground Surface)
- •8.2.4.2 Multiband circular disk monopole patch antenna
- •8.2.5 Application of DBE (Degenerated Band Edge) structure
- •8.3 Design and practice of PSA (Physically Small Antennas)
- •8.3.1 Small antennas for radio watch/clock systems
- •8.3.2 Small antennas for RFID
- •8.3.2.1 Dipole and monopole types
- •8.3.2.3 Slot type antennas
- •8.3.2.4 Loop antenna
- •Appendix I
- •Appendix II
- •References
- •9 Evaluation of small antenna performance
- •9.1 General
- •9.2 Practical method of measurement
- •9.2.1 Measurement by using a coaxial cable
- •9.2.2 Method of measurement by using small oscillator
- •9.2.3 Method of measurement by using optical system
- •9.3 Practice of measurement
- •9.3.1 Input impedance and bandwidth
- •9.3.2 Radiation patterns and gain
- •10 Electromagnetic simulation
- •10.1 Concept of electromagnetic simulation
- •10.2 Typical electromagnetic simulators for small antennas
- •10.3 Example (balanced antennas for mobile handsets)
- •10.3.2 Antenna structure
- •10.3.3 Analytical results
- •10.3.4 Simulation for characteristics of a folded loop antenna in the vicinity of human head and hand
- •10.3.4.1 Structure of human head and hand
- •10.3.4.2 Analytical results
- •11 Glossary
- •11.1 Catalog of small antennas
- •11.2 List of small antennas
- •Index
8.1 FSA (Functionally Small Antennas) |
309 |
|
|
Points define spline curve
Optimized spline curve
Points are moving perpendicular to original curve
Original
curve
|
Boundary |
|
where the |
|
design is |
|
restricted |
Optimized |
Non- |
area |
optimized |
|
section |
Figure 8.53 Shape optimization for the flare dipole; a spline is defined at points placed around the perimeter of the flare dipole arc ([33a], copyright C 2009 IEEE and [33b], copyright C 2007 IEEE).
achieved by optimizing the flare shape and employing multiple stage L-C matching circuits at its feeding port. The initial flare dipole has gain greater than 0 dBi beyond 280 MHz, but the same gain at lower frequencies around 190 MHz without affecting bandwidth is achieved by an optimized flare dipole.
To lower the resonance frequency, the outer shape curved portion is modified by optimization of the shape, taking points distributed along the circular arc to define a spline as shown in Figure 8.53, illustrating an approach for shape optimization of the flare dipole; points are placed around the arc perimeter to define a Spline.
A printed shape-optimized dipole is illustrated in Figure 8.54: (a) the photo,
(b) simulated and measured return loss, (c) measured gain for the original and optimized dipole, and (d) an enlarged version for the lower frequency regions of (c).
To match the antenna impedance, N number of two port network/stages are designed by applying the optimizing process, which is described in [33b].
More about spline-shaped UWB antennas will be described in the next section.
8.1.2.1.2.3.2 Monopole UWB antennas
The simplest monopole UWB antenna is a half-sized planar square dipole with the ground plane on the same plane. Most monopole-type UWB antennas have modified
310 |
Design and practice of small antennas II |
|
|
dBi
10
5
0
−5
−10
−15
−20
−25
Return loss
0
−5
dB |
−10 |
|
|
|
−15 |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Measured |
|
||
|
|
|
−20 |
|
|
|
|
Simulated with HFSS |
|||
|
|
|
0.2 |
|
0.4 |
0.6 |
|
0.8 |
1.0 |
||
|
|
|
|
|
|
||||||
|
|
|
|
|
|
|
GHz |
|
|
|
|
|
(a) |
|
|
|
|
|
(b) |
|
|
|
|
|
|
Measured gain |
|
|
1 |
|
Measured gain |
|
|
||
|
|
|
|
|
|
|
|
|
|
||
|
|
|
|
|
0 |
|
|
|
|
|
|
|
|
|
|
|
−1 |
|
|
|
|
|
|
|
|
|
|
dBi |
−2 |
|
|
|
|
|
|
|
|
|
|
|
|
90 MHz |
|
|
|||
|
|
|
|
|
−3 |
|
|
|
|||
|
|
|
|
|
|
|
|
|
|
||
|
|
Shape optimized |
|
−4 |
|
|
Shape optimized |
|
|||
|
|
|
|
|
|
|
|||||
|
|
Original flare dipole |
|
−5 |
|
|
Original flare dipole |
||||
0.2 |
0.4 |
0.6 |
0.8 |
1.0 |
0.18 |
0.21 |
0.24 |
0.27 |
0.30 |
||
0.15 |
|||||||||||
|
|
GHz |
|
|
|
|
GHz |
|
|
|
|
|
|
(c) |
|
|
|
|
(d) |
|
|
|
|
Figure 8.54 (a) Printed shape optimized flare dipole, (b) simulated and measured return loss of the optimized dipole, (c) measured gain of the original and optimized dipole, and (d) expanded version of (c) around 0.2 GHz. ([33], copyright C 2009 IEEE).
shape, that is, the patch sides are modified to attain longer current paths, and the number of current paths increases so as to achieve multiple resonances beginning from lower frequencies, and consequently produce wideband behavior. The representative ones are illustrated in Figure 8.55, where (a) and (b) are a beveled square patch [34], (c) a patch with binomial curve [35], (d) with staircase-profile [36], and (e) with spline-shape [38].
8.1 FSA (Functionally Small Antennas) |
311 |
|
|
(a) |
(b) |
(c) |
(d) |
(e) |
Figure 8.55 Various planar monopole antennas.
Most monopole UWB antennas have planar structure and are placed on the same plane with the reduced-size ground plane that allows reduction of total size (volume) of the antenna and makes integration of an antenna into electronic devices easy.
8.1.2.1.2.3.2.1 Binomial-curved patch antenna
The edge curve of a printed patch modified in shape according to the binomial function is introduced in [35]. Antenna geometry is illustrated along with geometrical parameters in Figure 8.56. The curved boundary as a function of the coordinates (x, y) is expressed by
y = f (x) = G + (x/2w)N |
(8.1) |
where G is the gap between the patch and the ground plane, w is the width of the top side of the patch, is the length of the patch, and N is the order of the binomial function. As N increases from unity toward infinity, the shape varies from triangular to nearly rectangular. By parametric analysis, it was found that the optimum values for G and N are 0.45 mm and 4, respectively, with other parameters fixed; w = 30 mm,
312 |
Design and practice of small antennas II |
|
|
y
w
E(w/2,
)
G |
x |
|
L |
|
W |
Figure 8.56 Geometry of the planar binomial-curved monopole antenna ([34], copyright C 2010 IEEE).
|
0 |
|
|
|
|
|
|
|
|
|
loss (dB) |
10 |
|
|
|
|
|
|
|
|
|
20 |
|
|
|
|
|
|
|
|
|
|
Return |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
N = 1 |
|
|
|
|
|
|
|
|
|
|
N = 2 |
|
|
30 |
|
|
|
|
|
|
|
N = 3 |
|
|
|
|
|
|
|
|
|
|
|
||
|
|
|
|
|
|
|
|
|
N = 4 |
|
|
|
|
|
|
|
|
|
|
N = 5 |
|
|
40 |
|
|
|
|
|
|
|
N = 6 |
|
|
3 |
4 |
5 |
6 |
7 |
8 |
9 |
10 |
11 |
|
|
2 |
Frequency (GHz)
Figure 8.57 Simulated return loss of the antenna with different N ([35], copyright C 2008 IEEE).
= 20 mm, W = 46 mm, and L = 50 mm. With these parameters, the widest 10-dB return loss bandwidth obtained by simulation was from 2.7 GHz to 11 GHz, while from 2.59 to 10.97 GHz by measurement. Simulated return loss is shown in Figure 8.57. The measured peak (average) gain for the frequencies 3.1, 5.0, and 8.0 GHz, respectively, are –0.88 (–3.65), –2.36 (4.51), and 1.54 (–2.1) (all in dBi).