Presently we are witnessing great efforts which aim at soaring the role of the antenna and relevant signal processing in the concepts of communication and radar systems. The interest in modern antenna technologies has been substantiated by the belief that the gains from new antenna concepts are likely to be most profitable, since well-organized spatial access to the radio channels competes successfully with many modern modulation and coding methods. Even though, techniques using space-time coding with multipathly propagating signals (e.g. MIMO) might need less focused radio wave transmission and reception, highly integrated antenna arrays are of great desire. These challenging tasks placed the antenna technique in the critical spot of the development of modern communication. Thus, the 'lagging behind' of the antenna designs exposes the launch of new systems to jeopardy.
In this monograph, we attempt to describe two evaluation methods developed in-house for the needs of the research on highly integrated lightweight antennas. With one of the methods it is possible to carry out simulations of highly integrated antennas made of composites or other dielectrics. The other method explores the near field of the antenna. The capabilities of both methods have been upgraded as compared to those described in the literature. In contrast to conventional measuring methods which provide overall data, it is expected that the considered evaluation methods will enable instant pointing of non-conforming elements. As in both methods use is made of indirect approach, comprehensive data processing or simulations must be performed in order to achieve interpretable results.
Spis treści:
Preface
1. DIAGNOSTICS OF ADVANCED ANTENNA ARRAYS
1.1. Introduction
1.2. Importance of measuring technologies in antenna engineering
1.3. Interdisciplinarity of modern diagnostics
1.4. Need for diagnosis of highly integrated arrays
1.5. Major advantages of near-field antenna measurements
1.6. Historical milestones
1.7. Outline of the presented research
2. HIGHLY INTEGRATED LIGHTWEIGTH ANTENNA ARRAYS
2.1. Increasing precision of beamforming in modem arrays
2.2. Technology of high-scale array integration invented in the framework of the author's research
2.3. Conformal integrated antennas
2.4. Antennas of future SAR radar
3. MULTI-ELEMENT ANTENNA ARRAYS FEATURING LOW-LOSS FEEDING SYSTEMS
3.1. Specifics of low-loss feeding systems
3.2. Radial line planar antennas
3.3. Spatial solid-state power combining
3.4. Inflatable lightweight arrays
4. TEMPERATURE-DEPENDENCE OF MICROSTRIP ANTENNA PERFORMANCE
4.1. Introduction
4.2. Temperature-related problems in integrated arrays
4.3. Effect of temperature on the microwave substrate properties
4.4. Performance of microstrip elements over large temperature ranges
4.5. Design guidelines
5. NEAR-FIELD BI-POLAR ANTENNA MEASUREMENTS
5.1. Scanning methods and major related problems
5.2. Other major types of near-field electromagnetic measurements
5.3. Advantages of the bi-polar scanning method
5.4. Conventional bi-polar grid
5.5. Bi-polar near-field systems: basic technical considerations
5.6. Scanner for the bi-polar system
5.7. Microwave equipment
5.8. Probes of electromagnetic field
5.9. Automatic data acquisition and system operation
5.10. Our bi-polar scanning system
5.11. Examples of recorded data
6. SPATIAL SAMPLING AND NEAR-FIELD DATA PROCESSING
6.1. Sampling criterion
6.2. Interpolation techniques
6.3. Fundamentals of near to far-field transform
6.4. Far-field transform computation in our laboratory
6.5. Thinning of the bi-polar sampling grid
6.6. Determination of polarization properties in far-field results
7. RADIATION PATTERN MEASUREMENTS
7.1. Probe used in the measurements
7.2. Probe corrected measurements
7.3. Polarization correction
7.4. Measurements of fixed beam arrays
7.5. Measurements of arrays with a scanned beam
7.6. Truncation error
8. MICROWAVE HOLOGRAPHY AT OUR LABORATORY
8.1. Microwave holography in the bi-polar method
8.2. Detection of blockages in the antenna aperture
8.3. Diagnostics of phased arrays
9. UPGRADE OF DIAGNOSTIC CAPABILITIES
9.1. Concurrent dual-method scanning
9.2. Mobility of the scanner - on-site antenna evaluation
9.3. Tests of small multiband terminal antennas
9.4. Fine alignment of antenna arrays
9.5. Time domain measurements in the near-field
10. SUMMARIZING COMMENTS
REFERENCES
