In this thesis a method to analyze antennas on board of complex bodies is presented. The Geometri... more In this thesis a method to analyze antennas on board of complex bodies is presented. The Geometrical Optics (GO) and Uniform Theory of Diffraction (UTD) have been used to analyze the effect of the structure in the radiation pattern of the antennas. The bodies are geometrically modelled by using NURBS (Non Uniform Rational B-Spline) surfaces. In addition to be accurate and efficient, the method is compatible with most of the modern CAGD (Computer Aided Geometric Design) available programs.
A low cost, high performance Gunn X Band oscillator for educational and research purposes has bee... more A low cost, high performance Gunn X Band oscillator for educational and research purposes has been developed. The cavity has been manufactured on standard waveguide WR90, with UBR100 flange, in order to make it compatible with the rest of waveguide circuitry available in a basic microwave laboratory. The ability to sweep the whole X Band (8- 12 GHz) with constant output power and low phase noise, added to its low cost makes this oscillator an interesting tool for users at any level.
A new set of pseudo-empirical equations are presented in order to simulate the optical and bias d... more A new set of pseudo-empirical equations are presented in order to simulate the optical and bias dependencies of GaAs MESFET junction capacitances, which is valid for the whole I-V plane. The variations induced in the small signal equivalent circuit by the optical illumination are extracted from on-wafer scattering parameter measurements. New linear and quasilogarithmic variations versus the incident optical power are shown for gate-to-drain and gate-to-source (Cgd and Cgs) capacitances. Furthermore, experimental results are in very good agreement with the simulated values for a wide range of optical power and bias conditions.
This paper shows a new and accurate electrical modelling technique for low cost active plastic mi... more This paper shows a new and accurate electrical modelling technique for low cost active plastic microwave encapsulated devices. The method employs analytically derived expressions, and is based on the analysis of measured S-parameters over an appropriate frequency range. The approach produces a good fit between measured and simulated S-parameters for plastic packaged devices, as demonstrated in the results for PHEMT devices up to 26.5GHz and for low-cost LNAs up to 6GHz.
The antenna radiates predominantly the E component of field with the cross polarization level bel... more The antenna radiates predominantly the E component of field with the cross polarization level below 13 dB. Next, radiation-pattern data are computed for the proposed feed. A half-wave dipole feed is also modeled for comparison. The parameters of the reflector are S ϭ 0.21, L ϭ 0.21, and ⌯ ϭ 0.65. Computed horizontal-plane (xy plane) patterns for both feeds are shown in Figure 3. It is clear that the front-to-back (F/B) ratio for the MLBT feed is better than the dipole feed. The directivity for the MLBT feed is 7.6 dBi, whereas that for the dipole feed is 6.9 dBi. The new feed results in some small cross polarization (suppressed below 18 dB). The second example given in Figure 4 has the same front-toback ratio for both feeds. To achieve this the height of the reflector, H is adjusted for each feed, and L is fixed. For the same F/B ratio, the reflector height for the MLBT feed is 34% shorter (H ϭ 0.65) than that for the dipole feed (H ϭ 0.98). The final model is generated by adjusting the length L and height H of the reflector for fixed F/B ratio, directivity, and beamwidth for both feeds. The pattern data for this case is shown in Figure 5. For fixed F/B ratio, directivity, and beamwidth of 15.5 dB, 7.6 dBi, and 100 o , the reflector dimension for the MLBT feed is 46% smaller than the dipole feed. The elevation-plane patterns for both feeds have been found to be almost identical. CONCLUSIONS A novel primary feed antenna is introduced for application with plane sheet metallic reflectors. Such a feed, when compared to a conventional half-wave dipole feed, can reduce the reflector dimension by almost half for fixed directivity, beamwidth, and front-to-back ratio. These antennas can also be used in conjunction with corner reflectors or other types of reflectors.
The main drawback of the coupled-mode method is the poor convergence and accuracy of the disconti... more The main drawback of the coupled-mode method is the poor convergence and accuracy of the discontinuous field components. The greater the discontinuity, the worse these problems become. This Letter presents an improvement of the method, allowing this ...
A low-cost, high-performance-band Gunn diode oscillator for educational and research purposes has... more A low-cost, high-performance-band Gunn diode oscillator for educational and research purposes has been developed. The cavities have been manufactured on a standard WR90 rectangular waveguide with UBR100 flange in order to make it compatible with the waveguide circuitry usually available in a basic microwave laboratory. The capability of sweeping the whole band at constant output power and low phase noise, as well as the low cost of its components, make this device suitable for users at any level. As an example of its many educational applications, a multiple frequency continuous-wave (MFCW) radar has been developed, and the results of the laboratory implementation are shown.
IEEE Transactions on Microwave Theory and Techniques, 2000
Numerical results obtained using a full-wave hybrid technique (comprising a new formulation of th... more Numerical results obtained using a full-wave hybrid technique (comprising a new formulation of the coupled-mode method and the mode-matching method) for treating 3-D isotropicchiral-material discontinuities in rectangular waveguides with perfect electrically conducting walls were compared with experimental data. For that purpose, samples of an isotropic chiral material were manufactured as composite materials. These samples were then fully characterized in the -band. The measured constitutive parameters were used in the full-wave hybrid technique to predict the scattering parameters of three different structures-each a waveguide filled partially with the isotropic chiral material. The scattering parameters were also measured. The predicted and measured scattering parameters were in reasonably good agreement.
In this thesis a method to analyze antennas on board of complex bodies is presented. The Geometri... more In this thesis a method to analyze antennas on board of complex bodies is presented. The Geometrical Optics (GO) and Uniform Theory of Diffraction (UTD) have been used to analyze the effect of the structure in the radiation pattern of the antennas. The bodies are geometrically modelled by using NURBS (Non Uniform Rational B-Spline) surfaces. In addition to be accurate and efficient, the method is compatible with most of the modern CAGD (Computer Aided Geometric Design) available programs.
A low cost, high performance Gunn X Band oscillator for educational and research purposes has bee... more A low cost, high performance Gunn X Band oscillator for educational and research purposes has been developed. The cavity has been manufactured on standard waveguide WR90, with UBR100 flange, in order to make it compatible with the rest of waveguide circuitry available in a basic microwave laboratory. The ability to sweep the whole X Band (8- 12 GHz) with constant output power and low phase noise, added to its low cost makes this oscillator an interesting tool for users at any level.
A new set of pseudo-empirical equations are presented in order to simulate the optical and bias d... more A new set of pseudo-empirical equations are presented in order to simulate the optical and bias dependencies of GaAs MESFET junction capacitances, which is valid for the whole I-V plane. The variations induced in the small signal equivalent circuit by the optical illumination are extracted from on-wafer scattering parameter measurements. New linear and quasilogarithmic variations versus the incident optical power are shown for gate-to-drain and gate-to-source (Cgd and Cgs) capacitances. Furthermore, experimental results are in very good agreement with the simulated values for a wide range of optical power and bias conditions.
This paper shows a new and accurate electrical modelling technique for low cost active plastic mi... more This paper shows a new and accurate electrical modelling technique for low cost active plastic microwave encapsulated devices. The method employs analytically derived expressions, and is based on the analysis of measured S-parameters over an appropriate frequency range. The approach produces a good fit between measured and simulated S-parameters for plastic packaged devices, as demonstrated in the results for PHEMT devices up to 26.5GHz and for low-cost LNAs up to 6GHz.
The antenna radiates predominantly the E component of field with the cross polarization level bel... more The antenna radiates predominantly the E component of field with the cross polarization level below 13 dB. Next, radiation-pattern data are computed for the proposed feed. A half-wave dipole feed is also modeled for comparison. The parameters of the reflector are S ϭ 0.21, L ϭ 0.21, and ⌯ ϭ 0.65. Computed horizontal-plane (xy plane) patterns for both feeds are shown in Figure 3. It is clear that the front-to-back (F/B) ratio for the MLBT feed is better than the dipole feed. The directivity for the MLBT feed is 7.6 dBi, whereas that for the dipole feed is 6.9 dBi. The new feed results in some small cross polarization (suppressed below 18 dB). The second example given in Figure 4 has the same front-toback ratio for both feeds. To achieve this the height of the reflector, H is adjusted for each feed, and L is fixed. For the same F/B ratio, the reflector height for the MLBT feed is 34% shorter (H ϭ 0.65) than that for the dipole feed (H ϭ 0.98). The final model is generated by adjusting the length L and height H of the reflector for fixed F/B ratio, directivity, and beamwidth for both feeds. The pattern data for this case is shown in Figure 5. For fixed F/B ratio, directivity, and beamwidth of 15.5 dB, 7.6 dBi, and 100 o , the reflector dimension for the MLBT feed is 46% smaller than the dipole feed. The elevation-plane patterns for both feeds have been found to be almost identical. CONCLUSIONS A novel primary feed antenna is introduced for application with plane sheet metallic reflectors. Such a feed, when compared to a conventional half-wave dipole feed, can reduce the reflector dimension by almost half for fixed directivity, beamwidth, and front-to-back ratio. These antennas can also be used in conjunction with corner reflectors or other types of reflectors.
The main drawback of the coupled-mode method is the poor convergence and accuracy of the disconti... more The main drawback of the coupled-mode method is the poor convergence and accuracy of the discontinuous field components. The greater the discontinuity, the worse these problems become. This Letter presents an improvement of the method, allowing this ...
A low-cost, high-performance-band Gunn diode oscillator for educational and research purposes has... more A low-cost, high-performance-band Gunn diode oscillator for educational and research purposes has been developed. The cavities have been manufactured on a standard WR90 rectangular waveguide with UBR100 flange in order to make it compatible with the waveguide circuitry usually available in a basic microwave laboratory. The capability of sweeping the whole band at constant output power and low phase noise, as well as the low cost of its components, make this device suitable for users at any level. As an example of its many educational applications, a multiple frequency continuous-wave (MFCW) radar has been developed, and the results of the laboratory implementation are shown.
IEEE Transactions on Microwave Theory and Techniques, 2000
Numerical results obtained using a full-wave hybrid technique (comprising a new formulation of th... more Numerical results obtained using a full-wave hybrid technique (comprising a new formulation of the coupled-mode method and the mode-matching method) for treating 3-D isotropicchiral-material discontinuities in rectangular waveguides with perfect electrically conducting walls were compared with experimental data. For that purpose, samples of an isotropic chiral material were manufactured as composite materials. These samples were then fully characterized in the -band. The measured constitutive parameters were used in the full-wave hybrid technique to predict the scattering parameters of three different structures-each a waveguide filled partially with the isotropic chiral material. The scattering parameters were also measured. The predicted and measured scattering parameters were in reasonably good agreement.
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Papers by Juan Ipiña