Robert Walter Schlub

Seven-element ground skirt monopole ESPAR antenna design from a genetic algorithm and the finite element method

The design of an optimized electronically steerable passive array radiator (ESPAR) antenna is presented. A genetic algorithm using a finite element based cost function optimized the antennas structure and loading conditions for maximal main lobe gain in a single azimuth direction. Simulated gain results of 7.3 dBi at 2.4 GHz were attained along the antennas elemental axis. The optimized antenna was fabricated and tested with the corresponding experimental gain better than 8 dBi. The 0.7 dB error between simulated and measured gain was constant for numerous structures and therefore did not affect the optimization. The optimized antenna reduced average main lobe elevation by 15.3/spl deg/ to just 9.7/spl deg/ above the horizontal.

Dielectric embedded ESPAR (DE-ESPAR) antenna array for wireless communications

A novel dielectric embedded electronically steerable passive array radiator (ESPAR) (DE-ESPAR) antenna array for mobile wireless communication terminal is developed by finite element method based numerical modeling technique. The size reduction of the seven-element monopole antenna was accomplished by embedding the array in a cylindrical rod of FIK ceramic complex with a relative permittivity around /spl epsiv//sub r/=4.5. Dielectric embedded prototypes of a seven-element ESPAR antenna array were modeled and experimentally characterized. Experimental and numerical results are in good agreement. The optimized antenna produced a horizontal directivity of 5.1 dBi and return loss of 19 dB at 2.48 GHz. An overall volume reduction of 80% and footprint reduction of 50% were achieved.

Switched parasitic antenna on a finite ground plane with conductive sleeve

A switched parasitic monopole antenna on a finite ground structure with a conductive sleeve attached to a small, circular ground plane controls the vertical radiation direction. The antenna was designed using a genetic algorithm and finite element (FEM) solver. At 1.575 GHz, the constructed antenna exhibited a front to back ratio of 10.7 dB and gain of 6.4 dBi with no elevation from the horizontal. The switched parasitic nature of the antenna allowed it to steer a directional beam through 5 locations in the azimuth. Incremented from 0/spl lambda/ to 0.45/spl lambda/, the sleeve was observed to linearly depress the main lobe elevation with little influence on other antenna characteristics such as gain and S/sub 11/.

A Multi-Band Hybrid Balanced Antenna

The design of antennas for small user equipment has for many years relied on the use of unbalanced designs – usually ingenious variants of monopoles and inverted-L antennas. As the size of the equipment is reduced, unbalanced antennas become increasingly problematical because their input impedance and radiation properties become strongly dependent on the size of the groundplane and their position on it.

Dual band switched-parasitic wire antennas for communications and direction finding

Wire dipole and monopole switched-parasitic antennas have been designed to operate at 900 and 1900 MHz simultaneously. The array consists of a centre driven element circled by four parasitic elements symmetrically arranged. DC levels applied to p.i.n. diodes on each parasitic element allow full 360 degree coverage in the horizontal plane. The design of the antenna was undertaken using the genetic algorithm technique with the NEC2 solver. The design was optimised for element spacing and lumped impedance size and position. The cost function included the input impedance and directional characteristics at both frequencies. The final design has a front to back ratio of approximately 15 dB, S/sub 11/ less than -35 dB and 360 degree coverage of within 1.5 dB of the main lobe gain for both frequencies.

Frequency characteristics of the ESPAR antenna

Simulation results showing the frequency characteristics and radiation patterns of the electronically steerable passive array radiator (ESPAR) antenna are presented. Three software packages (NEC2, HFSS and XFDTD) were used to obtain the results. Five different loading cases optimised at 2.4 GHz provided main lobe direction ranging between 0/spl deg/ and 360/spl deg/ azimuth. All five cases had minimum S/sub 11/ values between 2.35 GHz and 2.4 GHz resulting in a resonant frequency variation of 2.2%. S/sub 11/ response was found to be better than -9 dB in all cases, with 4 cases exhibiting results better than -11.90 dB. -10 dB S/sub 11/ bandwidths in these cases were greater than 200 MHz. Highest gain variations in the H field between the cases was 1.5 dB, with maximum gain values ranging from 4.46 dBi to 5.99 dBi. Gain variation 100 MHz either side of resonance was smaller than 0.44 dB. Radiation patterns taken over the 200 MHz (8.4%) bandwidth were only slightly different from the resonant patterns.

Development of ESPAR antenna array using numerical modelling techniques

The work presents three configurations of an electronically steerable passive array radiator (ESPAR) antenna and their design topologies based on computer modelling techniques. Three different structures of ESPAR antenna arrays, such as wire ESPAR antenna, patch ESPAR antenna and DE-ESPAR (dielectric embedded ESPAR) arrays and their performances are discussed. The paper also discusses the optimal design techniques in ESPAR antenna development.

A performance comparison of smart antenna technology for wireless mobile computing terminals

The paper introduces two newly developed smart antennas, the ESPAR antenna and the ESMB antenna, for mobile wireless computing terminals and mobile stations. The configurations of these smart mobile terminal antennas at the operating frequency approximately over 2.4 GHz are illustrated and the applications of using these smart antennas at mobile computing terminals and mobile stations are proposed. The performance comparison of these smart antennas and the beam control circuits, and the beam-forming and selection algorithm is discussed.