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vor 7 Jahren

9-2016

  • Text
  • Technik
  • Radio
  • Filter
  • Oszillatoren
  • Quarze
  • Emv
  • Messtechnik
  • Bauelemente
  • Antennen
  • Antenna
  • Frequency
  • Wireless
Fachzeitschrift für Hochfrequenz- und Mikrowellentechnik

RF & Wireless Figure 5:

RF & Wireless Figure 5: Spec sheet for the 10” form factor at low frequency Figure 4: Results using 12” tall form factor: UWB monopole (top) and asymmetric monopole (bottom) the size unless there was dramatic improvement in frequency coverage. A series of AntSyn evaluations were conducted to explore this design space. The final design was optimized to cover 325 MHz to 2.5 GHz and was 7.5” wide x 10” tall. What Antenna Types Work Best? (Initial spec sheet definition) The initial evaluation explored various antenna types to determine if any could perform as required at the low end Figure 6: Results for the 10” form factor at low frequency (300 MHz) of the frequency band while not exceeding the specified maximum form factor. Given the AntSyn user’s prior experience with antenna design, a select set of antenna types of interest was specified as a starting point for the optimization, rather than allowing AntSyn to automatically select antenna types. The 30 hf-praxis 9/2016

RF Components & Wireless Figure 7: Spec sheet settings for UWB dipole Figure 8: Dipole results Figure 9: Spec sheet for genetic dipole Figure 10: Best result for genetic dipole specification sheet for the initial evaluation is shown in Figure 1. AntSyn allows the user to specify a run quality (RQ) based on how much time and computation AntSyn will spend optimizing each design. AntSyn completes runs much faster at low RQ than it does at medium RQ, which in turn runs much faster than high RQ. However, the higher quality setting performs more computations, which often leads to better antenna performance required for difficult design challenges. For this initial evaluation, medium RQ was selected since the wide bandwidth and relatively small form factor made this specification more difficult, yet the limited number of antennas to screen would solve relatively quickly. High RQ was not selected because the primary purpose of the initial exploration was to become familiar with the problem quickly and not to create the final highest-performance design. The results of this initial evaluation for the various antenna types along with the quality of results (QoR) indicator (star rating system) are shown in Figure 2. The QoR provides a qualitative rating of how well each design performed compared with the entered specifications. The best of the results returned by AntSyn did not achieve the required return loss at 300 MHz. The voltage standing wave ratio (VSWR) exceeded 4.0 at 300 MHz, 1 GHz, and the middle frequencies, indicating more design effort and a possible trade off were required. Exploring the Effect of Aspect Ratio The designer then set up a new spec sheet to investigate the impact of the orientation of the antenna on performance. The overall dimensions were maintained, but now with a 7” hf-praxis 9/2016 31

hf-praxis

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