Accurate 3D EM simulations and precision machining for low cost microwave

1

• Accurate 3D EM simulations and precision
  machining for low cost microwave
• and millimeter wave filters/diplexers
• Adam Abramowicz, Maciej Znojkiewicz
• QWED, Poland
• MWTG Telecom, Canada

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• Outline
• 1. Introduction
• 2. Segmentation and E-M simulations
• 3. Examples
• - 13 GHz and 15 GHz diplexers
• - filter and 26 GHz filter
• - filters for DBS Block Up Converters
• - combline X-band filter
• 4. Conclusions

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• Application - low cost digital radio links.
• Highly competitive market.
• Low cost products
• rectangular waveguide technology
• quick design and manufacturing cycle
• accurate 3D electromagnetic simulation
• accurate CNC machining

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• CNC vertical milling machines 40 microns
  accuracy
• internal rounded corners in E- and/or H- plane
• 40 micron accuracy translates to 140 MHz
  frequency accuracy of a cavity resonator at 40
  GHz.
• Center frequency drift of a 40 GHz filter is
  0.96 MHz/C
• Design is a careful tradeoff between performance
  and cost
• Performance margins are needed to guarantee
  manufacturability and tunability.

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• Fast, accurate and flexible design and
  optimization of waveguide components.
• Cross-sections of arbitrary shape such as
• filters, T-junctions, bends, lateral coax feeds
• 3D FDTD analysis (QuickWave)
• S-parameter matrices are used in circuit
  simulator to optimize the relative position of
  the elements.
• The advantage is mainly in shorter design time.

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• A diplexer with two asymmetric inductive iris
  coupled filters with integrated SMA-WR
  transitions and including an additional waveguide
  low pass filter is divided into two bandpass
  filters and two identical SMA-WR transitions, a
  waveguide low pass filter and a waveguide
  T-junction.

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• 16 times bigger memory and 64 times longer time
  to compute the characteristics of the complete
  diplexer is needed in comparison with the filter
  only.
• QuickWave 3D
• - accuracy,
• - speed,
• - possible optimization using parametrized
  objects library - moderate price.

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Library of UDO objects as shown below two
resonator asymmetric inductive iris coupled
filter with rounded corners is used in design and
optimization.
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13 GHz diplexer with metal post inside cavities,
integrated low-pass filter and WR to SMA
transitions
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• Measured RL characteristic of the 15 GHz diplexer
  (no tuning).

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• Measured characteristics of the lower channel.

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• Measured characteristics of the upper channel.

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• n5, f026 GHz
• Measured characteristics
• (without tuning).

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• n5, f026 GHz
• Measured
• characteristics
• (after tuning).

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n5, f026 GHz, asymmetric inductive iris coupled
filter with integrated waveguide bends
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Initial characteristic of the 18 GHz (WR62) seven
resonator filter
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Tuned characteristics of the 18 GHz (WR62) seven
resonator filter
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18 GHz (WR62) seven resonator filter
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Initial characteristic of the 14 GHz (WR75) five
resonator filter
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Tuned characteristic of the 14 GHz (WR75) five
resonator filter
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14 GHz (WR75) five resonator filter
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X-band comb-line resonator filter with
step-impedance resonators. Measured (continuous
lines) and simulated (dashed lines) results.
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• CONCLUSIONS
• examples of the design and realization of X, K
  and Ka band filters and diplexers have been
  presented,
• the design method is based on the 3D
  electromagnetic simulations combined with the
  circuit simulations,
• 3D simulations take into account effects
  resulting from CNC fabrication like rounded
  corners of resonators,
• realizations of the filters and diplexers
  justify the described approach and efficiency of
  QuickWave 3D.