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

Outline1. Introduction2. Segmentation and E-M simulations3. Examples

- 13 GHz and 15 GHz diplexers - filter and 26 GHz filter- filters for DBS Block Up Converters- combline X-band filter

4. Conclusions

•Application - low cost digital radio links.

•Highly competitive market.

•Low cost productsrectangular waveguide technology

•quick design and manufacturing cycle

accurate 3D electromagnetic simulation accurate CNC machining

•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.

•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.

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.

T junction Filter 2Filter 1SMAtoWG

SMAtoWGLow-pass

filter

•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.

Library of UDO objects as shown below two resonator asymmetric inductive iris coupled filter with rounded corners is used in design and optimization.

13 GHz diplexer with metal post inside cavities, integrated low-pass filter and WR to SMA transitions

Measured RL characteristic of the 15 GHz diplexer (no tuning).

Measured characteristics of the lower channel.

Measured characteristics of the upper channel.

n=5, f0=26 GHz

Measured

characteristics(without tuning).

n=5, f0=26 GHz

Measuredcharacteristics(after tuning).

n=5, f0=26 GHz, asymmetric inductive iris coupled filter with integrated waveguide bends

Initial characteristic of the 18 GHz (WR62) seven resonator filter

Tuned characteristics of the 18 GHz (WR62) seven resonator filter

18 GHz (WR62) seven resonator filter

Initial characteristic of the 14 GHz (WR75) five resonator filter

Tuned characteristic of the 14 GHz (WR75) five resonator filter

14 GHz (WR75) five resonator filter

9 90 0 1 000 0 1 010 0 1 020 0 1 030 0 1 040 0 1 050 0 1 060 0 1 070 0

frequency /M H z

-8 0

-7 0

-6 0

-5 0

-4 0

-3 0

-2 0

-1 0

0

s11

a

nd

s2

1

/d

BX-band comb-line resonator filter with step-impedance resonators. Measured (continuous lines) and simulated (dashed lines) results.

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.