Design and analysis of antennas for an Automotive Collision Avoidance System using Antenna Magus and CST Microwave Studio

Transcription

1 Design and analysis of antennas for an Automotive Collision Avoidance System using Antenna Magus and CST Microwave Studio Brian Woods, Magus (Pty) Ltd

2 The design specification 3-zone side detection and blind spot detection (SDS and BSD) radar Flush-mounted with smallest possible footprint (110 x 60 mm) Similar systems use 3 bi-static RX/TX pairs (6 antennas) Ku-Band ( GHz) Specification based on: NHTSA, Automotive Collision Avoidance Systems (ACAS) Program Final Report, U.S. Dept. of Trans., NHTSA, 2000.

3 A solution

4 A solution Zone A Required Achieved Azimuth beamwidth 24 º º Squint angle -64 º º Azimuth sidelobe level -22 db -22 db

5 1. DESIGN 2. ANALYSIS Antenna analysis and design

6 1. DESIGN 2. ANALYSIS Antenna analysis and design Given a structure: with all the necessary details to build it determine it s characteristics and evaluate these characteristics in the light of a specific application (CEM and/or measurement)

7 1. DESIGN 2. ANALYSIS Antenna analysis and design Given an application: Given a structure: determine what antenna characteristics are required with all the necessary details to build it choose an antenna type that can achieve these properties calculate the dimensions of the antenna structure to do so determine it s characteristics and evaluate these characteristics in the light of a specific application (CEM and/or measurement)

8 1. DESIGN 2. ANALYSIS Antenna analysis and design Given an application: Given a structure: determine what antenna characteristics are required with all the necessary details to build it choose an antenna type that can achieve these properties calculate the dimensions of the antenna structure to do so determine it s characteristics and evaluate these characteristics in the light of a specific application (CEM and/or measurement) A design must be analysed to evaluate performance in its environment and refined till it works

9 A design specification 3-zone side detection and blind spot detection (SDS and BSD) radar Flush-mounted with smallest possible footprint (110 x 60 mm) Similar systems use 3 bi-static RX/TX pairs (6 antennas) Ku-Band ( GHz) Specification based on: NHTSA, Automotive Collision Avoidance Systems (ACAS) Program Final Report, U.S. Dept. of Trans., NHTSA, 2000.

10 Capturing the Specification (Properties) Qualitative: Captured as keywords Ku-band Not a broad bandwidth Low-profile Low-cost Compact? Micro-strip or slot structure? Maybe an array will be required?

11 Capturing the specification (Values) Quantitative: Captured as described values The operating frequency Geometry of the target zones (provides quantitative azimuth pattern cut requirements) Measurements of antennas used in similar systems available

12 Capturing the specification (Values from plots) Specification based on: NHTSA, Automotive Collision Avoidance Systems (ACAS) Program Final Report, U.S. Dept. of Trans., NHTSA, 2000.

13 Capturing the specification (Expanding values) RADIATION PATTERN PROPERTIES REQUIRED FOR COVERAGE OF EACH SDS/BSD ZONE Antenna properties Zone A Zone B Zone C Azimuth beamwidth 24 Degrees 26 Degrees 26 Degrees Squint angle -64 Degrees -30 Degrees 30 Degrees Azimuth sidelobe level -22 db -12 db -12 db Specification based on: NHTSA, Automotive Collision Avoidance Systems (ACAS) Program Final Report, U.S. Dept. of Trans., NHTSA, 2000.

14 Finding candidate antennas for a Specification In Find Mode, antennas are reordered based on keyword relevance Antenna Magus contains many antenna types (260+) Familiar/obvious suggestions (A) Unfamiliar/less-obvious choices (B, C and D) (A) (C) (B) (D)

15 Refining the antenna options Read information on some of the suggested antennas Ideas on how they could be used can quickly be generated. Poor options (for practical or other reasons) disqualified early The best solutions may be a combination of antennas

16 Refining the antenna options For our example: A rectangular patch array is the most obvious option A wire-grid array could work, but cannot be squinted sufficiently A practical option is a linear array of sub-arrays of series-fed patches or Franklin arrays (simple feed network)

17 Refining the antenna options For our example: A rectangular patch array is the most obvious option A wire-grid array could work, but cannot be squinted sufficiently A practical option is a linear array of sub-arrays of seriesfed patches or Franklin arrays (simple feed network)

18 Refining the antenna options For our example: A practical option is a linear array of sub-arrays of seriesfed patches or Franklin arrays (simple feed network)

19 Designing the sub-array elements + Smart Design suggests sensible values for unspecified properties (such as a substrate) This allows dimensions of any antenna to be computed for any set of specification values* Quick performance estimate analysis the design *Within ranges achievable for that antenna

20 Designing the sub-array elements + The design can quickly be refined Quick performance estimate confirms the design and provides a full 3D radiation pattern The sub-array elements are small enough

21 Layout of the arrays Antenna Magus synthesises ideal layouts based on the specification (squint angle and distribution to achieve the side-lobe level) The impact of the actual element radiation pattern was used in the array pattern synthesis. The layout was adjusted accordingly to correct for the sub-array patterns Zone A

22 Transferring designs to CST for installed analysis Models of the sub-array designs can be exported and opened in CST Antenna Magus The array layouts are exported from Antenna Magus in tsv format The layouts can be imported into CST using the Array Wizard macro or the new 2015 Array layout tool (drag-and-drop) The full array is then generated! Array design layout file (*.tsv) CST Microwave Studio Sub-array design CST Model file

23 Transferring designs to CST for installed analysis Zone A Zone B/C

24 Transferring designs to CST for installed analysis Required Achieved Azimuth beamwidth 24 º º Squint angle -64 º º Azimuth sidelobe level -22 db -22 db

25 A final solution Using Antenna Magus we have found a practical solution and have generated good CEM models of the design Is this the best solution? Could we do better? What if the parameters for the design change? Using Antenna Magus it is quick to repeat the process and consider other options or to change design choices that were made

26 Conclusion Antenna Magus helps experienced and in-experienced antenna designers understand and expand the design requirements for an application Familiar and unfamiliar antennas can be designed easily using Smart Design to help make good initial design choices Tools, such as the array layout tool can be used to consider additional design possibilities All designs are easily transferred to analysis tools for refinement and detailed integration studies Information regarding the whole design process is easily stored and can be accessed and modified