antenna design interview questions 5

[ac350]

Hey all,
I'm an RF/Microwave engineer, a recent grad., with very little antenna design exp. The only antenna design experience i have(if you can call it that) is feed network of phased arrays made up of phase shifters for X-band radar apps at my current position. I am interviewing for a microwave/antenna design position next week. They already know I am inexperienced per our phone interview, but I was just wondering if anyone had any tips on interview questions an employer might ask for this kind of position? I know its vague but I was just wondering what I should brush up on as 'basics' in the field since they know that I am a novice, but are expecting some knowledge. Thanks in advance for any help!
-AC

 

[biff44]

Having modest experience is not necessarily a drawback. There are probably few qualified applicants available, and you do have some hands on experience. I would probably ask questions like:

1) On your Xband feed network. How did the project go? What major hangups did you find, and who fixed them and how were they solved. How accurately did your predictive software mimic the actual performance. How did you package the design? What mechanical features did you include to make it reliable, producable, and able to withstand the environment. How did the feed network get fabricated, and how were you involved. What were the tricks in measuring the feed networks performance, and what type of requirment and accuracy were you trying to measure to.

2) What software products are you familiar with in the Microwave/Antenna area? Which is your favorite? How do you know the software is accurately predicting behavior? How can you tell when the software is lying?

3) What sort of hobbies, passtimes, or other activities do you do that show your creativity and interests?

4) Being a hard case, I would probably also ask a few specific emag theory or Sparameter design questions, just to see if you remember anything from your college courses. The more ways you could explain the answer, equations, smith charts, intuition, etc. the more I would be impressed.

 

[biff44]

Also, back in college, what type of electronic design projects did you do? You should be able to describe at least two in great detail. They can even be lab assignments, if that is all you have. Just be able to show that you really understood the nuances of what was going on.

 

[ac350]

Thanks biff44. I will definitely review this material. My brain is already churning with some of the suggestions you made. I actually have been reviewing my e-mag and microwave eng. textbooks from school, but how much attention should I use on the detailed math? I have been reviewing Maxwell's eq's- do you know of any sources or sites that could help me understand these 'basic' concepts a little easier and allow me to describe things in an interview type setting? Easier said than done right? I appreciate all of your help, thanks again!
-AC

 

[biff44]

Depends on the job. If it is a design engineer's job, the math is less important than knowing where to find it and how to use the canned software programs. Design managers want to know if you can produce stuff, they don't care how you do that. You can invent it, steal it, find it on the web, just as long as products come out of the lab on time, at budget, and producable. So impressing them with your memory of obscure math is not really what they want to hear. They want to know if you can "walk the walk".

If it is a teaching assignment, they will be all over the math.

 

[ac350]

THANKS! Youre the man biff

 

[IRstuff]

One thing that you probably should be able to produce at will is a link margin equation, e.g., how much received power you get for a given transmitter power. Antenna gain, transmission loss, etc.

TTFN

 

[Higgler]

Antenna design has changed alot in the past few years with the software packages like;
Ansoft HFSS ($40K)
IE3D ($35K)
Microwave Studio ($40K)

Research these three, plus NEC software program (it's a wire code and I think it's free) on the internet and ask the employer which one of these you have, mention that you have some familiarity with them and am looking forward to learning those in detail.

Ask them about their testing facilities. Look up antenna chamber types;
1) Standard Anechoic (big box with absorber, two antennas and a turntable)
2) Near Field Probe antenna range (a little probe that moves in X and Y over a plane, takes data, then patterns are calcuated)
3) Compact antenna range (large dish antenna with a feed antenna to radiate your unit under test).

Ask about prototyping capabilities, such as drawing tools
AutoCad
Solidworks
Corel Draw (can make .dxf files for artwork)

Know these items;
VSWR (unitless)
Return Loss (dB)
Gain (dBi, dBiL, dBiC)
Directivity (dB)
Polarization (linear and circular)
Radar Cross Section (RCS) dBsm, dB relative to square meter
Radar
Space loss (dB)
decibel (named after Alexander Graham Bell, who plotted things in Bells i.e. log format, then later someone said multiplying it by 10 is prettier for displaying data, hence deci Bell, and the abbreviation is dB, little d and large B.

Know connector types
SMA small
N large
TNC medium size

Know antenna types
Dipole
Monopole
Log Periodi
Yagi-Uda (although Uda did the work, his professor Yagi stole most of the credit, my antenna professor in 1979 said to pass the word, poor Mr. Uda).
Patch
Bicone (Monocone)
Notch
Horn
Reflector

Know the word Stealth and Low Observable(LO, pronounced ell owe) these are the same things. Ask if they have an RCS range

Inquire about etching capabilities too, if they make their own or go outside for etching and drilling.

I think that asking them questions about those capabilities would go a long way towards showing them you know what it takes to design and build antennas. I hope you read all the stuff on their website to know their products first.


Ask the interviewer what antennas they have designed.

Put in at least 10 hours on the internet and 10 hours reading the materials.

kch
sorry if I over did it
(antenna engineer and budding rock star golfer)

 

[sonvbui]

When I interview people for an antenna design position, I would ask them about the antenna specifications and how it apply to applications for which the design is for.
1. What is the relationship between the gain and beamwidth of an antenna? Why is a narrow beamwidth important for an X-band antenna for radar applications?
2. How is beam tilting achieved?
What is the advantages of electrical tilt over mechanical tilt?
3. What is the difference between dBd and dBi?
i.e., the microwave engineers typically use dBi while the wireless phone engineers use dBd.
4. How is IM controlled or prevented in the design of an antenna?
5. Name the technique for feeding an antenna. What are the advantages with each.

Etc...