### Author Topic: Antenna engineer interview questions  (Read 2492 times)

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#### PythonGuython

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##### Antenna engineer interview questions
« on: February 23, 2023, 03:44:11 am »
What technical questions would you ask when interviewing a recent graduate for an antenna engineering position?

#### coppercone2

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##### Re: Antenna engineer interview questions
« Reply #10 on: February 26, 2023, 04:50:40 am »

jon

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#### PythonGuython

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##### Re: Antenna engineer interview questions
« Reply #11 on: February 26, 2023, 11:13:30 am »
If you just calibrated your port, the smith chart should read along the resistive axis near the right side, near infinity.

How did I do? Am I missing practical effects - don't opens sometimes read slightly capacitive?

#### PythonGuython

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##### Re: Antenna engineer interview questions
« Reply #12 on: February 26, 2023, 11:21:49 am »

Quote
"You have an ideal, infinitely long transmission line of impedance Z0. At the end of the transmission line you have a voltage dependent voltage source. You can place any passive network you want between the transmission line and the voltage source. What network will provide the highest output power from the VDVS?" Once they answer that, add conditions: "How does your answer change if the transmission line is of finite length? Are there any lengths that require extra attention? How does that answer change if the transmission line has loss? Does this new answer depend on how much loss it has?"

Without setting up specific parameters of this problem, how would you reason about this? The only concepts that come to mind are opens and shorts can appear as inductive or capacitive depending on the length of the line relative to the wavelength, but I don't know how the VDVS affects that... Then the other concept is max power transfer when your source and load impedance are matched with the complex conjugate. What else am I missing?

#### PythonGuython

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##### Re: Antenna engineer interview questions
« Reply #13 on: February 26, 2023, 11:31:32 am »
I'm sorry can you explain the test more? What is the DUT here?

#### Bud

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##### Re: Antenna engineer interview questions
« Reply #14 on: February 26, 2023, 04:00:44 pm »
If you just calibrated your port, the smith chart should read along the resistive axis near the right side, near infinity.

How did I do? Am I missing practical effects - don't opens sometimes read slightly capacitive?
Not "slightly" capacitive to be pedantic, but exact capacitance of the Open standard which you entered in Cal Standards Coefficients settings of the VNA, if the VNA has that feature. If there is no calibration standards coefficients entry in the VNA, as it may be with cheap or some handheld models, the VNA assumes the Open standard is ideal with no capacitance, and will display the Open as a dot on the righthand side of the Smith chart R axis.

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#### TheUnnamedNewbie

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##### Re: Antenna engineer interview questions
« Reply #15 on: February 27, 2023, 03:36:13 pm »

Quote
"You have an ideal, infinitely long transmission line of impedance Z0. At the end of the transmission line you have a voltage dependent voltage source. You can place any passive network you want between the transmission line and the voltage source. What network will provide the highest output power from the VDVS?" Once they answer that, add conditions: "How does your answer change if the transmission line is of finite length? Are there any lengths that require extra attention? How does that answer change if the transmission line has loss? Does this new answer depend on how much loss it has?"

Without setting up specific parameters of this problem, how would you reason about this? The only concepts that come to mind are opens and shorts can appear as inductive or capacitive depending on the length of the line relative to the wavelength, but I don't know how the VDVS affects that... Then the other concept is max power transfer when your source and load impedance are matched with the complex conjugate. What else am I missing?

The entire point of this question isn't that there is a specific answer to this (I also just came up with this in a whim as example, I'm not saying I uses this a lot or anything). It's so the person I'm interviewing can reason and bounce ideas around what would impact this, etc. And there is the added trap that a rookie would just say 'a termination resistor equal to Zo', but that is not correct. For example, a transformer with ratio M and a termination of M^2*Zo would have M times higher voltage. And nothing stops you from taking that to the extreme with M->infinity.
The candidate might bring up reflections, or the fact that an open would give double the voltage.
« Last Edit: February 27, 2023, 03:40:34 pm by TheUnnamedNewbie »
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#### xabre77

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##### Re: Antenna engineer interview questions
« Reply #16 on: March 26, 2023, 06:12:31 pm »
First five from ChatGPT:

What is the role of impedance matching in antenna design?
What are the main factors that affect antenna gain and how are they related?
What is the difference between a directional and an omnidirectional antenna?
What is polarization in the context of antenna design and how is it determined?
How do you optimize the performance of an antenna in terms of efficiency, bandwidth, and radiation pattern?

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#### n4u

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##### Re: Antenna engineer interview questions
« Reply #17 on: March 26, 2023, 07:23:48 pm »
U should ask for somethink he needs in work. You didnt provided any information about software / hardware / types of antennas you are making / measures etc.
Let him make some measurement in VNA (with calibration) / spectrum analizer / ask him about S matrix / reflection coef / characteristics of standard antennas / matching circuits / let him make some sim / ask what he ever done / give him some impedance and let him match it using rg58 for some freq, then change the freq and ask him to make planar match / you maky ask about planar circuts /or antennas

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#### Joel_Dunsmore

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##### Re: Antenna engineer interview questions
« Reply #18 on: March 26, 2023, 10:50:49 pm »

#### tggzzz

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##### Re: Antenna engineer interview questions
« Reply #19 on: March 27, 2023, 08:16:44 am »
What technical questions would you ask when interviewing a recent graduate for an antenna engineering position?

If you don't know what questions to ask
• you probably don't know enough to be able to evaluate the answers
• you won't be able to formulate follow-up questions on the fly
There are lies, damned lies, statistics - and ADC/DAC specs.
Glider pilot's aphorism: "there is no substitute for span". Retort: "There is a substitute: skill+imagination. But you can buy span".
Having fun doing more, with less

#### pdenisowski

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##### Re: Antenna engineer interview questions
« Reply #20 on: March 27, 2023, 10:22:40 am »
As many others have said, designing antennas is part art, part science, and usually requires quite a bit of experience and equipment to do properly.  I wouldn't expect many new grads to have much of either.

What I would expect of a new grad interested in an antenna design position are things like:

- How to use / read a Smith chart
- How to make basic antenna measurements using a VNA
- Familiarity with some kind of modeling tool
- Some experience with matching / tuning networks
- Knowledge of basic antenna types and concepts (dipole, Yagi, LP, relationship between beamwidth, bandwidth, phasing of multiple antennas, effect of environment on antennas)
- Basic antenna construction / prototyping techniques
- Ideally, a genuine interest in antenna design (i.e. someone who plays with antennas as a hobby, not just in classes / labs)

#### n4u

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##### Re: Antenna engineer interview questions
« Reply #21 on: March 27, 2023, 10:26:35 am »
what you can do with a meter of rg58 cable

#### Mr Simpleton

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##### Re: Antenna engineer interview questions
« Reply #22 on: March 27, 2023, 06:04:14 pm »
"Seriously Sir, are your name really Ant Luneburg? "

Smf