Generating High Frequency Signals

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Discussion Overview

The discussion revolves around methods for generating high-frequency signals in the range of 700 MHz to 30 GHz, with considerations for circuit design, antenna length, and regulatory requirements. Participants explore the challenges of signal generation and handling, as well as the implications of electromagnetic shielding in testing environments.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Experimental/applied

Main Points Raised

  • Some participants inquire about the best methods for generating high-frequency signals, questioning whether circuit diagrams or processors are preferable.
  • There is a suggestion that the length of the antenna, specifically dipole antennas, may significantly influence signal generation.
  • One participant emphasizes the importance of transmission line theory for successfully connecting to the signal generator.
  • Another participant mentions the need for a license to transmit in certain frequency bands, raising concerns about regulatory compliance.
  • A participant describes a project involving an electromagnetic shield within a Faraday cage, aiming to block higher frequencies and verifying impedance through testing.
  • There is a discussion about the feasibility of generating random noise signals at around 1000 MHz and whether this is easier to build.
  • One participant references an industry standard test for Radiated RF Immunity and suggests using local EMC test labs for testing rather than renting expensive equipment.
  • Questions arise regarding testing frequencies around 100 MHz and the associated power output limits, with some participants noting that 1 watt may exceed allowable limits for many bands.
  • Concerns are raised about the need for a well-shielded room for conducting immunity testing independently.

Areas of Agreement / Disagreement

Participants express varying opinions on the best methods for signal generation and the regulatory aspects of testing. There is no consensus on a single approach or solution, and multiple competing views remain regarding the technical requirements and feasibility of the proposed designs.

Contextual Notes

Participants highlight limitations related to regulatory compliance, the need for specific testing environments, and the complexity of achieving desired signal characteristics. The discussion reflects uncertainty about the best practices for generating and testing high-frequency signals.

amanno
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What is the best way to generate a signal with a high frequency (700 MHz - 30 GHz)?

Is there a preferred circuit diagram for such a design, or is it better to use a processor of some kind?
Is it really heavily based on the length of the antenna (dipole)?

I am trying to do it as cheap as possible but I am not sure if that is very possible.

Thanks in advanced for any ideas.
 
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Is it really heavily based on the length of the antenna (dipole)?

Generating the signal is not really the problem.

Handling it ie successfully connecting to generator and using it is the really difficult part.

You need a good working knowledge of transmission line theory to do this and I worry from the above question.

How would you know if you have achieved your objective?
 
amanno said:
What is the best way to generate a signal with a high frequency (700 MHz - 30 GHz)?

Is there a preferred circuit diagram for such a design, or is it better to use a processor of some kind?
Is it really heavily based on the length of the antenna (dipole)?

I am trying to do it as cheap as possible but I am not sure if that is very possible.

Thanks in advanced for any ideas.

What frequency band do you want to transmit in? Do you have a license to transmit in that band?
 
Well actually the main design is an electromagnetic shield. We have an circuit inside a faraday cage and want to make sure it reflects/blocks higher frequencies (700MHz - 30 GHz). We have the impedance of the box as low as we can but we need to verify with actual testing.

It is a small scale low power test (or will be) so I am hoping a license would not be needed.

The signal can be just random noise just need it to be about 1000 MHz.

Is what I am asking possible or "easier" to build?

Thanks again
 
amanno said:
Well actually the main design is an electromagnetic shield. We have an circuit inside a faraday cage and want to make sure it reflects/blocks higher frequencies (700MHz - 30 GHz). We have the impedance of the box as low as we can but we need to verify with actual testing.

It is a small scale low power test (or will be) so I am hoping a license would not be needed.

The signal can be just random noise just need it to be about 1000 MHz.

Is what I am asking possible or "easier" to build?

Thanks again

There is an industry standard test for Radiated RF Immunity -- EN 61000-4-3

http://www.teseq.com/com/en/products_solutions/systems/commercial/EN_61000-4-3.php

The test is conducted inside an anechoic chamber to keep the test signals from violating FCC rules. If you have your own shielded room, you could potentially do a similar test, but renting the test equipment would be more expensive than going to your local EMC test lab and renting some "engineering test" time.

Google for "EMC Test Lab" in your area, and give them a call to get a quote. That would be my recommendation. I've spent a *LOT* of time in such labs, testing and improving products that I have been on the design teams for.
 
Okay great thank you, I will look into one around us, that sounds like a convenient way to do the higher frequency testing.

What if I want to test for frequencies around 100 MHz? I can do that without violating FCC rules as long as I keep the power output below 1 watt correct?

What is the best circuit to use for that kind of a signal output? Again it can be just random noise.
 
amanno said:
Okay great thank you, I will look into one around us, that sounds like a convenient way to do the higher frequency testing.

What if I want to test for frequencies around 100 MHz? I can do that without violating FCC rules as long as I keep the power output below 1 watt correct?

What is the best circuit to use for that kind of a signal output? Again it can be just random noise.

The allowed unlicensed power levels vary with the band, but 1W is much too high for most bands. Up in the microwave oven band (WiFi around 2.4GHz), the power limits are relaxed, but for most other bands that I'm aware of the power limits are quite low unless you are licensed for that band.

You would need some sort of well-shielded room or chamber in order to do any immunity testing on your own.

http://www.ets-lindgren.com/EMCTestEnclosures

.
 

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