Grounding Considerations for Portable Radio Devices

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Discussion Overview

The discussion revolves around grounding considerations for portable radio devices, particularly focusing on the challenges of grounding in wireless applications. Participants explore various approaches to grounding for integrated circuits (ICs) and antennas, considering the implications of different circuit designs and antenna types.

Discussion Character

  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant inquires about alternatives to traditional grounding methods for a wireless device, seeking a circuit solution that could simulate a ground.
  • Another participant explains that "ground" can refer to a common reference point in circuits, emphasizing that in portable applications, a metal area for bypassing does not need to connect to actual ground.
  • A participant clarifies that for radio devices, the grounding requirements may differ based on the antenna type and frequency, questioning whether the ground for the antenna should be set up differently than for the ICs.
  • It is noted that for balanced antennas, a ground may not be necessary, while for quarter wavelength antennas, a proper ground connection or ground plane is crucial.
  • A warning is issued regarding legal considerations for using transmitters, suggesting obtaining a Ham Radio license for safe operation.

Areas of Agreement / Disagreement

Participants express differing views on the necessity and implementation of grounding for antennas versus ICs, indicating that multiple competing perspectives remain on the topic.

Contextual Notes

Participants discuss the implications of frequency and antenna type on grounding requirements, highlighting the need for careful consideration of circuit layout and grounding strategies without resolving the specific conditions under which each approach is applicable.

shazi
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Hi, Some of the ICs for a portable device I'm making need to be attached to ground. However, the device needs to be wireless so I can't ground it the way we usually do. Is there any way around this, such as a circuit that could somehow act as ground? Thanks.
 
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Unless it is a radio device where the real ground makes a difference, "ground" really just means that these points can be joined together or touched by humans without affecting the circuit operation (or the humans).

Normally, there will be a substantial area of metal which is used for bypassing purposes.
This may be an actual metal case or it may be a portion of a printed circuit board copper coating which has not been etched.
Incoming shielded cables would have their shield connected to this "ground" and pins of ICs etc that were marked as "ground" would be connected to this area as well.

Because the different areas of this ground have negligible resistance between them, they can be regarded as the same point for most circuits. For very high frequency circuits, the inductance beteen various points on the "ground plane" have to be allowed for in the circuit layout.

In portable applications such as battery operated equipment, this metal area does not have to be connected to the actual ground or even to a mains supply ground.

If the apparatus was mains powered, this metal case would have to be grounded in accordance with wiring regulations.
 
Actually it's a radio device. I'm going to get an oscillator and connect it to an antenna. Would the ground for the antenna need to be set up differently than the ground for the ICs?
 
Actually it's a radio device. I'm going to get an oscillator and connect it to an antenna. Would the ground for the antenna need to be set up differently than the ground for the ICs?

It depends on the frequency and type of antenna. If you have a balanced output going to a matched, balanced antenna, you don't need a ground. It would work OK anywhere.

If you have an antenna that is a quarter wavelength long, or less, then the ground connection is very important and an actual ground or a ground plane will make a big difference.
A ground plane is either a flat area of metal (like the roof of a car) or it can be some radial metal rods just below the antenna.
Like this:
120px-136_to_174_MHz_base_station_antennas.jpg



Most countries have fierce penalties for using transmitters illegally, so be warned. Don't do it.
Get a Ham Radio license and learn how to transmit safely and legally.
 

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