Re: Help: how to design air-core transformer?

From: Jim (jmgong74_at_tom.com)
Date: 11/23/04 

Date: 23 Nov 2004 09:53:58 -0800

legg <legg@nospam.magma.ca> wrote in message news:<n076q0l32ektjtrb9fq93mkvkk2ish00oc@4ax.com>...
> On 22 Nov 2004 15:08:36 -0800, jmgong74@tom.com (Jim) wrote:
>
> >I hope to design an air-core transformer which may operate at 100-500 MHz.
> >However I found the loss is too high.
> >Can anybody give me some advices to design air-core transformer?
> >Thanks a million!
>
> What is your loss like WITH a core? Maybe the core is not your
> problem. What application/environment?
>
> Google 'air-core transformer', 'air cored transformer', 'coreless
> transformer', 'contact-free transmission', 'contactless transmission',
> 'transcutaneous energy' etc.
>
> RL
I observed two unwanted phenomenon:

1. direct capacitive coupling between primary/secondary coils. It
interferes with the mutual inductance, and makes the transmissivity of
the transformer change significantly with frequency.

2. Insertion loss is higher than 10dB.

I googled air core transformer before i posted my question. It is
weird that the concept is mentioned in many places, but I can never
find a real one which works in VHF/UFH band except transmission-line
type.

My purpose is for impediance matching, from 50 ohm cable to a 0.5 ohm
load.

To my understanding, air-core transmission-line transformers have
fixed conversion ratio, e.g. 1:1, 4:1 or 1:4, is it right? What i need
is a ratio of 10:1.

I saw some companies provide RF transformer with ferrite coil inside.
The insertion loss is only 1-2dB, however, for UHF band, the maximum
ratio is 4:1 or 6:1 only.

Thank you all again! And hope to hear from you again.

Relevant Pages

  • Re: Help: how to design air-core transformer?
    ... >> What is your loss like WITH a core? ... Insertion loss is higher than 10dB. ... >I googled air core transformer before i posted my question. ... The old Motorola App Note AN1304 discusses the use of coaxial baluns ...
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  • Re: Help: how to design air-core transformer?
    ... >> What is your loss like WITH a core? ... Insertion loss is higher than 10dB. ... >I googled air core transformer before i posted my question. ... The old Motorola App Note AN1304 discusses the use of coaxial baluns ...
    (sci.electronics.components)
  • Re: Help: how to design air-core transformer?
    ... >>However I found the loss is too high. ... > What is your loss like WITH a core? ... I googled air core transformer before i posted my question. ... To my understanding, air-core transmission-line transformers have ...
    (sci.electronics.design)
  • Re: Help: how to design air-core transformer?
    ... >> What is your loss like WITH a core? ... Insertion loss is higher than 10dB. ... >I googled air core transformer before i posted my question. ... >is a ratio of 10:1. ...
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