Attenuator impedance

[Deniz]

We have this setting:

...--(56ohm)----(47ohm)----(47ohm)----(RG58/U to spectrum analyzer)
| |
(3.3ohm) |
| ---
---

47ohm, 47ohm and grounded 3.3ohm resistors form the three resistor
attenuator.
Attenuator attenuates the circuit output delivered to 56ohm load. Now
what is the output impedance of attenuator?? and why? (asuming that
RG58/U coaxial cable has an impedance of 50ohm)

 

[Tom MacIntyre]

On 20 Nov 2004 12:24:33 -0800, daksoy@gmail.com (Deniz) wrote:

We have this setting:

..--(56ohm)----(47ohm)----(47ohm)----(RG58/U to spectrum analyzer)
| |
(3.3ohm) |
| ---
---

47ohm, 47ohm and grounded 3.3ohm resistors form the three resistor
attenuator.
Attenuator attenuates the circuit output delivered to 56ohm load. Now
what is the output impedance of attenuator?? and why? (asuming that
RG58/U coaxial cable has an impedance of 50ohm)

Is the 3.3 to ground between the two 47 ohm resistors or the 56 and
the first 47 ohm resistors?

Tom

 

[Spajky]

On 20 Nov 2004 12:24:33 -0800, daksoy@gmail.com (Deniz) wrote:

..--(56ohm)----(47ohm)----(47ohm)----(RG58/U to spectrum analyzer)
| |
(3.3ohm) |
| ---
---

47ohm, 47ohm and grounded 3.3ohm resistors form the three resistor
attenuator.
Attenuator attenuates the circuit output delivered to 56ohm load. Now
what is the output impedance of attenuator?? and why? (asuming that
RG58/U coaxial cable has an impedance of 50ohm)

this is a -36dB attenuator (T-type) schematics (with a Z transforming
2:1 too) with approx. 50 ohm output impedance. (& normally approx. 100
ohm input Z ). Since imedance of spectrum Anal. is 50 ohm & has
connected the last R of 47 ohm in series, its input gets -6dB signal
(half voltage of it= matching impedance) compared to the taken point
on 3,3 ohm resistor (-30dB); so on the Analizer you get of TL -36dB
attenuated signal (approx. only of 1/64 part of the voltage of main
input signal with 50ohm matched inpedance /Z/ with Spec.Anal.) ...

--
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& visit my site @ http://www.spajky.vze.com
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[Deniz]

Is the 3.3 to ground between the two 47 ohm resistors or the 56 and
the first 47 ohm resistors?

Tom

yes, 3.3 goes to ground btw the two 47 ohm resistors.