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maniana
Joined: 04 Sep 2006
Posts: 31
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 29 Apr 2009 15:32 wideband matching |
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Hi,
I have an LDMOS that has an output impedance of 15+j1.1 at 330MHz.
I have a big problem to match it in 280-350MHz band using two pi sections.
It tunes very shraply with only 5MHz bandwith.
1. Could anyone suggest a good matching network or suggest some readings with practical examples.
2. if i put a 15ohm port in AWR will the simulation be valid?
how to add a port in AWR that has complex impedance?
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29 Apr 2009 15:32 Ads |
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kezambo
Joined: 26 Mar 2009
Posts: 14
Location: UK
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05 May 2009 21:25 wide band match |
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Hi,
you can use HB1 tone load pull analysis using ads software to find the optimum impedance. then use smitch chart to design the matching network
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vfone
Joined: 10 Oct 2001
Posts: 2328
Helped: 327
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06 May 2009 8:34 wideband matching network |
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AWR is fine to find the matching network, with the condition to have the right model of the LDMOS transistor.
In AWR you have in General\Passive\Other various elements that simulate complex impedance, IMPED, LTUNER, etc.
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jayce3390
Joined: 22 May 2007
Posts: 219
Helped: 9
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06 May 2009 8:51 power amplifier wideband matching |
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some methods exist to enlarge the operating bandwidth, for exmaple you can add a R+C components between gate and drain. But at the beginning try to find a proper matching network able to match your circuit at your impedance.
But you need to get :
1 . Optimal impedance at 280MHz
2 . Optimal impedance at center frequency
3 . Optimal impedance at 350 MHz
You have to design your matching network using a set of 3 impedances to see if you are able to match the bandwidth.
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dream-cast
Joined: 02 Dec 2007
Posts: 10
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08 May 2009 6:10 wide band matching |
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| it is very hard
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maniana
Joined: 04 Sep 2006
Posts: 31
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14 May 2009 8:05 wideband matching power amplifier |
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I designed matching in a similar way to the circuit shown in the pic above.
at the output I have 2 pi sections (c10-Z9-c11) build from lumped elements.
Those 2 pi sections transform the optimum output impedance to 50 ohm.
So, if the matching is done by the pi sections, what is the L1 inductor for and how do you pick its value?
I know it provides Vdd, but its value is 55nH in the datasheet of the transistor, so it is not a choke.
I matched the device using 2 pi sections at the input and 2 sections at the output, but the bandwith is only 10MHz at 330MHz and there is plenty of resonances outside the band. in my case L1 is a large value choke.
What is the reason for L1 and how do you calculate it?
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