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winglj
Joined: 21 Feb 2005
Posts: 147
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 17 Jul 2008 18:38 phase array + frontend transceiver design |
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Hi, everyone. I just faced a problem about the phase array transceiver design.
Since the phase shifters are used in phase array, I believe they will introduce extra noise to the receiver. So should I put the LNAs before the phase shifters in the transceiver design? If so, how can I integrate the duplexers and PA in the phase array?
So I am wondering what is the typical configurations of the phase array + front-end transceiver design? Any references or information will be welcome.
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RF-OM
Joined: 03 Aug 2007
Posts: 608
Helped: 107
Location: The Earth
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| 18 Jul 2008 23:44 Re: phase array + frontend transceiver design |
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| If phase shifter have no resistive element it will not create additional noise. Reactive elements are noiseless.
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LE YAO
Joined: 15 Jul 2008
Posts: 18
Location: GuangDong,China
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| 19 Jul 2008 5:02 phase array + frontend transceiver design |
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Yeah,but if phase shifter affect impedance matching how to handle it?
Thank you in advance
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RF-OM
Joined: 03 Aug 2007
Posts: 608
Helped: 107
Location: The Earth
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| 19 Jul 2008 6:44 Re: phase array + frontend transceiver design |
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| Impedance mismatch is easy to count. Just convert return loss to mismatch loss and this loss will be count dB per dB for noise. For example S11=-10 dB corresponds to ML=0.46 dB and will increase the noise by 0.46 dB.
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winglj
Joined: 21 Feb 2005
Posts: 147
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| 21 Jul 2008 20:06 Re: phase array + frontend transceiver design |
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| Hi, RF-OM. Thanks for your reply. But generally speaking, the active phase shifter, such as CMOS or Ferroelectric phase shifters are both with resistive parts. So do we need to account this effects for noise consideration? I found many of the phase shifter datasheets do not contain noise figure, so I am just wondering whether I should characterize them by building the test-fixture.
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RF-OM
Joined: 03 Aug 2007
Posts: 608
Helped: 107
Location: The Earth
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| 21 Jul 2008 23:53 Re: phase array + frontend transceiver design |
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| If they produce noticeable noise you probably need to count it. But if they make very small noise comparable to noise already in the system it hardly will change the total SNR. CMOS is not my area of expertise, so I am not good person to ask. I can tell only how to count several independent noise sources: you need to count them one at a time leaving one on and replacing other with resistors. After you determine individual contribution from each of them you need to take superposition as we usually do for independent power sources.
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khouly
Joined: 20 Oct 2003
Posts: 2423
Helped: 331
Location: EGYPT
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| 22 Jul 2008 10:44 phase array + frontend transceiver design |
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i think if the phase shifter is passive and in 50 ohm system the NF is equals the loss in the shifter , if the loss 2 dB , then the NF will be 2 dB as well
then u can take it into account in the receiver NF calculation
khouly
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