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:smile::smile:
The root cause is found, the reason is because LO has a spur at 400kHz offset, and the blocking signal is so strong, then is mix with spur and produce a 71MHz CW, it is cause the DC-offset, and has this phenomena.
to Baas Rietrot,
what't the meaning of "Floating DC point? Sounds like a large cap and resistor or something (RC constant). " could you please to give some clearly explaination? thanks very much, ^^.
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to Tony_lth
It have DC block cap for each port of mixer, and only...
Hi friends,
I meet a problem as title, could you please help to give me some ideas? :-?:-?
This issue is found in GSM base station radio board, the receiver architecture is two stage LNAs->RF filter->RF mixer->IF saw-> one chip (which include IF amplifier, I/Q modulator, and ADC)...
Hi,
For hybrid coupler, change the isolation port impedance will improve the input port impedance, how it come true? And, change the two output port phase will change the input port impedance in smith chart, how to analyse this? thanks.
cdma baseband filter bandwidth
Hi,
In the CDMA receiver, the input signal at antenna port is 1.23MHz, in case of use ZIF architecture, when downconverted the input signal, why the BB filter is 615kHz, I don't know where does the other half band signal power? and why the bandwidth of...
Hi,
Thank you for your reply, I study the interface between radio board and filter, I find the the coupler is integrate in the filter, and the SRX input is the PA output coupled signal.
TDU is the test and diagnostic unit, the 1960MHz tone is used to test antenna, but I don't know how...
Hi all,
At present, I study the CDMA base station radio board, which is the digital IF architecture, and used for PCS band, but I am confused many things, as following:
1) For TX output, I find the SRX signal is from the radio board TX output signal, SRX is used for pre-distortion. I think...
Khouly and vfone, thank you for your advice.
now, i do some experiments, and i found the problem was caused by the RX chipset, i changed the RX chipset, the sensitivity is ok, and i put the poor sensitivy rx chipset on a good board, the good board sensitivity is poor.
i don't RX chipset how to...
lna de-sensitivity
Hi all,
i want to know how to judge whether the LNA is self excitated?
I design the CDMA mobile phone, the sensitivity is very low in some channel, only -100dBm, and some channel is normal, about -108dBm, this is in B2, before B2 the sensitivity is very good...
rssi + rf
what about you RF system structure? and what about your gain control mechanism? you know, in CDMA ystem, before the digital modulation, the signal level is constant, and the control gian is know (this information is from the calibration, the calibration data is stored in the memory)...
microstrip patch antenna for mobiles
at present, some mobile phones use PIFA and some use monopole, because now many phones are small and thin, the PIFA antenna can not satisfy this requirement, so many thin moble phones use monopole antenna.
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