Hi Carrack Thank you for your valuable opinion. Since I am just a freshman in RF field, I am not familiar with HPF in baseband and image rejection correction in baseband. I am very intersted in both of them, especially the correction for image rejection (Did they control the IQ phase by baseband?)x. Can you kindly provid some relative paper, patent, or books for me? Recently I also face some problems of adjacent channel rejection ration due to insufficient image rejection ratio. In our case, the poly-phase filter can only provid 30 dB image rejection. I am wondering how can we improve it in baseband. Thank you for your reply. ※ 引述《carrack (.....)》之铭言： : Hey Lary thanks for your opinion! : Sorry I am not in Taiwan and need to use English typing sys. : Yes, I agree with you zero-IF has some DC issue compared with low-IF. : However, we are not necessary to use "physical" HPF to deal with that in : the industry. : Why I said maybe you are talking about zero-IF system is because of the : image rejection issue. : Because the image of zero/low-IF system is usually located in your own : application band, it is impossible to design a image rejection filter to : kill them. That's why we need image cancellation Mixer/sys. : Sure, as you said the mismatch of IQ path will degrade the image rejection, : if we don't do any correction I think maybe only ~ -40dB we can get in current : technology. : In heterodyne system, it is a different story. If we can choose the IF cleverly : then the image can be located some less interference band and we don't need : high rejection level. : Also, the IF selection will affect the channel filter and image(band) filter : design. In most cases, they are directly trade-off. : Anyway, really appreciate your idea and I agree with you direction conversion : type sys is the main-stream now and maybe IQ mismatch has more effect on the : image issue. : ※ 引述《Lary (PTTuser)》之铭言： : : 推 poppyya:嗯~ 谢谢各位^^ 114.46.113.58 09/11 00:27 : : → poppyya:再问一下喔~ IF 中频 要去哪里查? 114.46.113.58 09/11 00:31 : : → poppyya:我的意思是 如果我做2.4GHz的MIXER 那IF? 114.46.113.58 09/11 00:31 : : → poppyya:这要到哪里才查的到??? 谢谢了!! 114.46.113.58 09/11 00:32 : : → Lary:也许你应该先说你到底要做什麽样的系统? 123.195.2.141 09/11 00:38 : : → Lary:不同调变方式需要不同的频宽 这可能需要做 123.195.2.141 09/11 00:39 : : → Lary:system或baseband的人来订到底if的center 123.195.2.141 09/11 00:40 : : → Lary:freq. 和band width是多少 然後决定DAC到 123.195.2.141 09/11 00:41 : : → Lary:mixer间的LPF design 123.195.2.141 09/11 00:41 : : 推 Gocoba:不同的架构有不同的IF 同时也牵扯到Image 72.222.132.58 09/11 01:12 : : → Gocoba:rejection的问题 还有filter的设计 72.222.132.58 09/11 01:12 : : → Lary:image rejection感觉跟poly-phase filter 140.113.228.149 09/11 17:29 : : → Lary:以及LO的I-Q error比较有关系ㄟ... 140.113.228.149 09/11 17:30 : : 推 carrack:Lary, you are talking about zero-IF sys 63.239.159.137 09/11 23:44 : : → Lary:I am talking about low IF system 60.250.197.166 09/12 11:53 : : → Lary:I'm not sure if the mixer design is differ 60.250.197.166 09/12 12:02 : : → Lary:ent for zero-IF and low-IF. However, the 60.250.197.166 09/12 12:02 : : → Lary:difficult part of zero-IF design would be 60.250.197.166 09/12 12:03 : : → Lary:how to remove DC offset due to device mism 60.250.197.166 09/12 12:04 : : → Lary:atch or other factors without affecting th 60.250.197.166 09/12 12:04 : : → Lary:e wanted signal. A HPF with very low 3dB 60.250.197.166 09/12 12:05 : : → Lary:freq will need a large layout area and lon 60.250.197.166 09/12 12:06 : : → Lary:g stable time. I did not do it myself. 60.250.197.166 09/12 12:07 : : → Lary:I do not know it very well and we can 60.250.197.166 09/12 12:09 : : → Lary:discuss if you are interested. 60.250.197.166 09/12 12:09 --

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