billykao wrote:>> On May 14, 8:42 pm, cincy...@gmail.com wrote: >> >>> You should be fine, assuming that the signal you sampled is >>> appropriately bandlimited (i.e. you should bandpass filter the 55-85 >>> MHz band before sampling). Your sampling frequency is 100 MHz, so the >>> signal of interest will "alias" down to a center frequency of 30 MHz >>> after sampling. Your signal will then occupy the 15-45 MHz band in the >>> sampled signal, which is all below the Nyquist rate. No problems >>> there. >>> >>> Jason >> To the original poster: the keyword is "bandpass sampling". >> >> > > For 30 MHz I signal, the maximum available bandwidth is 15 MHz. So is Q > signal. If using I and Q, can I make it 30 MHz bandwidth? Thank you.Yes. In that special case, you may add. Jerry -- Engineering is the art of making what you want from things you can get. ¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯
Bandwidth of complex IQ signals
Started by ●May 14, 2007
Reply by ●May 15, 20072007-05-15
Reply by ●May 15, 20072007-05-15
billykao wrote:>> "billykao" <billy.kao@gmail.com> writes: >> >>>> On May 14, 8:42 pm, cincy...@gmail.com wrote: >>>> >>>>> You should be fine, assuming that the signal you sampled is >>>>> appropriately bandlimited (i.e. you should bandpass filter the 55-85 >>>>> MHz band before sampling). Your sampling frequency is 100 MHz, so > the >>>>> signal of interest will "alias" down to a center frequency of 30 MHz >>>>> after sampling. Your signal will then occupy the 15-45 MHz band in > the >>>>> sampled signal, which is all below the Nyquist rate. No problems >>>>> there. >>>>> >>>>> Jason >>>> To the original poster: the keyword is "bandpass sampling". >>>> >>>> >>> For 30 MHz I signal, the maximum available bandwidth is 15 MHz. So is > Q >>> signal. If using I and Q, can I make it 30 MHz bandwidth? Thank you. >> Yes. You essentially utilize the bandwidth in -Fs/2 to +Fs/2 with an >> I/Q signal, whereas with a real signal the usable bandwidth is from 0 >> to +Fs/2. >> -- >> % Randy Yates % "And all that I can do >> %% Fuquay-Varina, NC % is say I'm sorry, >> %%% 919-577-9882 % that's the way it goes..." >> %%%% <yates@ieee.org> % Getting To The Point', *Balance of > Power*, ELO >> http://home.earthlink.net/~yatescr >> > > I appreciate your answer. Could you explain why Q signal shows bandwidth > from -Fs/2 to 0?It doesn't. The two together give you the higher bandwidth.> Is there any article or book talking about this? Thank > you very much.Most books on sampling will explain. I like Richard Lyons: "Understanding Digital Signal Processing" for a serious introduction. (Rick is a comp.dsp regular. Beiefly, the I and Q samples are independent. 30,000 I samples/sec and 30,000 Q samples/sec together provide 60,000 samples/sec. That's (barely!) adequate for a 30 KHz bandwidth. Jerry -- Engineering is the art of making what you want from things you can get. ¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯
