rickleicn
Member level 1
in transmit path:I and Q signals are mixed with the same local oscillators(LO) which have a 90 degree phase shift.the combined sigals are transmitted in the air through antenna.
in receive path:the input signals is mixed with local oscillator signal at the carrier frequency in two forms,one is at an arbitrary zero phase,the other has a 90 degree phase shift,the composite input signal is thus broken into I,Q signals again.
question: is there any document or book which describe the above process in detail? is there any theory which supports that?
thank you in advance.
Added after 3 hours 56 minutes:
so modulation such as PSK,QAM in the transmit path can be divided into two amplifier modulation on two Orthogonal LO,and the demodulation in the receive path can be divided into two amplifier demodulation.is that right?
another question:
what's the relationship between PSK and FSK?from the equation:I* cos(ωt) + Q * sin (ωt),it can always be equal to A*sin(ωt+Φ),it is then a psk or QAM.so the modulated carrier's frequency is always a constant ω,so we need no bandwidth to transmit something,it seems un-reasonable,but i can not explain it.
can you help me on that?
in receive path:the input signals is mixed with local oscillator signal at the carrier frequency in two forms,one is at an arbitrary zero phase,the other has a 90 degree phase shift,the composite input signal is thus broken into I,Q signals again.
question: is there any document or book which describe the above process in detail? is there any theory which supports that?
thank you in advance.
Added after 3 hours 56 minutes:
so modulation such as PSK,QAM in the transmit path can be divided into two amplifier modulation on two Orthogonal LO,and the demodulation in the receive path can be divided into two amplifier demodulation.is that right?
another question:
what's the relationship between PSK and FSK?from the equation:I* cos(ωt) + Q * sin (ωt),it can always be equal to A*sin(ωt+Φ),it is then a psk or QAM.so the modulated carrier's frequency is always a constant ω,so we need no bandwidth to transmit something,it seems un-reasonable,but i can not explain it.
can you help me on that?