Kev sib txuas lus digital wireless: Txoj cai ua haujlwm ntawm IQ modulation

Kev sib txuas lus digital wireless: lub hauv paus ntsiab lus ua haujlwm ntawmKev hloov kho IQ
IQ modulation yog lub hauv paus ntawm ntau txoj kev modulation siab uas siv dav hauv LTE thiab WiFi teb, xws li BPSK, QPSK, QAM16, QAM64, QAM256, thiab lwm yam. Kev nkag siab txog lub hauv paus ntsiab lus ua haujlwm ntawm IQ modulation yog qhov tseem ceeb rau kev nkag siab zoo dua ntawm lub hauv paus OFDM kev siv mechanism hauv LTE thiab WiFi. Vim tias cov txheej txheem modulation siv rau txhua lub subcarrier ntawm OFDM tseem yog ntau yam QAM modulation txheej txheem raws li IQ modulation, thiab qhov tseem ceeb, kev siv OFDM yog superposition ntawm IQ modulation ntawm ntau lub orthogonal subcarriers.
Cov tswv yim ntawm I thiab Q hauv IQ modulation sib raug rau cov lus luv ntawm ob lo lus Askiv: Hauv Theem thiab Quadrature, feem. Tsuas yog hais los ntawm lub ntsiab lus tiag tiag, cov npe ntawm I thiab Q cov cim tsis muaj lub ntsiab lus. Dab tsi yog nyob rau hauv-theem? Dab tsi yog orthogonality? Dab tsi yog siv lub cim qhia los ua qhov siv los txiav txim siab hauv-theemthiab quadrature? Hauv kev siv tiag tiag, ib pawg ntawm cosine thiab sine nthwv dej ntawm tib lub zaus feem ntau yog siv ua cov cim I thiab Q. Yog li ntawd, lub cim cosine siv ua lub cim I yog qhov tseeb lub cim siv, uas yog qhov tseeb yog lub cim In Phase. Lub cim cosine uas yog 90 degrees tawm ntawm theem nrog lub cim I yog nws lub cim Quadrature. Yog li qhov kev nkag siab yooj yim tshaj plaws ntawm IQ modulation signals yog xav txog lub cim I ua lub cim cosine carrier, thiab lub cim Q ua lub cim sine carrier nrog qhov sib txawv ntawm 90 degrees ntawm lub cim I.

Qhov hu ua IQ modulation yog siv ib pawg ntawm I teeb liab, uas yog cosine teeb liab, thiab Q teeb liab, uas yog sine teeb liab (nrog qhov sib txawv ntawm 90 degrees thiab orthogonal rau ib leeg) ntawm tib zaus li cov neeg nqa khoom, kom tib lub sijhawm modulate ob lub teeb liab baseband rau ob tus neeg nqa khoom, thiab tom qab ntawd superimpose ob lub teeb liab modulated ua ke thiab xa lawv los ntawm RF circuit. Tom qab tau txais lub teeb liab zaus xov tooj cua, qhov kawg tau txais uaIQ demodulation. Thaum lub sijhawm IQ demodulation, vim tias ob lub carriers yog orthogonal rau ib leeg, ob lub baseband teeb liab tuaj yeem sib cais los ntawm cov teeb liab sib xyaw raws li I thiab Q carrier teeb liab siv hauv cov txheej txheem modulation yav dhau los thiab demodulated sib cais. Rau ob qho tib si I thiab Q teeb liab modulated los ntawm IQ, kev nce qhov sib piv ntawm ib sab tsis tsuas yog ua rau qhov amplitude ntawm lub teeb liab modulated nce ntxiv, tab sis kuj ua rau theem ntawm lub teeb liab modulated hloov mus rau sab nrog qhov amplitude nce ntxiv. Yog li ntawd, IQ modulation yog amplitude modulation ua rau ntawm I teeb liab thiab Q teeb liab, tab sis qhov tshwm sim modulation tsis tsuas yog cuam tshuam rau qhov amplitude ntawm lub teeb liab modulated, tab sis kuj nws qhov kev hloov pauv theem. Qhov no yog lub hauv paus ntsiab lus ua haujlwm ntawm IQ modulation thiab demodulation.