DIGITAL IQ IMBALANCE COMPENSATION FOR DUAL-CARRIER DOUBLE CONVERSION RECEIVER
First Claim
1. A method of compensating for imbalances between the In-phase (I) and Quadrature (Q) components (IQ imbalance) of communication signals processed by a multi-carrier multiple conversion receiver operative in a radio frequency (RF) wireless communication network, the receiver having two or more receiver chains, each operative to downconvert signals modulated onto different RF carrier frequencies to baseband via at least one intermediate frequency (IF), the method comprising:
- processing, in a first receiver chain, a first signal modulated onto a first RF carrier;
processing, in a second receiver chain that utilizes one or more RF or IF components of the first receiver chain, a second signal modulated onto a second RF carrier, different from the first carrier;
downconverting the first and second signals to baseband by conversion from the respective RF carrier frequencies to an IF, and by further conversion from the IF to baseband;
processing known reference signals in each receiver branch;
deriving IQ imbalance estimates associated with each receiver chain as the values that best match each received signal with one of the corresponding known reference signal or the corresponding known reference signal modified by the corresponding channel estimate; and
compensating the received signals for the IQ imbalance based on the IQ imbalance estimates.
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Accused Products
Abstract
Digital IQ imbalance compensation is utilized for a dual-carrier double conversion receiver. First, the effect of IQ imbalance on OFDM-based digital baseband is analyzed, showing that, in the presence of IQ imbalance, the baseband signal of each carrier is obtained from its own branch as well as the other branch. Second, IQ imbalance parameters of interest are estimated using pilot signals and compensated using only digital baseband processing.
23 Citations
24 Claims
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1. A method of compensating for imbalances between the In-phase (I) and Quadrature (Q) components (IQ imbalance) of communication signals processed by a multi-carrier multiple conversion receiver operative in a radio frequency (RF) wireless communication network, the receiver having two or more receiver chains, each operative to downconvert signals modulated onto different RF carrier frequencies to baseband via at least one intermediate frequency (IF), the method comprising:
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processing, in a first receiver chain, a first signal modulated onto a first RF carrier; processing, in a second receiver chain that utilizes one or more RF or IF components of the first receiver chain, a second signal modulated onto a second RF carrier, different from the first carrier; downconverting the first and second signals to baseband by conversion from the respective RF carrier frequencies to an IF, and by further conversion from the IF to baseband; processing known reference signals in each receiver branch; deriving IQ imbalance estimates associated with each receiver chain as the values that best match each received signal with one of the corresponding known reference signal or the corresponding known reference signal modified by the corresponding channel estimate; and compensating the received signals for the IQ imbalance based on the IQ imbalance estimates. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A wideband intermediate frequency (IF) dual-carrier double conversion receiver operative to process first and second communication signals, modulated onto first and second radio frequency (RF) carriers, respectively, comprising:
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a first receiver chain comprising RF local oscillators (LO) operative to perform RF mixing and RF LOs operative to perform IF mixing, the first receiver chain operative to double convert a first signal from a first RF carrier frequency to an IF and then to baseband; a second receiver chain sharing one or more RF LOs with the first receiver chain and operative to double convert a second signal from a second RF carrier frequency, different than the first RF carrier frequency, to the IF and then to baseband; wherein the first and second receiver chains are operative to process known reference signals; an IQ imbalance estimator operative to estimate IQ imbalance in each receiver chain as the values that best match each signal with one of a corresponding known reference signal or a corresponding known reference signal modified by a corresponding channel estimate; and an equalizer operative to compensate the first and second baseband signals so as remove the estimated IQ imbalance. - View Dependent Claims (14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24)
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Specification