Signal Processing Devices Sweden Ab

Teledyne Signal Processing Devices Sweden Ab

Håkan Johansson

Per Löwenborg

A method and device for handling an in-phase and quadrature ('I/Q') channel mismatch of an I/Q down-converted signal, and a use of the device. A discrete-time complex valued signal r(n) based on an analog-to-digital conversion of the I/Q down-converted signal is obtained. The obtained discrete-time complex valued signal r(n) is oversampled by a factor of two or more. An intermediate signal v(n) is formed from the discrete-time complex valued signal r(n). The intermediate signal v(n) corresponds to the real part of a &#x3c0;/2 frequency shifted version of the obtained discrete-time complex valued signal r(n). A procedure for obtaining an estimate of a frequency dependent mismatch of a two-channel time-interleaved analog-to-digital converter ('TI-ADC') is applied on the formed intermediate signal v(n). Thereby a TI-ADC mismatch estimate is obtained. The I/Q channel mismatch is estimated and/or compensated based on the obtained TI-ADC mismatch estimate.

Methods and devices for handling channel mismatches of an I/Q down-converted signal and a two-channel TI-ADC

An estimation unit for estimating a nonlinearity error of a conversion circuit, such as an ADC, is adapted to receive a continuous-time input signal and output a digital output signal. In at least one embodiment, the continuous-time input signal is essentially bandlimited to an angular frequency band [&#x3c9;, &#x3c9;], where &#x3c9;&#x3e;(L&#x2212;1)&#x3c0;/T, &#x3c9;&#x3c;L&#x3c0;/T, L is a positive integer, and T is a sample period of the conversion circuit. The estimation unit includes an input port for receiving a digital input signal having a first sample rate 1/T and an output port for outputting a digital estimated error signal also having the first sample rate. For each integer P_k in a set of integers, the estimation unit a first linear filter unit for generating a first signal s(n) as a linear function of the digital input signal, an interpolation unit for interpolating the first signal s(n) to generate a second signal s(m) having a second sample rate which is a factor L&#xb7;R_k higher than the first sample rate, wherein L&#xb7;R_k&#x2267;&#x3c9;&#xb7;T&#xb7;P_k/&#x3c0;, a nonlinearity unit for generating a third signal s(m) as (s(m)), and a second linear filter unit for generating a component of the estimated error signal based on the third signal s(m), wherein the component has the first sample rate. Furthermore, the estimation unit includes an adder circuit for generating the estimated error signal as the sum of the components of the estimated error signal. Moreover, at least one embodiment is directed to a compensation circuit including the estimation unit, corresponding methods for estimating and compensating nonlinearity errors, a computer program product, a computer readable medium, and a hardware-description entity.

Methods and apparatuses for estimation and compensation on nonlinearity errors

Methods for compensation of imbalance between I (In-phase) and Q (Quadrature) signal paths () in a quadrature receiver () and a quadrature transmitter () are disclosed. In the receiver case, the imbalance is compensated for by means of post-distortion in the digital domain. In the transmitter case, the imbalance is compensated for by means of pre-distortion in the digital domain. The methods can be carried out with a relatively low computational complexity. Signal-processing devices () for carrying out the methods are disclosed as well. The same basic internal structure may be used for the signal-processing device () in the receiver case as for the signal processing device () in the transmitter case.

Methods and apparatuses for compensation of I/Q imbalance

A method and a module for estimating a plurality of relative channel-error for at least one signal with respect to a reference signal. The signals and are produced by an analog-to-digital module including parallel and time interleaved analog-to-digital converters and are received by an estimation module. The method is performed by the estimation module and includes defining a function representing a relationship between the reference signal and an arbitrary signal in the group of signals, selecting a first reference signal in the group of signals, selecting a second signal from the remaining signals in the group, optimizing the function so as to obtain an estimate of the plurality of relative channel-error, and repeating the selecting a second signal and optimizing the function for each remaining signal.

Method and a system for estimating errors introduced in a time-interleaved analog-to-digital converter system

A method for the compensation of frequency-response mismatch errors in M-channel time-interleaved ADCs. The compensation is done through an M-periodic time-varying filter h(k)=h(k) (2), or, equivalently, a set of M time-invariant filters h(k), n=0, 1, . . . , M&#x2212;1. The overall compensation system is constructed by determining the M filter impulse responses h(k) through M separate matrix inversions, where the size of the matrices equals the filter impulse response length. Also, a compensated M-channel time-interleaved ADC based on and performing the method.

Compensation of mismatch errors in a time-interleaved analog-to-digital converter

A method for estimating a relative time difference vector in a group of digitized signals from a time interleaved analog-to-digital module having a plurality of parallel and time interleaved analog-to-digital converters. The method comprises the steps of selecting (S) one of said digitized signals as a reference signal, calculating (S-S) an actual time delay between each of the remaining signals and said reference signal, and subtracting (S), for each of said remaining signals, an intended interleaving time delay from said time delay. In order for this method to provide the correct estimate, the signal must be bandlimited, not only to the system bandwidth, but to the bandwidth of one ADC. However, given this bandwidth limitation, the estimation is very precise, and therefore enables reconstruction of the digitized signal without feedback.

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Linköping, Sweden

Håkan Johansson