The effects of mismatch in complex bandpass ΔΣ modulators

Jantzi, S.; Martin, K.; Sedra, A.S.

doi:10.1109/iscas.1996.539870

Cited by 16 publications

(13 citation statements)

References 5 publications

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“…This is because it was shown in [11] that only the relative difference between the branch values affects the mirror responses. In addition, it was confirmed in simulations that no significant differences appear between the transfer functions with symmetric and asymmetric mismatches.…”

Section: Effects Of Input Mismatchesmentioning

confidence: 99%

“…This results, in addition to the STF and the NTF, in two additional transfer functions, which are called an image signal transfer function (ISTF) and an image noise transfer function (INTF). Thus, the output of the mismatched modulator can generally be given in the form [11] …”

Section: I/q Imbalance Model For Quadrature Adcmentioning

confidence: 99%

“…This means that the deviation from the nominal value is opposite in the two channels. If the error is common and parallel between the branches, the desired response (STF or NTF) is affected but no mirror-frequency interference is present [11].…”

Section: I/q Imbalance Model For Quadrature Adcmentioning

confidence: 99%

“…In addition, mitigation of the MFI through sophisticated STF design will be addressed and identified. For reference, the properties of mirror-frequency rejecting NTF have been discussed already in [10][11][12]32] and a brief analysis on the related STF phenomenon has been given earlier in [10,12]. However, closed-form analysis of the imbalance phenomenon, presented in this article, gives more complete understanding on the generated interference, which in turn is essential in order to develop efficient mitigation methods.…”

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confidence: 99%

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Quadrature ΣΔ Modulators for Cognitive Radio—I/Q Imbalance Analysis and Complex Multiband Principle

Marttila

Allén

Valkama

2011

Circuits Syst Signal Process

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This article discusses the applicability of quadrature modulator (Q M) based analog-to-digital (A/D) conversion in cognitive radio (CR) receivers. First, unavoidable in-phase/quadrature (I/Q) mismatch effects, limiting the dynamic range, are analyzed in closed-form in the case of a first-order modulator. In addition, using the derived analytical converter model, it is shown that notching the signal transfer function (STF) of the modulator at the mirror frequencies of the desired signals will effectively cancel the I/Q imbalance induced mirror-frequency interference in case of the modulator feedback mismatch. In practice, such STF design is easy to implement within the existing converter circuitry, as will be demonstrated in this article. The latter part of the article proposes a novel complex multiband Q M scheme, particularly aimed for the CR receivers. This multiband scheme allows parallel reception of scattered frequency chunks in the CR context and is stemming from the additional degrees of freedom in noise transfer function (NTF) design, provided by the Q M principle. Here multiple noise shaping notches on distinct frequencies are effectively realized through proper design of complex NTF. The modulator structure also allows flexible reconfigurability of the notches with straightforward parameterization of the modulator transfer functions. When combined with the above mirror-frequency rejecting STF design, the concept is demonstrated and proved ef-

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Section: Effects Of Input Mismatchesmentioning

confidence: 99%

Section: I/q Imbalance Model For Quadrature Adcmentioning

confidence: 99%

Section: I/q Imbalance Model For Quadrature Adcmentioning

confidence: 99%

mentioning

confidence: 99%

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Quadrature ΣΔ Modulators for Cognitive Radio—I/Q Imbalance Analysis and Complex Multiband Principle

Marttila

Allén

Valkama

2011

Circuits Syst Signal Process

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“…Modifying the analog circuitry [39], careful layout [1], and making the circuit more robust are the analog solutions introduced in [32], [14], [39]. A digital solution introduced in [9], [25] is using off-line compensation of channel imbalances.…”

Section: Introductionmentioning

confidence: 99%

A novel adaptive mismatch cancellation system for quadrature IF radio receivers

Snelgrove²

1999

IEEE Trans. Circuits Syst. II

158

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This paper investigates and resolves in-phase/ quadrature phase (I=Q) imbalances between the input paths of quadrature IF receivers. These mismatches along the paths result in the image interference aliasing into the desired signal band, thus reducing the dynamic range and degrading the performance of the receivers. I=Q errors occur because of gain and phase imbalances between quadrature mixers. They are also caused by capacitor mismatches in analog-to-digital converters (A/D's), which are designed to be identical for each input path. This paper presents a novel and feasible digital signal processing (DSP) solution for the I=Q mismatch problems. The system includes a novel complex least mean square algorithm and a modified adaptive noise canceler (signal separator) to separate the desired signal and the image noise caused by the mismatch. The noise canceler can also solve the signal leakage problem, which is that the noise reference includes signal components. This system was implemented in a Xilinx FPGA and an Analog Devices DSP chip. It was tested with a complex intermediate frequency receiver, which includes an analog front end and a complex sigma-delta modulator. Both simulation results and test results show a dramatic attenuation of the image noise.Extending applications of the system to N -path systems further indicates the robustness and feasibility of this novel adaptive mismatch cancellation system.

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Gothenberg

Tenhunen

2002

Analog Integrated Circuits and Signal Processing

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The effects of mismatch in complex bandpass ΔΣ modulators

Cited by 16 publications

References 5 publications

Quadrature ΣΔ Modulators for Cognitive Radio—I/Q Imbalance Analysis and Complex Multiband Principle

Quadrature ΣΔ Modulators for Cognitive Radio—I/Q Imbalance Analysis and Complex Multiband Principle

A novel adaptive mismatch cancellation system for quadrature IF radio receivers

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