An N-Path Enhanced-Q Tunable Filter With Reduced Harmonic Fold Back Effects

Mohammadpour, Amin; Behmanesh, Baktash; Atarodi, M.

doi:10.1109/tcsi.2013.2256238

Cited by 27 publications

(28 citation statements)

References 20 publications

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“…(4) suggests that the response of this system to an RF input at ω RF , includes not only the RF voltage, but also that of all the frequency contents residing with an offset of integer multiples of Nω s with respect to ω RF , i.e., ω RF ±Nω s , ω RF ± 2Nω s , etc. This phenomenon is known as harmonic fold-back (HFB) [5]. In particular, if ω s = ω RF , the closest fold-back occurs at (1 ± kN )ω s .…”

Section: A Review On N-path Filtersmentioning

confidence: 99%

“…It is shown in [2]- [4], [8] that while lacking reverse isolation, current-driven passive mixers with 25% non-overlapping clock phases can serve as an N-path filter. The function of N-path filters have also been mathematically verified by two schools of thought, one pertaining to linear time-variant analysis [2], [5], [6] and the other using impedance transformation property [4], [7]. N-path filtering has been widely used in modern transceivers, especially in the past two years [10]- [14].…”

Section: Introductionmentioning

confidence: 99%

“…However, there are three main drawbacks associated with N-path filters. First, as a switching network, N-path filters suffer from a phenomenon similar to aliasing, which is called harmonic fold-back (HFB) [2], [5]. Second, the frequency response of N-path filters exhibits replica at integer multiples of the switching frequency.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Analysis of imperfections in N-phase high-Q band-pass filters

Nikoofard

Kananian

Behmanesh

et al. 2015

2015 IEEE International Symposium on Circuits and Systems (ISCAS)

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The effect of clock skew and duty-cycle on the performance of high-Q N-phase band-pass filters (BPFs) have been examined in this paper. Following a mathematical approach and using the analytical derivations carried out, the effects of such non-idealities as clock skew and duty-cycle error are determined in an N-path filter. It is analytically proved that image signals from all integer multiples of the clock signal, rather than just those at (1 ± kN ) multiples of the clock signal, land atop the wanted RF spectrum. In a real world clock generator, with nonidealities in effect, filtering property and proper behavior of the filter is adversely affected. Finally, system level simulation along with circuit simulation using TSMC 0.18μm process have been performed which corroborate the proposed analytical derivations.

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Section: A Review On N-path Filtersmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Analysis of imperfections in N-phase high-Q band-pass filters

Nikoofard

Kananian

Behmanesh

et al. 2015

2015 IEEE International Symposium on Circuits and Systems (ISCAS)

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“…In fact, aliasing effect causes N‐path filters to have folding transfer functions in addition to the frequency response. So far, several analyses have been proposed for N‐path filter transfer function; some are accurate but complex, while others have less complexity and accuracy …”

Section: Introductionmentioning

confidence: 99%

“…In Mohammadpour et al, with Fourier series expansion, frequency response of a differential N‐path filter, including folding response of the filter, is derived. Although methods proposed in Ghaffari et al and Mohammadpour et al accurately represent frequency responses of N‐path filters, they cannot easily be used to address nonidealities of N‐path filters that cause energy sharing between paths. In Ho and Hameed and Pamarti, analysis of N‐path filter is performed by using matrix‐based calculation.…”

Section: Introductionmentioning

confidence: 99%

Analysis of nonidealities of N‐path circuits using impulse response

Mohammadpour

Nabavi

2020

Circuit Theory & Apps

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Summary This paper presents a new method to analyze nonidealities of N‐path circuits. This method utilizes Fourier transform of the impulse response of an N‐path circuit in the time domain to calculate the transfer functions. The time domain analysis makes the method simple and intuitive. Instead of conventional sophisticated calculations, this method limits the analysis to some integral calculations. This analysis can take into account two common nonidealities: parallel capacitance and overlapping clocks. The accuracy of the analysis is verified by simulations for both cases. Further, the analysis has been expanded to differential filters.

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Harmonic fold back reduction at the N‐path filters

Hemati

Jannesari

2016

Circuit Theory & Apps

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Summary In this paper, a method is proposed to reduce harmonic fold back (HFB) problem of N‐path filters, without increasing the input reference clock (fCLK) frequency. The HFB at the N‐path filter is analyzed, and simple expressions are extracted to model this problem. Using the results of the analysis, an M‐of‐N‐path filter has been proposed that behaves like an M × N‐path filter in terms of HFB problem; however, the fCLK frequency of this structure is the same as an N‐path filter. To demonstrate the feasibility of the proposed idea, a 3‐of‐4‐path filter is designed, and its characteristics are compared with 4‐path and 12‐path filters by simulation. Impacts of different non‐idealities like clock‐phase error, mismatch, and parasitic capacitance are investigated. The transistor‐level implementation of this filter is performed in 0.18 µm Complementary Metal Oxide Semiconductor (CMOS) technology. The simulation results show that the filter has the pass‐band gain of 17 dB, tuning range of 0.2–1.2 GHz, −3 dB bandwidth of 25 MHz, quality factor of 8–48, 18 dB out‐of‐band rejection, 16 dB rejection of the third harmonic of switching frequency (fs), and the noise figure of 4.35 dB (using ideal Gm cells) and 6.95 dB (for practical Gm cells). The strongest harmonic folding to the filter pass‐band occurs around 11fs with the attenuation of 23.8 dB. Each Gm cell draws about 12.4 mA from 1.8 V supply, and the out‐of‐band IIP3 and P1 dB,CP are 17 and 4 dBm, respectively. Copyright © 2016 John Wiley & Sons, Ltd.

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An N-Path Enhanced-Q Tunable Filter With Reduced Harmonic Fold Back Effects

Cited by 27 publications

References 20 publications

Analysis of imperfections in N-phase high-Q band-pass filters

Analysis of imperfections in N-phase high-Q band-pass filters

Analysis of nonidealities of N‐path circuits using impulse response

Harmonic fold back reduction at the N‐path filters

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