III. Gm-C Filtering - Epublications - Université de Limoges

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A 4-path filter, for instance, consists in four parallel identical filter cells which are cyclically sampled with a clock frequency. A bandpass filter centered at the clock frequency fc can then be used. Hence, frequency tuning means tuning the sampling frequency. Figure 183. Amplitude response of a 4-path filter As explained in [V.3] and depicted in Figure 184.a, mixers are realized by means of switches driven by multiphase clocks. Low pass filters are simply implemented with an RC network. Since a resistor is a memory-less element, it can be shared by all paths and shifted in front of them. Furthermore, the first set of switches can also implement the function of the second set of switches, if Vout is tapped between the resistor and the switches, as illustrated in Figure 184.b and detailed in [V.3]. Figure 184. Switched-RC 4-path filter (a) and the simplified version (b) The filter bandwidth is determined by a baseband low-pass filter. Indeed, due to the lack of reverse isolation, the passive mixer constituted by the switches frequency-translates the baseband impedance to RF. Therefore, very small cut-off frequencies can be achieved and, by up-conversion at the sampling frequency, create a highly selective bandpass filter whose central frequency is controlled by the clock frequency. In the following, simulations are run in a 4-path configuration to describe and quantify the impact of all parameters. - 162 -
V.2 4-path Filter Simulations V.2.a 4-path Filter Architecture Figure 185. Simulated 4-path filter phi 0° phi 90° phi 180° phi 270° Figure 186. Non-overlapped 25% duty-cycle clocks This 4-path filter architecture presented in Figure 185 uses a non-overlapped 25% duty-cycle clock depicted in Figure 186. It also cancels the even harmonics of the switching frequency due to anti-phase switching of the differential input. To simplify, it has been chosen to perform first simulation trials with a 4-path (N=4) architecture. With an N-phase high-Q BPF, the closest folding frequency is shifted to (N-1) th harmonic, which can be pushed to high frequency by using a large N value. However, “although folding frequencies are moved to higher frequencies, the input impedance seen from the RF side is equal to the baseband impedance shifted to the LO frequency and all of its odd harmonics, along with scaling factors that resemble to sinc function with respect to the harmonic number” [V.4]. - 163 -
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UNIVERSITE DE LIMOGES ECOLE DOCTORA
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Acknowledgments En préambule à ce
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Summary ACKNOWLEDGMENTS ...........
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V. A PERSPECTIVE FOR FUTURE DEVELOP
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French Introduction Les signaux TV
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I. Introduction to TV tuners and to
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I.1.b.ii Digital modulations In dig
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makes the covering of a large terri
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I.1.c.iii Terrestrial spectrum Firs
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I.1.e Broadband Reception Systems F
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I.2.b TV Tuner High Performance Spe
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I.2.b.ii High linearity Although co
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I.3 RF Filter Specifications I.3.a
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27. This leads to the downconversio
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These adjacent channel rejection re
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Above 870MHz, there are no more ter
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Newest silicon tuners generations,
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I.6 References [I.1] B. Razavi, RF
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II. Challenges of RF Selectivity Fo
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Figure 39. H3 and N+5 rejections of
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Figure 43. Second order Low-pass Fi
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Figure 46 illustrates the transfer
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H HPF s ( s) = s 1 + ω This corres
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Topologies comparison for a same Q-
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Figure 56. Low-pass to Notch Transf
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II.2 Passive LC Second Order Bandpa
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A possible solution is to split the
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II.2.c Second Order Bandpass Filter
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Figure 69. Band Switching Figure 70
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Another paper [II.7] provides a FOM
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A parallel self resonating circuit
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This gives the following values for
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Vb - 63 - M1 M2 Zin Figure 76. Anot
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when given, reported noise figures
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In all publications dedicated to Gm
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II.4.c Second Order Bandpass Filter
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Figure 87. Biquad Schematic The Gm-
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Vin Rm - 73 - C Vout Figure 89. Der
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Figure 93 depicts the RF performanc
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A second advantage of advanced BiCM
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II.7 Conclusion As a conclusion, th
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[II.13] C. Andriesei, L. Goras, and
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III.I Theoretical Study III. Gm-C F
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g V m3 in III.1.b Linearity Conside
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Assuming an ideal input transconduc
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Figure 102. Linearity of the filter
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Furthermore, a Gm-C circuit is not
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In terms of noise, the Flicker nois
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Table 7 summarizes the specificatio
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Idiff (A) levels reached with this
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III.2.e Unbalanced Differential Pai
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Hence, the combination of the expon
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Technique Current Increase Source D
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Using this structure and considerin
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The dimensioning of the transistors
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III.3.c Gm-cells with MGTR III.3.c.
Page 115 and 116: Furthermore, the high sensitivity t
Page 117 and 118: Figure 136. Filter in-band IIP3 ver
Page 119 and 120: III.4 Comparison of the filters III
Page 121 and 122: III.5 Conclusion Once the Gm-C seco
Page 123 and 124: IV. Rauch Filtering IV.1 Sallen-Key
Page 125 and 126: Thus, an equation linking Q and Gai
Page 127 and 128: IV.1.c.ii Proposed positive feedbac
Page 129 and 130: For both Rauch and Sallen-Key filte
Page 131 and 132: The high sensitivity to passive com
Page 133 and 134: Furthermore, it should also be take
Page 135 and 136: IV.2.b Innovative Implementation of
Page 137 and 138: esulting gain K, constituted of the
Page 139 and 140: Table 25. Sum-up of the OA specific
Page 141 and 142: Figure 153. OA voltage gain versus
Page 143 and 144: Filtering in the mirror, by means o
Page 145 and 146: However, this feedback makes the fi
Page 147 and 148: Figure 160. OA Gain and phase versu
Page 149 and 150: IV.3.c Implemented Filter and Test
Page 151 and 152: Figure 165 depicts the layout of th
Page 153 and 154: Figure 169. PVT variations of the f
Page 155 and 156: IV.4 Rauch Filter Performances: Mea
Page 157 and 158: Figure 178. IIP3 versus input power
Page 159 and 160: IV.4.c Performances Sum-up The filt
Page 161 and 162: Table 30. Frequency Limitations of
Page 163 and 164: IV.7 References [IV.1] Y. Tsividis
Page 165: V. A Perspective for Future Develop
Page 169 and 170: The frequency tunability is ensured
Page 171 and 172: V.3 State-of-the-Art V.3.a 4-path F
Page 173 and 174: V.4 Conclusion In this chapter, it
Page 175 and 176: IEEE International, 2009, pp. 222-2
Page 177 and 178: RF selectivity challenges In this t
Page 179 and 180: The positive feedback Rauch filter
Page 181 and 182: It is worth highlighting that FOM1
Page 183 and 184: étudiée. Il s’avère que la lin
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Page 187 and 188: A.3 Signal-to-Noise Ratio These dif
Page 189 and 190: A.5 Friis’ Formula In case of mul
Page 191 and 192: A.7 References [A.1] Friis, H.T., N
Page 193 and 194: To estimate the influence of the di
Page 195 and 196: Now, let’s have a look to the cub
Page 197 and 198: Figure 200. Third order intercept p
Page 199 and 200: B.2 RF Filter Linearity Measurement
Page 201 and 202: B.2.c IIP2 measurement To measure t
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Page 205 and 206: C.1 Gyrator-C filtering year Ref. f
Page 207 and 208: C.2 Gm-C Filtering year Ref. f0 (MH
Page 209 and 210: year C.3 Rm-C filtering Ref. f0 (MH
Page 211 and 212: C.5 References C.5.a Gyrator-C filt
Page 213 and 214: [C.23] J. De Lima and C. Dualibe,
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this gives: I I I md d1 d 2 = I I =
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D.2 MOS Degenerated Common-Source C
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⎛ I s ⎞ Vout = Vin + U T ln ⎜
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Computing, this leads to: V out + v
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FIGURE 54. H3 AND N+5 REJECTIONS AC
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FIGURE 168. PVT VARIATIONS OF THE F
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