Radio Frequency Integrated Circuit Design - Webs

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LNA Design Finally, the noise figure of the circuit was plotted as shown in Figure 6.22. The design had a noise figure of 1.76 dB at 5 GHz, which is very close to the minimum achievable noise figure of 1.74 dB, showing that we have in fact noise-matched the circuit at 5 GHz. 6.3.4 Relationship Between Noise Figure and Bias Current Noise due to the base resistance is in series with the input voltage, so it sees the full amplifier gain. The output noise due to base resistance is given by vno, r b ≈ √ 4kTr b � g m1RL 169 (6.65) Note that this noise voltage is proportional to the collector current, as is the signal, so the SNR is independent of bias current. Collector shot noise is in parallel with collector signal current and is directly sent to the output load resistor. vno, I C ≈ √ 2qI C R L (6.66) Note that this output voltage is proportional to the square root of the collector current, and therefore, to improve the noise figure due to collector shot noise, we increase the current. Base shot noise can be converted to input voltage by considering the impedance on the base. If Z eq is the impedance on the base (formed by a combination of matching, base resistance, source resistance, and transistor input impedance), then Figure 6.22 Plot showing the noise figure compared to the minimum noise figure for the design.
170 Radio Frequency Integrated Circuit Design vno, I B ≈ √ 2qIC � Z eq g m R L (6.67) Note that this output voltage is proportional to the collector current raised to the power of 3/2. Therefore, to improve the noise figure due to base shot noise, we decrease the current, because the signal-to-noise ratio (in voltage terms) is inversely proportional to the square root of the collector current. Therefore, at low currents, collector shot noise will dominate and noise figure will improve with increasing current. However, the effect of base shot noise also increases and will eventually dominate. Thus, there will be some optimum level to which the collector current can be increased, beyond which the noise figure will start to degrade again. Note that this simple analysis ignores the fact that r b increases at lower currents, so, in practice, thermal noise due to r b is more important at low currents than is indicated by this analysis. 6.3.5 Effect of the Cascode on Noise Figure As discussed in Section 6.1.3, the cascode transistor is a common-base amplifier with current gain close to 1. By Kirchoff’s current law (KCL) of the dotted box in Figure 6.23, ic2 = ie2 − i b2 ≈ ie2. Thus, the cascode transistor is forced to pass the current of the driver on to the output. This includes signal and noise current. Thus, to a first order, the cascode can have no effect on the noise figure of the amplifier. However, in reality it will add some noise to the system. For this reason, the cascode LNA can never be as low noise as a commonemitter amplifier. Figure 6.23 A cascode LNA showing noise sources.
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Radio Frequency Integrated Circuit
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Radio Frequency Integrated Circuit
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Contents Foreword xv Acknowledgment
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Contents 3.8 Base Shot Noise Discus
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Contents 5.25 Packaging 135 5.25.1
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Contents 7.12 General Design Commen
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Contents 9.5 Some Simple Image Reje
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Foreword I enjoyed reading this boo
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Foreword estimates of parasitic cap
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xx Radio Frequency Integrated Circu
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2 Radio Frequency Integrated Circui
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2 Issues in RFIC Design, Noise, Lin
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Issues in RFIC Design, Noise, Linea
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The input noise is Issues in RFIC D
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2.5 Filtering Issues Issues in RFIC
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3 A Brief Review of Technology 3.1
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A Brief Review of Technology IC = I
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3.4 Small-Signal Model A Brief Revi
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3.6 High-Frequency Effects A Brief
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A Brief Review of Technology If thi
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A Brief Review of Technology Soluti
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A Brief Review of Technology 3.8 Ba
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A Brief Review of Technology • Pi
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A Brief Review of Technology 3.16,
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A Brief Review of Technology The tr
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4 Impedance Matching 4.1 Introducti
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Impedance Matching Z 2 = Z in + j
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Figure 4.5 A Smith chart. Impedance
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4.3 Impedance Matching Impedance Ma
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Impedance Matching Figure 4.9 Which
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Impedance Matching Figure 4.11 Lowp
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Impedance Matching section, convers
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Impedance Matching Much as in the p
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Impedance Matching Note that dots i
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Impedance Matching Thus, in the fir
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Impedance Matching The exact resist
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Impedance Matching 4.10 Quality Fac
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Impedance Matching Example 4.7 Matc
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Impedance Matching line to change w
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Impedance Matching S22 = b 2 a2 | a
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Impedance Matching without the need
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96 Radio Frequency Integrated Circu
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98 Radio Frequency Integrated Circu
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100 Radio Frequency Integrated Circ
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Voltage-Controlled Oscillators back
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I C_AVE = 1 Voltage-Controlled Osci
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Voltage-Controlled Oscillators Loop
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Voltage-Controlled Oscillators freq
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Voltage-Controlled Oscillators Figu
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Voltage-Controlled Oscillators from
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Voltage-Controlled Oscillators [10]
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10 Power Amplifiers 10.1 Introducti
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Power Amplifiers where G is the pow
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Power Amplifiers Figure 10.4 Optima
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Power Amplifiers Figure 10.8 Power
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Power Amplifiers Figure 10.9 Curren
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Power Amplifiers The efficiency is
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Power Amplifiers sinusoid), this pe
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Power Amplifiers Note that this agr
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Power Amplifiers stabilization. The
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Power Amplifiers Solution The first
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Power Amplifiers Figure 10.22 Class
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Figure 10.24 Class E waveforms. Pow
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Power Amplifiers B = 0.1836 0.81Q R
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Power Amplifiers Figure 10.25 Initi
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Power Amplifiers added to the funda
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Power Amplifiers 10.8.1 Variation o
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Example 10.4 Class F Power Amplifie
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Figure 10.36 Class H amplifier. Pow
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Power Amplifiers ered quite good. O
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Power Amplifiers Figure 10.39 Time-
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Figure 10.42 High-Q matching circui
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Figure 10.44 Multiple transistors.
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Power Amplifiers Figure 10.48 Combi
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Power Amplifiers have very narrow b
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Power Amplifiers Figure 10.53 Feedf
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Power Amplifiers in class A (input
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About the Authors John Rogers recei
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Index 1-dB compression point, 30-32
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Index Damped resonator, 247-48 Emit
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Index Local oscillator, 5 Mixing co
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Index Quadrature phase shift keying
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