Reading activity - "Hardware Design Guide: From Device Cognition to Mobile Phone Baseband Design" Book Report (2): ch3, ch4

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Reading activity - "Hardware Design Guide: From Device Cognition to Mobile Phone Baseband Design" Book Report (2): ch3, ch4 [Copy link]

Reading activity - "Hardware Design Guide: From Device Cognition to Mobile Phone Baseband Design" Book Report (2): ch3, ch4

This time we will look at ch3 analog signal processing and ch4 signal integrity basics

The contents of ch3 are as follows:

1 ADC

2 Signal Analysis Basics

3 Passive Filters

4 Common-mode and differential-mode signals

5 Operational Amplifier Basics

6 Practical case explanation

This section explains the basic concepts of ADC, including sampling rate, resolution, LSB, ENOB and other parameters. There is also an example of using a simple circuit built by myself to imitate the working principle of ADC, which I think is quite interesting.

The second section is an introduction to the basics of signal analysis.

The concepts of Fourier transform and time-frequency analysis are introduced, the differences between the two analyses are compared, and the calculation of signal-to-noise ratio in the time domain and frequency domain is introduced (the author explains that calculating SNR in the frequency domain is more accurate).

The principles of modulation and demodulation are introduced, and how the spectrum is moved in the process is explained.

Fourier transform and PWM are introduced, Fourier analysis of PWM is analyzed, and the author gives three conclusions.

This section also explains why the system bandwidth is defined as -3dB: half-power point, A=0.707.

Section 3 introduces passive filters.

Two sets of correspondences are introduced separately, and there are derivation and simulation images.

Low pass filter - Integrator

High pass filter -- Differentiator.

Then we introduced what a second-order filter is, and compared the performance of first-order, second-order, and third-order low-pass filters through simulation.

The next question is whether to filter first or amplify first. The author gives his own thoughts: for weak signals, filter first and then amplify.

Section 3.4 introduces a relatively classic concept: common mode signal and differential signal

The author introduced the characteristics of differential signals based on operational amplifiers and MIPI. I think these two perspectives fully explain the concept and characteristics of differential signals, covering analog differential signals and high-speed digital differential signals.

Section 3.5

The operational amplifier based non-inverting amplifier and inverting amplifier circuits are introduced:

Empty, empty, short;

Analyzing Circuits Using Source-Load Models

Section 3.6 is a practical case study

What I find more interesting is the analysis of capacitance in 3.6.1 and the analysis method used.

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Chapter 4

Section 4.1: Starting from the transmission line

The first part of this section explains the difference between high speed, high frequency, and high bandwidth

High speed - the speed at which the signal changes, the rising edge is very narrow - high-speed signal

High frequency - the frequency of the signal itself

High bandwidth - frequency range occupied

The second part introduces loop inductance and how to reduce it.

Here we introduce the concepts of signal path and return path.

The third section introduces reference planes and transmission lines:

A pair of conductors make up a transmission line, one is the signal path and the other is the "reference path" or "return path"

The signal propagation model in the transmission line is a distributed parameter model.

The fourth part introduces the difference between microstrip line and stripline:

Microstrip line - a transmission line with only one reference plane

Stripline - a transmission line with two reference planes, upper and lower

The fifth part introduces characteristic impedance. This part contains both the author's derivation and the author's analogy.

4.2 Signal Reflection

During signal propagation, the impedance suddenly increases, causing positive reflection

Z1 is the current impedance and Z2 is the new impedance

Reflection coefficient

R = (Z2-Z1)/(Z2+Z1)

The author analyzed three situations

Z2 is infinite, open circuit, R is approximately equal to 1

Z2=Z1, impedance does not change suddenly

Z2=0, short circuit, R=-1

The author then used a circuit to explain reflection.

In the next section, the author introduces the control of impedance:

Line width W, dielectric thickness h, dielectric constant, copper foil thickness these four parameters are controlled

Section 4.3 introduces the sources of crosstalk and how to suppress it.

Source: Capacitive coupling Inductive coupling

Control: Increase the spacing between lines; reduce the length of parallel lines; do a good job of impedance control or termination; use ground wire isolation.

It also introduces things to pay attention to when routing equal lengths to ensure equal delays

Section 4.4 introduces S parameters, which are used to describe transmission lines.

Introduced the meaning of S parameters

Section 4.5 is a practical case study

4.5.1 introduces termination resistance and impedance matching

Two termination methods:

The source series resistor,

Receiving end parallel resistance

Section 4.5.2 TDR Impedance Measurement

TDR Time Domain Reflectometer

TDR uses the reflection of the signal to evaluate the degree of impedance change in the link. Here is an introduction to the working principle of TDR

I have gained a lot from reading this book. I have learned a lot of new concepts and practical experience. The next time I read Chapter 5, it will be a more systematic introduction.