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The Almanack of Naval Ravikant

The Almanack of Naval Ravikant: Buy The Book Now!

Buy the book now! Yes, right now! The Almanack of Naval Ravikant is an incredible book packed with tons of wisdom on:

  • Differences between wealth and money
  • Being free
  • Using leverage to create wealth
  • A mental model for happiness

How to Write an Engineering Resume

A resume is an advertisement for an interview, no more, no less. In this blog I’ll describe the basics behind writing an engineering resume, including a simple format and how to use action words to make your resume more interesting and exciting.

Before getting started on the content of the resume, let’s first put ourselves in the shoes of the recruiter who is going to review your resume.

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Homebrew is used to install pdflatex, a command line utility for converting LaTeX into PDFs.

Install and Run LaTeX on macOS

Installing and running LaTeX on macOS can be done in four easy steps:

  • Install Homebrew
  • Install pdflatex with Homebrew
  • Install more LaTeX packages with tlmgr
  • Compiling LaTeX with a Makefile

Figure 5: The impulse response of an odd length SRRC allows for optimal sampling by being able to select the peak at n=0. An even length SRRC filter does not.

Why an FIR Filter Should Have an Odd Length

Today’s DSP Wisdom: odd-lengths are preferable to even-lengths in an FIR filter.

Powers of 2 are ubiquitous in DSP: binary number representations are in base-2, 3 \text{dB} is 10\text{log}_{10}(2), and modulations are powers of 2 (BPSK, QPSK, 8-PSK, 16-QAM). The radix-2 FFT is decomposed into 2-input, 2-output butterflies. Upsampling or decimation by 2 can be done efficiently with a half band filter.

I’ve been allured many times by the siren song of choosing DSP parameters solely because they are powers of 2. A natural fallout is I have typically chosen even parameters for things such as filter lengths because they divide cleanly by a power of 2. The downside is that selecting parameters based on ease of coding results can result in unintended consequences in the DSP.

In this example choosing an even length filter incorporates a fractional time delay at the output of the filter which can negatively effect systems which require precise sampling such as sampling symbols from a demodulator or synchronizing a correlation peak to reference signal.

Marie Kondo Your Office Y’all

Take a look at your office or lab space. Does it represent the quality of work you are doing in the office? Do you think your boss wants clients looking in there?

We’ve all been to “that office”. Maybe it’s the one with IEEE papers covering the desk, floor and walls like a hamster cage. Maybe it’s the one with the broken chair office visitors have to sit in. Maybe it’s just a musk in the air. Whatever it may be, no one wants to go in there and that’s an issue.

People know who has a tidy office and whose office is a mess and no one wants to be the one with the gross office. A tidy office leads people to believe you do high quality work and generally have your stuff together. Tidy does not mean spotless, it just means organized and picked up. You will also get huge points for having even a minimal amount of decoration.

Fourier Transform Explanation as a Cross-Correlation

For years I accepted the Fourier transform equation on faith without knowing where it came from or why it worked. Were you in the same situation? Are you there now? In this post I describe how the Fourier transform is the cross correlation between a signal x(t) and a complex exponential e^{j 2 \pi f t }. The Fourier transform explanation begins by reviewing cross correlation and then applies it to a complex exponential derive the continuous time and discrete time Fourier transform.

Figure 4: The frequency domain for the real passband version of the BPSK signal with noise.

Efficient Real to Complex Conversion with a Half Band Filter

You are going to have to perform a real to complex conversion at some point in your DSP career. The most common way is having to convert samples from a real analog to digital converter (ADC) to complex baseband. There are different ways to implement real to complex conversion however this algorithm is particularly efficient by downconverting from f_s/4 using only a handful of multiplies. Additional computational savings will come from the decimate by 2 half band filter to remove the negative frequency spectral image.

Note: I have heard of this algorithm referred to as a “quad-band downconverter” but I have not been able to find it elsewhere. (I have looked in all the books I have, internet searches, etc.) If you have a reference for it or the correct name please leave a comment below or send me an email.

Rodney Dangerfield and DSP

I came across this GIF of Rodney Dangerfield and saw the unit circle in the bottom right hand corner.

Always nice to see elements of DSP sprinkled into the real world!

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God, the Lord, is my strength; He makes my feet like the deer's; He makes me tread on my high places. Habakkuk 3:19
For everything there is a season, and a time for every matter under heaven. A time to cast away stones, and a time to gather stones together. A time to embrace, and a time to refrain from embracing. Ecclesiastes 3:1,5
The earth was without form and void, and darkness was over the face of the deep. And the Spirit of God was hovering over the face of the waters. Genesis 1:2
Behold, I am toward God as you are; I too was pinched off from a piece of clay. Job 33:6
Enter His gates with thanksgiving, and His courts with praise! Give thanks to Him; bless His name! Psalm 100:4
Lift up your hands to the holy place and bless the Lord! Psalm 134:2
Blessed is the man who trusts in the Lord, whose trust is the Lord. He is like a tree planted by water, that sends out its roots by the stream, and does not fear when heat comes, for its leaves remain green, and is not anxious in the year of drought, for it does not cease to bear fruit. Jeremiah 17:7-8
He said to him, “You shall love the Lord your God with all your heart and with all your soul and with all your mind. This is the great and first commandment. And a second is like it: You shall love your neighbor as yourself. On these two commandments depend all the Law and the Prophets.” Matthew 22:37-39
Then He said to me, “Prophesy over these bones, and say to them, O dry bones, hear the word of the Lord. Thus says the Lord God to these bones: Behold, I will cause breath to enter you, and you shall live." Ezekiel 37:4-5
Riches do not profit in the day of wrath, but righteousness delivers from death. Proverbs 11:4
The angel of the Lord appeared to him in a flame of fire out of the midst of a bush. He looked, and behold, the bush was burning, yet it was not consumed. And Moses said, “I will turn aside to see this great sight, why the bush is not burned.” When the Lord saw that he turned aside to see, God called to him out of the bush, “Moses, Moses!” And he said, “Here I am.” Exodus 3:2-3
Daniel answered and said: “Blessed be the name of God forever and ever, to whom belong wisdom and might. He changes times and seasons; He removes kings and sets up kings; He gives wisdom to the wise and knowledge to those who have understanding." Daniel 2:20-21
Now the Lord is the Spirit, and where the Spirit of the Lord is, there is freedom. 2 Corinthians 3:17
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