Work Pictures

Steve Thompson
Last updated: 5 Jan 2009

Communications signals can be whirly
A clipped OFDM signal, with a dash of color

Power amplifiers can be curvy
Model for the AM/AM and AM/PM conversions
for various power amplifiers

Chirping
A chirp signal has a linearly increasing frequency.
This figure can be created with:
“specgram(chirp([-2:0.001:15], 400, 10, 100,quadratic'))”
in GNU Octave

16 phase-shift keying
Possible transition made in the 16 PSK signal constellation (more)

Pick a number, any number
Integers from the set {-15,-13,...,13,15} generated
by a pseudo-random number generator

Sixty rings
Ring diameter is proportional to constant envelope signal
having k bits per transmission. For each case, the Eb/N0 (SNR) is
the same, but the carrier-to-noise ratios (CNRs) are different.
For the innermost circle, k=1; the outermost circle, k=61

A line's journey
The path taken, on the complex plane,
by the 50th subcarrier of a 128-subcarrier OFDM signal sampled
at the Nyquist rate (more)

Madness
4-PSK/OFDM distorted by solid-state
power amplifier with 3 dB backoff

Taking note
Every T seconds, N bits are transmitted.
Every T seconds, the signal changes
and a phase jump occurs.

..., if i could, if i could, ...
Trying to program.
Trying not to suck at programming.

Ball of yarn
What happens when you have a
large modulation index
and a relatively
low sampling rate.

Yall of barn
What happens when you have a
not-so large modulation index
and a relatively
low sampling rate—and a phase shift.

Thesis city
What happens when you have
to write a thesis—a little pretend
city grows around you.

Dancing noise
Noise. It keeps us busy.

Signal confetti
Hurray for the
low amplitude fluctuations!

Mind the boundaries
So long as all the circles
stay in their assigned boxes
Mr. Channel Coding can go sailing.

A ls'n on zoom
Even Mr. ls has pixels.

Big signal eats small signal
4 dB backoff stunts Mr. Green;
0 dB backoff doesn't stunt Mr. Red.
Mr. Red eats Mr. Green.

Your PAPR means nothing here
An input signal
with a large peak-to-average power ratio
gets distorted by a power amplifier.

20060112_nuclear
Balls of fading
Three Rayleigh fading channels
on the complex plane.

20060112_spiney
Spiney line-of-sight

Boomerang

Planetary noise

Forecast: Clear skies and high bit error rates

sin (x) = x

Sum it up

Must, run, simulation, longer

Streaming numbers

Bessel functions
(pdf, ps, source)

Flowering roots
A plot of all the roots of all the polynomials
with coefficients ±1, up to degree 14.
(GNU Octave m-file: plot_roots.m)
(See Polynomial Roots from MathWorld.)