From Analog to Software Defined:

A History of the Radio

Dr. Roland Kempter

kempter@ece.utah.edu

Organization

1. The History of Radio Communication (incomplete)

2. Important Concepts: Filtering and Modulation

3. Background: Fourier Series Expansion

4. SIMULINK Demo

5. From Analog to Digital: Software Defined Radio

6. Programming Software Defined Radios

History of the Radio: James C. Maxwell

1861-1865: James Clerk Maxwellexperiments with electromagnetic waves

1873: describes the propagation of electromagnetic waves in his paper “A Dynamical Theory of the Electromagnetic Field”

Wireless Radio Begins: Nikola Tesla

1893: Tesla gives public demonstration of wireless radio communication at St. Louis, Missouri.

He describes in detail the principles of radio communication.

Wireless Radio Begins: Guglielmo Marconi and K. F. Braun

1896: G. Marconi is awarded a patent for radio:Improvements in Transmitting Electrical Impulses and Signals and in Apparatus There-for

1897: Marconi establishes a radio station on the Isle of Wight (England)

1909: Marconi and Karl Ferdinand Braun win Nobel Prize in Physics for "contributions to the development of wireless telegraphy"

The History of the Radio

Better Sound Quality: FM Radio

1933: Edwin H. Armstrong patents FM radio (better quality than AM)

1940s: analog television transmissions start in North America and Europe.

The History of the Radio: the 21st century

Internet radioStreaming Internet connection, no RF, IF, etc.

Digital Audio Broadcasting (DAB)alternative to FM

Satellite RadioXM Radio, Sirius Satellite Radio

etc…

Going from analog “payload” to digital “payload”

However, radio itself still “analog” up to the decoder stage

The Fundamental Blocks in a Radio

Move signal from RF to baseband (original signal)HOW?

Remove frequency componentsHOW?

Increase amplitude of signalmultiply by constant

Fourier Series Expansion

The Theory Behind Radio Technology: Fourier Series

Jean Baptiste Joseph Fourier (1768-1830)French mathematician and physicist

Idea:“any” periodic function can be decomposed into an (infinite) sum of sines and cosines Fourier applied it to to problems of heat flow.

1824: gases in the atmosphere increase the surface temperature of the Earth. Fourier described the greenhouse effect!

Fourier Seriesdescribes the frequency content of periodic signals

The Theory Behind Radio Technology: Fourier Series

Different Time Domain signals have different harmonics (# and magnitude)

Example: Square Pulse, infinite # harmonics!

With 250 harmonics:

Gibbs phenomenonat discontinuity

Example: Sawtooth Wave

Example: Triangle Wave

Some TD signals are suited better for transmission than others (less harmonics)

Rect-wave: poor TD quality with 25 harmonics

Sawtooth-wave: poor TD quality with 25 harmonics

Triangle-wave: pretty good TD quality with 10 harmonics

Example: Fourier Transform

Courtesy of Thomas F. WeissMassachusetts Institute of Technology

(right) logarithm of the magnitude of the FT of Fourier

What is Modulation

Modulation: multiplication of baseband signal by a carrier wave

Periodic signal can be expanded into series of sine + cosine apply the above expression to every single one of those.

Move arbitrary baseband signal into higher bands

Fundamental Blocks: Why is Modulation Necessary?

At least 2 reasons:

1. different signals from different systems do not interfere

Example: - broad band cable services- Public TV and Radio (wireless services)

2. move the payload signal to frequency where it can be transmitted most easily

Problem: - signal attenuation in wires- free space signal attenuation

What is Filtering?

Input Signal

Filter Response

Output Signal

Modulation and Demodulation

Demodulate:x fc

Modulate:x fc

Filter:

Fourier Series: Continuous and Discrete

Nice, but all of this was for continuous signals,What about discrete (digital) samples?

Fourier works in digital, too: Discrete Fourier Transform

SIMULINK DEMO

BPSK Radio

A Radio?

A Conventional Radio: all in Analog

New Paradigm: Software Defined Radio (SDR)

RX Signals are digitized immediately after the LNAand then processed entirely in software, flexible

TX vice versa

Software Defined Radio:

A Radio!

SDR is Real!

23 November 2004: FCC approves the first SDR device in the United States. If radio changes behavior, no more re-approval necessary!

VANU Inc., ANYWAVE cellular base station:HP proliant server, ADC/DAC, running Linux,can act as a GSM, CDMA and UMTS basestationthrough software updates

Programming Software Defined Radios: Download?

Trinity: Operator, I need a pilot program for a V-212 helicopter!

Various manufacturers of SDR boards various flavors of hardware, on-the-fly reconfiguration

requires specific configuration files! Infeasible!

Different people have different brains! Different Hardware, simple downloads won’t work!

But

Describe to the target (brain) what to do:Give presentations instead of .exe files

Programming Software Defined Radios: Now and Future

“Classical” way: VERILOGProblem: hardware (board) specific, rewrite for different boards

State-of-the-art: SCA, Software Communication ArchitectureCORBA, XML with Object Request Broker (ORB) middleware

Future: Ontology-based programming languages, “describe” to the board what to do, board (compiler) figures out how and if possible

1. Easier board programming, do it once for different architectures

2. Enable reconfiguration “on-the-fly”, download of new policies

Benefits:

SDR with Ontology Language

SDR to Operator:I’ve been an AM radio all my life, I want to become an FM radio!

Operator:You’ll need to reconfigure your demodulator.

SDR:How do I do that?

Operator:You need 15 multipliers and 20 adders, do you have that?

SDR:Yes.

Operator:Now connect….

About us: SDR at the Wireless Communications Lab

2 Laptops running the GNU radio software, modified to work as 4 by 4 MIMO system, progam PHY

In January: upgrade to 3 boards that feature VIRTEX 4 + ARM 9 + DSP, running real-time OS, program PHY, MAC and Network layers

Now:

Why all that?

WE WANT YOUFOR

SOFTWARE DEFINED RADIO