What is SDR?

17
Software Defined Radio on Field Programmable Gate Array Karel L STERCKX Shinawatra University, Thailand SDR - on - FPGA SDR - on - FPGA SDR - on - FPGA SDR - on - FPGA

description

Software Defined Radio on Field Programmable Gate Array Karel L STERCKX Shinawatra University, Thailand. What is SDR?. SDR aims to implement as much of the electronics of a communication system on programmable digital platforms, preferably a single platform  System On Programmable Chip (SOPC) - PowerPoint PPT Presentation

Transcript of What is SDR?

Software Defined Radio onField Programmable Gate Array

Karel L STERCKXShinawatra University, Thailand

SDR- on -FPGA

SDR- on -FPGA

SDR- on -FPGA

SDR- on -FPGA

2

What is SDR?

SDR aims to implement as much of the electronics of a communication system on programmable digital platforms, preferably a single platform System On Programmable Chip (SOPC)

Places the analogue/digital conversion as close as possible to the antenna Ideally

ADC immediately after the Low Noise Amplifier (LNA) DAC in front of the RF Power Amplifier (PA)

Analogue/digital conversion at RF is not yet possible Analogue IF/RF conversion of IQ signals is necessary Note that phase modulation (hence, also frequency modulation) is

accomplished via amplitude modulation (which is simpler) of two orthogonal carriers, called the In-phase and Quadrature-phase carriers

Figure on the next slide illustrates the present day implementation of SDR

3

SDR Illustrated

Programmable Chip

ADC

Local Oscillator

Q

IADC

Antenna

LNA

I

Q

PA

90° 0°

Dem

odul

ator

DAC

DAC

90° 0°

Dec

oder

Mod

ulat

or

Enc

oder

Data Out

Data In

RF IF Baseband

4

Advantages of SDR

The Digital Advantage: Merits of processing signals in digital format More robust against noise and processing errors → Signal deviations, if

not too large, are still recognised as 0 or 1 Error coding can be added to enhance robustness against noise More effective → E.g. FIR filter has sharp roll-off and linear phase Requires no tuning or tweaking

The Software Advantage Designs can be upgraded Multiple radio standards, existing and emerging, can be supported Designs are portable → Can run on different hardware platforms Reconfigurable on the fly → Users can operate one radio in different

countries with different communication standards Reusability of designs or parts thereof

5

Advantages of SDR (2)

Allows for Cognitive Radio (CR) → CR senses and responds to RF spectrum conditions

- Ability to find unused spectrum (active spectrum utilisation typically falls below 5%, even in dense populated areas)

- Potential to seek low-cost communication channels → E.g. VoIP via WiFi instead of cellular phone links

The System-on-Chip (Soc) Advantage: Designs Are faster Use less power → Especially important in battery-powered devices Occupy less PCB space → Especially important in hand-held devices

6

SDR Implementation Platform

Most suitable platform is the Field Programmable Gate Array (FPGA)

A single programmable chip that contains all components that are required to implement a communication system up to IF modulation

Combinational and sequential logic to implement coding Multipliers and adders, which are essential to the implementation of

modulation/demodulation- Multipliers implement mixers- Adders combine signals- Multipliers and adders combine as a multiplier-accumulator (MAC), the

building block of digital filters

Phase Locked Loops (PLLs) to facilitate clock management High-end FPGAs also enable the implementation of an embedded RISC

processor Comparison of FPGA with other programmable digital chips is

provided next

7

FPGA vs. Processor

FPGA Software configures hardware Hardware processes data only →

More effective Allows for parallel as well as

sequential execution About 10 cheaper

Processor Software runs on fixed hardware Hardware processes code as well as

data Allows for sequential execution

only

About 10 higher clock speeds

Sequential and parallel processing are illustrated on the next two slides, respectively

Illustrations on these two slides were taken from the Xilinx white paper ‘Comparing and Contrasting FPGA and Microprocessor System Design and Development’ by Karen Parnell and Roger Bryner, July 21, 2004, WP213 (v1.1)

8

Sequential Processing

Limited resources are time-shared Used in conventional DSP processors

9

Parallel Processing

A large number of similar resources can be configured to execute in parallel

Used to implement DSP functions on FPGA

10

FPGA vs. CPLD

FPGA = Field Programmable Gate Array

Consist of small logic elements that can be interconnected via programmable interconnects that run through run throughout the entire chip → More flexible

Register (flip-flop) rich → Suitable for implementation of registers and counters

Higher-level embedded functions (notably adders and multipliers) and embedded memories, facilitating Lookup Tables (LUTs)

In system (re)programmable

Need to be reprogrammed after power shutdown

CPLD = Complex Programmable Logic Device

Consist of large sum-of-product logic arrays that can be inter-connected via a centrally located Programmable interconnect Array (PIA) → More predictable time delays

Limited number of flipflops → More suited for large combinational logic and complex FSMs

No higher-level embedded functions and no embedded memories

Need to be removed from the circuit when being (re)programmed

Retain the programmed configuration after power shutdown

11

CPLD Architecture

PIA

LAB

LAB = Logic Array Block

PIA = Programmable Interconnection Array

I/O = Input/Output

...

LAB

LAB

LAB

...

I/O

I/O

I/O

I/O

12

Architecture of FPGA Logic

I/O

I/O

LELELE

I/O I/OI/O

I/O LELELE

I/O LELELE

I/OI/O

I/OI/O I/OI/O

...

... ... ... ...

...

I/OLE

I/OLE

I/OLE

I/OI/O

...

...

...

... ... ProgrammableInterconnection

LE = Logic Element

I/O = Input/Output Block

13

Example of FPGA Architecture: Altera Cyclone II

14

Manufacturers

The following companies are the market leaders in FPGA manufacturing

Xilinx: www.xilinx.com Altera: www.altera.com

Both are based in San Jose, CA, USA FPGA related products of the market leaders are summarised on the

next two slides Other manufacturers of programmable logic are

Actel (www.actel.com) Atmel (www.atmel.com) Lattice (www.latticesemi.com)

15

Xilinx and Altera FPGA related Products

Xilinx FPGA

Spartan Series: Low Cost Virtex Series: High Performance EasyPath: Mid range

Design Software ISE System Generator for DSP →

Includes automatic code generation from Simulink and MATLAB

Embedded processor Name: Microblaze Type: 32-bit RISC Implemented in the logic and

memory blocks of the Virtex architecture

Altera FPGA

Cyclone Series: Low Cost Stratix Series: High Performance Aria: Mid range

Design Software Quartus II DSP Builder → Includes automatic

code generation from Simulink and MATLAB

Embedded processor Name: NIOS II Type: 32-bit RISC Implemented in the logic and

memory blocks of the Stratix architecture

16

Useful SDR Links

SDR Forum Non-profit international industry association dedicated to promoting the

success of next generation radio technologies Established in 1996 Website: www.sdrforum.org

GNU Radio Open source SDR project of the Free Software Foundation (www.fsf.org) GNU Radio applications are primarily written using the Python

programming language Website: http://gnuradio.org/trac

Thank you for your attention!Questions?

Karel L STERCKX([email protected])

SDR- on -FPGA

SDR- on -FPGA

SDR- on -FPGA

SDR- on -FPGA