Ministry of DefenceElectronics, Logistics andProperty Management Co.

Contents

1. Introduction......................................................................................................................... 32. Software radio-techniques .................................................................................................. 43. Equipment functionalities................................................................................................... 74. Equipment structure............................................................................................................ 9

4.1. Baseband unit................................................................................................................. 124.1.1. Digital Signal Processor (DSP) .............................................................................. 124.1.2. Digital Modulator (DM)......................................................................................... 12

4.2. Radio-frequency stage ................................................................................................... 134.2.1. Frequency Converter (FC)...................................................................................... 134.2.2. Frequency Extension (FE) ...................................................................................... 13

4.3. Channel Controller (CC)................................................................................................ 144.4. Built-in Test Equipment (BITE).................................................................................... 14

5. Emitter unit configuration................................................................................................. 166. Operating and control software ........................................................................................ 17

1. Introduction

The following document describes the results of an applied R&D innovation project, whichproduced an innovative and competitive product that is exemplary of the co-operationsbetween big concerns, universities and small entrepreneurs, taking advantage ofsophisticated technologies and carrying very high intellectual added value.

The project realised by the joint effort of MOD Electronics, Logistics and PropertyManagement Company and Broadband Communications Systems Faculty and WirelessInformation Technology Laboratory of Technical and Economic Sciences University ofBudapest and Sagax Information Technology Management and Advisory Ltd. has producedMulti-Function Communication Simulator equipment that consists of complex hardwareand software elements.

The equipment is developed on the basis of software radio technology that gained groundover the past years. In addition to applying cutting-edge digital processing techniques theequipment’s RF stages represent radio frequency and microwave technologic solutions ofthe highest standards. The Internet-based solution of external control and the object orientedgraphic control program significantly contribute to the high standard of the product. Theadded value in the project is manifest in the development of system-technical principles, theengineering of applied hardware elements in terms of circuitries and mechanical solutions,the planning and implementation of embedded digital signal processing software, thedevelopment of control system and user programs as well as in the test and quality controland quality verification methods.

2. Software radio-techniques

An innovative solution of realising variable radio equipment is based on the concept of so-called “software defined radio”. In this the number of actual radio-frequency subunits (RFoscillators, amplifiers, up- and down-converters, filters designed for the highest bandwidth) isminimal and all signal processing operations (filtering, equalising, modulating, demodulating)are provided by digital processing by means of software. The programmability of stillremaining high frequency stages, in addition to IF and BB signal processing, contributes to agreat extent to achieving full re-configuration. Besides the programmability of high frequencystages the programming and remote control of actually emitting antenna systems is alsofeasible.

Traditional radio sets are generally made for one type of modulation to realise one kind ofcommunication standard (e.g. analogue FM radio-telephones, GSM terminals, GPS receiversetc.), they might occasionally use some different modes of modulations (e.g. communicationreceivers, equipment used in military applications). These equipment are built of non-programmable application specific integrated circuits (ASIC) mostly well suited for their tasksand which define equipment functionalities in an unalterable way.

The family of software radio sets (Software Radio or Software Defined Radio, SDR)represents another approach that by means of programmable elements makes operations invarious (possibly quite different) radio systems possible. Today the need for these are everincreasing, and shall increase, because worldwide there are similar purpose systems withdifferent solutions, and it can also be foreseen – not exclusively due to technical aspects –that quite different systems propagate (e.g. the 3rd generation cellular telephony usesdifferent air-interface in Europe, USE and even Japan). However, users require of their setsto be usable in the widest possible circles (e.g. roaming). On the other hand, the need isthere to increase system inter-operability (e.g. there exist a number of wireless LAN standardand there are more under development). It would again be required of devices to support anumber of standards and of terminals to be interoperable in heterogeneous environment aswell. Similar aspects drive system developers as well as service providers; the introduction ofnew services would become faster and less expensive if there was no need to replacehardware elements but to simply provide for conditions to modify operating software.

But complying with these requirements – first of all in the physical and data-link layers –would need high level programmability of applied components, and on the other hand wouldneed very wide band and of high dynamic range devices, which was not a feature in the caseof traditional ASIC-based radio sets. Application specific circuits have to be replaced byFPGA circuits excellently suitable of high speed signal processing and by programmablesignal processing processors providing for the greatest flexibility. New devices can alsoperform at IF some part of signal processing tasks normally performed at baseband intraditional processors.

The above principles first appeared in military applications. A military purpose radio setdeveloped on the basis of software radio principles can operate on high variety of narrow-and wideband modes of transmissions, and by means of adaptive antenna sets it improvesthe quality of links. It can adopt without any change in circuitry to features such as e.g.applied waveform or data-link protocol (spectrum extension, modulation, error correctingcode, synchronization, interleaving, channel equalization, -framing etc.). Antennacharacteristics (switch-over, adaptive antennae) as well as output power and operatingfrequency can be altered by software means.

Companies working on software radio technologies and those taking part in R&D and theirapplications have established an international forum, which co-ordinates work in the field.The homepage of Software Defined Radio Forum (SDRF) can be accessed at the[http://www.sdrforum.org] address. Almost all significant manufacturers are represented inthis organisation.

A feature of digital radio sets is the point where conversion between analogue and digitalunits is achieved. In structures applied today fully digitised baseband functions is a widelyspread method. In this case (de)modulation method by processed baseband signals isimplemented by means of analogue modulators. Since the quadrature principle provides forimplementing arbitrary modulation process the circuits today in use apply IQ (de)modulatorsbuilt for quadrature-components. The required signal processing performance makes theapplication of general DSPs possible for these functions.

The next step of digitization is the application of digital IF signal processing. In this case boththe generation of CW and the IQ (de)modulation is performed in digital domain. Units withthis kind of functionality cannot be made of DSPs designed for fully general functions.Instead of these, special purpose processors specifically prepared for these functions withmaximized performance can be used. These special purpose processors feature, in additionto (de)modulators, interpolation/decimation and filter functionalities. These have ports toreceive baseband data and for configuration control ports as well as output interfaces.

Figure: Conversion in digital radio sets

Digital signalhandling

Digital basebandprocessing

Digital IFprocessing

Digital RFprocessing

Conversion technologies available today offer ADC and interpolation DAC circuits between75-300 Msps. Signal processing speed of special purpose processors match this andcapable to perform at 75 Msps maximum sampling rate. Since these basic components onlyappeared on market during the last months, there is no significant supply in the market ofsignal processing units representing higher-level integration based on these basiccomponents. This signal processing speed allows for direct applying lower IF bands (e.g.21.4MHz, 30MHz), though the higher bands (e.g. 70MHz, 140MHz, 270MHz) can also beapplied by means of various mirror-bands and on the cost of some decrease in dynamicranges.

The appearance of direct RF digitization in the commercial applications in frequency bandspresently used for mobile information communications services still to be seen, and thissolution cannot be expected in the near future.

3. Equipment functionalities

The Multi-Function Communication Simulator is a software radio emitter equipmentproducing real-time modulated radio-frequency signals as defined by a computer controlsoftware program.

The equipment can be applied to simulate a complex, dynamically changing radio-electronicenvironment. By its means a virtual radio-electronic space can be generated, each importantcharacteristics of which can be changed in a way according to a scenario predefined bycontrol computer.

The communication Simulator covers frequency ranges of 1 – 2500 MHz with 1Hz resolutionand 90 dB dynamics, and can produce modulation modes applied in these ranges.Generated modulation modes extend from narrow band analogue modes (CW, SSB, ISB,AM, FM) to wide band, multi-state digital modulation modes (FSK, PSK, QAM). Theequipment can generate frequency hopping and direct-sequence extended spread spectrumtransmission-mode signals. It also has its source generator for modulators, in which simplesine wave, telegraphic and wire sources, analogue and digital human voice, modem andfacsimile signals as well as digital signal trains and FDM and TDM multiplexed signals arealso included.

Figure: Characteristic modulation formats

Any change in the equipment’s output characteristics can be achieved in less than 1 second.Since the equipment’s internal controller has its own TCP/IP stack the external computercontrol can be provided via a twisted twin-wire Ethernet link even through the Internet. Thecontrol software contains a control panel that can be used to downloading set-ups or to takedirect control over the equipment. Another element of the control software is the scenarioeditor by means of which individual set-ups can be compiled in libraries and a control

scenario can be edited from saved set-ups. A scenario can store information for 24 hours in1-second steps. Emitter sources of the virtual radio-frequency space can be place onplatforms of which locations can be specified in the space. Disposition in space can also bedisplayed by means of a map-based visualization program.

Modulators and sources are used for generating modulated radio-frequency signals. TheCommsim generates all sources and modulator by means of digital signal processor. This,however, does not mean that analogue sources would not be used; only these are alsodigitally represented within the equipment.

Different op modes can be created by interconnecting various sources and modulators. Incases of simpler op modes the notation is identical to that of the applied modulator.

Major emitter parametersFrequency range 1 – 25,000 MHzOutput power max. 0 dBm, min. - 90 dBmModulation methods: - AM, FM, PM analogue

- ASK, FSK, PSK multi-state digital- QAM multi-state digital- FDM, TDM multi-channel multiplexing

Applicable sources: - Single-channel and multiplexed analogue voice- Single-channel and multiplexed digital voice- Single-channel and multiplexed telegraph and wire- Analogue TV signal- Facsimile- Data-modem signal- Pulse- High data-rate digital data- White- and pink-noise sources

Transmission security functions: - High bandwidth fast frequency hopping- High bandwidth direct-sequence spread spectrum

4. Equipment structure

The equipment is configured of a number of subunits. In order to functionally describeCommsim it is divided into three levels. The first one is the control computer platform, which

is followed by the emitters then comes the output summer (combiner) unit.

Figure: Functional model

#1 RF Channel

#2 RF Channel

#16 RF Channel

Σ

External Noise Source

SPDT

Monitor outputfor calibration

SUT

ControlSW

PC

ControlBUS

A: Audio in fromtape recorder

A

A

RF

External RF Source

A

Control computer RF channels Output stage

A possible basic configuration consists of the following sub-units:• Control computer platform• Commsim CS-2500-E emitter unit• Commsim CS-2500-S summer unit

The equipment’s mechanical design and the control program provides for extending thenumber of emitter units up to 16. This is made possible because the PC configurationrunning the control software can control more emitter units via Ethernet HUB, and the outputof emitters can be applied to the output summer.

Figure: Commsim CS-2500-C configuration

POWER CONTORL BITE OUTAF INPUT

CS-2500-E

IP adsress:192.168. 2.102

< >MENU ENTER RF OUT

POWER CONTORL BITE OUTAF INPUT

CS-2500-E

IP adsress:192.168. 2.101

< >MENU ENTER RF OUT

-

Control computer platform

OUT1

OUT2

EXT 1

EXT 2IN 1 - 4 IN 5 - 8 IN 9-12 IN13 -16

Ethernet HUB

CS-2500-E emitter #2

CS-2500-E emitter #1

CS-2500-S summer

Figure: Commsim CS-2500-C configuration (photo)

- -

An RF channel (emitter) unit implemented in Commsim equipment is made of a number ofsubunits. Fundamentally it consists of a baseband unit and a radio unit as well as a channelcontroller unit to provide for controlling the above two.

Figure: Emitter’s functional description

RF Channel unit

FrequencyConversion

Unit(FCU)

ControlBUS

Audioinfrom

taperecorder

RFout

Channel Controller Unit (CCU)

FrequencyExtension

Unit(FEU)

SignalProcessor

Unit(DSP)

DigitalModulator

Unit(DMU)

Baseband Unit (BBU) Radio Frequency Unit (RFU)

BITEinterface

Figure: (Photo of the equipment)

4.1. Baseband unit

The Baseband Unit (BU) consists of two basic assemblies: a digital signal processor and amodulator assembly. Similarly, the Radio Unit (RU) is also divided into two parts. Oneassembly is a frequency converter of which output signal is fed to frequency extensionassembly, where the output frequency is produced.

4.1.1. Digital Signal Processor (DSP)

It is the Digital Signal Processor’s task to generate baseband signals of the various sources.Baseband signals of sources modulate the carrier wave in accordance with preset mode ofmodulation. In addition to generating baseband signals the DSP also produces quadraturecomponents since the modulator applies general quadrature modulator.

The generated signals are applied to modulator via wideband DMA. DSP also has digitisinginput that is needed to generating real-time sources’ signals. In this mode of operation theDSP receives real-time modulating signal by means of ADC chip and then processes it.

(Figure: DSP – SC of DMU block diagram)

Digital Signal Processor (DSP)

DSP

Data

Address

DMA REQ

DMA ACKEXT ADC

RAM BasebandModulationGenerator

I

Q

INT

EXT

DSP Unit

CTRL

Spreading and Converter of the Digital Modulator Unit

Serialport

Serialport

Serialport

Serialport

Spreadingand

SerialConverter

Data

Address

DMA REQ

DMA ACK

Par

alel

DM

A b

ased

inte

rfac

e to

DS

P

Ser

ial i

nter

face

to u

p co

nver

ters

4.1.2. Digital Modulator (DM)

The function of DM is to perform quadrature modulation of baseband quadrature componentsgenerated by the DSP. The entire modulation process in achieved in digital domain andspecial digital up-converter and carrier generator circuitry are applied to the function. Digitalup-converters perform the necessary interpolation and samples are produced on thesampling frequency of numerical controlled oscillator. DM’s output frequency is determinedby the frequency of the programmable oscillator. Digitally produced modulated carrier waveis converted into analogue domain by means of digital-analogue converter located in the DM.

(Figure: Up-converter and CW gen – DM and summing block diagrams)

Up Converter and Carrier generator of the Digital Modulator Unit

Serialport

RAMCoefficientFilter (RCF)

CascadedIntegrator

Comb (CIC) FilterNCO

Serialport

RAMCoefficientFilter (RCF)

CascadedIntegrator

Comb (CIC) FilterNCO

Serialport

RAMCoefficientFilter (RCF)

CascadedIntegrator

Comb (CIC) FilterNCO

Serialport

RAMCoefficientFilter (RCF)

CascadedIntegrator

Comb (CIC) FilterNCO

SCLKDATASDFS

SCLK

DATASDFS

SCLKDATASDFS

SCLK

DATASDFS

OUT

DUC Unit

OUT

OUT

OUT

Digital Modulator and Summingof the Digital Modulator Unit

MOD

MOD

MOD

MOD

OUT

DigitalSumming

Unit

DAC

Modulator Units Digital Summing

OUT

OUT

OUT

DACDIF OUT

4.2. Radio-frequency stage

4.2.1. Frequency Converter (FC)

FC transfers to higher frequency ranges the modulated IF signal produced by the modulator.It applies dual conversion to produce the upper IF.

FC has an input attenuator (IF ATT) by means of which the level of digitally generated IFsignal coming from modulator can be adjusted.

The frequency of applied local oscillators can be programmed by coarse steps; the requiredfine resolution can be achieved by means of fine programming the carrier wave digitallyproduced by the modulator.

Frequency hopping operation mode is also based upon the interoperation of frequencyconverter and the modulator. Fine frequency hopping is provided by means of the modulatorand the wide band hopping by the frequency converter.

Frequency converter also has its micro-controller. Microcontroller performs according tocommand from channel controller the adjustment of local oscillators and input attenuators.Frequency controller is connected to channel controller via a serial interface channel.

4.2.2. Frequency Extension (FE)

FE provides for extending the modulated output signal over the entire frequency range.Desired output frequency is produced in FE by means of mixing the upper IF signal with thesignal of a local oscillator programmable over wide range.

In order to achieve desired output dynamics the FE has a digitally programmable powerdivider, by means of which the required output power level can be set.

FE’s micro-controller provides for communicating with channel controller as well as forprogramming its oscillator and power divider.

(Figure: FC – FE block diagram)

Frequency Conversion Unit

LIFM LIFB

LIFL

HIFM HIFB

HIFL

AMPDigital IFinput

MCUControl

port

-10dBm-10dBm

IF ATT

High IFoutput

Frequency Extension Unit

OM

OL

OLP AMPRF

ATTRF

output

0dBm-20dBm

MCUControl

port

High IFinput

4.3. Channel Controller (CC)

The function of CC is to control each unit of the RF channel in accordance with configurationcommands coming from control computer. It has an Ethernet port to provide for interfacingwith control computer, and four serial ports each connected to subunits of the RF channelunit. There is one more serial port on the CC for transferring the results of built-in testfunctions.

In addition to providing for control the CC also manages the tests performed in RF channelby means of built-in test functions. Test can be performed from control computer or from frontpanel controls.

(Figure: connections of CC – IP address settings)

Connections of Channel Controller Unit

Serialport

Serialport

Serialport

Serialport

ChannelController

Unit

Channel Control

FEU

FCU

MOD

DSP

Ethernet

Serial port

Controlinterface

to PC

BITEinterface

Paralel portDisplay

andfunction keys

IP cím beállítása

4.4. Built-in Test Equipment (BITE)

Each functional unit of the emitter has its own built-in test feature. These tests can be runeither from front panel controls or from control computer. Computer tests can be performedat the control level equipment constituted by devices applied in the system, or via a terminalor terminal software connected to the emitter. By means of self-tests any faulty emitter canbe identified, and, provided that the system controller is well operational, a subassemblywithin a given emitter, which means the smallest non-factory replaceable entity of thesystem. In addition to information on operational performance the self-tests also providesoperational characteristics such as e.g. the current consumption or temperature of individualassemblies.

5. Emitter unit configuration

In designing the emitter unit’s structure complying with environmental and mechanicaldurability standards are taken into consideration. Meeting any requirement is strictly verifiedby various tests.

(Figure: CS-2500-E top view)

Elolap

(Figure: CS-2500-E bottom view)

6. Operating and control software

The operation of the equipment needs the control software running on computer hardware.Software system is basically divided up to a control window application and a scenario editorapplication that provides for tabular and graphic information display. The following figuresshow a characteristic display screen for each application.Emitter unit control window, Scenario editor window, Graphic map display window.

Az adó egység vezérlo panel

Vezérlési forgatókönyv szerkeszto

Térkép alapú grafikus megjelenítés