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Time Domain Far Field Antenna Measurements Without Anechoic

ChamberTransmitting Antenna Antenna Under Test

1x-Positioner

DigitalSamplingConverter

Personal Computer

Pulse GeneratorMainframe

Pulse Generator

Head

SamplingUnit

DC-26GHz

Antenna Pattern

Adjacent Reflecting Objects

Preface

Two different methods are used for antenna pattern measurements: Frequency Domain measurement (FDM) and Time Domain measurement (TDM). Time Domain method allows to obtain substantial advantages:

• Ability to measure antenna pattern for different frequencies simultaneously using Fourier transform. In this case the full measurement requires less time.

• Elimination the reflections from adjacent objects using sufficient time window;

• Possibility to acquire measurement signals that are asynchronous with interferences from GSM base stations, Radio and TV transmitters and etc. Both latter advantages enables to carry out measurements without anechoic chamber:

In TDM the Pulse Generator generates short pulse with duration about 30 ps. Such pulse enables to measure in frequency band from DC to 26 GHz. Signal from Pulse Generator is applied to transmitting antenna. Signal from receiving antenna (antenna under test) which is located on positioner is applied to one channel of sampling scope. During antenna pattern measurement in TDM for various orientation angles the pulse signal received by receiving antenna is recorded and its spectrum is calculated using Fourier transform.

Shevchenko str. 16, LT-03111 Vilnius-09, Lithuania Tel.: +370 5 2135404; fax: +370 5 2333816; e-mail: info@geozondas.com; URL http://www.geozondas.com/

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Technical Specifications

Name of parameter Value Bandwidth 0.85 ~ 26 GHz Transmitting and Receiving antennas located in a room. Distance between antennas

Far field criterion

Dynamic range of side-lobe measurement level > 50 dB Antenna Pattern measurement error at a level -30 dB no more than 0.5 dB Bandwidth of AUT for Time Domain method ≥ 10 MHz Displayed Frequency Step ≥ 1 MHz Maximum signal acquisition time 1 s Angle resolution in Azimuth and Elevation planes 0.02° Software enables PC to realize:

- Control of all sampling converter modes; - Data acquisition from the sampling converter, data storage and displaying in real time;

- Data reception from the positioner: - To measure Antenna Pattern, Gain, Polarization features,

Phase Center location

- Friendly user interface allowing to draw gain and antenna pattern and show angles value on PC display during measurement;

- Digital signal processing; - Storage in PC memory and printing of observed and calculated data;

Software is created in LABVIEW environment (National Instruments Co., USA)

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Components And Units

SD-203T Digital Sampling Precision Converter with SU 3126M Sampling Head

The Three-Channel Digital Sampling Converter SD203T is a part of Antenna Test Area and intended for measurement of parameters of broadband repeated signals in frequencies range up to 26 GHz with internal and external triggering.

Digital Sampling Converter can operate together with personal computer IBM Pentium so its versatile characteristics are provided by all intelligent means of up-to-date computer and threshold parameters of the PC conjugated analog devices.

In particular the registered waveform can be subjected to any processing and filtering in time and frequency domain.

Short Specifications

Number of channels 2 Bandwidth 0.1 ~ 26 GHz Time window including delay 200 ns Sampling frequency 1 MHz Temperature range (+5 ~ +40) °C Power Supply 90 ~ 260 V

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Pulse generator Mainframe GZ1106DL1 with built-in GZ1192DL Analog Delay Unit with RS232 Computer Control Interface

The pulse generator mainframe is designed for placement different plug-in (type

A) or built-in (Type B) units and their supplying with power voltages. All units are compatible with SD203T measurement system. Application fields of GZ1106DL1 are: optical, microwave, radar and GPR systems

Short Specifications

Analog Delay 0÷11ns Temperature range (-10 ~ +45) °C Power Supply 90 ~ 260 V

. Generator Head GZ1117DN-25

The Pulse Generator Head GZ1117DN-25 is Pulse Former driven from

Generator Mainframe GZ1106DL1 (GZ1105) and designed for generation of negative high speed electrical pulses

Application fields of GZ1117DN-25 are: optical, microwave, radar and GPR systems.

Short Specifications

Pulse Amplitude ≈ 25 V Duration (on half-amplitude) ≈ 30 ps

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Transmitting antennas set

Short Specifications of P6-23M

Antenna Type Ridged Horn Bandwidth 0,85-18 GHz SWR on the antenna output <1,5 Gain

0,85 GHz 8 dBi 18 GHz 28 dBi

Aperture 351x265 mm Short Specifications of P40

Antenna Type TEM Horn Bandwidth 10-40 GHz Gain

10 GHz 0 dBi 40 GHz 15 dBi

Aperture 100x70 mm

Transmitting Antenna Tripod

Manual Control Azimuth, Elevation and Polarization

Angle resolution 1 ° Dimensions 1780xØ800

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1x-Positioner GZPU- 1 with Control Unit 2x-Positioner GZPU- 2 with Control Unit 3x-Positioner GZPU- 3 with Control Unit

Rotation angles in Azimuth and Polarization Planes

0 ~ 360°

Rotation angles in Elevation Plane ±95° Angle resolution 0.02 ° Load capability, up to 500 kg Bending moment, up to 600 N⋅m

Options:

Rotary Joint for all axes: DC~ 26 GHz Positioner control cables 5 m. Safety package for Sampling Head Foam AUT Holder (Pylon) Height ≈ 1m.

Cables and coaxial devices set

PC Requirements PC: Intel Pentium IV 2400 MHz/256 MB RAM/ 40 GB ULTRA ATA HDD/CD-ROM/LAN 10/100/ 2LPT/2COM Monitor: 17’, Color printer

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Software

The software for operation control of all system

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The software for operation control of digital scope