# Presentation: 402129

## Assessment of Ultrawideband and Global Positioning System Compatibility

- Assessment of Ultrawideband and Global Positioning System Compatibility

- Randy Hoffman and Mike Cotton
- ISART    March, 2002

## Contents

- Objectives, Test Setup, and Measurement Methodologies
- Ultrawideband (UWB) Parameters and Characteristics
- Interference Results

## Project Objectives

- Primary Objective: assess the interference potential of UWB signals to GPS receivers.
- Secondary Objective: Identify GPS receiver performance metrics and establish repeatable measurement methods.

## Test Setup - Conducted

## General Conducted Measurement Methodologies

- Metrics
- Loss of lock
- Satellite reacquisition time
- Associated performance criteria
- Maximum UWB signal power below loss-of-lock for which the receiver can regain satellite lock
- Monitor: pseudorange, cycle slip, position,C/N, phase lock, DOP, delta-pseudorange, accumulated Doppler cycles, Doppler

## GPS Receivers

## UWB Parameters

- Power levels – peak vs. average
- Pulse shape/width
- Pulse repetition frequency
- Pulse spacing
- Gating

## UWB Pulse Spacing

## Gating

## UWB Signal Parameters

## UWB Spectral Characteristics

## Amplitude Probability 

## APD Characteristics

- Constant Amplitude

- Gaussian Noise-like

- Impulsive

## Results

- Characterization of single-source UWB signals
- GPS-performance trends due to single-source interference

## APDs of Single-Source UWB Signals

- 2 Bandwidths – 3 MHz and 20 MHz
- Composite plots
- Across pulse spacing modes for specific PRF values
- Across PRF ranges for specific pulse spacing mode

## APDs of 20-MHz PRF UWB Signals Measured in a 3-MHz Bandwidth

- Constant-amplitude
- Noise-Like
- Gating
- Peak-to-Average

## APDs of 100-kHz PRF UWB Signals Measured in a 3-MHz Bandwidth

- Low PRF  Impulsive
- Resolved UWB pulses
- Gating decreases the
-   percentage of time the
-   signal is on

## APDs of Absolute-Reference Dithered UWB Signals Measured in a 3-MHz Bandwidth

- Higher PRF  Gaussian

## UWB Categorization

## Measurement Procedure

## Trends

- Spectral lines are particularly invasive
- Impulsive signals cause little interference
- Higher PRFs have a greater impact
- Dithering can produce effects that are more Gaussian noise-like
- Gating reduces the impact of interference

## Break Lock:  Rx 1, Non-Gated

## Pseudorange Precision: Rx 1, 50%-ARD

## Trends

- Observational results are correlated to BL and RQT.
- RQT has been found to be the most sensitive parameter for identifying interference effects on the receiver.

## Rx 1, 5-MHz PRF, 50%-ARD, Non-Gated

## SUMMARY

- Measurement Approach
- UWB Characteristics
- Interference Trends Related to UWB Characteristics

## Contact Information:Institute for Telecommunication Sciences

- J. Randy Hoffman
- 303/497-3582
- rhoffman@its.bldrdoc.gov
- Michael G. Cotton
- 303/497-7346
- mcotton@its.bldrdoc.gov
- Robert J. Achatz
- 303/497-3498
- rachatz@its.bldrdoc.gov

- _Mailing address_:
- U.S. Department of Commerce
- 325 Broadway NTIA/ITS
- Boulder, CO 80305
- _Web address for online report_:
- http://www.its.bldrdoc.gov/
- 	click on <Online Publications>
- 	Scroll down to NTIA Report 01-384

## Broadband Noise Power

- Broadband noise accounts for:
- Sky noise
- Cross-correlation noise
- Other satellite signals
- Setting  of broadband noise level based on ITU recommendation for minimum C/No required for  GPS satellite acquisition. (set at –93 dBm/20 MHz)
- Supported by ITU simulations for worst-case GPS cross-correlation noise.

## Doppler Frequency of SV25

## Slide 30

## Spectral Line Alignment

## Aggregate Scenarios

## Spectral Effects of Gating

## Break Lock: Rx 1, Gated