UWB Antennas & Measurements Gabriela Quintero MICS UWB Network Meeting 11/12/27
Outline UWB Antenna Analysis Frequency Domain Time Domain Measurement Techniques Peak and Average Power Measurements Spectrum Analyzer Settings Fourier Series Fourier Transform UWB Measurements
Outline UWB Antenna Analysis Frequency Domain Time Domain Measurement Techniques Peak and Average Power Measurements Spectrum Analyzer Settings Fourier Series Fourier Transform UWB Measurements
UWB Antennas Impulse radio UWB pulse (3.1 1.6 GHz) MICS pulse (4 4.5 GHz) Time and frequency domain Analysis Still with basic antenna architectures Monopole Vivaldi
Time and Frequency Domain Two different softwares used to characterize the antennas Ansoft HFSS FD Frequency Sweep at all frequencies Parameters in FD (S11, Gain, E-field, etc.) CST Microwave Studio TD Select the pulse BW Parameters in FD (S11, Gain, etc.) E-field in TD
Frequency Domain Tx Rx Transfer Function - S 21 Relates the output voltage with the input jωr voltage c V ( ω) = H( ω) V ( ω) e r Can be derived from the Friis Transmission Equation t 2 1 1 λ (, ) (, ) ˆ ˆ cdt cdr t r t θt φ 2 t r θr φr ρt ρr P ( )( ) r 2 2 = e e Γ Γ Pt 4π R D D And obtain V ( ) ( 2 1 ) r ω λ = ecdt S11 Et ( ω, θt, φt ) V ( ω) 4πR t
Frequency Domain Tx Rx HFSS Simulation S11 E-field Matlab Transfer Function Rx Pulse TD IFFT Rx Pulse PSD Pulse PSD
Monopole System Tx Rx -5 Return Loss S11 Simulated Measured 1.9 Normalized Magnitude Simulated Measured -5 Phase [radians].8-1 -1.7-15 Magnitude [db] -15-2.6.5.4-2 -25 TF S21-3 -25.3-35 HFSS NWA -3-35 2 4 6 8 1 12 14 16 18 2 Frequency [GHz].2.1 5 1 15 2 Frequency [GHz] -4-45 -5 5 1 15 2 Frequency [GHz] 2 Power Spectral Density 1 Input Vs. Output pulse (normalized) Rx + Tx Pulse PSD Gaussian Pulse [db] -2-4 -6-8 -1-12 2 4 6 8 1 12 Frequency [GHz] Input Simulated Measured Gaussian Pulse.5 -.5-1 1.5 1 1.5 2 2.5 3 3.5 4 4.5 Time [ns] Input Simulated Measured Rx + Tx Pulse 2.8 MICS Pulse, [db] -2-4 -6-8 -1 MICS Pulse.6.4.2 -.2 -.4 -.6 -.8-12 2 4 6 8 1 12 Frequency [GHz] -1-1 1 2 3 4 Time [ns]
Vivaldi System Tx Rx -5 Return Loss S11 Simulated Measured 1.9 Normalized Magnitude Simulated Measured -5 Phase [radians].8-1 -1.7-15 Magnitude [db] -15-2.6.5.4-2 -25 TF S21-3 -25.3-35 HFSS NWA -3-35 2 4 6 8 1 12 14 16 18 2 Frequency [GHz].2.1 5 1 15 2 Frequency [GHz] -4-45 -5 5 1 15 2 Frequency [GHz] 2 Power Spectral Density 1 Input Vs. Output pulse (normalized) Rx + Tx Pulse PSD Gaussian Pulse, [db] -2-4 -6-8 -1-12 2 4 6 8 1 12 Frequency [GHz] Input Simulated Measured Gaussian Pulse.5 -.5-1.5 1 1.5 2 2.5 3 3.5 4 4.5 Time [ns] Input Simulated Measured Rx + Tx Pulse 1 2.8 MICS Pulse, [db] -2-4 -6-8 -1 MICS Pulse.6.4.2 -.2 -.4 -.6 -.8-12 2 4 6 8 1 12 Frequency [GHz] -1-1 1 2 3 4 Time [ns]
CST: Monopole Antenna E-plane H-plane 4.25 GHz 6.85 GHz
CST: Vivaldi Antenna E-plane H-plane 4.25 GHz 6.85 GHz
Time Domain Monopole Vivaldi 1 UWB Pulse 1 UWB Pulse.5 Input Pulse E-field at 8.5 Input Pulse E-field at 8 -.5 -.5-1.5 1 1.5 2 2.5 3 3.5-1.5 1 1.5 2 2.5 3 3.5 4 1 MICS Pulse 1 MICS Pulse.5.5 -.5 -.5-1 2 4 6 8 1 12 14 16-1 2 4 6 8 1 12 14 16
Time Domain Fidelity Factor Measures the faithfulness with which a device reproduces the time shape of the input signal. f(t) = Input signal at antenna terminals r(t) = Radiated E-field in time domain The signals are normalized to have unit energy r( t) and f() t rˆ( t) = r( t) 2 dt 1/ 2 fˆ( t ) f() t = 1/2 2 dt
Time Domain The fidelity parameter, F, is determined by the peak of the cross-correlation function of the signals F = max fˆ ( t) rˆ ( t+ τ ) dt τ
Time Domain Input signal CST Simulation Fidelity Factor E-field (t,θ, φ)
Time Domain Monopole Fidelity Factor Vivaldi Fidelity Factor 3-3 UWB Pulse MICS Pulse 3-3 UWB Pulse MICS Pulse 6-6 6-6 9 1.9.8.7-9 9 1.9.8.7-9 12-12 12-12 15-15 15-15 ±18 ±18
Outline UWB Antenna Analysis Frequency Domain Time Domain Measurement Techniques Peak and Average Power Measurements Spectrum Analyzer Settings Fourier Series Fourier Transform UWB Measurements
MEASUREMENTS Average Power Peak Power E = P avg P Pτ eff τ = T eff = P avg T
MEASUREMENTS
Spectrum Analyzer RBW VBW Scan Time
Spectrum Analyzer Line Spectrum Pulse Spectrum 1 B> or B>PRF T A pulse repetition rate equal to the resolution bandwidth is the demarcation line between a true Fourier-series spectrum, where each line is a response representing the energy contained in that harmonic, and a pulse or Fouriertransform response. Agilent Spectrum Analyzers Series. Application note 15-2 pp. 32
Line Spectrum
Line Spectrum All individual frequency components are resolved. Line spacing is 1kHZ = PRF Spacing of sidelobe minima is 1kHz = The amplitude of each line will not change when RBW is changed, as long as RBW<.3PRF 1 τ eff
Line Spectrum Pulse Desensitization Only valid for Fourier line spectrum. τ eff αl[ db] = 2log1 = 2log1 T Pavg [ db] = 1log 1( τ eff PRF) P peak ( τeff PRF )
Pulse Spectrum It s a combination of time and frequency display. The lines that form the envelope are pulse lines in time domain. Each line is displayed when a pulse occurs. Frequency domain display of the spectrum envelope. The amplitude of the envelope increase linearly as RBW increases. (As long as RBW <.2/ τ eff ).
Pulse Spectrum -3dBm CW carrier modulated by a pulse train with a PRF of 1Hz, τ eff = 1µs and RBW = 1kHz =.1/ τ eff
Pulse Spectrum In Figure 23, we lost the linear relationship between bandwidth and display amplitude RBW >.2/ τ eff. The resolution of the sidelobes is lost to a great extent. In Figure 24 RBW = 1/ τ eff, we get a display with an amplitude practically equal to the peak amplitude of the pulsed signal.
Pulse Spectrum Pulse desensitization correction factor α [ db] = 2log1( τ K RBW ) K p = B imp RBW K = 1.617 for Agilnet ESA Series 856x or 859x eff
Average Power FCC Definition The average limit is 5 uv/m, as measured at 3 meters with a 1 MHz resolution bandwidth (RBW). Equivalent to an EIRP of -41.25 dbm/mhz EIRP [dbm/mhz] -4-45 -5-55 -6-65 -7-75 FCC Indoor Spectral Mask -8 2 4 6 8 1 12 Frequency [GHz]
Average Measurements If 1 khz > VBW >1 Hz Video averaging should be used in conjunction with peak hold. If NO dithering or PPM Line spectrum setting (VBW RBW) RBW <.3 PRF Average level = highest line in the emission line spectrum
Average Measurements If dithering or PPM True pulse spectrum settings A pulse desensitization correction factor would be added to the measurement to obtain a peak level. The average is calculated using the duty cycle factor in db P P avg peak ( τ PRF ) [ db] = 1log 1 eff
Peak Measurements pp. 174
Peak Measurements Peak level when measured over a bandwidth of 5 MHz 5MHz widest victim receiver that is likely to be encountered. Peak measurements based on a 5 MHz (resolution) bandwidth may not be feasible. The widest available RBW that can be employed for peak measurements is 3 MHz.
Peak Measurements
Peak Measurements Peak emission level of dbm/5 MHz = 58mV/m at 3 meters is adopted. Equivalent to: A peak EIRP of -24.44 dbm/3 MHz Peak field strength of 3.46 mv/m at 3 meters with a 3 MHz RBW.
Rules of Thumb P avg No dithering or PPM P avg Dithering or PPM Peak Interference Power Line Spectrum RBW<.3PRF Pulse Spectrum.1 1.5 PRF < RBW < τ eff 1 scan time[s/div] PRF[Hz]
QUESTIONS?