UWB Antenna at 1GHz

1
UWB Antenna at lt1GHz

• UWB at low-freq is good for thru-wall
  communication and imaging
• Skin depth is large
• Diffraction is prominent
• Antennas with dimension of centimeters are
  electrically small at lt1GHz
• Q (?3)/(antenna size)
• Reactance dominates

6cm Dipole Antenna Zin
Resistance
Reactance
2
UWB Antenna at lt1GHz (cont.)

• Since small antennas are high-Q, they can be deem
  as low-loss 1-port network

3
Small Antenna Modeling
Take small Loop Antenna as an example

• Small antenna ? waveform omni-directional
• E(?,?,R,t) ?(?,?) ? E(?o,?o,R,t)
• Only one resistor in the model
• Waveform across Rrad is equal to that of the
  far-zone E-fields
• E(?o,?o,R,t) ?(?,?) ? V(t-R/c)
• Can estimate radiated E-field in SPICE

4
6cm Dipole Antenna Modeling

• Verification of waveform omnidirectionality
• Identical phase response at all directions
• Identical normalized magnitude response at all
  directions

• 6cm dipole is waveform omnidirectional lt1GHz

Magnitude Response
Phase Response
5
6cm Dipole Antenna Modeling (cont.)

• Capacitance-dominant network
• Normalized E-field and Vrad match well

Vin
6
Large-current Radiator Modeling

• Inductance-dominant network
• Normalized E-field and Vrad match well

Vin
7
UWB Pulser
8
Package Modeling

• Package modeling is important for interface
  circuits
• TQFP is a good candidate
• Cadence PKG is used to generate the netlist

Mutual inductance
9
H-bridge Simulation Results

• Doublet is generated
• Pulse-width 1nS
• Smoothed after low-pass filtering at the receiver

• Meet FCCs rule
• EIRP will increase when PRF(Pulse Repetition
  Freq) increases

VRrad
FCC Mask
Vfiltered
EIRP (dBm/MHz)
Time(ns)
Frequency (GHz)