electronic beamwidth control principle meta materials

1. Electronic BeamWidth Control Principle
Samuel Cherukutty C
208114018
M.Tech

2. Quick Recap

Problems With LW antennas

Frequency Scanned

No broadside radiation and continous scanning
capability

Require fixed frequency operation for effective
channelization

Not that good solutions
− Horn's antenna using diodes as switch
− Maheri's antenna using dc magnetic field tuning

Good Solution
− Varacter Diode BE LW antenna

3. Varacter Diode BE LW antennas

Uses Varactor diode

Control beamwidth by varying reverse bias
− Continous beam steering
− Beam-width control by non uniform bias distribution

Advantages
− Only 1 radiating element
− Simple and compact feed mechanism
− Not necessiating any phase shifters

4. Electronic Scanning Principle
 θ MB
= θ MB
(β)
− For antenna
 β = β(ω;LR
,CR
,LL
,CL
)
− For CRLH MTM
 θMB
= θMB
(ω)
 θMB
= θMB
(V)

5. Electronic Beamwidth Control Principle

Electronic Scaning
− Bias Distribution is
uniform
− Results in periodic
structure(uniform)
− Incremental length radiate
to same direction-max
directivity

Electronic Beamwidth Control
− Different cell radiate at different
angle
− Beamwidth increased( via
superposition)
− Control beamwidth
− Bias progressively unifrom
from backfire to endfire

6. The Structure

2 Series and 1 Shunt
varactor diodes for
− Wide scanning range
− More degrees of
freedom
− Anodes of varactors are
grounded for simpler
bias
− Different… but with
similar performance

7. The Analysis
 (CLvar
andCRvar
) decrease
exponentially with
increasing reverse bias

Z(V)and Y (V) decrease (at
typically low voltages) as V
increases

cos(βp)=1+Z(V)Y(V)1 as V
increases,β→0

Main beam angle steere d
broadside with increasing
voltage

Observed as

8. The Measurement

Voltage above
3.5v results in
backward
radiation(uniform
bias)

Increased
backward
radiation with
nonuniform 5 →

Large insertion
loss
− Radiation
leakage
− Resistance
loss
− In varactors
− Gain 18 db
brodside
− S11
= -12 → -8
db

9. THANK YOU!!!!

10. THANK YOU!!!!