cambridge, dec 2010considerations for aa-lo lna dr saswata bhaumik pdra of: dr danielle george the...
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Cambridge, Dec 2010 Considerations for AA-lo LNA
Considerations for AA-lo LNA
Dr Saswata Bhaumik PDRA of:
Dr Danielle George
The University of Manchester
Cambridge, Dec 2010 Considerations for AA-lo LNA
Overview
• Hybrid LNA simulations Performances of LNA1 and LNA2
• MMIC process considerations Reproducibility, Repeatability, Yield, Availability, Power, Temperature
Stability
• Interface with Antenna Investigation of interface between LNA and Antenna is very important
Cambridge, Dec 2010 Considerations for AA-lo LNA
AA-lo hybrid LNA simulationsLNA1 LNA2
Cambridge, Dec 2010 Considerations for AA-lo LNA
AA-lo LNAAA-lo LNA:
Low loss Baluns.
Single ended LNAs.
Overall noise figure should be less
than sky noise.
AA-lo MMIC LNA:
Matured process
Excellent repeatability and yield
Low cost
High transconductance and low noise
Cambridge, Dec 2010 Considerations for AA-lo LNA
List of Measured HEMT SamplesProcess Different S-parameter Noise DetailsSizes samples Samples Samples
1 8 8x4 7x2 150nm GaAs pHEMT2 9 9x4 5x2 150nm GaAs mHEMT3 4 4x4 4x2 130nm GaAs pHEMT4 7 7x4 4x2 100nm InP pHEMT5 8 8x3 8x2 150nm GaAs mHEMT6 6 6x3 3x2 70nm GaAs mHEMT7 1 1x6 - 150nm GaAs pHEMT8 1 1x6 - 100nm InP pHEMT9 3 3x6 - 100nm GaAs pHEMT
Total 52 190 54 9 types
Ongoing/Future characterisation work:1.HEMTs of 2/3 more processes2.Further Characterisation of 2 of 9 above processes3.Cryogenic characterisation of HEMTs of shortlisted processes
MMIC Parameters:1. Reproducibility2. Reliability3. Yield4. Future Availability5. Power, Temperature,
Cost
Cambridge, Dec 2010 Considerations for AA-lo LNA
Process considerationsProcess Investigation based on power efficiency
Important parameters:
1.Noise Measure2.Position Gamma Opt in Smith Chart3.Temperature dependency4.Power efficiency
(0.000 to 0.000)
Sop
t[Fre
qCG
N]
freq (50.00MHz to 10.00GHz)
Sop
tpH
EM
T_s
im_O
MM
IC..S
opt[F
reqC
GN
]pH
EM
T_s
im_O
MM
IC..S
opt Loci of Γopt
Cambridge, Dec 2010 Considerations for AA-lo LNA
Temperature Dependency
1. Temperature fluctuation
varies gain and NT
2. Temperature stabilisation is
vital for long observations
3. Optimum biases change
with temperature
4. Temperature stabilisation?
Process Investigation based on temperature dependency
-0.020
0.000
0.020
0.040
0.060
0.080
0.100
0.120
-1.00 -0.80 -0.60 -0.40 -0.20 0.00 0.20
Gate voltage (V)Tr
ansc
ondu
ctan
ce (S
)
-50 degree C
-30 degree C
0 degree C
30 degree C
60 degree C
0.000
0.050
0.100
0.150
0.200
0.250
0.300
-0.50 -0.40 -0.30 -0.20 -0.10 0.00 0.10 0.20 0.30
Gate voltage (V)
Tran
scon
duct
ance
(S)
-50degree C
-30degree C
0degree C
30degree C
60degree C
Cambridge, Dec 2010 Considerations for AA-lo LNA
Interface between antenna and LNA/balun is crucial for noise and gain ripple.
Consideration must be given to practical implementation.
Options – 1.Direct connection between Antenna and LNA
–Differential Antenna and Differential/pseudo Differential LNA–Single-ended Antenna and Single-ended LNA
2.Balun in the Interface–Differential Antenna and Single-ended LNA (feasible for AA-lo SKA)
Interface with Antenna
Cambridge, Dec 2010 Considerations for AA-lo LNA
Conclusions and Further Work
AA-lo has different LNA design requirements to AA-mid.
HEMTs of 9 processes investigated – 2 processes will be further investigated.
2/3 more processes will be investigated.
Different pHEMT topologies superior to mHEMT topologies for AA SKA (considering factors discussed in previous slides).
Different processes suitable for different frequency bands (AA-lo and AA-mid).
MMIC version of AA-lo LNA has been designed for fabrication.