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 simulations
LNA1
Cambridge, Dec 2010
Considerations for AA-lo LNA
LNA2
AA-lo LNA
AA-lo LNA:
AA-lo MMIC LNA:
Low loss Baluns.
Matured process
Single ended LNAs.
Excellent repeatability and yield
Overall noise figure should be less
than sky noise.
High transconductance and low noise
Simulated results:
5. LNA1:
1. Two hybrid LNA designs.
2. 2-stage LNAs with
differential input and
single ended output.
3. Enhancement mode
pHEMTs of Avago
Technology
4. Operational from 50MHz
to 400MHz.
•
•
Cambridge, Dec 2010
Low cost
•
•
Gain above 25dB.
NT below 35Kelvin
between 100MHz and
450MHz 20Kelvin at
330MHz.
4V – 121mA drain bias
(at PSU).
P1dBIN point of -23dBm
at 0.4GHz.
Considerations for AA-lo LNA
6. LNA2:
•
•
•
•
Gain above 36.7dB.
NT below 36Kelvin.
P1dBIN is -24dBm at
0.4GHz.
3V – 60mA drain bias
and 0.5V at gate
List of Measured HEMT Samples
Process
Sizes
Different
samples
S-parameter
Samples
Noise
Samples
1
2
3
4
5
6
7
8
9
8
9
4
7
8
6
1
1
3
8x4
9x4
4x4
7x4
8x3
6x3
1x6
1x6
3x6
7x2
5x2
4x2
4x2
8x2
3x2
-
150nm GaAs pHEMT
150nm GaAs mHEMT
130nm GaAs pHEMT
100nm InP pHEMT
150nm GaAs mHEMT
70nm GaAs mHEMT
150nm GaAs pHEMT
100nm InP pHEMT
100nm GaAs pHEMT
Total
52
190
54
9 types
MMIC Parameters:
1. Reproducibility
2. Reliability
3. Yield
4. Future Availability
5. Power, Temperature,
Cost
Cambridge, Dec 2010
Details
Ongoing/Future characterisation work:
1. HEMTs of 2/3 more processes
2. Further Characterisation of 2 of 9 above processes
3. Cryogenic characterisation of HEMTs of shortlisted processes
Considerations for AA-lo LNA
Process considerations
Important parameters:
1.
2.
3.
4.
Noise Measure
Position Gamma Opt in Smith Chart
Temperature dependency
Power efficiency
Cambridge, Dec 2010
pHEMT_sim_OMMIC..Sopt
pHEMT_sim_OMMIC..Sopt[FreqCGN]
Sopt
Sopt[FreqCGN]
Process Investigation based on power efficiency
Loci of Γopt
(0.000 to 0.000)
freq (50.00MHz to 10.00GHz)
Considerations for AA-lo LNA
Temperature Dependency
Process Investigation based on temperature dependency
1.
Temperature fluctuation
0.120
0.300
-50degree C
-50 degree C
-30degree C
varies gain and NT
vital for long observations
3.
30 degree C
60degree C
0.200
0.150
0.100
Optimum biases change
0.080
60 degree C
Transconductance (S)
Temperature stabilisation is
0.100
0 degree C
30degree C
Transconductance (S)
2.
-30 degree C
0.250
0degree C
0.060
0.040
0.020
0.050
0.000
with temperature
-0.50
4.
Temperature stabilisation?
Cambridge, Dec 2010
-1.00
0.000
-0.40
-0.30
-0.20
-0.10
0.00
0.10
0.20
-0.80
-0.60
-0.40
Considerations for AA-lo LNA
0.00
-0.020
0.30
Gate voltage (V)
-0.20
Gate voltage (V)
0.20
Interface with Antenna
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)
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.
Cambridge, Dec 2010
Considerations for AA-lo LNA