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 processExcellent repeatability and yieldLow costHigh 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)

Sopt[

Freq

CGN]

freq (50.00MHz to 10.00GHz)

Sopt

pHEM

T_sim

_OMM

IC..S

opt[F

reqC

GN]

pHEM

T_sim

_OMM

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.