10 June 2002 Paul Lilie Advisory Committee1 EVLA Front Ends

10 June 2002 Paul Lilie Advisory Committee2 1 – 50 GHz Coverage In 8 Bands Dual Circular Polarization

10 June 2002 Paul Lilie Advisory Committee3 OMTs Quad-ridge Bøifot Symmetric Junction

10 June 2002 Paul Lilie Advisory Committee4 Bands 1 – 2, 2 – 4, 4 – 8 Quad-Ridge OMT & 90º Hybrid Design Scaled for frequency Commercial Stripline Hybrids

10 June 2002 Paul Lilie Advisory Committee5 Bands 12 – 18, 18 – 26, 26 – 40 Corrugated Phase Shifter Bøifot OMT 18 – 26 GHz in Production Now.

10 June 2002 Paul Lilie Advisory Committee6 Band 8 – 12 Quad-ridge or Bøifot; depends on size. Band 45 – 50 Sloping Septum, in Production Now.

10 June 2002 Paul Lilie Advisory Committee7 Cost per Receiver

10 June 2002 Paul Lilie Advisory Committee8 Advice Sought: Octave Bandwidth Quad-Ridge OMT “Headroom” MMICS

10 June 2002 Paul Lilie Advisory Committee9 Quad-Ridge OMT Critical Areas Octave Bandwidth 2:1 at ~20 dB has been done. Higher Modes Above cutoff: affect beam Below cutoff: “suckouts” TE21 L most troublesome

10 June 2002 Paul Lilie Advisory Committee10 Quad-Ridge OMT Design Approach: Circular-to-Quad-Ridge Waveguide: treat as impedance transformer Quad-Ridge to Coax: design for match

10 June 2002 Paul Lilie Advisory Committee11 Q-R OMT Modes Trapped Modes Q ~1000 Coupling fairly weak, ~ -25 dB Effect on beam? “one-pass” loss ~ dB

10 June 2002 Paul Lilie Advisory Committee12 Shorting Pins at  /4 Short out TE11 modes Pass TE21 L mode to absorber Assures one-pass for TE21 L

10 June 2002 Paul Lilie Advisory Committee13 Headroom What is it? How Defined? (TOIP? 1dB? 1%?) How Measured? How Much Do We Need? “As much as we can get, or...”

10 June 2002 Paul Lilie Advisory Committee14 Headroom Against What? Narrow-Band Pulsed Noise-like Component Variations

10 June 2002 Paul Lilie Advisory Committee15 How Much Can We Afford? Dollars Tsys Size and Power Dissipation

10 June 2002 Paul Lilie Advisory Committee16 MMIC Solution for a High Dynamic Range “Solar” Capable Receiver  Ka-Band  LO Ref GHz x GHz 25 dB 35 dB 25 dB GHz Po=+10dBm (?) Level 10 (?) IF Out 8-18 GHz GHzLevel 10 (?) Po=+10dBm (?) MMIC’s GHz Noise Diode Pol Step Att PIN Switch 15 dB Step Att SPDT Switch MMIC’s 15 dB Step Att SPDT Switch MMIC’s GHz LNA HNA Post-Amp NF < 5 dB