Novel Dual Balun / Coupler Is Space Saving Semi-Lumped.

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1 The use of a traditional coupler as a Balun has many advantageous. A single design can be adapted for both Class A applications and Push Pull applications. The method is best suited for narrow to moderate bandwidth circuits. The traditional coupler relies on a differential 9 degree signal split while the Balun is designed for a 8 degree split. The conversion of the coupler to the Balun requires an additional delay in the direct coupled leg. It is the practical application of this method that is the subject of this note. CLIN ZE= 23 Ohm ZO= 9.8 Ohm EL= 9 Deg F= 2.6 GHz P= 3 P= 4 Response And BandWidth Of A Coupler The coupler (Right) response with slight over coupling for increased bandwidth Direct Port Coupler Two Couplers Back to Back Center Frequency Mag Max 35 2 S2AndS Swp Max 3.5 Coupled Port degrees 5 Polar plot of the coupler showing the lead lag phase response Per Div Swp Min GHz -6 DIAMOND ENGINEERING 484 Main Street #6 Ph (53) Fax (53)

2 The ideal low pass filter topology offers a reasonable 9 degree phase shift and requires much less re estate than the traditional delay line. When the Low Pass transfer function pole is properly placed the insertion loss is minimum while the phase goes through 9 degrees. The second step in the process is to convert the ideal low pass topology to a distributed semilumped structure. Time Delay Filter Ideal Lumped Element Phase Shifter IND ID= L L= 3.8 nh ID= C ID= C2 Ca=.65 Insertion Loss (db) Practical Semi-Lumped Ideal (Below) The phase andmagnatude plots for both the ideal and semi-lumped low pass phase shifters -.5 Mag Max Swp Max MSUB Er= H= T= Rho= Tand= ErNom= Name= mil.5 mil FR4 A semi-lumped topology derived from the ideal low pass time delay filter Per Div Swp Min GHz ID= TL W= w mil L= L mil Wire ID= IC L= 265 mil Dia= 5 mil 2 w=32.3 L=89.4 ID= TL2 W= w mil L= L mil DIAMOND ENGINEERING 484 Main Street #6 Ph (53) Fax (53)

3 2 CLIN ZE= 23 Ohm ZO= 9.8 Ohm EL= 9 Deg F= 2.6 GHz 3 P= 3 P= 4 4 SUBCKT ID= S NET= LowPass 2 (Top Right) The simulated amplitude response for the coupler balun. The classical response is altered at frequencies beyond the coupler center frequency. The brown trace is the thru loss for a cascade of two such baluns showing the overall response band-width constriction. (Middle Right) The overall phase differential between the coupled port 4 and the direct port 2. The Balun makes +/- 5degrees balance from 2.5GHz to 2.7GHz ( an 8% BW) Prototype Time Delay Filter constructed from semi distributed and lumped elements Balun Measured Response Cascaded Thru Loss Direct Phase Delta Coupled Phase Delay Measure Amplitude Response DIAMOND ENGINEERING 484 Main Street #6 Ph (53) Fax (53)

4 IND ID= L L= 3.8 nh Precision Distributed Ckt. EVOLUTION OF THE TIME DELAY LOW PASS FILTER Wire ID= IC L= 265 mil Dia= 5 mil 2 ID= C ID= C2 ID= TL W= w mil L= L mil w=32.3 L=89.4 ID= TL2 W= w mil L= L mil Ca= Insertion Loss Multi-Layer Fr4 with ground plane removed below High L line Coupler Balun Delay Eqn Delta Eqn Delta2 All Distributed CouplerBalun Semi Distributed CouplerBalun DIAMOND ENGINEERING 484 Main Street #6 Ph (53) Fax (53)

5 Precision Distributed Ckt.Measured Response Circuit Layout For Time Delay Correction Scheme For Precision Filter With Reference Line Differential Phase And Amplitude S-Parameter Extraction SUBCKT ID= S NET= Filter 2 NEG2 ID= N NET= FilterCalThru 2 (-) Backside Ground Plane Removed Under Hi Z line Simulations Raw Measured Extracted MeasuredPhase Extracted Filter Phase Loss Profile DIAMOND ENGINEERING 484 Main Street #6 Ph (53) Fax (53)