ARO MUR I K-band Spatial Power Combiner Using Active Array Modules LY. Vicki Chen, PengCheng Jia, Robert A. York PA Workshop, San Diego 2002 Presentation Outline Passive System Antenna array, Higher order mode problem, Performance Amplifier Design Two-stage Amplifier, Flip-Chip IC, CPW-line Power Combiner Design considerations, Performance Conclusions ARO MURI Spatial Power Combining ARO MURI Normal incident/outgoing waves Limited bandwidth in general Easier for monolithic design Challenge in thermal management Tile Approach Parallel incident/outgoing waves Broadband characteristics Good heat-sinking property Consuming more substrate area Tray Approach System Overview
ARO MURI Extended work from the X-Band Spatial Combiner Design Oversized Waveguide Environment TE10, TE20 from 18 to 22GHz Fin-line to CPW line Transition Monolithic Circuit Design Flip-Chip IC Oversized waveguide (TE10,TE20) Gradual transition from WR42 to the oversized waveguide Active Devices Tapered-Finline Antennas Antenna Design Finline to CPW line transitions ARO MURI Design is based on the optimal taper design of the X-band system. Finline to CPW line transitions Eliminate the bond-wires. Klopfenstein Taper Ground Signal Air-bridges are needed to provide good grounding in the middle ground plane. Ground Use HFSS for simulation. Signal Ground AlN substrate CPW line
Reference paper: Design of Waveguide Finline Arrays for Spatial Combining. Submitted to IEEE transaction on MTTs ARO MURI HFSS Simulation PEC PEC metal air Et metal Et By forcing the PMC boundary condition, the even mode does not exist in the system. PEC Fin-line Metal PMC Dielectric Et Waveguide Wall PMC Simulate for 2x4 system. Simplify the problem by applying the boundary conditions. Impedance & Gamma vs. Gap-size Finline CPW Transition Reflection coefficient for the taper design. ARO
MURI Effects of Mounting Grooves Single mode unilateral finline d b d 1 < b 3 The mounting grooves affect the optimal values of many parameters: Operating frequency Effective dielectric constant Substrate thickness Small slots are affected more severely than broader slots. short circuit grooves Reflection Coefficient (dB) 0 -10 -20 -30 d The depth of the short circuit grooves has huge effect on the return loss -40 S11 (dB) - a S11 (dB) - b -50 18 19 20 d d=/5/5
d=/52/15 21 22 23 Frequency (GHz) 24 25 26 Combining Efficiency Symmetrical loading is necessary to avoid TE20 mode and achieve efficient combining. ~ 76% combining efficiency is achieved. P -P (G-1)Pia a = oa ia = Pdc a Pdc a sys a L o Measurement for one card (asymmetrical) and two cards (symmetrical) system 0 ARO MURI for high gain 6 cards (4x6 system) 50ohm Termination & Through-line measurement 0 -10 -10 -20 -20
20.5 Frequency (GHz) 21 21.5 22 Two-Stage Amplifier Design Flip-Chip Technology using CPW-line Thermal Management FCIC Gain Enhancement pre-amplifier Optimal load matching ADS/Momentum Simulations Pre-amp Design Challenges Substrate modes are excited easily. Biasing circuitry is complicated. Good grounding should be maintained. 13.5mm Ground Signal 8.56mm Ground Signal Ground ARO MURI Power device Two-Stage Amplifier Design CPW-line Substrate Mode Substrate mode is excited easily! Increasing the substrate thickness or reducing the width of the CPWline could reduce the effect of the substrate mode. AlN > eff > Air eff
Quasi-TEM ARO MURI AlN S21(dB) of the Two-stage Amplifier 20 20 10 15 0 10 -10 -20 -30 -40 5 10 15 20 Frequency [GHz] S21 (dB) - thin line 5 S21 (dB) - substrate mode S21 (dB) - with spacer 25 30 S21 (dB) - wide line 0 12 13 14 15 16 17 18
Frequency [GHz] 19 20 Two-Stage Amplifier ARO MURI Performance Return loss <-10dB for the operating frequencies. 27.3dBm output power with 20% PAE and 9.5dB power gain was obtained. Thin film (on-chip) and chip capacitors were both needed for biasing circuitry. 20 30 25 10 25 0 20 Pout 20 -10 -20 15 PAE 15 10 -30 S11 MAG [dB] S21 MAG [dB] S22 MAG [dB] -40
10 -50 14 15 16 17 18 19 20 Frequency [GHz] 21 22 5 5 Gain 6 8 10 12 14 16 Pin (dBm) 18 0 20 Combiner Performance Two Cards Measurement ARO MURI Small Signal Performance & Power Measurement @ 18GHz Two cards system (8 amplifiers) with 34dBm output power. 12.5% PAE 62% Combining Efficiency (optimal: 76%) Phase difference between cards degrades the output performance the most. 35
20 20.5 Frequency [GHz] 21 21.5 22 5 18 20 22 24 26 Input Power (dBm) 0 28 Measurement ARO MURI ARO MURI Statistical Errors in Arrays Output voltage: G2 Combiner A Splitter G1 Bout Bout
AG 0 N N r (1 G )e i i 1 ri Pe ri = 0 or 1 GN Output Power: i ji Probability of device survival P0 ( AG0 ) 2 2 P Bout Change in power due to errors: P 1 2 P0 N Ensemble average: N N ri rj (1 Gi )(1 G j )e j ( i j ) i 1 j 1 P
2 Pe e P0 2 1 N P 1 G2 e 2 2 e Pe Phase errors and device failures are most important in large combiners Ref: R. York, Some considerations for Optimal Efficiency and Low Noise in Large Power Combiners, IEEE Trans. Microwave Theory Tech. Combiner Performance 6 Cards Measurement ARO MURI Six Cards System (6x4) 2 devices failed. 10dB small signal gain. Absorbing material were added to prevent the in-band oscillations. Each cards was biased individually. Improper grounding could result in oscillations. Some chip resistors were added to prevent bias-line oscillations. 10 Signal cross-talk between bond-wires could induce in-band oscillations 5 0
S11 [dB] - 6 cards S21 [dB] - 6 cards S22 [dB] - 6 cards -5 Absorbing Material -10 -15 -20 -25 -30 18 18.5 19 19.5 20 20.5 Frequency [GHz] 21 21.5 22 Phase Noise Reduction Amplifiers degrade phase noise due to internal nonlineariities which up convert low-frequency amplitude and phase noise to the carrier Combiner Splitter G G in input noise fluctuation i amplifier noise contribution out total output noise fluctuation
G ~ out 2 ~ in 2 ARO MURI 1 2 ~ N 0 -20 amplifier combiner -40 Noise contributed by the ensemble is reduced by 1/N (-13.4dB) compared with a single amplifier -60 -80 -100 -120 -140 1 10 100 Frequency (Hz) 1000 Power Measurement
Non-uniform excitation profile 37.3dBm output power @18GHz was obtained. Non-uniform excitation. Chip resistors were added for biasline stabilization. Combining Efficiency: 53.7%. 40 ARO MURI Pin =/5 Pin =/5 Pin =/5 Pin =/5 300 35 31.08dBm 29.3dBm 24.12dBm 20.8dBm 250 30 Pout Gain 25 200 20 150 15 10 100 5 0 20
22 24 26 28 Pin (dB) 30 32 34 50 1 2 3 4 Card number 5 6 Conclusion ARO MURI Passive combiner achieved 76% combining efficiency. 34dBm output power has been obtained for 2-tray system. 62% combining efficiency was obtained. 37.3dBm output power has been obtained for 6-tray system. 53.7% combining efficiency was obtained. Phase noise reduction compared with single amplifier. Stabilization should be maintained for all frequencies.
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