Baluns, Balance, and Differential Signaling Doug Jorgesen|April 2, 2020 Why Balance? For Signal Cancellation Eliminate unwanted signals without filtering. Balanced Mixers Differential Signaling Differential Circuits Isolate ports and suppress Eliminate common mode noise Eliminate even harmonic even order spurious products and IP2 products Marki Microwave Inc. 3 Power Combining Quadrature In Phase Maximize Power Phase Eliminate Reflections • Increases power handling, linearity, or power generation • Increases linearity or power handling • Usually lowest loss for broadband applications • Improves Return Losses Out of Mixed Eliminates Input Signal for Phase Eliminates Noise and Harmonics Phase Harmonics • Increases linearity and power handling • Useful for gathering converted signals • Eliminates common mode and even harmonics Used in mixers, doublers, quadruplers, etc. F 2F F 2F Marki Microwave Inc. 4 What does a balun do? Digital Data Single Frequency A Balun Creates Digital Data Equal and Vbalanced Amplitude Opposite Signals Positive/0°/ Balance Unbalanced/ Non-inverted Vunbalanced Single Ended/ Balanced/Differential Isolation Z balanced Phase Zunbalanced Common Negative /180°/ Balance Single Frequency Inverted Mode Converter A passive balun converts Vbalanced bidirectionally between differential and single ended Digital Data Single Frequency Vunbalanced signals. Balun Transformer Balance Transforms between Isolation Amplitude and phase single ended and High insertion loss balance quantify how differential impedance between differential ports close to ideal a real balun according to the improves signal integrity. is. impedance ratio. Marki Microwave Inc. 5 Common Mode Rejection 3 2 Amplitude Balance 0 1 Good baluns provide ±2 dB 0 Marki baluns provide ±1 dB -10 -1 Amplitude Balance AmplitudeBalance (dB) -20 -2 -3 0 1 2 3 4 5 6 7 8 9 -30 Frequency (GHz) -40 CommonMode Rejection (dB) -50 210 0 1 2 3 4 5 6 7 8 9 200 Phase Balance Frequency (GHz) 190 Good baluns provide 15-20° Marki baluns provide 5-10° 180 Common Mode Rejection 170 Phase Balance Phase Balance (degree) 160 • Quantifies how much of a signal in 150 0 1 2 3 4 5 6 7 8 9 the ‘common mode’ of a Frequency (GHz) differential line will be rejected Marki Microwave Inc. 6 Mixed Mode S-Parameters 0 0 Insertion Loss (Output 1) Common Insertion Loss (Output 2) -3 -5 Output 1 Isolation Output 2 -6 -10 Isolation (dB) \ -9 -15 ReturnLoss (dB) -12 -20 InsertionLoss -15 -25 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 Frequency (GHz) Frequency (GHz) + Differential Single - Mode d 2 1 Ended Mode s + Common 3 + Mode c Mixed Mode S-Parameters S-Parameters Two ports, differential port has two Three ports with one mode each modes Better for isolation and output Better for differential return loss, impedance matching common mode rejection, and mode conversion loss Marki Microwave Inc. 7 Importance of Isolation VNA 0° 180° In 180° 0° Out Without Isolation Two Port VNA with Linear S-Parameters Lack of isolation causes poor Post-Processing Step Response differential return loss Impulse Response Four Port Dual Power Compression Source VNA Harmonic Generation Two Tone Intermodulation Marki Isolation Multitone Spurious Baluns Eye Diagrams Bit Error Ratio Linear Error Vector Magnitude Nonlinear Total Harmonic Distortion With Isolation Signal Integrity Spectral Regrowth Signal integrity improved in Differential to Single ended conversion Isolated Baluns Allow Complete Measurements Marki Microwave Inc. 8 Top Three Mistakes 1 Length Matching • Any differential trace mismatch produces a linear phase walk • Traces, cables, connectors, and other interconnects ΔΦ Phase 2 Trace Isolation Frequency • Neighboring channels can appear as aggressors • Far away channels will be more ‘common mode’ than nearby 3 Lack of Isolation • Low differential port isolation = high differential mode RL • Bad for differential to single ended conversions Marki Microwave Inc. 9 Poll Questions 10 Balun Types: Transformer Based Magnetic Core Magnetic Balanced Coupling Output Unbalanced Bifilar Balanced Balanced Capacitive and Input Magnetic Unbalanced Output Output Capacitive Coupling Input Coupling Unbalanced Input Flux Coupled Balun Transmission Line Transmission Line Transformer Balun Transformer Balun All coupling provided by Float the ground to Combines transmission line balun magnetic field create differential with magnetic material to eliminate output resonance and extend low end Provides ground/DC isolation Has problematic half Massive bandwidth ratio Massive bandwidth ratio wave resonance High frequency extends >10 GHz Limited to low frequencies Typically lossy (>2 dB excess insertion loss) New 10 MHz-12 GHz smaller form factor SMT Balun Marki Microwave Inc. 11 Balun Types: Coupler Based Tapered Balun Marchand Balun Tapered Balun Coupled Lines Based Baluns Coupled line structures with open/short ports New 2 GHz-20 GHz can be designed as baluns MMIC balun SMT MBAL-0220SM These baluns can be integrated and made in a planar structure Hundreds of circuit structure options Spiral Balun Low frequency is limited to 1-2 GHz Marki Microwave Inc. 12 Balun Types: Power Divider-Phase Shift Power Divider – Phase Shift Power Divider – Inverter Balun Planar Coupler Baluns Differential signaling can be realized by separating the signal first and then applying a phase shift Can provide extended high frequency, extended low frequency, and high isolation Marki Microwave Inc. 13 Balun Types: Magic Tee/Hybrid Coupler Power Divider – Inverter Balun Planar Coupler Baluns Rat Race Coupler Asymmetric Waveguide Magic Easy to Design and Tandem Coupler Tee Fabricate Difficult to Design and The original high Sub-octave bandwidth Fabricate isolation, low loss Can be very broadband Limited bandwidth Possible but not practical 180° Couplers Can be Used as Baluns, but also Have an Isolation/Sum Port. Marki Microwave Inc. 14 Marki Balun Catalog Surface Mount and Bare Die Baluns Analog to Digital Interfaces Test and Measurement Baluns Digital to Analog Interfaces For More Information Component Measurements Clock Driver Inputs Balun Primer Laboratory Experiments Balanced Circuits Tech Notes ADC/DAC Interfacing Antenna Feeds Videos High Speed Data [email protected] Marki Mission Statement Empower our customers to design faster, simplify production, eliminate complexity, and shatter performance barriers Marki Microwave Inc. © 15 Amplifier Biasing Made Easy Jacob Trevithick and Rob Maurer | April 16, 2020 A Brief Guide to Mixer Spurs Harley Berman and Christopher Marki | April 30, 2020 Register for our next webinars via links in upcoming email. 16.