1. ECE 6361:Mixer Design Review 2.4 GHz Single Balanced Mixer Jan Brosi Vasileios Iliopoulos

2. Project Objectives I IF Frequency 140MHz IF Bandwidth 5 MHz RF Frequency 2400-2485 MHz LO Frequency 2260-2345 MHz LO Power 8 dBm (max) Conversion Loss >-9.5 dB RF Power -10 dBm (max) LO-RF Rejection <-20dB LO-IF Rejection<-30 dB IF Input power0 dBm (max)

3. Spurious Signals at RF port Relative to desired RF with 8 dBm LO power 1000-2120 MHz <-30dBc 2325-2400 MHz <-40 dBc 2400-2485 MHz <-50 dBc 2485-2900 MHz <-40 dBc Project Objectives II Board:4-layer PPE (1.7x2.6 inches) Schottky diodes: dual series connected

4. Physical Construction I 27mm Reduced-size rat-race balun with coupled lines on different layers Radial stubs for matching at RF/LO frequency Lumped elements for matching at IF and for DC-return

5. Physical Construction II Board parameters: εr=2.85 ±0.5 tanδ=0.002-0.003 core thickness=1mm resin thickness=50μm copper thickness=12μm Diodes: Zetex ZC2812ECT IS=9.5nA, RS=16.3Ohm N=1.27, Cj0=1.1pF Lumped Elements Toko 2021 series chip inductors Panasonic chip capacitors

6. Simulation with Agilent ADS using a combination of Multilayer & Microstrip models Diode Model: ADS P-N diode model with parameters from manufacturer’s data sheet Inclusion of parasitic elements (bends, steps, T- junctions, vias, pads, parasitics of lumped elements). Balun design with S-parameter simulation and gradient method optimization for best performance Mixer harmonic balance simulation with 8 orders and gradient method optimization Model Description & Simulation

7. Simulation Results Simulated circuit meets all specs

8. Measurement of conversion loss in down-conversion using the frequency offset function of HP89441 Network analyzer The LO port is fed by E4432 Signal Generator with 8.5dBm input power (assuming 0.5 dB cable loss) Use of a low-pass filter at the input port of the Network analyzer to ensure better phase-locking The filter response was calibrated out  Accuracy of the measurement: Signal generator: ± 0.5dB Network analyzer: ± 0.2dB Total accuracy: ± 0.7dB Conversion Loss Measurement

9. LO FrequencyMax. Conv. Loss over IF BW Uncertainty Range Specs met 2.26 GHz8.4 dB7.7-9.1 dBYes 2.3025 GHz8.8 dB8.1-9.5 dBYes 2.345 GHz9.5 dB8.8-10.2 dBNo Conversion Loss Measurement Results Conversion loss increases with increasing LO-frequency

10. Measurement of spurious signals and LO-RF isolation for up-conversion using HP8994E Spectrum Analyzer. Measurement of LO-IF isolation for down-conversion Sweep over the LO frequency range Accuracy of the spurious signals measurement Relative accuracy of spectrum analyzer: ±0.5dB Accuracy of the LO-RF isolation measurement Absolute accuracy of spectrum analyzer: ±1dB Signal generator: ±0.5dB Total accuracy: ± 1.5dB Spurious & Isolation Measurement

11. Spurious & Isolation Measurement Graph LORF LO+2IF LO+3IF LO+4IF LO-IF LO-2IF LO-3IF

12. Signal Worst value in frequency range Uncertainty rangeSpec Spurious LO-3·IF -29.7dBc-29.2 to -30.3dBc-30dBc Spurious LO-2·IF -20.3dBc-19.8 to -20.8dBc-30dBc Spurious LO +2·IF -27dBc-26.5 to -27.5dBc-40dBc Spurious LO + 3·IF -30.9dBc-30.4 to -31.4dBc-40dBc Spurious LO+4·IF -41.7dBc-41.2 to -42.3dBc-40dBc Spurious Measurement Results

13. Signal Worst value in frequency range Uncertainty rangeSpec Isolation LO-RF -12dB-10.5 to –13.5dBc-20dB Isolation LO-IF -21.5dB-20 to -23dBc-30dB Isolation Measurement Results

14. Circuit assembled as designed has bad performance and does not meet any of the specs Slight change of inductor & capacitor values and interchange of their position increased mixer performance The mixer seems to be shifted to lower frequencies, it works much better at f LO =1.9 GHz Thus it was tried to reduce the size of the mixer Coupled lines were shortened by use of new vias Line edges were smoothened with copper material to reduce length Resulting circuit had best performance and was used for measurements Changes made to the Circuit

15. Comparison to Simulations The measurements don’t match with the simulations Trying to fit ADS-model to measurements by change of dielectric constant, distance between layers, coupled line offset, length and width of lines, stub length and width, vias and pads, losses and diode model. This should account for production tolerances and previously not considered effects Changes didn’t have a significant effect on the simulated mixer performance Indication that ADS multilayer-model is not accuarate

16. A single-balanced mixer using a reduced-size rat- race balun with mulilayer coupled-lines was designed, simulated, fabricated and measured Great differences between model and measurements of the produced mixer occurred Performance could be increased by change of lumped elements and reducing the size of lines Specifications for Conversion loss are almost met, for Isolation and some spurious signals not Re-simulation was not successful Summary & Conclusions I

17. Summary & Conclusions II The ADS multilayer-model does not seem to work well in our case, another software or model should be tried Board parameters like layer thickness and dielectric constant should be reevaluated The mixer works much better at lower frequencies, the balun seems to be downshifted For the next production cycle, the line lengths should be decreased to account for that