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Summary
Summary
Designed an upconverter operating up to K-Band using a Gilbert Cell Active Mixer in GaAs pHEMT technology. Takes an input signal at L/S-band and converts up to K-band frequencies using a K-band tunable LO.
Performance is ideal (10-11 dB) from approximately 26GHz to 29GHz RF output, for 1GHz IF and tuned LO, and taking the low-side injection output. Output is amplified by at least 8 dB across K-band range, and exhibits high unity-gain bandwidth across IF and LO tunable ranges.
Conversion Gain
Conversion Gain
How much the lower input frequency is amplified at the higher frequency output. Maximize across operating frequency range.
On this polar plot, stability measurements using GPROBE in AWR were taken at each terminal of every transistor, swept from DC to 100 GHz. The circuit is unconditionally stable provided that no measurement encircles the (-1, 0) point on the plot. Worst case point is shown, demonstrating no unstable traces were observed from these measurements.
Non-Linear Stability
Non-Linear Stability
Unconditional stability from DC through transition frequency, measured at each transistor terminal.
On this polar plot, stability measurements using GPROBE in AWR were taken at each terminal of every transistor, swept from DC to 100 GHz. The circuit is unconditionally stable provided that no measurement encircles the (-1, 0) point on the plot. Worst case point is shown, demonstrating no unstable traces were observed from these measurements.
In order to fit the entire design, consisting of:
Gilbert cell mixer
two active baluns
one passive balun
eight bias tees
several bias voltage lines
ground-signal-ground ports
careful choices regarding spacing, bends, and overlays needed to be considered to accommodate all components while minimizing undesired coupling.
Die Footprint Size
Die Footprint Size
Fit within 3.4mm x 2.9mm package restriction.
Takeaways
Takeaways
Active baluns can provide additional gain to a differentially-driven circuit, but are challenging to stabilize
Smaller-sized transistors are more ideal for avoiding harmonics in Gilbert switching stage,
Larger-sized transistors are mode ideal for driving higher currents in Gilbert amplification stage.
Undesired coupling can be mitigated in certain cases with adjacent vias and carefully-placed shunt capacitors
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