Voltage Variable Attenuators
Voltage variable attenuators (VVA) find wide application in many microwave and millimeter-wave systems. At frequencies above 50 GHz, most voltage variable attenuators are either based on pin diodes or resistive vanes with motor driven mechanical actuators. Many pin diode voltage variable attenuators offer only partial waveguide band coverage (10 GHz at WR-10) with maximum power near 100 mW. Transistor chip attenuators are available with good performance to 100 GHz, but the maximum power rating is only 30 mW. The chip must be mounted to a circuit and integrated into the waveguide.
At Micro Harmonics we have developed a line of voltage variable attenuators based on the physics of Faraday rotation. Our VVA design uses a magnetic coil to produce a variable magnetic bias field in a ferrite rod. The voltage variable attenuators are similar in many respects to our Faraday rotation isolators. Using this approach, we have produced voltage variable attenuators in WR-15, WR‑12, and WR-10 with full waveguide band operation and relatively high power handling as compared to other technologies. These voltage variable attenuators are compact, lightweight, and are insensitive to damage from electrostatic discharge. The measured performance of our WR-10 millimeter wave attenuators is shown in the graph to the right. The legend denotes the current in the magnetic bias coil.
The measured port reflections are shown in the graph below. The VSWR is less than 1.5:1 at the highest attenuation levels.
The photograph to the left shows our WR-15 millimeter wave attenuator. The millimeter wave attenuator is compact with the main body measuring only 0.75 x 0.75 x 1 inch (19 x 19 x 25 mm). The small size makes the millimeter wave attenuators very easy to fit into millimeter-wave systems. A DC control voltage is applied through an SMP connector. The switching speed is estimated to be a few kilohertz due to the relatively large inductance of the magnetic coil.
Micro Harmonics designs and manufactures all products in the United States. In addition to millimeter wave attenuators, we make millimeter wave isolators and millimeter wave circulators as well. We do reliability testing (Belcore) and cryogenic cycling tests. Nylon thread lockers are used to ensure that our components stay assembled in the field. Every component is thoroughly RF tested, and the data is shared with the customer. Our components are fully warranted.
When you purchase a Micro Harmonics component, rest assured that you are receiving the highest quality and best performance available on the global commercial market. If you have any questions, don’t hesitate to contact us.