UCLA

5G and Simultaneous Transmit and Receive (STAR) at radio frequency have led to an ever-increasing demand for physically smaller, wider bandwidth communication devices. In addition to civilian demand, electronic warfare also calls for robust RF systems that provide high fidelity communication and sensing in the presence of numerous interferences. Ultra-wideband Integrated Phased Array Systems are a major part of the solution to all this growing demand. Two components of particular interest to building an Ultra-wideband Integrated Phased Array System have been constructed with Gallium Nitride (GaN) transistors. The constructed circulator and power amplifier (PA) components both have excellent broadband, small-form factor, and scalability properties.

Using a switching network of transistors and transmission lines, it is possible to replicate the behavior of a traditional circulator. This constructed device, the Sequentially Switched Delay Line (SSDL), can overcome a circulator’s conventional limitations in insertion loss, form factor and bandwidth. Using passive bootstrapping, it is possible to increase the power handling and lower the insertion loss. Arranging SSDL devices in an array, it is possible to further raise the power handing and reduce distortions from the transistors’ higher order intermodulation terms. The SSDL in a 3,4,..,N-port setting, can provide a non-reciprocal device for simultaneous transmit and receive at the same radio frequency. The SSDL can also be used as a gyrator in a 2-port setting; it can provide a wideband conversion of a capacitor into an inductor.

A new differential broadband GaN PA design for direct integration with a Tightly Coupled Dipole Array (TCDA) will also be discussed. Using differential amplifiers, the overall PA design can be made balun-less. Using direct integration to a TCDA load, the overall PA design can leverage the TCDA’s common mode rejection of the second harmonic. Combining these design principles, the new integrated PA is also able to overcome conventional limitations in form factor and bandwidth.