It is quite common for transceivers to operate with the RF receiver and transmitter working on different time slots. Typical applications are radars and transceivers in the field of communications. Generally, the receiver is turned off when the transmitter broadcasts and vice versa. This is done in order to prevent the transmitter from blinding the receiver or causing the RF low noise amplification (LNA) stage to saturate. When keeping a receiver active, some leakage of RF energy is inevitable, and therefore shielding is applied to mitigate spurious signals. However, there are many applications wherein the receiver cannot be turned off. To address these applications, we investigate the design and performance of a fully-analog self-jamming canceller able to operate in UHF (Ultra High Frequency) RFID devices. While the traditional cost to design and build this type of topology can be quite high, our proposal is based on a low-cost physical approach. In addition to using common SMT (Surface Mount Technology) devices, we leveraged a new piece of modular technology offered by X-Microwave which allows designers to easily produce RF solutions with a broad portfolio of modular system drop-in blocks. A prototype was realized and the measured results are in close agreement with theoretical simulations. Significant damping of the leaked signal in the receiving channel was realized.
Rossi, M.; Liberati, R.M.; Frasca, M.; Richardson, J. Experimental Implementation of a Low-Cost, Fully-Analog Self-Jamming Canceller for UHF RFID Devices. Electronics 2020, 9, 786
F. Rodriguez-Morales, C. Carabajal, A. Paden and C. Leuschen, Center for Remote Sensing of Ice Sheets, University of Kansas; J. McDaniel, Advanced Radar Research Center, University of Oklahoma; and A. Wolf and S. Garrison, Kansas City National Security Campus
A set of compact ultra-wideband (UWB) radar transmit/receive modules has been developed using rapid prototyping. The modules are based on tailored microwave filters, off-the-shelf building blocks from a commercial supplier and custom DC biasing circuits. As an intermediate step toward full system miniaturization, the integration of microwave components using this technique enables evaluation of different configurations to improve radar performance with a reduced form factor.
Remote sensing with radar systems on airborne platforms is key for wide-area data collection to estimate the impact of ice and snow masses on rising sea levels. The NASA P-3B and DC-8, as well as other platforms, successfully flew with multiple versions of the Snow Radar developed at the Center for Remote Sensing of Ice Sheets. Compared to these manned missions, the Global Hawk Uninhabited Aerial Vehicle can support flights with long endurance, complex flight paths and flexible altitude operation up to 70,000 ft. This thesis documents the process of adapting the 2-18 GHz Snow Radar to meet the requirements for operation on manned and unmanned platforms from 700 ft to 70,000 ft. The primary focus of this work is the development of an improved microwave chirp generator implemented with frequency multipliers. The x16 frequency multiplier is composed of a series of x2 frequency multiplication stages, overcoming some of the limitations encountered in previous designs. At each stage, undesired harmonics are kept out of the passband and filtered. The miniaturized design presented here reduces reflections in the chain, overall size, and weight as compared to the large and heavy connectorized chain currently used in the Snow Radar. Each stage is implemented by a drop-in type modular design operating at microwave and millimeter wavelengths; and realized with commercial surface-mount integrated circuits, wire-bondable chips, and custom filters. DC circuits for power regulation and sequencing are developed as well. Another focus of this thesis is the development of the band-pass filters used in the frequency multiplier using different distributed element filter technologies. Multiple edge-coupled band pass filters are fabricated on alumina substrate based on the design and optimization in computer-aided design tools. Interdigital cavity filter models developed in-house are validated through full-wave iv electromagnetic simulation and measurements. Overall, the measured results of the modular frequency multiplier and filters match with the expected responses from original design and cosimulation outputs. The design files, test setups, and simulation models are generalized to use with new designs in the future.