Abstract
Fully digital arrays offer huge advantages in terms of flexibility and performance; however, they may suffer from dynamic range issues when used in the presence of in-band interferers. Higher dynamic range components can be used, but are more costly and power hungry, making the implementation of such technology impractical. This paper presents a way to mitigate those interferers by creating a spatial notch at the RF front-end with an antenna-agnostic circuit placed at the feeding network of the antenna array. This circuit creates a steerable null in the embedded element pattern that mitigates interferers at a specified incoming angle. A full mathematical model and closed form expressions of the behavior of the circuit are obtained and compared to simulated and measured results, where up to a 20 dB null in the embedded element pattern of an 1$\times$ 8 array is achieved with less than 1.5 dB of insertion loss. Finally, a real case scenario is set up with a desired signal and an interferer, which is initially saturating the receiver. The receiver successfully demodulates the signal after the null is placed in the direction of the interferer.
Highlights
The generation of radar and wireless communication systems should have advanced flexibility, allowing multi-purpose functions and spatial multiplexing while simultaneously reducing cost [1], [2]
Both approaches use complementary metal-oxide-semiconductor (CMOS) technology that compromises the power handling limitation when strong interferers are present. These CMOS RF front-end architectures suffer from a trade-off between noise figure and power handling. This trade-off is caused because high gain is needed at the RF front-end to reduce the noise figure, but due to low supply voltages used in current CMOS processes, even a 0 dBm interferer will can cause the amplification stage to clip and will result in a dynamic range limitation [18]
This paper introduces a Spatial Interference Mitigation Circuit (SIMC) that is able to mitigate interferers at the RF front-end before they enter the receiver by creating a steerable null in the antenna’s embedded element pattern
Summary
The generation of radar and wireless communication systems should have advanced flexibility, allowing multi-purpose functions and spatial multiplexing while simultaneously reducing cost [1], [2]. A total of 51 dB mitigation with moderate impact in the noise figure of 3.4 − 5.8 dB and the ability to create multiple notches is demonstrated in [16] This approach implies designing a fully integrated receiver resulting in lack of flexibility because the RF system must use only that specific receiver architecture in order to have a front-end spatial filter. This trade-off is caused because high gain is needed at the RF front-end to reduce the noise figure, but due to low supply voltages used in current CMOS processes, even a 0 dBm interferer will can cause the amplification stage to clip and will result in a dynamic range limitation [18] Another way to handle spatial interference is by using the Butler matrix, but they suffer from scalability problems for large arrays due to size. The signal is demodulated once the null is placed in the direction of the interferer
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