Power amplifier nonlinearity introduces intermodulation distortion when transmitting dual-tone signals from an antenna array. To reduce distortion levels and increase output power for dual-tone systems we propose to densely interleave two antenna arrays without increasing the antenna aperture. Each array is excited with a different tone, resulting in a single-tone input for the power amplifiers, thereby reducing intermodulation distortion. In order to compare the performance of the densely interleaved array with a regular, planar array, when excited by two-tone signals, a procedure for evaluating the S-parameters matrix of an interleaved dipole array is presented. Simulations with a realistic RF power amplifier model show 13 to 31 dB intermodulation reduction for the same output power and total antenna aperture.

The modern spectral, and thereby linearity, requirements force 5G phased-array transmitter systems to operate at reduced power efficiency, as they can no longer use voluminous filtering. To reduce the linearity requirements of the transmitter, we consider the case of an array consisting of closely spaced radiating elements operating at different frequencies.The coupled tones from one element to another create reverse intermodulation distortion (RIMD). We explain how RIMD is created within a power amplifier (PA), and derive an estimate for the power of the RIMD components. We provide a set of measurements for an X-Band GaAs PA and draw a direct comparison between RIMD and IMD. We show that RIMD has a third-order behaviour up to very high reverse power levels, opening up the perspective for higher output power operation as well as simpler and lower-power predistortion in multi-tone array systems such as 5G and radar.

We present a simple and useful figure of merit (FoM) with which to evaluate the performance of simultaneous-multibeam (SMB) transmit (TX) antenna arrays. The FoM builds upon the power-aperture product and effective isotropic radiated power for single-beam arrays and extends it to SMB arrays. The FoM is the product of radiated power, antenna aperture efficiency and the amplifiers power added efficiency. We compute the FoM for three different two-beam TX systems to highlight their differences. This will enable systematic comparison and proper system design for modern and future multi-beam radar and communications.

We present a simple and useful figure of merit (FoM) with which to evaluate the performance of simultaneous-multibeam (SMB) transmit (TX) antenna arrays. The FoM builds upon the power-aperture product and effective isotropic radiated power for single-beam arrays and extends it to SMB arrays. The FoM is the product of radiated power, antenna aperture efficiency and the amplifiers power added efficiency. We compute the FoM for three different two-beam TX systems to highlight their differences. This will enable systematic comparison and proper system design for modern and future multi-beam radar and communications.

We propose a fast and simple method to accurately determine the compressing stage in a two-stage amplifier system based on reverse intermodulation and hot S-parameter measurements. The method uses no specialized hardware and needs little reconfiguration, simplifying the measurements. We demonstrate its validity over a broad range of amplifiers designed in various semiconductor technologies. This method is a very useful tool in understanding or debugging amplifier designs.