Large-scale phased arrays need to combine weighted signals from multiple sub-arrays either in analog or in digital domain. Sub-arrays are preferably implemented modularly with integrated circuits placed next to the associated antennas. In order to enable flexible and scalable combining networks of several mmWave sub-arrays, this paper presents a wideband receiver module that provides the cartesian combining of beamforming weights for one sub-array at IF. Furthermore, it allows interference cancellation between subarrays or combining multiple sub-arrays. It also provides filtering before ADCs to support current and foreseeable 5G channel bandwidths up to 800MHz. The receiver is operating at 2-4GHz IF frequency range and has more than 400MHz baseband bandwidth, a noise-figure of 5.5dB,-6dBm 1dB compression point and +3dBm in-band IIP3. In addition, overthe-air measurements are performed, showing 26dB of interference cancellation between the sub-arrays. The prototype is implemented using 45nm CMOS PDSOI.

Practical radio frequency beamforming can suffer from high sidelobe levels which cause inter-beam interference (IBI) in multibeam transceivers. IBI can be reduced by shaping the amplitude and phase excitation over the individual antenna elements. However, such methods do not exploit the available power efficiently in practical arrays, where each antenna is driven with a dedicated power amplifier. In this paper, we show a simplified approach for hybrid beam synthesis in subarraybased beamforming architecture and propose a two-stage beamforming method for cancelling the IBI. The proposed technique cancels the interference between the subarrays while it maximizes the effective isotropic radiated powers in the desired directions. Simulation show typically over 40 dB IBI rejection for randomly spread beams and more than 4 dB improvement for radiated power compared to amplitude tapering.

The performance of multi-user millimeterwave (mmW) systems is limited by relatively high sidelobe levels (SLLs) of antenna arrays. Per-antenna amplitude control can be used to adjust the amplitudes to reduce the SLL, but the reduction is often achieved at the cost of reduced transmitted power. Large two-dimensional (2D) antenna panels used in mmW phased arrays, however, allow the 2D antenna configuration to be reconfigured to reduce the SLL. In this paper, we present a simplified approach for sidelobe reduction by stacking multiple uniform linear arrays of different size to reduce the sidelobes across the horizontal plane. The approach is based on the relation between the number of antenna elements and the directions of null and sidelobe maxima. The sidelobe reduction is demonstrated by both simulations and measurements. The measurements are carried out in an anechoic chamber at 28 GHz center frequency using a 100 MHz wide modulated 5GNR waveform.

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Multiantenna systems can increase the spatial reuse of the wireless spectrum by nulling the interfering directions. However, the efficiency of the spatial interference suppression is highly sensitive to errors in the progressive phase applied to the antenna elements. We examine the impact of one particular source of error resulting from the quantization of the analog beamforming weights. In particular, we focus on vector-modulator based RF beamforming system. To improve the quantization error, we propose a sliding reference approach for using a floating phase reference minimizing the quantization error of the RF beamformer. Monte-Carlo simulations are performed to analyze the performance of the zeroforcing with quantized coefficients. With small arrays, the simulation results showed almost 10 dB of improvement in the average null depth compared to the conventional round-off method.