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Millimeter-wave (mmWave) systems use directional beams to support high-rate data communications. Small misalignment between the transmit and receive beams (e.g., due to the mobility) can result in significant drop of the received signal quality especially in line-of-sight communication channels. In this paper, we propose and evaluate high-resolution angle tracking strategies for wideband mmWave systems with mobility. We custom design pairs of auxiliary beams as the tracking beams, and use them to capture the angle variations, towards which the steering directions of the data beams are adjusted.Different from conventional beam tracking designs, the proposed framework neither depends on the angle variation model nor requires an on-grid assumption. For practical implementation of the proposed methods, we examine the impact of the array calibration errors on the auxiliary beam pair design.Numerical results reveal that by employing the proposed methods, good angle tracking performance can be achieved under various antenna array configurations, channel models, and mobility conditions.

In this paper, a novel two-dimensional super-resolution angle-of-departure (AoD) and angle-ofarrival (AoA) estimation technique is proposed for wideband millimeter-wave multiple-input multipleoutput systems with cross-polarized antenna elements. The key ingredient of the proposed method is to form custom designed beam pairs, and devise an invertible function of the AoD/AoA to be estimated from the corresponding beam pairs. Further, a new multi-layer reference signal structure is developed for the proposed method to facilitate angle estimation for wideband channels with cross-polarized antenna elements. To facilitate feedback in closed-loop frequency division duplexing systems, a novel differential feedback strategy is proposed aiming at feedback reduction for the two-dimensional angle estimation.Numerical results demonstrate that by using the proposed method, good azimuth/elevation AoD and AoA estimation performance can be achieved under different levels of signal-to-noise ratio, channel conditions, and antenna array configurations.

The concept of roll-decoupled course correction fuze with canards can provide a cost-effective solution to improve the delivery accuracy for conventional unguided ammunitions. Due to the dual-spin configuration and canards for such a projectile, the basic projectile stability theory should be extended to well perceive its behavior of motion. The seven degree-of-freedom dynamic equations of motion for the dual-spin projectile are established in the fixed-plane frame and the differential equation for the complex angle of attack is derived by the use of the projectile linear theory without the assumption of a flat trajectory. A revised stability criterion is established according to the Hurwitz stability criterion and analytic solutions of the stability boundaries for trim angles are developed. The new stability criterion can account for the possible flight instability of projectiles subjected to side forces applied at the nose, and can be reduced to the same form as the conventional spin-stabilized projectile case. Moreover, detailed trajectory simulations of two sample projectiles indicate that the new stability criterion gives satisfactory agreement with numerical results.

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