Showing papers by "Randy L. Haupt published in 2019"
TL;DR: In this article, the authors demonstrated the two-way pattern sidelobe reduction using only uniform transmit and receive apertures, showing that the expected peak SLL is a little less than −27 dB, which can be reduced without amplitude tapering if the receive array is made smaller by turning off edge elements.
Abstract: A two-way array factor is the product of the transmit array factor and the receive array factor of a radar. Lowering the sidelobe level (SLL) of the two-way pattern traditionally requires amplitude tapering the transmit and receive apertures. This communication demonstrates the two-way pattern sidelobe reduction using only uniform transmit and receive apertures. If both array factors are uniform, then the expected peak two-way SLL is a little less than −27 dB. This level can be reduced without amplitude tapering if the receive array is made smaller by turning off edge elements. This communication demonstrates this idea for uniform linear and planar arrays. An additional 6.7 dB reduction is possible for the two-way maximum SLL.
18 citations
01 Jul 2019
TL;DR: In this article, the authors take a look at the beam squint and dispersion problems associated with high data rate phased array antennas and propose the use of time delay in addition to phase shifters.
Abstract: Antenna arrays were originally designed for a single frequency. The term phased array implies a narrow band approach to beam steering and adaptive nulling. This paper takes a look at the beam squint and dispersion problems associated with high data rate phased array antennas. This paper is a tribute to R.C. Hansen who spent a career investigating antenna effects on wide band signals. He advocated the use of time delay in addition to phase shifters in a high data rate antenna array.
8 citations
07 Jul 2019
TL;DR: This work presents a novel beamforming methodology based on evolutionary search techniques that is capable of adaptive interference cancellation in high-interference environments and presents experimental results on the performance of the proposed technique using in-house developed software defined radio digital beamformer.
Abstract: Digital beamforming adaptive nulling algorithms analyze the digital signals received by the beamformer to cancel interference while receiving a desired signal. In high-interference environments, however, classical approaches to digital beamforming often cannot distinguish between the intended signal and interferences, disrupting the intended operation. Here we present a novel beamforming methodology based on evolutionary search techniques that is capable of adaptive interference cancellation in high-interference environments. We present experimental results on the performance of our proposed technique using an in-house developed software defined radio digital beamformer.
7 citations
01 Jan 2019
TL;DR: A cost-effective platform for DBF using a software-defined radio array is reported and experimental results on interference cancellation using the DBF platform indicate that all adaptive methods provide significant improvements over unit weights.
Abstract: Digital beamforming (DBF) is the holy grail of antenna array technology. However, very few DBF arrays have been demonstrated due to the high cost of implementation. Here we report on a cost-effective platform for DBF using a software-defined radio array and present experimental results on interference cancellation using the DBF platform. We transmitted digital data modulated with 4-QAM from a single-element transmitter to the 4-element DBF array while a single-element interferer disrupted the transmission. Digital beamforming interference cancellation was then implemented with three different algorithms, namely, least mean squares, sample matrix inversion, and recursive least squares. The bit error rates in each case are compared for several interference power levels. The results indicate that all adaptive methods provide significant improvements over unit weights, with sample matrix inversion outperforming recursive least squares and recursive least squares outperforming least mean squares.
5 citations
22 Apr 2019
TL;DR: The potential benefits of jointly synthesizing the low sidelobe tapers of the transmit and receive patterns to improve the two-way pattern sidelobes are explained.
Abstract: Radar designs frequently specify a two-way array pattern sidelobe level. The two-way pattern is the product of the transmit and receive array patterns. Usually, the transmit and receive array patterns are independently synthesized. This paper explains the potential benefits of jointly synthesizing the low sidelobe tapers of the transmit and receive patterns to improve the two-way pattern sidelobes. In particular, results for a circular ring array with a Taylor taper on receive and a uniform/Taylor taper on transmit are presented. Results presented show up to a 3 dB lower sidelobe level than is obtained using the traditional approach.
3 citations
TL;DR: This paper applies Hans Steyskal's concepts to different adaptive array scenarios to provide insight into distortions in the adapted pattern.
Abstract: Research into antenna array pattern synthesis started with lows sidelobe amplitude tapers. Later, adaptive nulling and null synthesis became very important. Contributions by Dr. Hans Steyskal gave tremendous insight into array pattern nulling. This paper applies his concepts to different adaptive array scenarios to provide insight into distortions in the adapted pattern.
2 citations
TL;DR: In this article, a simple formula is derived for the bandwidth of a phased array antenna, where the upper frequency is determined by the grating lobe formation and the lower bound based on beam squint/pulse dispersion.
Abstract: A phased array is inherently narrowband, because phase is a narrowband concept. The components that comprise the array determine the operational bandwidth while, the number of elements, the element spacing, and the maximum scan angle contribute to the array instantaneous bandwidth. This paper considers these four factors in arriving at a definition for the bandwidth of a phased array antenna. A simple formula is derived for phased array bandwidth where the upper frequency is determined by the grating lobe formation and the lower bound based on beam squint/pulse dispersion.
2 citations
01 Jan 2019
TL;DR: A frequency tunable microstrip patch operating over an 870 MHz bandwidth at the 5 GHz wireless local area network (WLAN) band is presented.
Abstract: We present a new design for a frequency configurable microstrip patch antenna. The tuning mechanism consists of placing shorting posts placed in pre-drilled holes between the patch and ground plane at set locations on the patch. The hole locations are arranged so that the insertion of shorting pins in certain holes result in a predetermined resonant frequency. A frequency tunable microstrip patch operating over an 870 MHz bandwidth at the 5 GHz wireless local area network (WLAN) band is presented.
1 citations
22 Apr 2019
TL;DR: Ourline of First Half I.Adaptive Nulling without Digital Beamforming II.
Abstract: Ourline of First Half I.Introduction to Adaptive Antennas II.Array Analysis and Synthesis III.Array Beams IV.Direction Finding V.Adaptive Nulling without Digital Beamforming
1 citations
01 Jan 2019
TL;DR: In this paper, a new coplanar electromagnetic band-gap structure is proposed to suppress the simultaneous switching noise, based on the zigzag line and square patch bridge, the inductance between the neighboring units can be enhanced.
Abstract: ─ Simultaneous switching noise (SSN) generated between the power supply and the ground plane of a high-speed digital circuit is considered to be one of the most important factors affecting the signal integrity of a circuit system. In order to suppress the simultaneous switching noise, a new coplanar electromagnetic band-gap structure is proposed in this paper. Based on the zigzag line and square patch bridge, the inductance between the neighboring units can be enhanced. The results showed that the bandwidth of the band-gap is 0.1 ~ 12.6GHz when the depth of the new electromagnetic band-gap (EBG) structure is -30 db. Compared to the same parameter of the L-bridge structure, the relative bandwidth is about 48.7% and the cut-off frequency of the stop-band lower limit is reduced by 600MHz. The simultaneous switching noise on the power supply plane can be suppressed in all directions, and the signal integrity is less affected when the signal is transmitted by the differential line. Index Terms ─ Coplanar electromagnetic band-gap, electromagnetic band-gap structure, high-speed digital circuits, simultaneous switching noise.
TL;DR: In this paper, the authors derived an expression that predicts the axial ratio degradation due to random errors in the circularly polarized elements of an array, in the case of small errors in an array of crossed dipoles.
Abstract: Characterizing the random errors at the elements of a phased array antenna leads to equations that estimate the associated performance degradation. The increase in sidelobe level and decrease in gain due to random errors is well established. This paper derives an expression that predicts the axial ratio degradation due to random errors in the circularly polarized elements of an array. In the case of small errors in an array of crossed dipoles, we found a simple expression for the axial ratio of the array under random errors at broadside.