J. de Graaf

Generation of spectrally confined transmitted radar waveforms: experimental results

Managing the spectrum of radar emissions, particularly from shipboard radar platforms, is critical for minimizing interference to neighboring communication systems on ships, on land and other in-band radars. New radar waveform designs are needed to confine the radar transmitted spectrum to a region separate from other bands that are in use. An out-phasing technique (first developed by H. Chireix) is one approach that was implemented in hardware that provides a means of generating spectrally confined radar waveforms. A series of experiments were conducted in an effort to show the effects of power amplifiers (PA), in the Chireix out-phasing network, on spectrally confined waveforms under certain conditions. Several test results and conclusions are discussed in this paper.

Development of a digital array radar (DAR)

Twenty-first century littoral and open-sea missions present USA Navy (USN) shipboard-radar systems with the challenge of detecting small targets in severe clutter and against multiple sources of interference. In fiscal year 2000 (FY00), the Office of Naval Research (ONR) sponsored a program to develop an active array radar that includes a digital beamforming (DBF) architecture. The DBF radar system has the potential for improved time-energy management, improved signal-to-clutter (S/C) ratios, improved reliability and reduced life-cycle costs. This paper summarizes the latest developments of the program during FY00.

The measurement of broad band over power line emissions

This paper is a report on measurements taken of broadband over power line (BPL) signals at two US test sites in October 2004. The investigation sought to: (1) discriminate between BPL emissions and power line noise in the near field; (2) determine the maximum level of magnetic field intensity levels (H FIELD) at a given distance in the near field and (3) utilizing the CONCEPT II method of moments routine develop a numerical electromagnetic model of the power line emission (H/sub y/ and E/sub x/ ) characteristics.

Shared-spectrum multistatic radar: Preliminary experimental results

In this paper we present preliminary experimental results demonstrating the ability of the multistatic adaptive pulse compression (MAPC) algorithm to suppress the mutual-interference generated by shared-spectrum radar signals, thus enabling shared-spectrum radar. The MAPC algorithm, a waveform diversity technique wherein multiple known transmitted waveforms are adaptively pulse compressed using reiterative minimum mean-square error (RMMSE) estimation, has been shown to successfully suppress both range sidelobes and interference from multiple radars operating in the same spectrum. In this paper, we present initial experimental results from the adaptive pulse compression (APC) test bed that demonstrate the ability of MAPC to mitigate both the mutual interference from multiple radars and pulse compression range sidelobes when applied to measured data.

Adaptive Pulse Compression: Preliminary Experimental Measurements

Preliminary experimental results from the adaptive pulse compression (APC) test bed are presented. A recently proposed adaptive processing technique has been shown via simulation to improve upon current pulse compression techniques through a process known as reiterative minimum mean-square error estimation (RMMSE). The RMMSE technique forms the basis of the APC and the Multistatic APC (MAPC) algorithms. In this paper, we present experimental results demonstrating the feasibility of these approaches. Several polyphase waveforms have been implemented in an experimental test bed. Initial results show that small non-linearities in the waveform generation process have only a marginal impact on the estimation performance of the algorithms. A discussion of the APC test bed followed by experimental results demonstrating the performances of the APC and MAPC algorithms are presented. These initial experimental results indicate that the APC approach is able to successfully mitigate pulse-compression sidelobes on measured data, and that the MAPC algorithm can successfully mitigate both the mutual-interference from shared-spectrum radar signals and pulse compression sidelobes on measured data.

Calibration overview of the AMRFC test bed

The AMRFC (advanced multi-function radio frequency concept) phased array test bed is a joint effort to demonstrate the latest technologies to concurrently perform several Navys shipboard RF functions (e.g., communications, electronic warfare, and radar) including a calibration function through a common, shared software and RF architecture. The calibration function involves monitoring the drifts and misalignments of each subsystem as they vary over time and temperature. The main goal of calibration is to ensure that all interconnected components and subsystems perform as expected in terms of amplitude, and phase alignment. Key features of the calibration procedure are the method by which test and reference signals are generated, and how test data are collected and analyzed. The transfer functions of various subsystems in the test bed are measured via software control of these subsystems. A total of 22 calibration modes have been developed. In this paper, a single mode is described.

Advanced waveforms for software defined radar (SDR) to suppress interfering channels and provide isolation control

As the number of available channel bandwidths becomes increasingly scarce, more advanced radar waveforms are needed to provide better isolation control and interference suppression. A new technique was developed that will allow the end-user to define the channel bandwidths in a usable band and create waveforms in those bandwidths through software. This paper presents the highlights of this technique and some experimental results.

Transmit/receive isolation and ERP measurements of the AMRFC testbed

High transmit/receive (Tx/Rx) isolation of phased-array systems on board future US Navy ships is critical to preserving the performance of these systems. The advanced multifunction radio frequency (AMRFC) Testbed is a one-of-a-kind phased-array system that was evaluated to determine the level of Tx/Rx isolation for certain scan angles. The effective-radiated power (ERP) of the AMRFC Tx array was also evaluated to verify the emission characteristics under certain conditions. The preliminary results of evaluating the Tx/Rx isolation and ERP are discussed in this paper.

Digital local-oscillator generation using a delta-sigma technique

Local-oscillator (LO) signals in up/down converters for most radar systems are typically generated using synthesizers, bench sources, custom-built frequency sources or direct-digital synthesis (DDS). In a digital-array radar (DAR) concept, a single-bit delta-sigma (/spl Delta/-/spl Sigma/) technique is considered as a viable alternative to encode sine waves digitally for LO signal generation. This technique is applied to synthesize sinusoidal signals at a low frequency. These signals are then injected into a frequency multiplier system for generating LO signals. When independently coded /spl Delta/-/spl Sigma/ sine waves are created offline on a per element basis for a phased array system, the in-band noise shaped response improves as a result of digital beam forming (DBF). In this paper, a single-bit encoding technique for LO signal generation is discussed. Some simulation results are provided as well as a candidate microwave design for a frequency multiplier system.