No abstract

No abstract

No abstract

Ongoing work is exploring the optimization of physical radar emissions based on the continuous phase modulation (CPM) implementation of polyphase codes. Here a modification to the code search strategy known as Marginal Fisher's Information (MFI) is presented that enables this greedy approach to further improve upon the performance of the resulting CPM-implemented continuous waveform in terms of range sidelobes. The optimization process is also expanded to include the effects of the transmitter (from both modeled and physical hardware perspectives) to facilitate the optimization of physical emissions that are specifically tuned to the transmitter. This approach is particularly useful for high-power transmitters in which the actual physical emission is a spectrally modified and non-linearly distorted version of the intended radar waveform.

In this paper we shall demonstrate how a polyphasecoded radar waveform can be implemented using a continuous phase modulation (CPM) framework so as to achieve spectral containment while maintaining a constant envelope to maximize energy-on-target. Current modulation techniques such as derivative phase shift keying (DPSK) and minimum shift keying (MSK), which are applicable to binary-coded waveforms, are well-known implementation schemes for spectral containment. The CPM implementation is applicable to polyphase codes and can also achieve better spectral containment, though a byproduct is increased range sidelobes that result due to the deviation from the idealized code (implicitly defined for squared-shaped chips). To ameliorate the increased range sidelobes, a version of Least-Squares mismatched filtering is employed that accommodates the continuous nature of the CPM structure. Also, continuous rise/fall-time transitions of the pulse are addressed as part of the holistic implementation of the CPM-based waveform. It is observed that for the CPM implementation the rise/fall-time becomes the limiting factor on spectral containment and a rather simple scheme based on Chireaux out-phasing is suggested as a means to "slow down" the pulse rise/fall.

Small phase perturbations applied to a steppedfrequency or linear-frequency-modulated radar waveform have been proposed as a means to generate frequency nulls in the spectrum of the transmitted waveform. By nulling selected frequencies (or thinning) in the spectrum of transmitted pulses, the interference between the transmitted and received signals is reduced, which facilitates the spectral cohabitation of multiple RF users. Preliminary experimental results of two methods of spectral nulling are presented with consideration to in-band and out-of-band interference. Range processing is examined to determine the effects of the phase perturbation on radar operations. I.

No abstract

Haemangiosarcoma (HSA) is a neoplasm of the endothelial cells. Intramuscular HSA is an uncommon presentation of this endothelial cell neoplasm. This report describes an unusual case of an intramuscular HSA arising in the hindlimb of a dog with associated abscessation. Diagnosis of underlying HSA was complicated by associated infection and initial cytological evaluation showed only septic suppurative inflammation. However, due to the heterogeneously contrast enhancing appearance of the area on CT, underlying neoplasia was suspected. Definitive diagnosis of HSA could only be made following excision and histopathology of the affected muscle in addition to immunohistochemistical stains. This dog received multimodal treatment including surgery, radiation and chemotherapy, and despite developing metastatic lesions, was alive 12 months after presentation, at the time of manuscript writing. Deep abscessation can occur concurrently with neoplasia, and neoplasia should remain on the differential diagnosis list for deep abscesses of unknown aetiology.