Directional signal modulation by means of switched spaced antennas

The theory of modulation by hopping or by commutation among a number of spaced antennas is presented. The theory brings out the important considerations and criteria for determining the separation of discrete antennas in time and/or space that produces a desired modulation. In addition, antenna hopping and commutation are proposed for generating direction-dependent spread spectrum to enhance receiving system anti-interference processing gain and/or transmitted signal camouflage and LPI, as well as to provide an effective means for channel monitoring and analytical probing     

Perivitelline space granularity: a sign of human menopausal gonadotrophin overdose in intracytoplasmic sperm injection

The significance of the presence of coarse dark granules in the perivitelline space of oocytes has not been studied before. The study included 2288 intact oocytes [2063 in metaphase II (MII), 136 in metaphase I (MI), and 89 in germinal vesicle (GV)] retrieved in 206 intracytoplasmic sperm injection cycles stimulated by a long agonist protocol. The incidence of granules varied with oocyte maturity. It was detected in 34.3% and 4% of the MII and MI oocytes respectively, while none of the GV oocytes contained granules. The woman's age, hormonal values (oestradiol and progesterone), human chorionic gonadotrophin/oocyte retrieval interval, number of oocytes retrieved, and oocyte retrieval/injection interval were not related to the percentage of granular oocytes. Moreover, there was no correlation between the percentage of granular oocytes and the fertilization and cleavage rates, pregnancy outcome, as well as the implantation rate. Patients were divided into three groups according to the total human menopausal gonadotrophin (HMG) dose they received. There was a statistically significant difference between the three groups in the percentage of granular oocytes [17.4 +/- 5.2% versus 26.7 +/- 3.2% versus 45.4 +/- 4.2% in the low-dose (< 30 ampoules), intermediate dose (31-45 ampoules), and high-dose (> 45 ampoules) groups respectively]. We conclude that granularity in the perivitelline space is probably a physiological phenomenon related to the maturational events in oocytes and enhanced by exposure to high dosages of HMG.     

Cascaded bandpass vth-law devices

The effect of the n-cascaded bandpass vth-law devices on the sum of a strong signal and a weak signal is analysed. It is shown that if any of the nonlinear devices is a hard-limiter, the n-cascaded nonlinearities have the same effect as that of a single hard-limiter. If two such cascaded n vth-law devices (differing in at least one vth-value) or two complex bandpass nonlinearities are connected in parallel, we obtain the generalised form of a `power-division? multiplex system which utilises a feed-forward across a limiter technique.     

Novel Techniques for Counteracting Multipath Interference Effects in Receiving Systems

Discrete maltipath propagation is generally considered to impose severe limitations on the performance of receiving systems, and hence, on the information transmission capacity of a communication link. Much work has been directed to the problems of relieving multipath effects, generally concentrating on correction of the performance realized with the resultant of the multiple-path outputs. In this paper, the emphasis is on separating the outputs of a small number of discrete paths not only for freeing the output of at least one usable path, but also possibly for combining the various path outputs in constructive ways to take advantage of the additional signal energy that each path provides. Novel techniques for accomplishing this are described, based on converting directional and propagation-delay differences into very distinctive frequency differences by synthetic Doppler methods. These techniques are of course applicable to facilitate the separation of various time and frequency overlapping signals arriving from different directions.     

Theory of frequency modulation by synthetic antenna motion

The author presents the theory governing the method of simulating of synthesizing antenna motion over a specified aperture onboard a supporting platform by commutating among a number of discrete antennas arranged along a prescribed path of motion. The theory brings out the considerations and criteria for selecting the number and spacing of antennas to be commutated; the effects, and hence criteria, for specifying the pulse characteristics of the gating (or blending) time function that describes how each antenna is tapped (or switched on and turned off) by the commutator each time it is activated; the nature and performance characteristics of the blending corrective filter, or postcommutator sample interpolator, that will extract the desired Doppler-modulated signal if the spacing between successively activated antennas is such that no time-invariant blending function will extricate the desired sampling spectral zone for any but a very restricted type of signal; and the guidelines for resolving complications that may arise are in a number of special situations