EP0507440A1
Expired / Lapsed
EP
⏱️ 0.0 years remaining
Antenna
Assignee: Individual
•
Filing: 1992-02-24
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Granted: —
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Expires: 2012-02-24
Abstract
Abstract A satellite television receiver antenna for use on seaborne vessels comprise a Cassegrain antenna comprising a parabolic main reflector 1A, and a hyperbolic sub-reflector 1B mounted at an angle slightly opposite from the center axis of the parabolic reflector 1A, the sub-reflector being driven by a motor 30 to rotate so as to cause the antenna reception pattern to perform a conical scan around the main axis of the parabolic reflector 1A. The rotational speed is an even multiple of the frequency of any amplitude modulation of the received signal, or of any electrical interference, and the received signal is measured at points rotationally spaced apart 180 degrees, so that the effects of modulation and/or electrical interference are cancelled. The measured signal strength at four positions spaced rotationally by 90° is used to derive power signals to drive pulse width modulation control azimith and elevation motors 46A, 46B.
Inventors
- 👤 Gerald Alexander Bayne
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-01 08:43
CPC Classifications
H; H01; H01Q; H01Q1/00; H01Q1/12; H01Q1/125; H01Q1/1257; H01Q3/00; H01Q3/02; H01Q3/08; H01Q3/10; H01Q3/12; H01Q3/16; H01Q3/20
Claims Analysis
Total Claims: 28
Claim 1
Independent Claim
64 words
A satellite television receiver antenna system for use on a vehicle, comprising a receiver antenna having a main reception direction, means for scanning the main reception direction of the antenna, means for measuring the signal strength received from the antenna during the scan, and means for varying the alignment of the antenna to maintain orientation with the satellite on the basis of the measurement.
Claim 2
Dependent Claim
49 words
A tracking receiver antenna having a Cassegrain configuration comprising a main reflector and a relatively small sub-reflector, the reflectors being arranged to direct a received signal to a signal detector, in which the sub-reflector is mounted and rotated so as to cyclically vary the reception direction of the antenna.
Claim 3
Dependent Claim
46 words
A scanning Cassegrain antenna comprising a main reflector and a sub-reflector, the sub-reflector being mounted so that the focii of the two reflectors substantially co-incide, but their principal axes are angularly mis-aligned, the sub-reflector being rotatable relative to the main reflector to scan the antenna pattern.
Claim 4
Dependent Claim
41 words
In a modulated signal reception system, a scanning receiver antenna in which the scanning period of the antenna is related to the modulation frequency of the signal whereby the antenna alignment may be performed without dependence upon interference from said modulation.
Claim 5
Dependent Claim
39 words
A scanning receiver antenna in which the antenna scanning frequency is related to the frequency of a mains power supply influencing the antenna, whereby the antenna positional control is arranged not to depend upon the effects of said influence.
Claim 6
Dependent Claim
20 words
An antenna according to any one of claims 2 to 5 suitable for use as a satellite tracking receiver antenna.
Claim 7
Dependent Claim
13 words
An antenna according to any preceding claim arranged to perform a conical scan.
Claim 8
Dependent Claim
66 words
An antenna according to any preceding claim comprising scan rate control means for maintaining the rate at which the antenna is scanned, said control means comprising means responsive to the rotational position of a rotated element of said antenna to produce a rotational position signal, and means for rotating a component of said antenna in dependence upon said signal to maintain said scan rate substantially constant.
Claim 9
Dependent Claim
27 words
An antenna according to claim 8 in which the position responsive means comprises a radiation detector responsive to radiation modulated by a positional feature on said component.
Claim 10
Dependent Claim
69 words
An antenna according to claim 8 or claim 9 in which said rotating means comprises a rotary motor and means for supplying power to said motor, the power supply means being arranged to supply power in dependence upon the rotational position signal when the scan rate is within a predetermined range, and to supply power at a different rate when the scan rate falls below or exceeds said range.
Claim 11
Dependent Claim
57 words
An antenna according to claim 10, in which the power supply means comprises means for supplying power as a pulse sequence, the width of pulses of said sequence being varied when the scan rate is within said range so as to maintain the scan rate therein, and being constant when the scan rate is without said range.
Claim 12
Dependent Claim
98 words
A rotary speed control system comprising a rotary position signal generator generating a periodically varying signal having an average level related to the rotary speed, and a reference signal generator generating a corresponding signal, further comprising comparator means arranged to generate an output corresponding to the difference between said signals, whereby when the rotary speed approximates a desired speed said comparator means generates a pulsed output, the width of which is modulated to stabilize said rotary speed, and when said rotary speed diverges substantially from said desired speed said comparator output remains constant to adjust said rotary speed.
Claim 13
Dependent Claim
32 words
A speed control system according to claim 12 in which the reference signal generator and the rotary position signal generator each comprise a tachometer device connected to respective periodically varying signal sources.
Claim 14
Dependent Claim
20 words
An antenna including a component connected to be rotated by apparatus according to claim 13 to scan the antenna beam.
Claim 15
Dependent Claim
45 words
An antenna according to any one of claims 1 to 11 or 13 further comprising means arranged to sample the signal received by said antenna at spaced points in said antenna scan and to generate an antenna alignment signal in dependence upon a difference therebetween.
Claim 16
Dependent Claim
28 words
An antenna according to claim 14 when appended to claim 8 or 9 in which said sampling means are controlled in response to said rotary position detecting means.
Claim 17
Dependent Claim
29 words
An antenna according to claim 15 comprising interpolation means responsive to said rotary position signal to produce a plurality of sampling position signals, corresponding to said spaced points, therefrom.
Claim 18
Dependent Claim
55 words
An antenna according to any one of claims 14 to 16, in which said spaced points comprise at least one pair of points mutually in anti-phase relationship in said scan, and said antenna position signal generating means comprise means response to the difference between the signal sample at the points comprising the or each pair.
Claim 19
Dependent Claim
45 words
An antenna according to claim 17, in which said sampling means are arranged to sample at points comprising a plurality of said pairs, and the position signal generating means are responsive to the sum of the signal levels at sampling points adjacent within said scan.
Claim 20
Dependent Claim
52 words
An antenna according to claim 17 when appended to claim 7 in which the sampling means are arranged to sample the signal at points comprising two orthogonally disposed pairs, and the antenna position signal comprises two output signals representing orthogonal alignment axes, each signal being derived in dependence upon one said pair.
Claim 21
Dependent Claim
31 words
An antenna according to any one of claims 1 to 11 or 13 to 19 further comprising means for varying the alignment of the antenna to maintain orientation with a satellite.
Claim 22
Dependent Claim
28 words
An antenna according to claim 1 or claim 20 in which the varying means comprise a pair of motors arranged to vary the antenna alignment in orthogonal axes.
Claim 23
Dependent Claim
31 words
An antenna according to any one of claims 1, 20 or 21 in which the means for varying the alignment are inversely responsive to the rate of variation of the alignment.
Claim 24
Dependent Claim
77 words
An antenna according to claim 22 when appended to claim 21 in which each motor comprises a rotary motor and a reduction gear, and the varying means comprises velocity sensing means arranged to generate a signal corresponding to the rotational speed of each motor, means for applying an antenna alignment signal to vary the alignment of the antenna, and means for supplying power to the motors in response both to the alignment signal and the velocity signal.
Claim 25
Dependent Claim
29 words
An antenna according to claim 1 or claim 20, in which the varying means comprise a motor connected to the antenna via a linkage permitting slippage under predetermined circumstances.
Claim 26
Dependent Claim
34 words
An antenna according to claim 1 or claim 20 in which the varying means comprise a rotary drive connected to the antenna and there are provided means for reducing backlash within the varying means.
Claim 27
Dependent Claim
28 words
An antenna according to claim 26 in which the backlash reducing means comprise a brake acting on a shaft through which the varying means acts on the antenna.
Claim 28
Dependent Claim
84 words
An antenna according to claim 7 comprising a drive circuit for rotating an element of the antenna, the scan drive circuit comprising a motor, a pulse controlled power supply and means for supplying power control pulses to said supply, said means comprising a rotary position sensor, and means for deriving, from the output thereof, at least one pulse within each rotation having a width which increases in dependence upon the rotary period, so as to increase the power supplied when the rotary speed decreases.
References Cited (Backward Citations)
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EP0002982A1
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US4675688A
Cited
US4786912A
Cited
EP0403684A2
Cited
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