EP0656697A2
Expired / Lapsed
EP
⏱️ 0.0 years remaining
Method and apparatus for creating fast fading at a receiver using orthogonally polarized antennas and transmitter time diversity
Assignee: AT&T Inc
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Filing: 1994-11-23
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Granted: —
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Expires: 2014-11-23
Abstract
Abstract A system for inducing rapid fading in wireless communication systems (10), such as digital radio and television transmission is described. Orthogonal polarization from antennas (30,32) combined with time varying offsets introduced by mixer (24) and oscillator (26) are combined to ensure rapid fading and result in improved signal reception at receiver antenna (35).
Inventors
- 👤 Michael James Gans
- 👤 Vijitha Weerackody
- 👤 Jack Harriman Winters
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-31 00:11
CPC Classifications
H; H04; H04B; H04B7/00; H04B7/02; H04B7/10
Claims Analysis
Total Claims: 24
Claim 1
Independent Claim
146 words
An apparatus for transmitting data comprising: a carrier signal source, a data signal source, a modulator having a first input, a second input, and an output, the first input connected to the carrier signal source and the second input connected to the data signal source, said modulator having an output, a first channel having an input and an output, said input connected to the modulator output, a second channel having an input and an output, said input connected to the modulator output, the second channel further comprising an offset device for applying a time varying offset to the data signal, a first transmitting antenna coupled to the output of the first channel; and a second transmitting antenna coupled to the output of the second channel, said first and second transmitting antennas being arranged to transmit signals which are substantially orthogonally polarized with respect to one another.
Claim 2
Dependent Claim
12 words
The apparatus of claim 1 wherein the modulator uses differentially encoded modulation.
Claim 3
Dependent Claim
11 words
The apparatus of claim 1 wherein the modulator uses coherent modulation.
Claim 4
Dependent Claim
37 words
The apparatus of claim 1 wherein the time varying offset is a time varying phase offset and the time varying phase offset induces a fixed frequency offset which is between 1 to 2% of the data rate.
Claim 5
Independent Claim
88 words
An apparatus for transmitting data comprising: a first channel having an input and an output; a second channel having an input and an output, the second channel further comprising an offset device for applying a time varying offset to the data signal; a first transmitting antenna coupled to the output of the first channel; and a second transmitting antenna coupled to the output of the second channel, said first and second transmitting antennas being arranged to transmit signals which are substantially orthogonally polarized with respect to one another.
Claim 6
Dependent Claim
43 words
The apparatus of claim 5 wherein the first transmitting antenna is a linear antenna which is arranged to transmit a signal with vertical polarization and the second transmitting antenna is a linear antenna which is arranged to transmit a signal with horizontal polarization.
Claim 7
Dependent Claim
47 words
The apparatus of claim 5 wherein the first transmitting antenna is a circularly polarized antenna which is arranged to transmit a signal left hand circularly polarized and the second transmitting antenna is a circularly polarized antenna which is arranged to transmit a signal right hand circularly polarized,
Claim 8
Dependent Claim
18 words
The apparatus of claim 7 wherein the first transmitting antenna and the second transmitting antenna are helical antennas.
Claim 9
Dependent Claim
31 words
The apparatus of claim 5 further comprising a data signal source for producing a data signal wherein the inputs of the first and second channels are connected to the signal source.
Claim 10
Dependent Claim
26 words
The apparatus of claim 1 or 9 wherein the data signal source comprises: a digital message source for producing message data symbols, and a channel encoder.
Claim 11
Dependent Claim
14 words
The apparatus of claim 10 and further comprising an interleaver for rearranging data symbols.
Claim 12
Dependent Claim
17 words
The apparatus of claim 1 or 5 wherein the offset device applies a time varying phase offset.
Claim 13
Dependent Claim
17 words
The apparatus of claim 1 or 5 wherein the offset device applies a time varying amplitude offset.
Claim 14
Dependent Claim
17 words
The apparatus of claim 1 or 5 wherein the frequency of the carrier signal is about 100HHz.
Claim 15
Independent Claim
116 words
A method for transmitting data comprising the steps of: generating a carrier signal, generating a data signal, modulating the carrier signal based upon the data signal to form a modulated carrier signal, applying the modulated carrier signal to the input of a first channel and to the input of a second channel, applying a time varying offset to the modulated carrier signal in the first channel, applying the output of the first channel to the input of a first transmitting antenna and the output of the second channel to the input of a second transmitting antenna, wherein the first and second transmitting antennas produce output signals which are substantially orthogonally polarized with respect to each other.
Claim 16
Dependent Claim
30 words
The method of claim 15 wherein the step of generating the data signal comprises the steps of generating a digital message comprising message data symbols and encoding the digital message.
Claim 17
Dependent Claim
13 words
The method of claim 16 further comprising the step of interleaving data symbols.
Claim 18
Dependent Claim
19 words
The method of claim 15 wherein the step or modulating comprises the step of differentially encoding the digital data.
Claim 19
Dependent Claim
24 words
The method of claim 15 wherein the time varying offset applied is varied at a rate between 1 to 2% of the data rate.
Claim 20
Independent Claim
176 words
An apparatus for receiving data comprising a first receiving antenna having an input and an output, a second receiving antenna having an input and an output, said first and second receiving antennas arranged to receive signals at their inputs which are substantially orthogonally polarized with respect to one another, a first channel having an input and an output, said input connected to the output of the first receiving antenna, a second channel having an input and an output, said input connected to the output of the second receiving antenna, said second channel comprising an offset device for applying a time varying offset to a signal at the second channel's input to create a signal with a time varying offset at the second channel's output, said time varying offset being substantially independent of the signal at the second channel's input, a signal combiner having an output, and first and second inputs connected to the outputs of the first and second channels respectively, and signal processing means having an input connected to the output of the signal combiner.
Claim 21
Dependent Claim
39 words
The apparatus of claim 20 wherein the first receiving antenna is configured to receive a linearly polarized signal in the vertical direction and the second receiving antenna is configured to receive a linearly polarized signal in the horizontal direction.
Claim 22
Dependent Claim
35 words
The apparatus of claim 20 wherein the first receiving antenna is configured to receive a left hand circularly polarized signal and the second receiving antenna is configured to receive a right hand circularly polarized signal.
Claim 23
Dependent Claim
17 words
The apparatus of claim 20 wherein the signal processing means further comprises a decoder and a deinterleaver.
Claim 24
Independent Claim
163 words
An apparatus for receiving data comprising a first receiving antenna having an input and an output, a second receiving antenna having an input and an output, said first and second receiving antennas arranged to receive signals at their inputs which are substantially orthogonally polarized with respect to one another, a first channel having an input and an output, said input connected to the output of the first receiving antenna, a second channel having an input and an output, said input connected to the output of the second receiving antenna, said second channel comprising an offset device for applying a periodic time varying offset to a signal at the second channel's input to create a signal with a periodic time varying offset at the second channel's output, a signal combiner having an output, and first and second inputs connected to the outputs of the first and second channels respectively, and signal processing means having an input connected to the output of the signal combiner.
References Cited (Backward Citations)
US4160952A
Cited
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