US5422913A — High frequency multichannel diversity differentia…

Claim 1

Independent Claim 225 words

A high frequency multichannel communications system having at least a transmitter and a receiver: said transmitter comprising: a) input means for receiving digital signal data for transmission of transmitted data bits: b) the input means, connected to a plurality of separate diversity frequency channels distributed over a broad spectral region of a high frequency band, each channel including a differential phase shift key (DPSK) modulator, for modulating a channel frequency by successive bits of the digital signal data at a low data rate to produce a DPSK channel signal; and c) means for combining the DPSK channel signals from each of the plurality of separate diversity frequency channels for transmission; and wherein said receiver comprising: a) receiver means for receiving and demodulating the transmitted signals to form baseband signals; b) said baseband signals from the receiver means being connected to a plurality of narrowband receiver frequency channels, each receiver frequency channel including a DPSK detector responsive to a respective one of the transmitted DPSK channel frequency signals; c) means for identifying any of said receiver frequency channels corrupted by noise; and d) semi-coherent processing means, responsive to each transmitted data bit, for vectorially adding DPSK detector output signals, excluding said channels corrupted by noise and for producing a resultant vector signal phase for determining polarity of each transmitted data bit as a data output signal.

Claim 2

Dependent Claim 225 words

A high frequency multichannel communications system having at least a transmitter and a receiver: said transmitter comprising: a) input means for receiving digital signal data for transmission of transmitted data bits: b) the input means, connected to a plurality of separate diversity frequency channels distributed over a broad spectral region of a high frequency band, each channel including a differential phase shift key (DPSK) modulator, for modulating a channel frequency by successive bits of the digital signal data at a low data rate to produce a DPSK channel signal; and c) means for combining the DPSK channel signals from each of the plurality of separate diversity frequency channels for transmission; and wherein said receiver comprising: a) receiver means for receiving and demodulating the transmitted signals to form baseband signals; b) said baseband signals from the receiver means being connected to a plurality of narrowband receiver frequency channels, each receiver frequency channel including a DPSK detector responsive to a respective one of the transmitted DPSK channel frequency signals; c) means for identifying any of said receiver frequency channels corrupted by noise; and d) semi-coherent processing means, responsive to each transmitted data bit, for vectorially adding DPSK detector output signals, excluding said channels corrupted by noise and for producing a resultant vector signal phase for determining polarity of each transmitted data bit as a data output signal.

Claim 3

Dependent Claim 20 words

A high frequency multichannel communications system as claimed in claim 1 wherein the receiver is synchronised to the received signal.

Claim 4

Dependent Claim 35 words

A high frequency multichannel communications system as claimed in claim 1 wherein the data rate is selected such that dispersion effects during transmission from the transmitter to the receiver does not lead to intersymbol interference.

Claim 5

Dependent Claim 28 words

A high frequency multichannel communications system as claimed in claim 3 wherein said digital signal data is transmitted at a baud rate between 20 and 100 per sec.

Claim 6

Dependent Claim 18 words

A high frequency multichannel communications system as claimed in claim 4 wherein the baud rate is 50 bps.

Claim 7

Dependent Claim 24 words

A high frequency multichannel communications system as claimed in claim 1 wherein the transmitted signal has a number of phase states greater than two.

Claim 8

Dependent Claim 240 words

A high frequency multichannel communications system having at least a transmitter and a receiver: said transmitter comprising: a) input means for receiving digital signal data for transmission of transmitted data bits; b) the input means, connected to a plurality of separate diversity frequency channels distributed over a broad spectral region of a high frequency band, each channel including a differential phase shift key (DPSK) modulator, for modulating a channel frequency by successive bits of the digital signal data at a low data rate to produce a DPSK channel signal; and c) means for combining the DPSK channel signals from each of the plurality of separate diversity frequency channels for transmission; and wherein said receiver comprising: a) receiver means for receiving and demodulating the transmitted signals to form baseband signals; b) said baseband signals from the receiver means being connected to a plurality of narrowband receiver frequency channels, each receiver frequency channel including a DPSK detector responsive to a respective one of the transmitted DPSK channel frequency signals; c) means for identifying any of said receiver frequency channels corrupted by noise; and d) semi-coherent processing means, responsive to each transmitted data bit, for vectorially adding DPSK detector output signals, excluding said channels corrupted by noise and for producing a combined vector signal phase for determining polarity of each transmitted data bit as a data output signal, wherein there is included a channel exciser for excising channels identified as noise corrupted channels.

Claim 9

Dependent Claim 240 words

A high frequency multichannel communications system having at least a transmitter and a receiver: said transmitter comprising: a) input means for receiving digital signal data for transmission of transmitted data bits; b) the input means, connected to a plurality of separate diversity frequency channels distributed over a broad spectral region of a high frequency band, each channel including a differential phase shift key (DPSK) modulator, for modulating a channel frequency by successive bits of the digital signal data at a low data rate to produce a DPSK channel signal; and c) means for combining the DPSK channel signals from each of the plurality of separate diversity frequency channels for transmission; and wherein said receiver comprising: a) receiver means for receiving and demodulating the transmitted signals to form baseband signals; b) said baseband signals from the receiver means being connected to a plurality of narrowband receiver frequency channels, each receiver frequency channel including a DPSK detector responsive to a respective one of the transmitted DPSK channel frequency signals; c) means for identifying any of said receiver frequency channels corrupted by noise; and d) semi-coherent processing means, responsive to each transmitted data bit, for vectorially adding DPSK detector output signals, excluding said channels corrupted by noise and for producing a combined vector signal phase for determining polarity of each transmitted data bit as a data output signal, wherein there is included a channel exciser for excising channels identified as noise corrupted channels.

Claim 10

Dependent Claim 273 words

A high frequency multichannel communications system having at least a transmitter and a receiver: said transmitter comprising: a) input means for receiving digital signal data for transmission of transmitted data bits: b) the input means, connected to a plurality of separate diversity frequency channels distributed over a broad spectral region of a high frequency band, each channel including a differential phase shift key (DPSK) modulator, for modulating a channel frequency by successive bits of the digital signal data at a low data rate to produce a DPSK channel signal; and c) means for combining the DPSK channel signals from each of the plurality of separate diversity frequency channels for transmission; and wherein said receiver comprising: a) receiver means for receiving and demodulating the transmitted signals to form baseband signals; b) said baseband signals from the receiver means being connected to a plurality of narrowband receiver frequency channels, each receiver frequency channel including a DPSK detector responsive to a respective one of the transmitted DPSK channel frequency signals; c) means for identifying any of said receiver frequency channels corrupted by noise; and d) semi-coherent processing means, responsive to each transmitted data bit, for vectorially adding DPSK detector output signals, excluding said channels corrupted by noise and for producing a combined vector signal phase for determining polarity of each transmitted data bit as a data output signal wherein said DPSK modulator is an M phase DPSK modulator which produces an M phase DPSK channel signal where M is an integer and the means for identifying noise-corrupted channels includes a phase window detector having M phase windows of width <360/M deg centered on M phase states.

Claim 11

Dependent Claim 273 words

A high frequency multichannel communications system having at least a transmitter and a receiver: said transmitter comprising: a) input means for receiving digital signal data for transmission of transmitted data bits: b) the input means, connected to a plurality of separate diversity frequency channels distributed over a broad spectral region of a high frequency band, each channel including a differential phase shift key (DPSK) modulator, for modulating a channel frequency by successive bits of the digital signal data at a low data rate to produce a DPSK channel signal; and c) means for combining the DPSK channel signals from each of the plurality of separate diversity frequency channels for transmission; and wherein said receiver comprising: a) receiver means for receiving and demodulating the transmitted signals to form baseband signals; b) said baseband signals from the receiver means being connected to a plurality of narrowband receiver frequency channels, each receiver frequency channel including a DPSK detector responsive to a respective one of the transmitted DPSK channel frequency signals; c) means for identifying any of said receiver frequency channels corrupted by noise; and d) semi-coherent processing means, responsive to each transmitted data bit, for vectorially adding DPSK detector output signals, excluding said channels corrupted by noise and for producing a combined vector signal phase for determining polarity of each transmitted data bit as a data output signal wherein said DPSK modulator is an M phase DPSK modulator which produces an M phase DPSK channel signal where M is an integer and the means for identifying noise-corrupted channels includes a phase window detector having M phase windows of width <360/M deg centered on M phase states.

Claim 12

Dependent Claim 91 words

A high frequency multichannel communications system as claimed in claim 8 wherein a HIT is when a detected phase falls within a phase window and a MISS is when a detected phase falls outside a phase window, including a counter connected to each channel for providing, over a predetermined time, a first signal indicative of a running average of HITS for each channel and a second signal representing the proportion of HITs to MISSes said first and second signals connected to a discriminator for determining whether the channel is noise corrupted.

Claim 13

Dependent Claim 47 words

A high frequency multichannel communications system as claimed in claim 9 wherein each phase window is 360/2M deg and said discriminator provides an output indicating a channel to be uncorrupted by noise when said second signal indicates that the proportion of HITs to Misses is above 1.

Claim 14

Dependent Claim 52 words

A high frequency multichannel communications system as claimed in claim 10 wherein the proportion of HITs to MISSes in each channel and the number of phase windows taken to measure the proportion are selected with reference to a channel signal-to-noise (S/N) ratio and a predetermined probability of correct identification of channel corruption.

Claim 15

Dependent Claim 33 words

A high frequency multichannel communications system as claimed in claim 11, wherein the resultant vector signal phase for each phase window is connected to a PSK decoder for providing said data output signal.

Claim 16

Dependent Claim 277 words

A high frequency multichannel communications system having at least a transmitter and a receipt; said transmitter comprising: a) input means for receiving digital signal data for transmission Of transmitted data bits: b) the input means, connected to a plurality of Separate diversity frequency channels distributed over a broad spectral region of a high frequency band, each channel including a differential phase shift key (DPSK) modulator, for modulating a channel frequency by successive bits Of the digital signal data at a low data rate to produce a DPSK channel signal; and c) means for combining the DPSK channel signals from each of the plurality of separate diversity frequency channels for transmission; and wherein said receiver comprising: a) receiver means for receiving and demodulating the transmitted signals to form baseband signals; b) said baseband signals from the receiver means being connected to a plurality of narrowband receiver frequency channels, each receiver frequency channel including a DPSK detector responsive to a respective one of the transmitted DPSK channel frequency signals: c) means for identifying any of said receiver frequency channels corrupted by noise; and d) semi-coherent processing means, responsive to each transmitted data bit, for vectorially adding DPSK detector output signals, excluding said channels corrupted by noise and for producing a combined vector signal phase for determining polarity of each transmitted data bit as a data output signal wherein the plurality of narrowband channels in the receiver are arranged into contiguous broader bandwidth groups where the channels of each group are connected to a respective coherent adder for coherently adding uncorrupted channel signals and the adder outputs are connected to the semi-coherent processing means for vectorially adding the adder outputs.

Claim 17

Dependent Claim 277 words

A high frequency multichannel communications system having at least a transmitter and a receipt; said transmitter comprising: a) input means for receiving digital signal data for transmission Of transmitted data bits: b) the input means, connected to a plurality of Separate diversity frequency channels distributed over a broad spectral region of a high frequency band, each channel including a differential phase shift key (DPSK) modulator, for modulating a channel frequency by successive bits Of the digital signal data at a low data rate to produce a DPSK channel signal; and c) means for combining the DPSK channel signals from each of the plurality of separate diversity frequency channels for transmission; and wherein said receiver comprising: a) receiver means for receiving and demodulating the transmitted signals to form baseband signals; b) said baseband signals from the receiver means being connected to a plurality of narrowband receiver frequency channels, each receiver frequency channel including a DPSK detector responsive to a respective one of the transmitted DPSK channel frequency signals: c) means for identifying any of said receiver frequency channels corrupted by noise; and d) semi-coherent processing means, responsive to each transmitted data bit, for vectorially adding DPSK detector output signals, excluding said channels corrupted by noise and for producing a combined vector signal phase for determining polarity of each transmitted data bit as a data output signal wherein the plurality of narrowband channels in the receiver are arranged into contiguous broader bandwidth groups where the channels of each group are connected to a respective coherent adder for coherently adding uncorrupted channel signals and the adder outputs are connected to the semi-coherent processing means for vectorially adding the adder outputs.

Claim 18

Dependent Claim 21 words

A high frequency multichannel communications system as claimed in claim 13 where each group has a bandwidth less than 2 kHz.

Claim 19

Dependent Claim 119 words

A high frequency multichannel communications system as claimed in claim 14, further including first and second channel excisers, wherein in said means for identifying channels corrupted by noise, the DPSK channel signal detected in each receiver channel is connected to first and second channel excisers and to an error detector; the output from said error detector being connected to said first and second channel excisers for excising noise-corrupted channels; the first exciser being connected through a semi-coherent channel vector summer and through a PSK detector to a data output and the second exciser being connected via a second semi-coherent vector summer for providing an estimated combined vector signal phase input signal to a second input of said error detector.

Claim 20

Dependent Claim 37 words

A high frequency multichannel communications system as claimed in claim 15 wherein of an excision decorrelator is connected to an input to the second exciser for preventing the number of excised channels from exceeding a pre-determined value.

Claim 21

Dependent Claim 244 words

A high frequency multichannel communications system having at least a transmitter and a receiver: said transmitter comprising: a) input means for receiving digital signal data for transmission of transmitted data bits: b) the input means, connected to a plurality of separate diversity frequency channels distributed over a broad spectral region of a high frequency band, each channel including a differential phase shift key (DPSK) modulator, for modulating a channel frequency by successive bits of the digital signal data at a low data rate to produce a DPSK channel signal; and c) means for combining the DPSK channel signals from each of the plurality of separate diversity frequency channels for transmission; and wherein said receiver comprising: a) receiver means for receiving and demodulating the transmitted signals to form baseband signals; b) said baseband signals from the receiver means being connected to a plurality of narrowband receiver frequency channels, each receiver frequency channel including a DPSK detector responsive to a respective one of the transmitted DPSK channel frequency signals: c) means for identifying and of said receiver frequency channels corrupted by noise; and d) semi-coherent processing means, responsive to each transmitted data bit, for vectorially adding DPSK detector output signals, excluding said channels corrupted by noise and for producing a combined vector signal phase for determining polarity of each transmitted data bit as a data output signal wherein said vectorially added DPSK detector output signals are connected to each means for identifying channels corrupted by noise.

Claim 22

Dependent Claim 244 words

A high frequency multichannel communications system having at least a transmitter and a receiver: said transmitter comprising: a) input means for receiving digital signal data for transmission of transmitted data bits: b) the input means, connected to a plurality of separate diversity frequency channels distributed over a broad spectral region of a high frequency band, each channel including a differential phase shift key (DPSK) modulator, for modulating a channel frequency by successive bits of the digital signal data at a low data rate to produce a DPSK channel signal; and c) means for combining the DPSK channel signals from each of the plurality of separate diversity frequency channels for transmission; and wherein said receiver comprising: a) receiver means for receiving and demodulating the transmitted signals to form baseband signals; b) said baseband signals from the receiver means being connected to a plurality of narrowband receiver frequency channels, each receiver frequency channel including a DPSK detector responsive to a respective one of the transmitted DPSK channel frequency signals: c) means for identifying and of said receiver frequency channels corrupted by noise; and d) semi-coherent processing means, responsive to each transmitted data bit, for vectorially adding DPSK detector output signals, excluding said channels corrupted by noise and for producing a combined vector signal phase for determining polarity of each transmitted data bit as a data output signal wherein said vectorially added DPSK detector output signals are connected to each means for identifying channels corrupted by noise.

Claim 23

Dependent Claim 77 words

A high frequency multichannel communications system as claimed in claim 17, wherein the DPSK detector output signals in each channel are connected to one input of an error detector with an estimated combined vector signal phase being connected to a second input to the error detector, an output signal from the error detector is connected to an error counter, said error counter providing a noise corrupted channel output whenever a detected error rate exceeds a predetermined threshold.

Claim 24

Dependent Claim 36 words

A high frequency multichannel communications system as claimed in claim 18 wherein said error detector only provides an output if the detected phase signal is outside a pre-determined range centered on the combined vector phase signal.

Claim 25

Dependent Claim 298 words

A high frequency multichannel communications system having at least a transmitter and a receiver: said transmitter comprising: a) input means for receiving digital signal data for transmission of transmitted data bits: b) the input means, connected to a plurality Of separate diversity frequency channels distributed over a broad spectral region of a high frequency band, each channel including a differential phase shift key (DPSK) modulator, for modulating a channel frequency by successive bits of the digital signal data at a low data rate to produce a DPSK channel signal; and c) means for combining the DPSK channel signals from each of the plurality of separate diversity frequency channels for transmission: and wherein said receiver comprising.: a) receiver means for receiving and demodulating the transmitted signals to form baseband signals; b) said baseband signals from the receiver means being connected to a plurality of narrowband receiver frequency channels, each receiver frequency channel including a DPSK detector responsive to a respective one of the transmitted DPSK channel frequency signals; c) means for identifying any of said receiver frequency channels corrupted by noise; and d) semi-coherent processing means, responsive to each transmitted dam bit, for vectorially adding DPSK detector output signals, excluding said channels corrupted by noise and for producing a combined vector signal phase for determining polarity of each transmitted data bit as a data output signal wherein the transmitter includes a demultiplexer [(1101)]responsive to the digital signal data for providing at respective outputs demultiplexed portions of said signal data, said plurality of separate frequency channels are divided into groups of different frequency channels, each group connected to a respective demultiplexed portion of said signal data and each channel transmitting at a low data rate between 20-100 bps and the receiver includes a multiplexer to reproduce the transmitted data signal.

Claim 26

Dependent Claim 298 words

A high frequency multichannel communications system having at least a transmitter and a receiver: said transmitter comprising: a) input means for receiving digital signal data for transmission of transmitted data bits: b) the input means, connected to a plurality Of separate diversity frequency channels distributed over a broad spectral region of a high frequency band, each channel including a differential phase shift key (DPSK) modulator, for modulating a channel frequency by successive bits of the digital signal data at a low data rate to produce a DPSK channel signal; and c) means for combining the DPSK channel signals from each of the plurality of separate diversity frequency channels for transmission: and wherein said receiver comprising.: a) receiver means for receiving and demodulating the transmitted signals to form baseband signals; b) said baseband signals from the receiver means being connected to a plurality of narrowband receiver frequency channels, each receiver frequency channel including a DPSK detector responsive to a respective one of the transmitted DPSK channel frequency signals; c) means for identifying any of said receiver frequency channels corrupted by noise; and d) semi-coherent processing means, responsive to each transmitted dam bit, for vectorially adding DPSK detector output signals, excluding said channels corrupted by noise and for producing a combined vector signal phase for determining polarity of each transmitted data bit as a data output signal wherein the transmitter includes a demultiplexer [(1101)]responsive to the digital signal data for providing at respective outputs demultiplexed portions of said signal data, said plurality of separate frequency channels are divided into groups of different frequency channels, each group connected to a respective demultiplexed portion of said signal data and each channel transmitting at a low data rate between 20-100 bps and the receiver includes a multiplexer to reproduce the transmitted data signal.

Claim 27

Dependent Claim 28 words

A high frequency multichannel communications system as claimed in claim 20 wherein the channels of any one multiplexed group are interleaved with the channel of every other group.

Claim 28

Dependent Claim 276 words

A high frequency multichannel communications system having at least a transmitter and a receiver: said transmitter comprising: a) input means for receiving digital signal data for transmission of transmitted data bits: b) the input means, connected to a plurality of separate diversity frequency channels distributed over a broad spectral region of a high frequency band, each channel including a differential phase shift key (DPSK) modulator for modulating a channel frequency by successive bits of the digital signal data at a low data rate to produce a DPSK channel signal; and c) means for combining the DPSK channel signals from each of the plurality of separate diversity frequency channels for transmission; and wherein said receiver comprising; a) receiver means for receiving and demodulating the transmitted signals to form baseband signals; b) said baseband signals from the receiver means being connected to a plurality of narrowband receiver frequency channels, each receiver frequency channel including a DPSK detector responsive to a respective one of the transmitted DPSK channel frequency signals; c) means for identifying any of said receiver frequency channels corrupted by noise; and d) semi-coherent processing means, responsive to each transmitted data bit, for vectorially adding DPSK detector output signals, excluding said channels corrupted by noise and for producing a combined vector signal phase for determining polarity of each transmitted data bit as a data output signal wherein the receiver means is connected to the receiver frequency channels via an analogue to digital converter connected to a Fast Fourier Transform (FFT) processor which has a number of frequency channels equal to the number of receiver frequency channels and the signal phase is detected in each receiver frequency channel.

Claim 29

Dependent Claim 276 words

A high frequency multichannel communications system having at least a transmitter and a receiver: said transmitter comprising: a) input means for receiving digital signal data for transmission of transmitted data bits: b) the input means, connected to a plurality of separate diversity frequency channels distributed over a broad spectral region of a high frequency band, each channel including a differential phase shift key (DPSK) modulator for modulating a channel frequency by successive bits of the digital signal data at a low data rate to produce a DPSK channel signal; and c) means for combining the DPSK channel signals from each of the plurality of separate diversity frequency channels for transmission; and wherein said receiver comprising; a) receiver means for receiving and demodulating the transmitted signals to form baseband signals; b) said baseband signals from the receiver means being connected to a plurality of narrowband receiver frequency channels, each receiver frequency channel including a DPSK detector responsive to a respective one of the transmitted DPSK channel frequency signals; c) means for identifying any of said receiver frequency channels corrupted by noise; and d) semi-coherent processing means, responsive to each transmitted data bit, for vectorially adding DPSK detector output signals, excluding said channels corrupted by noise and for producing a combined vector signal phase for determining polarity of each transmitted data bit as a data output signal wherein the receiver means is connected to the receiver frequency channels via an analogue to digital converter connected to a Fast Fourier Transform (FFT) processor which has a number of frequency channels equal to the number of receiver frequency channels and the signal phase is detected in each receiver frequency channel.

Claim 30

Dependent Claim 273 words

A high frequency multichannel communications system having at least a transmitter and a receiver; said transmitter comprising: a) input means for receiving digital signal data for transmission of transmitted data bits: b) the input means, connected to a plurality of Separate diversity frequency channels distributed over a broad spectral region of a high frequency band, each channel including a differential phase shift key (DPSK) modulator, for modulating a channel frequency by successive bits of the digital signal data at a low data rate to produce a DPSK channel signal; and c) means for combining the DPSK channel signals from each of the plurality of separate diversity frequency channels for transmission; and wherein said receiver comprising: a) receiver means for receiving and demodulating the transmitted signals to form baseband signals; b) said baseband signals from the receiver means being connected to a plurality of narrowband receiver frequency channels, each receiver frequency channel including a DPSK detector responsive to a respective one of the transmitted DPSK channel frequency signals; c) means for identifying any of said receiver frequency channels corrupted by noise; and d) semi-coherent processing means, responsive to each transmitted data bit, for vectorially adding DPSK detector output signals, excluding said channels corrupted by noise and for producing a combined vector signal phase for determining polarity of each transmitted data bit as a data output signal wherein the transmitter includes a pseudorandom number generator (PNG) connected to the means for combining the DPSK channel signals for modulating the combined channel signals with a pseudorandom code and said receiver includes a demodulator connected to the same coherent processing means for demodulating the transmitted data signal.

Claim 31

Dependent Claim 273 words

A high frequency multichannel communications system having at least a transmitter and a receiver; said transmitter comprising: a) input means for receiving digital signal data for transmission of transmitted data bits: b) the input means, connected to a plurality of Separate diversity frequency channels distributed over a broad spectral region of a high frequency band, each channel including a differential phase shift key (DPSK) modulator, for modulating a channel frequency by successive bits of the digital signal data at a low data rate to produce a DPSK channel signal; and c) means for combining the DPSK channel signals from each of the plurality of separate diversity frequency channels for transmission; and wherein said receiver comprising: a) receiver means for receiving and demodulating the transmitted signals to form baseband signals; b) said baseband signals from the receiver means being connected to a plurality of narrowband receiver frequency channels, each receiver frequency channel including a DPSK detector responsive to a respective one of the transmitted DPSK channel frequency signals; c) means for identifying any of said receiver frequency channels corrupted by noise; and d) semi-coherent processing means, responsive to each transmitted data bit, for vectorially adding DPSK detector output signals, excluding said channels corrupted by noise and for producing a combined vector signal phase for determining polarity of each transmitted data bit as a data output signal wherein the transmitter includes a pseudorandom number generator (PNG) connected to the means for combining the DPSK channel signals for modulating the combined channel signals with a pseudorandom code and said receiver includes a demodulator connected to the same coherent processing means for demodulating the transmitted data signal.

Claim 32

Dependent Claim 58 words

A high frequency multichannel communications system as claimed in claim 23 wherein in the transmitter the DPSK channel signals are generated at 1 bps and the pseudorandom code is generated at 50 bps and in the receiver the received signal is summed over 1 sec intervals for every 50 received bits to determine the transmitted data bit polarities.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1998-06-05	1998-12-05	1999-06-06	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	2002-06-05	2002-12-05	2003-06-06	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	2006-06-05	2006-12-05	2007-06-06	$7700.00	Window Closed / Lapsed

High frequency multichannel diversity differential phase shift (DPSK) communications system

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