Time domain multiplexing apparatus for multiple microphones

Claim 2

A time domain multiplexer for feeding an analogue signal input from a plurality of signal sources along a transmission line, comprising: a. a multiplexer connected by a channel line to each signal source for channel-to-channel switching at switching speeds of about 1.5-2.3×10 6 times/second to produce a sample train from the separate channel signals and convert the analog signals to sample pulses at an individual sample rate of about 225 KHz-275 KHz; b. blanking generator means for producing a time delay of about 100-200 ns between successive sample pulses to prevent sample pulse overlap, thereby reducing cross talk; c. means to superimpose a synchronizing pulse at the end of each complete sample cycle; d. a counter for driving the multiplexer and a demultiplexer; e. a clock generator for producing a clock signal superimposed on the sample cycle and for driving the counters and blanking generator, each sample cycle being identified by a clock signal and synchronizing pulse; f. means for amplifying and driving the synchronizing pulse, clock signal and sample pulse along the transmission line; and, g. a demultiplexer for converting the sample pulses to continuous and discrete analog signals, the demultiplexer being driven by decoders for the synchronizing pulses and clock signal pulses.

Claim 3

A time domain multiplexer for feeding an audio signal input from a plurality of audio signal sources along a single wire, comprising: a. a multiplexer connected by a channel input to each audio signal source for channel-to-channel switching at switching speeds of about 1.5-2.3×10 6 times/second to produce a sample pulse train from the separate channel signals and to convert audio analog signals to sample pulses at an individual sample rate of about 225 KHz-275 KHz; b. blanking generator means for producing a time delay of about 100-200 ns between sample pulses, thereby reducing cross talk; c. means to superimpose a synchronizing pulse at the end of each complete sample cycle; d. a counter for driving the multiplexer and a demultiplexer; e. a clock generator for producing a clock signal superimposed on the sample cycle and for driving the counters and blanking generator, each sample cycle being identified by a clock signal and synchronizing pulse; f. means for amplifying and driving the synchronizing pulse, clock signal and sample pulse along the wire; g. a demultiplexer for converting the sample pulses to continuous and discrete analog signals, the demultiplexer being driven by decoders for the synchronizing pulses and clock signal pulses; and, h. filtering means for converting the demultiplexed analog signals to continuous and discrete analog signals.

Claim 4

A time domain multiplexer for feeding an audio signal input from a plurality of audio signal sources along a single wire, comprising: a. a multiplexer connected by a channel input to each audio signal source for channel-to-channel switching at switching speeds of about 1.5-2.3×10 6 times/second to produce a sample pulse train from the separate channel signals and to convert audio analog signals to sample pulses at an individual sample rate of about 225 KHz-275 KHz; b. blanking generator means for producing a time delay of about 100-200 ns between sample pulses, thereby reducing cross talk; c. means to superimpose a synchronizing pulse at the end of each complete sample cycle; d. a counter for driving the multiplexer and a demultiplexer; e. a clock generator for producing a clock signal superimposed on the sample cycle and for driving the counters and blanking generator, each sample cycle being identified by a clock signal and synchronizing pulse; f. means for amplifying and driving the synchronizing pulse, clock signal and sample pulse along the wire; g. a demultiplexer for converting the sample pulses to continuous and discrete analog signals, the demultiplexer being driven by decoders for the synchronizing pulses and clock signal pulses; and, h. filtering means for converting the demultiplexed analog signals to continuous and discrete analog signals.

Claim 5

The time domain multiplexer of claim 2, in which the audio signal sources are a plurality of microphones.

Claim 6

The multiplexer of claim 2 in which the channel-to-channel switching occurs at about 2×10 6 times/second.

Claim 7

The multiplexer of claim 2 providing a sample duration of about 0.5 microsecond.

Claim 8

The multiplexer of claim 2 in which the sample and blanking pulses have a duration of about 400-670 nanoseconds.

Claim 9

The multiplexer of claim 2 in which the blanking pulse initiates a succeeding sample pulse by about 120 nanoseconds.

Claim 10

The multiplexer of claim 2 in which the channel-to-channel switching speeds vary from about 1.5-2.3×10 6 times/second, at an individual sample rate of about 225 KHz-275 KHz and with a pulse duration varying from about 400-670 nanoseconds.

Claim 11

The multiplexer of claim 2 including a Butterworth filter for conversion of the demultiplexed signals to analog signals.

Claim 12

The multiplexer of claim 9 in which the filter is a two pole, multiple feedback, low pass, Butterworth filter.

Claim 13

The multiplexer of claim 2 in which cross talk is reduced by about 40 dB.

Claim 14

The multiplexer of claim 2 in which the synchronizing pulse is superimposed on the last pulse of a complete sample cycle.