Analogue filter systems

Claim 2

An analogue filter system comprising a first analogue filter connected to an input terminal for receiving an input analogue signal, a second analogue filter having similar characteristics to the first analogue filter, delay means connected between the first and second analogue filters for storing the output from said first analogue filter and for producing an output with the time axis thereof inverted under the control of a timing circuit, and means for restoring the inverted time axis of said output, whereby an output analogue signal is produced which is delayed in relation to said input analogue signal but free from any phase distortion.

Claim 3

The analogue filter system according to claim 1 which further comprises an analogue-digital converter interposed between said first analogue filter and said delay means, and a digital-analogue converter interposed between said delay means and said second analogue filter.

Claim 4

An analogue filter system comprising: a first analogue filter connected to an input terminal for receiving an input analogue signal; a second analogue filter having similar characteristics to the first analogue filter; a first analogue to digital converter for receiving an output signal from said first analogue filter; delay means connected to an output of said analog to digital converter for storing the output from said first analogue filter and for producing an output with the time access thereof inverted under the control of a timing circuit, said delay means comprising a N-bit (N being an integer) shift register and a first switching means adapted to be transferred between a first position at which the output of said shift register is fed back to the input thereof and a second position at which said shift register receives the output from said analogue to digital converter, said first switching means being normally thrown to said first position but thrown to said second position in response to an (N-3)th timing pulse from said timing circuit; a digital to analogue converter for receiving an output signal from said delay means; and means for restoring the inverted time access of an output signal of said digital to analog converter, said means for restoring the time access comprising second switching means interposed between said second analogue filter and the output terminal of said filter system, and a capacitor on the output side of said second switching means, said second switching means being normally held open but closed in response to an (N-2)th timing pulse from said timing circuit, whereby an output analogue signal is produced which is delayed in relation to said input analogue signal but free from any phase distortion.

Claim 5

An analogue filter system comprising: a first analogue filter connected to an input terminal for receiving an input analogue signal; a second analogue filter having similar characteristics to the first analogue filter; a first analogue to digital converter for receiving an output signal from said first analogue filter; delay means connected to an output of said analog to digital converter for storing the output from said first analogue filter and for producing an output with the time access thereof inverted under the control of a timing circuit, said delay means comprising a N-bit (N being an integer) shift register and a first switching means adapted to be transferred between a first position at which the output of said shift register is fed back to the input thereof and a second position at which said shift register receives the output from said analogue to digital converter, said first switching means being normally thrown to said first position but thrown to said second position in response to an (N-3)th timing pulse from said timing circuit; a digital to analogue converter for receiving an output signal from said delay means; and means for restoring the inverted time access of an output signal of said digital to analog converter, said means for restoring the time access comprising second switching means interposed between said second analogue filter and the output terminal of said filter system, and a capacitor on the output side of said second switching means, said second switching means being normally held open but closed in response to an (N-2)th timing pulse from said timing circuit, whereby an output analogue signal is produced which is delayed in relation to said input analogue signal but free from any phase distortion.

Claim 6

The analogue filter system according to claim 3 which further comprises means for operating said A-D converter in synchronism with the shifting operation of said N bit shift register.

Claim 7

The analogue filter system according to claim 1 wherein said second analogue filter has a cut off frequency characteristics N times of that of the first analogue filter.

Claim 8

The analogue filter system according to claim 4 wherein said A-D converter is operated by a clock pulse from said timing circuit, and said shift register is operated by a compound pulse train produced by synthesizing first and second pulse trains generated by said clock pulse through a drive circuit.

Claim 9

The analogue filter circuit according to claim 6 wherein said drive circuit comprises a flip-flop circuit supplied with said clock pulse, means for differentiating the leading edge of the output from said flip-flop circuit for producing said first pulse train and means for differentiating and inverting the trailing end of the output from said flip-flop circuit for producing said second pulse train, said first and second pulse trains being synthesized by said shift register.

Claim 10

The analogue filter system according to claim 3, wherein said first switching means comprises an integrated circuit and said second switching means comprises a combination of a transistor and a field effect transistor.

Claim 11

An analogue filter system comprising an input terminal for receiving an input analogue signal, a first analogue filter channel including means for inverting and condensing the time axis of said input analogue signal, a second analogue filter channel connected in parallel with said first analogue filter channel and including means for delaying said input analogue signal, an adder for adding with each other the outputs from said first and second analogue filter channels, and a sampling and holding circuit connected to the output of said adder for restoring the time axis thereof.

Claim 12

An analogue filter system comprising an input terminal for receiving an input analogue signal, a first analogue filter channel including means for inverting and condensing the time axis of said input analogue signal, a second analogue filter channel connected in parallel with said first analogue filter channel and including means for delaying said input analogue signal, an adder for adding with each other the outputs from said first and second analogue filter channels, and a sampling and holding circuit connected to the output of said adder for restoring the time axis thereof.

Claim 13

The analogue filter system according to claim 9 wherein said first analogue channel comprises an A-D converter, a digital memory device for storing the digital output of said A-D converter, said digital memory device including means for inverting and condensing the time axis of the digital signal read out therefrom, a D-A converter for effecting D-A conversion of the digital signal read out from said digital memory device, and an analogue filter connected to the output of said D-A converter and wherein said second analogue channel comprises similar elements to said first analogue channel except that said digital memory device includes means for delaying the digital signal read out therein for a time sufficient to assure impulse response of the filter system.

Claim 14

An analogue filter system comprising an analogue input terminal; a single A-D converter connected to said analogue input terminal; a first channel including means for inverting and condensing the digital output from said A-D converter; a second channel connected in parallel with said first channel and including means for delaying the digital output of said A-D converter; a first analogue filter channel including holding means corresponding to said first channel; a second analogue filter channel including holding means corresponding to said second channel: a single D-A converter; switching means for alternately connecting said D-A converter between said first channel and said first analogue filter channel and between said second channel and said second analogue filter channel; an adder for adding with each other the outputs of said first and second analogue filter channels; and a sampling and holding circuit connected to the output of said adder for restoring the time axis of the analogue signal.

Claim 15

An analogue filter system comprising an analogue input terminal; a single A-D converter connected to said analogue input terminal; a first channel including means for inverting and condensing the digital output from said A-D converter; a second channel connected in parallel with said first channel and including means for delaying the digital output of said A-D converter; a first analogue filter channel including holding means corresponding to said first channel; a second analogue filter channel including holding means corresponding to said second channel: a single D-A converter; switching means for alternately connecting said D-A converter between said first channel and said first analogue filter channel and between said second channel and said second analogue filter channel; an adder for adding with each other the outputs of said first and second analogue filter channels; and a sampling and holding circuit connected to the output of said adder for restoring the time axis of the analogue signal.