Baseline correction circuit

Claim 2

Baseline correction apparatus for subtracting a baseline potential from an input signal occurring with the baseline potential at times not predicted beforehand, comprising: a propagation path; hold and subtract means for receiving a baseline potential applied to it from the propagation path, storing a function of the received baseline potential, and subtracting the stored function from a function of the input signal; and control means for causing said propagation path to have a low rate of propagation when said baseline potential is applied to it and a high rate of propagation when said input signal is applied to it.

Claim 3

Baseline correction apparatus for subtracting a baseline potential from an input signal occurring with the baseline potential at times not predicted beforehand, comprising: a propagation path; hold and subtract means for receiving a baseline potential applied to it from the propagation path, storing a function of the received baseline potential, and subtracting the stored function from a function of the input signal; and control means for causing said propagation path to have a low rate of propagation when said baseline potential is applied to it and a high rate of propagation when said input signal is applied to it.

Claim 4

Baseline correction apparatus for subtracting a baseline potential from an input signal occurring with the baseline potential at times not predicted beforehand, comprising: a propagation path; hold and subtract means for receiving a baseline potential applied to it from the propagation path, storing a function of the received baseline potential, and subtracting the stored function from a function of the input signal; and control means for causing said propagation path to have a low rate of propagation when said baseline potential is applied to it and a high rate of propagation when said input signal is applied to it.

Claim 5

Baseline correction apparatus according to claim 1 in which said control means includes switch means for causing said hold and subtract means to receive said baseline potential and store a fuNction of said baseline potential during one period of time and subtract the function of the baseline potential from the function of the signal during another period of time.

Claim 6

Baseline correction apparatus according to claim 1 in which said control means includes a means for averaging the value of said baseline potential whereby ripple is reduced.

Claim 7

Baseline correction apparatus according to claim 1 in which said control means includes: a low pass filter; means for connecting said low pass filter into said propagation path when said baseline potential is applied to said propagation path without said signal and means for disconnecting said low pass filter from said propagation path when said signal is applied to said propagation path.

Claim 8

Baseline correction apparatus according to claim 4 in which said low pass filter includes: a resistor having a first end and a second end; said first end of said resistor being adapted to receive said baseline potential and said signal; a capacitor having first and second plates; said first plate of said capacitor being electrically connected to said second end of said resistor; a switch having first and second contacts; one of said first and second contacts of said switch being grounded and the other being connected to said second plate of said capacitor; and means for closing said switch when said baseline potential is applied to said propagation path and opening said switch when said signal is applied to said propagation path.

Claim 9

Baseline correction apparatus according to claim 4 including a storage means comprising a common part of said hold and subtract means and said control means, said control means further comprising: sampling means for periodically sampling said baseline potential and applying said baseline potential to said storage means; and means for inhibiting said sampling means when said signal is applied to said propagation path, whereby said storage means stores the function of said baseline potential immediately before said signal is applied to said propagation path.

Claim 10

Baseline correction apparatus according to claim 4 adapted to provide corrected signals to a signal processor, said baseline correction apparatus including a capacitor forming a common part of said control means and said hold and subtract means, said control means further comprising: switch means for causing at least a portion of said baseline potential to be applied to said capacitor when said baseline potential is applied to said propagation path without said signal; said capacitor having a first plate and a second plate; an operational amplifier having an input and an output; said input of said operational amplifier being electrically connected to said first plate of said capacitor and to said switch means; a first resistor having a first end and a second end; a second resistor having a first end and a second end; said second plate of said capacitor being electrically connected to the output of said operational amplifier and to said switch means; said second end of said first resistor being electrically connected to said propagation path; said second end of said second resistor being electrically connected to the output of said operational amplifier and to said switch means; and said operational amplifier being adapted to provide said corrected signals to said signal processor.

Claim 11

Baseline correction apparatus according to claim 7 in which said switch means includes a switch having one contact electrically connected to the input and the other contact electrically connected to the output of said operational amplifier, whereby said input and output are electrically connected when said switch means samples said baseline potential and are opened when said hold and subtract means subtracts said baseline potential.

Claim 12

Baseline correction apparatus according to claim 8 in which said switch means further comprises gating means for closinG said switch periodically when said baseline potential is applied to said propagation path and inhibiting the closing of said switch when said input signal is applied to said propagation path.

Claim 13

Baseline correction apparatus according to claim 8 in which said low pass filter includes: a resistor having a first end and a second end; said first end of said resistor being adapted to receive the baseline potential and said signal; a capacitor having a first plate and a second plate; said first plate being electrically connected to said second end of said resistor and to said hold and subtract means; a second switch having a first contact and a second contact; one of said first and second contacts of said second switch being a movable contact; and one of said first and second contacts of said second switch being electrically connected to said second plate and the other being grounded; said control means including means for making said first and second contacts of said second switch when only a baseline potential is applied to the input of said propagation path and for breaking said contacts when an input signal is applied to the input of said propagation path.

Claim 16

The method of claim 11 in which the step of applying said baseline potential to a storage means at a first propagation rate comprises the step of applying said baseline potential to a propagation path having a first rate of propagation and applying the output from said propagation path to a capacitor.

Claim 17

A method according to claim 12 in which the step of applying the signals at a second propagation rate to a subtractor with said stored baseline potential comprises the step of applying said signals to said subtractor at a faster rate of propagation than that at which said baseline potential was applied to said storage means.

Claim 18

A method according to claim 13 in which said step of applying the signals to said subtractor at a faster rate of propagation comprises the steps of: applying the signals to the input of the same propagation path through which said baseline potential was conducted; and altering the propagation rate at substantially the same time that the signals are applied to it so that it has a faster rate of propagation.

Claim 19

The method of claim 14 in which the step of applying the baseline potential to a storage means at a first propagation rate comprises the step of applying the baseline potential to a propagation path and, while the baseline potential is in the propagation path, connecting a low pass filter to the propagation path, whereby the path of propagation of the propagation path is decreased and the baseline potential is averaged.

Claim 20

A method according to claim 15 in which the step of applying the baseline potential to a storage means comprises the steps of: sampling the potential of the propagation path; applying the sampled potential to a storage capacitor; detecting the presence of an incoming signal to the propagation path; and inhibiting the sampling of the propagation path upon the detecting of the incoming signal whereby the baseline potential occurring just before a signal is detected is stored in the storage means.

Claim 21

A method according to claim 16 in which the low pass filter is disconnected from the propagation path at the same time that the sampling is inhibited.

Claim 22

A method according to claim 17 in which: the step of applying said baseline potential to a storage means comprises the step of applying the baseline potential to a capacitor that is connected between the input of an operational amplifier and the junction between two resistors, one of which is connected to the output of the operational amplifier at its other end; the step of applying said signals at a second propagation rate to a subtractor comprises the steps of applying the signals from the propagation path to the other end of the other resistor, whereby the signal has a polarity that is opposed by said stored baseline potential; and said method further comprising the step of taking the signal minus the stored baseline potential times the function determined by the ratio of the resistances of the two resistors from the output of the operational amplifier and applying it to a signal processor.