Method and apparatus for frequency compensation of electro-mechanical transducer

Claim 2

In combination with an electro-mechanical transducer having mechanical response parameters of known valve and including current-carrying conductor means in a magnetic field wherein the response characteristic of said transducer is a known function of the frequency of the drive current in said conductor means, the improvement comprising: drive circuit means receiving an input signal for supplying a drive current to said current-carrying conductor means of said transducer; and compensation network means in circuit with said drive circuit means for modifying the frequency characteristic and the input signal to be the complement of the frequency response characteristic of said transducer, said compensation network means including resistive, capacitive and inductive components each having a value determined by a corresponding one of the mechanical response parameters of said transducer.

Claim 3

The apparatus of claim 1 wherein said drive circuit means further includes a current amplifier driving said transducer and having a high output impedance relative to the ohmic resistance and self-inductance of said transducer.

Claim 4

The apparatus of claim 2 wherein the frequency response characteristic of said transducer is a velocity response characteristic and said mechanical response parameters of said transducer include mass, a spring value and a dissipation value; and wherein said compensation network comprises said resistive, capacitive and inductive components connected in parallel circuit with each other, said compensation network resistive value being inversely proportional to the dissipation value of said transducer, said compensation network inductive value being inversely proportional to said spring value of said transducer, and said compensation network capacitive value being proportional to the mass of said transducer.

Claim 5

The apparatus of claim 3 further comprising circuit means receiving the output signal of said compensation circuit means for generating an input signal to said current amplifier.

Claim 6

The apparatus of claim 4 further comprising voltage amplifier means receiving said input signal and having a low output impedance relative to the magnitude of the impedance of said compensation network, the output of said voltage amplifier means being coupled to the input of said compensation network.

Claim 7

The apparatus of claim 2 wherein the frequency response characteristic of said transducer is a velocity response characteristic and said mechanical response parameters of said transducer include mass, a spring value and a dissipation value; and wherein said compensation network comprises said resistive, capacitive and inductive components connected in series circuit with each other, said compensation network resistive value being proportional to the dissipation value of said transducer, said compensation network inductive value being proportional to the mass of said transducer, and said compensation network capacitive value being inversely proportional to the spring value of said transducer.

Claim 8

The apparatus of claim 6 further comprising a current amplifier having a high output impedance receiving said input signal and having its output coupled to said compensation network.

Claim 9

The apparatus of claim 2 wherein the frequency response characteristic of said transducer is a displacement response characteristic and said mechanical response parameters of said transducer include mass, a spring value and a dissipation value; and further comprising differentiating circuit means for differentiating the output signal of said compensation network means, the output of said differentiating circuit means being coupled to said current amplifier.

Claim 10

The apparatus of claim 8 wherein said compensation network comprises resistive, capacitive and inductive components connected in series circuit with each other, said compensation network resistive value being proportional to the dissipation value of said transducer, said compensation network inductive value being proportional to the mass of said transducer, and said compensation network capacitive value being inversely proportional to the spring value of said transducer.

Claim 11

In combination with an electro-mechanical transducer including mechanical response parameters of known value and including displaceable means including current-carrying conductor means in a magnetic field wherein the force on said displaceable means depends on the drive current in said conductor means and wherein the resulting velocity response characteristic of said transducer is a known function of the frequency of the drive current, the improvement comprising: compensation network means receiving an input signal and having an impedance characteristic as a function of frequency such that the resulting output signal thereof is the complement of the frequency-dependent velocity response characteristic of said transducer; and amplifier means having an output impedance larger than the impedance comprising the ohmic resistance and self inductance of said transducer and receiving the input signal as modified by said compensation network means for driving said transducer.

Claim 12

In combination with an electro-mechanical transducer including mechanical response parameters of known value and including displaceable means including current-carrying conductor means in a magnetic field wherein the force on said displaceable means depends on the drive current in said conductor means and wherein the resulting velocity response characteristic of said transducer is a known function of the frequency of the drive current, the improvement comprising: compensation network means receiving an input signal and having an impedance characteristic as a function of frequency such that the resulting output signal thereof is the complement of the frequency-dependent velocity response characteristic of said transducer; and amplifier means having an output impedance larger than the impedance comprising the ohmic resistance and self inductance of said transducer and receiving the input signal as modified by said compensation network means for driving said transducer.

Claim 13

The apparatus of claim 10 wherein said amplifier means is a current amplifier having an output impedance which is large in relation to the combined magnitude of the ohmic resistance and self inductance of said transducer for the frequency range over which said transducer is intended to operate.

Claim 14

The apparatus of claim 10 wherein said displaceable means of said transducer has a mass, and a suspension system having a spring value and a dissipation value, said dissipation being representative of friction losses and losses in converting electrical power to acoustic power, said network means including a capacitance value representative of said mass of said displaceable means, an inductance value representative of said spring value for the suspension system of said displaceable means, and a resistance value representative of the dissipation losses of said transducer means.

Claim 15

The apparatus of claim 12 wherein said capacitance, inductance and resistance of said compensation network are connected in parallel, said system further comprising voltage amplifier means receiving the input signal and driving said compensation network means; and shunt resistance means connected between the output of said network means and the input of said current-controlled amplifier and having resistance value which is very much less than the impedance value of said compensation network means for the frequency range over which said transducer is intended to operate.

Claim 16

Apparatus for driving an electro-mechanical transducer including displaceable means and having mechanical response parameters of mass, spring value and dissipation value and exhibiting a known relationship between the velocity of the displaceable means of the transducer and the frequency of a driving signal, comprising: first amplifier means comprising a voltage-controlled amplifier receiving the input signal for amplifying the same; compensation network means having impedance elements each representative of a corresponding electrical equivalent element of a mechanical response parameter of said transducer, said compensation network receiving the output signal of said first amplifier for modifying said signal to have a frequency characteristic which is the complement of the velocity response characteristic of the mechanical response parameters of said transducer; and current amplifier means receiving the output signal of said compensation network means for driving said transducer, said current amplifier having an output impedance which is greater than the magnitude of the impedance of said transducer for the entire frequency range over which said tranducer is intended to operate.

Claim 17

Apparatus for driving an electro-mechanical transducer including displaceable means and having mechanical response parameters of mass, spring value and dissipation value and exhibiting a known relationship between the velocity of the displaceable means of the transducer and the frequency of a driving signal, comprising: first amplifier means comprising a voltage-controlled amplifier receiving the input signal for amplifying the same; compensation network means having impedance elements each representative of a corresponding electrical equivalent element of a mechanical response parameter of said transducer, said compensation network receiving the output signal of said first amplifier for modifying said signal to have a frequency characteristic which is the complement of the velocity response characteristic of the mechanical response parameters of said transducer; and current amplifier means receiving the output signal of said compensation network means for driving said transducer, said current amplifier having an output impedance which is greater than the magnitude of the impedance of said transducer for the entire frequency range over which said tranducer is intended to operate.

Claim 18

Apparatus for driving an electro-mechanical transducer including displaceable means and having mechanical response parameters of mass, spring value and dissipation value, and exhibiting a known relationship between the velocity of the displaceable means of the tranducer and the frequency of the input signal, comprising: first amplifier means comprising a current amplifier receiving the input signal for amplifying the same; compensation network means having impedance elements of resistance, capacitance and inductance, each representative of a corresponding electrical equivalent element of one of said mechanical response parameters, said elements of said compensation network being connected in series circuit and receiving the output signal of said first current amplifier for modifying said signal to have a frequency characteristic which is the complement of the velocity response characteristic of the mechanical response parameters of said transducer; and second current amplifier means receiving the output signal of said compensation network means for driving said transducer, said first and second current amplifiers having respective output impedances which are greater than the magnitude of their associated load impedances for the frequency range over which said transducer is intended to operate.

Claim 19

Apparatus for driving an electro-mechanical transducer including displaceable means and having mechanical response parameters of mass, spring value and dissipation value, and exhibiting a known relationship between the velocity of the displaceable means of the tranducer and the frequency of the input signal, comprising: first amplifier means comprising a current amplifier receiving the input signal for amplifying the same; compensation network means having impedance elements of resistance, capacitance and inductance, each representative of a corresponding electrical equivalent element of one of said mechanical response parameters, said elements of said compensation network being connected in series circuit and receiving the output signal of said first current amplifier for modifying said signal to have a frequency characteristic which is the complement of the velocity response characteristic of the mechanical response parameters of said transducer; and second current amplifier means receiving the output signal of said compensation network means for driving said transducer, said first and second current amplifiers having respective output impedances which are greater than the magnitude of their associated load impedances for the frequency range over which said transducer is intended to operate.

Claim 20

Apparatus for driving an electro-mechanical transducer including displaceable means and having mechanical response parameters of mass, spring value and dissipation value, and exhibiting a known relationship between the displacement of said displaceable means of said transducer and the frequency of a driving signal, comprising compensation network means receiving an input signal and having impedance elements of resistance, capacitance and inductance, each element representative of a corresponding electrical equivalent element of a mechanical response parameter of said transducer, said compensation network means modifying said input signal to have a frequency characteristic which is the complement of the velocity response characteristic of the mechanical response parameters of said transducer; differentiating circuit means receiving the output signal of said compensation network means for differentiating the same; whereby the output signal of said differentiating circuit means is compensated for the displacement characteristic of said transducer; and current amplifier means receiving the output signal of said differentiating network means for driving said transducer, said current amplifier means having an output impedance which is greater than the magnitude of the impedance of said transducer for the frequency range over which said transducer is intended to be used.

Claim 21

Apparatus for driving an electro-mechanical transducer including displaceable means and having mechanical response parameters of mass, spring value and dissipation value, and exhibiting a known relationship between the displacement of said displaceable means of said transducer and the frequency of a driving signal, comprising compensation network means receiving an input signal and having impedance elements of resistance, capacitance and inductance, each element representative of a corresponding electrical equivalent element of a mechanical response parameter of said transducer, said compensation network means modifying said input signal to have a frequency characteristic which is the complement of the velocity response characteristic of the mechanical response parameters of said transducer; differentiating circuit means receiving the output signal of said compensation network means for differentiating the same; whereby the output signal of said differentiating circuit means is compensated for the displacement characteristic of said transducer; and current amplifier means receiving the output signal of said differentiating network means for driving said transducer, said current amplifier means having an output impedance which is greater than the magnitude of the impedance of said transducer for the frequency range over which said transducer is intended to be used.

Claim 22

The apparatus of claim 16 wherein the elements of said compensation network means are connected in series circuit, and said resistive element of said compensation network is proportional to the dissipation value of said transducer, the inductive element of said compensation network means is proportional to the mass of said displaceable means of said transducer, and the capacitive element of said compensation network means is inversely proportional to the spring value of said transducer.

Claim 23

The apparatus of claim 16 wherein the elements of said compensation network means are connected in parallel circuit with each other and said resistive element is inversely proportional to the dissipation value of said transducer, the inductive element of said compensation network means is inversely proportional to the spring value of said transducer, and the capacitive element of said compensation network means is proportional to the mass of the displaceable means of said transducer.

Claim 26

The method of claim 19 wherein said response characteristic of said transducer is a displacement characteristic and further comprising the step of differentiating the output signal of said compensation network and prior to driving said transducer with the modified signal.