Modulation system

Claim 2

A modulation system comprising: a source of modulating signal having a high-frequency portion and a low-frequency portion; a frequency modulator for producing a frequency-modulated signal in response to said low-frequency portion of said modulating signal; a suppressed-carrier amplitude modulator having an input coupled to the output of said frequency modulator for modulating said frequency-modulated signal by said high-frequency portion of said modulating signal to produce a suppressed-carrier amplitude-modulated signal; and means coupled to the outputs of said frequency-modulator and said suppressed carrier amplitude modulator for combining said frequency-modulated signal and said suppressed-carrier amplitude modulated signal to provide a combined modulated signal.

Claim 3

The modulation system of claim 1, further comprising filter means for separating said modulating signal into a high-frequency component and a low-frequency component, said filter means comprising: a low-pass filter for passing the portion of said modulating signal below a predetermined frequency the output of said low-pass filter being coupled to an input of said frequency modulator; and a high-pass filter for passing the portion of said modulating signal above said predetermined frequency the output of said high-pass filter being coupled to an input of said suppressed carrier amplitude modulator.

Claim 4

The modulation system of claim 2, wherein the transfer impedance characteristics of said low-pass filter and said high-pass filter are tapered to provide a gradual transition between said low-frequency portion and said high-frequency portion of said modulating signal.

Claim 5

The modulation system of claim 2, wherein the transfer impedance characteristic of said high-pass filter is independent of the frequency of said modulating signal.

Claim 6

The modulation system of claim 2, wherein the transfer impedance characteristic of said high-pass filter varies with the frequency of said modulating signal.

Claim 7

The modulation system of claim 2, wherein said low-pass filter is characterized by a substantially constant time delay for all frequencies in said low-frequency portion of said modulating signal.

Claim 8

The modulation system of claim 6, wherein said low-pass filter comprises a Bessel filter.

Claim 9

The modulation system of claim 6, wherein said high-pass filter comprises: time delay means for delaying said modulating signal by an amount substantially equal to said time delay of said low-pass filter to produce a delayed modulating signal; and means for subtracting said low-frequency portion of said modulating signal from said delayed modulating signal to produce said high-frequency portion of said modulating signal.

Claim 10

The modulating system of claim 8, wherein said subtracting means comprises: means for inverting said delayed modulating signal with respect to said low-frequency portion of said modulating signal; and means for adding said inverted delayed modulating signal and said low-frequency portion of said modulating signal to provide said high-frequency portion of said modulating signal.

Claim 11

The modulation system of Claim 9, further comprising: means for modifying the frequency response of said high-frequency portion of said modulating signal, and means for applying said modified frequency response high-frequency portion of said modulating signal to the input of said suppressed-carrier amplitude modulator.

Claim 12

The modulation system of Claim 2, wherein the ratio of a. the frequency deviation of said frequency-modUlated signal corresponding to the maximum amplitude of said modulating signal to (b) said predetermined frequency, is at least unity.

Claim 13

A modulation system comprising: filter means for separating a modulating signal into a high-frequency portion and a low-frequency portion; a frequency modulator for producing a frequency-modulated signal in response to said low-frequency portion of said modulating signal; a 90* phase-shifter coupled to the output of said frequency-modulator for producing a 90* phase-shifted frequency-modulated signal; a suppressed-carrier amplitude modulator coupled to the output of said 90* phase-shifter for modulating the 90* phase shifted frequency-modulated signal by said high-frequency portion of said modulating signal to produce a suppressed-carrier amplitude modulated signal; and means coupled to the outputs of said frequency modulator and said suppressed-carrier amplitude modulator for combining said frequency-modulated signal and said suppressed-carrier amplitude modulated signal to produce a combined modulated signal.

Claim 14

A modulation system comprising: filter means for separating a modulating signal into a high-frequency portion and a low-frequency portion; a frequency modulator for producing a frequency-modulated signal in response to said low-frequency portion of said modulating signal; a 90* phase-shifter coupled to the output of said frequency-modulator for producing a 90* phase-shifted frequency-modulated signal; a suppressed-carrier amplitude modulator coupled to the output of said 90* phase-shifter for modulating the 90* phase shifted frequency-modulated signal by said high-frequency portion of said modulating signal to produce a suppressed-carrier amplitude modulated signal; and means coupled to the outputs of said frequency modulator and said suppressed-carrier amplitude modulator for combining said frequency-modulated signal and said suppressed-carrier amplitude modulated signal to produce a combined modulated signal.

Claim 15

The modulation system of claim 12, wherein said suppressed-carrier modulator comprises a balanced amplitude-modulator.

Claim 16

A modulation system comprising: means for separating a modulating signal into a high-frequency portion and a low-frequency portion; a frequency modulator for producing a frequency-modulated signal in response to said low-frequency portion of said modulating signal; means coupled to the output of said frequency modulator for shifting the phase of said frequency-modulated signal by 90*; a suppressed-carrier modulator having an input coupled to the output of said phase shifting means for modulating said phase-shifted signal by said high-frequency portion of said modulating signal to produce a suppressed-carrier modulated signal; and means coupled to the outputs of said frequency modulator and said suppressed-carrier modulator for adding said frequency-modulated signal and said suppressed-carrier-modulated signal to produce a combined output signal.

Claim 17

A modulation system comprising: means for separating a modulating signal into a high-frequency portion and a low-frequency portion; a frequency modulator for producing a frequency-modulated signal in response to said low-frequency portion of said modulating signal; means coupled to the output of said frequency modulator for shifting the phase of said frequency-modulated signal by 90*; a suppressed-carrier modulator having an input coupled to the output of said phase shifting means for modulating said phase-shifted signal by said high-frequency portion of said modulating signal to produce a suppressed-carrier modulated signal; and means coupled to the outputs of said frequency modulator and said suppressed-carrier modulator for adding said frequency-modulated signal and said suppressed-carrier-modulated signal to produce a combined output signal.

Claim 20

The method of claim 15, wherein the step of separating said wide-band information signal into an upper frequency portion and a lower frequency portion comprises the steps of: subtracting said low-frequency portion from said wide-band information signal to produce said high-frequency portion.

Claim 21

The method of claim 16, wherein the step of subtracting said low-frequency portion from said wide-band information signal comprises the steps of: inverting said wide-band information signal; and adding said low-frequency portion to the inverted wide-band information signal to produce said high-frequency portion.

Claim 22

The method of claim 15, further comprising the step of modifying the frequency response of said high-frequency portion of said information signal prior to the step of suppressed-carrier amplitude modulating said high-frequency portion.

Claim 23

A bandwidth reduction system adapted to have applied thereto a video signal extending over a wide frequency spectrum comprising: means for separating the video spectrum into first and second subspectra, the first subspectrum containing predominantly lower-frequency video signal components and the secOnd frequency subspectrum containing predominantly upper frequency components; means coupled to an output of said separating means for wide-deviation frequency-modulating the first subspectrum onto said carrier to produce a frequency-modulated signal; means coupled to the output of said frequency modulating means for suppressed-carrier amplitude modulating the second subspectrum onto said frequency-modulated signal; and means coupled to the outputs of said frequency modulating means and said suppressed-carrier amplitude modulating means for combining the resultant modulated signals to provide over-all modulated signals effectively occupying a band narrower than would be occupied by the entire video signal if said entire video signal were wide-deviation frequency modulated.

Claim 24

A bandwidth reduction system adapted to have applied thereto a video signal extending over a wide frequency spectrum comprising: means for separating the video spectrum into first and second subspectra, the first subspectrum containing predominantly lower-frequency video signal components and the secOnd frequency subspectrum containing predominantly upper frequency components; means coupled to an output of said separating means for wide-deviation frequency-modulating the first subspectrum onto said carrier to produce a frequency-modulated signal; means coupled to the output of said frequency modulating means for suppressed-carrier amplitude modulating the second subspectrum onto said frequency-modulated signal; and means coupled to the outputs of said frequency modulating means and said suppressed-carrier amplitude modulating means for combining the resultant modulated signals to provide over-all modulated signals effectively occupying a band narrower than would be occupied by the entire video signal if said entire video signal were wide-deviation frequency modulated.

Claim 25

A system as in claim 19 further including means for causing a 90* phase shift between said frequency-modulated signal and the amplitude-modulated signal supplied to said combining means.

Claim 26

A system as in claim 19 further comprising a 90* phase shifter between the output of said frequency modulator and an input of said amplitude-modulator.

Claim 27

A system as in claim 1 further comprising a 90* phase shifter between the output of said frequency-modulator and the input of said suppressed carrier amplitude-modulator.

Claim 30

The system of claim 22 wherein said 90* phase-shifter comprises a wide band 90* phase-shifter.

Claim 31

The system of claim 24 wherein said wide band 90* phase-shifter comprises: a divide by two circuit coupled to the output of said frequency modulator, said divide by two circuit having first and second complementary outputs; an inverter coupled to the output of said frequency modulator; a first NAND circuit having a first input coupled to the output of said inverter and a second input coupled to said first complementary output of said divide by two circuit; a second NAND having a first input coupled to the output of said inverter and a second input coupled to said second complementary output of said divide by two circuit; and a flip-flop having a first input coupled to the output of said first NAND circuit and a second input coupled to the output of said second NAND circuit, the output of said flip-flop being connected to an input of said suppressed-carrier amplitude modulator.