Simultaneous amplitude and angle modulation using detection of complex zeroes

Claim 3

A method according to claim 1 wherein the carrier signal is amplitude and frequency modulated and the frequency change imparted to the carrier signal to modulate the carrier signal on occurrence of a k th complex zero approximates to 2σ k /(σ k 2 +t 2 ) radians/second, where σ k is the imaginary root value at the complex zero and t represents time, with t=t k at the time of occurrence of the said k th zero.

Claim 4

A method according to claim 1 wherein the carrier signal is amplitude and phase modulated and the phase change imparted to the carrier signal to modulate the carrier signal on occurrence of a k th complex zero approximates to ##EQU13## radians, where σ k is the imaginary root value at the complex zero and t represents time, with t=t k at the time of occurrence of the said k th complex zero.

Claim 5

Apparatus for modulating a carrier signal using both amplitude and angle modulation, comprising zero detection means for detecting the occurrence, and the imaginary root values, of complex zeros in the first modulating signal, means for angle modulating a carrier signal on the occurrence of at least some complex zeros, the magnitude of the angle modulation being a function of the respective imaginary root values detected for those zeros and of a second modulation signal having not more than three possible values, and modulating means for amplitude modulating the angle modulated signal in accordance with the first modulating signal.

Claim 6

Apparatus for modulating a carrier signal using both amplitude and angle modulation, comprising zero detection means for detecting the occurrence, and the imaginary root values, of complex zeros in the first modulating signal, means for angle modulating a carrier signal on the occurrence of at least some complex zeros, the magnitude of the angle modulation being a function of the respective imaginary root values detected for those zeros and of a second modulation signal having not more than three possible values, and modulating means for amplitude modulating the angle modulated signal in accordance with the first modulating signal.

Claim 7

Apparatus according to claim 4 wherein the carrier signal is amplitude and frequency modulated and the frequency change imparted to the carrier signal to modulate the carrier signal on occurrence of a k th complex zero approximates to 2σ k /(σ k 2 +t 2 ) radians/second, where σ k is the imaginary root value at the complex zero and t represents time, with t=t k at the time of occurrence of the said k th complex zero.

Claim 8

Apparatus according to claim 4 wherein the carrier signal is amplitude and phase modulated and the phase change imparted to the carrier signal to modulate the carrier signal on occurrence of a k th complex zero approximates to ##EQU14## radians, where σ k is the imaginary root value at the complex zero and t represents time, with t=t k at the time of occurrence of the said k th complex zero.

Claim 9

Apparatus according to claim 5 or 6 wherein the zero detection means comprises a plurality of filters, each of the filters having a transfer function e 2 π fσ k with different values of k for each filter and an output with real and imaginary parts, and respective means for each filter for indicating when both the real and imaginary parts of the output of that filter are zero.

Claim 10

Apparatus according to claim 5 wherein the means for angle modulating comprises a number of shift registers, one for each of k imaginary root values, σ k , which can be detected by the zero detection means, each shift register having taps weighted according to samples of the function 2σ k /(σ k 2 +t 2 ) evaluated in the region around t=0 for the value of k corresponding to that shift register; means for summing the outputs from the shift register taps; means for inverting or not inverting the summed output in accordance with the binary value of the second modulating signal which is to be represented; and means for generating a carrier signal; frequency modulated in accordance with the output of the inverting means.

Claim 11

Apparatus according to claim 5 wherein the means for angle modulating comprises at least one shift register having taps weighted according to samples of the function 2σ/(σ 2 +t 2 ) evaluated in the region around t=0 for a respective one of the imaginary values, σ, which can be detected by the zero detection means; means for clocking the shift register when an imaginary root value is detected at a rate dependent on the imaginary root value detected; means for summing the outputs from the shift register taps; means for inverting or not inverting the summed output in accordance with a binary value of the second modulating signal which is to be represented; and means for generating a carrier signal, frequency modulated in accordance with the output of the inverting means.

Claim 12

Apparatus according to claim 6, wherein the means for angle modulating comprises means for generating a ramp signal having a value t-t k as t varies when a complex zero is detected, a first multiplier circuit for multiplying the ramp signal by an inverted version of the carrier signal delayed by 90°, a second multiplier circuit for multiplying the imaginary root value of the currently detected complex zero by the carrier signal, signal processing means for summing the outputs of the multiplier circuits, doubling the frequency of the resultant signal and removing amplitude modulation, and means for inverting or not inverting the signal to the second multiplier circuit in accordance with a binary value of the second modulating signal which is to be represented.

Claim 13

A method of demodulating a signal modulated by a method according to claim 1, wherein the second modulating signal is a binary signal, comprising the steps of envelope detecting the modulated signal to recover the first modulating signal, and phase or frequency detecting the modulated signal to recover the second modulating signal.

Claim 14

A method of demodulating a signal modulated by a method according to claim 1 wherein the second modulating signal is a ternary signal, comprising the steps of envelope detecting the modulated signal to recover the first modulating signal, detecting complex zeros in the recovered first modulating signal, and determing the presence of phase or frequency modulation in the modulated signal, and the sense of any such modulation when a complex zero is detected to recover the second modulating signal.

Claim 15

Apparatus for demodulating a signal modulated by an apparatus according to claim 4 when the second modulating signal is a binary signal, comprising envelope detection means connected to receive the modulated signal and providing the first signal as its output, and phase or frequency detection means connected to receive the modulated signal for recovering the second modulating signal.

Claim 16

Apparatus for demodulating a signal modulated by an apparatus according to claim 4 when the second modulating signal is a ternary signal, comprising envelope detection means connected to receive the modulated signal and providing the first signal as its output, means for detecting complex zeros in the output signal of the envelope detection means, and phase or frequency detection means connected to receive the modulated signal for determining the presence of frequency or phase modulation when a complex zero is detected, and the sense of any such modulation to recover the second modulating signal.

Claim 21

Apparatus for transmitting the amplitude first signal and a binary second signal, comprising zero detection means for detecting the occurrence and the imaginary values of complex zeros in the first signal, means for angle modulating a carrier signal on the occurrence of at least some complex zeros, the magnitude of the angle modulation being a function of the respective imaginary values detected for those zeros and of the second signal, modulating means for amplitude modulating the angle modulated signal in accordance with the first signal, means for transmitting the amplitude modulated angle modulated signal, means for receiving the transmitted signal, means for envelope detecting the received signal and providing the first signal as its output, and means for phase or frequency detecting the received signal for recovering the second modulated signal.

Claim 22

Apparatus for transmitting the amplitude first signal and a binary second signal, comprising zero detection means for detecting the occurrence and the imaginary values of complex zeros in the first signal, means for angle modulating a carrier signal on the occurrence of at least some complex zeros, the magnitude of the angle modulation being a function of the respective imaginary values detected for those zeros and of the second signal, modulating means for amplitude modulating the angle modulated signal in accordance with the first signal, means for transmitting the amplitude modulated angle modulated signal, means for receiving the transmitted signal, means for envelope detecting the received signal and providing the first signal as its output, and means for phase or frequency detecting the received signal for recovering the second modulated signal.

Claim 23

Apparatus for transmitting an amplitude modulated first signal and a ternary second signal, comprising zero detection means for detecting the occurrence and the imaginary values of complex zeros in the first signal, means for angle modulating a carrier signal on the occurrence of at least some complex zeros, the magnitude of the angle modulation being a function of the respective imaginary values detected for those zeros and of the second signal, modulating means for amplitude modulating the angle modulated signal in accordance with the first signal, means for transmitting the amplitude modulated angle modulated signal, means for receiving the transmitted signal, means for envelope detecting the received signal and providing the first signal as its output, means for detecting complex zeros in the output signal of the envelope protection means, and phase or frequency detection means for determining the presence of frequency of phase modulation in the received signal when a complex zero is detected, and the sense of any such modulation in order to recover the second signal.

Claim 24

Apparatus for transmitting an amplitude modulated first signal and a ternary second signal, comprising zero detection means for detecting the occurrence and the imaginary values of complex zeros in the first signal, means for angle modulating a carrier signal on the occurrence of at least some complex zeros, the magnitude of the angle modulation being a function of the respective imaginary values detected for those zeros and of the second signal, modulating means for amplitude modulating the angle modulated signal in accordance with the first signal, means for transmitting the amplitude modulated angle modulated signal, means for receiving the transmitted signal, means for envelope detecting the received signal and providing the first signal as its output, means for detecting complex zeros in the output signal of the envelope protection means, and phase or frequency detection means for determining the presence of frequency of phase modulation in the received signal when a complex zero is detected, and the sense of any such modulation in order to recover the second signal.