JPH07112178B2 - Double sideband amplitude modulation phase double transmission system - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a new transmission system in which amplitude modulated signals in wired and wireless are multiplexed by phase doubling.

[0002]

2. Description of the Related Art Conventionally, there are an amplitude modulation transmission system and a frequency division multiplexing transmission system. These methods involve an operation of amplitude-modulating a carrier wave of a certain frequency with a signal containing information. In this operation, the lower sideband and the upper sideband are generated centering on the carrier wave in the frequency space. Even in the case of frequency division multiplexing, the frequency transition of the modulation signal is necessary, but this operation also involves amplitude modulation of the carrier in a broad sense. Therefore, by amplitude-modulating the carrier with the amplitude-modulated modulation signal and the frequency-modulated modulation signal, the amplitude-modulated wave is frequency-division multiplexed, and the frequency-modulated wave is frequency-division multiplexed. Hereinafter, in the present specification, the amplitude modulation is not limited to the meaning of the amplitude modulation of the original signal, and also includes the modulation of the carrier wave that is performed when the frequency of the modulated signal is changed when the various modulated signals are frequency division multiplexed. .

In the above amplitude modulation, only one carrier is used at the same frequency. Therefore,
If all the cosine waves used for modulation in the process of frequency division multiplexing are used as carriers, not only the waves that are modulated when they are transmitted to the transmission line, but one channel is assigned to each carrier.

[0004]

[Problems to be Solved by the Invention]
No transmission method for channel transmission has been proposed. The present invention proposes a transmission method capable of transmitting two channels per carrier.

[0005]

[Means for Solving the Problems]

The configuration of the present invention is
A carrier wave is amplitude-modulated with a first information signal wave containing transmission information, and both sidebands with a first carrier wave are transmitted to a transmission medium. Other oscillation stations detect the first carrier wave from the transmission medium and 1
With respect to the carrier wave, the phase angle differs from the phase angle of the first carrier wave at the receiving point by a predetermined angle α (α ≠ 0, π), the second carrier wave having the same frequency is generated, and the second carrier wave is transmitted. Amplitude-modulating with a second information signal wave containing information, transmitting a carrier-suppressed double-sideband wave to a transmission medium, receiving a wave transmitted through the transmission medium, and using the phase angle at the reception point of the first carrier as a reference, With respect to the phase angle, a phase difference of π / 2 (or −π / 2) and α + π / 2 (or α−π / 2), respectively.
When the second demodulation carrier and the first demodulation carrier having the same phase difference as the frequency of the first carrier are generated and the first information signal wave is detected, it is received on the first demodulation carrier. When the double sidebands are synchronously detected and the second information signal wave is detected, the double sidebands received by the second demodulation carrier wave are synchronously detected.

[0007]

In order to facilitate the explanation, the first information signal wave is

## EQU1 ## S ₁ (t) = F ₁ (ω) cos (ωt + φ ₁ (ω)) (1) The second information signal wave is

## EQU00002 ## Consider a single frequency as S ₂ (t) = F ₂ (ω) cos (ωt + φ ₂ (ω)) (2). When the signal wave is an arbitrary waveform, the above equation may be considered by Fourier integration. Therefore,
When the signal wave is an arbitrary waveform, it can be regarded as the synthesis of the single spectrum in the above equation, and therefore the principle can be understood by analyzing the single spectrum.

A first carrier wave and a second carrier wave used at the time of modulation (hereinafter, referred to as "first modulated carrier wave" and "second modulated carrier wave", and both are collectively referred to as "modulated carrier wave").
Is defined as follows.

[Number 3] _{C 1 (t) = A 1} cos (ω c t + θ) ... (3)

[Number 4] _{C 2 (t) = A 2} cos (ω c t + θ + α) ... (4)

Here, α is a phase angle of the second modulated carrier wave with respect to the first modulated carrier wave. The amplitude-modulated wave at the transmission point (hereinafter referred to as the “modulated wave”) is as follows.

[Number 5] _{E 1 (t) = S 1} (t) C 1 (t) = F 1 (ω) A 1 cos (ωt + φ 1 (ω)) cos (ω c t + θ) ... (5)

[6] _{E 2 (t) = S 2} (t) C 2 (t) = F 2 (ω) A 2 cos (ωt + φ 2 (ω)) cos (ω c t + θ + α) ... ( 6) Hereinafter, the transmission division by the first modulated carrier wave and the second modulated carrier wave will be referred to as the first channel and the second channel.

[0010]

[Equation 7] E ₁ (t) = E _1U (t) + E _1L (t) = F ₁ (ω) A ₁ cos ((ω _c + ω) t + θ + φ ₁ (ω)) + F ₁ (ω) A ₁ cos ((ω _c -ω) t + θ-φ ₁ (ω))… (7)

[Equation 8] E ₂ (t) = E _2U (t) + E _2L (t) = F ₂ (ω) A ₂ cos ((ω _c + ω) t + θ + φ ₂ (ω) + α) + F ₂ (ω) A ₂ cos ((ω _c -ω) t + θ-φ ₂ (ω) + α) (8) where E _1U (t) and E _1L (t) are Upper sideband (USB), lower sideband (LSB), E _2U (t), E
_2L (t) is the upper sideband (USB) and lower sideband (LSB) of the second channel. The transfer function of the transmission line

[0011]

## EQU9 ## Let G (ω) exp (jψ (ω)) (9). Then, both sidebands of the first channel at the receiving point
R ₁ (t) and the double sideband R ₂ (t) of the second channel are as follows.

[Formula 10] R ₁ (t) = R _1U (t) + R _1L (t) = F ₁ (ω) G (ω _C + ω) A ₁ cos ((ω _c + ω) t + θ + φ ₁ (ω) + ψ (ω _c + ω)) + F ₁ (ω) G (ω _C -ω) A ₁ cos ((ω _c -ω) t + θ-φ ₁ (ω) + ψ (ω _c- ω))… (10)

[Equation 11] R ₂ (t) = R _2U (t) + R _2L (t) = F ₂ (ω) G (ω _C + ω) A ₂ cos ((ω _c + ω) t + θ + φ ₂ (ω) + ψ (ω _c + ω) + α) + F ₂ (ω) G (ω _C -ω) A ₂ cos ((ω _c -ω) t + θ-φ ₂ (ω) + ψ (ω _c- ω) + α) (11)

However, R _1U (t) and R _1L (t) are the upper sideband (USB) and the lower sideband (LSB) of the first channel at the receiving point, and R _2U (t) and R _2L ( t) is the upper sideband (USB) and lower sideband (L) of the second channel at the receiving point
SB). Next, the carrier used for synchronous detection at the receiving point (hereinafter referred to as “demodulated carrier”) is defined by the following equation.

[0013]

H (t) = Bcos (ω _C t + θ + ψ (ω _C ) + β) (12) where θ + ψ (ω _C ) is the phase angle at the receiving point of the modulated carrier. β is a deviation phase angle with respect to the phase angle. With the demodulated carrier of formula (12), the following formula is established for the synchronous detection of the reception double sideband R ₁ (t) of the first channel.

[0014]

[Equation 13] D ₁ `(t) = R <sub>1</sub> (t) H (t) = F <sub>1</sub> (ω) G (ω <sub>C</sub> + ω) A <sub>1</sub> cos ((ω <sub>c</sub> + ω) t + θ + φ <sub>1</sub> ( ω) + ψ (ω <sub>c</sub> + ω)) × B cos (ω <sub>C</sub> t + θ + ψ (ω <sub>C</sub> ) + β) + F <sub>1</sub> (ω) G (ω <sub>C</sub> -ω) A <sub>1</sub> cos ((ω <sub>c</sub> -ω ) t + θ-φ <sub>1</sub> (ω) + ψ (ω <sub>c</sub> -ω)) × Bcos (ω <sub>C</sub> t + θ + ψ (ω <sub>C</sub> ) + β)… (13) D <sub>1</sub> `(t) frequency ω _C Letting D ₁ (t) be the detected signal wave with the above components removed, D ₁ (t) is expressed by the following equation.

[0015]

[Equation 14] D ₁ (t) = 1/2 × F ₁ (ω) G (ω _C + ω) A ₁ B × cos (ωt + φ ₁ (ω) + ψ (ω _c + ω) -ψ ( ω _C ) -β) +1/2 × F ₁ (ω) G (ω _C -ω) A ₁ B × cos (ωt + φ ₁ (ω) -ψ (ω _c -ω) + ψ (ω _C ) + β) (14) Similarly, with the demodulated carrier of formula (12), the following formula is established for synchronous detection of the reception double sideband R ₂ (t) of the second channel.

[0016]

[Equation 15] D ₂ `(t) = R ₂ (t) H (t) = F ₂ (ω) G (ω _C + ω) A ₂ cos ((ω _c + ω) t + θ + φ ₂ ( ω) + ψ (ω _c + ω) + α) × B cos (ω _C t + θ + ψ (ω _C ) + β) + F ₂ (ω) G (ω _C -ω) A ₂ cos ((ω _c -ω) t + θ-φ ₂ (ω) + ψ (ω _c -ω) + α) × Bcos (ω _C t + θ + ψ (ω _C ) + β)… (15)

[0017] D ₂ `a detection signal waves ingredients remove frequency omega _C or more components of a (t) and D ₂ (t), D ₂ (t) is expressed by the following equation.

## EQU16 ## D ₂ (t) = 1/2 × F ₂ (ω) G (ω _C + ω) A ₂ B × cos (ωt + φ ₂ (ω) + ψ (ω _c + ω) -ψ ( ω _C ) + α-β) +1/2 × F ₂ (ω) G (ω _C -ω) A ₂ B × cos (ωt + φ ₂ (ω) -ψ (ω _c -ω) + ψ (ω _C ) -α + β) (16) Here, the following assumption is introduced.

(17) G (ω _C + ω) = G (ω _C -ω) (17)

(18) ψ (ω _c + ω) -ψ (ω _C ) = ψ (ω _C ) -ψ (ω _c -ω) ≡ψ (ω) (18)

The assumption of the equation (17) is that the magnitude of the transfer function in the transmission line is the frequency ω _{C in the} upper sideband band and the lower sideband band.
Means to be a subject. Applies to space and coaxial cables. The assumption in Eq. (18) is that the phase difference with respect to the phase at the frequency ω _C of the transfer function in the transmission line is the target for the frequency ω _C between the upper sideband band and the lower sideband band. Means It is established if the phase characteristic of the transfer function in the transmission line is linear with respect to the frequency ω, that is, if there is no dispersion. Usually, space and coaxial cables have no dispersion, that is, can be regarded as non-phase distortion transmission lines.

If the assumptions of the above equations (16) and (17) are introduced, (1
Equations 4) and (16) can be transformed as follows.

## EQU19 ## D ₁ (t) = F ₁ (ω) G (ω _C + ω) A ₁ B cos (ωt + φ ₁ (ω) + Ψ (ω)) cos β (19)

(20) D ₂ (t) = F ₂ (ω) G (ω _C + ω) A ₂ B cos (ωt + φ ₂ (ω) + Ψ (ω)) cos (α-β) (20) ( What can be said from equations (19) and (20) is that if β = π / 2,

[Equation 21] D ₁ (t) = 0 ... (21)

## EQU22 ## D ₂ (t) = F ₂ (ω) G (ω _C + ω) A ₂ B cos (ωt + φ ₂ (ω) + Ψ (ω)) sin (α) (22)

What can be said from the above equation is that if the DSB received wave is synchronously detected with the demodulated carrier wave having the same frequency ω _C , which has a π / 2 phase difference with respect to the phase angle of the first modulated carrier wave at the receiving point, This means that the detection signal wave of the first channel can be set to zero and the second information signal wave of the second channel can be detected.

On the contrary, if the DSB received wave is synchronously detected with the demodulated carrier having the same frequency ω _C and having a phase difference of π / 2 with respect to the phase angle of the second modulated carrier at the receiving point, the second The first information signal wave of the first channel can be detected by setting the detection signal wave of the channel to zero.

Further, the detection output of the detection channel can be maximized by setting the phase difference α between the first modulated carrier wave and the second modulated carrier wave to π / 2. In this way, it is possible to transmit and detect the amplitude-modulated signal waves of the both sideband waves in which the information signal waves of the two channels are multiplexed with the phase double.
In this transmission method, it is necessary to generate the second demodulation carrier and the first demodulation carrier of the same frequency with a phase difference of π / 2 with respect to the phase of the reception points of the first modulation carrier and the second modulation carrier. is there.

The method for this is to use the DS of each channel.
B is transmitted while suppressing the carrier wave, and the reference signal of frequency ω _C which is always equal to the frequency of the modulated carrier wave is transmitted from the master station. It is possible to determine the phase angle at the reception point of the carrier and the second modulated carrier of the second channel.

[0024]

【The invention's effect】

According to the present invention, in one oscillating station, the first carrier wave is amplitude-modulated with respect to the first information signal wave and is transmitted as a double sideband wave with a carrier wave.
It receives a carrier wave, generates a second carrier wave that differs from the first carrier wave by a predetermined phase angle α, and amplitude-modulates the second carrier wave with a second information signal wave to generate a double sideband wave with carrier wave suppression. It is designed to be sent. Therefore, one DS
B enables transmission and reception of information signal waves of two channels.

[0026]

[Embodiment] First, two modulated waves are generated at one transmitting station.
The case of forming and transmitting will be described as a comparative example. Figure 1
2 is a diagram showing the configuration of a transmission system, and the configuration of the oscillation station 10 is shown in FIG. In the transmitting station 10, the first modulated carrier wave represented by the formula (3) whose frequency and phase are locked to the oscillation waveform of the crystal oscillator 50 is the phase comparator 51,
Generated by the voltage controlled oscillator 52. The first modulated carrier wave is generated by the + α phase shifter 54 to have the phase angle advanced by + α, and the second modulated carrier wave represented by the equation (4) is generated.

Then, the first information signal wave of the equation (1) and the first modulated carrier wave are input to the modulation circuit 53 and modulated,
The modulated wave represented by the equation (5) is transmitted to the transmission medium A via the bandpass filter 55 that limits the bands of the both sidebands. The modulated wave propagating through the transmission medium A is a double sideband wave accompanied by the first modulated carrier wave.

On the other hand, the second modulated carrier wave and the second information signal wave are input to the modulation circuit 56 and modulated, and the modulated wave represented by the equation (6) limits the band of the upper sideband wave. 57U, and is transmitted to the transmission medium A via the bandpass filter 57L that limits the band of the lower sideband. The modulated wave propagating through the transmission medium A is a carrier suppressed double sided wave. As a result, the first modulated carrier wave can propagate through the transmission medium A without being disturbed.

In this way, the signals of the two channels are modulated as the two sidebands by being modulated with the same two carriers whose frequencies differ by the phase angle α. The phase relationship of the two carriers does not change at any position on the transmission medium.

As shown in FIG. 1, at each position of the transmission medium A, a large number of receiving stations R are provided. Each receiving station R
Then, the first modulated carrier wave is extracted from the transmission medium A by the crystal filter 11. The signal waveform at the reception point of the first modulated carrier wave is represented by the equation β = 0 in equation (12).

The first modulated carrier wave is input to the phase comparator 12 and compared in phase with the output signal of the voltage controlled oscillator 13. The phase difference is input to the voltage controlled oscillator 13, and the frequency of the signal output from the voltage controlled oscillator 13 is controlled. After all, the signal output from the voltage controlled oscillator 13 and the first
A signal is generated that is phase locked with the modulating carrier. The signal is input to the channel switch 14 and output from the selected reception channel terminal. When demodulating the first information signal wave of the first channel, the channel switch 1
The output of 4 is input to the α + π / 2 phase shifter 15, and (1
The first demodulated carrier wave of the equation of β = α + π / 2 in the equation 2) is generated. When demodulating the second information signal wave of the second channel, the output of the channel switch 14 is π / 2.
It is input to the phase shifter 16, and the second demodulated carrier wave of the equation β = π / 2 in equation (12) is generated.

The first demodulated carrier wave is the synchronous detection circuit 1
I am typing in 7. Further, the signal wave received from the transmission medium A is input to the bandpass filters 19L and 19U, only the both sidebands are extracted and input to the synchronous detection circuit 17. Then, by being synchronously detected by the synchronous detection circuit 17, a detection signal waveform represented by the equations (19) and (20)
D ₁ (t) and D ₂ (t) can be generated. However, since β = α + π / 2, D ₁ (t) of the equation (19) (for the first information signal,
(Represented by a formula similar to formula (22)) is detected, and D ₂
(t) = 0. Therefore, only the first information signal wave is detected.

On the other hand, the second demodulated carrier wave output from the π / 2 phase shifter 16 is input to the synchronous detection circuit 18.
Further, the signal wave received from the transmission medium A is input to the band pass filters 20L and 20U, only the both side bands are extracted and input to the synchronous detection circuit 18. Then, by being synchronously detected by the synchronous detection circuit 17, the detection signal waveforms D ₁ (t) and D ₂ (t) represented by the equations (19) and (20) can be generated. However, since D ₁ (t) and D ₂ (t) are β = π / 2, they are represented by the equations (21) and (22). Therefore, the second
Only the information signal wave is detected.

Next, examples of the present invention will be described. The present embodiment has the configuration shown in FIG. The first channel oscillator station 60 is the same as the circuit for modulating and transmitting the first information signal wave in the first embodiment. The modulated wave of the first information signal wave is a double sideband wave accompanied by the first modulated carrier wave.

A second channel oscillator station 70 is installed at a different position on the transmission medium A. In this second channel oscillator station 70, only the first modulated carrier wave is separated by the crystal band pass filter 71, and the carrier wave whose frequency and phase are locked to the first modulated carrier wave at the receiving point by the phase comparator 72 and the voltage controlled oscillator 73. Is generated. Then, the carrier wave has a phase angle of + α by the + α phase shifter 74.
The second modulated carrier is generated by advancing by α. The second modulated carrier wave and the second information signal wave are input to the modulation circuit 75 and modulated. The modulated wave is transmitted to the transmission medium A via the bandpass filter 76L that limits the band of the lower sideband and the bandpass filter 76U that limits the band of the upper sideband. This modulated wave transmitted through the transmission medium A is a carrier suppressed double-sided wave. Since the carrier wave is suppressed, the first modulated carrier wave present in the transmission medium A is not disturbed.

In the above-described embodiment, the first information signal wave is transmitted as a double sideband wave with a carrier, and the second information signal wave is transmitted as a double sideband wave with carrier suppression. However, the reverse is also possible. In addition, two first carrier waves and two second carrier waves (however, the phase difference between the first carrier wave and the second carrier wave is not 0 or π) that differ by a predetermined phase angle are generated with the common carrier wave as a reference. And then set those carriers first
The information signal wave and the second information signal wave may be modulated to transmit both sidebands for carrier wave suppression and a reference carrier wave. In the reception in this case, a reference carrier wave is received, the first carrier wave and the second carrier wave at the reception point are generated with the carrier wave as a reference, and the phases differ from each other by π / 2. The second demodulation carrier wave and the first demodulation carrier wave may be generated.

In the above embodiment, the detection output can be maximized by setting the angle α of the phase of the second modulated carrier wave to the phase of the first modulated carrier wave to π / 2. In the above embodiment, the transmission medium is a space, but a coaxial cable may be used. If the first information signal wave and the second information signal wave are frequency-multiplexed signals, normal demodulation of the first information signal wave and the second information signal wave with a frequency-multiplexed carrier is performed. Multiple baseband signals can be separated. In addition, since two channels are multiplexed for one modulated carrier wave, when a large number of modulated carrier waves with different frequencies are present in the transmission medium, the reference signal of the frequency corresponding to each modulated carrier wave is detected. In addition, the double sidebands corresponding to the respective reference frequencies may be separated by a filter.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a transmission system according to a specific example of the present invention.

FIG. 2 is a block diagram showing a configuration of an oscillator station in the transmission system according to the embodiment.

FIG. 3 is a block diagram showing a configuration of an oscillator station in a transmission system according to another embodiment.

[Explanation of symbols]

 A ... Transmission medium 10 ... Transmission station 60 ... First channel transmission station 70 ... Second channel transmission station

Claims (4)

[Claims] 1. One oscillator station amplitude-modulates a first carrier wave with a first information signal wave containing transmission information, and transmits a double sideband wave with a first carrier wave to a transmission medium. , The first carrier wave is detected from the transmission medium, and the phase angle is a predetermined angle α (α) with respect to the phase angle of the first carrier wave at the reception point with reference to the first carrier wave.
≠ 0, π), and generates a second carrier wave having the same frequency, amplitude-modulating the second carrier wave with a second information signal wave including transmission information, and transmitting a carrier-suppressed double-sideband wave to the transmission medium. Then, the wave transmitted through the transmission medium is received, and a phase difference of π / 2 (or −π / 2) with respect to the phase angle at the reception point of the first carrier wave as a reference. And α
A second demodulation carrier and a first demodulation carrier having a phase difference of + π / 2 (or α−π / 2) and the same frequency as the frequency of the first carrier are generated, and the first information signal wave is detected. If both sides are received, the both sidebands received by the first demodulation carrier wave are synchronously detected, and when the second information signal wave is detected, the both sidesband waves received by the second demodulation carrier wave are synchronously detected. An amplitude modulation phase double transmission system characterized by the following. 2. The amplitude modulation phase double transmission system according to claim 1, wherein the first information signal wave and the second information signal wave are frequency division multiplexed signal waves. 3. The band of the transmission medium is frequency division multiplexed by providing a large number of sets of the first carrier and the second carrier having the same frequency and different phases. The described amplitude modulation phase double transmission system. 4. The amplitude modulation phase double transmission system according to claim 1, wherein the phase angle α is π / 2 or −π / 2.