JP3403366B2 - Pulse transmission system and transmitting apparatus therefor - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pulse transmission system for transmitting a frequency-modulated pulse signal and a transmitter for the same.

[0002]

2. Description of the Related Art There is a pulse modulation method as a modulation method used when transmitting information through a transmission line formed of a transmission medium such as an optical fiber. For example, when transmitting an image signal as analog information using an optical fiber, pulsed frequency modulation (hereinafter referred to as “pulsed FM”) or pulsed frequency modulation (hereinafter referred to as “PFM”) is used. In this case, when these pulse modulation methods are used, an analog signal such as an image signal is converted into a pulse train having a constant amplitude and then transmitted, which is advantageous in that it is not affected by the nonlinearity of the light source.

The pulsed FM and PFM are both types of frequency modulation, and the pulse repetition frequency changes according to the transmission information (an analog image signal in the above example). That is, in the pulsed FM, as shown in FIG. 6A, the pulse repetition period T changes according to the transmission information while keeping the duty ratio at 1/2. The frequency spectrum of the modulated wave in this pulsed FM is shown in FIG.
As shown in (b), the receiving side receives the fundamental wave and the sideband of the frequency fo and extracts the transmission information. On the other hand, in the PFM, as shown in FIG.
While keeping w constant, the pulse repetition period T changes according to the transmission information. The frequency spectrum of the modulated wave in this PFM is as shown in FIG.
The frequency component (hereinafter referred to as "low-frequency component") Lo corresponding to the transmission information in the frequency band lower than the sideband of the fundamental wave of o.
Appears. That is, the modulated wave in the PFM contains the transmission information as the low frequency component Lo distant from the sideband of the fundamental wave. Therefore, in the case of pulse transmission by the PFM method (hereinafter referred to as “PFM transmission”), transmission information can be obtained by extracting this low-frequency component Lo from the pulse signal received on the receiving side, so that the demodulation means There is an advantage that it becomes unnecessary.

[0004]

By the way, FIG. 6 (a)
In the conventional pulse transmission in which a rectangular pulse as shown in FIG. 7A or FIG. 7A is used, the transmitted pulse signal contains many harmonics (in the case of an ideal rectangular wave pulse, harmonics are included). Is included infinitely). However, since the band of the transmission line and the amplifier is limited to a predetermined range, there is distortion in the waveform of the pulse signal after transmission as shown in FIG. When such distortion is present, inter-waveform interference occurs, and in the case of PFM transmission, the pulse width, which should be originally constant, fluctuates due to changes in the pulse repetition frequency due to frequency modulation.
That is, in the case of PFM transmission, originally, even if the pulse waveform becomes the waveform shown by the dotted line in FIG. 3 by frequency modulation, the pulse width does not change and ta = tb, but in reality, the pulse repetition frequency Changes, the pulse width fluctuates due to interference between waveforms, and ta ≠ tb. This fluctuation of the pulse width appears as noise (referred to as "low frequency conversion noise") for the low frequency component Lo. Therefore, in PFM transmission, in order to obtain high-quality transmission information with little noise by extracting the low-frequency component Lo on the receiving side, this low-frequency conversion noise must be reduced.
When the transmission information is analog information, this low-frequency conversion noise directly affects the transmission quality, so that reduction of this low-frequency conversion noise is particularly important.

Therefore, according to the present invention, by reducing the above-mentioned low-frequency conversion noise, it is possible to obtain high-quality transmission information with less noise from the low-frequency component of the pulse signal received on the receiving side, and PFM pulse transmission. An object of the present invention is to provide a system and a transmission device therefor.

[0006]

A first aspect of the present invention is a pulse transmission system for transmitting a pulse signal frequency-modulated based on transmission information through a predetermined transmission line and having a duty ratio of 1/2. Based on the transmission information while
Pulsed F consisting of rectangular pulses, frequency-modulated according to
Pulsed FM means for generating M signal and pulsed FM signal
Signal is a frequency-modulated pulse signal with a constant pulse width.
Signal, which is a pulse signal composed of rectangular wave pulses
Wave PFM signal PFM conversion by the differential detection method
Means for receiving the rectangular wave PFM signal and transmitting the rectangular wave PFM signal.
The pulse waveform in the signal is converted into a Gaussian waveform.
A Gaussian filter that outputs a Gaussian-type PFM signal
Port, pulse transmitting means for transmitting the Gaussian PFM signal to the transmission line, and pulse receiving means for receiving the Gaussian PFM signal transmitted to the transmission line. According to the first aspect of the present invention, the transmitted pulse signal is composed of pulses having a Gaussian waveform or a waveform similar to a Gaussian waveform, and these pulses have a small spread in the frequency spectrum despite their small spread in time. Compared to the case of transmitting a pulse signal consisting of pulses,
There is little interference between waveforms and low frequency conversion noise is reduced. Therefore, by extracting only the low frequency component on the receiving side,
It is possible to obtain high-quality transmission information with little noise.

In a second aspect based on the first aspect, a predetermined frequency component lower than a sideband of a fundamental wave in the Gaussian PFM signal is extracted from the Gaussian PFM signal received by the pulse receiving means. By so doing, it is characterized by further comprising a low frequency band extracting means for acquiring the transmission information. According to the second aspect of the invention, since the transmission information is obtained by extracting the low-frequency component that is the predetermined frequency component in the Gaussian PFM signal received on the receiving side, no specific demodulating means is required, and the receiving side is not required. The cost in can be reduced.

[0008]

In a third aspect based on the first aspect, the transmission line is composed of an optical fiber, and the pulse transmission means is the Gaussian PF generated by the PFM means.
The pulse receiving means receives the optical signal from the optical fiber and drives the optical signal by generating a Gaussian PFM signal as an optical signal and transmitting the Gaussian PFM signal to the optical fiber. It is characterized by including a light receiving element for converting into the Gaussian type PFM signal as an electric signal.

A fourth aspect of the present invention is a transmission device for transmitting a pulse signal frequency-modulated based on transmission information to a predetermined transmission path, wherein the transmission is performed while maintaining a duty ratio of 1/2.
A rectangular pulse pattern that is frequency-modulated based on information.
And pulsed FM means for generating a pulse of FM signals, the path
The loose FM signal is frequency-modulated with a constant pulse width.
Pulse signal that is a rectangular pulse
Signal into rectangular wave PFM signal by differential detection method
And PFM converting means that, receive the square wave PFM signal
The waveform of the pulse in the rectangular wave PFM signal is
The Gaussian-type PFM signal
Signal output as a signal, and the Gaussian PF
Pulse transmission means for transmitting the M signal to the transmission path.

[0011]

[0012]

In a fifth aspect based on the fourth aspect, the ratio of the pulse width to the repetition period in the Gaussian PFM signal is 1/3 to 1/2 when the repetition frequency of the Gaussian PFM signal is maximum. Is characterized in that. According to the fifth invention, the ratio of the pulse width to the repetition period in the Gaussian PFM signal is 1 when the repetition frequency of the Gaussian PFM signal is maximum.
Since it is / 3 to 1/2, the harmonic component can be suppressed within a predetermined range while avoiding inter-waveform interference between adjacent Gaussian waveforms in a Gaussian PFM signal.
Low-frequency conversion noise is reduced.

A sixth invention is characterized in that, in the fourth invention, the Gaussian PFM signal is composed of a raised cosine pulse. According to the sixth aspect of the invention, the pulse signal to be transmitted is a squared cosine wave pulse having a small spread of the frequency spectrum in spite of having a small time spread like the Gaussian waveform. As compared with the case of performing, the interference between waveforms is less and the low frequency conversion noise is reduced.

In a seventh aspect based on the fourth aspect , the transmission information is analog information. In the seventh aspect , since the transmission information is analog information,
When the transmission information is obtained by extracting the low frequency component from the pulse signal received on the receiving side, the low frequency conversion noise directly affects the transmission quality. However, according to the present invention, since a Gaussian pulse signal is transmitted, there is little interference between waveforms, and deterioration of transmission quality due to low frequency conversion noise is prevented.

In an eighth aspect based on the fourth aspect , the transmission path is composed of an optical fiber, and the pulse transmitting means is the Gaussian PF generated by the PFM means.
It is characterized by including a light emitting element driven by an M signal to generate the Gaussian PFM signal as an optical signal and send it to the optical fiber.

A ninth aspect of the present invention is a pulse transmission method for transmitting a pulse signal frequency-modulated based on transmission information through a predetermined transmission line, wherein the duty ratio is maintained at 1/2.
A rectangle that is frequency-modulated based on the transmission information while holding
A pulsed F that produces a pulsed FM signal consisting of pulses
The pulse width of the pulsed FM signal is
Is a frequency-modulated pulse signal that has a rectangular wave pattern.
Delayed to square wave PFM signal which is a pulse signal consisting of
And PFM conversion step of converting the detection scheme, the quadrature
The square wave PFM signal is received and converted into the rectangular wave PFM signal.
Pulse signal in which the pulse waveform is converted to a Gaussian waveform
Which outputs as a Gaussian PFM signal
Gusuteppu and a pulse transmitting step of transmitting the Gaussian PFM signal to said transmission path, and the pulse receiving step of receiving the Gaussian PFM signal transmitted to the transmission path, the Gaussian received by the pulse receiving step Low-frequency extraction step of acquiring the transmission information by extracting a predetermined frequency component lower than the sideband of the fundamental wave in the Gaussian PFM signal from the PFM type signal.

[0018]

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. <Structure and Operation of Embodiment> FIG. 1 is a block diagram showing the structure of a pulse transmission system according to an embodiment of the present invention. In this pulse transmission system, a signal obtained by frequency-division-multiplexing a video signal as analog information is used as a transmission information signal Si, and a pulse signal obtained by performing frequency modulation with a constant pulse width (that is, PFM) using this transmission information signal Si. (Hereinafter referred to as "PFM signal") is transmitted by an optical fiber. Such a pulse transmission system is used, for example, in an optical subscriber system.
As shown in FIG. 1, the pulse transmission system according to the present embodiment includes a transmission device 10 that includes an optical heterodyne FM modulator 12, a limiter 22, a PFM converter 24, a Gaussian filter 26, and a transmission laser unit 28 on the transmission side. Each subscriber side, which is a receiving side, is provided with a receiving device 40 including an optical receiving section 42 including an avalanche photodiode (hereinafter referred to as “APD”) 112 as a light receiving element and a preamplifier 114, and a low-pass filter 44. ing. Note that the receiving device 40 does not necessarily have to include the low-pass filter 44, as described below.

The operation of the pulse transmission system having the above configuration will be described below. First, a transmission information signal (a signal in which a video signal is frequency division multiplexed) Si to be transmitted by the above pulse transmission system is input to the optical heterodyne FM modulator 12. The FM modulator 22 is a signal frequency-modulated by the transmission information signal Si (hereinafter referred to as “FM signal”).
That is, Sfms1 is generated. Generated FM signal Sfms1
Is input to the limiter 22. The limiter 22 limits the amplitude of the FM signal Sfms1 to generate the pulsed FM signal S.
Generate fms2. This pulsed FM signal Sfms2 is PFM
Input to the converter 24, the PFM converter 24 converts the pulsed FM signal Sfms2 into the PFM signal Spfm1 by a differential detection method using a circuit including a delay line and an AND gate. The PFM signal Spfm1 is a pulse signal composed of rectangular wave pulses having a constant pulse width as shown in FIG. The PFM signal Spfm1 is input to the Gaussian filter 26, passes through the Gaussian filter 26, and then, as shown in FIG.
A PFM signal (hereinafter referred to as “Gaussian PFM signal”) Sgfm1 composed of Gaussian pulses as shown in (b).
The Gaussian PFM signal Sgfm1 is input to the transmission laser unit 28, and the drive circuit 102 in the transmission laser unit 28
The semiconductor laser 104 is driven by the drive current based on the Gaussian PFM signal Sgfm1. As a result, the semiconductor laser 104 outputs the optical signal Sgfm2 corresponding to the Gaussian PFM signal Sgfm1. This optical signal Sgfm2 is transmitted from the transmission side to the reception side through the optical fiber 30. Therefore, the optical signal Sgfm2 transmitted by the optical fiber 30 is also shown in FIG.
It is a PFM signal composed of Gaussian pulses as shown in (b), that is, a Gaussian PFM signal.

The above-mentioned optical signal Sgfm2 transmitted through the optical fiber 30 is applied to the AP in the optical receiving section 42 in the optical receiving device 40.
The light is received by D112, and the APD 112 receives this optical signal Sgfm2.
To electrical signals. This electric signal is the preamplifier 1
The signal Sgfm3 is output from the optical receiving unit 42 via 14. This signal Sgfm3 is a PFM signal (Gaussian PFM signal) composed of Gaussian pulses as shown in FIG. 2B, and as shown in FIG. 7B, the transmission information signal Si
Is a low-frequency component L distant from the sideband of the fundamental wave of frequency fo
Included as o. The low-pass filter 44 extracts the low frequency component Lo from the Gaussian PFM signal Sgfm3.
The low frequency component Lo is output from the receiving device 40 as an output signal So. As described above, in the present embodiment, since the transmission information is obtained by extracting the low-frequency component Lo from the Gaussian PFM signal Sgfm3, the APD 112 and the preamplifier 114 only need to have a band that can cover the low-frequency component Lo. Is. Therefore, according to the present embodiment,
The cost of the optical receiving unit 42 is reduced as compared with a pulse transmission system such as a pulsed FM system that receives a fundamental wave and its sidebands and extracts transmission information. Further, when transmitting information is obtained by extracting the low-frequency component Lo as in the present embodiment, a simple circuit such as the low-pass filter 44 is sufficient, and a demodulation means is substantially unnecessary.
Also in this respect, the present embodiment is more advantageous than the pulsed FM transmission system.

When the output signal So from the receiving device 40 is input to a device having a tuning circuit (tuning circuit) such as a television receiver or a set top box, these signals are used instead of the low pass filter 44. The low-frequency component Lo can be extracted by the tuning circuit in the device. Therefore, in this case, it is not necessary to provide the low-pass filter 44 as a means for extracting the low-frequency component Lo from the output signal Sgfm3 of the optical receiving unit 42 in the receiving device 40, and the Gaussian output signal from the optical receiving unit 42 is used. Type PFM signal Sgf
You may output m3 directly as the output signal So of the receiver 40.

<Regarding Gaussian Filter> In the conventional pulse transmission system for transmitting a rectangular pulse signal, the waveform of the pulse signal on the receiving side is limited due to the band limitation in the transmission line and the amplifier as described above. , There is distortion as shown in FIG. When such distortion is present, inter-waveform interference occurs and low frequency conversion noise appears. On the other hand, in the present embodiment, the Gaussian PFM signal Sgfm2 is transmitted,
The pulse waveform is a Gaussian waveform as shown in FIG. 2B, and the spread of the frequency spectrum is small in spite of the small spread in time. Therefore, according to the present embodiment, the inter-waveform interference is less and the low frequency conversion noise is reduced as compared with the conventional pulse transmission system that transmits the rectangular wave pulse signal.

However, even when a Gaussian PFM signal is transmitted, when the pulse width is relatively large with respect to the pulse repetition period T, inter-waveform interference occurs (that is, low-frequency conversion noise is generated). Occur). In PFM transmission, since the pulse repetition frequency changes depending on the transmission information, the pulse repetition cycle T also changes accordingly, and the repetition cycle T becomes the minimum when the repetition frequency is maximum (the cycle T at this time is expressed as "Tfmax ]), The repetition period T when the repetition frequency is the minimum
Becomes maximum (the period T at this time is represented by "Tfmin"). Therefore, the degree of inter-waveform interference is evaluated by the ratio t / Tfmax of the pulse width t to the repetition period Tfmax when the repetition frequency is the maximum (hereinafter, this t / Tfmax is referred to as the “relative value of the pulse width at the maximum frequency”). can do. For example, when the relative value of the pulse width t = t1 at the maximum frequency is small as shown in FIG. 4A, the inter-waveform interference is small, but as shown in FIG. As the relative value of t2 increases, the inter-waveform interference increases (t1 / Tfmax <t2 / Tfm
ax). On the other hand, when the pulse width t becomes small, the harmonic component contained in the pulse signal to be transmitted increases. as a result,
The Gaussian waveform after transmission is distorted due to the band limitation of the transmission line and the amplifier. In order to avoid such distortion, it is necessary to widen the band of the transmission line and the amplifier.

Therefore, when a Gaussian PFM signal is created by a Gaussian filter, an appropriate range of the relative value t / Tfmax of the pulse width at the maximum frequency is set in consideration of the degree of inter-waveform interference and the degree of increase of harmonic components. The characteristic of the Gaussian filter must be set so that the relative value t / Tfmax falls within the appropriate range. By the way,
As shown in FIG. 4, when t1 <t2, the cutoff frequency (which corresponds to 1 / t1) of the Gaussian filter for obtaining the Gaussian PFM signal (FIG. 4A) having the pulse width t1 is the pulse width t2. , Which is higher than the cut-off frequency (which corresponds to 1 / t2) of the Gaussian filter for obtaining the Gaussian-type PFM signal (FIG. 4B). Thus, the pulse width of a Gaussian pulse created by a Gaussian filter is
It corresponds to the cutoff frequency of the Gaussian filter. Therefore, in order to set the relative value t / Tfmax of the pulse width at the maximum frequency in an appropriate range, the cutoff frequency of the Gaussian filter may be set to a value according to the appropriate range of t / Tfmax. In the present embodiment, an appropriate range of the relative value t / Tfmax of the pulse width at the maximum frequency is set to 1/3 to 1/1 in consideration of the degree of interference between waveforms and the degree of increase of harmonic components.
2, and the cutoff frequency of the Gaussian filter 26 is set so that this t / Tfmax falls within the range of 1/3 to 1/2. The pulse width is such that the instantaneous amplitude is 1 /
Shall be defined as the time interval between the pulse leading edge point and the pulse trailing edge point, which is 2.

<Effects of the Embodiment> As described above, according to the present embodiment, the waveform of the pulse signal (Gaussian PFM signal) to be transmitted has a Gaussian waveform in which the spread of the frequency spectrum is small in spite of the small spread in time. Therefore, as compared with the conventional pulse transmission system which transmits a rectangular wave pulse signal, there is less inter-waveform interference and the low frequency conversion noise is reduced. On the other hand, the Gaussian PF transmitted in the present embodiment
Since the M signal has a frequency spectrum as shown in FIG. 7B, transmission information can be obtained by extracting the low-frequency component Lo from the Gaussian PFM signal on the receiving side. Therefore, when the low frequency conversion noise is reduced as described above, by extracting only the low frequency component Lo from the Gaussian pulse signal received on the receiving side, it is possible to obtain high-quality transmission information with less noise.

Further, according to this embodiment, the transmission information can be obtained by extracting the low frequency component Lo from the Gaussian PFM signal on the receiving side as described above.
It is sufficient for the light receiving element and the amplifier on the receiving side to have a band that can cover the low-frequency component Lo, and a wide band is not required. Further, the demodulating means such as the PFM converting section as in the receiving device of the conventional pulsed FM transmission system becomes unnecessary. Therefore, according to the present embodiment, it is possible to reduce the cost of the receiving device while suppressing noise in the transmission information extracted on the receiving side.

In a pulse transmission system based on another pulse modulation method such as pulse width modulation, when a Gaussian filter is applied to make the waveform of the pulse signal to be transmitted a Gaussian waveform, the pulse signal is included in the modulated pulse signal. The transmitted information may be lost or changed by passing through the Gaussian filter. However, in this embodiment, since the Gaussian filter is applied to the PFM signal having the constant pulse width, the transmission information is not lost or changed.

<Modification> In the above embodiment, the Gaussian waveform is adopted as the waveform of the pulse signal transmitted through the transmission line. However, if the pulse waveform does not spread in the frequency spectrum although the temporal spread is small, other waveforms are possible. The waveform of may be adopted. That is, even if it is not a perfect Gaussian waveform, a waveform that can be approximately regarded as a Gaussian waveform or a waveform close to a Gaussian waveform, for example, a waveform of raised cosine pulse represented by the following expression f (t) is adopted. You may. When | t | ≦ τ / 2, f (t) = (A / 2) · {1 + cos (2πt / τ)} = A · cos ² (π
t / τ) | t |> τ / 2, f (t) = 0

Further, although the above embodiment has been described on the premise of pulse transmission, that is, optical transmission in which an optical fiber is used as a transmission medium constituting a transmission line, the present invention is
It is not limited to this. For example, the present invention can be applied to pulse transmission using a coaxial cable as a transmission medium, and in that case, the same effect as that of the above embodiment can be obtained.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of a pulse transmission system that is an embodiment of the present invention.

FIG. 2 is a waveform diagram (a) of the PFM signal before passing through the Gauss filter, and PF after passing through the Gauss filter.
Waveform diagram (b) of the M signal (Gaussian PFM signal).

FIG. 3 is a waveform diagram showing a waveform after transmission of a PFM signal composed of rectangular wave pulses.

FIG. 4 is a diagram for explaining inter-waveform interference in a PFM signal composed of Gaussian pulses (Gaussian PFM signal).

FIG. 5 is a diagram showing a frequency characteristic of a Gaussian filter together with a frequency spectrum of a PFM signal.

FIG. 6A is a diagram showing a waveform of a modulated wave in pulsed frequency modulation (pulsewise FM) and FIG. 6B is a diagram showing a frequency spectrum.

7A is a diagram showing a waveform of a modulation wave in pulse frequency modulation (PFM) and FIG. 7B is a diagram showing a frequency spectrum.

[Explanation of symbols]

10 ... Transmitting device 12 ... Optical heterodyne FM modulator 22 ... Limiter 24 ... PFM converter 26 ... Gaussian filter 28 ... Transmission laser unit 30 ... Optical fiber 40 ... Receiving device 42 ... Optical receiver 102 ... Driving circuit 104 ... Semiconductor laser 112 ... APD (avalanche photodiode) 114 ... Preamplifier Lo ... low-frequency component Si ... Transmission information signal Sfms1 ... FM signal Sfms2 ... Pulsed FM signal Spfm1 ... PFM signal Sgfm1 Gaussian PFM signal (transmission side) Sgfm2 Gaussian PFM signal (optical signal) Sgfm3 Gaussian PFM signal (reception side) So ... Output signal of receiving device

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Claims (9)

(57) [Claims] 1. A pulse transmission system for transmitting a pulse signal frequency-modulated based on transmission information through a predetermined transmission path, wherein the duty ratio is maintained at 1/2 and the pulse information is based on the transmission information.
Frequency-modulated, pulsed FM consisting of rectangular pulses
A pulsed FM means for generating a signal, and the pulsed FM signal having a frequency with a constant pulse width
A modulated pulse signal consisting of rectangular wave pulses.
The square wave PFM signal which is a loose signal is detected by the differential detection method.
A PFM converting means for converting the rectangular wave PFM signal, and receiving the rectangular wave PFM signal.
The pulse waveform in the signal is converted into a Gaussian waveform.
Gaussian signal for outputting a Gaussian PFM signal
A pulse transmission system comprising: a filter, pulse transmitting means for transmitting the Gaussian PFM signal to the transmission line, and pulse receiving means for receiving the Gaussian PFM signal transmitted to the transmission line. 2. The transmission information is obtained by extracting a predetermined frequency component lower than a sideband of a fundamental wave in the Gaussian PFM signal from the Gaussian PFM signal received by the pulse receiving means. The pulse transmission system according to claim 1, further comprising a low frequency band extracting means. 3. The transmission path is composed of an optical fiber, and the pulse transmitting means is driven by the Gaussian PFM signal generated by the PFM means to generate the Gaussian PFM signal as an optical signal. The pulse receiving means includes a light emitting element for transmitting to the optical fiber, and the pulse receiving means includes a light receiving element for receiving the optical signal from the optical fiber and converting the optical signal into the Gaussian PFM signal as an electric signal. The pulse transmission system according to claim 1. 4. A transmission device for transmitting a pulse signal, which is frequency-modulated based on transmission information, to a predetermined transmission path, wherein the duty ratio is maintained at 1/2 and the transmission information is based on the transmission information.
Frequency-modulated, pulsed FM consisting of rectangular pulses
A pulsed FM means for generating a signal, and the pulsed FM signal having a frequency with a constant pulse width
A modulated pulse signal consisting of rectangular wave pulses.
The square wave PFM signal which is a loose signal is detected by the differential detection method.
A PFM converting means for converting the rectangular wave PFM signal, and receiving the rectangular wave PFM signal.
The pulse waveform in the signal is converted into a Gaussian waveform.
Gaussian signal for outputting a Gaussian PFM signal
A transmitting apparatus comprising: a filter; and pulse transmitting means for transmitting the Gaussian PFM signal to the transmission path. 5. The ratio of the pulse width to the repetition period in the Gaussian PFM signal is ⅓ to ½ at the maximum repetition frequency of the Gaussian PFM signal. 4. The transmitter according to item 4 . 6. The transmission device according to claim 4 , wherein the Gaussian PFM signal is composed of a raised cosine wave pulse. 7. The transmission device according to claim 4 , wherein the transmission information is analog information. 8. The transmission path is composed of an optical fiber, and the pulse transmission means is driven by the Gaussian PFM signal generated by the PFM means to generate the Gaussian PFM signal as an optical signal. A light emitting device for delivering to the optical fiber is included.
4. The transmitter according to item 4 . 9. A pulse transmission method for transmitting a pulse signal frequency-modulated based on transmission information through a predetermined transmission path, which is based on the transmission information while maintaining a duty ratio of 1/2.
Frequency-modulated, pulsed FM consisting of rectangular pulses
A pulsed FM step for generating a signal and a frequency of the pulsed FM signal with a constant pulse width
A modulated pulse signal consisting of rectangular wave pulses.
The square wave PFM signal which is a loose signal is detected by the differential detection method.
A PFM conversion step for converting, and receiving the rectangular wave PFM signal, and receiving the rectangular wave PFM signal.
The pulse waveform in the signal is converted into a Gaussian waveform.
Phil you output a scan signal as the Gaussian PFM signal
A step of transmitting the Gaussian PFM signal to the transmission line, a pulse receiving step of receiving the Gaussian PFM signal transmitted to the transmission line, and a pulse receiving step of the pulse receiving step. Gaussian PF
A low-frequency extraction step of acquiring the transmission information by extracting a predetermined frequency component lower than a sideband of a fundamental wave in the Gaussian PFM signal from the M signal, the pulse transmission method.