JPH0511698B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention is directed to a digital transmission system with a transmission rate of ₀ , in which a logic "1" or "0" is generated within one time slot T = _1/0 [sec]. In order to have bit information, a frequency equal to the transmission speed and a half period of a periodic waveform with twice the period are made to correspond to logical "1" and "0", respectively, and furthermore, between the waveforms in adjacent bits Quadri-
This relates to a transmission method using (Phase) codes.

[Conventional technology]

Conventionally, as a code used in such a transmission method, a function sin θ ( ₀ ≦
Two modes (θ≦2π and −π≦θ≦π) waveforms,
₀ /2 waveform with function sinθ/2 (0≦θ≦2π and −2π≦θ
A method using a waveform of two modes (≦0) has been considered. Here, _{the 0} waveform is set to logic “1”,
The _0/2 waveform corresponds to logic "0". As is clear from FIG. 3, each of logic "1" and "0" has two states. However, in order to maintain phase continuity between waveforms in adjacent bits, the state of the waveform next to the waveform of interest is limited. FIG. 4 shows the state transition. Here, the starting point of the arrow indicates the state of the bit of interest, and the ending point indicates the state of the bit to the right.

According to this state transition diagram, the waveforms show a smooth connection when the state changes from "1" to "1" or from "0" to "0". This situation is shown in FIG.
In this case, the differential coefficients of the waveforms match at the connection points of adjacent bits. For example, in the case of “1”→“1”, it is proven by sin θ′|〓 ₌₂ 〓=sin′θ|〓 ₌₀ =1. However, “1” → “0” or “0” →
The differential coefficients at the state change point of “1” do not match. For example, in the case of “1” part 1 → “0” part 2, sinθ′ | ₌₂ = 1sin′θ/2 = 1/2
This is proven by This situation is shown in FIG.

[Problem to be solved by the invention] In this way, phase continuity is not maintained at the moment of transition from ₀ waveform (sin θ) to _0/2 waveform (sin θ/2) or vice versa. However, there are "corners" at the connection points of the waveforms. This means that unnecessary harmonic components are included. When transmitting using a waveform containing such unnecessary harmonics, there are drawbacks such as being susceptible to distortion in the transmission line and also tending to have an adverse effect on adjacent transmission lines.

SUMMARY OF THE INVENTION An object of the present invention is to provide a transmission system using a quadriphasic code that eliminates the above-mentioned drawbacks.

[Means for solving problems]

According to the present invention, time is plotted on the horizontal axis, voltage amplitude is plotted on the vertical axis, and the time width of T=1/ ₀ obtained by dividing the unit time (1 sec) on the horizontal axis into ₀ equal parts is defined as one time slot. In order to have logic "1" and logic "0" information in the time slot, ₁ , ₂ ,
Considering periodic waveforms ₃ and ₄ , and extracting only the waveforms within a time period equal to one time slot width, these four waveforms are made to correspond to logic "1" and logic "0" (however, one time slot width) Depending on the waveform before the rotor, the next waveform to be transmitted is limited to two types), and four waveforms are set according to the phase continuity condition according to the data to be transmitted (logical "1", "0" information). Sample values of a total of four types of waveforms, a logic "1" waveform with two modes and a logic "0" waveform with two modes, in a transmission method using quadriphasic codes with a transmission rate of ₀ , which performs switching connections while satisfying a memory holding means for storing and holding data in different address areas; a first latch for temporarily storing information for selecting one from four different address areas of the memory holding means; and said memory holding means. a counter for sequentially counting up read addresses within the selected address area of the memory holding means; and a second latch for temporarily storing sample value data of each waveform output from the memory holding means at a stable timing. , a digital/analog conversion circuit that converts the sample value data of each waveform that has passed through the second latch into analog voltage amplitude, and a driver that buffers the analog output, and a connection of each waveform. Thus, a transmission system using a modified quadrature aids code is obtained, which is characterized in that the waveforms are made to correspond so that the differential coefficients match.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

The present invention uses a quartic function (θ) = a + bθ + (cθ) ² + (dθ) ³ + (eθ) 4 that approximates sinθ/2 ( ₀ ≦θ≦2π) with sinθ as a ₀ waveform and sinθ/2 as ^{a 0/2 waveform} . θ = 0 and θ = 2π, the phase is continuous with sin θ, and the differential coefficient of (θ) at θ = 0 is
By selecting the coefficients a, b, c, d, and e to match the differential coefficient of sinθ at θ=2π, the waveform is created by removing unnecessary harmonics that cause “edges” in the waveform. This allows digital transmission to be performed in a narrower band.

Referring to FIG. 1, the transmission method according to an embodiment of the present invention includes sample values of a total of four types of waveforms: a logic "1" waveform having two modes and a logic "0" waveform having two modes. ROM2 that stores and holds data in four different address areas;
The first memory temporarily stores information for selecting one of the four different address areas of this ROM2.
a latch 6, a counter 1 for sequentially counting up read addresses within the selected address area of the ROM 2, and a counter 1 for temporarily storing sample value data of each waveform output from the ROM 2 at stable timing. 2 latch 3
, a digital/analog conversion circuit 4 that converts the sample value data of each waveform passed through the second latch 3 into analog voltage amplitude, and a driver 5 that buffers the analog output.

Next, the state transition from sin θ ( ₀ waveform) to (θ) ( _0/2 waveform) according to this embodiment will be explained with reference to FIG.

(θ) = a + (bθ) + (cθ) ² + (dθ) ³ + (eθ
) In ⁴ , by appropriately selecting the coefficients a, b, c, d, and e, a transmission waveform having the following characteristics can be obtained.

The power of sinθ ( ₀ waveform) and (θ) ( ₀ /2 waveform) are the same, the DC components of sinθ ( ₀ waveform) and (θ) ( ₀ /2 waveform) are balanced, and the connection point between waveforms that can be combined is The differential coefficient (slope) at matches.

As a result, in any case, a smooth connection is possible at the connection point between the waveform sin θ and the waveform (θ), and the effect of removing harmonic components that cause “edges” in the waveform is exhibited.

The operation shown in FIG. 1 will be explained below. sinθ, (θ)
In order to electrically generate the four waveforms obtained from the above, sample value data obtained by sampling each waveform at appropriate time intervals is written into four different address areas of the ROM 2. Latch 6
The read address is counted up and switched within the address area containing the sample value data of the waveform selected from the four waveforms, and the sample value data output corresponding to each address is sent to the D/A via latch 3. lead to converter 4. By temporally changing the analog voltage amplitude as the output of the D/A converter 4, a desired voltage waveform is reproduced in a pseudo manner. The voltage waveform is transmitted by the driver 5 via the transmission line.

〔Effect of the invention〕

As is clear from the above explanation, the transmission method according to the present invention is as follows: ₀ waveform is sinθ, ₀ /2 waveform is (θ) = a + (bθ) + (cθ) ² + (dθ) ³ + (eθ) ⁴
using
Continuous in phase with sinθ at θ=0 and θ=2π, and θ
By appropriately selecting coefficients a, b, c, d, and e so that the differential coefficient at = 0 matches the differential coefficient of sinθ at θ = 2π, unnecessary harmonics that cause "edges" at the connection points of the waveform can be eliminated. By using a waveform with the wave component removed, it is possible to provide a transmission method that enables digital transmission in a narrower band.

[Brief explanation of drawings]

Figure 1 is a block diagram of a transmission system according to an embodiment of the present invention, and Figure 2 is a sinθ ( ₀ waveform) according to the present invention.
→(θ) ( _0/2 waveform). Figure 3 is a diagram showing four types of 1-bit transmission waveforms using ₀ waveform and _0/2 waveform. Figure 4 is 3. A diagram for explaining the phase continuous state transition of the four types of transmission waveforms in the figure, FIG. 5 is a diagram showing the state transition of logic "1" → "1" and logic "0" → "0", Figure 6 shows logic “1”→“0” and logic “0”→
FIG. 3 is a diagram illustrating a state transition of “1”. In Figure 1, 1...counter, 2...
ROM, 3...Latch, 4...D/A converter, 5
...Driver, 6...Latch.

Claims (1)

[Claims] 1. Time is plotted on the horizontal axis, voltage amplitude is plotted on the vertical axis, and the time width of T = _1/0 obtained by dividing the unit time on the horizontal axis into ₀ equal parts is defined as one time slot, and a logic "1" and a logic "1" are assigned to each time slot. In order to have logic “0” information, consider periodic waveforms of ₁ , ₂ , ₃ , and ₄ with two different frequencies and four different phases.
When only the waveforms within a time equal to one time slot width are extracted from each waveform, these four waveforms are made to correspond to logic "1" and logic "0", and the logic "1" and "0" of the data to be sent are set. In a transmission method using a quadriphasic code with a transmission rate of ₀ , which switches and connects four waveforms while satisfying the phase continuity condition according to the information of ``1'', the waveform has two modes; A memory holding means for storing and holding sample value data of a total of four types of waveforms including a logic "0" waveform in different address areas, and information for selecting one of the four different address areas of this memory holding means. A first latch for temporarily storing data, a counter for sequentially counting up read addresses within a selected address area of the memory holding means, and sample value data of each waveform output from the memory holding means. a second latch that temporarily stores the data at a stable timing, a digital/analog conversion circuit that converts the sample value data of each waveform that has passed through the second latch into an analog voltage amplitude, and the analog output of the second latch. A transmission method using a modified quadrature aids code, characterized in that the waveforms are made to correspond to each other so that the differential coefficients match at the connection points of the respective waveforms.