JPH11355368A - Phase modulation system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To relieve the linearity of an amplifier of an output stage by placing equidistantly an odd set of signal points on the same circle of a signal space diagram so as to prevent them from passing through the 0 point when being shifted and using an optional even number of those signal points for the transmission data. SOLUTION: A level converter 1 converts the inputted transmission data into a phase angle θ through the level conversion. The angle θ is decided by the placement of signal points of a signal diagram. The converter 1 outputs a cosine signal cosθ or the angle θ to a multiplication product modulator 2 and also outputs a sine signal sinθ of the angle θ to a multiplication product modulator 3 respectively. The modulator 2 multiplies the signal cosθ by a carrier sine wave signal sinωt of angle frequency ω and outputs them to an adder 4. The modulator 3 multiplies the signal sinθ by a carrier cosine signal cosωt of angle frequency ω and outputs them to the adder 4. The adder 4 adds together the signal outputs of both modulators 2 and 3 and outputs them to a BPF.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a phase modulation system.

[0002]

2. Description of the Related Art For example, regarding a phase modulation method, "Digital Mobile Communication System" (Yukiji Yamauchi, published by Tokyo Denki University Press) "Basic of Mobile Communication" (supervised by Yoshihisa Okumura, Masaaki Shinji, published by The Institute of Electronics and Communication Engineers) It is described in "Introduction to Communication Methods" (by Kazuhiro Miyauchi, published by Corona) "Modulation and Demodulation of Digital Wireless Communication" (by Youichi Saito, published by the Institute of Electronics, Information and Communication Engineers).

[0003]

The first problem in the phase modulation system described in the above publication is that the amplifier of the modulation output on the transmission side requires linearity and linearity. The reason is four-valued PSK (4-phase PSK)
Will be described as an example. FIG. 1 is a signal diagram of 4-phase PSK, and FIG. 2 is a configuration of a general transmission system.

[0004] The modulator of FIG. 2 modulates the phase of a transmission carrier to the phases of signal points (A to D) of FIG. The carrier, which is the output of the modulator, has its spectrum shaped by a band pass filter (BPF) in order to prevent interference with adjacent channels. Then, after frequency conversion is performed by the wireless channel control for multi-channel access and the frequency synthesizer, the signal is amplified and transmitted by the amplifier. At this time, if the amplifier performs amplification with poor amplification linearity such as class C amplification, side lobes occur outside the band of the BPF.

Therefore, it is essential to apply an amplifier having good amplification linearity without saturation to the amplifier shown in FIG.
Further, in the signal diagram of FIG. 1, since the signal sometimes passes through the zero point when making a phase transition, the minimum amplitude value of the envelope of the carrier changes to “0”. From this,
The amplification linearity of the amplifier is "0" from the maximum amplitude of the envelope.
It is necessary over a wide range up to.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide a phase modulation system capable of relaxing the linearity of an output stage amplifier.

[0007]

In order to achieve the above object, according to the present invention, an odd number of signal points are arranged at equal intervals on the same circle of a signal space diagram so as not to pass through zero points during transition. Means of using an arbitrary even number of the odd signal points for transmission data is employed. Also,
In the above means, means for using signal points other than signal points used for transmission data for transmitting option data may be used.

[0008]

In the PSK taking even signal points (2n values),
If the phase values are arranged at equal intervals on the same circle centered on the zero point, there is a combination in which the phase of the signal passes through the zero point at the transition. On the other hand, the phase arrangement on the diagram is (2n +
1) By arranging them at equal intervals and using 2n points among them as signal points to be actually used, it is possible to realize a carrier wave that does not pass through 0 points when the phase changes. As an example, FIG. 3 shows the case where n = 2, that is, the case of quaternary PSK. When signal points are arranged as shown in FIG.
When a phase transition occurs in the signal, the distance from the zero point becomes minimum between 0 and P as shown in FIG. That is, the minimum value of the envelope of the carrier does not become “0”. As described above, since the fluctuation of the envelope of the carrier wave is reduced, the range of the amplification linearity of the transmission output amplifier can be reduced.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a phase modulation system according to the present invention will be described below with reference to FIG.

FIG. 5 is a block diagram showing the configuration of the present embodiment. As shown in this figure, the present embodiment includes a level converter 1, two product modulators 2 and 3, and an adder 4. The level converter 1 converts the level of the input transmission data into a phase angle θ. This phase angle θ
Is determined by the arrangement of signal points on the signal diagram. Then, the level converter 1 outputs the cosine signal COS of the phase angle θ.
is output to the product modulator 2 and the sine signal SINθ is output to the product modulator 3.

The feature of this embodiment is that the level converter 1
Is that the arrangement of the signal points in the signal diagram is devised. In the 2n-valued PSK, the signal diagram is divided into 2n + 1, and 2n points are used as signal points corresponding to transmission data. That is, the even value P
Using the constellation of signal points in the signal diagram of the odd-valued PSK for SK, associating the transmitted data with 2n signal points,
The level is converted to the phase angle θ.

The product modulator 2 multiplies the cosine signal COSθ by a carrier sine signal SINωt having an angular frequency ω, and
Output to On the other hand, the product modulator 3 outputs the sine signal SIN
.theta. is multiplied by the carrier cosine signal COS.omega.t of the angular frequency .omega. The adder 4 adds the output signals of the product modulators 2 and 3 and outputs the result to the BPF.

The functional configuration of the transmission system in the present embodiment is the same as the configuration of FIG. 2 described above. The output of the adder 4 is input to the BPF, and only the main lobe is selected, so that the radio channel control and the frequency synthesizer , And then amplified by a transmission amplifier and transmitted to the outside.

Next, when n = 2, that is, a quaternary PSK
As an example, the operation of this embodiment will be described with reference to FIGS.
This will be described in detail with reference to FIG. Note that the present invention is applicable to all PSKs where n is a positive integer, and is not limited to the case where n = 2 described below.

As shown in FIG. 3, the signal points are arranged at equal intervals on the same circle. In order to realize the arrangement of the signal points, the level converter 1 sets the level to a level at which “θ = θA” corresponding to the phase angle θA of the signal point A when the transmission data is data “00”, for example. Convert the data "0
In the case of “1”, “θ =
θB ”, and in the case of data“ 10 ”, the level is converted to a level of“ θ = θC ”corresponding to the phase angle θC of the signal point C. In the case of data“ 11 ”, The level is converted into a level that satisfies “θ = θD” in accordance with the phase angle θD of the signal point D.

The cosine signal COSθ of the transmission data whose level has been converted in this manner is multiplied by the carrier sine signal SINωt in the product modulator 2 and input to the adder 4. Also, the sine signal SIN of the level-converted transmission data
is multiplied by the carrier cosine signal COSωt in the product modulator 3 and input to the adder 4. As described above, by multiplying and adding the carrier sine signal SINωt or the carrier cosine signal COSωt, a modulation signal SIN (ωt + θ) obtained by modulating the carrier having the angular frequency ω with the phase θ can be generated.

The present invention is not limited to the above embodiment, and the following modifications are conceivable. (1) As described above, 2n-valued PSK is extracted from signal points arranged at (2n + 1) points on the signal diagram, 2n points are extracted, and transmission data and signal points are fixed and corresponded. It is also conceivable to change the correspondence between the signal points and the transmission data, or to make the transmission data correspond to the phase transition angle. (2) In the above embodiment, 2n points among (2n + 1) signal points are used for transmission data, but the remaining 1 signal point can be used as an option. (3) In the above embodiment, the odd number of signal points A to E are arranged on the same circle at equal intervals. This takes into account that the error rate of the received signal is lowest. However, if it is possible to sacrifice the error rate to some extent, it is conceivable to arrange the signal points A to E at unequal intervals.

[0018]

As described above, the phase modulation system according to the present invention has the following effects. (1) The first effect is that the linearity of the transmission-side output stage amplifier can be reduced. The reason is that the signal transition on the signal diagram does not pass through the zero point. (2) The second effect is that data and commands other than transmission data can be transmitted using signal points not used as transmission data on the signal diagram. The reason is that signal points other than signal points used for transmission data are used for transmitting option data.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing an example of signal point arrangement in quaternary PSK.

FIG. 2 is a block diagram illustrating an example of a functional configuration of a transmission system using a phase modulator.

FIG. 3 is an explanatory diagram showing an arrangement of signal points according to an embodiment of the present invention.

FIG. 4 is an explanatory diagram showing a minimum value of an envelope amplitude of a carrier in one embodiment of the present invention.

FIG. 5 is a block diagram showing a functional configuration of an embodiment of the present invention.

[Explanation of symbols]

 1 Level converter 2, 3 Multiplier modulator 4 Adder

Claims (2)

[Claims] 1. An odd number of signal points are arranged at equal intervals on the same circle of a signal space diagram so as not to pass through a zero point during transition, and an arbitrary even number of the odd number of signal points is used for transmission data. A phase modulation method characterized by being used for: 2. The phase modulation system according to claim 1, wherein signal points other than signal points used for transmission data are used for transmitting option data.