JPH05276142A - Rz pseudo noise code generator - Google Patents

Abstract

PURPOSE:To make the power distribution of a spectrum uniform, and to validly utilize a frequency by operating an RZ by multiplying a PN(Pseudo Noise) code by the output of a converting means, and attenuating the frequency components of the PN code more than a prescribed value. CONSTITUTION:A PN code generator 2 generates a PN code in which the pulse width of one chip is (t)1, and DC components are removed, by a clock whose one period is (t)1 generated from a clock generator 1. A duty ratio converter 3 converts the duty ratio of the clock, and generates the clock whose one period is (t)1 and whose duty, ratio is 1: (n). A multiplier 4 multiples the clock by the PN code, and generates an RZ PN code in which the pulse width of one chip is (t)1/(n + 1) Then, the band width of the main lobe is (n + 1) times. A low pass filter 5 allows a signal of a band from the DC to 1/(t)1 to pass, and when the (n) is large to some extent, the power of the spectrum of the PN code is almost uniform, and the PN code whose power distribution is uniform can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pseudo noise code (PN code) generator, and more particularly to an RZ pseudo noise code generator suitable for a spread spectrum communication device.

[0002]

2. Description of the Related Art As shown in FIG. 8, a spread spectrum communication system is a system for obtaining an anti-jamming characteristic by modulating an information signal with a PN code and spreading it over a wide frequency band. Can be seen as a formula. In this case, the power distribution of the spectrum of the multi-carrier information signal is (sinX / X) ² as shown in FIG. 9, so the power distribution of the spectrum of the PN code is (sinX / X). Weighted to type ² .

[0003]

As is apparent from FIG. 9, the power within the main lobe band of the spectrum of the PN code is concentrated near DC and is not uniform. For this reason, most of the information signal transmission contributes near the center of the main lobe of the spectrum, but does not contribute much near the sides. Therefore, the nonuniformity is disadvantageous from the viewpoint of effective use of frequencies. Further, the S / N deterioration due to the frequency selective multipath becomes significant. That is, when the frequency response characteristic of the propagation path as shown in FIG. 10A occurs due to the selective fading, as shown in FIG.
Since the power of the conventional spread spectrum signal is concentrated near the center of the spectrum, it is almost suppressed.

An object of the present invention is, in spread spectrum communication, to eliminate the nonuniformity of the power distribution of the spectrum of the information signal as shown in FIG. 10 (c) so as to effectively use the frequency and improve the S / N. To provide a suitable RZ pseudo-noise code generator.

[0005]

To achieve the above object, an RZ pseudo-noise code generator according to the present invention generates a PN code based on a clock generator and a clock generated from the clock generator. A PN code generator,
Converting means for converting the duty ratio of the clock generated from the clock generator; RZ converting means for multiplying the PN code and the output of the converting means into RZ;
Filter means for attenuating frequency components of the RZ-converted PN code output from the Z-converting means that are equal to or greater than a predetermined value.

[0006]

The PN code obtained by the present invention is RZ coded. Therefore, the power distribution of the spectrum is uniform, and when it is used in the SS communication device, the effective use of the frequency and the S / N deterioration due to the frequency selective multipath can be improved.

[0007]

Embodiments of the present invention shown in the drawings will be described below.
FIG. 1 is an embodiment of an RZ pseudo noise code generator according to the present invention, which includes a clock generator 1, a pseudo noise (PN) code generator 2, a duty ratio converter 3, a multiplier 4, a low pass filter (LPF). ) 5.

FIG. 2 is a time chart for explaining the operation of the above embodiment. First, in the above embodiment, the pseudo noise code generator 2 is the clock generator 1 as shown in FIG.
2 (b) in which the pulse width of one chip is t ₁ and the DC component is removed by the clock whose one cycle is t ₁ generated from FIG.
Generate a pseudo-noise code (PN) as shown in.

As shown in FIG. 2 (c), the duty ratio converter 3 converts the duty ratio of the clock generated from the clock generator 1 so that one cycle is t ₁ and the duty ratio is 1: n. To occur.

Next, the multiplier 4 multiplies the pseudo noise code from which the DC component has been removed by the clock having the duty ratio of 1: n, and the pulse width of one chip as shown in FIG. 2D is obtained. Generate an RZ pseudo-noise code of t ₁ / (n + 1). Here, the waveform of the main lobe of the spectrum is shown in Fig. 3.
In contrast to the pseudo noise code from which the DC component is removed from the pseudo noise code generator 2 shown in (a), the RZ pseudo noise code is as shown in FIG. 3 (b), and the main lobe bandwidth is n + 1. Doubled.

Next, the low-pass filter 5 is a filter for passing a signal in the band from DC to 1 / t ₁ as shown in FIG. 3 (c). If n is large to some extent, R
The power of the spectrum of the Z-coded pseudo noise code is from DC to 1
It can be considered that it is almost uniform up to around / t ₁ .
Therefore, by passing the RZ-coded pseudo-noise code through the filter 5, a pseudo-noise code having a uniform spectrum power distribution is obtained as shown in FIG. However, in FIG. 3, p is electric power and f is frequency.

4 to 6 show an example of the configuration of the multiplier 4. FIG. 7 is a time chart for explaining the operation. In FIG. 4, 11 is a logic circuit, 12 is a switching circuit, the logic circuit 11 is composed of, for example, gates G ₁ and G ₂ as shown in FIG. 5, and FIG. 6 is a configuration example of the switching circuit. It is composed of a pair of transistors Q _A and Q _B , capacitors C ₁ and C ₂ , and resistors R _{1 to} R ₇ .

The pseudo noise code generator 2 outputs a PN code synchronized with the PN clock as shown in FIG. The duty ratio converted PN clock and PN code are given to the gates G ₁ and G ₂ forming the logic circuit 11, and the two signals a shown in FIG.
₁ and b ₁ are generated.

The signals a ₁ and b ₁ are given to the switching circuit of FIG. 6, but since the pattern of the PN code has the property that the numbers of 0 and 1 are almost equal, the capacitors C ₁ and C _{2 are provided.} The DC components of the signals a ₁ and b ₁ are removed by taking out the signals a ₁ and b ₁ to obtain the signals a ₂ and b _{2 shown} in FIG. For the signals a ₂ and b ₂ in FIG. 7, | V ₁ | ≈ | V ₁ '|, | V ₂ | ≈ | V ₂ ' |, | V ₁ | / | V ₂ | ≈ | V ₁ ' The relationship | / | V ₂ '| ≈3 holds.

Next, referring to FIG. 6, in the state of signals a ₂ and b ₂ at t ₁ , the transistor Q _A is on, Q _B is off, and in the state of t ₂ , both the transistors Q _A and Q _B are off, t ₃ In the state of, the transistor Q _A is turned off, Q _B is turned on, and in the state of t ₄ , both the transistors Q _A and Q _B are turned off. As a result, it is possible to obtain an RZ-encoded PN code as shown in FIG. The swing circuit can be replaced with an adder. As the duty ratio converter 3, for example, a known mono-multivibrator is used,
The time constant may be set appropriately.

[0016]

As described above, according to the present invention, a pseudo noise code having a uniform power distribution in the spectrum can be obtained. Therefore, when used in spread spectrum communication, the frequency can be effectively used and the frequency selective multipath can be achieved. It is possible to improve the S / N deterioration due to the above.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a time chart for explaining the operation of the above embodiment.

FIG. 3 is a power spectrum distribution diagram for explaining the operation of the above embodiment.

FIG. 4 is a block diagram showing a configuration example of a multiplier in the above embodiment.

5 is a diagram showing a configuration example of a logic circuit in FIG.

FIG. 6 is a circuit diagram showing an example of the switching circuit of FIG.

FIG. 7 is a time chart for explaining the operation of the multiplier.

FIG. 8 is an explanatory diagram of a spread spectrum communication system.

FIG. 9 is a diagram showing a power distribution of a spectrum of a PN code.

FIG. 10 is a diagram showing a spectrum distribution of an SS signal according to the related art and the present invention.

[Explanation of symbols]

 1 Clock Generator 2 PN Code Generator 3 Duty Ratio Converter 4 Multiplier 5 LPF

Claims (1)

[Claims] 1. A clock generator, a PN code generator for generating a PN code based on a clock generated by the clock generator, and a conversion means for converting a duty ratio of the clock generated by the clock generator. RZ conversion means for multiplying the PN code and the output of the conversion means into RZ, and filter means for attenuating a frequency component of a predetermined value or more of the RZ conversion PN code output from the RZ conversion means, An RZ pseudo-noise code generator characterized by comprising: