JPH08139639A - Modulation method - Google Patents

Abstract

(57) [Abstract] [Purpose] An object of the present invention is to provide a modulation method that can reduce the load on the frequency synthesizer, achieve high speed, and reduce the product cost. In a spectrum modulation method using a frequency synthesizer, when the difference between the highest instantaneous carrier frequency and the lowest instantaneous carrier frequency is B and the total number of instantaneous carrier frequencies is n, there is a difference between instantaneous carrier frequencies that are temporally adjacent to each other. The frequency difference is set to B / (n-1), the frequency is sequentially increased from the lowest instantaneous carrier frequency in B / (n-1) steps, and after reaching the maximum instantaneous carrier frequency, the frequency is sequentially increased in the same step. After reaching the lowest instantaneous carrier frequency, the frequency step (change) is minimized by repeatedly using the same frequency conversion.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a modulation method used for spread spectrum communication.

[0002]

2. Description of the Related Art Conventionally, a frequency hopping system (hereinafter referred to as FH) spread spectrum system has
For example, as shown in FIG. 2, the carrier frequency is randomly changed with the passage of time. That is, F
In the H method, continuous times t1, t2, t3, ...
..., tn, corresponding to ft1, ft2, ft3, ..., f
The different frequencies of tn are switched and used at high speed.

[0003]

As described above, in the conventional system, the relationship between ft (n-1) and ftn is intentionally set to be random or pseudo-random. This is because the technology was aimed at military communications at the beginning of the study,
It seems that the intention was not to be easily intercepted.

However, the frequency synthesizer used for switching the frequency generally takes time from the time when the switching is instructed until the output frequency is actually stabilized, when a large frequency step (change) is given. However, there is a problem in that this hinders speeding up and eventually leads to an increase in product cost.

It is an object of the present invention to provide a modulation system that can reduce the load on the frequency synthesizer, achieve high speed, and reduce the product cost.

[0006]

According to the present invention, when the difference between the highest instantaneous carrier frequency and the lowest instantaneous carrier frequency is B and the total number of the instantaneous carrier frequencies is n in a spectrum modulation system using a frequency synthesizer. , B / (n-1) is the frequency difference between the temporally adjacent instantaneous carrier frequencies, and the frequency is sequentially increased from the lowest instantaneous carrier frequency in B / (n-1) steps,
After reaching the maximum instantaneous carrier frequency, the frequency is sequentially reduced by the same step, and after reaching the minimum instantaneous carrier frequency, the same frequency conversion is repeatedly used to minimize the frequency step (change). By doing so, it is possible to speed up the frequency synthesizer, and thus to reduce the cost.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is an explanatory diagram showing frequency steps of a spectrum modulation system in a first embodiment of the present invention.

In the first embodiment, in the FH system,
When n frequencies are used and the difference between the highest frequency and the lowest frequency is B, the continuous time t (n
-1) and tn, the frequencies corresponding to ft (n-1) and f
As t, ft-ft (n-1) = B / n is set.

Under these conditions, with the passage of time, ft1, ft2, ft3, ..., ft (n-1), ft
n, ft (n-1), ..., ft3, ft2, ft1,
It is used cyclically as ft2, ft3, ....

According to the above system, the frequency step (change) of the frequency synthesizer is always constant at a minimum, so that the time required for stabilizing the frequency synthesizer can be easily shortened and high-speed switching can be facilitated.

FIG. 3 is an explanatory diagram showing frequency steps of the spectrum modulation method in the second embodiment of the present invention.

In the present embodiment, f (n
A frequency of f ′ (n−1) t is set between −1) t and ftn, and ft1, ft2, ft3, ..., F (n
-1) t, fnt, f '(n-1) t, ..., f't
2, f′t1, ft1, ft2, ft3, ...

In this embodiment, a so-called frequency interleaving effect can be expected in addition to the effect of the first embodiment.

[0014]

As described above, according to the present invention,
By cyclically using small frequency steps (changes), there is an effect that high-speed frequency switching can be easily achieved.

[Brief description of drawings]

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

FIG. 2 is an explanatory diagram showing a conventional example.

FIG. 3 is an explanatory diagram showing a second embodiment of the present invention.

[Explanation of symbols]

ft1, ft2 to ftn ... Frequency corresponding to continuous time t.

Claims (2)

[Claims] 1. In a spectrum modulation method using a frequency synthesizer, when the difference between the highest instantaneous carrier frequency and the lowest instantaneous carrier frequency is B and the total number of instantaneous carrier frequencies is n, the temporally adjacent instantaneous carriers are used. The frequency difference between the frequencies is set to B / (n-1), the frequency is sequentially increased in B / (n-1) steps from the lowest instantaneous carrier frequency, and after reaching the maximum instantaneous carrier frequency, the same step is performed. A modulation method characterized in that the same frequency conversion is repeatedly used after the frequency is gradually decreased and the lowest instantaneous carrier frequency is reached. 2. The modulation system according to claim 1, wherein frequency interleaving is applied between the instantaneous carrier frequencies when the frequency is increasing and when the frequency is decreasing.