JPS6166430A - Spectrum scramble reception system - Google Patents

Abstract

PURPOSE:To minimize noises of audible level by making a noise spectrum of an output of an FM reception means flat to prevent the noise spectrum from being affected with spectrum scramble. CONSTITUTION:A signal received by a reception antenna 21 is demodulated by an FM demodulation section 22 and outputted from an output terminal 25 via a spectrum descramble section 23 and an integration device 24. The FM demodulation section 22, the spectrum descramble section 23 and the integra tion device 24 are connected in cascade to constitute a processing function, and the descramble section 23 applies spectrum descramble to a demodulation output signal of the FM demodulation section 22 and the descrambled output is integrated by the integration device 24 and a received output is led out.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention is designed to improve the privacy of communications or provide protection against leakage due to frequency interference in communications. This is a reception method for transmitting waves that are scrambled, further emphasized, and modulated, and is a reception method that provides high communication secrecy and prevents deterioration of speech quality due to fading noise generated in the PM transmission path. (Prior Art) FIG. 11 is a functional block diagram showing a conventional confidential reception system, in which 1 is a receiving antenna, 2 is a PM demodulator, 3 is a spectrum descrambler, 4 is an output terminal, and a
, l) indicates the observation point.

Figure 2 is a diagram schematically representing the spectrum of each part of the conventional reception system when simple spectrum inversion is used as the spectrum descrambler.
, (b) are observation points a in Figure 11, respectively.

It corresponds to b.

FIG. 3 is a professional diagram showing an example of the transmission method, where 5 is an input terminal, 6 is a spectrum scrambling section, and 7 is a PM
The transmitter 8 is a transmitting antenna, and c and d indicate observation points.

FIG. 4 is a diagram schematically representing the spectrum of each part of the transmission system, and (c) and (d) correspond to observation points c and d in FIG. 3, respectively.

A conventional reception system of this kind uses a configuration in which a spectrum descrambler section 3 is cascaded to a PM demodulation section 2 as shown in FIG. As a prerequisite for receiving radio waves, the demodulated signal obtained by PM demodulation is subjected to spectrum descrambling (in particular, simple spectrum inversion is considered), and the secret signal is decoded and reproduced. The period from when the phase modulated signal is emitted until it is received by the receiving antenna is
It is called an M transmission line, and when the PM transmission line forms a standing wave electric field and 7E/G noise is mixed in the received demodulated signal, it is especially called a fading PM transmission line.

Mobile communications such as car telephones are often affected by fading noise. FIG. 5 shows the average power spectrum of noise in such a fading PM transmission path. In Figure 5, the reception level 10 dBμ indicates the electric field at the edge of the car phone service area, 20 dBμ indicates the electric field at the center of the same area, and the reception level across the entire area is 20 dB.
/decade (An integral property kffl having a D slope. Therefore, it is shown schematically as shown in the shaded area in FIG. 2 (, ).

Since the demodulated signal contains fading noise as shown in the shaded area in FIG. 2(a), it is converted into triangular noise as shown in FIG. 2(b) by the overlap tram inverter 3.

When the F'M demodulation function is used in place of the PM demodulation function, fading noise having a tractram is mixed into a flat field as shown in FIG. 6 (11). PM in Figure 6 (1)
It also shows the fading noise when the simple spectrum is inverted during demodulation and (iii) KPM demodulation. These three turns show a typical noise power spectrum, and their auditory level 'jiZwicke'
Table 1 shows the analytical values using the r method and the experimentally determined values. Table 1
As shown in Figure 3, even if the noise power is kept the same for the 3 main turns, the flat type is approximately 4 dB higher than the lowest level for the inverted triangle, and the noise power for the flat type is approximately 4 dB higher than the inverted triangle at the highest level. It is heard 10dB higher.

From this, when using the secret message receiver shown in Fig. 11, the SNH is 10 dB (
It is known that communication quality (power) may deteriorate.

(The rest of the article) As a method to prevent the deterioration of this reception S, a secret receiver is used in which a differential function section is added to the front end of the spectrum scrambling section, and an integral function section is added to the rear end, as shown in Figure 7. The system has been disclosed by the applicant (Japanese Patent Application No. 1983-
179395). This method is used to receive a PM modulated wave emitted using the confidential message transmitter shown in FIG. 8 and to decode the confidential message. In FIG. 7, 9 is a receiving antenna, 10 is a PM demodulation section, 11 is a differential function section, 1
2 is a spectrum descrambling section, 13 is an integral function section, and e=h is an observation point. In Figure 8, 15
1 is an input terminal, 16 is a differential function section, 17 is a spectrum scrambling section, 18 is an integration function section, 19 is a PM transmission section, and 1 to t are observation points. Figure 9 shows the spectrum at each observation point in Figure 7, and (e) to (h) are
Corresponds to observation point ez h. FIG. 10 shows the spectrum at each observation point in FIG. 8, and 0) to (4) correspond to observation points 1 to t, respectively.

The spectrum in Figure 9.10 is shown schematically,
Now, it is assumed that a signal having the spectrum shown in FIG. 10(i) is input to the input terminal 15 in FIG. 8. After the input signal is differentiated by 16 and becomes as shown in FIG. 10(j), it is encrypted by a spectrum scrambler 17 and scrambled on the frequency domain as shown in FIG. 10(k). The scrambled signal is then integrated by 18,
Figure 10 (spectrumed as shown in 4, PM modulated at 19, and emitted from 20 antennas.
The radio waves propagated through the M transmission path are received by 9 antennas and sent to the IO
It is demodulated by a PM demodulator.

As shown in Figure 9(,), the spectrum of PM demodulation is
It has a shape equivalent to Figure 0 (4). The demodulated output of 10 is 1
The signal is differentiated by 1 and the spectrum is corrected as shown in FIG. 9(f). Note that the noise component is flat as a characteristic of the spectrum in (f). Due to the noise characteristics of (f),
Noise characteristics can be maintained unchanged even if tractram descrambling is applied to any system at a total of 1O.

On the other hand, the signal components are affected by spectrum descrambling as shown in FIG. 9(g). The signal subjected to spectrum descrambling is integrated at 13 in Fig. 7 and shown in Fig. 9 (h
) has a spectrum like this. It is clear that the spectra of the input signal in Figure 10 (i) and the signal component in Figure 9 (h) are equal to each other, and that the noise in Figure 9 (h) forms the inverted triangular spectrum in Figure 6 (1). become. Figure 7 1
If the spectrum descrambler shown in Fig. 2 and the spectrum scrambler shown in Fig. 8 17 have opposite characteristics of the spectrum scramblers, such as S(*) and 5-1 (*), then the spectrum descrambler shown in Fig. 10 (i) and Fig. 9 The above relationship in figure (h) is maintained.

As mentioned above, the applicant has already disclosed a method for solving the drawbacks of the conventional method, but this method has a secret function 12 and a PM receiving function as shown in FIG. In addition to the essential functions of 10, additional functions of differential function 11 and integral function 13 are required, and when realized by a circuit, the circuit becomes complicated and economically expensive.

(Problems to be Solved by the Invention) As described above, the conventional PM demodulation method has the drawbacks that the noise characteristics are affected by the spectrum scrambler and the circuit configuration is complicated.

(Means for Solving the Problems) The present invention is characterized in that, in a method for receiving spectrum-scrambled and phase-modulated transmitted waves, an F'M receiving means for frequency demodulating the received waves, and an F'M receiving means connected to the output thereof, are used. The present invention is a PM signal receiving system comprising a spectrum descrambling means and an integrating means connected to the output thereof.

(Function) According to the above configuration, the noise spectrum of the output of the FM receiving means is flat, so the noise spectrum is not affected by spectral scrambling, and the noise spectrum of the output of the integrating means has a so-called inverted triangle shape.
Hearing level noise can be minimized.

(Example) It is well known to those skilled in the art that a PM signal can be demodulated by an FM demodulator and an integrating means.
972, 9, 30), and is described on page 51 of the book ``Mobile Communication System'' (written by Masanobu Watanabe).

The present invention advances this technology.

FIG. 1 is a functional block diagram showing one embodiment of the present invention, in which 21 is a receiving antenna, 22 is an FM demodulation section, 23 is a basic spectral descrambling section, 24 is an integrating section, and 25 is an output terminal section. , where m, n, and o each indicate an observation point. FIG. 12 is a diagram schematically representing the spectrum of each observation point in the embodiment of the present invention.
(n), (,) are the points m r n * O in Figure 1
It corresponds to

In FIG. 1, an FM receiving section 22, a spectrum descrambling section 23, and an integrating section 24 are connected in cascade to form a processing function. When receiving the PM modulated wave emitted by the already disclosed spectrum scramble transmitter shown in FIG. 8 using such a processing function, each point in FIG.
The spectrum shown in Fig. 12 is generated, the spectrum of the input signal in Fig. 10 (i) is correctly received as shown in Fig. 12 (0), and the fading noise forms the inverted triangle shown in Fig. 6 (i). It can be seen that the call quality does not deteriorate compared to when receiving PM without using the confidential message at all. Here, it will be explained that the FM demodulated output signal has a spectrum as shown in Fig. 12 h).

FIG. 13 is a diagram showing a detailed configuration example of the PM demodulation section.

In the figure, 26 is the input terminal of the PM demodulator, 27 is the F
'M demodulator, 28 is an integral filter, and 29 is an output terminal of the PM demodulator. This configuration is an example of a configuration of a PM demodulator that uses an FM demodulator, focusing on the excellent operational stability of the FM demodulator.

When the PM demodulation means having the configuration shown in FIG. 13 is applied to the 10 PM demodulation means of the conventional spectrum scrambling reception system (Japanese Patent Application No. 58-17939.5) disclosed by the present applicant shown in FIG. 7, FIG. A spectrum scrambling reception system having the configuration shown in FIG.

In FIG. 15, 30 is a receiving antenna, 31 is an FM demodulating means, 32 is an integrating means, 33 is a differentiating means, 34 is a spectrum descrambling means, 35 is an integrating means, 36 is an output terminal, and r and set are observation terminals. Show points. In the same figure, 33 differentiation and 35 integration are addition means, and 31
F'M demodulation at 32, integration at 32, and spectrum descrambling at 34 are essential means.

FIG. 16 shows an example of implementation of the overlapping tram scrambler means. In FIG. 16, 40 is an input terminal, 41 is a mixer, 42 is a local oscillator, 43 is a low/cess filter, 4
4 to 46 are switches, 47 to 49 are band cess filters, 50 to 52 are doublexers, 53 to 55 are variable frequency local oscillators, 56 to 58 are low cess filters with adjustable cutoff frequencies, and 59 are adders. 60 is an output terminal, EA.

EB, ..., EP are observation points. The spectrum appearing at each of these points is shown in Figure 17 (EA) to (EM
).

In FIG. 17, (EA) to (EM) correspond to points EA-EM, respectively. The frequency of the local oscillator 42 is fl+f
2 (=fo) is fixed, the cutoff frequency of the low and low bass 43 is f2, and the passbands of the bass/tonos filters 47 to 490 are Cft, ft+1w), Cft+1w
, fl-V2fvt].

Cf2-fw, fz). here f
w = (fz-ft)/m, which is determined by the number of band divisions m of the input signal and the input bandwidth Cfz-ft). Here, the case where the number of band divisions m is 3 will be explained, but the explanation will be omitted since the analogy can be easily made even when m is other than 3. The oscillation frequency of the variable local oscillator 53 is 2(f1+
fw), 54 is 2(ft+1w), 55 is 2fz f
w (!: L, the cutoff frequency of the variable cutoff flow filter is 56 t” ft+2fw,
57k ft + fw, 58 t f2, and set the switch 44 to the EA side, 45 to the iEB side, and 46 to the EA side.

The spectrum shown schematically in Figure 17 (EA)? When a signal with a value of (EB
), a signal with a simple spectrum inversion appears. (EA) and (EB) are band gas filter 4
With the filter puncture formed by 7 to 49 (EA),
The signal is divided into m bands as shown by dotted lines in (EB). In the figure, it means the signal components existing in the bands of 1, 2, and 3Fi input signals, and as shown in (EB), 11%1.3/ indicates that each component is inverted. 44 and [7'J Sat, (EA
) to extract the first component of EC), the spectrum of EC) is the point EC
appears in Product of output of 53 and output of 47 total mixer 5
0 is output, and the spectrum of the output signal is shown in Figure 17 (
It becomes a double-sided wave like ED). Only the lower side of this both-side wave 56
When extracted, a spectrum (EE) appears at point EE.

This operation inverts the component l and shifts only the frequency fw. Due to the action of 45 and 48, the spectrum (
After EF) is extracted, the mixer 51 modulates it with the output signal of the local oscillator 54, and the lower sideband of the modulated wave is extracted at 57 to obtain the spectrum (gH). During this time, component 2 is
Only the frequency fw is shifted downward.

After being extracted at 46 and 49, the third signal component 3 is modulated by the output of the local oscillator in a mixer 52, extracts the lower sideband of the modulated wave, and undergoes a spectrum inversion operation in the same frequency range. If the sum of the three signals at the three points EE, EH, and EL is calculated using 59 adders, a spectrum (EM) appears at the point EM.

As can be clearly seen by comparing the spectra (EA) and (EM), each component depends on the state of the switches 44 to 46 and the frequency of the local oscillators 53 to 55 in the spectrum scrambling pattern of 2"mj. You get a turn. Now (EM
), if the pattern shown is used as scrambled output, descrambling can be done by performing the reverse of this operation. That is, (
The spectrum (EA) of the source signal can be found by shifting component ltfw upward in EM), inverting component 2, shifting downward only fW, and inverting component 3. Such spectrum descrambling means has 44 in FIG. 16 on the EB side and 44 in FIG.
Set 5 to the EA side and 46 to the EB side, and set the oscillation frequencies of the local oscillators 53 to 55 to 2f t + 3.
fw, 54 to 2Cfl+fvi), 55 to 2 (f
t +2fw), and the cutoff frequencies of 56 to 580 Ronox filters are set to 56tfz and 57t, respectively.
This can be achieved by setting ft+fw and 58 to ft+2fv.

By the way, the differentiating means uses the input signal G(,?'') t, fG
The integrating means has a function of converting the input signal F(f)t into a spectrum of f-2F(f). Here, f indicates the frequency.

In Fig. 15, the fact that the spectrum of observation point t is equal to the spectrum of r can be understood from the fact that the integral of 32 and the differential of 33 cancel each other out (f''''・f=1). In other words, Even if the FM demodulation output of 31 is directly subjected to spectral descrambling, the FM demodulation output (corresponding to point S in Fig. 15) as shown in Fig. 7 can be differentiated and then spectrum descrambled. They match correctly when they are equal.Therefore, it is shown that the ctram at point m in the embodiment of the present invention becomes as shown in FIG. 12(e).

Returning the discussion to Figure 15. The configuration obtained when the integral of 32 and the differential of 33 are canceled out and the output of 31 is led to the descrambler of 34 constitutes the present invention. The demodulating means and the integrating means 24 are each part of the PM demodulating means. It is clear that FIG. 11 actually has a structure in which the spectrum descrambler 23 is inserted at the point P of the FM demodulation shown in FIG. 13, and does not have any additional means for cutting.

As explained above, according to the method of the present invention, the confidentiality of communication can be increased by using the F'M demodulation hand, the spectrum descrambling means, and the integrating means in tandem. The first advantage is that the noise mixed in during reception can be completely prevented from deteriorating the speech quality due to deformation during descrambling, and the second advantage is that the present invention does not use any additional means. A fourth advantage is obtained that the circuit molding cost does not increase at all when applied.

The explanation above has focused mainly on the auditory noise level, with emphasis on preventing deterioration of call quality and disclosing technology for realizing it economically. The following describes the spectrum inversion rumble reception method disclosed in the present invention and the already disclosed spectrum scramble transmission method shown in FIG.
0636), a new effect of improving confidentiality and interference resistance in the PM transmission path is produced.

A signal representing power G(f) is input to the input terminal of FIG. 815. A signal with power T(f) is obtained at point t by means of differentiation 16, scrambler 17, and integration means 18. That is, TCf) is T(f) = f-sCf acf)E
(1) Here, S[*] indicates spectrum scrambling, and the signal * is scrambled to find S[*].

When T(f) in Equation 1 is PM modulated and emitted, and F'M demodulated at 22 in FIG. 11, which is an embodiment of the method of the present invention,
If the PM transmission path is ideal, demodulation power R(f crown, T(f
), i.e., f T(7). Therefore FtCf) = f T(f) = s[:fc(f))
(2) In the method of the present invention, after FM demodulation, the signal is immediately descrambled, integrated at 24, and output. If the power of the output signal is OCf, it is given as follows.

0(f)=f″″s (R(f))
(3) Here, S-1 (*:] represents the spectrum descrambling function, and satisfies the following relationship.

s-"s(*)=5s-1(*)=*Substituting equation 2 into equation 3, we get 0(f)=f-28-1[S[f2G(f)1=f"''
s sCf a(f))=c(f) (4
), it can be seen that if the PM transmission path satisfies the noise-free and distortion-free conditions, the transmitted input signal GCf) can be correctly reproduced on the receiving side. Therefore, it becomes clear that the present invention has a fourth advantage.

(Effects of the Invention) As described above, according to the present invention, a PM reception system having a simple configuration and having noise characteristics that are not affected by spectrum scrambling can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of the present invention, FIG. 2 is a diagram schematically showing the spectrum of each part of a conventional reception system, and FIG. 3 is a diagram showing an example of a transmission system. Figure 4 is a diagram schematically representing the spectrum of each part of the transmission system, Figure 5 is a diagram showing the long-term average spectrum of fading noise power mixed in during PM demodulation, and Figure 6 is a diagram showing the spectrum of fading noise mixed in during PM demodulation. FIG. 7 is a block diagram showing another example of a conventional reception method; FIG. 8 is a block diagram showing another example of a conventional transmission method; Figure 9 is a diagram schematically representing the spectrum of each part of the reception system, Figure 10 is a diagram schematically representing the spectrum of each part of the transmission system, Figure 11 is a block diagram showing the conventional reception system, and Figure 12 is a diagram schematically representing the spectrum of each part of the reception system. 13 is a block diagram showing the detailed configuration of the PM demodulation means, and FIG. 14 is a diagram schematically showing the spectrum of each part of the embodiment of the present invention.
FIG. 15 is a block diagram showing the configuration of a confidential reception system using FM demodulation means, and FIG. 16 is an example of implementation of a spectral scrambler. FIG. 17 is a diagram schematically representing the spectrum of each part in FIG. 16. 1.9, 21, 30... receiving antenna, 2.10...
- PM demodulation section, 3, 12, 23... Spectrum descrambling section, 6, 17, 34... Spectrum scrambling section, 7.19... PM modulation (transmission) section, 8.
20... Transmitting antenna, 11, 16.33... Differentiating section, 13, 18, 24, 28, 32, 35... Integrating section, 22, 27, 31... FM demodulating section, 40...・Input terminal, 41.50~52...Mixer, 42,53~5
5...Local oscillator, 43.56-58...Low pass filter, 44-46...Switch, 47-49...
・Band/base filter, 59...X adder, 60...
・Output terminal.

Claims (1)

[Claims] A method for receiving a spectrum-scrambled and phase-modulated transmitted wave includes at least FM receiving means for frequency demodulating the received wave, means for spectrally descrambling the demodulated output signal of the FM receiving means, and a means for spectrally descrambling the demodulated output signal of the FM receiving means, and a method for receiving the descrambled output. A means for integrating is provided, and phase modulation (
PM) A spectrum scramble reception method characterized by receiving a spectrum scrambled signal on a wireless transmission path.