JPH04347947A - Frequency inverting communication system - Google Patents
Frequency inverting communication systemInfo
- Publication number
- JPH04347947A JPH04347947A JP14978991A JP14978991A JPH04347947A JP H04347947 A JPH04347947 A JP H04347947A JP 14978991 A JP14978991 A JP 14978991A JP 14978991 A JP14978991 A JP 14978991A JP H04347947 A JPH04347947 A JP H04347947A
- Authority
- JP
- Japan
- Prior art keywords
- frequency
- amplitude
- circuit
- signal
- inversion
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
- 238000000034 method Methods 0.000 claims description 8
- 230000003247 decreasing effect Effects 0.000 claims description 7
- 230000000694 effects Effects 0.000 abstract description 4
- 230000005236 sound signal Effects 0.000 abstract description 4
- 238000006243 chemical reaction Methods 0.000 abstract description 3
- 230000005540 biological transmission Effects 0.000 abstract description 2
- 238000010079 rubber tapping Methods 0.000 abstract 3
- 238000010586 diagram Methods 0.000 description 4
- 238000001228 spectrum Methods 0.000 description 4
- 230000010355 oscillation Effects 0.000 description 2
Abstract
Description
【0001】0001
【産業上の利用分野】本発明は,通信方式に関するもの
であり,特に,たとえば,コードレス電話機の親機と子
機との間の無線通信において盗聴防止用に周波数を反転
させた通信を行う周波数反転通信方式に関する。[Industrial Application Field] The present invention relates to a communication system, and in particular, for example, a frequency inverted frequency communication method for wireless communication between a base unit and a slave unit of a cordless telephone to prevent eavesdropping. Concerning reverse communication method.
【0002】0002
【従来の技術】コードレス電話機において,親機と子機
との間が無線通信されるが,この無線通信空間における
漏話または盗聴が問題になっている。そのような盗聴を
防止する方法として,たとえば,子機から親機に送信す
る信号の周波数スペクトルが図3(A)に示す特性の場
合,子機において一旦中心周波数fM/2を中心として
周波数を反転させて,図3(B)に示す周波数スペクト
ルにして親機に送出している。親機から子機に信号を送
信する場合も同様である。2. Description of the Related Art In cordless telephones, wireless communication is carried out between a base unit and a slave unit, but crosstalk or eavesdropping in this wireless communication space has become a problem. As a method to prevent such eavesdropping, for example, if the frequency spectrum of the signal transmitted from the slave unit to the base unit has the characteristics shown in Figure 3 (A), the slave unit temporarily changes the frequency around the center frequency fM/2. The frequency spectrum is inverted and transmitted to the base unit as shown in FIG. 3(B). The same applies when transmitting a signal from the base unit to the slave unit.
【0003】0003
【発明が解決しようとする課題】上述の周波数反転暗号
化によっても中心周波数近傍では信号振幅(スペクトル
)は変化しない。したがって,中心周波数近傍の音声信
号が子機から親機またはその逆に送信された場合,その
ような周波数帯域の信号については周波数反転暗号化の
効果がなく,盗聴などが容易に行われるという問題があ
る。したがって,本発明はコードレス電話機の子機など
に容易に実現可能な簡単な回路構成で上記問題を解決す
ることを目的とする。Problem to be Solved by the Invention Even with the frequency reversal encryption described above, the signal amplitude (spectrum) does not change in the vicinity of the center frequency. Therefore, if an audio signal near the center frequency is transmitted from the handset to the base unit or vice versa, frequency reversal encryption has no effect on signals in such frequency bands, and eavesdropping can easily occur. There is. Therefore, it is an object of the present invention to solve the above-mentioned problems with a simple circuit configuration that can be easily implemented in a handset of a cordless telephone.
【0004】0004
【課題を解決するための手段】上記問題を解決するため
,本発明の送信信号の周波数成分を反転させて送信し,
受信信号の周波数成分を反転させて再生する周波数反転
通信方式においては,送信側に上記周波数反転した送信
信号の中心周波数近傍の振幅を上昇または低下させる手
段を有し,受信側に上記受信信号について上記中心周波
数近傍の振幅を上記上昇または低下させた分に相当する
量を低下または上昇させる手段を有する。[Means for Solving the Problems] In order to solve the above problems, the frequency components of the transmission signal of the present invention are inverted and transmitted.
In a frequency inversion communication system that inverts and reproduces the frequency components of a received signal, the transmitting side has means for increasing or decreasing the amplitude near the center frequency of the frequency-inverted transmitted signal, and the receiving side has a means for increasing or decreasing the amplitude of the frequency-inverted transmitted signal, and the receiving side has a means for increasing or decreasing the amplitude of the frequency-inverted transmitted signal. It has means for decreasing or increasing the amplitude in the vicinity of the center frequency by an amount corresponding to the above-described increase or decrease.
【0005】[0005]
【作用】送信側では送信信号の周波数反転して暗号化す
る他,この暗号化では変化しない中心周波数近傍の振幅
を変化させる。この振幅を変化させる方法としては振幅
を上昇させるか,または,低下させる。受信側では受信
信号の周波数を反転して復号化する他,上記送信側にお
ける中心周波数近傍の変化の逆操作を行う。すなわち,
送信側で振幅を大きくしている場合は振幅を低下させる
。この振幅変化方式は事前に送信装置と受信装置との間
で規定されている。振幅を低下させると盗聴されても聞
きにくくなるので,送信側では振幅を低下させることが
望ましい。受信側では,振幅を低下させた分に相当する
量を振幅上昇させてもとの振幅を復元させる。[Operation] On the transmitting side, in addition to inverting the frequency of the transmitted signal and encrypting it, it also changes the amplitude near the center frequency, which does not change with this encryption. The method of changing this amplitude is to increase or decrease the amplitude. On the receiving side, in addition to inverting the frequency of the received signal and decoding it, the inverse operation of the change in the vicinity of the center frequency on the transmitting side is performed. That is,
If the amplitude is increased on the transmitting side, the amplitude is decreased. This amplitude change method is defined in advance between the transmitting device and the receiving device. Lowering the amplitude makes it harder to hear even if eavesdropping occurs, so it is desirable to lower the amplitude on the transmitting side. On the receiving side, the amplitude is increased by an amount corresponding to the amplitude reduction to restore the original amplitude.
【0006】[0006]
【実施例】本発明の周波数反転暗号化通信方式の1実施
例として,図1に,コードレス電話機の子機に設けられ
た送信回路の一部と受信回路の一部のブロック図を図1
に示す。親機にもこの子機と同様の送信回路と受信回路
が設けられる。このコードレス電話機の子機において,
キャリア発振周波数fM の局部発振器(LCO)5を
挟んで,上部の回路が送信回路の一部,下部の回路が受
信回路の一部になる。[Embodiment] As an embodiment of the frequency inversion encrypted communication system of the present invention, FIG. 1 shows a block diagram of a part of a transmitting circuit and a part of a receiving circuit provided in a cordless telephone handset.
Shown below. The base unit is also provided with a transmitting circuit and a receiving circuit similar to that of the slave unit. In the handset of this cordless telephone,
With a local oscillator (LCO) 5 having a carrier oscillation frequency fM in between, the upper circuit becomes part of the transmitting circuit, and the lower circuit becomes part of the receiving circuit.
【0007】送信回路は,ローパスフィルタ(LPF)
1,直交変調器2,LPF3,振幅低下回路4を有して
いる。音声信号INA がLPF1に入力され,LOC
5のキャリア周波数よりも高い周波数成分が除去される
。
直交変調器2にはLCO5からのキャリア発振周波数f
M の周波数信号が印加され,キャリア周波数を中心と
した搬送波抑圧両側波帯の信号に周波数変換が行われる
。
この周波数変換信号がLPF3に入力され,下側波帯成
分のみを通過させ上側波帯成分を除去させる。これによ
り,図3(A)に示したように,入力音声周波数成分と
反転した周波数成分(スペクトル)を持つ信号が得られ
る。振幅低下回路4はこの周波数反転された信号成分の
中心周波数fM /2を中心として周波数的にある一定
の幅だけその振幅を低下させる。振幅低下回路4,具体
的には,周波数fM /2で所定量振幅を低下させるノ
ッチフィルタが設けられており,図2(A)の記号Aで
示した位置の周波数fM /2を中心とするその近傍に
おいて周波数反転されこの信号の振幅を低下させる。[0007] The transmitting circuit is a low-pass filter (LPF).
1, a quadrature modulator 2, an LPF 3, and an amplitude reduction circuit 4. Audio signal INA is input to LPF1, and LOC
Frequency components higher than the carrier frequency of 5 are removed. The quadrature modulator 2 receives the carrier oscillation frequency f from the LCO 5.
A frequency signal of M is applied, and frequency conversion is performed to a carrier-suppressed double-side band signal centered on the carrier frequency. This frequency-converted signal is input to the LPF 3, which passes only the lower sideband component and removes the upper sideband component. As a result, as shown in FIG. 3A, a signal having a frequency component (spectrum) that is inverted from the input audio frequency component is obtained. The amplitude lowering circuit 4 lowers the amplitude of the frequency-inverted signal component by a certain width around the center frequency fM/2. The amplitude reduction circuit 4, specifically, is provided with a notch filter that reduces the amplitude by a predetermined amount at a frequency fM/2, and is centered at the frequency fM/2 at the position indicated by symbol A in FIG. 2(A). In its vicinity, the frequency is inverted, reducing the amplitude of this signal.
【0008】受信回路は,振幅上昇回路6,LPF7,
直交変調器8,LPF9を有している。受信回路内のL
PF7,直交変調器8,LOC5,LPF9によって,
上記同様,図3(B)に示した周波数逆変換復号化処理
が行われる。この周波数逆変換に先立って,振幅上昇回
路6によって上記振幅低下回路4で振幅を低下させたと
同等の量だけ受信信号の振幅を上昇させる。図示しない
親機内の送信回路からは図1に示した送信回路における
と同様に周波数fM /2を中心とするその近傍で振幅
を低下させて図1に示す子機内の受信回路に送信してい
るから,受信回路の振幅上昇回路6において振幅を上昇
させることにより,LPF7には本来の振幅に復元され
た信号が出力される。このように子機内の送信側で中心
周波数近傍で所定量だけ振幅を低下させて親機内の受信
回路に周波数反転かつ振幅低下させた信号を送信するか
ら,子機と親機との間でかりに盗聴があっても聞きにく
い。親機内の受信回路(図示せず,ただし,子機の受信
回路と同等)で上記子機の送信回路で振幅低下量に相当
する量を振幅上昇させているので,コードレス電話機全
体として振幅低下または上昇は生じない。そして,音声
信号について周波数反転され暗号化されていることを考
慮すると盗聴に対して充分な効果を示す。[0008] The receiving circuit includes an amplitude increase circuit 6, an LPF 7,
It has a quadrature modulator 8 and an LPF 9. L in the receiving circuit
By PF7, quadrature modulator 8, LOC5, LPF9,
Similarly to the above, the frequency inverse transform decoding process shown in FIG. 3(B) is performed. Prior to this frequency inversion, the amplitude increase circuit 6 increases the amplitude of the received signal by the same amount as the amplitude decrease by the amplitude decrease circuit 4. Similar to the transmitting circuit shown in Fig. 1, the transmitting circuit in the main unit (not shown) lowers the amplitude around the frequency fM/2 and transmits to the receiving circuit in the slave unit shown in Fig. 1. By increasing the amplitude in the amplitude increasing circuit 6 of the receiving circuit, a signal restored to its original amplitude is output to the LPF 7. In this way, the transmitting side of the handset lowers the amplitude by a predetermined amount near the center frequency, and transmits the frequency-inverted and amplitude-reduced signal to the receiver circuit of the base unit. Even if there is eavesdropping, it is difficult to hear. The receiving circuit in the base unit (not shown, but equivalent to the receiving circuit in the handset) increases the amplitude by an amount equivalent to the amount of amplitude decrease in the transmitting circuit of the handset, so the overall cordless phone has a decrease in amplitude. No rise occurs. Considering that the audio signal is frequency inverted and encrypted, it is sufficiently effective against eavesdropping.
【0009】中心周波数帯域振幅低下回路4は上述した
ノッチフィルタに限らず,ノッチフィルタと同等の機能
を有する回路を用いることができる。また振幅上昇回路
6は中心周波数帯域振幅低下回路4の逆に振幅を上昇さ
せる回路であればどのような回路構成をとってもよい。
さらに上述した実施例では送信回路で振幅を低下させ,
受信回路で振幅を上昇させる場合について述べたが,そ
の逆にすることもできる。この場合,送信側においては
,盗聴にたいして充分大きすぎる程振幅を上昇させて聞
くに耐えないようにする。The center frequency band amplitude reduction circuit 4 is not limited to the above-mentioned notch filter, but a circuit having the same function as a notch filter can be used. Further, the amplitude increasing circuit 6 may have any circuit configuration as long as it increases the amplitude inversely to the center frequency band amplitude decreasing circuit 4. Furthermore, in the embodiment described above, the amplitude is reduced in the transmitting circuit,
Although the case where the receiving circuit increases the amplitude has been described, the reverse can also be done. In this case, on the transmitting side, the amplitude is increased to a level that is sufficiently large to prevent eavesdropping, thereby making it unbearable to listen to.
【0010】上記実施例はコードレス電話機に関連づけ
て述べたが,本発明の実施に際しては,コードレス電話
機に限らず,周波数反転して暗号化,およびその逆変換
をして復号化する通信方式に広く適用できる。Although the above embodiment has been described in connection with a cordless telephone, the present invention is applicable not only to cordless telephones but also to a wide range of communication systems that perform encryption by frequency inversion and decryption by inverse conversion. Applicable.
【0011】[0011]
【発明の効果】以上に述べたように,本発明によれば,
簡単な回路構成で盗聴,漏話に対して充分効果を示す周
波数反転暗号化通信方式が提供できる。[Effect of the invention] As described above, according to the present invention,
A frequency reversal encrypted communication system that is sufficiently effective against eavesdropping and crosstalk can be provided with a simple circuit configuration.
【図1】本発明の周波数反転暗号化通信方式の1実施例
のコードレス電話機の送信回路と受信回路を示す図であ
る。FIG. 1 is a diagram showing a transmitting circuit and a receiving circuit of a cordless telephone according to an embodiment of the frequency inversion encrypted communication system of the present invention.
【図2】図1のコードレス電話機における周波数反転暗
号化および周波数反転復号化を示す信号波形図である。FIG. 2 is a signal waveform diagram showing frequency reversal encryption and frequency reversal decoding in the cordless telephone of FIG. 1;
【図3】従来の周波数反転暗号化および周波数反転復号
化を示す信号波形図である。FIG. 3 is a signal waveform diagram showing conventional frequency reversal encryption and frequency reversal decoding.
1,3,7,9・・ローパスフィルタ 2,8・・直交変調器 4・・振幅低下回路 5・・局発振器 6・・振幅上昇回路 1, 3, 7, 9...Low pass filter 2, 8... Quadrature modulator 4. Amplitude reduction circuit 5...Local oscillator 6. Amplitude increase circuit
Claims (1)
信し,受信信号の周波数成分を反転させて再生する周波
数反転通信方式において,送信側に上記周波数反転した
送信信号の中心周波数近傍の振幅を上昇または低下させ
る手段を有し,受信側に上記受信信号について上記中心
周波数近傍の振幅を上記上昇または低下させた分に相当
する量の振幅を低下または上昇させる手段を有すること
を特徴とする周波数反転通信方式。Claim 1: In a frequency inversion communication method in which the frequency components of a transmitted signal are inverted before being transmitted, and the frequency components of a received signal are inverted and reproduced, the amplitude near the center frequency of the frequency-inverted transmitted signal is transmitted to the transmitting side. A frequency characterized in that the receiving side has means for increasing or decreasing the amplitude of the received signal by an amount corresponding to the increase or decrease in the amplitude near the center frequency of the received signal. Reverse communication method.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP14978991A JPH04347947A (en) | 1991-05-24 | 1991-05-24 | Frequency inverting communication system |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP14978991A JPH04347947A (en) | 1991-05-24 | 1991-05-24 | Frequency inverting communication system |
Publications (1)
Publication Number | Publication Date |
---|---|
JPH04347947A true JPH04347947A (en) | 1992-12-03 |
Family
ID=15482753
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
JP14978991A Pending JPH04347947A (en) | 1991-05-24 | 1991-05-24 | Frequency inverting communication system |
Country Status (1)
Country | Link |
---|---|
JP (1) | JPH04347947A (en) |
-
1991
- 1991-05-24 JP JP14978991A patent/JPH04347947A/en active Pending
Similar Documents
Publication | Publication Date | Title |
---|---|---|
JP2001505017A (en) | Mixed analog / digital broadcasting method of audio by single transmitting apparatus and apparatus therefor | |
US5553317A (en) | Quadrature modulator for TDMA/TDD radio communication apparatus | |
CA1204188A (en) | Privacy signal transmission system | |
JPH04347947A (en) | Frequency inverting communication system | |
JP2637624B2 (en) | Transmission / reception control circuit of cordless telephone | |
JPH0242259B2 (en) | ||
JP5350351B2 (en) | COMMUNICATION SYSTEM, TRANSMISSION DEVICE, RECEPTION DEVICE, AND COMMUNICATION METHOD | |
JP2674726B2 (en) | Spread spectrum communication equipment | |
JP2001308828A (en) | Method and device for arranging confidentiality in radio equipment | |
JPH08274753A (en) | Secret talk method, and transmitter and receiver | |
JPH022337B2 (en) | ||
JPS6377233A (en) | Voice communication system | |
US1654080A (en) | Carrier signaling system | |
JP2525409Y2 (en) | Wireless telephone equipment | |
JPH0147061B2 (en) | ||
JPH0564494B2 (en) | ||
JPH02272932A (en) | Privacy facsimile equipment | |
JPS63114330A (en) | Privacy communication equipment | |
JP2001007731A (en) | Spread spectrum transmitter and receiver thereof | |
JPS5950628A (en) | Frequency diversity system | |
JPH0347025B2 (en) | ||
JPH0147062B2 (en) | ||
JPS60174542A (en) | Secret communication system | |
JPS5862948A (en) | Signal encryption processing system | |
JPH02250444A (en) | Privacy call equipment |