JPH0425342U

JPH0425342U -

Info

Publication number: JPH0425342U
Application number: JP6774990U
Authority: JP
Priority date: 1990-06-26
Filing date: 1990-06-26
Publication date: 1992-02-28

Description

[Brief explanation of the drawing]

第１図はこの考案の第１実施例の構成を示すブ
ロツク図、第２図イ〜ニは同実施例の各部の周波
数スペクトラムを示すグラフ、第３図はこの考案
の第２実施例の構成を示すブロツク図、第４図〜
第７図は同実施例の変形例の構成を示すブロツク
図、第８図はコードレス電話機の親機の構成を示
すブロツク図、第９図はコードレス電話機の子機
の構成を示すブロツク図、第１０図は従来の秘話
回路の構成を示すブロツク図、第１１図イ〜ニは
同秘話回路の各部の周波数スペクトラムを示すグ
ラフである。５０，５６……ＢＰＦ（第１のフイルタ）、５
１，５７……ＤＢＭ（第１の混合手段）、５２…
…発振器（第１の発振手段）、５３，５８……Ｄ
ＢＭ（第２の混合手段）、５４……発振器（第２
の発振手段）、５５，５９……ＬＰＦ（第２のフ
イルタ）、６０，６６……ＳＣＦ（第１のフイル
タ）、６５，６９……ＳＣＦ（第２のフイルタ）
。 Figure 1 is a block diagram showing the configuration of the first embodiment of this invention, Figure 2 A to D are graphs showing the frequency spectrum of each part of the same embodiment, and Figure 3 is the configuration of the second embodiment of this invention. Block diagram showing this, Figure 4~
FIG. 7 is a block diagram showing the configuration of a modified example of the same embodiment, FIG. 8 is a block diagram showing the configuration of the base unit of the cordless telephone, FIG. 9 is a block diagram showing the configuration of the slave unit of the cordless telephone, and FIG. FIG. 10 is a block diagram showing the configuration of a conventional secret speech circuit, and FIGS. 11A to 11D are graphs showing frequency spectra of various parts of the secret speech circuit. 50, 56...BPF (first filter), 5
1, 57...DBM (first mixing means), 52...
...Oscillator (first oscillation means), 53, 58...D
BM (second mixing means), 54...oscillator (second
oscillation means), 55, 59...LPF (second filter), 60, 66...SCF (first filter), 65, 69...SCF (second filter)
.

Claims

[Claims for Utility Model Registration] (1) A first filter that extracts frequency components below a predetermined frequency limit from an input signal, and outputs a first oscillation signal having a frequency that is at least twice the frequency limit. a first oscillation means; a first oscillation means that receives an input signal supplied through the first filter and the first oscillation signal and outputs a modulated wave having a lower sideband and an upper sideband; a second oscillation signal that outputs a second oscillation signal whose frequency differs from the first oscillation signal by the limit frequency;
oscillation means; and a second mixing means that inputs the modulated wave and the second oscillation signal, demodulates the lower sideband of the modulated wave to a band below the limit frequency, and outputs the demodulated signal. a second filter that extracts frequency components below the limit frequency from the output of the second mixing means and outputs a signal of the lower sideband whose frequency spectrum is inverted with respect to the input signal; A secret circuit for a cordless telephone characterized by the following. (2) At least one of the first and second filters is configured by a switched capacitor filter, and one of the first and second oscillation signals is used as a clock signal for the switched capacitor filter. 2. A secret circuit for a cordless telephone according to claim 1. (3) The first and second filters are configured by first and second switched capacitor filters, respectively, and one of the first and second oscillation signals is transmitted to the first switched capacitor filter. 2. The secret line circuit for a cordless telephone set according to claim 1, wherein one signal is used as a clock signal for a passive filter, and the other is used as a clock signal for said second switched capacitor filter.