Radio transmitter/receiver for digital and analog communications system

• US 4,355,401 A
• Filed: 09/26/1980
• Issued: 10/19/1982
• Est. Priority Date: 09/28/1979
• Status: Expired due to Term

• Current Assignee: Nippon Electric Company Limited (NEC Corporation)
• Original Assignee: Nippon Electric Company Limited (NEC Corporation)
• Inventors: Akaiwa, Yoshihiko, Saegusa, Noboru, Takase, Ichirou, Ikoma, Masao
• Primary Examiner(s): Safourek, Benedict V.
• Application Number:
  US06/191,154
• Time in Patent Office: 753 Days
• Field of Search: 179/1.5 R, 179/1.5 E, 179/2 DP, 179/6 R, 179/3, 340/170, 340/171 R, 375/2.1, 375/2.2, 375/3, 375/4, 375/5, 375/46, 375/7, 375/8, 455/26, 455/31, 455/38, 455/7, 455/73, 455/78
• US Class Current: 375/216
• CPC Class Codes: H04L 27/0008 arrangements for allowing a transmitter or receiver to use more than one type of modulation negotiating modulation type for two-way transmission paths H04L5/1453
• CPC Class Codes: H04L 27/14 Demodulator circuits; Receiver circuits
• CPC Class Codes: H04L 27/2035 using a single or unspecified number of carriers
• CPC Class Codes: H04L 27/2275 wherein the carrier recovery circuit uses the received modulated signals

Abstract

According to the present invention, a radio apparatus has a section for receiving an analog signal and a digital angle-modulated carrier wave signal. The analog signal and digital angle-modulated carrier wave output of the receiver section are demodulated to provide first and second demodulated signals. A clock signal is regenerated from the output of either the demodulating means or receiver section. A control signal selectively operates a switch for passing either the first or the second demodulated signals. The regenerated clock signal controls the switch.

Claims

1. A method of securely encoding communication, the method comprising the steps of:

(a) converting an analog signal into a digitally encoded signal,

(b) selecting between said analog signal and digitally encoded signal for transmission in response to a control signal,

(c) angle modulating a carrier wave with the selected analog signal or digitally encoded signal,

(d) transmitting the angle modulated carrier wave,

(e) receiving and demodulating said angle modulated carrier wave to produce one of either the analog or the digitally encoded signals,

(f) regenerating a clock signal responsive to the received signal of step (e),

(g) generating said control signal responsive to said clock signal of step (f),

(h) decoding said encoded signal of step (e) to produce an analog signal,

(i) selecting said analog signals of either steps (e) or (h) in response to said control signal.

2. The process of claim 1 wherein said transmission of step (d) is in the 25 KHz band.

3. A radio device having secure transmission capabilities, said device comprising means for transmitting carrier waves which are angle modulated by either analog or digital signals;

first selecting means for selecting either the analog or digital angle modulated carrier waves in response to a control signal;

means for receiving both analog and digital angle modulated carrier waves and demodulating them to provide demodulated analog or digital signals, respectively;

means for regenerating a clock signal from the output of said receiving means;

analog-digital decision means responsive to said clock signals for generating said control signal, and second selecting means responsive to said control signal for selecting either said demodulated analog or digital signals.

5. The radio apparatus of claims 3 or 4, wherein said analog-digital decision means comprises an amplifier for amplifying said clock signal, a rectifying circuit for rectifying the output of said amplifier, and a voltage comparator for comparing the output voltage of said rectifying circuit with a reference voltage to provide said control signal.

4. A radio apparatus comprising:

receiver means for receiving both analog and digital angle-modulated carrier waves transmitted over a radio frequency;

means connected to the output of said receiver means for respectively demodulating said analog and digital angle-modulated carrier waves to provide first and second demodulated signals;

means for regenerating a clock signal from the output of said receiver means;

first switching means responsive to a control signal for selectively passing either said first or said second demodulated signals;

analog-digital decision means responsive to said clock signal for generating said control signal;

means for analog and digital modulating a signal to be transmitted to produce first and second modulated signals, respectively;

second switching means responsive to said control signal for selectively passing either said first or said second modulated signals; and

means for transmitting the output of said second switching means over a radio frequency.