Radio frequency transmission system

• US 4,312,072 A
• Filed: 12/31/1979
• Issued: 01/19/1982
• Est. Priority Date: 01/17/1979
• Status: Expired due to Term

• Current Assignee: Siemens AG
• Original Assignee: Siemens AG
• Inventors: Vogel, Klaus
• Primary Examiner(s): Safourek, Benedict V.
• Assistant Examiner(s): Chin, Stephen
• Application Number:
  US06/108,460
• Time in Patent Office: 750 Days
• Field of Search: 375/1, 375/2, 375/96, 375/45, 375/46, 375/80, 455/1, 455/29, 455/42, 455/313, 455/323, 455/18, 455/95, 455/167, 455/242, 329/102, 329/103, 329/104, 331/4, 331/19, 332/1, 332/9 R, 332/10, 340/348, 343/59 A, 343/121
• US Class Current: 380/34
• CPC Class Codes: H04B 14/002 characterised by the use of a carrier modulation using subcarrier modulation H04B14/08
• CPC Class Codes: H04K 1/003 by varying carrier frequency at or within predetermined or random intervals H04K1/04 takes precedence

Abstract

Radio transmission system in which the carrier frequency oscillator at the transmitter is wobbulated by varying its frequency in a periodic manner and modulated and transmitted to a receiving site where the detected signal is passed through two separate paths, one being supplied to a converter and the other is supplied to the converter through a delay line. The output of the converter comprises an intermediate frequency which contains the modulation which is then demodulated and detected. Modification of the invention provides for transmitting two or more separate intelligences on the carrier and detecting the two intelligences at the receiver.

Claims

1. A communications system for electromagnetic waves, consisting of a transmitter, in which the signal to be transmitted is modulated onto a carrier, a transmitting- and a receiving-antenna with a radio linkhop, dispensed therebetween and a receiver in which the received signal is converted into an IF-signal and demodulated, characterized by the following features:

the transmitting signal is modulated in the transmitter with an intelligence signal and is controlled in its frequency-time-progression periodically between an upper and a lower frequency boundary by means for signal controlling and processing with at least one carrier oscillator, in such a manner that the absolute value of the frequency difference of the transmitting signal, relative to the times t and t+τ

, is constant for all times t within the sweep time T, and there results at the receiving converter of the receiver, a constant intermediate frequency containing the modulation, by virtue of the fact that the amplified receiving signal is separated by two branches, with one branch connected with the one input of the receiving converter, and the other is connected through a delay line, with the other input of the receiving converter, the intermediate frequency of the receiving converter is subsequently supplied to a filter, an amplifier and a demodulator and subsequently the method-conditioned transit time distortion of the intelligence signal is corrected.

2. A radio transmission system according to claim 1, characterized in that the transmitted carrier signal which is modulated with the intelligence is controlled in frequency with a control unit connected to said oscillator to periodically vary its frequency between upper and lower frequency limits such that the frequency varies as a linear function of time over a fixed period.

3. A radio transmission system according to claim 2, characterized in that the transmitted power after each fixed period during which the receiver has maintained a constant intermediate frequency which contains the intelligence is switched off by the control unit for at least one carrier oscillator period for short times which is smaller than the wobble time or for the time τ

, which corresponds to the delay time of the delay line in the receiver.

4. A radio transmission system according to claim 1, characterized in that the transmitted carrier signal is produced by the signal addition of the outputs of two oscillators which are alternately switched in and controlled by a common wobble unit, and said two oscillators are controlled between upper and lower frequency limits such that the switch-in time of said two oscillators overlap for a time interval of τ

, which corresponds to the delay time of the delay line in the receiver, so that in the receiver an uninterrupted constant intermediate frequency occurs which carries the intelligence.

5. A radio transmission system according to claim 1, characterized in that the transmitted carrier signal which is modulated with the intelligence is controlled by the control unit between upper and lower frequency limits such that the transmitted frequency is always constant within a time period of τ

, which corresponds to the length of the time delay of the delay line in the receiver, said transmitter signal is switched very quickly in frequency between consecutive carrier periods, the frequency difference of the transmitted carrier frequency during two consecutive periods is always the same and corresponds to the intermediate frequency of the receiver, and frequency jumps of the carrier between "double" periods can be random or can be selected to follow a selected pattern as required to prevent interfering influences on the receiver due to external transmitters.

6. A radio transmission system according to claim 1, wherein the transmitted carrier signal in the transmitter is produced by a plurality of carrier oscillators, and their output signals combined in steps with mixers such as single side band converters, and filters and said oscillators are controllable separately in frequency and amplitude so that they can be steered independently in frequency and so that they can be modulated with different modulating intelligence, which is decoupled due to the individual carrier oscillator frequencies.

7. A radio transmission system according to claim 1, characterized in that in the receiver, a receiving filter receives the output of the receiving antenna, a wide band amplifier receives the output of said filter and amplifies the sum of the received signals and regulates and limits them to a level which is at such a height such that the receiving converter is not over-driven and so that cross modulation products will be as small as feasible.

8. A radio transmission system according to claim 7, characterized in that a filter is connected to the output of said receiving amplifier which eliminates interfering frequencies which arise due to non-linearity of the amplifier and also eliminates the interfering signals which arrive at the amplifier simultaneously with the intelligence signal.

9. A radio transmission system according to claim 7, characterized in that in the transmitter, the transmitted carrier signal which is modulated with the intelligence signal is controlled by the control unit for at least one carrier oscillator such that in the receiver, a constant intermediate frequency occurs, the amplified received signal is divided into two branches, one branch having a first delay line which is adapted to the transmitted carrier signal, said two branches are connected to first and second inputs of a first receiving converter, and the intermediate frequency of said converter is regulated, amplified and filtered and then is again divided into two branches with one branch having a second delay line which is adapted to the transmitted carrier signal, and these two branches are connected to a pair of inputs of a second converter which has a constant intermediate frequency output which carries the intelligence, and this intermediate frequency is filtered, amplified and demodulated to produce the intelligence.

10. A radio transmission system according to claim 1, characterized in that to the receiving antenna (A) or to receiving amplifier (EV), a controllable selection filter (F_E) is connected, which is controlled to follow the wobbled received signal with a synchronizing and control unit (S) in the receiver.

11. A radio transmission system according to claim 1, characterized in that the intelligence signal is modulated onto the transmitted carrier signal in the form of amplitude modulation or ASK modulation.

12. A radio transmission system according to claim 1, characterized in that the intelligence signal is modulated onto the transmitted carrier in the form of frequency modulation or FSK modulation.

13. A radio transmission system according to claim 1, characterized in that the intelligence signal is modulated onto the transmitted carrier signal with combination of AM and/or FM and/or ASK and/or FSK modulations.

14. A radio transmission system according to claim 1, characterized in that the intelligence signal which is to be transmitted is predistorted in the transmitter with a predistorter so that despite system conditioned transit time distortion in the receiver, the undistorted signal will appear at the output of the demodulator.

15. A radio transmission system according to claim 1, characterized in that the intelligence signal is transmitted in pulse code modulation form, a control unit for at least one carrier oscillator is controlled so that the transmitted carrier signal is controlled between upper and lower frequency limits such that the absolute value of the frequency difference Δ

f is a constant at the times t and t-τ

, for all times t within the wobble time τ

for a wobble time period T, and these constants represent the bit content of one bit which is to be transmitted and the wobble time T forms the bit length of the bits of the bit current which is to be transmitted.

16. A radio transmission system according to claim 1, characterized in that the bit length of the information which is to be transmitted, the transit time of the delay line of the receiver and the wobble period of the transmitter have a whole number relationship ratio to one another.