A SWITCHED FREQUENCY COMMUNICATIONS SYSTEM WITH AUTOMATIC PHASE AND AMPLITUDE COMPENSATION

• US 3,838,342 A
• Filed: 12/22/1970
• Issued: 09/24/1974
• Est. Priority Date: 02/27/1967
• Status: Expired due to Term

• Current Assignee: Bengt Harry Bjorkman
• Original Assignee: Bengt Harry Bjorkman
• Inventors: Bjorkman, Bengt Harry
• Primary Examiner(s): Tubbesing, T. H.
• Assistant Examiner(s): Birmiel, H. A.
• Application Number:
  US05/100,684
• Time in Patent Office: 1,372 Days
• Field of Search: 325/42,45,47,62,65,347,473,476,32 179/1.5R,1.5FS
• US Class Current: 380/34
• CPC Class Codes: C07D 207/22 with hetero atoms or with carbon atoms having three bonds to hetero atoms with at the most one bond to halogen, e.g. ester or nitrile radicals, directly attached to ring carbon atoms

Abstract

A communications device consisting of a transmitter that produces a phase modulated signal that is switched to a plurality of different frequencies according to a preselected program, and a receiver that mixes the received signal with a sequence of frequencies equal to the transmitted frequencies plus or minus a fixed intermediate frequency. In order to compensate for the different phase shifts produced by the interaction of the different transmitted frequencies with various fixed obstructions the phase of the intermediate frequency in the receiver corresponding to each transmitted frequency is measured, compared with a fixed phase reference oscillator and stored. The stored phase information relating to each transmitted frequency is used to control a phase shifter in the receiver during subsequent transmissions of the corresponding frequency, thereby completing a phase correction control loop. A similar comparison, storage, and control feedback loop is used in conjunction with an AVC amplifier in order to individually control the amplitude of each received frequency.

Claims

1. A communications device, comprising a transmitter and a receiver, means in the transmitter for providing a coded carrier signal sequentially switched to at least two different frequencies under the control of a stored program, frequency synthesis means in the receiver for providing a sequence of frequencies corresponding to the carrier frequency sequence, each of the synthesized frequencies differing from the corresponding carrier frequency by an intermediate frequency, a mixer in the receiver connected to the frequency synthesis means and to the received coded carrier signal for forming an intermediate frequency signal from the received signal, a reference oscillator providing an output signal with a fixed phase, a phase shifter in the receiver connected to the received signal and having a control input for adjusting the phase of the received signal, phase detector means in the receiver and connected to the phase shifter and the reference oscillator for providing an output equal to the phase difference between the reference oscillator and the phase shifter output corresponding to each received frequency of the coded carrier signal, a memory connected to the phase detector means for sequentially storing the phase difference corresponding to each received frequency of the coded carrier signal, a feedback loop connected between the output of the memory and the control input of the phase shifter for adjusting the phase of the received coded carrier signal toward the phase of the reference oscillator, and means connecting the frequency synthesis device to the memory for interrogating the memory in the same sequence as the frequency sequence of the received coded carrier signal whereby the stored phase difference of each received frequency is used to adjust the phase of a subsequently received identical frequency.

2. A device as claimed in claim 1, wherein the intermediate frequency is a fixed frequency, wherein the phase shifter is connected to the output side of the mixer, wherein the reference oscillator provides a signal having a fixed frequency equal to the intermediate frequency, and wherein the memory further comprises means for adding the phase difference from the phase detector for each new frequency to the value previously stored for that corresponding frequency.

3. A device as claimed in claim 2, wherein the memory comprises a shift register matrix consisting of a number of columns of memory elements, each column storing phase information corresponding to a different frequency, the frequency synthesis device providing shifting signals for the register, the feedback loop connecting the last column of the shift register to the control input of the phase shifter, and means for adding the value of the last column to the output of the phase detector before storing the sum in the first column of the register.

4. A device as claimed in claim 1, wherein the receiver further comprises an AVC-amplifier connected to the received coded carrier signals and having a control input for adjusting the level of the received coded carrier signals, a reference voltage source, means for generating an amplitude difference signal corresponding to each received frequency of the coded carrier signals and equal to the difference between the amplitude of each received frequency of the coded carrier signals and the amplitude of the refErence voltage source, means for storing each amplitude difference frequency, and a feedback loop connecting the output of the storage means to the control input of the AVC-amplifier for adjusting the amplitude of each received frequency of the coded carrier signal with the stored amplitude difference of the corresponding previously received frequency.