DE2061744A1 - Device for transmitting information when the frequency changes - Google Patents

Description

". . 7..PHN. ^ 769 »I) *. BUtWt SCHOI * ■

Aft »No. PHN-4769
dated December 14, 1970

Device for the transmission of information with changing Frequency.

The result relates to a device in a system consisting of a transmitter and a receiver for the transmission of information with the aid of a high-frequency carrier wave * in which device a periodically operating control element installed in the transmitter ensures that the Frequency of the carrier wave gradually between different iierteii flat eiiiem determined beforehand! Pattern changes, with the Receiver eilie mixing stage contains, in which an incoming Carrier wave with a frequency is joined together with iiiiiö elilös similar control element awake the same pattern how the frequency of the transferring carrier wave is changed. This means that there is a mix of signals with a low bandwidth

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Received in the receiver, despite the fact that the frequency of the transmitted carrier wave changes in a wide frequency range. The changing frequency of the transmitted carrier wave will cause difficulties for an incompetent person in interpreting the information, because this person, if he does not know the frequency code, has to scan the entire frequency band. If other signals also occur within the actual frequency range, the difficulties in interpreting the transmitted information are increased because it is then difficult to determine which frequencies do and which do not belong together.

If the transmission can take place with a sufficiently low power, it is also possible before a to keep the incompetent person secret, that the transfer is taking place, whereby messages can even be transmitted if one has asked for radio silence. Therefore, your own recipient must have an extremely low bandwidth, while the amount of information that can be transmitted per unit of time will of course be relatively low.

In the case of shortwave transmission, the signal received by the receiver generally consists of two or more components, e.g. a fundamental wave and an atmospheric wave or several at different points of impact in the area reflected fundamental waves. Those components of the received signal j originating from reflected waves, are frequency dependent due to the fact that they are on different points are reflected and thus in dependencies

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have different migration distances depending on the frequency. The received signal in the receiver is therefore in step with the Frequency change modulated in phase and, as a result, also modulated in amplitude. As a result, the incoming carrier wave will have sidebands that are part of the transmitted Performance included. In an extremely narrow bandwidth receiver, performance in these sidebands is lost. The recipient can also be given a larger bandwidth, but this brings with it an increase in the noise received ^ which means that the transmitted power must be increased.

According to the invention, these disadvantages are eliminated and a receiver with an extremely low bandwidth can be used without loss of information. The invention is based on the knowledge that the atmospheric conditions of the environment are assumed to be relatively stable during a transmission period and will hardly change from the time when a certain frequency appears until the time when the same frequency reappears. M.

The invention is characterized in that the receiver further contains a phase rotator which is connected to the mixer and is arranged at the output of the mixer or in one of its feed lines, while further means for detecting the phase position of the incoming carrier wave with respect to the phase of a Locally generated wave and a storage device are provided, which storage device contains a number of storage layers corresponding to the number of frequencies and in time with the frequency change

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is actuated, which memory device is connected to the output of said phase detection means in which Storage positions for each new frequency information about the phase position of the actual frequency with respect to the reference phase is stored , wherein the storage device controls the phase rotator in such a way that this phase rotator for each new frequency in a position which corresponds to a value stored in the memory device, which the detected phase position during previous intervals representing the same frequency is offset so that the phase position of the after passing through the Mixer stage and the phase rotator received signal is kept almost constant.

As a result of the fact that the phase rotator for

each new frequency is set to a new value that corresponds to the measured phase position of the incoming carrier wave corresponds to previous intervals of the same frequency, the phase changes are almost completely compensated. The remaining Phase steps in the signal at the output of the phase shifter are then only affected by changes in the environment or in the Atmosphere during the intervals between transmissions of the same Frequency dependent.

In one embodiment of the device according to In the invention, the added frequency in the receiver is a fixed distance from the frequency of the incoming carrier wave, so that a constant intermediate frequency is obtained at the output of the mixer, the phase rotator at the output of the Mixing stage is attached so that it is at the constant

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Intermediate frequency works. The phase position of the incoming carrier wave is then detected with the help of a phase detector, which is connected downstream of the phase rotator and on the one hand with the output signal of the phase rotator and on the other hand with a phase stable intermediate frequency signal is fed. That The output signal of the phase detector then represents the change in represents the phase position that has taken place since the previous interval in which the actual frequency was transmitted, with the storage device is set in such a way that the output variable of the phase detector becomes a previously stored one Value with respect to the same frequency is added.

Some embodiments of the invention are shown in FIGS Drawings shown and are described in more detail below. Show it:

Fig. 1 is a block diagram of a transmitter for transmission a carrier wave of gradually changing frequency;

Fig. 2 is a block diagram of a receiver with ^

Phase compensation according to the invention for receiving the carrier wave transmitted by the transmitter according to FIG. 1, and

3 shows an arrangement which can be connected to the receiver according to FIG. 2 and with the aid of which changes can also be made can be compensated in amplitude.

In Fig. 1, 1 denotes an oscillator which supplies a fixed frequency of, for example, 1OMHz. The oscillator has two outputs that emit voltages that are 180 ° out of phase with one another. With the help of a working

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and normally closed contact 2, one of the outputs is connected to a mixer 3 in each case. At this stage the oscillator voltage is combined with the output voltage of a frequency synthesizer k , which frequency synthesizer may be of the type described in Swedish patent specification 223.13 ^. The frequency synthesis device is fed by a very stable oscillator 5. The pattern for the frequency change is determined by a frequency selection programming device 6, while the shift to a new frequency of pulses of a shift oscillator 7 is initiated.

It is assumed that the frequency of the output voltage supplied by the frequency synthesis device changes, for example, according to the previously determined pattern between the limit values 10 and 20 MHz. A mixed product then appears at the output of mixer 3, the frequency of which changes gradually within the frequency range from 30 to kO MHz. This mixed product is filtered in a bandpass filter 8, amplified in an amplifier 9 and transmitted via an antenna 10.

The phase of the transmitted carrier wave can be used for

each frequency can take one of two values, 0 ° and 180 ° could be. The phase is determined by the location of the work and Normally closed contact 2 is determined, which is controlled by a relay winding 11 will. This winding is in turn controlled by a pushbutton contact 12. Assume that the transmitted Information is in binary form; one of the binary values

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is determined by a phase position of the transmitted carrier wave and the second binary value, represented by the opposite phase position of this carrier wave. The push button contact 12 determines which value is transferred. The sampling frequency is assumed to be very low, e.g. 1-2 Hz, which means that the per time unit amount of information transmitted is small.

The frequency shift can take place with a shift frequency of 100 Hz and the shift pulses can e.g. be taken from a stage of the frequency synthesis device. "

FIG. 2 shows a receiver for receiving the changing carrier wave which is transmitted by a transmitter according to FIG. 1. The carrier wave is received by an antenna 21 and amplified in an amplifier 22 which contains a bandpass filter with a large bandwidth. The amplified carrier wave is fed to a mixer 23, in which it is combined with the output voltage of a frequency synthesis device 24. This device is fed by a control oscillator 25 and controlled by a frequency selection programming device Λ 26, which is shifted to a new frequency with the aid of pulses from a shift pulse oscillator 27. The frequency synthesis device 2k is designed in the same way as the transmitter-side frequency synthesis device k , while the programming device 26 is set in such a way that for the frequency change the same pattern is obtained as in the transmitter-side programming device 6, but with the frequency supplied by the receiving-side frequency synthesis device a constant value of the corresponding frequency synthesis device on the transmitter side

end-side Fi

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delivered frequency deviates. It is believed that the
Synchronization of the frequency synthesis devices of the transmitter and the receiver in any suitable manner, e.g.
The beginning of the transmission * takes place, after which this synchronization is maintained by the high frequency stability of the control oscillators 5 and 25. In this way, on
Output of the mixer 23 received a constant intermediate frequency, which is equal to the aforementioned fixed difference between
is the frequencies supplied by the frequency synthesis devices and is, for example, 1 MHz.

As a result of the fact that the received carrier wave consists of several waves, e.g. a fundamental wave and a
atmospheric wave, is built up and the latter wave itself
changes with the frequency as a result of different traveling distances, phase jumps will occur at the output of the mixer stage 23 in step with the frequency change. According to the invention, these phase jumps are compensated for by a phase rotator 28, which is connected downstream of the mixer 23 and which is controlled in a manner to be described in more detail below in such a way that most of the phase jumps mentioned are compensated. After passing through the phase rotator 28, an intermediate frequency signal appears in which both the frequency jumps in the incoming carrier wave and most of the phase jumps have been eliminated. The signal obtained from the phase rotator is passed through a bandpass filter 29 with a very small bandwidth and then through an amplitude limiter 30.

The filtered and limited intermediate frequency signal,

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which is then obtained is fed to a phase detector or a second mixer 31, in which (in which) it is compared with a phase-stable reference signal of the actual intermediate frequency, which is taken from an oscillator J2. In practice, the reference signal is taken from suitable stages of the frequency synthesis device 2k. At the output of the phase detector 31, a voltage occurs which represents the phase difference between the two applied voltages. After filtering in a filter 33 'in which any remaining high-frequency ripple voltage is suppressed, the output voltage of the phase detector is fed to a converter 3k in which the voltage is converted into digital form. The numerical variable that appears at the output of the converter 3k and represents the output voltage of the phase detector 31 is then fed to a first register R in a shift register matrix 36 via an adder 35. This matrix contains a number of individual registers R ₁ - ύ R corresponding to the number of frequencies in the frequency shifting pattern. The matrix is controlled by the oscillator 27 in time with the frequency change in such a way that for each frequency change the information in the drawing is shifted one step to the right} For example, the numerical information in register R is written into register R at the point in time at which the number contained in the register R "is written into R", etc. The number stored in the last register R of the matrix is used as a second input signal to the adding device 35. _{In this case, R 1} is entered in the first register for each frequency change

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a number is written which corresponds to the number which was stored in the last register R in the previous interval, plus the number received from the converter 3k . It is evident that because the matrix contains a number of registers corresponding to the number of frequencies, the two numbers combined in the device 35 always relate to the same frequency.

The aforementioned phase rotator 28, which is in the intermediate frequency part is arranged is controlled by the number stored in the last register R in each time interval. Included a closed circle is formed. The phase rotator 28 can advantageously be operated linearly, so that for each Frequency induces a phase shift that is proportional to the stored number. The phase rotator is thereby set gradually in time with the frequency change depending on the numbers appearing successively in the last register R. For each frequency, this number is the same as the number at the end of the previous interval when the actual frequency occurred was enrolled. In this way the adjustment of the phase rotator for each frequency is made by the output voltage determined at the output of the phase detector during a number of previous intervals with the actual transmission frequency occured. Provided that this If the frequency reaches the receiver in the same phase position from time to time, this is the output voltage of the phase detector the same after a number of complete work cycles zero, being the phase shift in the incoming carrier wave

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are completely balanced, so that after passing through the phase rotator a signal is obtained whose frequency is constant and its phase position remains unchanged.

During the switch-on state and when changes are made In the phase position of the incoming carrier wave, an error voltage occurs at the output of the phase detector that is continuous is regulated down to zero by negative feedback in the closed control loop. If the changes are slow enough and e.g. caused by shrinkage, the circle ™

follow the changes and the error voltage becomes almost the same held zero. On the other hand, rapid changes in the phase position of the incoming carrier wave run through the circle and lead a gradual increase in the error voltage at the output of the Phase detector. Only after a number of complete work cycles is the fault voltage regulated down to zero again, provided that the phase after the rapid change is constant or changes only slowly.

The adder 35 is advantageous in such Removing Λ formed that they are for measured phase error that is greater than Tt / 2, provides a number which corresponds to the complementary angle of the measured phase error, that is, that the device is formed as a modulo-Tt-adder is. As a result, if the phase error is γ , where lf is less than tc / 2, and the phase of the transmitted carrier wave is suddenly reversed, so that the real phase deviation of the incoming signal is Tt + if immediately after the phase reversal, the device 35 still left a number

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f ert, which corresponds to the angle I ^. In this case, the device "} h must contain complete information about the measured phase deviation and supply numbers which correspond to angles between 0 and 2 -tr Cosine supplies for the measured phase deviation, whereby the phase angle is fully determined.

The useful information is advantageously taken from the output of limiter 30 at an intermediate frequency level. For this purpose, this limiter can be connected to an evaluation device 37 which contains a discriminator, which is adapted to the type of modulation concerned. A further filtering process can also be carried out in the evaluation device 37 be performed.

In the present case, in which the information with

With the help of a simple type of modulation, in which the carrier wave is transmitted in one of two alternative phase positions J) , the information can also be taken from the output of the phase detector 31 or optionally the output of the converter "} h , with each phase reversal of the transmitted carrier wave In this case, the entire intermediate frequency part can be omitted if it is ensured that the receiving-side frequency synthesis device 2 ^ 4 delivers exactly the same frequencies as the transmitter-side frequency synthesis device, whereby a DC voltage is already applied during the first mixing is obtained that corresponds to the measured phase difference

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chung corresponds. The phase rotator, with the help of which the Phase jumps in the incoming carrier wave can then be compensated for in one of the feed lines of the mixing stage, are preferably arranged in the connecting line between the frequency synthesis device and the mixer stage. In In this case, there is the disadvantage that the phase rotator has to work with different frequencies, which makes his Design becomes complicated.

As already mentioned, the amplitude of the incoming carrier wave also changes in time with the frequency changes. If a different type of modulation than the phase modulation described is used, it may be necessary to also to compensate for the amplitude changes, which can be achieved, for example, with the aid of an arrangement according to FIG.

The amplitude correction circuit is shown in FIG. 3 from an automatic variable gain amplifier 4θ, which is in the intermediate frequency part of the receiver according to FIG. 2 and preferably between the bandpass filter 29 and the phase detector 31 becomes, whereby the limiter 30 is unnecessary. The exit of the automatic control amplifier 4θ is provided with an amplitude detector 41 which generates a voltage which is proportional to the amplitude of the output signal of the amplifier and which is fed to a difference generator 42. On one Second input, the difference generator receives a reference voltage from the adjustable reference voltage source 43 »which Voltage dom the setpoint corresponds to the amplitude. The output voltage dos Diff'oronzerzeugers 42 is a converter 44

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which converts the voltage into digital form. The number appearing at the output of the converter 44 is fed to the first register A- of a shift register matrix 46 by an adding device 45. _{This matrix contains a number of individual registers A 1} - A corresponding to the number of frequencies in the frequency pattern. The information in the matrix is shifted in the manner already described for matrix 36 in time with the frequency change, so that for each frequency change the number stored in register A is shifted to A, the number stored in A is shifted to A, etc. In the adding device 45 the number stored in the last register of the matrix 46 is combined with the number appearing at the output of the converter 44, which number corresponds to the differential voltage at the output of the difference generator 42. As a result of the fact that the matrix 46 contains a number of registers corresponding to the number of frequencies in the frequency offset pattern, the two quantities added in the adder 45 always relate to the same frequency.

The numeric stored in the last register

Grosse serves as a control signal for the automatic control amplifier 4o. The gain factor is then regulated in such a way that the output voltage of the difference generator 42 is regulated down to zero by negative feedback in a closed circuit. The amplitude correction is also based on the condition that the reflected wave is relatively stable for the same frequency, as a result of which the signal received by the antenna Ii) is for the same frequency

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has an almost constant amplitude. In the last register of the matrix 46 a number is stored which is obtained by adding together the error voltages of the difference generator 42 which occur during previous intervals for the same frequency. In the device 45, the error voltage occurring at the actual transmission time at the output of the difference generator 42 is added to this number, the sum being fed to the first register of the matrix g 46. When the same frequency reappears, this number is stored in the last register and used to set the gain of amplifier 4θ. After a number of complete work cycles, the gain of the amplifier 4θ is automatically adjusted for each new frequency in such a way that the error voltage at the output of the difference generator 42 is almost equal to zero for all frequencies. The amplitude jumps are then almost completely compensated and a signal of constant amplitude occurs at the output of the amplifier 40. ~

Several modifications of the system described are possible within the scope of the invention. E.g. the phase position of the incoming carrier wave can be measured directly at this wave without the carrier wave being mixed at intermediate frequency is regulated down. As mentioned, this can be achieved in that the receiving-side frequency synthesis device is set so that it delivers exactly the same frequencies as those of the transmitted carrier wave. If this phase measurement is carried out without phase compensation, i.e. without

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the phase rotator, which is set as a function of previously measured phases, in one of the supply lines Mixing stage is arranged, the output signal of the same corresponds to the real phase position of the incoming carrier wave with respect to a reference phase position determined by the frequency synthesis device. The storage device must then be designed in such a way that the number of variables to be stored for each frequency in this device is Output voltage of the mixer / phase detection device without being merged with previously saved values. The storage device can be on any in a suitable manner and, for example, as a static memory device, which has a memory layer for each frequency having. Instead of a digital memory, a memory device can also be used for analog quantities, e.g. a capacitive memory, with a capacitor for each frequency is. The static memory can be combined with a selection mechanism that works in time with the frequency change works to the different memory cells one by one to make it effective. In principle, the useful information can also be provided by any other suitable type of modulation instead of the one described Phase modulation with two alternative phase positions of the transmitted carrier wave, e.g. by frequency or amplitude modulation, be transmitted.

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Claims (1)

Z.PHN. 4769. - 17 PATENT CLAIMS, . 1.1 Device in a system consisting of a transmitter and a receiver for the transmission of information with the help of a high-frequency carrier wave, in which device the frequency of the carrier wave with the help of a periodically active control element ('* -7) arranged in the transmitter step by step between different values according to a predetermined pattern is changed, the receiver containing a mixer (23) in which an incoming carrier wave is combined with a frequency which is changed in accordance with the same pattern as the transmitted carrier frequency with the aid of a similar control element (24-27) that a signal of low bandwidth is generated in the receiver, characterized in that the receiver further contains a phase rotator (28) which is connected to the mixer (23) and is attached to the output of the mixer or is arranged in one of the feed lines of the mixer , while means (31) for detecting the phase position of the incoming end ™ carrier wave with respect to the phase of a locally generated wave and a storage device (36) are provided, which storage device has a number of storage layers (R. - K) and is actuated in time with the frequency change, which storage device is correctly connected to the output of the phase detection mentioned, in which storage positions for each exact frequency iriformatiori over the phase position of the sequence in relation to the IJfäzufjphase is stored, the storage device 101827/0969 2Q617U Z. PHN. U7 (> ¹ ). - 18 - ( '} (j ) controls the Phaseiulrelior (<-8) in such a way that this Phason- (Irclier for each new frequency in a position that corresponds to a value stored in the memory device, which the detected phase position during previous intervals with the same frequency is so that the phase of the received, after passing through the mixing stage and the phase rotator signal is almost kept constant 2. the apparatus of claim I, wherein the changing of the mixing stage of the receiver added frequency at a constant distance from the incoming is displaced. Frequencies, so that after passing through the mixer ('.''3) a signal with a constant intermediate frequency is obtained, characterized in that the' phase rotator (~ 8) is attached to the output of the mixer (2'3) and works with the constant / wiping frequency, the mentioned means for detecting the phase position of the incoming carrier wave being designed as a phase end t ok tor ('3I) nd, of · the phase rotator devices connected downstream J te is t, and one hand on the other hand fed with a locally generated phaseristabilen Zwisehenfrequenzsignal with the Zwisehenfrequenzsignal of the phase rotator ( 'IH) and, and wherein the memory device (36) is constructed such that DEI at the phase detector ( 31) value obtained is added for each new frequency to the previously stored value with respect to the same frequency. 'j. Device according to claim 2 , characterized in that that the storage device is designed as a sliding glass module ("J 6), which consists of a · number of columns (H ₁ - H ) of storage elements, where j <>di> ho I utiinc- ¹¹ 109827/0969 Z.PHN. - 19 - - Information about the measured phase position contains which register matrix is controlled in time with the frequency change in such a way that the information is shifted from column to column for each frequency change, and the information stored in the last column (R) is used to set the phase rotator (28) is, during the ₍₁ R) injected value (31) obtained value is formed in the first column by the value stored in the last column value plus the ύ at the output of Phasendetek- tors. '4. Device according to one of Claims 1 to 3 »characterized in that the receiver further contains an automatic control amplifier (^ 4θ ) which is controlled by a memory (hb) which works in time with the frequency change and a dex 'number of frequencies of the transmitted Carrier wave corresponding number of storage _{layers (A 1} -A), which storage device information from a comparison device (^ 2) for comparing the amplitude of the output voltage of the amplifier with a reference value corresponding to the target amplitude is supplied, the automatic control amplifier (^ O) for each new frequency is controlled by a signal which corresponds to the stored control signal during previous intervals of the same frequency, so that the amplitude of the output voltage of the amplifier is kept almost constant. 109877 / 09G9 «Ο Blank page