DK162728B - RECEIVER DEVICE FOR AT LEAST TWO RADIO NAVIGATION SYSTEMS - Google Patents

Description

in

DK 162728 B

The invention relates to a receiver apparatus of the kind specified in the preamble of claim 1.

Existing radio navigation receivers of this type are used to locate the position of a moving object by means of broadcasts from at least two radio navigation systems. Measurements from at least two systems are compared in such receivers, which are more expensive to manufacture, as it is necessary to combine two separate receivers in a single box.

US Patent No. 3,936,763 discloses an apparatus for simultaneously amplifying two radio navigation signal frequencies, e.g. OMEGA, without changing the phase of the signals (modulus ΙΊΓ).

US Patent No. 3,936,828 discloses a radio navigation apparatus having a number of receivers which are too connected to a multiplexer for a computer.

The object of the invention is to provide a receiver apparatus of the kind initially indicated, which has an improved structure which leads to a reduced production cost.

This is achieved in accordance with the invention in that the receiver apparatus indicated at the beginning is peculiar to the characteristic part of claim 1.

The microprocessor may also be adapted to change the gain rate of the automatically controlled gain control circuit as set forth in claim 2.

In one embodiment of receiving a radio navigation system with frequency change, the apparatus comprises a mixing circuit for receiving the signal from a local

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2 oscillator and the microprocessor is arranged to switch the switch so that the mixing circuit also receives signals from the receiver filter of the system to be received with a frequency change and where a filter for another system receives the output of the mixing circuit where the output signal of the filter generates the switch output. The radio navigation system for reception with frequency change may be the LORAN system in the interference-detecting phase where the local 10 oscillator can be tuned.

The apparatus may further be arranged to receive at least three radio navigation systems, the apparatus in this case for receiving a first dual frequency change system comprising frequency mixing circuits, each receiving a signal from a local oscillator and the microprocessor adapted to switching the switch such that the first mixing circuit also receives the output signals from the receiver filter for the first system, that a filter for the second system receives the output signals from the first mixing circuit, the second mixing circuit also receives the output signals from the second system filter, the third system filter receives the output signals from the second mixing circuit, and the output signal 25 from the third filter generates the output signal of the switch. The first system may be selected from the group comprising marker beacon, radio beacon and directional search transmitters, and the second system may be a LORAN system and the third system an OMEGA system wherein at least 30 the first oscillator belonging to the first mixing circuit can be tuned. In a recommended embodiment, the first system may be a differential OMEGA system transmitted from a radio or marking beacon.

In a recommended alternative to lead Ice's form,

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3, the circuit is controlled by the associated oscillator at least in the presence of an activation signal representing the receiver configuration.

In another embodiment, the microprocessor is adapted to store programmed time intervals, and arranged, by means of integration, to calculate the time elapsed between completion of one sample period for one system and the start of sample period 10 for the next system, so that no time error is less than a given duration and that this duration plus the inverse sample rate for both systems is also not exceeded, and that resumption of synchronization is in a stationary form.

The invention will be further explained by the description of some embodiments, with reference to the drawing, in which fig. 1 shows a receiver apparatus using time-distributed multiplexing; FIG. Figures 2a and 2b show OMEGA and LORAN sample patterns; 3 shows the control of the switch between OMEGA and LORAN; FIG. 4 and 5 show the recommended alternative embodiments using at least one OMEGA filter for a frequency change which involves receiving another radio navigation system, while FIGS. 6 shows a variant of the embodiment of FIG. 4.

FIG. 1 shows a combined receiver for OMEGA and LORAN C systems, the receivers comprising a filter and switching circuit 1 containing OMEGA filters 11, a LORAN C filter 12

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4 and a switch 14. Standard OMEGA filters include three individual filters Fq (10.2 kHz), F ^ (11.3 kHz) and F ^ (13.6 kHz) tuned to the three frequencies normally used to calculate the position of a moving object. Each of these 5 filters can have a bandpass between - 10 and + -500 Hz. The LORAN C filter 12 has a nominal frequency of 100 kHz and a bandpass of approx. - 10 kHz. When switch 14 receives an order, it controls these filters so that their output terminals are connected in turn to the input terminal of an automatic amplifier control circuit 1 connected to a digital exemplary circuit 3 which includes a sample circuit 31 and a digital / analog converter 32.

The sample circuit 31 is controlled by a time base 3 which receives pulses from a local clock 6. The setting 15 of the switch 14 and the division ratio of the time base 5 are controlled by a microprocessor 4 to produce a time-distributed multiplexing of the reception of OMEGA and LORAN. C

systems. The amplifier control circuit 2 may be self-controlled, or controlled by microprocessors 4, so that the gain corresponds to a maximum number of significant bits during the turnover of the transducer 32. The amplifier circuit 2 may e.g. be a stepwise programmable amplifier. The required amplitude of the programmable amplifier is always locked at the receiving station, which is well known through the selected input filter (reception frequency) and through the synchronization of the system (the station is activated at a given time by the received frequency). For the OMEGA system there are three frequencies and eight stations, ie. twenty-four possible levels of gain in the storage, and for the 30 LORAN C system there is a frequency and four stations, ie. five possible levels of reinforcement in the warehouse. These amplifier levels are determined by examining the output of the A / D converter 32, and by increasing the amplitude of the amplifier 2 to a given percentage (e.g., 10%) of cut-off samples obtained in the transducer 32. These individual automatic amplifier control circuits for each station are slowly stabilized from an average starting level. micro-

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The processor stores the required gain ratios for each station and controls the amplifier circuit 1 and the filters used, as well as the sample time. This can be achieved by changing the gain rate with Vi at each level change, and 5 by four bits, ie. 16 possible amplifier levels, it is possible to achieve a dynamic reception.

The time base 5 may be a programmable time interval generator (for example, a MOTOROLA 6840 circuit) which secures the samples at times entered into the microprocessor's program.

Since the OMEGA system uses time signals in groups of eight by 10 seconds format, while the LORAN C system uses an impulse base at a faster repetition rate (40 to 199 ms), ten seconds will be an appropriate time unit to multiplex the two systems by the OMEGA signals as synchronization, to correspond to eight consecutive signals, which preferably have the same OMEGA format.

After starting the receiver, the following steps are performed.

The first step is to generate a synchronization of 2 (1 OMEGA format. · The apparatus is used as an OMEGA receiver with switching between filters Fg and F2J until synchronization of the OMEGA format is produced, so that the multi-plexing is adjusted to the OMEGA format during the periods. The second step is to generate synchronization for the two systems.

Provided the local clock 6 is sufficiently stable, at least statistically, this step can be produced by multiplexing operations. Statistical collection is generated for a number of OMEGA formats, e.g. 5-10 for each system so that position data is generated. During the multiplexing, the microprocessor 4 stores the accumulated pulses from the local clock 6, while keeping the instructions for the time base 5 updated, as do the data for previous samples. The instructions for the time base 5 involve an order to generate a sample pulse after a program.

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6 noticeable number of jump pulses from the local clock 6. The accumulation of these jump instructions is therefore representative of the accumulation of the local clock pulses. The apparatus can then function in continuous multiplexing, ie. alternately as an OMEGA receiver over an OMEGA format and as a LORAN C receiver over the next format.

Continuous clock pulses are used to control the multiplexing and to recover the synchronization, which is almost instantaneous after switching from one system to another.

10 It can be seen from FIG. 2a, the OMEGA treatment is generated by exemplifying the three frequencies 10.2 11.3 and 13.6 Khz by means of pulses in cross-phase pairs, i.e. separated by ΤΓ / 2 (24, 22 and 18 microseconds), modulus 2 TV. The sampling frequency F ^. is a sub-multiple of the three above OMEGA frequencies, e.g.

188.88 Hz. If Tg, and T ^ are periods corresponding to the frequencies Fg, F ^ and F ^ and Kg, K ^ and are integers not less than 0, then the microprocessor 4 produces during a period 1 / F ^. a sequence of 3 pairs of sample pulses at intervals of Tg (1/4 + Kg), T ^ (1/4 + K ^) and 1 ^ (1/4 + 20) where the first pulses of subsequent pairs are preferably separated by 1 / K 3, K 2, K 2, and K 2 are chosen so that the sample pulses are distributed with the period T 2 (which in this example is about 6.29 milliseconds), which of course are only effective during the useful portion of the signals. , 25 depending on the signals lasts from 0.9 - 1.2 seconds, a consequence of which is that the OMEGA format starts and ends with a time error, since the effective part of the first and last signal is 0.9 and 1 second respectively. .

The filters need only be switched between the OMEGA system 30 and the LORAN C system every ten seconds, and the associated sample rate is generated. Updating current clock pulses means that synchronization of one system is not performed when the device processes the other system.

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7

As shown in FIG. 2b, the LORAN C system comprises the transmission of pulse sequences from 4 local stations, a main station and 3 slave stations X, Y and Z, with a repetition rate Tg which, depending on local station groups, may be approx. 40 - 100 milli-5 seconds. Each station in turn transmits 8 pulses. Three pulses are performed for each pulse, ie. 96 samples in the interval Tg.

FIG. 3 shows the sequence of four 10-second periods, synchronized on the OMEGA format, for multiplexing reception of 10 OMEGA and LORAN C, ie. periods corresponding to the periods (N-1) and N of the LORAN C system, and to the periods N and (N + 1) of the OMEGA system. The synchronization on the OMEGA format gives the time t ^ every 10 seconds. The transition between OMEGA and LORAN C will be described below.

The exact timing of the end of the OMEGA period N is known through the programmed intervals of the microprocessor at the time base level. Assuming that this N period is the one in which the OMEGA synchronization is generated, any time intervalAtn, e.g. equal to 0.5 - 1.5 Tg, and 20 at the end of this interval, the LORAN C establishment from time t2 is activated. As can be seen in FIG. 2b, this time t 2 can be applied in any manner with respect to the LORAN C broadcasting periods. From t2, the microprocessor calculates the time tg within the period N corresponding to the most favorable LORAN example so that such a sample is maintained. Time tQ is, on the one hand, separated 'from time t2 by an interval K' Tr, where K 'is an integer, and on the other hand from time T'j, which indicates the start of the period (N + l) corresponding to The OMEGA sample for a time ^ t '^ not less than Tg. 1

For the LORAN sample period (N + 1), the microprocessor calculates the interval K + + Tg separation time tg in the LORAN sample period N from time t2 in the LORAN sample period N + 1. Kfg + 2 is an integer and £ t ^ must be as small as possible though with a lower bound, e.g. 0.5 Tg, so that microprocessing

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The soren has enough time to perform the necessary switches. Under these conditions, between 0.5 and 1.5 TG will vary for subsequent sample periods with a continuous cycle as long as the apparatus remains operational.

FIG. 4 shows a 0MEGA / LORAN C receiver for the 285-425 kHz band 5 comprising a recommended embodiment comprising filters 11 and 12 (Fig. 1) and switching circuit 14 in the form of switches Ag, A are located at the output terminals of the filters Fg, F ^, and 12. This embodiment comprises more refined switching circuits comprising 1Π switches, which allow the use of LORAN C filter and an OMEGA filter (e.g., produce a dual frequency change for receiving broadcasts, such as directional search signals, radio beacon signals, or marker signals.

A filter 1 is combined with an antenna capable of receiving all three systems. The bandpass of Filter 13 extends from 285 to 425 KHz, making it equally suitable for directional search and for radio and marker signals such as broadcasting differential OMEGA corrections. Filter 13 is connected to a mixing circuit 15 which also receives signals from 2Π a local oscillator 0LL, and its output terminal is connected to the input terminal of the LORAN C filter 12 through a contact G. The output terminal of the LORAN C filter is connected to a contact D and to a mixing circuit 14 ', which also receives signals from a local oscillator 0, and the output terminal of the mixing circuit is connected to the input terminal of the filter through switch E.

The following three types of operation are made possible by the multiplex: a - OMEGA reception: contacts D, G and E are open, a con-3Π beat B2 is closed and contacts Ag, A ^ and A ^ are closed in turn for to receive the sample of the three normal OMEGA frequencies.

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9 b - LORAN C reception: contacts Ag, Ap A ^ and G are open and in contact C above LORAN C filter 12 is closed just like switch D.

c - 285-425 KHz band reception: contacts Ag, A ^, B2, C and 5 D are open and contacts A ^, E and G are closed, signals from filter 13 are transmitted to LORAN C filter 12 after passage through the mixing circuit 15, then to the filter F after passing through the mixing circuit 14, the LORAC C and the F2 filters, then act as between frequency filters for 285-425 10 KHz band reception.

Details in the 285-425 KHz band reception are described below. The filter has a frequency of 13.6 KHz and if a local oscillator 0L2 with a fixed frequency F02 is selected, the first intermediate frequency FI ^ will be as follows (unit 1 KHz): FIX = F02 - 13.6 where FI ^ should be within the bandpass of the LORAN C filter 12. If F02 is 125 KHz, FIj will be 111.4 KHz, which is on the edge of the LORAN C filter band. However, this keeps the mirror frequency of the second frequency change as far away as possible, ie. F1 + 2F2, ie 138.6 KHz.

The tuning of the 285-425 KHz band is produced by the local oscillator OL ^, which is a synthesizer whose frequency range is from 285 + FI ^ to 425 + FI ^, i.e. in this case 396.4 to 536.4 KHz. The mirror frequency of the first frequency change ranges from 285 + 2FI ^ to 425 + 2FI ^, i.e.

25 507.8 to 647.8 KHz.

In practice, it is advisable to use a synthesizer OL1 with an output frequency varying in steps of 100 or 200 Hz and a filter F2 with a band pass of 300 Hz. These parameters are particularly suitable for OMEGA reception and for reception 30 in the range of 285-425 KHz, and especially for receiving

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10 profitable OMEGA broadcasts generated by phase modulation of the radio or marker signal. A synthesizer may also be used for the local oscillator OL ^ to produce a fine tuning of the frequency.

FIG. 5 shows an OMEGA and LORAN C receiver using an OMEGA filter, such as F 1, to take measurements of LORAN C interference so that it is possible to detect the broadcasts near the LORAN system used 90 -100 KHz band and that their frequencies are measured. One or more suitable resonance ^ 10 circuits can then be tuned so that arbitrary interferences are eliminated. Broadcasts that are likely to cause interference include frequencies 85 KHz and ΓΓ2 KHz in the OECCA system.

FIG. 5 shows components already included in FIG. 4, namely the filters Fg, F ^, F2 99-12, and the contacts Ag, A ^, A2, 15 B ^, D and E, as well as the mixing circuit 14 which receives signals from the local oscillator 0L2 ·

To detect the interferences, the LORAN C filter receives 12 signals from the 90 - 110 KHz LORAN C band and sidebands 70 - 90 KHz and 110 - 130 KHz, which of course is attenuated by the filter 12. The local oscillator 0L2 is a variable fre frequency synthesizer so that the 70 - 90 KHz and 110 - 130 KHz sidebands are brought, by means of a frequency change, to a frequency of 13.6 KHz.

For the 70 - 90 KHz band, the local oscillator 0L2's frequency F02 range can range from 70 - 13.6 to 90 - 13.6 KHz, ie. 57.4 - 77.4 KHz, with a mirror frequency of F02 ~ 13.6, i.e. 43.8 - 63.8 KHz.

For the 110 - 130 KHz band, the synthesizer 0L2's frequency F02 can range from 110 + 13.6 to 130 + 13.6 KHz, ie. 123.6 to 30 143.6 KHz, with a mirror frequency of F02 + 13.6 ie, '137.2 to 157.2 KHz.

11

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In a recommended embodiment, the frequency of the synthesizer Ol 2 varies in steps of 200 or 500 Hz, with one or more 1 KHz bandpass resonant circuits. FIG. 1 shows two such resonant circuits REJ1 and RE1 which can be tuned by a variable capacitor (alternatively a variable capacity diode whose voltage is controlled by the microprocessor) and which can be tuned to a broadcast received on a sideband. FIG. 6 shows an alternative embodiment of the embodiment of FIG. 4. The switches E and G are used as the mixing circuits. Oscillators 0L ^ 10 and OL ^ receive the output of OG circuits 41 and 42.

The one input terminal of each of these AND circuits 41 and 42 receives a signal S representing the receiver configuration, ie. logical 1 when multiplexing is received in the 285-425 KHz band. The second input terminal of the AND circuits 41 and 42 receives signals from the associated local clock, ie. 0L ^ and which switch from 0 to 1 at the desired frequency. This gives a frequency change with a minimum of components. When the receiver apparatus is in OMEGA or LORANI C reception configuration, the signal S is logical 0, which results in the output terminals of the OG circuits 41 and 42 being logical 0 and the contacts E and G being opened.

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Claims (11)

1. Receiver apparatus for at least two radio navigation systems with receiver means (11, 12, 13) for radio navigation signals, a multipath switch (14), an automatic controlled amplifier circuit (2), a digital sampling circuit (3) receiving sample pulses , a local clock sensor (6), a microprocessor (4) receiving the sampling pulses of said digital sampling circuit (3) and arranged to perform a signal processing and position calculations in accordance with the radio navigation systems, characterized in that said receiver means consist of a the number of receiver filters (11, 12, 13) corresponding to said radio navigation systems and the switch with the switch (14), that the output of the switch (14) is connected to the sample circuit (3) via the automatically controlled amplifier circuit (2), that a time base ( 5) which receives the signal of said clock transducer (6) divides this into a ratio which allows multiple sample pulses 20 during a transmit an emission interval comprising the longest transmission interval of the radio navigation system to output said digital sample pulses, and that the microprocessor (4) is adapted to produce a sequential switching of the multipath switch (14) 25 and adapted to change the division ratio of the time base (5) so that the sample becomes synchronized with other radio navigation systems so that a time multiplexing is produced upon receiving said systems. Apparatus according to claim 1, characterized in that the microprocessor (4) is adapted to change the degree of strength of the automatically controlled amplifier circuit (2). DK 162728 B 13 Apparatus according to claim 1 or 2, characterized in that, for receiving a radio navigation system with frequency change, a mixing circuit (14 ') for receiving the signal from a local oscillator (Ol 2) comprises the microprocessor being arranged for changing the switch (14) such that the mixing circuit (14 ') also receives signals from the receiver filter for the system to be received with a frequency change and that a filter for another system receives the output signal of the mixing circuit (14), and that the output signal of this filter produces the switch output signal. Apparatus according to claims 1 to 3, characterized in that it is arranged to receive at least three radio navigation systems and comprises, for receiving 15 a first dual frequency change system, two frequency mixing circuits (14 *, 15) each in particular, receives a signal from a local oscillator (0L ^, 01 ^) and the microprocessor (4) is arranged to switch the switch such that the first mixing circuit 20 (15) also receives the output signals from the receiving filter from the first system, that the second mixing circuit (14 ') also receives the output signals from the filter of the second system, a filter for a third system receives the output signals of the second mixing circuit 25 (14'), and that the output of this third filter generates the output signal of the switch (14). Apparatus according to claim 4, characterized in that the first system is selected from the group comprising marker lighthouse, radio beacon and directional search transmitters, that the second system is a LORAN, long-range navigation system, that the third system is an OMEGA system, and that at least the first local oscillator (OL ^) of the first mixing circuit (15) can be tuned. DK 162728 B 14 Apparatus according to claim 5, characterized in that the first system is the differential OMEGA system which is emitted from a radio or marking beacon. Apparatus according to claim 3, characterized in that the radio navigation system to be received with frequency change is the LORAN system in the interference detection phase and the local oscillator can be tuned. Apparatus according to any one or more of claims 10 to 7, characterized in that one local oscillator (OL1, OL2) is a synthesizer. Apparatus according to any one or more of claims 3 to 8, characterized in that the mixing circuit (14 ', 15) is a switch (EG) controlled by the corresponding local oscillator (0L ^, OL ^). at least in the presence of an activation signal (S) representing the receiver configuration. Apparatus according to claim 9, characterized in that the switch (E, G) receives an output of an AND circuit (41, 42), wherein one input terminal of the circuit receives the corresponding local oscillator signal (OL ·, 0I_2)> and wherein the second input terminal receives the logic activation signal (5). Apparatus according to any one or more of claims 25 to 10, characterized in that the microprocessor (4) is arranged to store programmed time intervals and arranged, by means of iteration, to calculate the time elapsed (At ') between the end of a sample period for one system and the start of a sample period for the next system so that no time error is less than a given duration, and that this duration plus the inverse sample frequency for both systems is not exceeded either, as well as resuming the synchronization in a stationary form.