US 2208378 A
Description (OCR text may contain errors)
July 16, 1940. D. G. c. LUCK CONTINUOUSLY INDICATING RADIO COMPASS Filed June 50, 1938 3 SheetS--Sheel'l l LV NT Lrtorneg RNV, NRV .N .www
`Iuly 16, 1940.
CONTINUOUSLY INDICATING RADIO COMPASS Filed June 30. 1938 3 Sheets-Sheet 2 55 'ro .amm/can ,57
7a 7.5 VTV? 75T wl T :inventor David C. LLLC' Lttorneg D. G. c. LUCKv I 2,208,378,
July 16, 1940. D. G. c. LUCK CNTINUOUSLY INDICATING RADIO COMPASS I 3 Sheets-Sheet 3 Filed June 30, 1938 PEG.
OUTPUT :inventor 4David, G. C. L iJ/C',
Q Gttorneg atente July i6, i940 CONTINUUUSLY INDICATENG )RADIO CONIPASS David G. C. Luck, Haddon Heights, N. J., assignor to Radio Corporation of America, a co1'- poration oli Eelaware Application June 30, i938, Serial No. 216,825
My invention relates to radio direction iinders and more particularly to a radio direction nder which aiords continuous indication throughout its azimuth.
Numerous types of radio compasses have been disclosed in the prior art. One radio compass is the sci-called left-right type. Such radio compasses indicate departures to the left or right oi a line toward a radio transmitter. It has if) also been proposed in a copending application oi Alexandre Sev, entitled Direct reading goniorneter, Serial No. i15,899, filed December 15, 1936, to continuously indicate the bearing of a radio transmitter with respect to a radio rel ceiver. The system proposed by Sev includes a pair of cross loop antennas of the balanced type and a non-directive antenna In this arrange ment the currents from the several loop sections are successively applied through pairs of diode gc detectors to a common circuit which is also energized by currents from1 the non-directive antenna. My invention improves the Sev system as will hereinafter appear.
It is an object of this invention to provide 25 means for operating a continuously indicating' radio compass employing a cathode ray indicator. It is a further object of this invention to provide means in a radio compass for deriving electrically scale indications to avoid errors which 30 might occur in the use of Xed scales. It is a further object of this invention to provide improved means for deriving side band currents from pairs of directive antennas and carriercurrents from. the non-directive antenna. It is an- 35 other object to provide means for applying modulation currents of suitable phase to successively modulate currents derived from pairs of directive antennas. The invention may be better understood by 40 referring to the accompanyingdrawings in which Figure l is a schematic diagram of one embodiment of the invention;
Figure 2 is a circuit diagram of a phase splitting circuit embodied in the invention; 4,5 Figure 3 is a. circuit diagram showing the circuit for applying signal and scale impulses to the cathode ray tube;
Figure 4 is a schematic circuit diagram of the balanced modulator; and
Figure 5 illustrates one suitable circuit for the impulse generator which is embodied in the invention.
Referring to Fig. 1, a stable oscillator I, preferably of the magnetostrictive type, is connected 55 to three frequency dividers indicated by reference (Ci. 25d- 11) numerals 3, 5, l, respectively. The outputs from the frequency dividers are impressed upon the control circuit of a cathode ray tube 9, as will be hereinafter described. The output from the last stage of the frequency divider 'l is impressed upon the input of a multi-vibrator il, which is connected to a lter it.
The filter output is connected to a pair of phase splitters i5, ll. @ne of the phase splitters l5 is connected to the deflecting coils, or deflecting electrodes, of the cathode ray tube 9. The outputs i9, 2l of the second phase splitter Il are connected respectively to a pair of balanced modulators 23, 25.
The first balanced modulator is connected to a north antenna and a south antenna. The second balanced modulator 25 is connected to an east antenna and a west antenna. The several antennas N, E, S, W are preferably arranged at the corners of a square, as in the Well known Adcock type direction finders. A non-directive or carrier current antenna is positioned at the intersection of the diagonals of the square and is coupled through an amplifier 2 to a radio receiver 29. The outputs of the balanced modulators 23, 25 are likewise coupled to the input of the radio receiver.
Although the invention is not limited to a particular type of receiver, a superheterodyne with a suitable automatic sensitivity control is preferred. The output of the radio receiver 29 is applied to a phase shifter and volume control 3|, which is connected to an amplier arid lter 33. The output of the amplifier and filter 33 isapplied to an impulse generator 35 which is connected to the input circuit of the cathode ray tube 9. The radio receiver may also include a loudspeaker 31.
The operation of the circuit is essentially as follows: Currents having a frequency of the order of 36011, .cycles per second are derived from the oscillator l and frequency divided to provide impulses at the respective rates of '1211, 361i and 121i cycles per second. These impulses are preferably of different amplitudes 'to provide the scale marking impulses 39 for the cathode ray tube 9.
The details and operation of the oscillator and frequency divider circuits are more completely described in U. S. Patent No. 2,121,359, issued June 21, 1938 to David G. C. Luck and Lowell E. Norton and assigned toRadio Corporation of America, or as described irl-Norton application Serial No. 210,574, led May 28, 1938 and assigned to the aforementioned assignee.
The currents from the last stage of the frequency divider 'i are impressed on the multivibrator to derive therefrom a frequency of 1n, or 42% cycles per second. The output currents` from the multi-vibrator, after filtering, are sine wave currents as indicated at 48|. The sine wave currents are applied to the first phase splitter i5 and through the phase splitter to the cathode ray deecting elements. The potentials thus applied to the deecting elements rotate the cathode ray beam in synchronism with theosclllator and thereby correctly apply the various scale marking impulses at intervals of 5, l and 30 electrical degrees.
The currents from the second phase splitter operate in synchronism with the cathode ray beam and modulate, at phase intervals of 90, currents induced in the several directive antennas N, E,S and W. The output currents fromV the balanced modulators -are substantially deprived of their carrier which is supplied by curents from the carrier antenna after amplificaion. l Y
The effect of thus successively modulating the several antennas and supplying carrier currents from the central antenna Vis that of a rotating cardioid response pattern. Thus, the rec'eiver output will be modulated as a. result of the rotation of the cardioid pattern. The phase of this modulation will depend on the direction from which the receiver signal arrives. This phase may be shifted so that the north point of the cathode ray scale can be made to correspond* to a signal derived from a transmitter due north of the carrier antenna, by use of the phase ,l
The receiver output .currents may be` further amplified and filtered to attenuate all the currents of undesired frequencies and to apply lcurrents of modulation frequency to the impulse generator 35. The impulse generator establishes a single impulse 53 whose phase is determined with respect to the modulation phase of the receiver output. Thus, the incoming signal establishing thempulse 83 is applied to the cathode ray tube as shown by the marker signal 45.
' v One satisfactory form of phase splitter for aplet plying the 'modulation currents to the balanced modulator is shown in Fig. 2. In this circut, capacitors di, t@ and resistor 53 are connected in series. The input currents are applied to the junction of capacitor 47 and resistance'53 and to the junction of capacitor 49 and resistance 5|l The resistive bridge is connected between these same junctions and the remaining junctions of the sexialiy connected capacitors and resistors. The bridge arms are provided with adjustable contacts 55, 5i, 59, 6|, which arerespectively connected to control grids in the balanced modu. lators which-are coupled to the N, W, S, E antennas in the order named. This phase splitting and adjusting circuit has been, found to provide a very satisfactory .means of impressing modulation voltages having the required phase progression on the four modulator tubes.
One suitable method of applying the deflecting potentials and the signal and scale input potentials to the cathode ray tube is illustrated in` Fig; 3.- The deflecting elements for the cathode ray tube 83 are represented as coils 65, 61. It should be understood that the coils are arranged 'in pairs Vand are separated substantially 90.
The first and second anodes 69, are connected VVVto a potentiometer 'in the output circuit of the ray velocityV modulator tube 1|. The control grid tion` of tube |01.
pressed on the input of tube |09 which is prefa capacitorjl to the signal and scale input which is also connected to the4 ray velocity modulator tube 1|., The operation of these circuits is more fully described in the above mentioned Norton application.
Referring to Fig. 4, the. thermionic tubes l'l, F9 are connected as a balanced modulator. The modulator currents from the phase splitter tl which corresponds to the phase splitter W oi Fig. l are impressed on grid electrodes t3, 85. The potentiometer 81, -which is connected to screen grid electrodes 9|, 93, forms a suitable means of balancing the modulator'tubes, which are of the two control grid mixer type. The input to the modulator tubes is applied through the transformer 95, the secondary of which is symmetrically connected to control grids of the modulator tubes. Filter circuits 91, 99 are preferably included in the connections between the grid electrodes 83, 85 and the phase splitter cirlcuit di.
One suitable form of impulse generator circuit is show n in Fig. 5. The input terminals are connected to an amplifier |03. 'I'he output circuit of the amplifier includes a iiltercircuit |05.
`The output of the filter is connected to a diode rectier which is part of thermionic tube |01. The rectifier is connected to'the amplifier sec- The amplifier` output is imerably a gas discharge typeof tube. The output terminals are indicated by the reference numeral lil. The foregoing circuit is arranged so that the input sine Wave currents are used to derive the sharply defined impulse marking current. In actual practice, this circuit' arrangement has proven very satisfactory, but it should be understood that the invention is not necessarily limited to the precisefimpulse generator shown.
The operation of the impulse -generator is essentially as follows: The signal currents applied to the input IUI are amplified and filtered. The filtered signals are applied to the diode rectifier which produces unidirectional currents. The unidirectional currents are made asymmetrical 'in form by properly choosing the ratio of capacity C and' resistance R in the rectifier circuit. The currents of asymmetrical wave `form are' difier- -entiated by a lter C'R including capacity and The differentiated currents are am- Ypliiied and further differentiated by another lresistance.
ter C"R". The last mentioned* differentiated currents establish, across the resistor R, potencircuits are known to those skilled in the art,
further description is unnecessary.` Thus, I have described' a continuously indicating radio compass. The scale markings for the compass are appliedelectrically and synchronously with the rotation of a cathode ray. Signals from a transmitter whose bearing is to be determined are modulated in synchronism with the rotation of the cathode ray whereby a signal is derived having a phase dependent upon the bearing of the transmitter. The phase determining this bearing is indicated by applying the received signal to the cathode ray tube.
It should be understood that the non-directive antenna may be omitted andy that the carrier frequency currents may be derived from the directive antennas. It should also be understood that the system may be operated by employing a symmetrical rotating field and obtaining two indications of bearing spaced 180. In such installations there will be a 180 ambiguity. A cathode ray tube 63 having deflecting electrodes or coils disposed as to produce a radial deilection directly may be used, in which case the beam velocity modulator tube 'il is not required.
I claim as my invention:
l. A directive radio receiver including a pairof.
directive antennas, said antennas having response patterns differently oriented, a non-directive antenna, a radio receiver, a pair of balanced modulators, one of said balanced modulators oemg connected between each of said pair of antennas and said radio receiver, a local source of modulation currents, means for applying said modulation currents in quadrature phase to said balanced modulators to successively transfer energy from said directive antennas to said radio receiver so that the resultant response pattern of said directive antennas is eiiectively rotated,
' means for applying energy from said non-directive antenna to said radio receiver, a cathode ray tube, means for obtaining from said modulation current source quadrature phase currents for rotating the cathode ray beam of said cathode ray tube. and means for applying a signal to deect said cathode ray as a function of the phase of the output signals irom'said receiver.
2. In the device of the character of claim 1 means including said quadrature phase currents for electrically applying, a compass scale to said cathode ray tube.
3. A continuously indicating radio compass including, in combination, a pair of directive an tennas, a non-directive antenna, a radio receiver, a pair of balanced modulators respectively connected between said pairs of directive antennas and the input of said radio receiver, a local source of modulation currents, meansfor obtaining currents of quadrature phase relation from said modulation currents, means for applying said for rotating saidcathode ray. and means for ap-v n plying a signal impulse derivedfrom the output of said radio receiver to deilect said cathode ray in a radial direction.
4. In a device of the character of claim 3 means operatively related to the next to the last mentioned means ior applying scale marking impulses to said cathode ray tube.
5. 'I'he method of continuously indicating the bearing of a radio transmitter Iwith respect to a radio receiver including a pair o! directive antennas, a non-directive antenna and a cathode ray tube which includes impressing radio waves from said transmitter on said antennas, successively modulating energy from each of said directive antennas, combining said modulated energy with carrier frequency energy from said non-directive antenna so that the resultant response pattern of said directive antennas is effectively rotated, rotating the cathode ray beam of said cathode ray tube in synchronism with the rotation of theresultant response pattern of said directive antennas, and applying an impulse derived from said combined energy to deilect and visibly indicate said cathode ray.
6. A directive radio receiver including a pair of directive antennas, said antennas having response patterns diierently oriented, a radio receiver, a source of modulation currents, means for obtaining currents in quadrature phase relation from said modulation currents, means for applying said quadrature phase currents to successively transfer energy from said directive antennas to said radio receiver whereby a rotating response pattern is obtained, a. cathode ray tube, means including said quadrature phase currents for rotating the cathode ray beam of saidcathode ray tube in synchronism with the rotation of said response pattern,and means for deflecting said cathode ray to provide marks as a function of the phase of the output signals from said receiver.
7. In a device of the character of claim 6, means including said quadrature phase currents forelectrically applying in synchronism with the rotation of said beam a compass scale to said cathode ray tube.
8. A continuously indicating radio compass including, in combination, a, pair of directive antennas, a radio receiver, a pair of balanced modulators for connecting said directive antennas to the input of said radio receiver, a source of modulation current, means for deriving two phases from said modulation current source, means for applying said phases to said pair of modulators whereby a rotating response pattern is obtained, a cathode ray tube, means for applying said phases to rotate the cathode ray of said tube in synchronism with the rotation of,said pattern, and means for applying signal impulses derived from the output of said radio receiver to deect said cathode ray.
DAVID G. C. LUCK.