US2445621A - Demodulator device for frequency and amplitude modulation - Google Patents

Description

E. H. LANGE'. DEMODULATOR DEVICE FOR FREQUENCY July 20, 1948.

AND AMPLITUDE MODULATIONS Filed Nov. 5, 1945 INVENTO R Patented July 20, 1948 UNITED STATES PATENT OFFICE DEMODULATOR DEVICE FOR FREQUENCY AND AMPLITUDE MODULATION i 21 Claims.

This invention relates to demodulators for carrier waves having frequency-modulation or amplitude-modulation, or having both of these modulations, and more particularly to such demodulators in connection with receiving systems for these carrier waves.

The principal object of this invention is to provide such demodulator devices with economy and simplicity of component circuit parts and electronic equipment, and with improved facilities for tuning, for compensating amplitude-modulation, and for control of average signal amplitudes.

A first object of this invention is to provide unilaterally-grounded output voltages forthe series-parallel circuit type frequency-demodulator described in U. S. Patent 2,369,055, of February 6, 1945, and more particularly to provide such operation with direct anode-cathode series connection of the series-parallel circuit as distinguished from a shunt supply of said circuit, and with a double-diode rectifier employing diodeanodes each capable of thermionic conductance with said cathode, and in the same tube with the common cathode.

A second object of this invention is to provide such unilaterallygrounded output voltages upon a conductive connection to ground, and to provide sustained output voltages which persist as long as a frequency deviation exists between the carrier wave and the centre or balance-frequency of the demodulator, for use in controlling the frequency of waves impressed upon the demodulator, for example in a superheterodyne receiver, and

when receiving either amplitude-modulation or frequency-modulation.

A third object is to prow'de simple separating means for separating or 'annulling the voltages of carrier frequency from the desired output voltages of modulation frequency.

A fourth object is to provide filter means for demodulators of the unilaterally-grounded common cathode type, whereby the grid. control means of a pre-amplifier coupled with such a demodulator is supplied with either amplitudeenvelope responsive and opposing voltages for reducing undesired amplitude-modulation, or average-amplitude responsive voltages for regulating signal strength employed, or both, and through a conductive path between the ground and said grid control means of the pre-amplifier.

A fifth object of this invention is to provide the features stated in the second to fourth objects inclusive through simple structures, applicable also to other types of demodulator circuit than I designated in the first object, and. also employing a common cathode type double-diode rectifier for supplying such unilaterally-grounded output voltages. r

A sixth object is to provide resistance-capaci tance filter means in the common cathode type demodulators of this invention, for transferring to the quadrature-phase controlling grid of an oscillator or reactance-modulator connected with an oscillator in a superheterodyne receiver, sustained voltages, determined by the amount and algebraic sign of the difference between the balance-frequency of the demodulator and the centre-frequency or unmodulated frequency of the carrier wave, independent of the presence of frequency-modulation upon the carrier wave, and for alignment of tuning in the receiver.

A seventh object of this invention is to provide simple impedance-balance means for annullin or substantially reducing. minor impedanceasymmetry introduced by unilateral impedance connections of this invention.

ture-phase or frequency-controlling grid, of a thermionic generator system, and with means employable for compensating impedance-asymmetry. Fig. 2 illustrates a pre-amplifier coupled with the input-impedance of one'of the demodulators of this invention, and a transfer-filter means for transferring control voltages from a common conductive path-between the diode-anodes and the cathode of the demodulators of this invention, and illustrated with particular reference to the demodulator of Fig. 1.; v v

Fig. 3 illustrates application of the principles and structure of this invention toanother type of demodulator circuit.

Referring to the figures, at His athermionic tube having the cathode l4, cathode-terminal Ida, the diode-anodes l2 and I3 each capable of thermionic conductance with the common cathode I4; also having a control-grid l9 connected through input-impedance 20 and conductor 2| to terminal Illa, which terminal is either directly connected to terminal Ma, or connected to terminal 14a through a bias-resistance I having one terminal connected to terminal Ma. At i6 is a third anode capable of thermionic conductance with the common cathode [4, it being understood that thermionic conductance between the third anode l6 and cathode I4 is controllable by the control-grid [9 between cathode l4 and anode l6.' At ll, Fig. 1, is shown a suppressorgrid directly connected to cathode terminal Ma and at I8 is a screen-grid understood to be connected to a positive terminal upon the source 24 of unidirectional voltage, the source 24 having its negative terminal connected to ground 22. For simplicity of illustration the suppressor-grid l1 and screen-grid l8 are omitted from Figs. 2 and 3, tube l5, however it will be understood that these grids may be present and similarly connected in these figures, for controlling the transconductance and impedance properties in a mannerwell understood;

One of'the diode-anodes, for example diodeanode I2 is connected directly to ground 22 through conductor 22- oi negligible impedance. At 111 is a junction-terminal upon a phase-shifting networkiconnected to the diode-anodes i2 and i3 and to the common cathode I l, and between junction-terminal m and common cathode I4 is acorn-men conductive path for thermionic currents of both diode-anodes l2 and I3.

ReferringtoFig, 1, the positive terminal of source' 24 is directly connectedthrough conductor 25 to the third anode it of tube l5. For purposescf illustration it will be understood that the source of unidirectional voltage 24 may be a battery or'other we'l'l know-n means, and having a conductive path from thepositive terminal to ground such as illustrated by resistance 5, for unidirectional components of current. At 9 is an inductance coil, and at 8 is a variable condenser connected across the terminals of coil 9, and for tuning coil 9 to resonance with the carrier frequency impressed upon input-impedance #20. At 6 is a high-frequency choke-coil connected between the cathode-terminal I la-and the junctionterm-ina-l m upon the inductance coil 9, the junction-"terminaim being between the terminals b and d of the inductance coil 9, which terminals are connected to condenser 8. "similarly connected in Fig. 2, except that series resistance may be included in the conductive path from junction-terminal m to cathode-terminal 'M a 'as hereafter pointed out. I

Terminal d is connected through vdiode-resistor 1' to terminal p of dioderesistor T, which terminal p is directly connected :to diode-anode i3; likewise terminal b is connected through diode-resistor -r' to terminal -q of diode-resistor 'v" ,which terminal g is directlyconnectedtodiodeanode l2. Diode-resistor -r is shunted iby. oon denser45, andlikewise diode-resistor -1" isshunted condenser '46. Terminals d and b are similarly connected in Fig.2. At K-is a switch-blade understood to'be-directly connected by connector are to the control-grid of anamplifier for amplifying-thedemodulated voltages oieither amplitudemodulation or frequency-modulation, and the switch-terminal indicated by :A. for amplitude modulation is directly connected to the tor-- minal of diode-resistor =1" opposite the terminal "q 'of 'said resistor, that is to terminal b. The switch terininal indicated by F. M; forirequencymodulation-is connected through coil'l 'by way of conductor 1 to the "terminal pof diode-resistor Choke-coil is I r. Coil l is understood to be inductively coupled with coil 9, and to be so connected in the circuit through conductor I that the resultant alternating voltage of carrier frequency in the circuit q-rb-9drp--I-l-F. M. is substantially zero, the magnitude of voltage induced in coil 1 by carrier frequency of coil 9 being understood to be equalized with the magnitude of alternating voltage in coil 9. Connected in series between the terminal and ground 22 is the filter-resistance 28 connected to the terminal F. M. and the filter-condenser 29 connected to ground 22. The junction between filter-resistance 28 and filter-condenser 29 is understood to be connected by the conductor Gqo to the frequency-controlling grid of a thermionic generator system of a superheterodyne receiver, for example to the quadrature-p-hase controlling grid of a thermionic oscillator, or reactance modulator connected with a generator, and for modifying the resultant carrier frequency impressed upon the inputr-impedance 20.

At 2v is a high-frequency choke-coil having. one terminal connected to the ground 22, and the other terminal 3 connected to the junctionetere minal m. At 2' is another high-frequency chokecoil having one terminal connected through condenser u to the ungrounded diode-anode, for example diode-anode l3, and the other terminal connected to the switch-blade K" which is con.- nectable to switch-termina1-3 I connected to the 1331:- minal s of the chokeecoil 2. Choke-coil 2 is simie larly connected in Fig. 3; likewise it will be under: stood that the choke-coil 2- for compensating impedan'ceeasymmetry is similarly connectable in Fig. 3 between the terminal s of choke-coil 2 and the ungrounded diode-anode 13.

Referring to Fig. 3., third anode i6 is connected through the primary coils 9'?) and 91av in series to the positive terminal of source 24, and byapass condenser 23 is connected from ground conducr tor22 to the positive terminal of source 29 as in Fig. 1. Coil 9191s inductively coupled with coil 9'71, and coil 9a is'inductively coupled with coil 9m, and coils 9a and 9b are connected in series. at the junction-terminal m, the terminal 11 of coil 9b opposite terminal m being connected through diode-resistor r to diodeeanode. l3, and the. terminal b of coil 9a opposite terminal m being connected through diode-resistor r to diode-anode l2. Terminal m is connected to cathodeeter-minal I l-a through the bias-resistance Hi. It will be understood that bias-resistance i0 is for introducing a small voltage drop through flow there.- throughof steady. component of current from third anode I6 to cathode 1A, for negatively bias.- ing the control-grid Hi. from cathode 14; that the employment of such negative biasing means optional. Negative bias voltage so introduced biases the diode-anodes. from, the, cathode it, however when small amounts .of such bias are employed in relation to the maximumvol-fia esfimployed upon the diode-anodes from the network, such small amounts do not appreciably af ect the operation of the demodulator. It will be under.- stood that the condenser H shunted across the bias-resistance. 10 has a small impedance in re; lation to resistance H1 for the low or modulation frequencies, and that such biasing means may also be employed inFig. -1, similarly connected to cathode IA and in series with coil 5, between terminal lfla and terminal l,.4,a. ,Gpil 9b is shunted :by tuning condenser 8b, and likewise coil 9a -is shunted 'by tuning condenser dd; these tuning condensers may :be mechanically connected as indicated by connection 50, indicating anelectricallyinsulated mechanical connection between rotors of condensers 8a, 8b. Tunablecircuits between terminals mb' and between m-d' are understood to be spaced as-to tuning, the carrier frequency being intermediate with reference to resonance frequencies set by condensers 8a-and 8b, as hereafter further pointed out. At la is an inductance coil inductively coupled with coil 9a, and at lb is another inductance. coil inductively coupled with coil 91). Coils la and lb are connected in series, one terminal of coil 1b being connected to the ungrounded diode-anode I3 and one terminal of coil Ia being connected to the terminal F. M. of the selector switch having switch-blade K, as heretofore described. It will be understood that coils 1a. and lb are each so connected in the series circuit 22r'--b-m d 1 |b--'|a--F. M. that thecarrier-frequency voltage in 9b is equalized by the carrier-frequency voltage in 1b, and likewise the voltage in 9a equalized by the voltage in la, leaving only the resultant of the rectified voltages across 1" and r in said series circuit, the resultantvoltage of carrier-frequency being substantially annulled.

Referring to Fig. 2, at 32 is a thermionic tube of a pre-amplifier having an output-impedance 20a coupled with the input-impedance 20, for example of demodulator of Fig. 1, and for transferring voltages of carrier frequency to inputimpedance 2| Tube 32 is understood to have a cathode 35 connected to ground 22, for example through a bias-resistor, to have a control grid 33 connected to one terminal of the input coil 20b of the mare-amplifier, and tohave an anode 34 connected with the positive terminal of a source of unidirectional voltage through output-impedance 20a, or otherwise energized from a unidirectional voltage source. Control-grid 33 is understood to control thermionic currents between anode 34 and cathode 35; also it will be understood that other grid controls may be present such as a screen-grid and suppressor-grid between the anode 34 and control-grid 33, for controlling currents between anode 34 and cathode 35, and'for controlling transconductance and impedance characteristics of tube 32, in a manner well known, and with particular reference to transconductance of control-grid 33. Connected in series in the conductive path between junctionterminal m and the terminal |4a of cathode I4, is the control-resistor r, connected between the junction-terminal "m and the terminal .9 of the high-frequency choke-coil 2 one terminal of control-resistor r being directly connected to junction-terminal m. Control-resistance 1'" is shunted by the control-condenser 31. Connected between the junction-terminal m and the ground 22, is the high-frequency choke-coil 2a in series with the high-frequency by-pass condenser 38, one terminal of coil 2a being connected to junction-terminal m and one terminal of condenser 38 being connected to ground 22. Shunted across the terminals of by-pass condenser 38 is the fllter resistance 39 in series with the filter-condenser 40, one terminal of resistance 39 being connected to ground 22 and one terminal of condenser 40 being connected to the ungrounded terminal of condenser 38. The common terminal 43 between condenser 40 and resistance 33 is connectable by switch-blade K through conductor 45 to the terminal of the input coil 23b of the pre-amplifier, opposite the'terminal of said coil connected to control-grid 33'of tube 32. Likewise shunted across the terminals of by-lpass condenser 38 is the filter-resistance 42 in series with the filter-condenser 4|, one terminal of condenser 4| being connected to ground 22, and one terminal of. resistance 42 being connected to the ungrounded terminal of condenser 38. r The common terminal 44 between resistance 42 and condenser M is connectable by switch-blade K through conductor 45to control-grid 33 of tubev 32, through input coil 20b.

7 It will be understood that the control-resistor r" shuntedby condenser 31 illustrated with reference to Fig. 1 can be likewise connected in the structure of Fig. 3, in the common conductive path between cathode l4 and junction-terminal m, and between the junction-terminal m and the terminal 8 of choke-coil 2.

Condensers 45, 46, and 31, shuntedrespectively across the resistances r, r, and 1", are understood to be for smoothing out the unidirectional voltages set up across these resistances by unidirectional currents respectively to diode-anode l3, diode-anode l2, and to both of these diodeanodes, and to provide a time-constant sufiiciently large in relation to the half-cycle time of the carrier wave to smooth out the rectified pulses of carrier frequency.

Referring to Fig. 1, operation of the devices will be evident from the following further considerations. The path for the unidirectional current component fromiground 22 through source 24, and third anode IE to cathode I4, is completed through choke-coils 6 and 2 in series to ground 22. When high-frequency voltage is impressed upon the input-impedance 20 currents of corresponding-carrier frequency are set up in the external network between cathode-terminal Ma and ground 22. The effective impedance ofthe external network is that of the series-parallel circuit composed of the choke-coil 6 in series with the parallel resonant circuit between the terminals mb; substantially equal voltages of carrier frequency are present upon the parts m--b and d-m of inductance coil 9, the parallel circuit between terminals m-b operating as a pure resistance when tuned to the carrier frequency.

The high-frequency voltages impressed between cathode and diode-anodes |2, |3, are thus com posed of a vector sum of voltages for one diodeanode and a vector difference for the other diodeanode, as detailed in the U. S. patent previously referred to; in the series circuit from ground 22 to conductor the resultant rectified voltage can thus be made zero for a specific carrier frequency, positive for frequency deviations therefrom of the carrier frequency, and negative for frequency deviations of opposite algebraic sign.

The choke-coil 2 is many times larger in inductance value than the inductance of the part m-b of coil 9; choke-coil 2 is nevertheless substantially in shunt with terminals m-b, the reactance of condenser 46 for carrier frequency being substantially smaller than the reactance of coil 2, and the equivalent inductance across the terminals m-b is thus slightly smaller than the inductance of the part mb of coil 9. The junction-terminal m is normally the mid-inductance point upon the coil 9, however it will be understood that this position may be advantageously slightlymodified when no impedance-compensation is employed for compensating impedanceasymmetry of the network, introduced for example bycoil 2. The reactance of coil 2 is also substantially higher than the equivalent resistance at resonance of the parallel resonant circuit m-b and m-d-b, and the total alternating current as distinguished from a shunt-supply of alternating currents to a phase-shifting network, combinations of shunt and series supply, or other network couplings; said structure providing unilaterally-grounded output voltages, and providing sustained voltages to ground for a frequency-controlling grid of a thermionic generator ill]. a superheterodyne receiver, whenever a sustained difference occurs between balance-frequency of the demodulator and centre-frequency of the carrier wave. When the filter means of Fi 2 is employed with Fig. 1, the simple onetube demodulator structure provides dynamic stabilization of amplitude-envelope and regulation of average carrier amplitude employed, with the pro-amplifier. It will be evident that the demodulator of Fig. 1 provides economies of circuit elements with reference to Fig. 3.

While I have described and indicated several systems for carrying out my invention, it will be apparent to one skilled in the art that the invention disclosed herein is not limited to theparticular organizations shown and described, but that many modifications may be made without departing from the scope of my invention.

What is claimed is:

1. A frequency-discriminator for providing unilaterally-grounded output voltages responsive in magnitude and polarity to modulation of frequency of a high-frequency carrier wave, having a thermionic tube with a cathode, a first and a second diode-anode with said cathode, a third anode, and grid control means for controlling thermionic currents between said third anode and cathode, an input-impedance connected between said grid control means and said cathode, a unidirectional voltage source with positive terminal connected to said third anode and negative terminal connected to ground, a phase-shifting network connected between said cathode and i said diode-anodes including a common conductive connection between said cathode and each of said diode-anodes, and a junction-terminal of said conductive connection upon said network} a conductive ground connection of negligible impedance to one of said diode-anodes, a high-frequency choke-coil connected between said ground and said junction-terminal, and a high-frequency voltage neutralizing device including a conductive neutralizing-impedance coupled with said network for transferring opposing high-frequency voltages therefrom, and a conductive connection through said neutralizing-impedance to the ungrounded diode-anode.

2. In combination with the structure of claim 1, a pre-amplifier having a thermionic tube with grid control means and an output circuitcoupled with said input-impedance, an amplitude-modulation responsive control-impedance connected in series ,with said common conductive connection, having one terminal thereof connected to said junction-terminal and the other terminal thereof connected to theungrounded terminal of said choke-coil, and a transfer-filter connected to said control-impedance including a resistance-capacitance series connection with one terminal of the resistance thereof connected to said ground, and another terminal of said resistance thereof connected to said grid control means of said preamplifier, for transferring amplitude-modulation opposing pulses to said pre-amplifier grid control means to reduce undesired amplitude-modulation, when the rate of change of said carrier anllplitudes exceeds a predetermined minimum va ue.

1 ii 3. In combination with the structure of claim 1, a pre-amplifier having a thermionic tube with grid control means and anoutput circuit coupled with said input-impedance, an amplitude-modulation responsive control-impedance connected in series with said common conductive connection, having one terminal thereof connected to the ungrounded terminal of said choke c'oil and the other terminal thereof connected to'said junction-terminal, and a transfer-filter connected to said control-impedance including a second highfrequency choke-coil connected in series with a high-frequency by-pass condenser between said junction-terminal and said ground, one terminal of said second choke-coil being connected tosaid junction-terminal, and one terminal of-said bypass condenser being connected to said ground, and impedance means shunted across said bypass condenser connected with the grid control means of said pre-amplifier.

4. A frequency discriminator for providing unilaterally-grounded sustained output voltages responsive in magnitude and polarity to deviation of frequency of a high-frequency carrierwave, having a thermionic tube with a cathode, a first and a second diode-anode with said cathode, a third anode, andgrid control means between said cathode and third anode, resonance-circuit means responsive to said high-frequency carrier wave,

ground, and a high-frequency choke-coil connected between said ground and said cathodeconnected junction-terminal upon said resotrance-circuit means common to said conductive circuit connections. a

5. In combination with the structure of claim 4, a neutralizing-impedance for neutralizing high-frequency voltages superposed upon ,said output voltages, a conductive connection tothe ungr-ounded diode anode serially including said neutralizing-impedance, and, a coupling means for coupling said neutralizing-impedance with said resonance-circuit means.

6. A demodulator for demodulating frequency.- modulation from a high-frequency carrier wave, having a thermionic tube with a cathode, a first and a second diode-anodewith said cathode, a third anode, and grid control means for controllingthermionic currents between said third anode and cathode, a three-branch impedance network having a common jun-ction,,and having a first conductive impedance branch including a first inductance coil connected between said. junction and one of said diode-anodes, a second conductive impedance branch including a second inductance coil connected between said, junction and the other of said diode-ano-des, and a third conductive impedance branch connected between said junction and said cathode; energizing means for said network including a source of unidirectional voltage with positive terminal connected to, said third anode and negative terminal connected to ground, a conductive connection of negligible impedance from one of said diode-anodes to said ground, a high-frequency choke-coil connected from said ground to said common junction, and

ahigherreduency voltage balancin means for balancing-out: the highs-frequency voltage in an output circuitfor demodulated voltages, including a; conductive connection from the ungrou-nded dibdc-anode through abucking-coil inductively coupled with said first and second inductance coils '7, A frequency-demodulator for providing unilaterally-grounded sustained output voltages responsive in magnitude and polarity todeviation of frequency of a high frequency carrier wave, having a thermionic tube with a cathode, a first and a second diode-anode with said. cathdc, ,a third anode, and a control grid for controlling currents between said third anode and cathode, a source of unidirectional voltage with positive terminal connected to said third anode and negative terminal connected to ground, a series-parallel circuit including an inductance coil with terminals shunted by a condenser tuned to said carrier frequency, with a first choke-coil having one terminal. connected to said cathode and the other terminal connected to the mid-- inductance point upon said inductance coil, a diode-resistor shunted by capacitance connected between one of said diode-anodes and a terminal :oi said inductance coil, a second diode-resistor shuntedlbya second capacitance con-nected between the other diodeeanode: and the other terminal of. said inductance coil, a conductive connection of negligible impedance from one of said dlode-anodes-to said ground, a second choke- 7, selector means for selecting demodulated voltages, including a switch-terminal connected to the ungrounded terminal of the diode-resistor having a grounded terminal, and a switch-terminal connected to the other terminal of said second inductance coil, respectively for reception of amplitude-demodulated voltages or for frequency-demodulated voltages.

9. In combination with the structure of claim 7,, the circuit connection to said ground from the other terminal of said second inductance coil serially including a filter-resistance and a filtercondenser, said filter-condenser having a terminal thereof connected to said ground, for transferring the sustained voltages across said filtercondenser fromsaid demodulator, independent of frequency-modulation upon said carrier wave, and dependent as to magnitude and polarity upon the deviation of the centre-frequency of said carrier wave from the tuned frequency of said inductance coll shunted by said condenser.

10. In combination with the structure of claim 6, a second high-frequency choke-coil connected in series with a condenser from said ungrounded diode-anode to said common junction, for compensating impedance-asymmetry introduced by the first said choke-coil.

11, In combination with the structure of claim 1, a second high-frequency choke-coil connected in series with a condenser from said ungrounded diode-anode to said junction-terminal, for com pensating impedance-asymmetry introduced by the first said choke-coil.

12. In a frequency-discriminator for providin sustained unilaterally-grounded output voltages responsive in magnitude and polarity to frequency deviations of a high-frequency carrier Wave, having a thermionic tube with a cathode, a first and a second diode-anode with said cathode, a third anode, and a control grid for controlling currents from said third anode, a carrier frequency responsive network having a common conductive connection to said cathode from a junction-terminal thereon conductively connected to each of said diode-anodes, a conductive connection of negligible impedance to ground from one of said diodeanodes, and a high-frequency choke-coil connected between said ground and said junction-terminal, the filter dcvice for transferring voltages of modulation frequency from said network, including a control-resistance shunted by a contro1-capacitance and connected in series with said common conductive connection between said junctionterrninal and the ungrounded terminal of said choke-coil, a second high-frequency choke-coil connected to said junction-terminal and in series with a high-frequency by-pass condenser connected to said ground, and circuit connections from the terminals of said by-pass condenser for transferring amplitude-modulation responsive voltages.

13. In combination with the structure of claim 12, a pro-amplifier for said frequency-discriminator, having a thermionic tube with grid control means and an anode coupled with said control grid of said discriminator, a filter-resistance connected to said ground and in series through a filter-condenser to the ungrounded terminal of said by-pass condenser, and a connection from said grid control means of said pro-amplifier to said ground including a circuit through said filter-resistance. v I

14. In combination with the structure of claim 12, a pre-amplifier for said =frequency discriminator having a thermionic tube with grid control means and an anode coupled with said control grid of said discriminator, a filter-condenser con nected to said ground and in series through a filter-resistance to the ungrounded terminal of said by-pass condenser, and a connection from said grid control means of said pro-amplifier to said ground including a circuit through said. filter-resistance.

15. In a frequency discriminator having a thermionic tube with cathode, anode, grid control means between said cathode and anode for controlling anode-cathode currents, and a first and second diode-anode with said cathode, a bilateral phase controlling network with a conductive connection to said cathode, a unidirectional voltage source with positive terminal connected to said anode, a first voltage-rectifying means including a conductive circuit from one of said diode-anodes to said cathode through said network and through a first diode-resistor, and a second voltage-rectifying means including a conductive circuit from the other of said diodeanodes to said cathode through said network and through a second diode-resistor, the means for unilaterally energizing said network with steady anode-cathode currents, including a choke-coil means conductively connected between a diodeanode connected terminal. of one of said diodediode-resistor from said steady anode-cathode currents, and a conductive connection between the negative terminal of said source and said terminal of said diode resistor.

'16. A frequency discriminator having a thermionic tube with a cathode, an anode, and grid control means between said cathode and anode for controlling anode-cathode currents, a phasecontrolling network connected between said cathode and anode for controlling phase of voltages upon said network in response to changes of frequency impressed upon said grid control means, having an inductance coil means connected in series with a parallel resonator-circuit having one branch including a resonator-inductance coil, said network having secondary coil means inductively coupled with said resonatorinductance coil for transferring voltages therefrom, a voltage-rectifying means includuing a diode means serially connected with a dioderesistor means, a second voltage-rectifying means including a second diode means serially connected with a second diode-resistor means, and circuit connections between said voltage-rectifying means and said phase-controlling network, including a circuit through said secondary coil means.

17. A frequency demodulator having a thermionic tube with a cathode, an anode, a grid control means for controlling anode-cathode oury rents, a first diode-anode with said cathode and a second diode-anode with said cathode, a voltagecombining network for combining frequency responsive voltages, including a three-branch conductive impedance circuit having a common junction between a terminal of each of said conductive impedance branches, one of said branches including inductance-coil means connected from one of said diode-anodes to said junction, another of said branches including a second inductancecoil means connected from the other of said diode-anodes to said junction, and a third branch having a conductive impedance connected from said cathode to said junction, energizing-circuit means for energizing said network with carrier frequencies, said energizing-circuit means having mutual impedance with said network and including a source of unidirectional supply-voltage with positive terminal connected to said anode; a first diode-resistor for rectified voltage connected in one of said diode-anode connected branches, a second diode-resistor for rectified voltage connected in the other of said diode-anode connected branches, and conductive output-circuit connections for conductively transferring frequency demodulated voltages from said diode-resistors and opposing transfer of carrier frequency voltages from said network, including a circuit through inductance means coupled with said network.

18. The combination with a diode voltagerectifier having a cathode means, a diode-anode means with said cathode means, and the conductive circuit connections between said means serially including a diode-resistor for rectified voltages shunted by a condenser for smoothing said rectified voltages, and a conductive impedance means for impressing alternating voltages upon said diode-anode means, of a thermionic amplifier means including a second anode means with said cathode means, and grid control means between said second anode means and said cathode means, a source of unidirectional supply-voltage with positive terminal connected to said second anode means, and means for unilaterally energizing said amplifier means with unidirectional current from said source, including a junction-terminal consisting of the negative terminal of said source and the diode-anode connected terminal of said diode-resistor, and chokecoil means connected to said junction-terminal of said diode-resistor, by-passing said unidirectional current of said second anode means to said cathode means around said diode-resistor.

19. A frequency-demodulator having a thermionic tube with a cathode, an anode grid control means for controlling currents between said anode and cathode, and a diode means including a diodeanode with said cathode, a voltage phase-control circuit including a, parallel resonator-circuit connected in series with a choke-impedance means,

a circuit connection from said anode to said cathode for energizing said phase-control circuit with carrier frequencies, serially including said resonator-circuit, said choke-impedance means, and a diode-resistor means for rectified voltages a. capacitor means shunted across said dioderesistor means, and a conductive connection from said diode-anode to said diode-resistor means for providing rectified voltages responsive to frequen-cy upon said diode-resistor means.

, ing two inductance means mutually independent of each other, and a junction-terminal between said inductance means; impedance means including capacitance shunted across one of said inductance means for resonating said shunted inductance means with frequencies of said cathodeanode current and with energy transferred through the other of said inductance means, voltage-rectifying means including diode means serially connected with diode-impedance means having resistor means for said output-voltages, said voltage-rectifying means being connected across both of said serially connected inductance means for rectifying combined voltages therefrom, a common-terminal upon said resistor means in common with a negative terminal of said source of anode-supply voltage, a controlimpedance means connected from said junctionterminal to a junction between said diode-impedance means and said diode means, said controlimpedance means being capabl of passing currents of either polarity with equal impedance thereto, a second control-impedance means connected from said junction-terminal to said common-terminal, said second control-impedance means being capable of passing currents of either polarity with equal impedance thereto, and a circult through one of said inductance means and through said diode-impedance means for transferring frequency-demodulated voltages from said diode-impedance means, having a neutralizing-impedance means coupled with said one of said inductance means and with said diode-impedance means for cancelling alternating voltages of carrier frequency in said circuit.

21. A frequency discriminator for separating 15 output-voltages of modulation frequency from carrier frequency-modulated input-voltages, having a thermionic tube with a cathode, an anode, and grid control means between said anode and cathode for controlling anode-cathode currents, connections for carrying currents between said anode and cathode including a source of unidirectional anode-supply voltage with positive terminal connected to said anode, and including a path capable of serially carrying a cathodeanode alternating current with said frequencymodulated carrier frequency, having an endterminal thereof connected to said cathode, said path serially including two inductance means mutually independent of each other, and a junction-terminal between said inductance means; impedance means including capacitance shunted across one of said inductance means for resonating said shunted inductanc means with frequencies of said alternating current and by means of energy supplied through the other of said inductance means, voltage-rectifying means including diode means serially connected with diode-impedance means having resistor means for said output-voltages, said voltage-rectifying means being connected across both of said serially connected inductance means for rectifying combined voltages therefrom, a common-terminal upon said resistor means in common with a negative-voltage terminal of said source of anodesupply voltage, and a control-impedance means connected from said junction-terminal to a junction between said diode means and said diodeimpedance means, said control-impedance means' being capable of passing currents of either polarity with equal impedance thereto.

EDWARD H. LANGE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS

Images