US1940519A - Frequency converting radioreceiver - Google Patents

Description

Dec. 19, 1933. R WYCKQFF 1,940,519

FREQUENCY CONVERTING RADiQRECEIVEF Filed Dec. 19, 1928 Patented Dec. 19,1933

1,940,519" W Z ooivvaa'rme naniov FREQUENCY E V B' a Ralph D. l/Vyckoff, Ponca 'City, Okla.

Application December-19,- 1928 U salient; 327,157

2 Claims. '(oi. 250-20);

My invention relates to methods and apparatus used for frequency conversion, particularly as applied to radio receiving equipment; and has for its object the simplification ofthe apparatus together with improvement in the operating char.-

acteristics of the receiver: 1' r r It is well known that frequencyconverters as quency converter, an intermediate radio-ire quency amplifier tuned'to a fixed frequency and a demodulator or detectorsfrom the output circuits of which the audi0-frequency signals are.

derived. The frequency conver'ter', composed of the oscillator and modulator components, has for its purpose the changingnf the incoming' oscilla- 'tions to the frequency for. which the intermediate radio-frequency amplifier is tuned, the signal is there amplified at the converted frequency, de-

modulated in the. following detector unit and ?9:audio-frequency components of the signal ob tained.

As usually constructed the frequency converter requires the use of one three-electrode thermionic tube as an oscillator and another in the modu- 3f1ator unit often called the first-detector unit, or if preferred the oscillator and modulator functions may be combined in a single unit using a single three-electrode thermionic tube. use of a single three-electrode thermionic tube as lia combination unitit is necessary to use some harmonic component of the oscillator-frequency to beat against the signahirequency in order that the signal-frequency circuits and the oscillator circuits may be independently adjusted and func l5; tion independently. I

Instead of using the usual three-electrode tube I employ a four-electrode thermionic tube in the frequency converter unit. It is then possible to use the so-called dynatron characteristic of the tube to obtain oscillations of any desired frequency and simultaneously, by use of a fourth electrode of the tube, to modulate the oscillations so obtained by any other desired frequency and thus obtain in the output circuits the com- 'ibination or beat frequency desired. Such opera- In the tion of the four-electrode tube as a combination oscillatonmodulator may be obtained which is equivalent to the use of two three-electrode tubes inthat the adjustments of the component parts of the circuit maybe made independent of one another and operationat a harmonic 'of the cillator frequency is unnecessary. I r Itis .also a well known fact that in ther usu al type of superheterodyne receiver the oscillator has aJcertain amount of coupling with the-antennal eircuitscausing the antenna to radiate energyatthe oscillator frequency or harmonics of it, a condition which causes interference with other nearby receivers. In order to eliminate suchradiation from the receiver it has been the practice. to couple theireceiver to the antenna circuits through an additional three-electrode In the accompanying drawing, Figure 1 shows 1 the fundamental circuit whereby the dynatron characteristic of any three-electrode thermionic tube may be used to produce oscillations of any desired frequency.

duce the same result and in addition shows the use of the fourth electrode to modulate the oscil lations so derived, at any desired frequency, thereby obtaining the desired frequency conversion. Figure 8'shows the fundamental circuits. involved in the use of the four-electrode thermionic tube as the frequency converter unit in a superheterodyne type of receiver.

Referring to Figure l, 1 is the cathode, 2 is the grid and Sis the anode of a thermionic tube. Unit 5 is a tuned circuit in the anode circuit of the tube. It the anode potential and grid potential are properly adjustectsustained oscillations may be produced in the anode circuit the frequency of; which may be controlled by adjust-. ment of the electrical constants of the anode circuit.

Referring to Figure 2, 4 is an additional grid element and 7 is an additional tuned circuit added to the circuit of Figure 1 and may be placed in the circuit of anode 3 as shown or in the circuit Figure 2 shows the same a method applied to afour-electrode tube to proof grid 2. If as mentioned above, the potentials of grid 2 and anode 3 are properly adjusted, sustained oscillations will be produced in the circuit of anode 3 which oscillations may be modulated at any desired frequency by a means of generator 6 mother source of alternating potential suitably connected to grid 4. A tuned circuit or other selective filter 7 may then be introduced in the circuit of anode 3 or grid 2 and the resultant combination or beat-frequency may be obtained at the terminals of '7. If the electrical constants of circuit '7 are properly selected no parasitic oscillations at the frequency of circuit '7 will be generated, even though it is placed in the circuit of anode3. I I 7 Referring to Figure 3, I have shown the fundamental circuit whereby the frequency converter shown in Figure 2 is applied to the well known 'superheterodyne type of radio receiver. 'Unit 6 is the coupling device that serves to apply the received signal frequency obtained from antenna system 10,.which may be any of the usual type or collecting devices, to thegrid 4.. Oscillations in anode circuitv 5 are thereby modulated bythe signal-frequency. and .the derived or beat-frequency selected by filter 7 passed on to amplifier 8 which is the usual type of intermediate-fre- V quenc'y amplifier, thence to the demodulator 9 I 5 may be adjusted to produce any desired beat from which the-'audio-frequency components of the received signal are derived. Oscillator circuit frequency thus the signal frequency may be converted to any frequency for which the filter and amplifier units? and 8 are adjusted. The signalfrequency circuit 6 may be independently adjusted to obtain maximum input to grid 4. The grid 4'may be given a suitable negative bias by means of cells. 11 or other suitable source of biasing potential thereby reducing the damping eifect of grid 4 on the tuned circuit 6 to a negligible amount. In addition, if circuit 7 is placed in the circuit of anode 3, the grid 2 maybe so constructed as to efiectively shield grid 4 from potential variations of anode 3, thereby preventing if internal electrode coupling between the oscillating. circuit 5 and the antenna circuits 6 and 10 radiation from the receiver, and improves the operating characteristics of the receiver.

What I claim is:

1. Frequency conversion apparatus 7 comprising a'ne'gat ive resistance thermionic device comprising. essentially 'a cathode, an inner control-grid, an intermediate or shield-grid, and an anode, an

input coupling device in circuit between said inner grid and cathode, means for maintaining a suitable biasing potential on said inner grid, means for maintaining saidintermediate or shield-grid at a positive potential with respect to all other elements of the thermionic tube, means for maintaining the .anode at a positive potential intermediate to said shield-grid and cathode, said anode potential being of such value relative to the shield-grid that the anode exhibits negative, resistance characteristics, an oscillatory circuit in said anode circuit, an ouput filter device in said anode circuit, whereby sustained oscillations produced in the anode circuit are modulated at the frequency impressed on the input grid and the resultant heterodyne frequency is available at the terminals of said output filter.

2. Frequency conversion apparatus as described in claim 1, wherein the input device of the grid circuit and the anode oscillatory circuit are tunable, permitting the input device to accommodate any input frequency and by adjustment of anode oscillatory circuit, maintaining the derived heterodyne frequency atany desired value, or at the frequency of the output filter device.

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