US2582683A

US2582683A - Superheterodyne radio receiver

Info

Publication number: US2582683A
Application number: US144305A
Authority: US
Inventors: Dammers Bernhardus Gerhardus
Original assignee: Hartford National Bank and Trust Co
Current assignee: Hartford National Bank and Trust Co
Priority date: 1949-02-16
Filing date: 1950-02-15
Publication date: 1952-01-15
Anticipated expiration: 1969-01-15
Also published as: NL80423C; FR1017229A; GB668498A; NL144910B

Description

Jan. 15, 1952 DAMMERS 2,582,683

SUPERHETERODYNE RADIO RECEIVER Filed Feb. 15 1950 INVENTOR. BERNHARDUS GERHARD'US DAMMERS AG ENT Patented Jan. 15, 1952 Bqrnha'rhus fGerhar'dus Dam'mers, JEin'dhoven, Netherlands, assignor to Hartford National Bank and Trust Compa trustee hpelieatiofii bruary 15, 1950, Serial No; 144,305

In the Netherlands F bruary 16,1949

The present invention relates to a 'suo dyne receiverja nd more particularl y to *a mixin'g circuit arrangement wherein both I the local I oscillations and the input signals are applied between the cathode' and the grid of the mixin'g tube.

For frequency transformation of ultra-short waves a diode is "generally used. This, however, has the disadvantage that 'an additional tube is required for generating the local oscillations.

It is known to use a triode as an oscillatormodulatorf but 'thes'e known circuit-arrangementsare, as a rule, unsuitable for frequency transformation of ultra-short "waves. H

'1he principle object of the present invention to provide a mixing circuit-arrangement for the reception of ultra-short waves, of the type referred to in the preamble, in which stable oscillator operation is ensured and in which a high conversion conductance is achieved.

Another object of the invention is to provide a mixing circuit wherein local oscillations are not radiated by the antenna and in which a favourable signal-to-noise ratio is achieved.

Further objects of the invention will appear from the following description.

According to the invention, the mixing circuit includes a discharge tube having a cathode, a control grid and an anode. An impedance network, from which the intermediate-frequency oscillations are derived, is coupled between the anode and the grid. Connected in series with this impedance network is an impedance element across which the local oscillations occur and which is inductively coupled with an impedance connected between the cathode'and the grid, so that the local oscillations are produced in the tube itself and are applied, together with the input signals, between the cathode and the grid of the tube.

The grid is preferably connected to a point of constant potential, such as ground, and acts as a static screen between the cathode and the anode. It is to be noted that such so-called grounded-grid arrangements for amplifying ultra-high-frequency oscillations are often used when it is desired to amplify a comparatively wide frequency band. In mixing circuits it is also known to connect the cathode, through an impedance across which the local oscillations occur, to a point of constant potential and to supply the signal voltage to the grid. In such an arrangement, however, the output circuit is generally connected between the anode and the point of constant potential, so that the grid does not constitute a static screen beween the output circuit and the in ut circuit at the -'tiib e'-' a d-tne arrangement is not well suited for frequency transformation of ultra-short waves. Q

According to the invention, there is interposed between the point'of constantpotential, towhi'ch the grid is "connected, and the anode arteries connection of a circuit tuned to "theiocal-qs" i lator frequency and the impedancefid" the intermediate-frequency os'c'illati a rived-i The inductance of the said o cut ductively coupled with aninducto'n' one-amd- -oi which is connected to the cathodepf the tube and the-'other end of whichisc'onnected,: through a condenser, to the point of constant potential. The input signal is :fed to "a tapping on the iwducto r, preferably to f'a 'c'enter tapping. I

In order that the invention may be more clearly understood and readily carried into effect, it will now be described more fully with reference to the accompanying drawing, in which one embodiment thereof is shown by way of-example.

Referring now to the drawing, the antenna circuit inductance l is coupled with the inductance of a first circuit 2, which is tuned to the desired signal frequency. The high-frequency oscillations developed across this circuit are applied through filters 3 and 4, the purpose of which will be explained hereinafter, and part of a feed-back coil 6, to a cathode 8 of a triode l. A grid 9 of triode I is grounded, with respect to high-frequency oscillations, through a parallelconnection II of a resistance and a condenser. An anode I0 is connected, through a circuit l2, which is tuned to the intermediate frequency, and a circuit I4 which is tuned to the oscillator frequency, to the positive terminal of the supply. The circuit I2 is coupled with a circuit l3, which is also tuned to the intermediate frequency, and from which the intermediate-frequency oscilla tions are derived for further amplification and detection.

As a triode, it is advantageous to employ a so called disc-seal tube or a grounded-grid triode, in which the grid constitutes an eifective static screen between the anode and the cathode and is grounded for this purpose. In the latter, the grid is provided with a number of supply leads in order to reduce the inductance.

The inductance of circuit I 4 is inductively coupled to coil 6 so that the triode operates as an oscillator and local oscillations occur across the circuit l4. If the antenna circuit is connected to the centre of coil 6 and a condenser I5 is connected between the lower end of this coil and ground, and if condenser I5 is chosen to be approximately equal to the grid-cathode capacity, local oscillations will not occur across the antenna circuit 2 and troublesome radiation will not take place. A resistance 11, connected in parallel with condenser I5, is chosen to be approximately equal to the input resistance of the tube. A parallel-connection of a resistance and a capacity coupled between the tap on coil 6 and ground serves to apply a suitable positive bias to the cathode 8. This resistance is traversed by the cathode current. An inductance l6, interposed between the tap on coil 6 and circuit 6, serves to prevent the high-frequency signal currents from flowing to ground. The filters 3 and 4 included in the lead between the antenna circuit-fiend the tap on coil 6 serve to keep the antenna circuit isolated from the intermediatefrequency oscillations and the local oscillator oscillations respectively. The filter 4 thus amplie V fies the effect of the balanced bridge-circuit formed by the two parts of coil 6, condenser l5 and the grid-cathode capacity of the tube.

While I have described my invention in a specific use thereof and in a specific embodiment, I do not wish to be limited thereto, for obvious modifications will occur to those skilled in the art without departing from the spirit and scope of 4 said intermediate frequency wave and said sec-- and wave and coupled in series between said anode and ground potential, said second impedance network including an inductance, means to derive said intermediate frequency wave from said first impedance network, a third impedance network having a low impedance at the frequencies of said first and second waves interposed between said control grid and ground potential, a tapped inductive element having one end thereof coupled to said cathode and having the other end thereof coupled to ground potential, said inductive element and said second impedance network being inductively coupled to apply said second wave to said control grid-cathode circuit in positive feedback relationship, and means to apply said first wave to the tap on said inductive element.

2. A mixing circuit arrangement, as set forth in claim 1, further including a resistance capacitance parallel network interposed between said other end of said inductance element and ground potential to apply a positive bias to said cathode.

BERNHARDUS GERHARDUS DAMMERS.

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

UNITED STATES PATENTS Mountjoy Aug. 4, 1936