US2611093A - Mixing circuit - Google Patents

Description

p 1952 J. M. 1.. JANSSEN 2,611,093

MIXING CIRCUIT Filed Feb. 14, 1947 J. M. L. JANSSEN \NVENTOR AGE NT Patented Sept. 16, 1952 2,611,093 Y MIXING, CIRCUIT Johannes Marinus Lodevicus Janssen, 'Eindhoven, Netherlands, assignor to Hartford National :Bank and Trust Company, Hartford, Conn, as

trustee Application February 14, 1947, Serial No. 728,711 In the Netherlands September 2, 19.4.4

Claims. (01. 2511-36) 1 This invention relates to a mixing circuit comprising adischarge tube which contains at least a cathode, a control grid, 'a screen grid and an output electrode and whose control grid is supplied with one of the signals to be mixed.

According to the invention, the other signal, which is constitutedby periodical short pulses, is fed to the output electrode which has such a bias voltage that it has only current passing through it during the occurrence of the pulses, the desired beat frequency being obtained from the circuit of the output electrode.

The .circuitaccording to the invention has the advantage'of making it possible to obtain output voltages whose frequency equals the sum or the difference of the frequency fed to the control grid and of any harmonic of the pulse frequency fed to the output electrode, the conversion mutual conductance being very high and practically independent of the order of the harmonic chosen. Thus, for example, the use of the circuit according to the invention even makes it'possible to derive a considerable output voltage whose frequency equals the difference of the frequency supplied to the control grid and of the hundredth harmonic of the pulse frequency.

The circuit according to the invention can therefore be used with advantage for the development of a large Zoneof accurately adjustable frequencies ranging for example between zero and 20 M cycles/sec. In addition, as an alternative the circuit-according to the invention can be used for frequency measurements, the measurement being undertaken by the ascertainment of the difference frequency between the frequency to be measured and themost proximate harmonic of a well known frequency.

In order that the invention may be clearly understood and readily carried into effect, it will now'be described more fully with reference to the accompanying drawing, in which two embodiments'are shown, Fig. 1 being the schematic diagram of a first preferred embodiment of the invention and Fig. Zbeihg the schematic diagram of the secondembodiment.

Referring to Fig. 1, .a discharge tube 1 comprises a cathode 2, a control grid 3,a screen grid 4 having a positive bias applied thereto, a suppressor grid 5 connected to the cathode and a plate-like output electrode 6. The control grid 3 and the cathode 2 have arranged between them a source of voltage 1 which supplies one of the two signals to be mixed. The other signal, which is constituted by periodical short pulses, is supplied by a source of voltage 8 arranged between the output electrode 6 and the cathode 2. An output voltage of the desired beat frequency is obtained from an oscillatory .circuit 9 tuned to this frequency and also included in the circuit of the output electrode.

By means of a source of direct-voltage in the output electrode '6 is supplied with a low negative bias voltage .in such manner that this electrode has only current passing through itduring the occurrence of the pulses supplied by the source of voltage 8. It is now found that if the circuit 9 is correctly tuned, said circuit being for this purpose preferably tunable throughout a large zone, an output voltage can be secured whose frequency equals "the sum or the difference of the frequency of the source I and of any harmonic of the pulse frequency supplied by the source 8.

The frequency of the source I is preferably made variable throughout a band whose width is at least equal to halfthe fundamental frequency of the source 8 so that the constant use of a higher harmonic of the source 8 for mixin permits of a continuous band of frequencies known with great accuracy being obtained.

taking frequency measurements, the frequencies to be measured being supplied to the control grid 3 and the circuit of the output electrode s including in addition to a source of voltageB a low pass Ifilter which is constituted by an inductance H and a condenser [:2 and whichis .shuntedby a leak resistance l3 so far as direct currents are concerned. The limit frequency of this filter is approximately equal to half the .fundamental frequency of the source.8, so that at the output terminals i4 and IE only the difference frequency between the frequency to be measured .and the most proximate harmonic of the pulse frequency supplied by the sourcea occurs. This difference frequency can be measured accurately by means of a calibrated low frequency oscillator. By a coarse frequency measurement, the harmonic of the source 8 which is to be added to the difierence frequency measured for obtaining the frequency to be measured is then ascertained.

WhatI claim is: V

l. A circuit-arrangement-forproducing an output voltage, whose value is a function of the frequency relation existing between an oscillatory wave and one component in the harmonic spectrum of periodic voltage impulses, comprising an electron discharge tube provided with a cathode, a grid and an anode, a grid-cathode circuit for said tube, an anode-cathode circuit for said tube, an impedance network connected in the anode cathode circuit of said tube, means to apply an oscillatory wave to the grid-cathode circuit of said tube, and means to apply periodic voltage impulses to said anode-cathode circuit to render said tube conductive solely during the occurrence of said impulses, said impulses having a duration which is short with respect to the interval between successive impulses, said network having a frequency response characteristic whose frequency width does not exceed the fundamental frequency of said impulses by which there is yielded an output voltage whose value is a function of the frequency relation existing between said wave and the most proximate component in said spectrum. Y

2. A circuit-arrangement for producing an output voltage, whose value is a function of the frequency relation existing between an oscillatory wave and the most proximate component in the harmonic spectrum of periodic voltage impulses, comprising an electron discharge tube provided with a cathode, a grid and an anode, a gridcathode circuit for said tube, an anode-cathode circuit for said tube, a low-pass filter having its input connected in the anode-cathode circuit of said tube, means to apply an oscillatory Wave to the grid-cathode circuit of said tube, and means to apply periodic positive voltage impulses having a predetermined repetition rate to said anode-cathode circuit to render said tube conductive solely during the occurrence of said im pulses, said impulses having a duration which is short relative to the interval between successive impulses, said filter having a band-pass characteristic whose frequency width does not exceed approximately half the rate of said impulses whereby said filter yields an output voltage whose value is a function of the frequency relation existing between said wave and the most proximate component in said spectrum.

3. A circuit-arrangement for producing an output voltage, whose value is a function of the frequency relation existing between an oscillatory Wave and the most proximate component in the harmonic spectrum of periodic voltage impulses, comprising an electron discharge tube provided with a cathode, a grid and an anode, a gridcathode circuit for said tube, an anode-cathode circuit for said tube, a low-pass filter having its input connected in theanode-cathode circuit of said tube, means to apply an oscillatory wave to the grid-cathode circuit of said tube, means to apply a bias potential to said anode-cathode circuit to maintain said tube normally non-conductive, and means to apply periodic voltage impulses having a predetermined periodicity to said anode-cathode circuit to render said tube conductive solely during the occurrence of said impulses, said impulses having a width which is short relative to the interval between successive impulses, said filter having a band-pass characteristic Whose frequency width is less than approximately half the periodicity of said impulses whereby said filter yields an output voltage whose value is a function of the frequency relation existing between said wave and the most proximate component in said spectrum.

4. A circuit-arrangement for producing an output voltage, whose value is a function of a frequency relation existing between an oscillatory wave and the most proximate component in the harmonic spectrum of periodic voltage impulses, comprising an electron discharge tube provided with a cathode, a grid and an anode, an oscillatory wave source connected between said grid and said cathode, a low-pass filter connected between said anode and said cathode, a periodic voltage impulse source interposed between said anode and said filter to render said tube conductive solely during the occurrence of said impulses, said impulse source producing impulses at a predetermined rate and having a duration which is short relative to the interval between successive impulses, said filter having a band-pass characteristic whose frequency width is substantially equal to one-half the rate of said impulses.

5. A circuit-arrangement for producing an output voltage, whose value is a function of a frequency relation existing between an oscillatory wave and the most proximate component in the harmonic spectrum of periodic voltage impulses; comprising an electron discharge tube provided with a cathode, a grid and an anode, an oscillatory wave source connected between said grid and said cathode, a low-pass filter connected between said anode and said cathode, a bias supply interposed between said cathode and said filter to maintain said tube normally non-conductive, a periodic voltage impulse source interposed between said anode and said filter to render said tube conductive solely during the occurrence of said impulses, said impulse source producing impulses having a predetermined periodicity and a duration which is short relative to the interval between successive impulses, said filter having a band-pass characteristic whose frequency width is substantially equal to one-half the periodicity of said impulses.

JOHANNES MARIN'US LODEVICUS JANSSEN.

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

UNITED STATES PATENTS Number Name Date 1,564,627 Round Dec. 8, 1925 1,912,234 Willoughby May 30, 1933 2,173,164 Hansell Sept. 19, 1939 2,246,958 Strutt et al June 24, 1941 2,258,877 Barber Oct. 14, 1941 2,416,367 Young July 30, 1942 2,401,945 Linder June 11, 1946 2,408,821 Stearns Oct. 3, 1946 2,408,858 Keiser Oct. 8, 1946 2,432,180 'I'ourshou Dec. 9, 1947 2,445,584 Ramo July 20, 1948 2,504,636 Bradley Apr. 13, 1950 OTHER REFERENCES Article by G. Grammer, Q. S. T., June 1938, pages 21 and 24, 98 and 100,

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