DE1072659B - Mixed circuit arrangement - Google Patents

Description

GERMAN

The invention relates to a mixer circuit arrangement in which between the anode and Grid of a self-oscillating mixer tube, an oscillating circuit tuned to the oscillator frequency is arranged, which consists of a coil and two 5 there is preferably capacitive, parallel voltage dividers. The input vibrations are between two mutually balanced tapping points of both voltage dividers. The electrodes of the vibrating mixer tube are connected to points of the second voltage divider.

By balancing the divider impedances, which preferably consist of capacitors, it is easier to Way can be achieved that the oscillator oscillations from the feed points of the high-frequency signal oscillations be kept away.

In-depth investigations have shown, however, that there is still an effect on the high-frequency signal oscillations entry. These are namely amplified in the mixing tube and then occur in the Bridge circuit on. Known arrangements of this type are for these high frequency oscillations that are fed in again not adjusted, so that they can act back on the input circuit and there depending on Phase position either damping or undamping or impairment of the resonance curve can evoke.

In a mixer circuit arrangement, in which between the anode and the grid of a self-oscillating mixer tube, an oscillating circuit tuned to the oscillating frequency is arranged, consisting of a coil with a first and a second, preferably capacitive, voltage divider in parallel, the second voltage divider being made up of the series connection of a first, second , third and fourth impedance and the input oscillations are fed between the mutually balanced tapping points of both voltage dividers, while the anode of the tube is connected to the connection point of the first and second impedance and further electrodes of the tube are connected to other points of the 'second' voltage divider the above-mentioned disadvantages avoided, and a reaction of the amplified high-frequency oscillations in the tube on the input circuit is prevented if, according to the invention, the cathode of the tube R to the junction of the third impedance Z ₃ and the four th impedance Z ₄ and the grid is connected to the outer connection of the fourth impedance Z _{4 of} the second voltage divider consisting of four impedances Z ₁ , Z ₂ , Z ₃ and Z ₄ and when the signal oscillations between the connection point of the second impedance and the third impedance on the one hand and the tapping point of a fifth Impe mixed circuit arrangement

Applicant:

Philips Patentverwaltung GmbH,
Hamburg 1, Mönckebergstr. 7th

Wilfried Aschermann, Hamburg-Harburg,
has been named as the inventor

danz Z ₅ and a sixth impedance Z ₆ existing first voltage divider on the other hand, and if at least approximately

is {v = bridge ratio) .

The impedances are preferably formed by capacitors, the impedance value of which is known to be equal to the reciprocal of the product ω C of the capacitance C and the angular frequency ω .

In this way a so-called double bridge circuit is formed, both for the input oscillations in relation to the oscillator circuit as well as in relation to the amplified ones in the mixing tube and high frequency vibrations fed back to the arrangement is balanced so that the input circuit can be kept completely unaffected.

A self-oscillating mixer circuit arrangement with capacitive feedback is known in which the amplifier tube is connected to the taps of a voltage divider consisting of four capacitors to which the oscillator circuit, which is grounded on the one hand, is parallel. The following is achieved here ^: by means of small partial capacitances between the tube electrodes and the oscillating circuit, changes in the tube capacitance can have less of an effect on the tuning of the oscillator circuit; a bridge circuit is not formed.

A self-oscillating VHF mixer stage is also known in which the oscillator circuit has a voltage divider consisting of the series connection of four capacitors is parallel, the Anode and the grid between the first and the second and the third and the fourth capacitor are connected and the input oscillations between the second and the third capacitor and earth are fed. There is none

909 708/201

Bridge circuit in front, in particular the capacitors located on the outside of the oscillator circuit "are used only for direct current separation.

The invention is explained in more detail below with reference to the drawing, for example.

An oscillator circuit is formed by an inductance L, which can be changed for the purpose of tuning the oscillator frequency ω . You have a first voltage divider from the capacitors C ₅ and C _{6 in} parallel. The input oscillations are fed to the mixer circuit arrangement between the connection points of the capacitors C ₅ and C ₆ or C ₂ and C ₃ by a possibly tunable resonance circuit B.

The coil L is also a second voltage divider from the series connection of four capacitors C ₁ , C ₂ , C ₃ and C _{4 in} parallel. The anode of an amplifier tube R is connected to the connection point of the capacitors C ₁ and C ₂ , the cathode of which is connected to the connection point of the capacitors C ₃ and C ₄ . The grid, which is connected to the cathode via a bleeder resistor G , is connected to the external connection of the capacitor C ₄ . In the anode circuit of the tube R is the series connection of an intermediate frequency output filter F and a feed battery B.

If, as stated above, according to the invention the ratio ν of the impedances of the sub-branches is made the same, a double bridge results in which a complete decoupling of the input circuit B not only from the oscillator vibrations, but also from those occurring between the anode and cathode of the tube R. increased input vibrations occurs. -

When dimensioning the capacitances, it must be taken into account that the feedback voltage for the oscillator tube is determined _{by the ratio of the impedance Z 4 of} the capacitor C ₄ to the impedance Z ₂ + Z _{3 of} the series connection of the capacitors C ₂ and C _3.

Next, the anode of the tube should be on a tap of the oscillator circuit with as low a resistance as possible, because then even in the event of a misalignment - as it occurs e.g. B. by changes in the tube values can occur - due to the large impedance Z _{1 of} the capacitor C _1, only minor disruptive repercussions on the input circuit are obtained.

The total capacitance of both branches is determined together with the inductance L by the oscillator frequency ω .

. The division of the branches results in particular from the fact that the transmission of the input voltage to the grid-cathode section of the tube R through the impedance Z _{4 of} the capacitor C ₄ in relation to the impedance Z ₃ + Z ₄ + Z _{6 of} the series connection of the capacitors C. ₃ , C ₄ and C _{6 is} conditional. In particular, the impedance Z _{6 of} the capacitor C ₆ should therefore be kept small compared to the impedance Z _{4 of} the capacitor C ₄ . _{C 3} should also be noticeably larger than C ₄ . The branch of the capacitors C ₁ to C ₄ should therefore have a relatively high impedance; However, this is on the one hand by the tube capacities and the. Influence of the band filter F limited, it should also be taken into account that z. B. the grid-anode capacitance of the tube R over three voltage divider _{capacitances - C 2} , C ₃ and C ₄ , touches and so can interfere with the adjustment.

When using a high-resistance second voltage divider C ₁ , C ₂ , C ₃ , C ₄ , the connected impedances with lower values also result in ζ. B. the grid input impedance of the tube, interfering phase rotations.

Particularly at high frequencies, it is often difficult to achieve a sufficiently strong feedback to ensure reliable oscillation of the oscillator. Then the output impedance of the oscillator tube R should be as large as possible _{for the oscillator frequency, and the ratio of the alternating grid voltage (on the capacitor C 4} ) to the anode alternating voltage (on the series connection of the capacitors C ₂ and C ₃ ) should be high. For this purpose it is expedient that the impedance Z _{4 of} the capacitor C _{4 is} noticeably greater, preferably 2 to 4.5 or 10 times as great as the impedance Z _{3 of} the capacitor C ₃ . An even greater increase would, however, bring about a significant reduction in the anode impedance, since with C ₄ also C ₁ or with C ₃ also C ₂ must be changed in order to meet the above-mentioned adjustment condition for the bridge.

For this purpose of achieving a strong feedback, the bridge ratio ν should also be in the order of magnitude of 1, e.g. B. 0.5 to 2, preferably about 1, be.

The oscillator circuit can also be tuned by changing its partial capacitive impedance. It is important to ensure that the bridge adjustment is retained; this is most easily ensured when the tuning capacitor of the coil L is connected in parallel.

In principle, the earth point can be chosen arbitrarily in the circuit; the cathode of the tube R is expediently connected to earth potential.

The mixer circuit with a triode tube R has been explained and described. It goes without saying that, instead, a multi-lattice tube or a correspondingly acting other reinforcing element, e.g. B. a tip transistor or layer transistor, can be used in one of the known types of circuit. Since the properties of the reinforcement element are not essential for the invention and in particular the electrode impedances can be included in the impedances of the first voltage divider, all such modifications also belong to the invention.

Claims (9)

Patent claims: 1. Mixer circuit arrangement, in which between the anode and the grid of a self-oscillating mixer tube, a resonant circuit tuned to the oscillator frequency is arranged, consisting of a coil with a first and a second, preferably capacitive, voltage divider in parallel, the second voltage divider from the series connection of a first, second , third and fourth impedance and the input oscillations are fed between the mutually balanced tapping points of both voltage dividers, while the anode of the tube is connected to the connection point of the first and second impedance and further electrodes of the tube are connected to other points of the second voltage divider, characterized in that, that the cathode of the tube [R) to the junction of the third impedance Z ₃ (C ₃ ) and the fourth impedance Z ₄ (C ₄ ) and the grid to the external connection of the fourth impedance Z ₄ (C ₄ ) of the four impedances Z ₁ , Z ₂ , Z ₃ and Z ₄ existing two ite voltage divider is connected, that the signal oscillations between the connec- connection point of the second impedance (C ₂ ) and the third impedance (C ₃ ) on the one hand and the tapping point of the _{first voltage divider consisting of a fifth impedance Z 5} (C ₅ ) and a sixth impedance Z ₆ (C ₆ ) on the other hand, and that at least nearly is. ίο 2. Circuit arrangement according to claim 1, characterized in that the oscillating circuit can be tuned by changing the inductance (L). 3. Circuit arrangement according to claim 1 or 2, characterized in that the oscillating circuit can be tuned by changing a capacitor lying parallel to the inductance. 4. Circuit arrangement according to one of the preceding claims, characterized in that the sixth impedance (C ₆ ) of the first voltage divider is small compared to the fourth impedance (C ₄ ) of the second voltage divider. 5. Circuit arrangement according to one of the preceding claims, characterized in that the sixth impedance (C ₆ ) of the first voltage divider is low in relation to the series connection of the third and fourth impedance (C ₃ and C ₄ ) of the second voltage divider. 6. Circuit arrangement according to one of the preceding claims, characterized in that the values of the second and third impedance (C ₂ and C ₃ ) are relatively low compared to the first impedance (C ₁ ). 7. Circuit arrangement according to one of the preceding claims, characterized in that the fourth impedance (C ₄ ) is noticeably greater, preferably 2 to 4.5 times as large as the third impedance (C ₃ ). 8. Circuit arrangement according to one of the preceding claims, characterized in that the bridge ratio (v) is of the order of magnitude. 9. Circuit arrangement according to one of the preceding claims, characterized in that the intermediate frequency output filter (F) is connected between the anode and cathode of the tube (R) . Considered publications:
German Patent No. 739 095;
German interpretative document No. 1 006 904. 1 sheet of drawings © 909 708/201 12:59