DE3212073C2 - Tunable high-frequency generator with almost temperature-independent frequency - Google Patents

Abstract

The high-frequency generator contains a variometer with a rotatable short-circuit winding and an oscillating circuit. Coil carrier and rotor consist of a dimensionally stable insulating material with the same thermal expansion, for example made of glass or special steatite. The shielding housing and cover are optionally made of another metallized insulating material with the same thermal expansion as one another, for example of laminated plastic. The rectangular lids form the reference edges for assembling the individual parts manufactured with a rough dimension tolerance. During the manufacturing process, the individual parts are positioned using gauges and differences in dimensions are compensated for by gluing and soldering joints and the interposition of spacers. In the adjustment process, the center frequency shifted into the upper tolerance range is shifted into the lower tolerance range by connecting small capacitors with negative temperature coefficients, the temperature coefficient of the frequency being adjusted to zero. The technical progress consists in a cheaper production and adjustment process.

Description

The invention is based on a tunable high-frequency generator according to the preamble of Claim 1,

In the high frequency technology! ¹ ; Infinitely variable LC generators are often used, the tuning elements of which consist of so-called. B. are described in the "Pocket Book of High Frequency Technology" by Meinke and Gundlach, 1956, page 28.

Their function is based on a rotatable short-circuit winding within one against the actuating shaft 45 ° inclined solenoid. In one end position, the short-circuit turn is perpendicular to the coil turns, is thus decoupled and realizes the maximum coil inductance. Is in the other end position the short-circuit winding is twisted in parallel to the coil windings and causes the strong damping the minimum coil inductance.

These variometers have no electrical contacts and allow stable oscillation circuits to be set up with high repetition accuracy of the frequency in the event of temperature changes.

Its temperature coefficient TKl = AL / L / Ut is at. The known constructions with ceramic bobbins KER 221 DIN 40685 are determined in a first approximation by the TKcder coil capacitance and is TK _L = 20 to 30 - ΙΟ " ⁶ / *.

A tried and tested version in volume production is explained in the description of DE-PS 12 02 358 and figuratively represented. Costly manufacturing processes with tight grinding tolerances were still used for this ceramic moldings required to make the coil with an inclined base at the angle of inclination 45 ° fasten, and to comply with the electrical tolerances according to the state of the art in volume production.

In an improved all-ceramic design according to DE-GM 17 52 885, a more rational one was already used Volume production described by using a solenoid without an inclined base, with the required Inclination of the coil against the actuating shaft due to an angled support surface of the shielding housing was achieved. In this version, however, narrow grinding tolerances for the door were still the ceramic ones Adhere to individual parts.

A further simplification was later described in DE-PS 12 02 358, in the case of the coil and shielding housing were designed as smooth hollow cylinders and the coil is glued into the shielding cylinder with a 45 ° incline became. However, this all-ceramic design still required tight grinding tolerances for the Fit of the individual parts and to comply with the electrical tolerances.

The invention specified in claim 1 has the object of producing the tunable Simplify high-frequency generator from a structural point of view and close-tolerance, ground ceramic parts to avoid.

To the mass production of the short-circuit variometer in the interest of a decisive reduction in price without To largely rationalize the loss of quality of the electrical tolerances, important components become the formerly had to consist of polished ceramics, now of uncut ceramics or others Insulating materials produced, the geometric dimensions of which tolerated sufficiently tight without additional processing are, according to the invention coil carrier and rotor of the short-circuit variometer from the same form-

stable insulating material with the same thermal expansion, z. B. made of glass or in a known manner from special steatite, that the shielding housing and its cover optionally made of another metallized insulating material with the same thermal expansion, for example made of laminate, the rectangular The housing cover forms the reference and contact edges for assembling the high-frequency generator and at the same time serve to attach the circuit board to the electrical circuit that also all items are manufactured with coarse dimensional tolerance without additional fine machining, and that mechanically and elekf5 Trically conductive connections consist either of conductive adhesive or, in a known manner, of soldering.

According to the invention, the manufacturing process for the generators has also been largely simplified. the

H Grinding tolerance in an earlier version, which is described in the description and figurative representation of the

p DE-PS 12 02 358 is mentioned, was z. B. at the outer diameter of the coil + 0.05-0 mm. The improved

|| Execution according to DE-GM 17 52 885 still contained the same tolerance requirement, but here it was

'' Possibility to remove individual parts comparatively quickly during assembly or repairs.

Exchange %.

% In a later version according to DE-PS 12 02 358, the coil and shielding housing were already smooth

Hollow cylinders made of ceramic, but their tolerances were still + 0.05 - 0 mm for the outer diameter.

fi knife of the coil and + 0.05 - 0 mm for the inner diameter of the shielding cylinder. They could only get through

% Grinding of the ceramic parts are adhered to.

% According to the invention, it is now possible to allow much larger dimensional tolerances by using the coarse

ψ: Dimensional tolerance manufactured individual parts are positioned by mechanical gauges for assembly,

'4 with geometric differences in dimensions due to adhesive or soldered joints and the interposition of spacers

■ -ν are bridged, and that the resulting electrical tolerances during electrical adjustment

be balanced.

The method of calibrating the temperature influence on high-frequency generators according to the invention has also been decisively improved over the known state of the art, as described in the article by E. Roske "About a temperature-compensated ceramic variometer" in STEMAG-Nachrichten, Issue 27, Dec. 1959 .
^: The task of compensating the temperature influence of the ... Frequency (TK /) is known to be solved if

¹

For the temperature coefficient of the inductance including the electrical circuit TKl ~ 20 to 30 · \ Q ~ ⁶ IK , a compensation capacitance was required with the opposite temperature coefficient TKc = -20 to -30 · IQ- ⁶ IK.

So far, the compensation capacity has been divided into two groups, a "coarse" and a "fine compensation". Both groups consisted of Kersmik small capacitors according to DIN 41 920 Type I, the capacitance and TKc of which had to be measured individually. Since the electrical tolerances of the variometer were correspondingly small due to the narrow dimensional tolerances of the ground ceramic parts, it was possible to put together appropriate groups from a stock of measured capacitors whose capacitance met the tolerance requirement of the tuning curve and whose TC _{C met} the requirement of temperature compensation.

The main advantage of the high-frequency generator according to the invention is that only one group of compensation capacitors with measured capacitance and measured TKc is used. Both values are set so that the base frequency of the generator is at the upper tolerance limit and the 7X / of the generator is at the lower tolerance limit. The fine compensation is then carried out according to the invention by connecting unmeasured individual capacitors with a small capacitance and a strongly negative TKc, e.g. from a supply of commercially available small ceramic capacitors from N 750 DIN 41 920, whose capacitance is in the range from 1.0 to 8.2 pF is graded according to the tolerance series E 12.

In addition, in the high-frequency generator according to the invention, the non-linearity of the temperature dependency of the frequency is compensated, which, as is known, comes about through non-linear properties of the switching elements. For this purpose, ceramic small capacitors according to DIN 41 920 Type II are used, for example with a dielectric constant e _r s 1000, which mainly consist of barium titanate and because of their non-linear temperature dependence and their high dielectric loss factor are not suitable for vibration capacitors, but only for coupling, screening , among others

The proportion of these non-linear capacitors is only about 0.1% of the total capacitance, so that the Loss factor can be neglected. The curved curve of the temperature dependence of the Capacitance is suitable to compensate for the curved course of the curve of the temperature dependence of the frequency, if the condition is fulfilled that the individual values fulfill the condition at each temperature:

Ar_ -IAC
7o ~ ~~ C ~

/ ₀ = center frequency of the generator.

The invention is to be explained using an exemplary embodiment.

1 shows a high-frequency generator schematically in a sectional side view and FIG. 2 shows a schematic front view. The metallized surfaces are thick in section. Here 1 a smooth solenoid with the cut outer winding. The coil is made of glass or ceramic with the rough tolerance of the outer diameter ± 0.6 mm max Shielding housing 2 glued in, which is, for example, cylindrical with a rough tolerance of the inner

diameter of ± 0.6 mm max., and that for example made of laminate with an externally applied Metallization can consist of copper foil. The dimensional differences between solenoid 1 and shielding housing 2 are compensated for by wedge-shaped spacers 3 and 4, if necessary. the Actuating shaft 5 carries a disk 6 on which a tuning ring 7 is attached, which is covered with copper on the outside or silver is coated and serves as a rotatable short-circuit winding. The shaft 5, the disc 6 and the Tuning ring 7 are made of an insulating material that has the same thermal expansion as coil 1, for example made of glass or ceramic. 8 is the actuating pin of the shaft 5, which is in a not shown here Thrust bearing is stored.

The shielding housing is completed with two rectangular cover plates 9 and 10, which are made of an insulating material exist, which has the same thermal expansion as the shielding housing, for example from Laminate with copper lamination.

The electrical oscillating circuit is housed on the printed circuit board 11, which is made of an insulating material consists of the same thermal expansion as the cover plates 9 and 10, for example made of laminate with Copper lamination.

The oscillating circuit, not shown here, consists of active and passive components and fulfills the Space 12 above the printed circuit board 11.

During assembly, two edges of the cover plate 9 which are at right angles to one another are turned into a teaching inserted, which at the same time fixes the shielding housing 2. Then the junction will be between 2 and 9 optionally soldered or coated with conductive adhesive. An additional jig fixes the coil 1 in the correct position less than 45 °, the coil being clamped with wedge-shaped spacers 3 and 4 if necessary. These places receive a drop of epoxy resin adhesive. Then the adhesive points harden in the teaching at an elevated temperature of, for example, 80 ° C. After inserting the shaft 5 with the rotor parts 6, 7 and 8 a further teaching for fixing the cover plate 10 is placed and proceeded accordingly.

The finished variometer and the printed circuit board 11 with the oscillating circuit 12 are in electrical replicas pre-checked and then connected with conductive adhesive at the support points between 9, 10 and 11 or soldered.

The method of balancing the generators according to the invention is explained with reference to FIGS. 3, 4 and 5.
Fig. 3 shows the oscillation circuit, consisting of the variometer L, the compensated oscillation capacity Cl, Cl 'and the fine compensation C2. The conventional oscillating circuit is not shown.
Fig. 4 shows the "tolerance tube" of the tuning range of the frequency / angle of rotation a.

Fig. 5 shows the tolerance field of the frequency change Af = f ₂ -f \ as a function of the temperature change At = I ₂ - ζ ,.

The procedure is now that the capacitance of the compensated resonant circuit capacitors Cl + Cl 'so is dimensioned that the setting curve 1 in Fig. 4 runs at the top of the "tolerance tube". The 7Kc of capacitors Cl + Cl 'is set so that the temperature dependence of the frequency, for example, curve 1 in Fig. 5 corresponds.

Now the capacitor C2 is switched on, the maximum capacity of which is such that the Tuning range according to curve 2 in Fig. 4 sets, but that at the same time the temperature dependence of the frequency after 2 in Fig. 5 is reached.

AO The curve 2 in FIG. 5 shows the typical curvature of the frequency as it is generated by non-linear switching elements. According to the invention, the curvature is compensated for by the partial capacitance Cl 'in FIG. 3 consists of a capacitor with a non-linear temperature variation of the capacitance, for example according to Type II DIN 41 920.

In a numerical example from practice, the mean inductance is L = 1.5 μH, the mean frequency / ₀ = 5.4 MHz with a tuning range / _me : / "," = 1.15: 1 = 5.75: 5 MHz. The resonant circuit capacity consists of the following components:

Ci = 670 pF TKc = - 28 XQ ^ IK
Cl '= 5 pF DK (ε) s 1000 Type II DIN 41 290
Cl = 1 pF N750 DIN 41 920.

A temperature compensation of the frequency has thus been achieved, which is in the dashed tolerance field of Fig. 5 and has the amount:

TK - ^{Δ /} (^ -Z ₁ ) _ 1080 _,. _λα -β _{/ κ}

5.375 ■ 10 ^s ■ 40

The non-linear capacitor Cl 'preferably has a maximum capacity at the temperature / ^ according to Fig. 5, in order to bring about a linearization which results in curve 3 in the example given.

For this purpose 2 sheets of drawings

Claims (2)

Patent claims: 1. Tunable high-frequency generator with almost temperature-independent frequency, consisting of a shielded short-circuit variometer and an electrical oscillating circuit, with coil carrier (1) and rotor (6) of the shielded short-circuit variometer made of the same dimensionally stable insulating material exist, e.g. B. made of glass or special steatite, characterized in that the shielding housing and its lids are made of another, metallized insulating material, e.g. B. made of laminate, wherein the rectangular housing cover the reference and contact edges for assembling the high-frequency generator form and at the same time serve to attach the circuit board to the electrical circuit, ίο that all items are also manufactured with rough dimensional tolerance without additional fine machining, that mechanical and electrically conductive connections are made of conductive adhesive or of soldering, that the resonant circuit capacitors (Cl, Cl ') are dimensioned according to their capacity so that the center frequency of the high-frequency generator is upper scatter range of the tolerance field and is shifted by the optional connection of a small capacitance in the direction of lower frequency within the tolerance field that the resonant circuit capacitors (Cl, Cl ") are dimensioned according to their temperature coefficient (JKr) so that the resulting temperature coefficient of the frequency (JKj) lies in the lower scatter of the tolerance field and by adding a small capacitance (C2) with a strongly negative temperature coefficient in the direction of temperature coefficient of frequency (JKj) is shifted approximately zero and that the resonant circuit capacitors have a capacitor (Cl ¹ ) with non-linear dependence the capacitance of the temperature, the direction of which is the same and the magnitude of which is twice as large as the non-linear temperature coefficient of the frequency. 2. Verijhren for producing a tunable high frequency generator according to claim 1, characterized characterized in that the items manufactured with rough dimensional tolerance by mechanical gauges for the Assembly are positioned, with geometric differences in dimensions due to adhesive and soldering joints and be bridged by interposing spacers.