GB1575198A

GB1575198A - Quarter-wave resonator

Info

Publication number: GB1575198A
Application number: GB9025/78A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1977-05-09
Filing date: 1978-03-07
Publication date: 1980-09-17
Also published as: DK99278A; NO139759B; SE415063B; FI65343B; NO771620L; NO139759C; FI65343C; DK144495B; SE7802482L; FI780851A7; DE2809363A1; DK144495C

Description

(54) QUARTER-WAVE RESONATOR (71) I, IVAN BACH, a Norwegian citizen, of 4990 S+ndeled, Norway, do hereby declare the invention, for which I pray that a patent may be granted to me, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to quarter-wave resonators of the coaxial type, and more particularly those in which the free end of the central conductor is temperature-compensated relative to its fixed end by means of a combination of members made of materials having different heat expansion coefficients.

In known resonators of this type, the central conductor consists of two telescopic tubes capable of passing within one another, one tube forming the free end of the central conductor and being connected at its outer end to compensating members. Upon expansion or contraction resulting from temperature variations, the outer end will remain fixed relative to the fixed end of the central conductor formed by the inner end of the second tube, such that the compensation itself works satisfactorily, but the sliding contact between the two tubes means that a variable contact resistance exists between the two tubes, which affects the stability of the resonator.

The object of this invention, therefore, is to provide a quarter-wave resonator of the type discussed above which does not have this disadvantage.

According to the present invention there is provided a coaxial quarter-wave resonator in which the free end of the central conductor is temperature-compensated relative to its fixed end by a combination of members made of materials having different heat expansion coefficients, wherein the free end of the central conductor has a section made flexible by transverse perforations thus enabling the central conductor to expand and contract in accordance with temperature variations between its fixed end and its free end while remaining in a fixed position.

The compensating members in an embodiment of the present invention can advantageously consist of a central bar of a steel alloy having an expansion coefficient of 0.0000115, one end of which is connected by screw threads to the fixed end of the central conductor, its other end being connected to one end of a surrounding coaxial tube of an aluminium alloy having an expansion coefficient of 0.000023. The other end of said aluminium tube may be connected to one end of a surrounding coaxial tube of a steel alloy having an expansion coefficient of 0.0000115, the other end of said steel tube being connected to the free end of the central conductor.

For coarse adjustment of the resonator's frequency, the central conductor, as known per se, can consist of two telescopic tubes which can pass within one another, where, according to an embodiment of the invention, one end of one of the tubes is fixed, and the other end supports a conical ferrule clamp fitting connecting it to the second tube, the second tube forming the free end of the central conductor and having the flexible perforated- section.

An example of one embodiment of the invention will be described below with referenceto the accompanying drawings.

Figure 1 is an axial cross-section through an embodiment of a quarter-wave resonator made in accordance with the invention Figure 2 is a detail of Fig. 1 showing the flexible pattern in the free end of the central conductor.

The embodiment illustrated shows a quarter-wave resonator of the coaxial type for UHF and SHF, with a closed outer conductor which consists of a container 15 and a cover plate 10, made of aluminium, for example. An inner central conductor 4 consists of two telescopically-slidable tubes, the end of one tube, which is fixed in the resonator, being centrally fastened in the cover plate 10, which has a central, threaded bore to receive a central, steel alloy rod 1 having a heat expansion coefficient of 0.0000115. The outer end of the rod 1 is connected to the outer end of a surrounding coaxial aluminium alloy tube 2 which has a heat expansion coefficient of 0.000023. The other end of the aluminium tube is con nected to the inner end of a surrounding coaxial steel alloy tube 3 which has a heat expansion coefficient of 0.0000115, and whose outer end in turn is connected to the free end of the central conductor 4. Owing to the material properties of the compensation members 1, 2 and 3, the central conductor has a fixed length L within a very wide temperature range. To enable the free end of the central conductor to maintain the desired fixed distance L from the cover plate 10 within the desired large temperature range, the outer portion of the central conductor is provided with a pattern 14 of transverse perforations which make it flexible, i.e., the patterned section can be compressed and expand again without any change in resistance over the perforated section. The second tube in the central conductor 4 which is provided with the flexible pattern is connected to the first tube by means of a conical ferrule clamp fitting 13 for coarse adjustment of the resonant frequency of the resonator. The rod 1 makes possible the fine adjustment of the resonator, in that its upper end is connected with members 5, 6, 7 and 9, which can be rotated and locked in place.

As indicated on Fig. 1, an oscillator or amplifier 8 is connected to the interior of the resonator by means of a coupling loop 12 which extends through an opening 11 in the cover plate 10.

WHAT I CLAIM IS:- 1. A coaxial quarter-wave resonator in which the free end of the central conductor is temperature-compensated relative to its fixed end by a combination of members made of materials having different heat expansion coefficients, wherein the free end of the central conductor has a section made flexible by transverse perforations thus enabling the central conductor to expand and contract in accordance with temperature variations between its fixed end and its free end while remaining in a fixed position.

2. A quarter-wave resonator according to Claim 1, wherein the compensating members consist of a central bar of a steel alloy having an expansion coefficient of 0.0000115, one end of which is connected by screw threads to the fixed end of the central conductor, its other end being connected to one end of a surrounding coaxial tube of an aluminium alloy having an expansion coefficient of 0.000023, the other end of said aluminium tube being connected to one end of a surrounding coaxial tube of a steel alloy having an expansion coefficient of 0.0000115, the other end of the steel tube being connected to the free end of the central conductor.

3. A quarter-wave resonator according to Claim 1 or Claim 2, wherein the central conductor consists of two telescopic tubes which can pass within one another, one end of one tube being fixed, the other end carrying a conical ferrule clamp fitting connecting it to the second tube, the second tube forming the free end of the central conductor and having the flexible perforated section.

4. A quarter-wave resonator substantially as hereinbefore described with reference to and as illustrated by the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. nected to the inner end of a surrounding coaxial steel alloy tube 3 which has a heat expansion coefficient of 0.0000115, and whose outer end in turn is connected to the free end of the central conductor 4. Owing to the material properties of the compensation members 1, 2 and 3, the central conductor has a fixed length L within a very wide temperature range. To enable the free end of the central conductor to maintain the desired fixed distance L from the cover plate 10 within the desired large temperature range, the outer portion of the central conductor is provided with a pattern 14 of transverse perforations which make it flexible, i.e., the patterned section can be compressed and expand again without any change in resistance over the perforated section. The second tube in the central conductor 4 which is provided with the flexible pattern is connected to the first tube by means of a conical ferrule clamp fitting 13 for coarse adjustment of the resonant frequency of the resonator. The rod 1 makes possible the fine adjustment of the resonator, in that its upper end is connected with members 5, 6, 7 and 9, which can be rotated and locked in place. As indicated on Fig. 1, an oscillator or amplifier 8 is connected to the interior of the resonator by means of a coupling loop 12 which extends through an opening 11 in the cover plate 10. WHAT I CLAIM IS:-

1. A coaxial quarter-wave resonator in which the free end of the central conductor is temperature-compensated relative to its fixed end by a combination of members made of materials having different heat expansion coefficients, wherein the free end of the central conductor has a section made flexible by transverse perforations thus enabling the central conductor to expand and contract in accordance with temperature variations between its fixed end and its free end while remaining in a fixed position.