GB2067039A - An active frame aerial stage - Google Patents
An active frame aerial stage Download PDFInfo
- Publication number
- GB2067039A GB2067039A GB8038849A GB8038849A GB2067039A GB 2067039 A GB2067039 A GB 2067039A GB 8038849 A GB8038849 A GB 8038849A GB 8038849 A GB8038849 A GB 8038849A GB 2067039 A GB2067039 A GB 2067039A
- Authority
- GB
- United Kingdom
- Prior art keywords
- frame aerial
- active frame
- stage
- output circuit
- frequency
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
- 230000005669 field effect Effects 0.000 claims description 4
- 230000035945 sensitivity Effects 0.000 abstract description 2
- 238000010276 construction Methods 0.000 abstract 1
- 230000000694 effects Effects 0.000 description 2
- 238000000034 method Methods 0.000 description 2
- 230000003321 amplification Effects 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 230000001419 dependent effect Effects 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 238000003199 nucleic acid amplification method Methods 0.000 description 1
- 230000005855 radiation Effects 0.000 description 1
- 238000004804 winding Methods 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03F—AMPLIFIERS
- H03F3/00—Amplifiers with only discharge tubes or only semiconductor devices as amplifying elements
- H03F3/189—High-frequency amplifiers, e.g. radio frequency amplifiers
- H03F3/19—High-frequency amplifiers, e.g. radio frequency amplifiers with semiconductor devices only
- H03F3/193—High-frequency amplifiers, e.g. radio frequency amplifiers with semiconductor devices only with field-effect devices
- H03F3/1935—High-frequency amplifiers, e.g. radio frequency amplifiers with semiconductor devices only with field-effect devices with junction-FET devices
Landscapes
- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Amplifiers (AREA)
- Variable-Direction Aerials And Aerial Arrays (AREA)
Abstract
The frequency-proportional sensitivity of an active frame aerial stage is compensated for by the construction of the amplifier part thereof as a cascaded emitter follower arrangement with a frequency proportional feedback impedance in the emitter branch. <IMAGE>
Description
SPECIFICATION
An active frame aerial stage
The present invention relates to an active frame aerial stage.
In frame aerials, there is a linear relationship between the signal frequency and the ratio of open-circuit output voltage to field strength. In very wide band receiving operation, this leads to output voltages increasing towards high frequencies, which in turn can lead to problems in respect of the intermodulation resistance of an aerial amplifier and wide band receiver inputs.
A known method keeping the ratio of output voltage to field strength constant in active frame aerial stages consists in letting the frame aerial operate into a comparatively low impedance amplifier input and to withdraw from it its frequency-constant short-circuit current and then to amplify this (DE-OS 27 48 076). However, the short-circuit current flowing in the frame aerial of this known arrangement generates a strong secondary field. When several such aerials are set up in close proximity to one another, this secondary field acts negatively on the entire arrangement through mutual desensitising of the individual frame aerials. Beyond that, such an amplifier arrangement is susceptible to signal distortions in consequence of the non-linearities of the characteristics of the amplifier elements.
The invention is based on the task of providing an active frame aerial stage, which builds up no disturbing secondary field and which over a wide band produces a ratio, substantially independent of frequency, of the output voltage to the incoming field strength with high linearity of the amplification at the same time without penalties having to be incurred in respect of the inherent noise of the amplifier.
According to the present invention, there is now provided an active frame aerial stage comprising a frame aerial and provided with an amplifier comprising a plurality of cascaded amplifying elements and having an input circuit, which includes input means of each of the amplifying elements and which is connected to the frame aerial, an output circuit including a load impedance element connected to output means of only the last of the amplifying elements, and a feedback impedance element, which is connected in a circuit path common to the input circuit and to the output circuit and the impedance of which above a given signal frequency is substantially proportional to frequency.
For the highest demands on the linearity of the aerial amplifiers, it is favourable for example to cascade several transistors connected in emitter follower configuration. A similar circuit in connection with a rod aerial is described for example in the DE-PS 2021 331. However, in the case of a frame aerial, where the voltage induced in the frame rises with the signal frequency, special measures must beyond that be taken for compensation of this frequency dependence in order to attain a constant ratio of useful output voltage to field strength.
Embodiments of the present invention will now be more particularly described by way of example with reference to the accompanying drawing, the single figure of which shows a frame aerial stage embodying the present invention.
Referring now to the drawing, there is shown a frame aerial stage comprising a frame aerial F receiving a signal at field strength H and providing an output voltage
U1 to the input circuit of an amplifier which in the illustrated embodiment comprises three cascaded transistors, of which the first two are connected in emitter follower configuration, the input means of each transistor, namely the base-emitter path thereof, being included in the input circuit which further includes a feedback impedance element in the form of an inductor L carrying an alternating current 1D and providing a feedback voltage U,.The output of the amplifier is derived from a load impedance element R connected to output means of the amplifier, the output means being provided by the collector-emitter path of the last transistor in the cascade and being included in an output circuit, a portion of which in addition to the load impedance element R includes the feedback impedance element L in a circuit path common to the input circuit and which is connected with the input of a receiver amplifier to apply thereto a signal voltage U2 developed across the load impedance element R by the alternating current 1D therethrough.
On connection of the transistor amplifier to the frame aerial, the emitter follower cascade operates with high linearity on the feedback impedance element L, which being an inductor has an impedance which is substantially proportional to signal frequency above a frequency given by any resistance thereof not being negligible by comparison with the reactance of its winding. The strong feedback has the effect that the voltage U, at the inductor becomes almost equal to the input voltage U, of the amplifier, so that U,~U, and
U2 U,jwL-l, = joL R wherein X denotes the angular frequency of the input signal radiation H.
Due to the frequency-dependent feedback impedance xL, the frequency independence of the ratio ID/H and thereby of the ratio of the output voltage to the field U2/H is attained.
The employment of field effect transistors is particularly advantageous by reason of the particularly low noise of these elements. The connection corresponding to the emitter in bipolar transistors is frequently designated as source in the case of field effect transistors.
The corresponding applies to the collector as collecting electrode in the bipolar transistor and corresponding drain in the field effect transistor.
Applying the known technique of valvetransistor equivalents, the amplifier may alternatively comprise cascaded valves connected in cathode follower configuration, the output means of the amplifier in this case being provided by the anode-cathode path of the last valve of the cascade.
Important possibilities of use of the described embodiments result from the fact that the frame is practically free of current and thereby generates no secondary field.
Therefore, several frame aerials can be operated as closely adjoining as desired without any mutual interference or any reduction in the useful voltage. This circumstance can be used for the formation of a desired directional effect with very small aerial spacing in receiving operation (supergain) or for improvement of the sensitivity by simple connection together at the output side.
Likewise, it is possible to feed several amplifiers from one frame aerial since they absorb only extremely small currents.
Claims (6)
1. An active frame aerial stage comprising a frame aerial and provided with an amplifier comprising a plurality of cascaded amplifying elements and having an output circuit, which includes input means of each of the amplifying elements and which is connected to the frame aerial, an output circuit including a load impedance element connected to output means of only the last of the amplifying elements, and a feedback impedance element, which is connected in a circuit path common to the input circuit and to the output circuit and the impedance of which above a given signal frequency is substantially proportional to frequency.
2. An active frame aerial stage as claimed in claim 1, wherein each of the amplifying elements comprises a respective transistor connected in emitter follower configuration, the output circuit including the collector-emitter path of the last transistor.
3. An active frame aerial stage as claimed in claim 2, wherein at least the first of the cascaded transistors is a field effect transistor.
4. An active frame aerial stage as claimed in claim 2, wherein each of the amplifying element comprises a respective valve connected in cathode follower configuration, the output circuit including the anode-cathode path of the last valve.
5. An active frame aerial stage as claimed in any one of the preceding claims, wherein the feedback impedance element comprises an inductor.
6. An active frame aerial stage substantially as hereinbefore described with reference to and as shown in the accompanying drawing.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE19792952160 DE2952160A1 (en) | 1979-12-22 | 1979-12-22 | ACTIVE FRAME ANTENNA |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB2067039A true GB2067039A (en) | 1981-07-15 |
| GB2067039B GB2067039B (en) | 1984-05-31 |
Family
ID=6089540
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB8038849A Expired GB2067039B (en) | 1979-12-22 | 1980-12-04 | Active frame aerial stage |
Country Status (2)
| Country | Link |
|---|---|
| DE (1) | DE2952160A1 (en) |
| GB (1) | GB2067039B (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2310320A (en) * | 1996-02-14 | 1997-08-20 | Edward Charles Forster | Active loop antenna with constant output/frequency characteristic |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE1282744B (en) * | 1965-07-02 | 1968-11-14 | Csf | Receiving loop antenna |
| DE2166898C2 (en) * | 1971-03-31 | 1982-08-26 | Gerhard Prof. Dr.-Ing. 8012 Ottobrunn Flachenecker | Active Unipol receiving antenna for reception in two frequency ranges separated by a frequency gap |
| DE2554829C3 (en) * | 1975-12-05 | 1985-01-24 | Flachenecker, Gerhard, Prof. Dr.-Ing., 8012 Ottobrunn | Active receiving antenna with a negative feedback impedance |
| DE2748076C2 (en) * | 1977-10-26 | 1982-06-09 | Rohde & Schwarz GmbH & Co KG, 8000 München | Loop antenna connected to an amplifier |
-
1979
- 1979-12-22 DE DE19792952160 patent/DE2952160A1/en active Granted
-
1980
- 1980-12-04 GB GB8038849A patent/GB2067039B/en not_active Expired
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2310320A (en) * | 1996-02-14 | 1997-08-20 | Edward Charles Forster | Active loop antenna with constant output/frequency characteristic |
| GB2310320B (en) * | 1996-02-14 | 2000-06-07 | Edward Charles Forster | Active loop antenna |
Also Published As
| Publication number | Publication date |
|---|---|
| DE2952160A1 (en) | 1981-06-25 |
| GB2067039B (en) | 1984-05-31 |
| DE2952160C2 (en) | 1989-09-28 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| 746 | Register noted 'licences of right' (sect. 46/1977) | ||
| 732 | Registration of transactions, instruments or events in the register (sect. 32/1977) | ||
| PCNP | Patent ceased through non-payment of renewal fee |
Effective date: 19921204 |