505,079

PATENT SPECIFICATION

Application Date: Oct. 4, 1937. No. 26796/37

Complete Specification Left: Sept. 13, 1938.

Complete Specification Accepted: May 4, 1939.

----------------------

PROVISIONAL SPECIFICATION

Improvements in or relating to Wireless Transmission or Receiving Apparatus

I, ALAN DOWER BLUMLEIN, of 37, The Ridings, Ealing, London, W.5, A British subject, do hereby declare the nature of this invention to be as follows:

This invention relates to wireless transmitting or receiving apparatus and has particular but not exclusive reference to transmitting or receiving apparatus operating on very short wave lengths.

In a television transmitting system it is know that the maximum distance from the transmitting station at which reception can be ensure is about 25 to 50 miles and for this reason it may be desirable to erect another transmitting station at a distance of about 50 to 100 miles from the first transmitting station and to transmit the same programmes from both transmitting stations in order that the programmes may be received over a much wider area. With such an arrangement using the same wavelength at each station it is possible that a receiver disposed substantially midway of the two transmitting stations will receive both transmissions simultaneously but that one transmission will be phase-displaced with respect to the other transmission due to the necessary time of transmission from one station to the other, and consequently two pictures will be reproduced in the receiver, one picture being displaced with respect to the other. This produces an undesirable effect in the reproduction. Of course the two stations may be given separate wavelengths but in covering a country with short wave broadcast stations, sufficient wavelengths may not be available. The closely adjacent stations may have different wavelengths but there may still be interference between slightly more distant stations which owing to shortage of available wavelengths, must operate on the same wavelength. Alternatively a common wavelength may be used for two transmissions from the same station for purposes hereinafter referred to. In addition it may be desirable to transmit two different programmes on the same carrier wave length from the two transmitters, in which case it is desirable to provide means at a receiver whereby the receiver may selectively receive one or other of the transmissions. Apart from television transmitting systems it might also, in some cases, be desirable in short wave transmission, owing to the fact that the short wave range is somewhat limited, to transmit different programmes or intelligence on the same wave length from two remotely situated transmitting stations or to transmit from closely adjacent stations on the same wave length television or other signals and in such a manner that it is possible for a receiver selectively to receive the two transmissions.

The present invention has for its object to provide a transmitting system in which two carrier wave transmissions of substantially the same wave length can be transmitted whilst at the same time enabling the transmissions to be selectively received or simultaneously received and separately reproduced at a receiver. The invention also provides a receiver for receiving such a transmission.

According to one feature of the invention a carrier wave transmitting system is provided in which two sets of signals on substantially the same carrier wave are transmitted the plane of polarisation of one set of signals being substantially at right angles to the plane of polarisation of the other set of signals. With such a form of transmission the aerial of one transmitter for example being vertical and the aerial of the other transmitter being horizontal, it is possible at a receiver to receive selectively either of the transmission, or, in some cases, both transmissions, as will hereinafter be more particularly referred to. This may be effected by providing the receiver with two aerials, one arranged in the plane of polarisation of the signals of one transmitter and the other arranged in the plane of polarisation of the signals from the other transmitter and to provide switching means whereby one or other of the aerials can be connected to the receiver at will by the operator or to provide the receiver with an aerial which is mounted in a suitable manner as, for example, on a pivot, whereby the aerial may be rotated at will by the operator to cause the aerial to lie in the plane of polarisation of the signals from one or other of the transmitters. Where it is desired to receive two sets of signals from different transmitters on the same carrier wave it will in this case be necessary to provide two aerials, one arranged in the plane of polarisation of the signals from the other transmitter, the two sets of signals received on the aerials being fed, for example, to two similar amplifiers and subsequently being fed to separate reproducing devices such as cathode ray tubes in the case of television reception, the purpose of such an arrangement being hereinafter referred to.

It is known, particularly with short wave transmission, that the plane of polarisation of the waves remain substantially constant throughout its path. Consequently by transmitting two sets of signals of substantially the same wave length from aerials so arranged that the planes of polarisation of the transmitted signals are substantially at right angles to one another, the signals received on an aerial disposed in the plane of polarisation of one set of signals will so predominate over the signals picked up by the same aerial from the other station that these latter signals will be substantially ineffective at the receiver.

The invention is particularly applicable to the transmission of television signals where it may be necessary to provide repeater stations for transmitting the same programme and in this case the receiving apparatus will, as aforesaid, be provided with two aerials, preferably dipoles which can be selectively connected to the receiver, or a single adjustable aerial, whereby the receiver may receive signals from one station substantially to the exclusion of signals from the other station. If the two stations transmit different programmes on the same wave length then selective reception of either station can be ensured by providing a single aerial orientated to receive signals from a desire station, or by providing an adjustably mounted aerial or two aerials with switching means as aforesaid.

If one station is more powerful than the other, the latter station will transmit its signals in which ever plane of polarisation transmits signals more efficiently.

For the transmission of television signals in two colours it is possible, according to the invention to provide two aerials at the transmitter, the plane of polarisation of one aerial being substantially at right angles to that of the other aerial and to feed to the aerials signals obtained on scanning an object through suitable colour filters and to provide at the receiver two aerials, one arranged in the plane of polarisation of one set of signals and the other in the plane of polarisation of the other set of signals, these two sets of signals being subsequently fed to two reproducing devices, such as cathode ray tubes, the fluorescent screens of which reproduce individually the two sets of signals and the fluorescent colour of the screens corresponding to the filters at the transmitter. The two pictures produced at the receiver are viewed simultaneously and super-imposed for which purpose the two cathode ray tubes may be arranged in such a manner that the fluorescent screens are substantially at right angles to one another and arranged at 45 between the two tubes is a half silvered mirror, that is to say a mirror which reflects substantially half of the light incident on it so that on viewing the mirror the two pictures will be super imposed and viewed simultaneously.

A somewhat similar form of transmitting arrangement may be employed for the transmission of pictures in stereoscopic form and in this case two sets of signals of the same object, but displaced an amount corresponding to the inter-ocular distance, will be transmitted from the two aerials and at the receiver two cathode ray tubes are provided for receiving the sets of signals, the images reproduced on the fluorescent screens being viewed through suitable lenses whereby the two images are super-imposed to produce a stereoscopic effect. The stereoscopic reproduction of images is also known in which two displaced images in different colours are viewed through suitable colour filters and the present invention can also be applied to such a form of stereoscopic reproduction.

Although the invention is particularly applicable for transmissions of intelligence on short wave lengths, since the planes of polarisation of the waves retain their polarisation to a maximum extent, it is however also possible to employ the invention for the transmission of intelligence employing signals of lower frequencies in accordance with the invention although the planes of polarisation of such lower frequency signals are not maintained to the same degree as signals of very high frequency.

Slight shifts of polarisation which occur at short wavelengths may be corrected by slightly tilting the receiving aerial so as to cut out the unwanted signal.

Dated this 4th day of October, 1937

F. W. Cackett

Chartered Patent Agent

COMPLETE SPECIFICATION

Improvements in or relating to Wireless Transmission or Receiving Apparatus

I, ALAN DOWER BLUMLEIN, of 37, The Ridings, Ealing, London, W.5, A British subject, do hereby declare the nature of this invention and in what manner the same is to be performed, to be particularly described and ascertained in and by the following statement:

This invention relates to wireless transmitting or receiving apparatus and has particular but not exclusive reference to transmitting or receiving apparatus operating on very short wave lengths.

In a television transmitting system it is know that the maximum distance from the transmitting station at which reception can be ensure is about 25 to 50 miles and for this reason it may be desirable to erect another transmitting station at a distance of about 50 to 100 miles from the first transmitting station and to transmit the same programmes from both transmitting stations in order that the programmes may be received over a much wider area. With such an arrangement using the same wavelength at each station it is possible that a receiver disposed substantially midway of the two transmitting stations will receive both transmissions simultaneously but that one transmission will be phase-displaced with respect to the other transmission due to the necessary time of transmission from one station to the other, and consequently two pictures will be reproduced in the receiver, one picture being displaced with respect to the other. This produces an undesirable effect in the reproduction. Of course the two stations may be given separate wavelengths but in covering a country with short wave broadcast stations, sufficient wavelengths may not be available. The closely adjacent stations may have different wavelengths but there may still be interference between slightly more distant stations which owing to shortage of available wavelengths, must operate on the same wavelength. Alternatively a common wavelength may be used for two transmissions from the same station for purposes hereinafter referred to. In addition it may be desirable to transmit two different programmes on the same carrier wave length from the two transmitters, in which case it is desirable to provide means at a receiver whereby the receiver may selectively receive one or other of the transmissions. Apart from television transmitting systems it might also, in some cases, be desirable in short wave transmission, owing to the fact that the short wave range is somewhat limited, to transmit different programmes or intelligence on the same wave length from two remotely situated transmitting stations or to transmit from closely adjacent stations on the same wave length television or other signals and in such a manner that it is possible for a receiver selectively to receive the two transmissions.

The present invention has for its object to provide a transmitting system in which two carrier wave transmissions of substantially the same wave length can be transmitted whilst at the same time enabling the transmissions to be selectively received or simultaneously received and separately reproduced at a receiver. The invention also provides a receiver for receiving such a transmission.

According to one feature of the invention, there is provided a wireless transmission system comprising means for transmitting two modulated carriers each having substantially the same wavelength and the plane of polarisation of one carrier being substantially at right angles to the plane of polarisation of the other carrier so that a suitable receiver can selectively receive one or other of the transmissions.

According to another feature of the invention, there is provided a wireless receiver designed to receive signals from said transmission system comprising a dipole aerial which is arranged to be rotatable so that any one of the two modulated carriers can be selectively received.

Accordingly to a further feature of the invention, there is provided a television system comprising a transmission system having means for transmitted two modulated carriers, each having substantially the same wavelength and the plane of polarisation of one carrier being substantially at right angles to the plane of polarisation of the other carrier, the signals for modulating said carriers being obtained by scanning the picture to be transmitted through suitable colour filters so that with a suitable receiving system the reproduced picture has to be a certain degree the same colouring as the picture transmitted.

A television receiver designed to receive signals from the said television transmission system comprises means for separately receiving the two modulated carriers and passing them through separate channels to two reproducing devices which are adapted to produce pictures the colour of each being substantially the same as that of the corresponding colour filter at the transmitter, it being so arranged that the two pictures are superimposed and viewed simultaneously so that a coloured reproduction is obtained.

According to another feature, there is provided a television system comprising a transmission system having means for transmitting two modulated carriers, each having substantially the same wavelength and the plane of polarisation of one carrier being substantially at right angles to the plane of polarisation of the other carrier, the signal for modulating said carriers being obtained in such a manner so that a suitable receiver stereoscopic reproduction is obtained.

A television receiver designed to receive signals from the above-mentioned television system comprises means for separately receiving the modulated carriers and passing them through separate channels to two reproducing devices which are so arranged that on being viewed through suitable lenses the two images are superimposed to produce a stereoscopic effect.

According to a further feature of the invention, there is provided a wireless transmission system comprising means for transmitting two modulated carriers each having substantially the same wavelength and the plane of polarisation of one carrier being substantially at right angles to the plane of polarisation of the other carrier, the modulating signals comprising audio signals which are obtained by microphones which are so arranged that with a suitable receiver binaural reproduction is obtained.

A wireless receiver designed to receive signals from the above-mentioned wireless transmission system comprises means for separately receiving the modulated carriers and passing them through separate channels to separate sound reproducing devices which are so arranged as to give binaural reproduction.

A transmission system according to one embodiment of the invention may have, for example, the aerial of one transmitter vertical and the aerial of the other transmitter, horizontal.

It is possible at a receiver to receive selectively either of the transmission, as will hereinafter be more particularly referred to. This may be effected by providing the receiver with two aerials, one arranged in the plane of polarisation of the signals of one transmitter and the other arranged in the plane of polarisation of the signals from the other transmitter and to provide switching means whereby one or other of the aerials can be connected to the receiver at will by the operator or to provide the receiver with an aerial which is mounted in a suitable manner as, for example, on a pivot, whereby the aerial may be rotated at will by the operator to cause the aerial to lie in the plane of polarisation of the signals from one or other of the transmitters. Where it is desired to receive two sets of signals from different transmitters on the same carrier wave it will in this case be necessary to provide two aerials, one arranged in the plane of polarisation of the signals from one transmitter and the other in the plane of polarisation of the signals from the other transmitter, the two sets of signals received on the aerials being fed, for example, to two similar amplifiers and subsequently being fed to separate reproducing devices such as cathode ray tubes in the case of television reception, the purpose of such an arrangement being hereinafter referred to.

It is known, particularly with short wave transmission, that the plane of polarisation of the waves remains substantially constant throughout its path. Consequently by transmitting two sets of signals of substantially the same wavelength from aerials so arranged that the planes of polarisation of the transmitted signals are substantially at right angles to one another, the signals received on an aerial disposed in the plane of polarisation of one set of signals will so predominate over the signals picked up by the same aerial from the other station that these latter signals will be substantially ineffective at the receiver.

The invention is particularly applicable to the transmission of television signals where it may be necessary to provide repeater stations for transmitting the same programme and in this case the receiving apparatus will, as aforesaid, be provided with two aerials, preferably dipoles which can be selectively connected to the receiver or a single adjustable aerial, whereby the receiver may receive signals from one station substantially to the exclusion of signals from the other station. If the two stations transmit different programmes on the same wavelength then selective reception of either station can be ensure by providing a single aerial orientated to receive signals from a desired station, or by providing an adjustably mounted aerial or two aerials with switching means as aforesaid.

If one station is more powerful than the other, the latter station will transmit its signals in whichever plane of polarisation transmits signals more efficiently.

For the transmission of television signals in two colours it is possible, according to the invention, to provide two aerials at the transmitter, the plane of polarisation of one aerial being substantially at right angles to that of the other aerial and to feed to the aerials signals obtained on scanning an object through suitable colour filters and to provide at the receiver two aerials. One arranged in the plane of polarisation of one set of signals and the other in the plane of polarisation of the other set of signals. These two sets of signals being subsequently fed to two reproducing devices, such as cathode ray tubes, the fluorescent screens of which reproduce individually the two sets of signals and the fluorescent colour of the screens corresponding to the filters t the transmitter. The two pictures produced at the receiver are viewed simultaneously and super-imposed for which purpose the two cathode ray tubes may be arranged in such a manner that the fluorescent screens are substantially at right angles to one another and arranged at 45 between the two tubes is a half silvered mirror that is to say, a mirror which reflects substantially half of the light incident on it so that on viewing the mirror the two pictures will be super-imposed and viewed simultaneously.

A somewhat similar form of transmitting arrangement may be employed for the transmission of pictures in stereoscopic form and in this case two sets of signals of the same object, but from cameras displaced an amount corresponding to the inter-ocular distance, will be transmitted from the two aerials and at the receiver two cathode ray tubes are provided for receiving the sets of signals, the images reproduced on the fluorescent screens being viewed through suitable lenses whereby the two images are super-imposed to produce a stereoscopic effect. The stereoscopic reproduction of images is also known in which two displaced images in different colours are viewed through suitable colour filters and the present invention can also be applied to such a form of stereoscopic reproduction.

Although the invention is particularly applicable for transmissions of intelligence on short wave lengths, since the planes of polarisation of the waves retain their polarisation to a maximum extent, it is however also possible to employ the invention for the transmission of intelligence employing signals of lower frequencies in accordance with the invention although the planes of polarisation of such lower frequency signals are not maintained to the same degree as signals of very high frequency.

Slight shifts of polarisation which occur at short wavelengths may be corrected by slightly tilting the receiving aerial so as to cut out the unwanted signal.

This invention may also be readily adapted to provide binaural reproduction of sound at a receiver. Each of the two transmitters is modulated by audio frequency signals which are obtained from separate microphones which are placed in suitable positions with respect to the source of the sound being transmitted. At the receiver the two carriers are separately received and passed through separate channels to separate loud speakers which are so positioned that binaural reproduction is obtained.

Having now particularly described and ascertained the nature of my said invention and in what manner the same is to be performed, I declare that what I claim is:

  1. A wireless transmission system comprising means for transmitting two modulated carriers each having substantially the same wavelength and the plane of polarisation of one carrier being substantially at right angles to the plane of polarisation of the other carrier, so that a suitable receiver can selectively receive one or other of the transmissions.
  2. A wireless transmission system according to claim 1, wherein said carriers are transmitted from two remotely situated transmitters.
  3. A wireless transmission system according to claim 1, wherein the said carriers are radiated from two adjacent aerials.
  4. A wireless transmission system according to claim 1, 2 or 3, wherein said carriers are modulated by the same signal.
  5. A wireless transmission system comprising two remotely situated transmitters for radiating signals having wide band width, such as television signals, and wherein, in order to avoid or reduce this difficulty due to the band width of said signals and the shortage of available wavelengths making it impossible to operate said transmitters at wavelengths such that the side-band frequencies of said signals do not overlap, so that at points between said transmitters it is difficult to receive signals from either of said transmitters without interference from the other, said transmitters are arranged to transmit signals on closely adjacent wavelengths and the plane of polarisation of the signals radiated from one transmitter is arranged to be substantially at right angles to the plane of polarisation of signals radiated from the other transmitter so that a receiver having a suitable aerial can selectively receive signals from one or other of the transmitters.
  6. A television system comprising a transmission system having means for transmitting two modulated carriers, each having substantially the same wavelength and the plane of polarisation of one carrier being substantially at right angles to the plane of polarisation of the other carrier, the signals for modulating said carriers being obtained by scanning the picture to be transmitted through suitable colour filters so that with a suitable receiving system the reproduced picture has to a certain degree the same colouring as the picture transmitted.
  7. A television receiver designed to receive signals from a transmission system as claimed in claim 6, wherein the modulated carriers are separately received and passed through separate channels to two reproducing devices which are adapted to produce pictures substantially the same as that of the corresponding colour filter at the transmitter, it being arranged that the two pictures are superimposed and viewed simultaneously so that a coloured reproduction is obtained.
  8. A television receiver according to claim 7, wherein said pictures are produced on two screens which are substantially at right angles to one another, and wherein a half silvered mirror is placed between said screens and at an angle of substantially 45 to each of said screens so that on viewing the mirror the two pictures are superimposed and viewed simultaneously.
  9. A television receiver according to claim 7 or 8, wherein said reproducing devices comprise cathode ray tubes, the screen of each of which is arranged to fluoresce in a colour which is substantially the same as that of the corresponding colour filter at the transmitter.
  10. A television system comprising a transmission system having means for transmitting two modulated carriers, each having substantially the same wavelength and the plane of polarisation of one carrier being substantially at right angles to the plane of polarisation of the other carrier, the signals for modulating said carriers being obtained in such a manner so that with a suitable receiver stereoscopic reproduction is obtained.
  11. A television receiver designed to receive signals from a transmission system as claimed in claim 10, wherein the modulated carriers are separately received and passed through separate channels to two reproducing devices which are so arranged that on being viewed through suitable lenses the two images are superimposed to produce a stereoscopic effect.
  12. A television receiver according to claim 11, wherein said reproducing devices comprise cathode ray tubes.
  13. A television receiver according to claim 11 or 12, wherein said reproducing devices produce pictures of different colour which are viewed through suitable colour filters so that stereoscopic reproduction is obtained.
  14. A wireless receiver designed to receive signals from a transmission system as claimed in any of claims 1 to 5, comprising a dipole aerial which is arranged to be rotatable so that any one of the two modulated carriers can be selectively received.
  15. A wireless transmission system comprising means for transmitting two modulated carriers each having substantially the same wavelength and the plane of polarisation of one carrier being substantially at right angles to the plane of polarisation of the other carrier, the modulating signals comprising audio signals which are obtained by microphones which are so arranged that with a suitable receiver binaural reproduction is obtained.
  16. A wireless receiver designed to receive signals from a transmission system as claimed in claim 15, wherein said modulated carriers are separately received and passed through separate channels to separate sound reproducing devices which are so arranged as to give binaural reproduction.
  17. Any of the wireless transmission systems substantially as described herein.
  18. Any of the wireless receivers substantially as described herein.

Dated this 13th day of September, 1938

F. W. Cackett

Chartered Patent Agent