Mackay Radio & Telegraph Co. v. Radio Corp. of America
306 U.S. 86 (1939)

Annotate this Case

U.S. Supreme Court

Mackay Radio & Telegraph Co. v. Radio Corp. of America, 306 U.S. 86 (1939)

Mackay Radio & Telegraph Co. v. Radio Corporation of America

No. 127

Argued December 14, 15, 1938

Decided January 30, 1939

306 U.S. 86




1. Carter patent, No. 1,974,387, for a directive antenna system for use in radio communication, held not infringed by petitioner's antenna structures. Pp. 306 U. S. 88, 306 U. S. 101.

Claims 15 and 16 are invalid so far as they claim antennae of wire lengths intermediate of multiples of half-wavelengths. And, so far as the patent discloses and claims invention of a V antenna structure made in conformity to the Abraham formula, petitioner's structures do not infringe, for none of them conforms to the Abraham formula. One has wires which are an integral number of half-wavelengths long, but uses an angle 10% smaller than that derivable from the Abraham formula; all of the others have wires which are not multiples of half-wavelengths long and angles not derivable from the formula.

2. The disclosure of the Carter patent was that the best directional radio propagation by the V type antenna is obtained in the direction of its bisector, with a structure in which the angle of the wires, their length, and the length of wave propagated are in a definite mathematical relationship expressed by a formula disclosed in the specifications. The formula shows that the appropriate angle between each of the antenna wires and their bisector depends upon the wavelength to be propagated and the wire length, which is a multiple of half-wavelengths. The formula had been developed and published by Abraham thirty years previously. Lindenblad had taught that, with an arrangement of antenna wires at an angle, radiation will occur in the direction of the bisector of the angle, and that the preferred angle was dependent upon an indicated relationship between wire length and wavelength. Carter's invention therefore, if it was invention, consisted in taking the angle of the Abraham formula as the angle between each wire of the V antenna and its bisector, and thus establishing along the bisector the greatest directional radio activity. The empirical formula of the specifications and Claims 15 and

Page 306 U. S. 87

16, derived graphically from the Abraham formula, disclosed no invention other than the application of the Abraham formula to the V antenna when wavelength and wire length are known.

Held, assuming that it was more than the skill of the art to combine the teaching of Abraham with that of Lindenblad and others who had pointed out that the arrangement of the wires at an angle enhanced directional radio activity along their bisector, then the invention was a narrow one, consisting of a structure conforming to the teachings of the Abraham formula as to angle and wire length relative to wavelength, and is to be strictly construed with regard both to prior art and to alleged infringing devices. Carter, avoiding prior art by defining his angle for antennae with wires of particular wavelengths with mathematical precision, cannot discard that precision to establish infringement. Pp. 306 U. S. 94, 306 U. S. 102.

3. The application of Carter, at least before the amendments introduced subsequently to the commencement of the present litigation, cannot be construed as embracing structures not conforming to the Abraham formula. And the attempt by amendment to extend the claims, based on the application of the empirical formula (derived from the Abraham formula) to wire lengths not multiples of half-wavelengths, must fail because it involved a departure from what Carter's application had described as his invention, and a contradiction of it. P. 306 U. S. 98.

4. It is unnecessary in this case to decide the further question whether petitioner's structures avoid infringement because the direction of their principal radioactivity is not in the plane of the wires. P. 306 U. S. 102.

96 F.2d 587 reversed.

Certiorari, 305 U.S. 582, to review a decree which modified and reversed a decree of the District Court, 16 F.Supp. 610, dismissing the bill in a suit to enjoin infringements of patents.

Page 306 U. S. 88

MR. JUSTICE STONE delivered the opinion of the Court.

The questions presented for decision by the petition for certiorari are whether the Carter patent, No. 1,974,387, of September 18, 1934, for a directive antenna system for use in radio communication, is valid and is infringed by antennae structures used by petitioner in such communication.

Respondent brought the present suit in the District Court for eastern New York to enjoin infringements of four patents relating to radio antennae or their operation. Two were those of Carter and two those of Lindenblad. Of these, only the second Lindenblad patent, No. 1,927,522, of September 19, 1933, for an antenna for radio communication, is of present importance. When the suit was begun, the application for the third Carter patent, with which we are presently concerned, was pending. After petitioner had answered, and respondent, as a result of the litigation, had acquired knowledge of the particulars of the structure and operation of petitioner's antennae, Carter, respondent's assignor, amended the statement of his invention in his application so as, in terms, to embrace a differentiating feature of petitioner's structures. After this patent was issued, respondent was permitted to file a supplemental bill charging infringement of it. The suits were consolidated, and the parties proceeded to trial on the issues of the validity and infringement of all five patents.

After taking the voluminous testimony of numerous witnesses, the trial court found that none of the patents in suit was infringed, and decreed that the suits be dismissed. 16 F.Supp. 610. It held that none of them was a pioneer patent; that none had been employed by anyone; that respondent's commercial structures did

Page 306 U. S. 89

not follow the teachings of any of them, and that consequently they were not entitled to a broad construction. With respect to the Carter patent in suit it said: "The disclosure and the claims were broadened not only contrary to their original terminology, but to their spirit as well." And,

". . . by those amendments, the plaintiff attempted to mold the third Carter patent, both as to disclosure and claims, to cover defendant's antenna systems. This could not lawfully be done."

On appeal from so much of the decree as related to the second Lindenblad patent and the third Carter patent, the Court of Appeals for the Second Circuit affirmed as to the Lindenblad patent, but reversed as to the Carter patent, holding Claims 15 and 16 valid and infringed. 96 F.2d 587. We granted certiorari, 305 U.S. 582, because of the nature and importance of the case, on a petition which urged as grounds for its allowance that validity and infringement of the Carter patent were in doubt, and that, as petitioner is the only competitor of respondent in the business of worldwide public radio communication, further litigation, resulting in conflict of decision among circuits, was improbable.

In ordinary broadcasting, radio waves are projected in all directions from the sending station. In radio communication, it is advantageous, and has long been the practice, to use a directive antenna by which the waves of radio activity emanating from it are projected as a beam in the direction of the receiving station. In practice, the beam is directed at an angle from the earth's surface toward the ionized layer of the stratosphere, or Heaviside layer, from which the beam is deflected toward the earth's surface in the compass direction of the receiving station. In more recent years, it has been the practice to use relatively short wavelengths for radio communication.

Page 306 U. S. 90

The radio waves are generated at the sending station by feeding an oscillating electric current of appropriate character into the wire or wires of the antenna. The electric waves in the wires energize radio activity, which the antenna projects as radio waves toward the receiving station. By modulating or interrupting the current, corresponding modulation or interruption of the radio waves is effected, which may be used as a means of transmitting any desired signal. The waves, as modulated, impinge on the antenna of the receiving station devised to receive and utilize them as a means of controlling, with corresponding modulation, an electric current which, in turn, actuates a mechanism contrived to give audible or visual expression to the transmitted signal.

The effective part of the antenna is a copper wire from which the radio waves are radiated, supported on towers or poles at a height above the ground depending on the wavelength used. The wire may be parallel with the earth, or vertical, or arranged at an angle, depending upon the function to be performed. Before Carter, antennae of two or more wires in varying arrangement had been used. The second Lindenblad patent showed an antenna of two wires arranged at an angle in the form of a V or an X, and it pointed out that, in such an arrangement, radiation will take place in the direction of the axis or bisector of the angle of the diverging wires, and that

"the spacing at the open end [of the wires], while variable over a great range, should be in the neighborhood of a fifth of the length, and the length of each antenna section should be of the order of magnitude of five to ten waves long."

While such an arrangement projects the radio waves principally in two directions along the bisector of the angle of the antenna wires, the prior art had made use of an arrangement of wires, parallel to the wires of the angular

Page 306 U. S. 91

antenna, as a "reflector" by which the radiation was projected as a beam in one direction away from the reflector and along the bisector of the angle of the wires.

The present Carter patent is for an "antenna system utilizing standing wave phenomena." Like the second Lindenblad patent, it is concerned with a V antenna by which the principal radiation is directed in the plane of the wires along the bisector of their angle. The disclosure of the patent, in which the court below found invention, was that the best directional radio propagation by the V type antenna is obtained with a structure in which the angle of the wires, their length, and the length of wave propagated are in a definite mathematical relationship expressed by a formula disclosed in the specifications.

In explaining his invention, Carter pointed out that

"It is known that, when a wire having a length greater than the operating wavelength is excited in such manner that standing waves are produced thereon, radiation will occur principally in the direction of symmetrical cones having their apices at the center of the wire. Such is the case with a wire having a length equal to a plurality of one-half-wavelengths at the operating frequency. The radiation pattern produced in such instance appears, in cross-section, in the form of symmetrical cones about the wire. The present invention, which makes use of these phenomena, in its most simple aspect, employs a pair of open-ended wires energized in phase opposition to have standing waves throughout the length of the wires, the wires having such angular relation with respect to each other as to obtain a highly directional, efficient, and simple antenna system. [Footnote 1] "

Page 306 U. S. 92

The patent states the mathematical formula by which the desired relationship is secured, which shows that the appropriate angle between each of the antenna wires and their bisector depends upon the wavelength to be propagated and the use of antenna wires of a length which is a multiple of half-wavelengths. [Footnote 2]

Page 306 U. S. 93

The significance of the formula lies in the fact that the angle between the wire and the direction of greatest radio activity is a trigonometrical function of two variables, the wavelength used and the "number of half-wavelengths contained in the wire," and that, as the application stated, the use of the formula, in practice, presupposes the use of a wire whose length is a multiple of half-wavelengths. The patent then explains that the angle

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