Cascaded harmonic multipliers

Claim 1

IN FREQUENCY MULTIPLYING APPARATUS OPERATIVE AT MOCROWAVE FREQUENCIES, A SECTION OF COAXIAL TRANSMISSION LINE HAVING INNER AND OUTER CONDUCTORS, FIRST AND SECOND VARACTOR DIODES CONNECTED IN THE INNER CONDUCTOR OF SAID TRANSMISSION LINE AND EACH OPERATIVE WHEN BIASED TO GENERATE HARMONICS OF AN INPUT SIGNAL FREQUENCY, SAID VARACTORS BEING IN SERIES, COAXIAL CAVITIES, ONE FOLLOWING EACH VARACTOR, AND EACH CAVITY HAVING END WALLS AND EACH INCLUDING A CENTRAL STUB RESONANT AT A SELECTED ONE OF SAID HARMONICS AND OPERATIVE TO TRAP FREQUENCIES OTHER THAN SAID SELECTED HARMONIC PRODUCED BY THE PRECEDING VARACTOR DIODE, MEANS CONNECTING THE INNER CONDUCTOR OF SAID TRANSMISSION LINE TO A POINT ON THE STUB OF SAID FIRST COAXIAL CAVITY, SELECTED TO PROVIDE RESISTANCE MATCHING OF SAID FIRST VARACTOR DIODE TO THE OUTPUT OF SAID FIRST CAVITY, A COAXIAL STUB OF A LENGTH EQUAL TO APPROXIMATELY A QUARTER WAVELENGTH AT SAID INPUT FREQUENCY CONNECTED IN BRANCH RELATIONSHIP WITH SAID TRANSMISSION LINE AT A POINT BETWEEN SAID SECOND VARACTOR AND SAID SECOND COAXIAL CAVITY, SAID COAXIAL STUB BEING OPERATIVE TO PROVIDE A REACTIVE MATCH BETWEEN SAID SECOND VARACTOR DIODE AND THE OUTPUT LOAD OF SAID SECOND CAVITY, A SOURCE OF DIRECT CURRENT BIASING VOLTAGE FOR SAID SECONE VARACTOR DIODE CONNECTED TO THE CENTRAL STUB OF SAID SECOND CAVITY, AND MEANS FOR COUPLING SAID SELECTED HARMONIC FROM SAID SECOND CAVITY.