Patent GB-833130-A (GB)
Title: Improvements in or relating to frequency changers for ultra-high frequency electromagnetic waves
IPC: H03D9/06
Filed: 1958-01-27
Abstract: 833,130. Gyromagnetic amplifiers. MARIE, G. R. P. Jan. 27, 1958 [Jan. 26, 1957; March 15, 1957], No. 2719/58. Class 40 (9). [Also in Groups XL (b) and XL (c)] A frequency changing amplifier comprises magnetic material 1 in a steady magnetic field (e.g. from 2 and 3, Fig. 1) so that the material exhibits gyromagnetic resonance, the material being subject to an alternating magnetic field of frequency F1 at right angles to the steady field (e.g. by coils 4) and to an alternating magnetic field of frequency F2 at right angles to the other fields (e.g. by coils 6) an output voltage of frequency (F1ŒF2) being derived from variations of the total magnetic field in the direction of the steady field (e.g. from coil 9). Fig. 2 shows first and second waveguides 24, 25 for feeding a signal and a local oscillation through a transition guide 38 to a rectangular cavity 22 resonant at the two frequencies. Four ferrite plates are arranged between poles of a permanent magnet system 26 to 29 in gaps in the sides of the resonator and covered by a grid of wires, three of which 34, 35 and 36 are shown and which complete the electrical circuit across the side walls. One of the inputs produces waves in the transition guide electrically polarized in the direction of the Y axis and the other in the direction of the X axis so that in the cavity the fields are parallel to the Z axis and respectively symmetrical with respect to the ZX plane and the ZY plane and respectively asymmetrical with respect to the other plane. The associated magnetic fields cause a sum or difference frequency fields to be produced by the gyromagnetic resonance effects in the ferrite plates and these fields induce voltages in aiding relation in an output coil 30 wound round the perimeter of the resonator. In a second embodiment (Figs. 3 and 4) one input is fed to a waveguide 41 while the other is fed to a waveguide 47. Guide 41 has a slot 48 in its side and the signal in guide 47 passes through the slot and along two rods 43 to a half wave rod 40. This rod is surrounded at its centre part by ferrite material 45 and under the influence of the two input signals and a steady magnetic field produced by an electromagnet 49, 50, 51 and 52 produces by gyromagnetic action a sum or difference frequency in an output coaxial line 53, the centre conductor 44 of which is coupled to the rod 40. A choke 54 is provided to prevent the signal in guide 47 passing into the output line and a tuning screw 46 tunes the input line to one of the input frequencies and adjusts the power supplied from this line to the ferrite element. The polepiece 50 of the electromagnet is formed of strips 50 of magnetic material in the waveguide arranged so that the transmission of the signal in the guide is not prevented. Fig. 6 shows a further embodiment in which one signal is fed to the system via a guide 67 and the other via a guide 61 coupled to the first guide by means of a quarter-wave stub 66 and a half wavelength conductor 62. The first waveguide carries two ferrite elements 69, 70 arranged together and each of which is wound with a coil. These coils which are connected in series aiding relationship provide the sum or difference frequency output and are tuned by a series or parallel condenser 76. The centre of the rod 68 is arranged at a half a wavelength from the end of the guide and this is ensured by extending the narrow dimension of the guide on each side as at 81 and narrowing the broad dimension by means of two conductive bars 82 and 83. It is stated that in the above embodiments maximum efficiency is obtained at certain discrete values of the so-called nutation notion, a formula for which values is given in the Specification. Under these conditions a power gain in the system is possible. It is also said that other magnetic materials may replace the ferrite material.