GB587583A - Improvements in ultra high frequency translation devices - Google Patents

Abstract

587,583. 'Wireless receiving apparatus. WESTERN ELECTRIC CO., Inc. June 15, 1944, No. 11477. Convention date, April 19, 1943. [Class 40 (v)] An ultra-high-frequency device comprises a crystal rectifier for translating signal waves in an input circuit into signal waves in an output. circuit, and means for applying to the crystal rectifier a direct voltage of such critical polarity and magnitude as to reduce the noise currents in the output circuit while the magnitude of the signal currents therein remains unaffected. Fig. 1 shows the invention applied to the input and frequency changing stages of a receiver in which microwave energy is received by a horn 7 and fed through a slot 5 to a concentric line comprising an outer conductor 2 and inner conductor 3, 4, both connected to a conducting block 29. A concentric line 14, 15 serves for the introduction of beat-frequency energy from a source 12 by way of an adjustable probe 16. The combined energy is fed to the spring contact 9 of a silicon detector 10 which is connected to outer conductor 2 by a high-frequency byepass condenser 11. Intermediate frequency energy is taken through line 18, 19 and condenser 30 to subsequent stages 24. Line 18, 19 is extended and the end terminated in disc 22 and part 21 forming a condenser such as to produce an effective short-circuit for intermediate frequency waves. Also the length of the line 18, 19 is chosen to give a nodal point at 21, 22. This enables a direct bias voltage from source 27 to be applied at this point to the crystal without interaction with the intermediate frequency circuit. Curves are supplied (Figs. 3-7, not shown) to show that the application of a small positive voltage having a critical optimum value of about .2 volts results in a minimum value for the noise currents without substantially reducing the signal output. The beat - frequency power is increased to its optimum by adjustment of the probe 16. The inner conductor 3, 4 is made of parts 3, 4 having different thicknesses so as to'present to the rectifier an impedance such as to support harmonics of the beat - frequency waves. Thereby selecting the lengths of 3 and 4, the harmonics may be brought into phase with the fundamental, thus increasing the power. Detailed constructional forms of the apparatus are shown in Figs. 8-10 and 12 (not shown). Fig. 11 shows a suitable construction of the crystal detector. A silicon crystal 47 is mounted on a screw-threaded end 74 of a metal block 48 which is screwed into a ceramic tube 91 to the other end of which is screwed a plug 46 carrying a metal spring contact 45. Specification 551,209 is referred to.