Patent GB-964565-A (GB)
Title: Transmitter apparatus
IPC: H03L7/16
Filed: 1962-07-31
Abstract: 964,565. Automatic frequency control. SIEMENS & HALSKE A.G, July 31, 1962 [July 31, 1961], No. 29491/62. Heading H3A. In a remote control transmitter in which a relatively low frequency carrier signal modulated in accordance with the intelligence to be transmitted is transposed by frequency changing to a required frequency in the transmitter output frequency band, the frequency of operation of the frequency changing oscillations is stabilized against a standard crystal oscillator signal either by an analysis method in which the oscillator signal is successively mixed with the output of a number of decade oscillators controlled by the standard signal to provide a stabilizing control signal or by a synthesis method in which a signal synthesized by mixing the outputs of a number of decade oscillations is directly compared with the oscillator signal to provide the stabilizing control signal. A crystal oscillator 06 provides an output at 1 Mc/s. which is multiplied and divided to provide outputs at 10 Mc/s., 1 Mc/s., 100 kc/s., 10 kc/s., 1 kc/s. and 100 c/s. for control of the decade oscillators. In the frequency analysis arrangement shown a translator unit V supplies a modulated signal at a carrier frequency of 6 Mc/s., which is mixed in unit M1 with the output of oscillator 01, operating in the range 59.0001-60 Mc/s., to provide a signal in the range 65.0001-66 Mc/s. The output of oscillator 01 is also applied to mixer M2 where it is mixed with a 50 Mc/s. signal derived from the crystal source and the difference frequency signal in the band 9.0001- 10 Mc/s. is selected by filter F1. This difference frequency signal is mixed in unit M3 with the output of a first decade oscillator 02 which supplies a signal at a selected one of the frequencies spaced by 100 kc/s. in the band 8.1- 9 Mc/s. and the difference frequency signal in the band 0.9001-1 Me/s. is selected by filter F2. The output of oscillator 02 is also applied to a mixer M6 in which it is added to a selected one of 10 signals spaced in frequency by 100 kc/s. in the band 1-1.9 Me/s. and derived from the crystal source, such that the sum of the signal frequencies equals 10 Me/s. This signal is selected by a filter and compared in a phase comparator with a 10 Mc/s. signal derived from the crystal source to provide a signal for stabilizing the frequency of oscillator 02. Operating in a similar manner, decade oscillator 03 operating with mixer M4 and oscillator 04 operating with mixer M5 reduce the signal to the band 9.1-10 kc/s. and this signal is applied to a phase comparator Ph1 with a signal selected from one of the signals supplied in 100 c/s. steps by oscillator 05 in the band 9.1-10 kc/s. and stabilized in the same manner as oscillators O2-O4. The phase comparator Ph1 supplies an output signal to control oscillator O1. The signal in the band 65.0001- 66 Mc/s. is then mixed with a signal supplied from oscillator 07 in the band 66-95 Mc/s. to provide a signal in the band 0-29.999 Mc/s. for transmission. The output of oscillator 07 is also applied to a mixer with a selected signal at either 40, 50 or 60 Mc/s. derived from the crystal source to provide a signal in the band 26-35 Mc/s. which is applied to a phase comparator Ph3 with a selected signal from the same band supplied by oscillator 08 and stabilized from the crystal source. The comparator provides an output signal for the control of oscillator 07. Each of the decade oscillators includes a pair of voltage controlled comparators, e.g. silicon diodes, one of which is connected to a switching arrangement by means of which either manually or by remote control using transistor switches, the voltage across the diode can be adjusted in steps to provide the spot frequencies spaced throughout the oscillator operating band and the other connected to the oscillator stabilizing control voltage source.