H - Electricity – 03 – B
Patent
H - Electricity
03
B
328/16
H03B 19/10 (2006.01) H03B 19/14 (2006.01)
Patent
CA 1234414
ABSTRACT: A frequency multiplying circuit which is partic- ularly suitable for battery operated portable radio equip- ment at VHF, such as radio paging receivers. The basic frequency multiplying circuit comprises a differential amplifier formed by two transistors (TR1, TR2) whose emitters are connected by a current source (24) to a low voltage supply rail, collector resistors (R1, R2) are con- nected to a higher voltage rail as is also done with the base electrode of one of the transistors, the base elec- trode of the other of the transistors has an oscillator connected thereon. An LC resonant circuit (L1, C1) coupled between the collectors of the two transistors (TR1, TR2) and is tuned to select either the basic frequency of the oscillator (12) or an odd harmonic thereof. In order to overcome problems of excessive damping of the resonant cir- cuit (14) due to the collector resistors (R1, R2) of the differential amplifier being effectively in parallel there- with which damping is made worse when the load of the following stage is added, it was found that the frequency multiplying circuit could provide a high quality factor and low power consumption if the coupling between the differ- ential amplifier and the resonant circuit (14) is reduced and also if the effect of the load of the next following stage was overcome. This is achieved by connecting a nega- tive resistance circuit (22) across the resonant circuit. The negative resistance circuit (22) comprises a transis- torised differential amplifier, the base electrodes of the transistors (TR3, TR4) are cross connected to the collector of the other transistor, to form a negative conductance which is in parallel with the positive conductances which are causing the resonant circuit to be lossy. Hence the parallel loss conductance is reduced in value and the effective Q is increased.
464766
Razzell Charles J.h.
Van Rumpt Herman W.
N.v.philips'gloeilampenfabrieken
Van Steinburg C.e.
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