US 4,058,771 AGranted

Double-balanced frequency converter

AssigneeSony Corporation

InventorsMitsuo Ohsawa, Wataru Yamatani

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Abstract

A frequency converter of the type having a local oscillating stage for producing a local oscillating signal and a double-balanced type mixing stage provided with a first pair of inputs for receiving a signal to be frequency converted and a second pair of inputs for receiving the local oscillating signal. The output of the mixing stage can be connected through a tuned circuit so as to frequency convert the input signal to an intermediate frequency (IF) signal. The local oscillating stage includes a first pair of differentially-connected transistors, the collector electrode of one being connected to a resonant circuit and, additionally, through an RC positive feedback circuit to the base electrode of the other transistor. The double-balanced type mixing stage includes a second pair of differentially-connected transistors, one of which being connected in cascade with a first differential amplifier and the other of which being connected in cascade with a second differential amplifier. The base electrodes of the second pair of differentially-connected transistors receive the local oscillating signal which is applied thereto in opposite phase relation. The first and second differential amplifiers both receive the input signal which is applied thereto in opposite phase relation. A DC bias circuit is provided for applying substantially equal bias voltages through equal impedances, such as resistors, to both pairs of differentially-connected transistors. Preferably, the DC bias circuit includes an emitter-follower.

Claims16

Dependent claims

A frequency converter, comprising:

local signal generating means including a first differential circuit having a first pair of differentially-connected transistor means and a positive feedback circuit coupling the collector electrode of one of said first pair of transistor means to the base electrode of the other, said local signal generating means having a pair of output terminals for producing a local oscillating signal thereacross;
double-balanced type mixing means including a second differential circuit having a second pair of differentially-connected transistor means, a third differential circuit having a third pair of differentially-connected transistor means, and a fourth differential circuit having a fourth pair of differentially-connected transistor means, said second differential circuit having a pair of outputs coupled to said third and fourth differential circuits, respectively;
signal input means for supplying an input signal to be frequency-converted across the base electrodes of said third pair of transistors and across the base electrodes of said fourth pair of transistors;
means for applying said local oscillating signal produced across said local signal generating means output terminals to the base electrodes of said second pair of transistor means in opposite phase relation, whereby said input signal and said local oscillating signal are mixed in said double-balanced type mixing means;
selecting means coupled to the collector electrode of one of said third pair of transistor means and to the collector electrode of one of said fourth pair of transistor means to produce a frequency-converted output signal of selected frequency;
and
bias means coupled to said first and second differential circuits for applying the same DC bias voltages to both said circuits.

4 more elements

A frequency converter comprising a local oscillating stage for producing a local oscillating signal;

a double-balanced type mixing stage having a first pair of inputs for receiving a signal to be frequency converted, said signal being applied to said first pair of inputs in opposite phase relation, and a second pair of inputs for receiving said local oscillating signal thereat in opposite phase relation;
means for supplying a DC operating voltage to said local oscillating stage and to said mixing stage;
and a DC bias circuit for applying substantially equal bias voltages to said local oscillating stage and to said mixing stage, said bias circuit comprising an emitter-follower transistor whose collector electrode is coupled to said supply means and whose emitter electrode is connected to an emitter resistance means, means for applying a predetermined potential to the base electrode of said transistor, and common impedance means through which said emitter electrode is coupled both to said local oscillating stage and to said mixing stage.

Dependencies are inferred from the claim text.