US 5,140,705 A · Center-tapped coil-based tank circuit for a balanced mixer circuit

Abstract

An RF tank circuit includes a coil with a center tap, the RF tank circuit being for receving an input RF signal, and for providing a balanced mixer circuit by being arranged in one of: a) receiving a local signal through second and third capacitors at first and second coil ends, respectively, with the center tap grounded; and, b) receiving a local signal at the center tap. An impedance is connected between the first and second coil ends of the RF tank circuit, the impedance providing low impendance for a predetermined intermediate frequency signal, and high impedance for a predetermined high frequency signal and a local signal. A bias resistor is connected between a middle connecting point of the impedance and ground. The coil of the RF tank cicuit can be one of a primary and second winding of an isolation transformer, with a remaining one of the primary and secondary windings being connected to an RF signal source, the isolation transformer being for preventing a leakage of a local signal to the RF signal source.

Claims3

Dependent claims

A balanced mixer circuit comprising:

RF tank circuit means including coil means with a center tap grounded, and first capacitor means connected between first and second ends of said coil means;
local signal oscillator means connected to said first and second ends of said RF tank circuit means, respectively, through second and third capacitor means;
impedance means connected between said first and second ends of said RF tank circuit means, said impedance means providing low impedance for a predetermined intermediate frequency signal, and high impedance for a predetermined high frequency signal and a local signal;
bias resistor means connected between a middle connecting point of said impedance means and ground;
first and second switching means connected, respectively, to said first and second ends of said RF tank circuit means, for receiving said local signal and performing a switching operation in accordance with said local signal;
tuning means connected to said first and second switching means, said tuning means being tuned to derive an intermediate frequency signal from outputs of said first and second switching means.

3 more elements

Dependencies are inferred from the claim text.

Center-tapped coil-based tank circuit for a balanced mixer circuit

Life of this patent

Center-tapped coil-based tank circuit for a balanced mixer circuit

Life of this patent

Abstract

Claims3