Balanced mixer with feedback pre-amplifier
First Claim
Patent Images
1. A balanced mixer circuit comprising:
- a first differential input port for providing an input radio frequency to the balanced mixer circuit;
a second differential input port for providing a local oscillator frequency to the balanced mixer circuit;
a transconductance amplifier means for receiving and converting the input radio frequency into a collector current, said transconductance amplifier means being coupled to the first input port;
a splitter circuit means for splitting the collector current, said splitter means being coupled to the transconductance amplifier means;
a mixer means for receiving a first portion of a split output of the splitter circuit means and the local oscillator frequency, said mixer means being coupled to the splitter circuit means and the second differential input port;
a first feedback means for providing a first feedback current to the first input port, said first feedback means coupled between a second portion of the split output of the splitter circuit means and the first input port;
a second feedback means for providing a second feedback current to the first input port, said second feedback means being coupled to the transconductance amplifier means; and
an output port coupled to the mixer means.
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Abstract
An improved balanced mixer is provided for use in radio communication devices. The improved balanced mixer comprises a known Gilbert type mixer, a transconductance amplifier, a signal splitter, and a dual feedback structure from the pre-amplifier output to the input ports, thereby providing better linearity, that is, better input third order intercept point (IIP3), and improved impedance matching, without increasing the circuit noise figure.
86 Citations
12 Claims
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1. A balanced mixer circuit comprising:
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a first differential input port for providing an input radio frequency to the balanced mixer circuit;
a second differential input port for providing a local oscillator frequency to the balanced mixer circuit;
a transconductance amplifier means for receiving and converting the input radio frequency into a collector current, said transconductance amplifier means being coupled to the first input port;
a splitter circuit means for splitting the collector current, said splitter means being coupled to the transconductance amplifier means;
a mixer means for receiving a first portion of a split output of the splitter circuit means and the local oscillator frequency, said mixer means being coupled to the splitter circuit means and the second differential input port;
a first feedback means for providing a first feedback current to the first input port, said first feedback means coupled between a second portion of the split output of the splitter circuit means and the first input port;
a second feedback means for providing a second feedback current to the first input port, said second feedback means being coupled to the transconductance amplifier means; and
an output port coupled to the mixer means. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A balanced mixer circuit comprising:
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a transconductance amplifier receiving an input radio frequency and converting said input radio frequency into a collector current;
a splitter circuit coupled to receive the collector current and to split the collector current into a feedback current and a mixer current;
a mixer core coupled to receive a local oscillator frequency and the mixer current, said mixer core outputting an intermediate frequency signal;
a first feedback path coupled between the splitter circuit and the transconductance amplifier, said first feedback path being used by the feedback current to provide a feedback to the input radio frequency;
a second feedback path coupled between the splitter and the transconductance amplifier such that the transconductance amplifier is coupled between the first and the second feedback paths.
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Specification