This is a U.S. National Stage of PCT Application No. PCT/US2015/065378, filed on Dec. 11, 2015, the disclosure of which is incorporated herein in its entirety by reference.
The subject invention relates to an active quadrature circuit for high-frequency applications.
Quadrature generation circuits that generate in-phase (I) and quadrature (Q) (quarter cycle or 90 degrees out of phase) output signals from an input signal have many applications. For example, a quadrature generation circuit may be used in a phase shifter system. Quadrature generation may be implemented with passive or active elements. An exemplary quadrature generation circuit that uses passive elements is a resistor-capacitor (RC) circuit. When resistors are manufactured for use in RC circuits, the resistors exhibit variations in their value. This process variation results in an issue of variation in the resulting RC circuits and, consequently, accuracy. Quadrature generation circuits that use active elements consume significant power. Accordingly, it is desirable to provide an active quadrature generation circuit that avoids the accuracy issues of passive elements while consuming less power.
In one exemplary embodiment, an active quadrature generation circuit configured to provide an in-phase output signal and a quadrature output signal based on an input signal includes an input node configured to receive the input signal; a first transistor including a collector connected to a power supply pin; and a second transistor including a base connected to the power supply pin, the second transistor differing in size from the first transistor by a factor of K, wherein the in-phase output signal and the quadrature output signal are generated based on an inherent phase difference of 90 degrees between a current at a collector of the first transistor and a current at a base of the second transistor.
In another exemplary embodiment, a method of fabricating an active quadrature generation circuit on an integrated circuit includes arranging an input node to receive the input signal; arranging a first transistor such that a collector of the first transistor is connected to a power supply pin of the integrated circuit; arranging a second transistor such that a base of the second transistor is connected to the power supply pin; sizing the second transistor to be a factor of K of a size of the first transistor; and generating an in-phase output signal and a quadrature output signal from the input signal based on an inherent phase difference of 90 degrees between a current at the collector of the first transistor and a current at the base of the second transistor.
The above features and advantages and other features and advantages of the invention are readily apparent from the following detailed description of the invention when taken in connection with the accompanying drawings.
Other features, advantages and details appear, by way of example only, in the following detailed description of embodiments, the detailed description referring to the drawings in which:
The following description is merely exemplary in nature and is not intended to limit the present disclosure, its application or uses. It should be understood that throughout the drawings, corresponding reference numerals indicate like or corresponding parts and features.
Embodiments discussed herein relate to active quadrature generation circuits that consume less power than traditional quadrature generation circuits that use active elements. The quadrature generation circuits according to the embodiments detailed herein rely on inherent characteristics of transistors for quadrature generation.
In accordance with an exemplary embodiment of the invention, a single-end, active, internally matched, quadrature generation circuit 100 is shown in
The phase difference between the in-phase and quadrature output signals, Iout 70 and Qout 75, is ensured based on the transistor inherent characteristics of Qmain 30 and Qaux 50. When the (normalized) current gain between nodes 1 and 3 (RF input node and the node at the collector of Qmain 30) and the (normalized) current gain between nodes 1 and 2 (RF input node and the node at the base of Qaux 50) is equal or within 3 decibels (dB) of each other, then the output phase difference (phase difference between Iout 70 and Qout 75) is at or about 90 degrees. Perfect amplitude balance (|IRC|=|IRB|) occurs when the frequency f is given by:
At higher frequencies, when f>>fT/β (where fT is cutoff frequency of the transistor (on the order of 100 GHz, for example), and β is the dc gain current or collector current/base current), the ratio of IRC 37 to IRB 57 is given by:
As EQ. 2 illustrates, when EQ. 1 is true, then
IRC≈−jIRB [EQ. 3]
That is, IRC 37 and IRB 57 are 90 degrees apart in phase. Further, the quadrature (90 degree) relationship is achieved by the inherent characteristics between the collector and base alternating current (AC) (IRC 37 to IRB 57). To achieve a wide-band matching, the resistor values are selected such that:
In EQ. 4, gm is the transconductance of the transistors Qmain 30 and Qaux 50. In order to match the load impedance, RL 65, RC 35, and RB 55 can be chosen as:
RC≈RL [EQ. 5]
RB≈RL [EQ. 6]
In accordance with another exemplary embodiment of the invention, a differential, active, internally matched, quadrature generation circuit 200 is shown in
Some common features of the circuits according to the embodiments discussed with reference to
While the invention has been described with reference to exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiments disclosed, but that the invention will include all embodiments falling within the scope of the application.
Filing Document | Filing Date | Country | Kind |
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PCT/US2015/065378 | 12/11/2015 | WO | 00 |
Publishing Document | Publishing Date | Country | Kind |
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WO2017/099812 | 6/15/2017 | WO | A |
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Number | Date | Country | |
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20200266801 A1 | Aug 2020 | US |