Circuit for amplifying radio signal using high frequency

A high frequency amplifier circuit includes a transistor including a drain, a gate, and a source, an inductance-capacitor (LC) tank connected to the drain, and a transformer connected to the gate and the source.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application claims the priority benefit of Korean Patent Application No. 10-2016-0045743, filed on Apr. 14, 2016, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference for all purposes.

BACKGROUND

One or more example embodiments relate to a wireless communication apparatus, and more particularly, to a high frequency amplifying circuit for reducing occurrence of oscillation.

2. Description of Related Art

A high frequency amplifier circuit may include a transistor and a resonance load. However, due to a feature of a radio frequency (RF) corresponding to a high frequency, a stability may be reduced by a feedback effect caused by a parasite element of the transistor.

To solve a problem that the stability is reduced, several methods are proposed. A method of increasing a degree of isolation between an input end and an inductance-capacitance (LC) tank, a method of applying an additional negative feedback, and a method of compensating for a feedback factor are proposed.

However, the method of increasing the degree of isolation may require that a supply voltage should be as high as an operating condition of an additional transistor because the additional transistor is disposed on top of an original transistor such that an amount of power consumption increases. In addition, a gain may be reduced due to a signal leakage caused by a parasitic element increasing at a connection point between transistors.

The method of applying the additional negative feedback may have a disadvantage that a gain is reduced. As a result, a plurality of amplifying operations is required such that the amount of power consumption may increase. Also, an additional inductor is required except for a matching circuit of an input end. An increased area of the inductor may reduce an economic efficiency.

The method of compensating for the feedback factor may remove such effect from a resonance frequency by using a feedback capacitor CFand a feedback inductor LFcorresponding to a main factor that causes oscillation by reducing the stability. However, an operation bandwidth is relatively narrow because the method of compensating for the feedback factor is only performed at a resonance point of the feedback capacitor CFand the feedback inductor LF. In addition, a size of the feedback inductor LFmay increase based on a target frequency in order to compensate for a small size of the feedback capacitor CF. When an integrated circuit (IC) is manufactured, it may be difficult to include an inductor in the IC and the economic efficiency may be reduced due to the increased area of the inductor.

SUMMARY

An aspect provides a method and apparatus for reducing occurrence of oscillation using a transformer and simultaneously enhancing a stability and performance of a high frequency amplifier circuit.

According to an aspect, there is provided a high frequency amplifier circuit including a transistor including a drain, a gate, and a source, an inductance-capacitance (LC) tank connected to the drain, and a transformer connected to the gate and the source.

The transformer may include a first transformer including a second inductor connected to the gate and a third inductor connected to an input end of the high frequency amplifier circuit, and a second transformer including the third inductor and a fourth inductor connected to the source, and the second inductor and the fourth inductor have opposite polarities.

One terminal of the second inductor may be connected to a reference voltage and another terminal of the second inductor may be connected to the gate.

One terminal of the third inductor may be connected to an input end of the high frequency amplifier circuit and another terminal of the third inductor may be connected to a ground.

One terminal of the fourth inductor may be connected to the source and another terminal of the fourth inductor may be connected to a ground.

The high frequency amplifier circuit may have a perpendicular structure including a first layer and a second layer, and the second inductor and the third inductor may be included in the first layer and the fourth inductor may be included in the second layer.

The LC tank may include a first inductor and a first capacitor.

According to another aspect, there is provided a high frequency amplifier circuit including a first transistor including a first drain, a first gate, and a first source, and a second transistor including a second drain, a second gate, and a second source, a first inductance-capacitance (LC) tank connected to the first drain and a first output end, and a second LC tank connected to the second drain and a second output end, and a first transformer and a second transformer connected to the first gate, the first source, a first input end, the second gate, the second source, or a second input end, wherein the first input end and the second input end are included in a differential input end.

The first LC tank may include a first inductor and a first capacitor, and the second LC tank may include a second inductor and a second capacitor.

The first transformer may include a third inductor connected to the first gate and the second gate and a fourth inductor connected to the first input end and the second input end, the second transformer may include the fourth inductor and a fifth inductor connected to the first source and the second source, and the third inductor and the fifth inductor may have opposite polarities.

The high frequency amplifier circuit may have a perpendicular structure including a first layer and a second layer, and the third inductor and the fourth inductor may be included in the first layer and the fifth inductor may be included in the second layer.

According to still another aspect, there is provided a matching circuit including a first transistor, and a high frequency amplifier circuit connected to a first drain of the first transistor, wherein the high frequency amplifier circuit includes a second transistor including a second drain, a gate, and a source, an inductance-capacitor (LC) tank connected to the second drain and an output end, and a first transformer and a second transformer connected to the gate, the source, or the first drain.

The first transformer may include a second inductor connected to the gate and a third inductor connected to the first drain, the second transformer may include the third inductor and a fourth inductor connected to the source, and the second inductor and the fourth inductor may have opposite polarities.

The third inductor may be connected to a supply voltage.

The third inductor and the fourth inductor may be connected to a bypass capacitor.

DETAILED DESCRIPTION

Hereinafter, examples are described in detail with reference to the accompanying drawings. Like reference numerals in the drawings denote like elements, and a known function or configuration will be omitted herein.

FIG. 1is a diagram illustrating a high frequency amplifier circuit according to an example embodiment.

In an example, the high frequency amplifier circuit may operate at a high frequency to transmit a radio signal by amplifying the radio signal or amplify a received radio signal. In detail, the high frequency amplifier circuit may apply an input signal to an input end of the high frequency amplifier circuit. The input signal may be applied to a gate of a transistor and a resonance point of an inductance-capacitance (LC) tank connected to a drain of the transistor is matched to a high frequency signal such that an amplification gain may be obtained.

In this example, a stability of the high frequency amplifier circuit may be reduced by a feedback effect caused by a parasitic element of the transistor due to a high frequency. Thus, an oscillation phenomenon in which an output signal occurs may be caused even when an input signal is absent due to the feedback effect. The high frequency amplifier circuit may enhance the stability using a transformer disposed between the input end and the gate.

The high frequency amplifier circuit may operate at the high frequency to simultaneously achieve the stability and high performance. Here, the high performance may indicate good performance in an input/output matching feature, a noise feature, a gain, an output power, a linearity, and an amount of power consumption. The stability may indicate a degree of reducing the oscillation phenomenon.

In an example, a high frequency amplifier circuit100includes a transistor110, hereinafter also referred to as a transistor M1, an LC tank120, and a transformer130.

The high frequency amplifier circuit100may apply an input signal to an input end140of the high frequency amplifier circuit100. The LC tank120may be connected to a drain of the transistor110to match a resonance point to a high frequency signal. The transistor110may obtain an amplification gain using the input signal applied to the gate and the resonance point formed by the LC tank120. The transformer130may be connected between the gate and a source such that a stability of the high frequency amplifier circuit100is enhanced.

The transistor110includes a drain, a gate, and a source. For example, the transistor110includes a metal oxide semiconductor field effect transistor (MOSFET). The LC tank120may be connected to the drain. The LC tank120may include a first inductor L1and a first capacitor C1to form a resonance load. The first inductor L1, the first capacitor C1, and the drain may be connected to an output end150. The transformer130may be connected to the gate and the source.

The transformer130includes a first transformer T1including a second inductor Ls1connected to the gate and a third inductor Lpconnected to the input end140of the high frequency amplifier circuit100. The second inductor Ls1and the third inductor Lpmay be coupled by a mutual inductance. The transformer130may include a second transformer T2including the third inductor Lpand a fourth inductor Ls2connected to the source. The third inductor Lpand the fourth inductor Ls2may be coupled by the mutual inductance. The second inductor Ls1and the fourth inductor Ls2may have opposite polarities.

The fourth inductor Ls2may be connected to the source of the transistor110to apply a negative feedback to the transistor110. Thus, the stability may be enhanced such that a probability that oscillation occurs may be reduced. It may indicate that a real value of an input impedance is a positive value.

The third inductor Lpconnected to the input end140may form two transformers simultaneously. Thus, the first transformer T1and the second transformer T2are formed. The first transformer T1may include the third inductor Lpand the second inductor Ls1. The second transformer T2may include the third inductor Lpand the fourth inductor Ls2. The third inductor Lpand the second inductor Ls1may have a mutual inductance, and the third inductor Lpand the fourth inductor Ls2may have a mutual inductance.

Here, the fourth inductor Ls2and the second inductor Ls1connected to the third inductor Lpmay have opposite polarities. Thus, a phase of a signal of the gate coupled to the third inductor Lpbeing a first side of the first transformer T1and connected to the second inductor Ls1being a second side of the first transformer T1may differ, by 180 degrees, from a phase of a signal of the source coupled to the third inductor LTbeing a first side of the second transformer T2and connected to the fourth inductor Ls2being a second side of the second transformer T2.

An amplitude of a valid signal between the gate and the source of the transistor110may increase due to an amplitude difference caused by a difference between the phases. Thus, the high frequency amplifier circuit100may increase a gain using a manual element only without consuming additional power. The high frequency amplifier circuit100may obtain a maximum gain from the phase difference of 180 degrees, and the amplitude of the valid signal between the gate and the source of the transistor110may decrease as the phase difference differs from a value during one cycle.

FIG. 2is a diagram illustrating a perpendicular structure of a high frequency amplifier circuit according to an example embodiment.

FIG. 2is a top view and a cross-sectional view of the transformer130. A planar inductor may be implemented by twisting a metal line in an integrated circuit (IC) manufacturing process. The transformer130may be provided by laterally disposing inductors on a same layer, or disposing the inductors on or below different layers.

In an example, the transformer130has a perpendicular structure including a first layer and a second layer. A second inductor Ls1and a third inductor Lpmay be included in the first layer. A fourth layer Ls2may be included in the second layer. Thus, the second inductor Ls1and the third inductor Lpmay be included in a layer differing from a layer in which the fourth layer Ls2is included.

In detail, the third inductor Lpand the second inductor Ls1ofFIG. 2are disposed on a same layer inFIG. 2such that an edge side coupling may be used. The third inductor Lpand the fourth inductor Ls2ofFIG. 2are disposed on different layers such that a broad side coupling may be used. Here, the second inductor Ls1and the fourth inductor Ls2may be disposed to minimize an effect of the edge side coupling and an effect of the broad side coupling.

FIG. 3is a diagram illustrating a high frequency amplifier circuit configuration applied to a differential amplifier circuit according to an example embodiment.

In an example, a high frequency amplifier circuit300has a symmetrical structure of the high frequency amplifier circuit100ofFIG. 1. Through this, the high frequency amplifier circuit300may achieve a high stability and performance by removing a common mode portion of an input signal while amplifying a differential mode portion.

A first transformer T1includes a fourth inductor Lpand a third inductor Ls1. A second transformer T2includes a fourth inductor Lpand a fifth inductor Ls2. The high frequency amplifier circuit300is in a form of a differential amplifier circuit, and a negative terminal (second input end) and a positive terminal (first input end) instead of a ground terminal of a single amplifier circuit may perform a role of the single amplifier circuit. The fourth inductor Lpand the third inductor Ls1may form a mutual inductance, and the fourth inductor Lpand the fifth inductor Ls2may form a mutual inductance. Here, the fifth inductor Ls2and the third inductor Ls1connected to the fourth inductor Lpmay have opposite polarities.

The high frequency amplifier circuit300includes a first transistor311, a second transistor312, a first LC tank321, a second LC tank322, a transformer330, a differential input end340, and an output end350. The differential input end340includes a first input end and a second input end. The output end350includes a first output end and a second output end.

The first transistor311includes a first drain, a first gate, and a first source, and the second transistor312includes a second drain, a second gate, and a second source.

The first LC tank321may be connected to the first drain and the first output end. The second LC tank322may be connected to the second drain and the second output end. The first LC tank321includes a first inductor L1and a first capacitor C1, and the second LC tank322includes a second inductor L2and a second capacitor C2.

The transformer330includes the first transformer T1and the second transformer T2. The first transformer T1and the second transformer T2may be connected to the first gate, the first source, the first input end, the second gate, the second source, or the second input end. In detail, the first transformer T1includes the third inductor Ls1connected to the first gate and the second gate, and the fourth inductor Lpconnected to the first input end and the second input end. The second transformer T2includes the fourth inductor Lpand the fifth inductor Ls2connected to the first source and the second source. Here, the third inductor Ls1and the fifth inductor Ls2may have opposite polarities.

FIG. 4is a diagram illustrating a perpendicular structure of a high amplifier circuit applied to a differential amplifier circuit according to an example embodiment.

FIG. 4is a top view and a cross-sectional view of the transformer330. A planar inductor may be implemented by twisting a metal line in an integrated circuit (IC) manufacturing process. The transformer330may be provided by laterally disposing inductors on a same layer, or disposing the inductors on or below different layers. Such description is identical to the description provided with reference toFIG. 2. However, a symmetrical layout may be used to apply a structure of the transformer330to a structure of the differential amplifier circuit.

In an example, the transformer330has a perpendicular structure including a first layer and a second layer. A third inductor Ls1and a fourth inductor Lpare included in the first layer, and a fifth inductor Ls2is included in the second layer. Thus, the third inductor Ls1and the fourth inductor Lpmay be included in a layer differing from a layer in which the fifth layer Ls2is included.

In detail, the third inductor Ls1and the fourth inductor LpofFIG. 3are disposed on a same layer inFIG. 4such that an edge side coupling may be used. The fourth inductor Lpand the fifth inductor Ls2ofFIG. 3are disposed on different layers such that a broad side coupling may be used. Here, the third inductor Ls1and the fifth inductor Ls2may be disposed to minimize an effect of the edge side coupling and an effect of the broad side coupling.

FIG. 5Ais a diagram illustrating a high frequency amplifier circuit applied to a matching circuit according to an example embodiment, andFIG. 5Bis a diagram illustrating a high frequency amplifier circuit applied to a matching circuit according to another example embodiment.

In an example, a high frequency amplifier circuit may be used as an inter stage matching circuit.FIGS. 5A and 5Billustrate two examples in which the high frequency amplifier circuit is used as the inter stage matching circuit.

When a transformer including a second inductor Ls1and a fourth inductor Ls2is used, current conversion or voltage conversion of a first side and a second side may be adjusted such that a signal of a first transistor550may be effectively transferred to the second transistor110, hereinafter also referred to as a second transistor M2. In a structure of a general common source, oscillation caused by a radio frequency (RF) of an inductor load connected to a drain of a transistor may be reduced by controlling a first transformer T1or a second transformer T2. An area of each of a third inductor Lp, a second inductor Ls1, and a fourth inductor Ls2may not greatly increase compared to a size of a single inductor because the third inductor Lp, the second inductor Ls1, and the fourth inductor Ls2are provided in an overlapping structure.

The inter stage matching circuit may include the high frequency amplifier circuit connected to a first drain of the first transistor550. The high frequency amplifier circuit includes the second transistor110including a second drain, a second gate, and a second source, and the LC tank120connected to the second drain and the output end140.

The high frequency amplifier circuit includes the first transformer T1and the second transformer T2connected to the source, the gate of the first transistor550, or a first drain of the second transistor110. In detail, the first transformer T1includes the second inductor Ls1connected to the gate and the third inductor Lpconnected to the first drain. The second transformer T2includes the third inductor Lpand the fourth inductor Ls2connected to the source. Here, the second inductor Ls1and the fourth inductor Ls2may have opposite polarities.

The third inductor Lpmay be connected to the first drain of the first transistor550included in a first end to perform a role of a load of the first transistor550. Simultaneously, the third inductor Lpmay perform a role of the first transformer T1and the second transformer T2provided with the second inductor Ls1and the fourth inductor Ls2such that a signal from the first transistor550to a second end including the second transistor110.

In an example, the third inductor Lpof the inter stage matching circuit ofFIG. 5Amay be connected to a supply voltage. In detail, a terminal of the third inductor Lpmay be connected to a supply voltage VDD561, and the first transistor550and the second transistor110may have distinguished current paths. Referring toFIG. 5A, a matching circuit may consume a great amount of power but there is a sufficient space for swinging a voltage whereby having a relatively great linearity.

In another example, referring toFIG. 5B, the third inductor Lpand the fourth inductor Ls2of the inter stage matching circuit may be connected to a bypass capacitor562, hereinafter also referred to as a bypass capacitor Cs. In detail, one terminal of the third inductor Lpmay be connected to the fourth inductor Ls2. A current used by the second transistor110may be reused by the first transistor550when a connected portion is reconnected to the bypass capacitor562.

According to an example embodiment, it is possible to reduce occurrence of oscillation using a transformer and simultaneously enhance a stability and performance of a high frequency amplifier circuit.

The components described in the exemplary embodiments of the present invention may be achieved by hardware components including at least one DSP (Digital Signal Processor), a processor, a controller, an ASIC (Application Specific Integrated Circuit), a programmable logic element such as an FPGA (Field Programmable Gate Array), other electronic devices, and combinations thereof. At least some of the functions or the processes described in the exemplary embodiments of the present invention may be achieved by software, and the software may be recorded on a recording medium. The components, the functions, and the processes described in the exemplary embodiments of the present invention may be achieved by a combination of hardware and software.