Power measurement via bond wire coupling

A device includes an output circuit that includes an input port at which a signal is received, an output port at which an impedance-adjusted representation of the signal is provided, and a set of bond wires connecting the input and output ports. The device further includes first and second couplers, each including a respective coupling bond wire along the set of bond wires for inductive coupling with the set of bond wires. The first coupler is oriented relative to the distributed-element output circuit to measure forward power provided by the impedance-adjusted representation of the signal via the output port. The second coupler is oriented relative to the output circuit to measure reflected power received via the output port.

FIELD OF INVENTION

The present embodiments relate to amplifiers.

BACKGROUND

Amplifiers use power transistor devices to develop an amplified version of an input signal. The input signal is often modulated to carry information. To avoid distortion or other loss of the information, the power transistor device is configured and operated to amplify the input signal in a linear manner.

Power transistor devices are often controlled to improve operational characteristics. For instance, a power transistor device may be controlled to limit the input signal or bias voltages to levels at which the power transistor device operates in an efficient and linear manner. In linearization control schemes, the output power of the power transistor device is often monitored. Output monitoring is used to ensure that the modulation component of the input signal in the amplified output signal is acceptably linear.

Radio frequency (RF) power couplers are used for power monitoring. Some RF power couplers are installed to monitor the forward power delivered to the load. The forward power level measurement may then be used in a feedback loop to control the power transistor device.

RF power couplers are also installed to monitor the reflected power from the load. Such monitoring may be used to protect the power transistor devices from failure during output mismatch. Output mismatch arises with an offset in the output impedance of the amplifier and the input impedance of the load. The amount of output mismatch is identified by monitoring the power reflected from an output load.

RF power couplers often use distributed transmission lines and lumped-element networks. In such cases, the transmission lines may become undesirably long in connection with, for instance, quarter-wavelength transmission lines. For example, a transmission line on the surface of a substrate with a limited dielectric constant can be relatively long for an operating frequency of 2 Gigahertz (GHz). Even with a substrate having a relatively high permittivity, for example, a permittivity equal to about 10, a transmission line length will be of the order of 20 millimeters (mm).

For these reasons, RF power couplers have consumed a significant amount of space, e.g., on a printed circuit board. RF power couplers may also introduce undesirably long time delays in the output signal when being used for power control or linearization.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

Embodiments of power measurement devices with bond wire-based couplers are described, along with methods of measuring power with coupling bond wires. The devices include power measurement (or monitoring) devices, or power sensors, as well as power amplifier devices including such power measurement devices or power sensors. The power measurement devices include two couplers: one coupler for monitoring forward power and another coupler for monitoring reflected power. Each coupler includes a coupling bond wire inductively coupled to a set of bond wires connecting input and output ports of the power measurement device.

The bond wire-based couplers of the disclosed devices allow a bidirectional coupler to be realized in a compact and effective manner. For instance, both forward power and reflected power are monitored with high directivity, or isolation between forward and reflected power output ports. Effective monitoring of both forward power and reflected power is also achieved without relying on lumped elements in either the bond wire-based couplers or an output circuit (e.g., an impedance adjustment circuit or impedance matching circuit) with which the bond wire-based couplers are inductively coupled. For instance, neither the output circuit nor the bond wire-based couplers rely on adding lumped elements. Instead, the intrinsic and parasitic capacitance or inductance of the devices is sufficient. The output circuit and the bond wire-based couplers are accordingly capable of being fabricated and assembled in a compact manner.

The use of the intrinsic and parasitic inductances and capacitances present in the devices allows the amplifier devices, and the power measurement devices thereof, to be provided as a discrete, packaged device. For example, the amplifier device may be provided with integrated power measurement in a single, discrete RF power module. A device with a compact form factor may thus be attained.

The amplifier devices may be used in connection with RF power in the microwave bands, such as power at about 2.45 GHz (or other frequencies) for microwave heating. However, the disclosed devices are well suited for use in a wide variety of other applications and usage scenarios, including applications at other frequencies. For instance, the RF power amplified and otherwise handled by the disclosed devices may be used in various types of communication applications. The forward and reflected power may accordingly be representative of information or content via various modulation schemes.

The amplifier devices described below may be used in applications involving multiple amplifier devices, such as microwave systems. For example, a heating cavity of a microwave system may use four power amplifiers, or some other number of power amplifiers. In such cases, a non-operational one of the power amplifier devices may be especially susceptible to damage when all of the other power amplifiers are operational. The reflected power measurements may alternatively or additionally be representative of power delivered by the other power amplifiers but not absorbed by the load.

FIG. 1depicts an amplifier device100in accordance with one example. The amplifier device100may be a power amplifier device configured to amplify RF signals. The amplifier device100may be a discrete device. In the example ofFIG. 1, the device100is enclosed in a package102, e.g., as a packaged semiconductor device. The package102may be an overmolded package with a lead frame having one or more die pads on which components of the amplifier device100are mounted. Alternatively, the package102may be an air cavity package with a flange on which components of the amplifier device100are mounted, and leads that provide electrical connectivity with circuits outside of the air cavity. The assembly of the components of the device100within the package102and other characteristics of the package102may vary. One or more components of the device100may be implemented in semiconductor die, and/or may be discrete devices (e.g., discrete, packaged devices) disposed within the package102.

The device100includes a transistor device104. The transistor device104may be a power transistor device. The transistor device104may be realized on a semiconductor die. The transistor device104may be integrated with one or more other components of the device100. In some cases, the transistor device104may be or include one or more field-effect transistor (FET) devices, such as a laterally-diffused metal-oxide-semiconductor (LDMOS) transistor device. Other types of FET devices may be used, including, for instance, heterojunction FET (HFET) devices and other types of high electron mobility transistor (HEMT) devices. Alternatively, the transistor device104is or includes a bipolar junction transistor (BJT) device. Still other types of transistor devices may be used, including, for instance, heterojunction bipolar transistor (HBT) devices. The configuration, construction, and other characteristics of the transistor device102may vary.

The transistor device104is connected to an input lead or other input terminal106of the device100via an input circuit108. An RF signal to be amplified by the device100is received at the input terminal106. The input circuit108may be or include an input matching circuit. The input matching circuit may be configured to match (e.g., sufficiently match) the input impedance of the device100to the output impedance of a source of the RF signal received at the input terminal106. Other types of pre-matching circuits may be used. In various embodiments, all or portions of the input circuit108may be integrated with the transistor device104or may be formed from components that are distinct from the transistor device104. Alternatively, the transistor device104is configured to present an input impedance that matches the output impedance of the signal source, or vice versa.

The transistor device104is configured to generate an amplified representation of an input signal received at the input terminal106(“the amplified signal”). The input signal may be a voltage signal or a current signal. In some cases, the transistor device104is configured for operation as a transconductance amplifier such that the amplified signal is a current signal generated from an input voltage signal. In other cases, the amplified signal is a voltage signal. The term “signal” is used herein in a broad sense to include any type of electrical waveform regardless of whether the waveform is modulated or otherwise indicative of information.

The amplifier device100includes an output circuit110coupled to the transistor device104to receive the amplified signal. The output circuit110includes an impedance adjustment circuit, an input port112at which the amplified signal is received, and an output port114at which an impedance-adjusted representation of the amplified signal is provided. The impedance adjustment provided by the circuit110may, for instance, address the low output impedance of the transistor device104in connection with a load having a higher input impedance. In that case, the output circuit110establishes a different (e.g., higher) output impedance for the amplifier device100. As will be described later in conjunction withFIG. 2, the output circuit110includes a plurality of bond wires (e.g., bond wires136,FIG. 2) that convey signals between the transistor device104and an output port116.

In the example ofFIG. 1, an output terminal of the transistor device104is electrically tied to the input port112of the output circuit110. In other cases, the transistor device104and the output circuit110are coupled to one another by an intervening circuit, network, or other element.

The amplifier device100includes an output port116to which the output circuit110is coupled. The output port116may be an output pin, lead, or other node to which a load to be driven by the amplifier device100can be connected. In the example ofFIG. 1, the output port116corresponds with the output port114of the output circuit110. In other cases, one or more intervening circuits, networks, or other elements may be disposed between the output port114of the output circuit110and the output port116of the amplifier device100.

The output circuit110may be or include an impedance matching circuit configured to establish an impedance of the amplifier device100. The impedance may be an output impedance for the output port112of the amplifier device100. A load attached or otherwise coupled to the output port112exhibits an input impedance that may be lower or higher than the output impedance of the transistor device104. The output circuit110is then configured to adjust the output impedance of the amplifier device100at the output port112to match the input impedance of the load. The terms “match” and any derivatives thereof are used in a broad sense to include impedances that are not exactly equal.

In the example ofFIG. 1, the output circuit110is a distributed-element circuit. For example, the output circuit110does not include lumped elements, such as lumped element capacitors or lumped element resistors. The output circuit110thus establishes the impedance of the output port112without relying on lumped elements. For instance, the output circuit110does not rely on or otherwise introduce a lumped element-based phase shift between the signal generated by the transistor device104and the impedance-adjusted representation at the output port112. The absence of lumped elements allows the output circuit110and the amplifier device100to be more compactly realized.

The output circuit110relies upon distributed elements rather than lumped elements to implement the impedance matching or other adjustment. The distributed elements may be intrinsic to the construction of the output circuit and/or parasitic in nature. As described below, at least one inductance of the output circuit110is provided by a set of bond wires. Capacitance of the output circuit110is provided by the parasitic capacitance between structural components of the output circuit110and a ground plane.

The output circuit110may be configured for impedance matching at a desired frequency or within a desired frequency range. In one example, the output circuit110is configured for impedance matching at a frequency of about 2.45 GHz, which corresponds with the frequency used in microwave heating applications. The frequency may vary, e.g., in accordance with the application, the load, or other usage scenario for the amplifier device100. For instance, in other applications, the frequency may be above about 1.0 GHz. Other frequency ranges may include, for example, about 4.45 gigahertz (GHz)+/−5 percent. In one embodiment, for example, the frequency falls in a range of about 4.40 GHz to about 4.50 GHz.

The amplifier device100includes a pair of couplers120,122for power monitoring, in an embodiment. Each coupler120,122includes a respective bond wire124(or multiple bond wires) for inductive coupling with the output circuit110. The coupler120is oriented relative to the output circuit110to measure forward power provided by the impedance-adjusted representation of the signal via the output ports114,116. The coupler122is oriented relative to the output circuit110to measure reflected power received via the output ports114,116. The orientations of the couplers120,122are further described below in connection with measurement port and termination locations.

Each coupler120,122includes a respective measurement port126,128connected to one end of the respective coupling bond wire(s)124. The end to which the measurement port126,128is connected depends on whether forward or reflected power is being monitored. A signal indicative of the forward power is provided at the measurement port126. As shown inFIG. 1, the measurement port126is connected to a proximal end of one of the bond wires124. A signal indicative of the reflected power is provided at the measurement port128. As shown inFIG. 1, the measurement port128is connected to a distal end of the other one of the bond wires124. In the example ofFIG. 1, the measurement ports126,128are configured as output ports of the amplifier device100. The measurement ports126,128may be configured as pins, leads, or other output elements at which signals indicative of the forward and reflected power are made available.

Each coupler120,122includes a respective termination130,132. Each termination130,132is connected at the other end of the respective coupling bond wire124as shown inFIG. 1. Each termination130,132may be configured as an impedance connected to ground. In some cases, ground is provided as a plane, such as a back plane of the package102or a conductive flange to which the components of device100are coupled. The ground connection may vary in accordance with the construction of the packaging102and other structural characteristics of the amplifier device102.

The amount of impedance associated with each termination130,132may be selected in accordance with one or more characteristics of the amplifier device100, including, for instance, the impedance of the couplers120,122. For example, the impedance of each termination may fall in a range from about 100 Ohms to about 600 Ohms, such as about 350 Ohms, although the impedance may be higher or lower, as well.

The use of two distinct couplers120,122allows for accurate and trouble-free measurement of both forward and reflected power. For instance, having a separate coupler for each measurement avoids having to rely on a phase differential to provide both measurements. The couplers120,122may also have higher directivity than other techniques that rely on a single coupling to provide both forward and reflected power.

The couplers120,122are useful in additional ways. For example, the couplers120,122may be smaller than couplers utilizing discrete components or couplers that rely on a quarter-wavelength phase difference to measure both forward and reflected power. The configuration of the couplers120,122may also help integrate the measurement components fit into particular applications or package implementations. The couplers120,122also provide flexibility in the opportunity to adjust the terminations130,132for use with different frequencies, thereby avoiding a redesign of the coupling spacing, bond wire length, and other component parameters or characteristics. The disclosed devices are thus compatible with a wide variety of applications and usage scenarios.

In the example ofFIG. 1, the couplers120,122are integrated within the package102. The couplers120,122may thus be enclosed in a package or otherwise integrated with the transistor device104and other components of the amplifier device100. In other cases, one or more components of the amplifier device100are not disposed within the packaging102. In such cases, each packaged, discrete component of the amplifier device100, including the packaged device including the transistor device104, may be disposed on a printed circuit board (PCB). For example, the components shown inFIG. 1may be enclosed in the package102, while one or more control circuits of the amplifier device100, such as a feedback circuit responsive to the forward and/or reflected power, are separately housed and mounted on the PCB.

The couplers120,122and the output circuit110may be considered a coupler device134for the transistor device104. Each of the output circuit110and the couplers120,122couples an output or other signal associated with the transistor device104to a respective one of the ports116,126,128. Further details regarding the construction and assembly of the coupler device134are provided below in connection withFIG. 2.

FIG. 2depicts a coupler device134in accordance with one example in greater detail. The packaging102is not shown for ease in illustration of the components of the coupler device134. The impedance adjustment elements of the coupler device134include a set of bond wires136. Each bond wire136connects a die pad138and a packaging lead140, which, in this example, correspond with the input port112of the output circuit110and the output port116of the amplifier device (FIG. 1). The bond wires136collectively provide a distributed inductance of the output circuit110. A distributed capacitance of the output circuit110is provided by a parasitic capacitance between the die pad138and ground, such as the ground plane of the package102(FIG. 1).

The die pad138may constitute part of a transistor die on which the transistor device104(FIG. 1) is disposed or otherwise formed. For example, the die pad138may be or include one or more bond pads located along a periphery of the die. In some cases, the die pad138includes a metal layer supported by a substrate of the die. The metal layer may be spaced from a backside or other ground plane to establish the parasitic capacitance of the output circuit110(FIG. 1). In an embodiment, the die pad138is coupled to a current conducting terminal (e.g., a drain, in FET terminology) of the transistor device104.

In the example ofFIG. 2, the packaging lead140includes a rigid conductive structure that extends laterally outward from the package102(FIG. 1). In other examples, the coupler device134and, more generally, the amplifier device100(FIG. 1) may have an output port or terminal that has a different construction or configuration. For instance, one or more pins or pads may be used to provide the output of the coupler device134and, more generally, the amplifier device100(FIG. 1).

FIG. 2depicts the bond wires124of the couplers120,122in greater detail. Each bond wire124is positioned and configured to act as a coupling bond wire. As shown inFIG. 2, each bond wire124is positioned and oriented along the set of bond wires136of the output circuit110(FIG. 1). The positioning and orientation establishes the inductive coupling between the set of bond wires136and the bond wires124. For instance, in some cases, the bond wires124,126may be oriented such that more than one bond wire124may be used for each coupler120,122. The bond wires124may thus be in locations other than those shown in the example ofFIG. 2. For instance, the bond wires124may be disposed above, below, and/or interdigitated with the bond wires136.

The bond wires124may be disposed on opposite ends (or sides) of the set of bond wires136and, thus, more generally, the output circuit110(FIG. 1). As shown in the example ofFIG. 2, the bond wire124for the coupler120is disposed along an end or side140of the array of bond wires136. The bond wire124for the coupler122is disposed along an end or side141of the array of bond wires136opposite the end140. In this way, the bond wires124for the couplers120,122are adjacent to two different wire bonds136. Also, the bond wires124are sufficiently spaced from one another to avoid any inductive coupling between the bond wires124.

The measurement ports126,128of the couplers120,122are also shown in greater detail inFIG. 2. The measurement port126is connected to an end142of the bond wire124of the coupler120located adjacent the die bond pad138. The measurement port128is connected to an end144of the bond wire124of the coupler122. The terminations130,132of the couplers120,122are connected at ends of the bond wires124opposite those identified above.

The connections between the bond wires124and the measurement ports126,128may be established at respective bond pads or other conductive structures146,148. In some cases, the conductive structures146,148are parts of a packaging lead frame. A variety of other types of conductive structures and connections may be used, such as pins, pads, or other structures.

Each measurement port126,128may include a transmission line150that extends laterally in a direction perpendicular to an orientation of the respective coupling bond wire124. The perpendicular orientation of the transmission lines150avoids or minimizes any inductive coupling of the transmission lines150and the bond wires124,136. In the example ofFIG. 2, each transmission line150is or includes a packaging lead or pin. The transmission line150may be configured or constructed differently from the example shown. For example, the transmission line150may be or include a bond wire, trace, or other conductive element.

The bond wires124of the couplers120,122may have a configuration in common with each bond wire136of the output circuit110(FIG. 1). For instance, the bond wires124,136may have the same diameter, composition, length (or span), and/or height (or vertical deflection). In some cases, the bond wires124,136have a diameter of about 2 mils, an aluminum or gold composition, a length of about 60 mils, and a height of about 9 mils. But these and other parameters or characteristics may vary considerably.

One or more characteristics of the bond wires124may differ from the bond wires136. For instance, adjacent bond wires136may be spaced apart by a distance shorter than a spacing between each bond wire124and the closest bond wire136, or alternatively by a distance longer than a spacing between each bond wire124and the closest bond wire136. In addition, the heights of bond wires124may be different from the heights of bond wires136. In one example, the spacing of adjacent bond wires136is about 8 mils, while the spacing between the bond wire124and closest bond wire134is about 10 mils. These and other dimensions may be set to attain a desired amount of coupling for the couplers120,122and/or inductance in the output circuit110(FIG. 1). The dimensions may vary from the above examples for these and other reasons. For instance, the distances between the bond wires124,136may vary by +/−5% or more.

The configuration of the bond wires136and other components of the coupler134may exhibit sufficient power coupling for the couplers120,122, but without introducing a significant phase difference between the input port112(FIG. 1) and the output port114(or116). For example, the phase difference between the input and output ports112,114may be less than about 10 degrees (e.g., about 9 degrees), although it may be more than 10 degrees, as well.

The use of the intrinsic and parasitic inductance and capacitance of the bond wire arrangement allows the impedance of the input port112(FIG. 1) to be fairly low. For example, the input port impedance may be about 10 Ohms, or some other value. That impedance may be sufficiently close to the output impedance of the transistor device104(FIG. 1).

FIG. 3shows a method300of measuring forward power and reflected power for a power amplifier device. The method may be implemented using one or more of the above-described devices. The method includes a sequence of acts, only the salient of which are depicted for convenience in illustration.

The method300may begin with one or more acts directed to providing the above-described devices. For example, an amplifier device configured in accordance with one of the above-described examples may be connected and configured for operation with a load. The connections may include connections at the above-described input and output ports as well as at other ports or terminals, such as bias voltage terminal connections. The connections may also include connections at two ports for power measurement or monitoring of forward and reflected power.

The method300may alternatively or additionally begin with one or more acts directed to providing an input signal. The input signal may be provided by one or more signal sources. Multiple signal sources may be used to provide a composite input signal having an RF signals modulated with one or more low frequency (e.g., DC) signals.

The method300includes an act302in which an amplified signal is generated with a transistor device of the power amplifier based on an input signal (e.g., a signal provided to a gate of the transistor device, in FET terms). In some cases, the amplified signal may be a current signal generated from a control voltage or current. The act302may include applying a bias voltage to the transistor device. The act302may also include implementing various control schemes. For instance, a control scheme may be directed to setting the bias voltage and/or controlling the input signal.

An output impedance of the power amplifier is adjusted for the generated signal in an act304via a distributed-element impedance matching circuit. The output impedance adjustment may involve or include matching an impedance of a load. The matching or other adjustment is realized without a lumped element-based phase shift in the generated signal. As described above, lumped elements are not relied upon to implement the impedance adjustment and/or phasing. Instead, the matching or other adjustment is achieved with one of the above-described bond wire-based circuits. The intrinsic inductance of the bond wires and parasitic capacitance of the circuits is capable of attaining a desired impedance adjustment for a selected frequency or frequency range, such as 2.45 GHz or some other frequency.

Measurements of forward and reflected power are developed in acts308,310. The measurements are developed using the inductive coupling of respective coupling bond wires with the set of bond wires of the inductance adjustment circuit. The acts308,310may thus be concurrently implemented with the acts304. The forward and reflected power measurements are provided at respective measurement ports, as described above.

In the example shown inFIG. 3, the power measurements are used in an act312to analyze one or more parameters indicative of the operation of power amplifier device. The parameter(s) are then used to further adjust the output impedance or otherwise control operation in an act314. For example, the act312may include calculating a reflected to forward power ratio with the measurements obtained in the acts308,310, and comparing the ratio with a threshold. If the threshold is exceeded, then the output impedance is further adjusted in the act314. Examples of these and other applications of the power measurements are provided in connection withFIGS. 4 and 5. The act312may include or involve alternative or additional calculations and analyses, and the act314may include alternative or additional control adjustments.

The ordering of the acts may vary in other embodiments. For example, the output generation of the act302may follow the development of the power measurements in cases in which the power measurements are used to configure or otherwise control the operation of the power amplifier device.

Additional, fewer, or alternative acts may be implemented. For example, the method300may include one or more acts directed to using the forward and reflected power measurements.

Embodiments of a power amplifier device (e.g., amplifier device100) and/or embodiments of an RF coupler device (e.g., coupler device134) may be incorporated into various types of systems. For example, but not by way of limitation, such embodiments may be incorporated into RF solid-state heating systems (e.g., system400,FIG. 4), as or in connection with power detection circuits or circuitry of such systems in accordance with various example embodiments.

FIG. 4is a simplified block diagram of a solid-state heating system400that includes one or more amplifier devices (e.g., amplifier device100) or and/or coupler devices (e.g., coupler device134), in accordance with an example embodiment. Solid-state heating system400includes heating cavity410, user interface420, N microwave energy radiators430-432(e.g., N may be any integer from 4 to 10 or more), RF signal generator440, N microwave generation modules450-452, N power detection circuits460-462, a processing unit480, power supply and bias circuitry486, and memory488, in an embodiment. In addition, in some embodiments, solid-state heating system400may include temperature sensor(s), infrared (IR) sensor(s), and/or weight sensor(s)490, although some or all of these sensor components may be excluded. It should be understood thatFIG. 4is a simplified representation of a solid-state heating system400for purposes of explanation and ease of description, and that practical embodiments may include other devices and components to provide additional functions and features, and/or the solid-state heating system400may be part of a larger electrical system.

Heating cavity410, which is configured to contain a load412to be heated, is defined by the interior surfaces of bottom, top, and side walls. According to an embodiment, the cavity410may be sealed (e.g., with a door) to contain the electromagnetic energy that is introduced into the cavity410during a heating operation. The system400may include one or more interlock mechanisms that ensure that the seal is intact during a heating operation. If one or more of the interlock mechanisms indicates that the seal is breached, the processing unit480may cease the heating operation.

Heating cavity410and any load412(e.g., food, liquids, and so on) positioned in the heating cavity410present a cumulative load for the electromagnetic energy (or RF power) that is radiated into the cavity410by the N microwave energy radiators430-432. More specifically, the cavity410and the load412present an impedance to the system, referred to herein as a “cavity input impedance.” The cavity input impedance changes during a heating operation as the temperature of the load412increases.

User interface420may include a control panel, for example, which enables a user to provide inputs to the system regarding parameters for a heating operation (e.g., characteristics of the load to be heated, duration of heating operation, and so on), start and cancel buttons, mechanical controls (e.g., a door/drawer open latch), and so on. In addition, the user interface420may be configured to provide user-perceptible outputs indicating the status of a heating operation (e.g., a countdown timer, visible indicia indicating progress or completion of the heating operation, and/or audible tones indicating completion of the heating operation) and other information. In some embodiments, communication with the system400also may be implemented using a data port422, which may be configured to convey commands and other information between an external system (e.g., external computer180,FIG. 1) and the system400(e.g., the processing unit480).

Processing unit480may include one or more general purpose or special purpose processors (e.g., a microprocessor, microcontroller, Application Specific Integrated Circuit (ASIC), and so on), volatile and/or non-volatile memory (e.g., Random Access Memory (RAM), Read Only Memory (ROM), flash, various registers, and so on), one or more communication busses, and other components. According to an embodiment, processing unit480is coupled to user interface420, data port422(if included), RF signal generator440, microwave power generation modules450-452, power detection circuits460-462, power supply and bias circuitry486, and sensors490(if included). Processing unit480is configured to receive signals indicating inputs received via user interface420and/or port422, to receive signals indicating temperature and/or weight via sensors490(when included), and to receive forward and reflected power measurements from power detection circuit460-462over connections463-465. Based on the input signals received from user interface420, port422, and sensors490, processing unit480determines a combination of excitation signal parameters, and provides control signals to the RF signal generator440and microwave generation modules450-452, which indicate the one or more determined excitation signal parameters. As used herein, an “excitation signal” is an RF signal provided by any microwave power generation module450-452over a connection456-458to a microwave energy radiator430-432. An “excitation signal parameter” is an electrical characteristic of an excitation signal, including but not by way of limitation, a frequency of an excitation signal, a phase shift of an excitation signal with respect to another instance of the excitation signal, a power level of an excitation signal, or another electrical characteristic of an excitation signal.

For example, an excitation signal parameter may be a frequency or a range of frequencies at which the RF signal generator440should provide RF signals to the microwave power generation modules450-452. Upon determining a frequency or range of frequencies based on the input signals received from user interface420, port422, and/or sensors490, processing unit480may provide a control signal to RF signal generator440indicating the determined frequency or range of frequencies. In response to the received control signal(s), the RF signal generator440produces an excitation signal at the indicated frequency or within the indicated range of frequencies. According to an embodiment, the RF signal generator440may be configured to produce an oscillating electrical signal having a frequency in the ISM (industrial, scientific, and medical) band, although the system could be modified to support operations in other frequency bands, as well. In the illustrated embodiment, only a single RF signal generator440is shown. In alternate embodiments, system400may include multiple RF signal generators (e.g., N RF signal generators), each of which receive control signals from the processing unit480. Either way, each RF signal generator440may be controlled to produce oscillating signals of different power levels and/or different frequencies, in various embodiments. For example, the RF signal generator440may produce a signal that oscillates above about 1.0 GHz. Some desirable frequency ranges may include, for example, about 4.45 gigahertz (GHz)+/−5 percent. In one particular embodiment, for example, the RF signal generator440may produce a signal that oscillates in a range of about 4.40 GHz to about 4.50 GHz and at a power level in a range of about 10 decibels (dB) to about 15 dB. Alternatively, the frequency of oscillation and/or the power level may be lower or higher than the above-given ranges or values.

In addition to excitation signal frequency, an excitation signal parameter may be a phase shift to be applied by a microwave power generation module450-452to an excitation signal received from the RF signal generator440. In an embodiment, each microwave power generation module450-452includes a variable phase shifter454(only one shown) coupled in series with an amplifier455(only one shown). Upon determining phase shifts for each of the microwave generation modules450-452based on the input signals received from user interface420, port422, and/or sensors490, processing unit480may provide control signals to the phase shifter454within each of the microwave power generation modules450-452over connections482-484, which indicate phase shifts to be applied by the phase shifters454to the RF signals received from the RF signal generator440. In response to the received control signal(s), the phase shifters454apply corresponding phase shifts to the excitation signals received from the RF signal generator440.

FIG. 4shows the variable phase shifter454having an input coupled to the RF signal generator440, and an output coupled to the amplifier455(i.e., the phase shifter454is coupled between the generator440and the amplifier455). In an alternate embodiment, the amplifier455may be coupled between the RF signal generator440and the variable phase shifter454(i.e., an input to the amplifier455may be coupled to the signal generator440, and an output of the amplifier455may be coupled to the input to the phase shifter454). Either way, the input of each microwave power generation module450-452is coupled to the RF signal generator440, and the output each microwave power generation module450-452is coupled to a microwave energy radiator430-432through a transmission line456-458.

In the illustrated series configuration, the variable phase shifter454is configured to receive an RF signal from the RF signal generator440, and to apply a phase shift to the signal that corresponds to a phase shift indicated in a control signal received over one of connections482-484from the processing unit480. The amplifier455receives the phase shifted RF signal from the variable phase shifter454(or an unshifted signal if a phase shift of 0 degrees was imparted), and amplifies the RF signal to produce an amplified and potentially phase shifted output RF signal. Each amplifier455may be implemented using any of a variety of amplifier topologies. For example, each amplifier455may include various embodiments of a single ended amplifier, a double ended amplifier, a push-pull amplifier, a Doherty amplifier, a Switch Mode Power Amplifier (SMPA), or another type of amplifier.

Each power amplifier455may be implemented as a single-stage or a multi-stage power amplifier (e.g., including a driver amplifier stage and a final amplifier stage). The power amplifier455is configured to receive the oscillating signal from the variable phase shifter454(or from the RF signal generator440if the series configuration is reversed), and to amplify the signal to produce a significantly higher-power signal at an output of the power amplifier455. For example, the output signal may have a power level in a range of about 100 watts to about 400 watts or more.

The gain applied by the power amplifier455may be controlled using gate bias voltages and/or drain supply voltages provided by the power supply and bias circuitry486to each stage of the amplifier455. More specifically, power supply and bias circuitry486may provide bias and supply voltages to each RF amplifier stage in accordance with control signals received from processing unit480. Thus, according to a further embodiment, processing unit480may provide control signals to power supply and bias circuitry486, which cause the circuitry486to adjust the gate and/or drain bias voltages provided to amplifiers455within the microwave power generation modules450-452.

In an embodiment, each amplifier stage is implemented as a power transistor, such as a field effect transistor (FET), having an input terminal (e.g., a gate or control terminal) and two current carrying terminals (e.g., source and drain terminals). For a single stage amplifier, impedance matching circuits (not illustrated) may be coupled to the input (e.g., gate) of the single amplifier stage, and/or to the output (e.g., drain terminal) of the single amplifier stage. For a two-stage amplifier, impedance matching circuits (not illustrated) may be coupled to the input (e.g., gate) of the driver amplifier stage, between the driver and final amplifier stages, and/or to the output (e.g., drain terminal) of the final amplifier stage, in various embodiments. In an embodiment, the power transistor of each amplifier stage includes a laterally diffused metal oxide semiconductor FET (LDMOSFET) transistor. However, it should be noted that the transistors are not intended to be limited to any particular semiconductor technology, and in other embodiments, each transistor may be realized as a gallium nitride (GaN) transistor, another type of MOSFET transistor, a bipolar junction transistor (BJT), or a transistor utilizing another semiconductor technology.

Each amplified and potentially phase shifted RF signal produced by a microwave power generation module450-452is provided over a transmission path456-458to one of the N microwave energy radiators430-432. For example, each of the transmission paths456-458may include an impedance matching network and a conductor (e.g., a coaxial cable or other type of conductor).

According to an embodiment, a power detection circuit460-462is coupled along each transmission path456-458between the output of each microwave power generation module450-452and the input to each microwave energy radiator430-432. For example, each power detection circuit460-462may include a coupler device (e.g., coupler device134). Each power detection circuit460-462is configured to monitor, measure, or otherwise detect the power of the forward signals (i.e., from one of the microwave generation modules450-452toward one of the N microwave energy radiators430-432), and the power of the reflected signals (i.e., from one of the N microwave energy radiators430-432toward one of the microwave generation modules450-252) traveling along the transmission paths456-458.

Power detection circuits460-462supply signals conveying the magnitudes of the forward and reflected signal power (and possibly the forward signal power) to processing unit480over connections463-465. For example, referring also toFIGS. 1 and 2, the signals may be conveyed through ports126,128, as previously discussed. Processing unit480, in turn, may calculate a ratio of reflected signal power to forward signal power and/or return loss from the received measurements. The processing unit480may then modify RF excitation signal parameters in order to find combinations of excitation signal parameters that result in acceptable or optimal reflected power and/or return loss.

As mentioned above, some embodiments of solid-state heating system400may include temperature sensor(s), IR sensor(s), and/or weight sensor(s)490that may be useful in determining load characteristics. The temperature sensor(s) and/or IR sensor(s) may be positioned in locations that enable the temperature of the load412to be sensed during the heating operation. When provided to the processing unit480, the temperature information enables the processing unit480to select a combination of excitation signal parameters, to alter the power of the RF signal supplied by the RF signal generator440(e.g., by controlling the bias and/or supply voltages provided by the power supply and bias circuitry486), and/or to determine when a heating operation should be terminated. The weight sensor(s) are positioned under the load412, and are configured to provide an estimate of the weight of the load412to the processing unit480. The processing unit480may use this information, for example, to select a combination of excitation signal parameters, to determine a desired power level for the RF signal supplied by the RF signal generator440, and/or to determine an approximate duration of a heating operation.

Other combinations of the various features and aspects of the embodiments described above may also be provided. For example, one or more features or aspects of one embodiment may be combined with one or more features or aspects of another embodiment, even though the resulting combination is not expressly described or identically shown in the figures.

Described above are power amplifier and other devices having a bidirectional coupler for monitoring forward and reflected power, with high directivity. The power measurement is realized by additional bond wires that are inductively coupled to bond wires used to couple a power transistor device to an output port in connection with signal output, impedance matching or other adjustment. The power monitoring may be achieved without imposing any phasing adjustments or other phase differences on output impedance matching circuitry or the circuitry used to provide the bidirectional coupler.

Although described as useful in connection with RF power devices, the disclosed devices may be useful in a variety of other applications. The devices are not limited to any particular application or type of load.

In a first aspect, a device includes an output circuit that includes an input port at which a signal is received, an output port at which an impedance-adjusted representation of the signal is provided, and a set of bond wires connecting the input and output ports. The device further includes first and second couplers, each including a respective coupling bond wire along the set of bond wires for inductive coupling with the set of bond wires. The first coupler is oriented relative to the output circuit to measure forward power provided by the impedance-adjusted representation of the signal via the output port. The second coupler is oriented relative to the output circuit to measure reflected power received via the output port.

In a second aspect, a power amplifier includes a transistor device configured to generate a signal, and an output circuit that establishes an impedance of the power amplifier without a lumped element-based phase shift in the generated signal. The output circuit includes an input port at which the generated signal is received, an output port at which an impedance-adjusted representation of the generated signal is provided, and a set of bond wires connecting the input and output ports. The power amplifier further includes first and second couplers, each including a respective coupling bond wire along the set of bond wires for inductive coupling with the set of bond wires, a respective measurement port connected to a first end of the respective coupling bond wire, and a respective termination connected at a second end of the respective coupling bond wire. The first coupler is oriented relative to the output circuit to provide a first output on the respective measurement port indicative of forward power provided by the impedance-adjusted representation of the generated signal via the output port. The second coupler is oriented relative to the output circuit to provide a second output on the respective measurement port indicative of reflected power received via the output port.

In a third aspect, a method of measuring forward power and reflected power for a power amplifier includes generating a signal with a transistor device of the power amplifier, and adjusting an output impedance of the power amplifier for the generated signal via an output circuit, the output circuit including an input port at which the generated signal is received, an output port at which an impedance-adjusted representation of the generated signal is provided, and a set of bond wires connecting the input and output ports. The method further includes developing a forward power measurement at a first measurement port via inductive coupling between a first coupling bond wire inductively coupled with the set of bond wires, and developing a reflected power measurement at a second measurement port via inductive coupling between a second coupling bond wire inductively coupled with the set of bond wires.

In a fourth aspect, a solid-state system includes a heating cavity configured to contain a load to be heated, a transistor device configured to generate a signal to support introduction of energy into the heating cavity, an output circuit comprising an input port at which the generated signal is received, an output port at which a representation of the generated signal is provided, and a set of bond wires connecting the input and output ports, a power detection circuit including first and second couplers, each including a respective coupling bond wire along the set of bond wires for inductive coupling with the set of bond wires, the first coupler being oriented relative to the output circuit to measure forward power provided by the representation of the signal via the output port, and the second coupler being oriented relative to the output circuit to measure reflected power received via the output port, and a processing unit coupled to the power detection circuit to receive signals indicative of the measured forward power and the measured reflected power.

The present invention is defined by the following claims and their equivalents, and nothing in this section should be taken as a limitation on those claims. Further aspects and advantages of the invention are discussed above in conjunction with the preferred embodiments and may be later claimed independently or in combination.