RF power amplifier with combined baseband, fundamental and harmonic tuning network
阅读说明：本技术 具有组合的基带、基波和谐波调谐网络的rf功率放大器 (RF power amplifier with combined baseband, fundamental and harmonic tuning network ) 是由 阿日贡巴彦尔 张海东 R.威尔逊 F.莊 母千里 E.哈希莫托 于 2018-11-27 设计创作，主要内容包括：一种用于射频(RF)放大器设备(108)的阻抗匹配网络(116)包括基带终止电路(122),其具有电抗部件,所述电抗部件被配置成对在低于与RF放大器设备(108)相关联的基波频率范围的基带频率范围中的信号呈现低阻抗。网络(116)还包括基波频率匹配电路(124),其具有电抗部件,所述电抗部件被配置成将基波频率范围中的RF放大器设备(108)的输出阻抗基本上匹配到预定值。网络(116)还包括二阶谐波终止电路(126),其具有电抗部件,所述电抗部件被配置成在具有基波频率范围中的基波频率的RF信号的二阶谐波处呈现低阻抗。其它实施例包括放大器电路,其包括网络(116)和RF放大器设备(108),以及封装的RF放大器,其包括金属凸缘(202)、RF晶体管(214)、以及包括网络(116)的集成无源设备(216)。(An impedance matching network (116) for a Radio Frequency (RF) amplifier device (108) includes a baseband termination circuit (122) having reactive components configured to present a low impedance to signals in a baseband frequency range below a fundamental frequency range associated with the RF amplifier device (108). The network (116) further includes a fundamental frequency matching circuit (124) having reactive components configured to substantially match an output impedance of the RF amplifier device (108) in the fundamental frequency range to a predetermined value. The network (116) also includes a second harmonic termination circuit (126) having reactive components configured to present a low impedance at a second harmonic of the RF signal having a fundamental frequency in the fundamental frequency range. Other embodiments include an amplifier circuit comprising a network (116) and an RF amplifier device (108), and a packaged RF amplifier comprising a metal flange (202), an RF transistor (214), and an integrated passive device (216) comprising the network (116).)
1. An impedance matching network (116) for a Radio Frequency (RF) amplifier device (108), the impedance matching network (116) comprising:
a baseband termination circuit (122) having reactive components configured to present a low impedance to signals in a baseband frequency range below a fundamental frequency range associated with the RF amplifier device (108);
a fundamental frequency matching circuit (124) having reactive components configured to substantially match an output impedance of the RF amplifier device (108) in the fundamental frequency range to a predetermined value; and
a second harmonic termination circuit (126) having reactive components configured to present a low impedance at a second harmonic of an RF signal having a fundamental frequency in the fundamental frequency range.
2. The impedance matching network (116) of claim 1, wherein the fundamental frequency matching circuit (124) is configured to transfer output power from the RF amplifier device (108) across the fundamental frequency range with a variation of no more than 2 dB.
3. The impedance matching network (116) of claim 1, wherein:
the fundamental frequency matching circuit (124) includes a first capacitor (128) and a first inductor (130) electrically coupled in series;
the capacitance of the first capacitor (128) is such that the first capacitor (128) appears as a short circuit at frequencies in the fundamental frequency range; and
the inductance of the first inductor (130) is such that the first inductor (130) and the inherent capacitance of the RF amplifier device (108) form a parallel L C resonator at frequencies in the fundamental frequency range.
4. The impedance matching network (116) of claim 3, wherein:
the second harmonic termination circuit (126) includes a parallel L C resonator connected in series between the first inductor (130) and the first capacitor (128) of the fundamental frequency matching circuit (124);
the parallel L C resonator includes a second capacitor (134) in parallel with a second inductor (132), and
an inductance of the second inductor (132) and a capacitance of the second capacitor (134) are such that the parallel L C resonator resonates with the first inductor (130) and the natural capacitance of the RF amplifier device (108) at a second order harmonic of a fundamental frequency in the fundamental frequency range.
5. The impedance matching network (116) of claim 3, wherein:
the baseband termination circuit (122) includes a third capacitor (140) and a third inductor (138) electrically coupled to the first capacitor (128) and the second harmonic termination circuit (126); and
the inductance of the third inductor (138) and the capacitance of the third capacitor (140) are such that the third inductor (138) and the third capacitor (140) provide a low impedance to signals in the baseband frequency range.
6. The impedance matching network (116) of claim 5, wherein the parallel L C resonator, the first capacitor (128), the third inductor (138), and the third capacitor (140) are provided in an integrated passive device (216).
7. The impedance matching network (116) of claim 5, wherein:
the baseband termination circuit (122) further includes a first resistor (136) electrically coupling the third capacitor (140) and the third inductor (138) to the first capacitor (128) and the second harmonic termination circuit (126);
the resistance of the first resistor (136) is such that an impedance response of the baseband termination circuit (122) is flatter across the baseband frequency range than a corresponding impedance response of the baseband termination circuit (122) without the first resistor (136).
8. An amplifier circuit (100), comprising:
a first port, a second port and a reference potential port (106);
an RF amplifier device (108) comprising a first terminal electrically coupled to the first port, a second terminal electrically coupled to the second port, and a reference potential terminal (114) electrically coupled to the reference potential port (106), the RF amplifier device (108) having a natural capacitance and being configured to amplify RF signals having a fundamental frequency within the fundamental frequency range as between the first and second terminals; and
the impedance matching network (116) of any of claims 1-7, wherein the impedance matching network is electrically coupled to the second terminal of the RF amplifier (108) and to the first port.
9. The amplifier circuit (100) of claim 8, wherein:
the amplifier circuit (100) comprises a series branch (118), the series branch (118) being connected between the first port of the amplifier circuit (100) and the first terminal of the RF amplifier device (108); and
the impedance matching network (116) is electrically coupled to the first port via the series branch (118).
10. The amplifier circuit (100) of claim 8, further comprising a DC terminal (145), wherein the baseband termination circuit (122) of the impedance matching network (116) further comprises a fourth inductor (144) connected between the DC terminal (145) and the second port (104).
11. The amplifier circuit (100) of claim 8, wherein:
the first terminal of the RF amplifier device (108) is an output terminal (112) and the first port of the RF amplifier device (108) is an output port (104);
the second terminal of the RF amplifier device (108) is an input terminal (110) and the second port of the RF amplifier device (108) is an input port (102); and
the intrinsic capacitance of the RF amplifier device (108) is an output capacitance of the RF amplifier device (108).
12. The amplifier circuit (100) of claim 8, wherein:
the first terminal of the RF amplifier device (108) is an input terminal (110) and the first port of the RF amplifier device (108) is an input port (102);
the second terminal of the RF amplifier device (108) is an output terminal (112) and the second port of the RF amplifier device (108) is an output port (104); and
the intrinsic capacitance of the RF amplifier device (108) is an input capacitance of the RF amplifier device (108).
13. A packaged RF amplifier (200) comprising:
a metal flange (202) comprising a first conductive lead, a second conductive lead, and a conductive die pad (212);
an RF transistor (214) mounted on the metal flange (202) and including a first terminal electrically coupled to the first lead, a second terminal electrically coupled to the second lead, and a reference potential terminal (114) electrically coupled to the die pad (212), the RF transistor (214) configured to amplify an RF signal as between the first terminal and the second terminal across an RF frequency range including fundamental RF frequencies; and
an integrated passive device (216) mounted on the metal flange (202) adjacent to the RF transistor (214) and electrically coupled to the first terminal and the first lead, wherein the integrated passive device (216) comprises the impedance matching circuit (116) of any of claims 1-7.
14. The packaged RF amplifier (200) of claim 13, further comprising:
a first set (218) of electrically conductive bond wires directly connected between the first terminal and the first lead (206); and
a second set of electrically conductive bond wires (220) directly connected between the first terminal and the integrated passive device (216), wherein:
the second set of electrically conductive bond wires (220) provides a first inductor (130) of the impedance matching network (116), and
the first inductor (130) and the inherent capacitance of the RF transistor 214 form a parallel L C resonator of the impedance matching network (116) at frequencies in the fundamental frequency range.
15. The packaged RF amplifier (200) of claim 13, wherein:
the integrated passive device (216) comprises the impedance matching network (116) of claim 3; and
the first capacitor (128) is connected in series between the first inductor (130) and the conductive die pad (212).
16. The packaged RF amplifier (200) of claim 13, wherein:
the integrated passive device (216) comprises the impedance matching network (116) of claim 5; and
the third inductor (138) and the third capacitor (140) are also connected to the conductive die pad (212).
17. The packaged RF amplifier (200) of claim 13, wherein:
the first terminal of the RF transistor (214) is an output terminal and the first lead of the metal flange (202) is an output lead (206);
the second terminal of the RF transistor (214) is an input terminal and the second lead of the metal flange (202) is an input lead (204); and
the intrinsic capacitance of the RF transistor (214) is an output capacitance.
18. The packaged RF amplifier of claim 13, wherein:
the first terminal of the RF transistor is an input terminal and the first lead of the metal flange (202) is an input lead (204);
the second terminal of the RF transistor is an output terminal and the second lead of the metal flange (202) is an output lead (206); and
the inherent capacitance of the RF transistor (214) is an input capacitance.
Technical Field
The present application relates to RF (radio frequency) amplifiers, and in particular to impedance matching networks for RF amplifiers.
Background
RF power amplifiers are used in a variety of applications, such as base stations for wireless communication systems and the like. The RF power amplifier is designed to provide linear operation without distortion. Signals amplified by RF power amplifiers often include signals having a high frequency modulated carrier with a frequency in the range of 400 megahertz (MHz) to 4 gigahertz (GHz). The baseband signal that modulates the carrier is typically at a relatively low frequency and may be up to 300MHz or higher depending on the application.
Examples of transistor dies used in RF applications include MOSFET (metal oxide semiconductor field effect transistor), L DMOS (laterally diffused metal oxide semiconductor) devices, and HEMT (high electron mobility transistor) devices.
The input and output impedance matching networks are used to match the relatively low characteristic impedance of the RF transistors for high power devices to a fixed impedance value (e.g., 50 ohms). In this way, greater efficiency is obtained through load matching. However, the input and output impedance matching networks are frequency selective and introduce impedance dispersion versus frequency, which results in band-limited power amplifier operation. Therefore, an important goal of RF amplifier design is highly efficient operation over a wide bandwidth.
Efficient amplifier operation can be achieved by appropriately terminating (terminate) RF signals in the baseband frequency below the fundamental frequency and by appropriately terminating higher order harmonics of the fundamental signal above the fundamental frequency range. One way to filter out these signals is to provide a tuning circuit at the circuit board level (i.e., outside the package including the RF transistor die). However, board level termination (termination) techniques are complex and require the use of valuable space. Furthermore, these techniques have limited effectiveness due to parasitic effects that affect the propagation of signals between the transistor die and the circuit board. Another way to filter out these signals is at the package level (i.e., within the same package that includes the RF transistor die). While this solution advantageously places the tuning circuit close to the transistor die, it adds complexity to the design. Furthermore, perfect tuning is difficult to achieve due to mutual coupling effects between bond wires connected to various components of the tuning network. This problem becomes particularly problematic as the complexity of the tuning network and the component count increase.
Disclosure of Invention
An amplifier circuit is disclosed. The amplifier circuit includes a first port, a second port, and a reference potential port. The amplifier circuit additionally includes an RF amplifier device having a first terminal electrically coupled to the first port, a second terminal electrically coupled to the second port, and a reference potential terminal electrically coupled to the reference potential port. The RF amplifier device is configured to amplify an RF signal, e.g., between the first and second terminals, across an RF frequency range including a fundamental RF frequency. The amplifier circuit additionally includes an impedance matching network electrically coupled to the first terminal and the first port of the RF amplifier. The impedance matching network includes a baseband termination circuit having reactive components with electrical parameters that are adjusted such that the baseband termination circuit presents a low impedance in a baseband frequency region below the RF frequency range. The impedance matching network additionally comprises a fundamental frequency matching circuit having reactive components with electrical parameters which are adjusted such that the fundamental frequency matching circuit presents a complex conjugate of the intrinsic impedance of the RF amplifier device in the RF frequency range. The amplifier circuit additionally includes a second harmonic termination circuit having a reactive component with an electrical parameter adjusted such that the second harmonic termination circuit presents a low impedance at a second harmonic of frequencies in the fundamental RF frequency range.
A packaged RF amplifier is disclosed. The packaged RF amplifier includes a metal flange including a first conductive lead, a second conductive lead, and a conductive die pad. The packaged RF amplifier additionally includes an RF transistor mounted on the metal flange and having a first terminal electrically coupled to the first lead, a second terminal electrically coupled to the second lead, and a reference potential terminal electrically coupled to the die pad, the RF amplifier device configured to amplify an RF signal, such as between the first terminal and the second terminal, across an RF frequency range including a fundamental RF frequency. The packaged RF amplifier additionally includes an integrated passive device mounted on the metal flange adjacent the RF transistor and electrically coupled to the first terminal and the first lead. The integrated passive device includes a plurality of reactive components. The parameters of the reactive component are adjusted such that the integrated passive device presents a low impedance in the baseband frequency region below the RF frequency range, a complex conjugate of the intrinsic impedance of the RF amplifier device in the RF frequency range, and a low impedance at the second harmonic of the frequency in the fundamental RF frequency range.
Those skilled in the art will recognize additional features and advantages upon reading the following detailed description, and upon viewing the accompanying drawings.
Drawings
The elements of the drawings are not necessarily to scale relative to each other. Like reference numerals designate corresponding similar parts. Features of the various illustrated embodiments may be combined unless they are mutually exclusive. Embodiments are depicted in the drawings and are detailed in the following description.
Fig. 1 depicts an electrical schematic of an amplifier circuit according to an embodiment.
Fig. 2 (which includes fig. 2A and 2B) depicts a packaged amplifier circuit according to an embodiment. Fig. 2A depicts the amplifier from a plan view perspective and fig. 2B depicts the amplifier from a side view perspective.
Fig. 3 (which includes fig. 3A, 3B, and 3C) depicts a modeled impedance matching network according to an embodiment. Fig. 3A depicts a circuit schematic of a modeled impedance matching network. Fig. 3B depicts a comparison of transmission characteristics for modeled impedance matching networks with and without second order harmonic tuning in accordance with an embodiment. Fig. 3C depicts a comparison of transmission characteristics for a modeled impedance matching network across a range of frequencies with and without baseband termination according to an embodiment.
Detailed Description
According to embodiments disclosed herein, an amplifier circuit is disclosed. The amplifier circuit includes an RF amplifier device and an impedance matching network electrically coupled to an output terminal of the RF amplifier device. The impedance matching network is configured to simultaneously perform fundamental frequency matching, baseband termination, and second order harmonic termination. To this end, the impedance matching network comprises a first reactance network presenting a complex conjugate of the inherent impedance of the RF amplifier device in the fundamental frequency range, a second reactance network presenting a low impedance in the baseband frequency range, and a third reactance network presenting a low impedance at higher order harmonics of the fundamental RF frequency.
According to embodiments disclosed herein, an amplifier circuit comprising an RF amplifier device and an impedance matching network is integrated within a single device package. The RF amplifier device is provided by a transistor die mounted on a conductive die pad of the package between package leads. The impedance matching network is provided by a network of passive components (e.g., capacitors and inductors) mounted on die pads connected between the transistor die and the package leads.
According to an advantageous embodiment of the packaged amplifier device, IPDs (integrated passive devices) are used to provide some or all of the passive components for the fundamental frequency matching circuit, the baseband termination circuit and the second order harmonic termination circuit. This design avoids the disadvantages of board level techniques for selective filtering, such as increased area and reduced effectiveness due to distance from the transistor die. Furthermore, the design avoids the disadvantages of package-level selective filtering techniques that rely on complex networks of bond wires and discrete passive components (e.g., chip capacitors), such as cross-coupling. By using the IPD, many bond wires that are prone to cross-coupling are eliminated from the device.
Referring to fig. 1, an amplifier circuit 100 is depicted, the amplifier circuit 100 including an input port 102, an output port 104, and a reference potential port 106, the amplifier circuit 100 additionally including an RF amplifier device 108, the RF amplifier device 108 having an input terminal 110 electrically coupled to the input port 102, an output terminal 112 electrically coupled to the output port 104, and a reference potential terminal 114 electrically coupled to the reference potential port 106 in various embodiments, the RF amplifier device 108 and the complete amplifier circuit 100 may be a multi-carrier amplifier, a multi-band amplifier, an L TE (long term evolution) compatible amplifier, a WCDMA (wideband code division multiple access) compatible amplifier, an 802.11 (X) compatible amplifier, and the like.
In general, the RF amplifier device 108 may be any device that may perform amplification for an RF signal. In the depicted embodiment, the RF amplifier device 108 is a transistor device, with the input terminal 110 corresponding to a control terminal or gate terminal of the transistor device, the output terminal 112 corresponding to a first load terminal (e.g., drain terminal) of the transistor device, and the reference potential terminal 114 corresponding to a second load terminal (e.g., source terminal) of the transistor device.
The RF amplifier device 108 is configured to amplify an RF signal across a range of RF frequencies, such as between the input terminal 110 and the output terminal 112, across a range of RF frequencies including a fundamental RF frequency. According to an embodiment, the frequency range is a so-called "wideband" frequency range. A "wideband" frequency range refers to the fact that the range of frequency values for an RF signal exceeds the coherence bandwidth of a single channel.
In the following discussion, an RF frequency range between 1.8 GHz (gigahertz) and 2.2 GHz with a fundamental (center) frequency of 2.0 GHz is used for exemplary purposes to describe parameters of the amplifier circuit 100. In this example, the second order harmonic of the fundamental RF frequency lies in the range of 3.6 GHz to 5.4 GHz, with the second order harmonic of the fundamental frequency at 4.0 GHz. Furthermore, in this example, the baseband signal modulating the RF signal in the RF frequency range is located in a baseband frequency range significantly lower than the RF frequency range, for example in the 400MHz (megahertz) range in the case of the fundamental frequency range of 1.8 GHz-2.2 GHz. More generally, the principles described herein may be applied to a wide variety of different frequency ranges, including fundamental frequencies in the range of 100MHz to 10GHz and baseband frequencies in the range of several MHz to 500 MHz.
Amplifier circuit 100 also includes an output impedance matching network 116 electrically coupled between output terminal 112 and output port 104. The output impedance matching network 116 comprises a series branch 118 connected in series between the output terminal 112 of the RF amplifier and the output port 104 of the RF amplifier and a parallel branch 120 connected in parallel with the output port 104 of the RF amplifier and the reference potential terminal 114. The output impedance matching network 116 includes a baseband termination circuit 122, a fundamental frequency matching circuit 124, and a second harmonic termination circuit 126. The baseband termination circuit 122, fundamental frequency matching circuit 124, and second order harmonic termination circuit 126 are each provided by a network of reactive components. In the depicted embodiment, these reactive components include inductors and capacitors. As will be discussed in further detail below, the parameters (i.e., inductance and capacitance) of these inductors and capacitors are specifically adjusted to provide a desired frequency response within a given frequency range. More generally, the reactive components of the output impedance matching network 116 may be provided by any of a variety of components (e.g., radial stubs, transmission lines, etc.), with the parameters (e.g., radii, lengths, etc.) of these components adjusted to provide a desired frequency response.
The components of the fundamental frequency matching circuit 124 are adjusted such that the output impedance matching network 116 presents at the output terminal 112 of the RF amplifier device 108 a complex conjugate of the natural impedance of the RF amplifier device 108 in the RF frequency range. As is generally known in the art, optimal power transfer occurs when the input and output impedances are matched to the complex conjugate of each other. Typically, transistor devices such as GaN-based HEMTs have relatively low characteristic input and output impedances (e.g., 2 ohms or less). The fundamental frequency matching circuit 124 matches the output impedance of the RF amplifier device 108 to a fixed value (e.g., 50 ohms) corresponding to a normalized value at the system level. In this way, optimal power transfer between the amplifier circuit 100 and other components at the system level may be achieved. Using the exemplary fundamental frequency ranges of 1.8 GHz (gigahertz) and 2.2 GHz, the parameters (i.e., capacitance and inductance) of the reactive components in the fundamental frequency matching circuit 124 are adjusted so that high power transfer occurs across the entire fundamental frequency range of 1.8 GHz (gigahertz) to 2.2 GHz (e.g., no more than-2 dB). According to an embodiment, an optimal power transfer of 0dB or substantially close to 0dB occurs at a center frequency of 2.0 GHz.
According to an embodiment, the fundamental frequency matching circuit 124 includes a first capacitor 128 and a first inductor 130. the first capacitor 128 and the first inductor 130 are connected in series with each other along the parallel leg 120. the inductance of the first inductor 130 is adjusted to provide impedance matching with respect to the characteristic impedance of the RF amplifier device 108. in the depicted circuit, the first inductor 130 is in parallel with the output of the RF amplifier device 108. thus, the output capacitance of the RF amplifier device 108 and the first inductor 130 form a first parallel L C resonator as is generally known in the art, the parallel L C circuit provides the maximum impedance (from the RF perspective) at the resonant frequency (i.e., the point at which the reactive leg currents are equal and opposite). according to an embodiment, the inductance of the first inductor 130 is adjusted such that the first parallel L C resonator resonates at a center frequency of 2.0 GHz. the first capacitor 128 is configured to block DC blocking very low frequencies (e.g., frequencies less than 10 MHz) and DC blocking capacitors of the DC signals.the DC blocking capacitors have very large value, thus, the first parallel inductor 128C capacitor may exhibit a much more negligible effect on the fundamental frequency of the first parallel resonator at this way as RF frequency parameter of the first parallel L.
The components of the second harmonic termination circuit 126 are adjusted such that the second harmonic termination circuit 126 presents a low impedance at the output terminal 112 of the RF amplifier device 108 in the second harmonic frequency range. Filtering out higher order harmonic components of the RF signal can significantly improve the efficiency of the device. By mitigating harmonic oscillations at the output of the device, the shape of the voltage and current waveforms during the transition states is advantageously controlled for minimal overlap and therefore greater efficiency. This is achieved by including a fundamental frequency F for the amplified RF signal0Of even higher order harmonics (e.g., 2F)0，4F0，6F0Etc.) is completed. To this end, the second harmonic termination circuit 126 is tuned to provide a short circuit path (from an RF perspective) at the second harmonic of the fundamental frequency (e.g., 4.0GHz in the exemplary fundamental frequency range). That is, second order harmonic termination is designed to terminate RF signals in this frequency range so that they do not appear at the RF output port 104.
According to an embodiment, the second order harmonic termination circuit 126 includes a second inductor 132 and a second capacitor 134, the second inductor 132 and the second capacitor 134 are connected in parallel with each other along the parallel leg 120 of the impedance matching circuit, thus, the second inductor 132 and the second capacitor 134 form a second parallel L C resonator, the parameters of the second L C resonator (i.e., the capacitance of the second capacitor 134 and the inductance of the second inductor 132) are adjusted to provide a low impedance path for the second order harmonic between the output terminal 112 of the RF amplifier device 108 and the reference potential terminal 114. this adjustment of the parameters of the second L C resonator accounts for the collective effect of other reactance values in the output impedance matching network 116, including the first parallel L C resonator, which includes the first inductor 130 and the inherent capacitance of the RF amplifier device 108. as is generally known, the parallel resonant circuit becomes more capacitive as the frequency value increases above the resonant frequency and becomes more inductive as the frequency value decreases below the resonant frequency. applying this principle, the resonant frequency of the second L C resonator can be adjusted so that the second harmonic termination circuit is connected in parallel with the resonant frequency of the second resonator 112 so that the output impedance matching network 112, i.e.g., the impedance matching impedance of the second parallel amplifier device 112, the resonant circuit, the resonant impedance matching network 114, the resonant frequency of the resonant circuit, thus, the resonant impedance matching circuit can be short-parallel impedance matching circuit, or the inductive impedance matching the resonant circuit, the resonant frequency of the resonant circuit, thereby, for example.
The baseband termination circuit 122 is tuned to present a low impedance in the baseband frequency region below the RF frequency range. By suppressing these lower frequency values, the effects of intermodulation distortion (IMD) across the baseband frequency range may be mitigated, thereby improving the linear efficiency of the amplifier circuit 100. The parameters (e.g., capacitance and inductance) of the baseband termination circuit 122 are selected such that the impedance matching circuit suppresses these lower frequency values. That is, the baseband termination circuit 122 provides a low impedance path (from an RF perspective) from the output terminal 112 of the RF amplifier device 108 to the reference potential terminal 114 for frequencies lying within this range.
According to an embodiment, baseband termination circuit 122 includes a first resistor 136, a third inductor 138, and a third capacitor 140, each of these components is connected on a second branch 142 of output impedance matching network 116. the second branch 142 of output impedance matching network 116 is connected between a first node 143 that directly connects first capacitor 128 to a second parallel L C resonator and a reference potential port. the parameter values (i.e., resistance, inductance, and capacitance) of the components in baseband termination circuit 122 are selected to exhibit a low impedance response across a wideband baseband frequency region. using the baseband frequency range of 400MHz as an example, the parameters of third inductor 138 and third capacitor 140 may be selected such that these components, in conjunction with other components of the impedance matching circuit, form a low impedance path from output terminal 112 of RF amplifier device 108 to reference potential terminal 114. by adjusting the resistance of first resistor 136, the impedance response of baseband termination circuit 122 is flattened for better performance across the wideband frequency range.
Optionally, the output impedance matching network 116 may include a fourth inductor 144 connected between the series branch 118 and the DC terminal 145 of the amplifier circuit 100. The fourth inductor 144 is configured as an RF choke, i.e. a device that blocks higher frequency values while transmitting lower frequency values. The RF choke may be used in conjunction with the first resistor 136, the third inductor 138, and the third capacitor 140 to present a low impedance in the baseband frequency region.
The amplifier circuit 100 additionally comprises an input impedance matching network 146 connected between the input port 102 of the amplifier circuit 100 and the input terminal 110 of the RF amplifier device 108. In the depicted embodiment, the input impedance matching network 146 includes a fifth inductor 148 and a sixth inductor 150 connected in series between the input port 102 and the input terminal 110 of the RF amplifier device 108, and a fourth capacitor 152 connected in parallel with the input terminal 110 of the RF amplifier device 108 and the reference potential terminal 114. According to one embodiment, the parameters of the sixth inductor 150 and the fourth capacitor 152 are adjusted in a similar manner as previously discussed for impedance matching between the input capacitance of the RF amplifier device 108 and a fixed impedance value at a board level (e.g., 50 ohms) in the fundamental frequency range.
Instead of the circuit topology depicted in fig. 1, the input impedance matching network 146 may be configured in a substantially similar manner as the output impedance matching network 116 as previously described. In this case, a series branch 118 of the output impedance matching network 116 connects the input port 102 to the input terminal 110 of the RF amplifier device 108, and a parallel branch 120 is connected in parallel with the input terminal 110 of the RF amplifier and the reference potential terminal 114. While using the input impedance of the amplifier device (e.g., the gate-source capacitance in the case of a MOSFET device) as the characteristic impedance to which the network is matched, the parameter values of the components in the impedance matching network may be adjusted in the same manner as described above. In different embodiments of the amplifier circuit 100, the impedance matching network topology may be provided at the input side only, the output side only, or both the input side and the output side.
Referring to fig. 2, a packaged RF amplifier 200 is depicted, in accordance with an embodiment. The packaged RF amplifier 200 comprises two amplifier circuits 100 as described with reference to fig. 1, the two amplifier circuits 100 being arranged adjacent to each other. Packaged RF amplifier 200 includes a metal flange 202 configured to interface with another device, such as a printed circuit board. A pair of conductive input leads 204 extend away from a first side of the metal flange 202, and a pair of conductive output leads 206 extend away from a second side of the metal flange 202 in a direction opposite the input leads 204. These conductive input leads 204 and conductive output leads 206 provide the input port 102 and the output port 104, respectively, of the amplifier circuit 100 described with reference to fig. 1. Optionally, packaged RF amplifier 200 includes a separate DC bias lead 208 extending away from the side of the package adjacent output lead 206.
An electrically insulating window frame 210 is formed around the perimeter of the metal flange 202. The window frame 210 insulates the input lead 204 and the output lead 206 from the metal flange 202. A central portion of the metal flange 202 is exposed from the window frame 210. This exposed portion of metal flange 202 provides a conductive die pad 212 for mounting an integrated circuit device thereon. Since the metal flange 202 may include a thermally and electrically conductive material (e.g., copper, aluminum, etc.), the electrically conductive die pad 212 may provide both a reference potential connection (e.g., GND terminal) and a heat sink configured to carry heat away from the integrated circuit device mounted thereon.
RF transistors 214 are mounted on metal flange 202 these RF transistors 214 provide RF amplifier device 108 as previously described in amplifier circuit 100 of fig. 1 RF transistors 214 may be configured as power transistors such as MOSFETs (metal oxide semiconductor field effect transistors), DMOS (double diffused metal oxide semiconductor) transistors, GaN HEMTs (gallium nitride high electron mobility transistors), GaN MESFETs (gallium nitride metal semiconductor field effect transistors), L DMOS transistors, etc., and more generally as any type of RF transistor device.
The RF transistor 214 includes conductive input, output, and reference potential terminals. In the depicted embodiment, the reference potential terminal is disposed on the bottom side of the RF transistor 214. The reference potential terminal directly faces the die pad 212 and is electrically connected to the die pad 212, for example, by a conductive paste. The input and output terminals of the RF transistor 214 are disposed on the top side of the RF transistor 214 opposite to the reference potential terminal.
The packaged RF amplifier 200 includes an output impedance matching network 116 as previously described with reference to fig. 1 connected between the output terminal of the RF transistor and the output lead 206. Most of the passive components of the output impedance matching network 116 are provided by the IPD (integrated passive device) 216. The lower side of IPD216 includes reference potential terminal 114, reference potential terminal 114 being mounted on die pad 212 in a manner similar to that previously described with reference to the RF transistor.
In general, the term IPD refers to an integrated circuit, which may be semiconductor-based, and includes a plurality of passive devices integrally formed within and connected to terminals of the IC. The customized circuit topology may be provided by the IPD. A variety of different structures are fabricated within the device to provide the necessary frequency response of a given passive component (e.g., capacitor, inductor, etc.). Examples of such structures include parallel plate capacitors, radial stubs, transmission lines, and the like.
In the depicted embodiment, the first set of conductive bond wires 218 is electrically connected directly between the output terminal of the RF transistor 214 and the output lead 206. The second set 220 of electrically conductive bond wires is directly electrically connected between the output terminal of the RF transistor 214 and the integrated passive device 216. The third set of electrically conductive bond wires 222 is directly connected between the output lead 206 and the DC bias lead 208.
The second set of conductive bond wires 220 provides the first inductor 130 of the output impedance matching network 116, as previously discussed with reference to fig. 1. Additionally, the third set of conductive bond wires 222 provides the fourth inductor 144 of the output impedance matching network 116, as previously discussed. As one of ordinary skill in the art will appreciate, there is some inductance associated with any wire connection. Thus, each span of bond wires extending between two conductive terminals of the packaged RF amplifier 200 provides a defined inductance. The inductance value can be adjusted by adjusting the physical parameters of the span of the bond wire. Exemplary physical parameters that may be adjusted to achieve a desired inductance include the height of the bond wires, the separation distance between the bond wires, the length of the span of the bond wires, and the like.
In the depicted embodiment, the remaining components of the output impedance matching network 116, except for the first inductor 130, are provided by the IPD 216. In particular, the first, second and third capacitors 128, 134, 140, the second and third inductors 132, 138, and the resistor 136 are incorporated into the integrated passive device 216. An outline 154 of the circuit covered by IPD216 is provided in fig. 1 to illustrate the internal circuit topology of IPD 216. This embodiment represents just one example of many potential configurations of IPD 216. More generally, the IPD may be used to provide any one or more passive components in the output impedance matching network 116. Multiple separate IPDs may be provided along with other devices (e.g., chip capacitors, etc.) in a single device package.
Referring again to fig. 2, on the input side of the device, an input impedance matching network 146 is provided as previously described with reference to fig. 1. The fourth capacitor 152 is provided by a chip capacitor 224, which chip capacitor 224 is mounted on the die pad 212 and electrically connected to the die pad 212 in a similar manner as previously described. A fourth set 226 of bond wires is electrically connected between the input lead 204 and the chip capacitor 224. A fifth set 228 of bond wires is electrically connected between the chip capacitor 224 and the input terminal of the RF transistor 214. The fourth set of bond wires 226 provides the fifth inductor 148 and the fifth set of bond wires 218 provides the sixth inductor 150 in the input impedance matching network 146, as previously described. As previously mentioned, the input impedance matching network 146 may have a similar topology and function as the first output impedance matching network 116. In this case, instead of the chip capacitors 224, integrated passive devices may be mounted at the input side of the device and configured according to the techniques described herein.
Referring to fig. 3, a graphical representation of the impedance response of the output impedance matching network 116 across a wide frequency range including a baseband region, a fundamental region, and a second order harmonic region is depicted in accordance with an embodiment provided.
Referring to fig. 3A, a circuit schematic of a modeled passive network 300 is depicted, in accordance with an embodiment. The modeled passive network 300 includes the output impedance matching network 116 as previously described with reference to fig. 1. In addition, the output capacitance of the RF amplifier device 108 is modeled as a fifth capacitor 302 in the network. The modeled passive network 300 includes an input port 304 corresponding to the output terminal 112 of the RF amplifier device 108 as previously described, and an output port 306 corresponding to the output port 104 of the amplifier circuit 100 as previously described. Further, in this model, the DC terminal 145 is connected to the reference potential terminal 145.
Referring to fig. 3B, the transmission characteristics of the modeled passive network 300 is shown, a first curve 318 plots the transmission characteristics of the modeled passive network 300 of fig. 3A as between the input port 304 and the output port 306, a second curve 320 plots the corresponding transmission characteristics as between the input port 304 and the output port 306 of the passive network, which is the same as the passive network of fig. 3A but does not include a second L C resonator, i.e., a second inductor 306 and a second capacitor 308 as illustrated in fig. 3A, rather, the first inductor 310 is directly connected to the first capacitor 312, in fig. 3B, the X-axis corresponds to a frequency sweep of 10MHz-6GHz, which encompasses the baseband, fundamental, and second harmonic operating regions, the Y-axis plots the power transfer between the first inductor 130 and the second port in decibels (dB), thus, a perfectly transmitted signal corresponds to 0dB, while a signal as well terminated between the first port 304 and the second port 306 has a lower transmission value, e.g., a power ratio of less than about 5% at 31 dB.
As can be seen, the second harmonic termination circuit 126 advantageously suppresses second harmonics of frequencies in the fundamental frequency range (i.e., frequencies at or near 4.3 GHz). At the same time, the fundamental frequency (i.e., a frequency at or near 2.15 GHz) is well transmitted because the change in power is 0 dB. In addition, the inclusion of the second order harmonic termination circuit 126 does not meaningfully degrade the transmission of signals outside the second order harmonic frequency range.
Referring to fig. 3C, a transmission characteristic of a modeled passive network 300 is shown, according to another embodiment. A third curve 322 plots the transmission characteristics of the modeled passive network 300 of fig. 3A as between the input port 304 and the output port 306. A fourth curve 314 depicts a corresponding transmission characteristic as between the input port 304 and the output port 306 of a passive network that is the same as the passive network of fig. 3A but does not include the baseband termination circuit 122. Thus, the second branch 142 and the fourth inductor 144 are removed from the circuit. In the figure, the X-axis corresponds to a frequency sweep of 10MHz-6GHz, which encompasses the baseband, fundamental, and second harmonic regions of operation. These values are plotted on a logarithmic scale so that the baseband operating region is more clearly illustrated. The Y-axis plots power transfer, as between the first port 304 and the second port 306, in decibels (dB). Thus, a perfectly transmitted signal corresponds to 0dB, while a signal that terminates as well between the first port 304 and the second port 306 has a lower transmission value, e.g., a value below-5 dB (i.e., a power ratio of about 31%).
As can be seen, the baseband termination circuit 122 advantageously suppresses frequency values in the baseband frequency region (i.e., frequencies between 10Hz and about 560 MHz). Furthermore, the impedance response of the baseband termination circuit 122 is relatively flat, meaning that the baseband termination circuit 122 provides frequency independent baseband termination. At the same time, the fundamental frequency (i.e., a frequency at or near 2.15 GHz) is well transmitted. Thus, the baseband termination circuit 122 does not degrade the performance of the impedance matching circuit outside of the baseband range.
Terms such as "same," "matching," and "match" as used herein are intended to mean the same, nearly the same, or approximately the same, such that some reasonable amount of variation is contemplated without departing from the spirit of the invention. The term "constant" means not changing or changing, or slightly changing or changing again, such that some reasonable amount of change is contemplated without departing from the spirit of the invention. Furthermore, terms such as "first," "second," and the like, are used to describe various elements, regions, sections, etc. and are not intended to be limiting. Like terms refer to like elements throughout the specification.
The term "direct electrical connection" or "electrical connection" describes a permanent low impedance connection between electrically connected elements, such as a wire connection between related elements. In contrast, the term "electrically coupled" means that one or more intermediate elements configured to affect an electrical signal in some way (in the real or imaginary domain) are provided between the electrically coupled elements. These intermediate elements include active elements, such as transistors, and passive elements, such as inductors, capacitors, diodes, resistors, and the like.
Spatially relative terms (such as "below," "lower," "upper," and the like) are used for ease of description to explain the positioning of one element relative to a second element. These terms are intended to encompass different orientations of the device in addition to different orientations than those depicted in the figures.
As used herein, the terms "having," "containing," "including," "comprising," and the like are open-ended terms that indicate the presence of stated elements or features, but do not exclude additional elements or features. The articles "a", "an" and "the" are intended to include the plural as well as the singular, unless the context clearly indicates otherwise.
With the above range of variations and applications in mind, it should be understood that the present invention is not limited by the foregoing description, nor is it limited by the accompanying drawings. Instead, the present invention is limited only by the following claims and their legal equivalents.