Power amplifier with shielded transmission line

Abstract

A power amplifier module includes a first phase shifter, a second phase shifter, and an electromagnetic shield. The first phase shifter includes a first transmission line assembly that shifts a first amplified signal by a first phase angle. The second phase shifter includes a second transmission line assembly that shifts a second amplified signal by a second phase angle. The electromagnetic shield is arranged to protect the first transmission line assembly from interference by the second transmission line assembly. For example, the power amplifier module may have a Doherty amplifier configuration.

Description

Technical Field

[0001] The example embodiments disclosed herein generally relate to power amplification. Background Art

[0002] Power amplifiers are used in a variety of applications. In a wireless communication system, a power amplifier generates an amplified radio frequency (RF) signal to an antenna for conveying information such as calls and data. In terms of performance, a power amplifier can operate with maximum power efficiency when transmitting at or near saturation power. However, the power efficiency tends to decrease as the output power decreases.

[0003] Recently, the Doherty amplifier architecture has become a focus of attention for supporting wireless communication. A Doherty power amplifier can use different strategies, for example, based on the phase difference between a carrier amplifier (or "main amplifier") and a peak power amplifier. One type of Doherty power amplifier uses a 90 / 0 strategy, where a 90-degree phase shift is applied to the peak signal before amplification along the peak amplifier path, and a corresponding 90-degree phase shift and impedance inversion are applied to the carrier signal after amplification along the carrier amplifier path and before in-phase combining the amplified carrier and peak signals at a combining node. However, the 90 / 0 Doherty power amplifier has narrowband performance and thus cannot meet the requirements of many applications.

[0004] Another type of Doherty power amplifier uses a 90 / 180 strategy that provides a wider RF bandwidth. However, the currently designed 90 / 180 Doherty power amplifier is not suitable for use in the limited available space of a power amplifier module. Adding lumped components can help save space in some cases to enable the use of a 90 / 180 Doherty power amplifier, but there is an efficiency trade-off. Summary of the Invention

[0005] According to one aspect of the present invention, there is provided a power amplifier module, comprising: a first phase shifter configured to shift a first amplified signal by a first phase angle, wherein the first phase shifter includes a first transmission line assembly; a second phase shifter configured to shift a second amplified signal by a second phase angle different from the first phase angle, wherein the second phase shifter includes a second transmission line assembly; and an electromagnetic shield between the first phase shifter and the second phase shifter, wherein the electromagnetic shield is arranged to protect the first transmission line assembly from interference by the second transmission line assembly.

[0006] According to one or more embodiments, the electromagnetic shielding includes at least one vertical barrier, the at least one vertical barrier including one or more dielectric layers interleaved between a plurality of metal layers, the plurality of metal layers being electrically connected to at least one of the first transmission line assembly and the second transmission line assembly, and at least one of the plurality of metal layers including or being connected to a ground layer.

[0007] According to one or more embodiments, further comprising: a plurality of conductive vias extending through the one or more dielectric layers to connect a first metal layer of the metal layers to a second metal layer of the metal layers.

[0008] According to one or more embodiments, the first metal layer of the metal layers is connected to the first transmission line assembly, and the second metal layer of the metal layers is connected to the second transmission line assembly.

[0009] According to one or more embodiments, the second transmission line assembly includes first and second transmission lines, the first metal layer of the metal layers being connected to the first transmission line, and the second metal layer of the metal layers being connected to the second transmission line.

[0010] According to one or more embodiments, the electromagnetic shielding includes a patterned horizontal portion covering an area including at least one of the first transmission line assembly and the second transmission line assembly.

[0011] According to one or more embodiments, the patterned horizontal portion corresponds to one of the metal layers of the at least one vertical barrier.

[0012] According to one or more embodiments, the second transmission line assembly includes: a first transmission line that shifts the second amplified signal by a third phase angle, and a second transmission line that shifts the second amplified signal by a fourth phase angle, wherein the sum of the third phase angle and the fourth phase angle is equal to the second phase angle.

[0013] According to one or more embodiments, at least a portion of the electromagnetic shielding includes a vertical barrier arranged to shield the first transmission line from interference by the second transmission line.

[0014] According to one or more embodiments, the first transmission line is a first type of transmission line, and the second transmission line is a second type of transmission line different from the first type of transmission line.

[0015] According to one or more embodiments, the first transmission line assembly includes the first type of transmission line.

[0016] According to one or more embodiments, the first type is a shielded stripline and the second type is a microstrip.

[0017] According to another aspect of the present invention, there is provided a power amplifier module, comprising: a first amplifier configured to amplify a first signal; a first transmission line assembly coupled to an output of the first amplifier; a second amplifier configured to amplify a second signal; a second transmission line assembly coupled to an output of the second amplifier; and an electromagnetic shield between the first transmission line assembly and the second transmission line assembly, wherein the first transmission line assembly is configured to shift a phase of a first amplified signal by a first phase angle, and the second transmission line assembly is configured to shift a phase of a second amplified signal by a second phase angle different from the first phase angle.

[0018] According to one or more embodiments, the first amplifier is arranged along a carrier signal path, the second amplifier is arranged along a peak signal path, and the carrier and peak signal paths are in a Doherty amplifier configuration.

[0019] According to one or more embodiments, further comprising: a phase regulator configured to shift the first signal input to the first amplifier by a third phase angle, wherein a sum of the first phase angle and the third phase angle is substantially equal to the second phase angle.

[0020] According to one or more embodiments, the first phase angle is in a first range between 0° and 90°, and the second phase angle is in a second range between 90° and 180°.

[0021] According to one or more embodiments, further comprising: a combiner coupled to outputs of the first transmission line assembly and the second transmission line assembly.

[0022] According to one or more embodiments, the first transmission line assembly is coupled between the first amplifier and the combiner, and wherein the second transmission line assembly is coupled between the second amplifier and the combiner.

[0023] According to one or more embodiments, the electromagnetic shield includes at least one vertical barrier, the at least one vertical barrier includes one or more dielectric layers interleaved between a plurality of metal layers, the plurality of metal layers are electrically connected to at least one of the first transmission line assembly and the second transmission line assembly, and at least one of the plurality of metal layers includes or is connected to a ground layer.

[0024] According to one or more embodiments, further comprising: a plurality of conductive vias extending through the one or more dielectric layers to connect a first metal layer in the metal layers to a second metal layer in the metal layers.

[0025] According to one or more embodiments, the first metal layer in the metal layers is connected to the first transmission line assembly, and the second metal layer in the metal layers is connected to the second transmission line assembly.

[0026] According to one or more embodiments, the second transmission line assembly includes first and second transmission lines, the first metal layer in the metal layers is connected to the first transmission line, and the second metal layer in the metal layers is connected to the second transmission line.

[0027] According to one or more embodiments, the electromagnetic shielding includes a patterned horizontal portion covering an area including at least one of the first transmission line assembly and the second transmission line assembly.

[0028] According to one or more embodiments, the patterned horizontal portion corresponds to one of the metal layers in the at least one vertical barrier. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] When taken in conjunction with the drawings, additional objects and features of the present invention will become more apparent from the following detailed description and the appended claims. Although several example embodiments are shown and described, the same reference numerals identify the same parts in each of the drawings, wherein:

[0030] Figure 1 A schematic diagram showing an embodiment of a Doherty power amplifier;

[0031] Figure 2 A top view showing an embodiment of a power amplifier module;

[0032] Figure 3 Showing Figure 2 Another view of the power amplifier module;

[0033] Figure 4 A cross-sectional view showing an embodiment of a stripline transmission line;

[0034] Figure 5 A cross-sectional view showing an embodiment of a microstrip transmission line;

[0035] Figure 6 Showing Figure 2 And Figure 3 A top view of the module, further illustrating an embodiment of electromagnetic shielding; and

[0036] Figure 7Cross-sectional view showing an embodiment of a substrate. Detailed Description

[0037] It should be understood that the drawings are merely schematic and not drawn to scale. It should also be understood that throughout the drawings, the same reference numerals are used to indicate the same or similar parts.

[0038] The description and the figures illustrate the principles of various example embodiments. Thus, it will be understood that although not explicitly described or shown herein, those skilled in the art will be able to design various arrangements that embody the principles of the present invention and fall within the scope of the present invention. In addition, all the examples recited herein are mainly and explicitly intended for teaching purposes to assist the reader in understanding the principles of the present invention and the concepts proposed by the inventors, thereby deepening the art, and should be understood as not being limited to such specifically recited examples and circumstances. Additionally, unless otherwise indicated (e.g., "otherwise" or "in an alternative"), as used herein, the term "or" refers to a non-exclusive or (i.e., and / or). And the various example embodiments described herein are not necessarily mutually exclusive, as some example embodiments may be combined with one or more other example embodiments to form new example embodiments. For example, the descriptions such as "first", "second", "third", etc. are not intended to limit the order of the elements discussed, but are used to distinguish one element from the next and are generally interchangeable. For example, the values of maximum or minimum values may be predetermined and set to different values based on the application.

[0039] Example embodiments describe a unique broadband power amplifier having a Doherty configuration using hybrid transmission lines and a shielding structure. This power amplifier can be effectively implemented within the limited space of a module platform and is suitable for use in many applications. In one embodiment, the power amplifier has a 90 / 180 Doherty configuration that exhibits high efficiency across a wide frequency band. The combined node impedance of this power amplifier can be selected, for example, as 50 Ω and can be implemented without an impedance transformer in many other designs. The amplifier can also reduce dispersion and reduce or eliminate the use of lumped components.

[0040] Figure 1 Schematic diagram showing an embodiment of a Doherty power amplifier 100, where an embodiment of a shielding structure can be implemented as described later. In one embodiment, the Doherty power amplifier 100 is implemented as a module (e.g., Figure 2 , Figure 3 , Figure 6 the module 200 in), where various components of the Doherty amplifier are integrated within or coupled to a module substrate (e.g., Figure 2 , Figure 3 , Figure 6 , Figure 7 the substrates 202, 700 in).

[0041] The Doherty amplifier 100 includes an input node 2, an output node 4, a power splitter 10 (or divider), a main amplifier path 20 (or "first signal path"), a peak amplifier path 30 (or "second signal path"), and a combining node 40. In an embodiment, a load 60 (e.g., an antenna) can be coupled to the combining node 40 via an impedance transformer 50 and a DC blocking capacitor 52. The impedance transformer 50 can impose a 90-degree phase delay on the signal before the output RF signal is supplied to the load 60. The DC blocking capacitor 52 can perform a high-pass filter operation, allowing the higher-frequency (AC) portion of the amplified signal to pass and blocking the lower-frequency (DC) portion of the amplified signal. One or more additional capacitors can be coupled to the input and / or output of the power amplifier module package for RF impedance matching.

[0042] The main amplifier path 20 includes a phase delay element 22, an input matching network 23, a main amplifier stage 24, an output matching network 25, and a first transmission line assembly 26. The peak amplifier path 30 includes an input matching network 31, a peak amplifier stage 32, an output matching network 33, and a second transmission line assembly 34. Basically, the power splitter 10 divides the input RF signal supplied at the input node 2 and amplifies the divided signals along the main amplifier path 20 and the peak amplifier path 30, respectively. The amplified signals are then combined in-phase at the combining node 40. Importantly, the phase coherence between the main amplifier path 20 and the peak amplifier path 30 is maintained over the frequency band of interest to ensure that the amplified main signal and peak signal arrive at the combining node 40 in-phase and thus ensure the proper operation of the Doherty amplifier.

[0043] Each of the main amplifier 24 and the peak amplifier 32 includes one or more single-stage or multi-stage power transistor integrated circuits (ICs) for amplifying the RF signal conducted through the amplifiers 24, 32. Although the main power transistor IC and the peak power transistor IC can have equal sizes (e.g., in a symmetric Doherty configuration), the main power transistor IC and the peak power transistor IC can also have unequal sizes (e.g., in various asymmetric Doherty configurations). In an asymmetric Doherty configuration, the peak power transistor IC is typically several times larger than the main power transistor IC. For example, the size of the peak power transistor IC can be twice the size of the main power transistor IC, such that the current-carrying capacity of the peak power transistor IC is twice the current-carrying capacity of the main power transistor IC. Peak-to-main amplifier IC size ratios other than the 2:1 ratio can also be implemented.

[0044] During operation of the Doherty amplifier 100, the main amplifier stage 24 is biased to operate in class AB mode, and the peaking amplifier stage 32 is biased to operate in class C mode. More specifically, the transistor arrangement of the main amplifier stage 24 is biased to provide a conduction angle between 180 degrees and 360 degrees. Conversely, the transistor arrangement of the peaking amplifier stage 32 is biased to provide a conduction angle less than 180 degrees.

[0045] At low power levels, when the power of the input signal at node 2 is below the turn-on threshold level of the peaking amplifier 32, the amplifier 100 operates in a low power (or back-off) mode, in which the main amplifier 24 is the only amplifier supplying current to the load 60. When the power of the input signal exceeds the threshold level of the peaking amplifier 32, the amplifier 100 operates in a high power mode, in which both the main amplifier 24 and the peaking amplifier 32 supply current to the load 60. At this time, the peaking amplifier 32 provides active load modulation at the combined node 40, thereby allowing the current of the main amplifier 24 to continue to increase linearly.

[0046] The power divider 10 is configured to divide the input power of the RF input signal received at input 2 into a main portion and a peaking portion of the input signal. The main input signal is provided to the main amplifier path 20 at the first power divider output, and the peaking input signal is provided to the peaking amplifier path 30 at the second power divider output. During operation in full power mode, i.e., when both the main amplifier 24 and the peaking amplifier 32 supply current to the load 60, the power divider 10 divides the input signal power between the amplifier paths 20, 30. For example, the power divider 10 may divide the power equally, such that approximately half of the input signal power is provided to each path 20, 30 (e.g., for a symmetric Doherty amplifier configuration). Alternatively, the power divider 10 may divide the power unequally (e.g., for an asymmetric Doherty amplifier configuration).

[0047] Input and output impedance matching networks 23, 25 (input MNm, output MNm) may be implemented at the input and / or output of the main amplifier 24. Similarly, input and output impedance matching networks 31, 33 (input MNp, output MNp) may be implemented at the input and / or output of the peaking amplifier 32. In each case, the matching networks 23, 25, 31, 33 can be used to incrementally increase the circuit impedance to the load impedance and the power supply impedance. Additionally, the main amplifier 24 and the peaking amplifier 32 may have additional pre-matching input and / or output impedance matching networks ( Figure 1 not shown in the figure), which are integrated with the power transistor die or integrated within the power transistor die package.

[0048] Compared with a conventional non-inverted Doherty amplifier, the Doherty amplifier 100 has an "inverted" load network configuration. In the inverted configuration, the input circuit is configured such that the input signal supplied to the main amplifier 24 is delayed by 90 degrees relative to the input signal supplied to the peak amplifier 32 at the center operating frequency fo of the amplifier 100. For example, a 90-degree differential delay between the main path 20 and the peak path 30 can be imparted to the input circuit by a 90-degree phase delay element 22 in the main amplifier path 20. For example, the phase delay element 22 can be a quarter-wave transmission line or another suitable type of delay element having an electrical length of approximately 90 degrees. Alternatively, the power divider 10 and the phase delay element 22 can be replaced by a hybrid power splitter (not shown) that outputs a main signal and a peak signal having the desired 90-degree phase difference.

[0049] According to the operating principle of the "inverted" Doherty amplifier 100 and in order to establish the correct load modulation characteristics, the main output path including the first transmission line assembly 26, the output matching network 25, and any output pre-matching within the main amplifier device 24 (i.e., the transmission path between the output of the amplifier 24 and the combinational node 40) is configured to impart a total phase delay of approximately 90 degrees to the amplified RF signal transmitted through the main output path. Additionally, the peak output path including the second transmission line assembly 34, the output matching network 33, and any output pre-matching within the peak amplifier device 32 (i.e., the transmission path between the output of the amplifier 32 and the combinational node 40) is configured to impart a total phase delay of approximately 180 degrees to the amplified RF signal transmitted through the peak output path. Thus, the Doherty amplifier 100 can be referred to as a 90 / 180 Doherty power amplifier. As discussed above, the main amplifier input path (i.e., the transmission path between the first output of the splitter 10 and the input to the main amplifier 24) applies a phase delay of approximately 90 degrees to the input RF signal before the input RF signal reaches the input of the main amplifier 24 to compensate for the 90-degree phase delay difference between the main amplifier output path and the peak amplifier output path (i.e., to ensure that the amplified signals arrive at the combinational node 40 in phase).

[0050] Amplifier 24 may include a power transistor having an input (or control) terminal (e.g., gate terminal) coupled to splitter 10 through phase delay element 22, a first conductive terminal (e.g., source terminal) coupled to a reference potential (e.g., ground), and a second conductive terminal (e.g., drain) coupled to first transmission line assembly 26. Similarly, amplifier 32 may include a power transistor having an input (or control) terminal (e.g., gate terminal) coupled to splitter 10, a first conductive terminal (e.g., source terminal) coupled to a reference potential (e.g., ground), and a second conductive terminal (e.g., drain) coupled to second transmission line assembly 34. For example, the power transistor may include a silicon-based field effect transistor (FET), such as a laterally diffused metal oxide semiconductor (LDMOS) FET, a gallium nitride FET, and / or a gallium arsenide FET, to name a few.

[0051] In this embodiment, first transmission line assembly 26 includes only one transmission line 28 (TL1) that shifts the phase of the amplified carrier signal by a predetermined angle. Thus, the signal output from transmission line assembly 26 represents an amplified carrier signal that has been in-phase shifted by both phase regulator 22 and transmission line assembly 26. Since phase regulator 22 regulates the phase of the carrier signal input to power transistor 24, the total phase shift of the signal input to combiner 40 from first signal path 20 includes the sum of the phase shift applied by phase regulator 22 and the phase shift applied by transmission line assembly 26.

[0052] Second transmission line assembly 34 may include a plurality of transmission lines, such as transmission line 36 (TL2) and transmission line 38 (TL3) connected in series. Transmission line 36 may shift the phase of the amplified peak signal by a first predetermined angle, and transmission line 38 may shift the phase of the amplified peak signal output from transmission line 36 by a second predetermined angle. The first and second predetermined angles may be the same or different. Also, the sum of the first and second predetermined angles may be different from the phase angle shift applied by first transmission line assembly 28 in the carrier signal path. Although transmission line assembly 34 is shown as including two transmission lines 36 and 38 connected in series, in another embodiment, second transmission line assembly 34 may include only one transmission line that shifts the amplified peak signal by a phase angle equal to the sum of the phase angles applied by transmission lines 36 and 38. Thus, the signal output from second transmission line assembly 34 represents an amplified peak signal that has been in-phase shifted based on the sum corresponding to the phase angles of transmission lines 36 and 38.

[0053] In one embodiment, the power amplifier module has a Doherty 90 / 180 configuration, where the first transmission line component (e.g., transmission line 28) together with other delay components between the intrinsic drain of amplifier 24 and the combined node 40 shift the phase of the amplified carrier signal by about 90°, and the second transmission line component (e.g., transmission lines 36 and 38 together) together with other delay components between the intrinsic drain of amplifier 32 and the combined node 40 shift the phase of the amplified carrier signal by about 180°.

[0054] To further improve performance, the impedance values of all three transmission lines 28, 36, and 38 can be selected to achieve impedance matching therebetween. For example, to achieve an output impedance that matches the input impedance of a load (e.g., Z load = 50 Ω), the first transmission line (TL2) 36 can have a characteristic impedance of about 23 Ω, the second transmission line (TL3) 38 can have a characteristic impedance of about 72 Ω on the peak signal path, and the transmission line 28 on the carrier signal path (TL1) can have a characteristic impedance of about 53 Ω. The impedance can be achieved at least in part by changing the width of the transmission line. For example, a wider transmission line can have less impedance and vice versa.

[0055] The Doherty power amplifier 100 described above has an inverting topology as discussed above. In an alternative embodiment, the Doherty power amplifier 100 can have a non-inverting Doherty topology, where an opposite relationship is applied between the delay elements in the main path 20 and the peak path 30. More precisely, in the non-inverting Doherty topology, the phase delay element 22 will be implemented along the peak input path instead of the main input path. Additionally, the main output path will include a total phase delay that compensates for the phase delay element 22 along the peak input path. For example, the main output path can have a total phase delay of about 90 degrees, while the peak output path can have substantially no phase delay (0 degrees).

[0056] Figure 2 Shows an embodiment of a power amplifier module 200 embodying Figure 1 a Doherty power amplifier 100 in a top view, and Figure 3 shows additional views of the module 200 from different perspectives.

[0057] The power amplifier module 200 (or “Doherty amplifier module”) includes a substrate 202, a power splitter 210 (e.g., Figure 1 the power splitter 10 in Figure 1 ), a phase delay element 222 (e.g., Figure 1 the phase delay element 22 in Figure 1the peak amplifier 32), the first transmission line assembly 226 (e.g., Figure 1 the first transmission line assembly 26) in, the second transmission line assembly 234 (e.g., Figure 1 the second transmission line assembly 34) in, the combining node 240 (e.g., Figure 1 the combining node 40) in, and various other circuit elements will be discussed in detail below.

[0058] For example, the power amplifier module 200 may be implemented as a land grid array (LGA) module. Accordingly, the substrate 202 has a component mounting surface 212 (also referred to herein as the "upper" or "top" surface) and a pad surface 214 (also referred to herein as the "lower" or "bottom" surface). The conductive pad pads of the LGA are exposed at the pad surface 214. Although the module 200 is depicted as an LGA module, the module 200 may alternatively be packaged as a pin grid array module, a quad flat no-lead (QFN) module, or another type of package. Either way, the component mounting surface 212 and the components mounted to the surface 212 may optionally be covered with a sealant material (e.g., Figure 7 the sealant material 730 in, such as a plastic sealant). In an alternative embodiment, the components may be housed within an air cavity defined by various structures (not shown) overlying the mounting surface 212.

[0059] According to an embodiment, the substrate 202 is relatively small, which provides a particularly compact Doherty amplifier. For example, the component mounting surface 212 may have a width ( Figure 2 the horizontal dimension in) in the range of about 5 millimeters (mm) to about 20 mm and a length ( Figure 2 the vertical dimension in), but the width and / or length may also be smaller or larger. In a specific embodiment, for example, the component mounting surface may have a width of about 10 mm and a length of about 6 mm.

[0060] A plurality of non-overlapping regions are defined at the mounting surface 212 of the substrate 202. In the input signal and splitter regions, the conductive pad pads exposed at the pad surface 214 are electrically coupled through the substrate 202 to the conductive contacts at the mounting surface 212. The pad pads and the contacts, along with the electrical connections therebetween, act as an RF input node for the module 200 (e.g., Figure 1 the RF input 2).

[0061] The power splitter 210 is coupled to the mounting surface 212 in the input signal region. According to an embodiment, the power splitter 210 may include one or more discrete die and / or components, but in Figure 2The medium power splitter 210 is presented as a single element. The power splitter includes an input terminal and two output terminals. The input terminal is electrically coupled to the RF input node to receive an input RF signal. The output terminals are electrically coupled to conductive traces on the mounting surface 212, and the conductive traces connect the output terminals to the inputs (e.g., gate terminals) of the carrier amplifier die 224 and the peak amplifier die 232.

[0062] The power splitter 210 is configured to split the power of the input RF signal received through the input terminal into first and second RF signals (e.g., a carrier signal and a peak signal), and the first and second RF signals are generated at the output terminals. In addition, the power splitter 210 may include one or more phase shift elements configured to apply a phase difference of approximately 90 degrees between the first and second RF signals provided at the output terminals. Alternatively, a phase delay element 222 (e.g., Figure 1 the phase delay element 22) may be provided along the path between one of the power splitter output terminals and the input to the carrier amplifier die 224.

[0063] The first and second RF signals may have equal or unequal power, as previously discussed. The first RF signal generated at the first output terminal is amplified through a carrier amplifier path (e.g., Figure 1 the carrier path 20). The carrier amplifier path includes the carrier amplifier die 224 and the first transmission line assembly 226.

[0064] Each of the transistors 224 and 232 may be a field effect transistor (FET) (e.g., a metal oxide semiconductor FET (MOSFET), a laterally diffused MOSFET (LDMOS FET), a high electron mobility transistor (HEMT), etc.). Alternatively, each of the transistors 224 and 232 may be a bipolar junction transistor (BJT). The references herein to "gate," "drain," and "source" which are commonly used to describe FETs are not intended to be limiting, as each of these names has similar characteristics for BJT implementations. In various embodiments, the semiconductor substrate on which the transistors 224 and 232 are formed may include silicon, silicon on insulator (SOI), silicon on sapphire (SOS), gallium arsenide (GaAs), gallium nitride (GaN), GaN on silicon carbide, GaN on silicon, or other types of substrate materials.

[0065] The carrier amplifier die 224 generates an amplified RF carrier signal at the RF output terminal (e.g., drain terminal) of the die 224. In addition, the peak amplifier die 232 generates an amplified RF peak signal at the RF output terminal (e.g., drain terminal) of the die 232.

[0066] The first end of the first transmission line assembly 226 (e.g., the first transmission line assembly 26) is electrically connected to the output end (e.g., the drain end) of the carrier amplifier die 224 through a wire bond array 225 (or another conductive connection). The second end of the first transmission line assembly 226 is electrically connected to the combined node 240. Similarly, the first end of the second transmission line assembly 234 (e.g., the second transmission line assembly 26) is electrically connected to the output end (e.g., the drain end) of the peak amplifier die 232 through another wire bond array 233 (or another conductive connection). The second end of the second transmission line assembly 234 is also electrically connected to the combined node 240.

[0067] The first transmission line assembly 226 includes a first transmission line 228 (e.g., Figure 1 transmission line 28). According to an embodiment, the first transmission line 228 is implemented by a transmission line having an electrical length less than lambda / 4 (λ / 4) (e.g., less than 90 degrees) (e.g., a shielded strip line as described in connection with Figure 4 ), where λ corresponds to the wavelength of the center frequency within the amplifier operating bandwidth implemented in the module 200.

[0068] The second transmission line assembly 234 includes a second transmission line 236 and a third transmission line 238 (e.g., Figure 1 transmission lines 36, 38) coupled in series. More specifically:

[0069] - The first end of the second transmission line 236 (corresponding to the first end of the second transmission line assembly 234) is coupled to the output end (e.g., the drain end) of the peak amplifier die 232;

[0070] - The second end of the second transmission line 236 is coupled to the first end of the third transmission line 238; and

[0071] - The second end of the third transmission line 238 (corresponding to the second end of the second transmission line assembly 234) is coupled to the combined node 240.

[0072] According to an embodiment, the second transmission line 236 is implemented by a first type of transmission line (e.g., a shielded strip line as described in connection with Figure 4 ), and the third transmission line 238 is implemented by a second type of transmission line (e.g., as described in connection with Figure 5implemented as described for the microstrip transmission line). In an embodiment, the combined electrical length of the second transmission line 236 and the third transmission line 238 is less than lambda / 2 (λ / 2) (e.g., less than 180 degrees). In some embodiments, the second transmission line 236 and the third transmission line 238 have substantially equal electrical lengths. In other embodiments, the second transmission line 236 may provide 25% to 75% of the total electrical length of the second transmission line assembly 234, and the third transmission line 238 may provide the remainder of the total electrical length of the second transmission line assembly 234.

[0073] As noted above, the transmission lines 228, 236, and 238 may be of the same type or different types of transmission lines. In one embodiment, the transmission lines 228 and 236 are shielded striplines and the transmission line 238 is a microstrip transmission line. In another embodiment, the transmission lines may be different combinations of transmission line types. In an embodiment, the transmission lines 228, 236, and 238 are integrally formed with the module substrate 202 (e.g., Figure 7 substrate 700). Referring briefly to Figure 7 , the substrate 700 (or substrate 202) includes a plurality of metal layers 701-705, with dielectric layers 710 interleaved between adjacent metal layers 701-705, and conductive vias 720 electrically connecting portions of the metal layers 701-705. Specifically, when there are different transmission line types, the signal-carrying portions of the transmission lines 223, 236, and 238 may be implemented on different metal layers. For example, the signal-carrying portion of a microstrip transmission line (e.g., transmission line 238) may be a patterned portion of metal layer 701, the signal-carrying portion of a shielded stripline transmission line (e.g., transmission line 236) may be a patterned portion of metal layer 702 (to allow for a ground shield structure to be included at the higher metal layer 701), and the signal-carrying portion of another shielded stripline transmission line (e.g., transmission line 228) may be a patterned portion of metal layer 703 (to allow for a ground shield structure to be included at the higher metal layer 701). Conductive vias (e.g., via 720) can be used to electrically connect the transmission lines when the transmission lines 228, 236, and 238 are implemented on different metal layers. In an alternative embodiment, the signal-carrying portions of the transmission lines 228, 236, and 238 can be implemented on the same metal layer, provided that a ground shield structure can be formed on at least some of the transmission lines (e.g., the metal layer having the signal-carrying portions of the transmission lines 228, 236, and 238 can be lower than layer 701 such that a portion of layer 701 can provide a ground shield structure).

[0074] To prevent mutual coupling between the transmission lines, the module 200 includes an electromagnetic shield. In a more specific embodiment, the transmission lines 228, 236, and 238 and the electromagnetic shield are all integrally formed with the module substrate 202 (e.g., Figure 7is integrally formed with the substrate 700). Briefly referring to Figure 7 The substrate 700 (or substrate 202) includes a plurality of metal layers 701-705, where dielectric layers 710 are interleaved between adjacent metal layers 701-705, and conductive vias 720 electrically connect portions of the metal layers 701-705.

[0075] In this embodiment, the signal-carrying conductors of the transmission lines 228, 236, and 238 have a curved configuration to increase the line length and thus most effectively utilize the space in the package. For example, the first transmission line 228 includes a first plurality of serially connected transmission line segments, the transmission line segments including first, second, and third elongated segments arranged in parallel with each other, and two 180-degree curved segments respectively connecting the first and second elongated segments and the second and third elongated segments. The second transmission line 236 includes a second plurality of serially connected transmission line segments, the transmission line segments including fourth, fifth, and sixth elongated segments arranged in parallel with each other, two 180-degree curved segments respectively connecting the fourth and fifth elongated segments and the fifth and sixth elongated segments, and a 90-degree curved segment connecting between the end of the sixth elongated segment and the first end of the third transmission line 238. Finally, the third transmission line 238 includes a third plurality of serially connected transmission line segments, the transmission line segments including seventh, eighth, and ninth elongated segments arranged in parallel with each other, two 180-degree curved segments respectively connecting the seventh and eighth elongated segments and the eighth and ninth elongated segments, and a 90-degree curved segment connecting between the end of the ninth elongated segment and the combined node 240.

[0076] As will be more apparent from the following description, the signal-carrying conductors of the second transmission line 236 and the third transmission line 238 can be implemented in different metal layers of the substrate 202, and the transmission lines are serially electrically connected between the first and second ends. Accordingly, one or more conductive vias can be used to electrically connect the second transmission line 236 and the third transmission line 238. As used herein, the "region" occupied by the transmission lines 228, 236, and 238 can be considered to cover the two-dimensional region (e.g., plane) of the plurality of serially connected transmission line segments for the transmission lines 228, 236, and 238. As Figure 2 shown, the regions occupied by the transmission lines generally do not overlap and are adjacent to each other, and at least some of the various conductive barriers 250 and 270 discussed below are close to the boundaries between the regions occupied by the transmission lines 228, 236, and 238.

[0077] The electromagnetic shielding includes a first conductive vertical barrier 250, a second conductive vertical barrier 260, a third conductive vertical barrier 270, and a fourth conductive vertical barrier 280, where "vertical" as used herein indicates a direction perpendicular to Figure 2 the page (conversely, "horizontal" as used herein represents a direction parallel to Figure 2in a direction coplanar with the page). Each of the barriers 250, 260, 270, and 280 can be formed by conductive vias within the substrate 202. In addition to the barriers 250, 260, 270, 280, the electromagnetic shielding can also include patterned horizontal portions of one or more metal layers (e.g., patterned portions of layer 701, 702, or other layers). Additional barriers can be included to protect additional sides of the transmission line and / or other features on the package.

[0078] The first barrier 250 is disposed between the transmission line 228 along the carrier signal path and the third transmission line 238 along the peak signal path. According to an embodiment, the first barrier 250 is a vertical barrier including one or more conductive vias (e.g., vias that interconnect two metal layers (e.g., layer 701 and 703) or portions of other metal layer sets through one or more dielectric layers 710). As Figure 3 best shown, the vias of the first barrier 250 can be trench vias, or the vias of the first barrier 250 can have another cross-section (e.g., circular). Although not depicted in Figure 2 and Figure 3 the vias of the first barrier 250 are electrically coupled to a ground node (e.g., electrically coupled to a conductive ground node at the bottom surface 214 of the substrate 202).

[0079] The second barrier 260 is disposed between the transmission line 228 and the carrier amplifier die 224 including a power amplifier for the carrier signal, and is also disposed between the transmission line 228 and the combination node 240 and the capacitor 252 (e.g., Figure 1 capacitor 52). According to an embodiment, the second barrier 260 is also a vertical barrier including one or more conductive vias (vias that interconnect two metal layers (e.g., layer 701 and 703) or portions of other metal layer sets through one or more dielectric layers 710). As Figure 3 best shown, the vias of the second barrier 260 can be trench vias, or the vias of the second barrier 260 can have another cross-section (e.g., circular). Although not depicted in Figure 2 and 3 the vias of the second barrier 260 are electrically coupled to a ground node (e.g., electrically coupled to a conductive ground node at the bottom surface 214 of the substrate 202).

[0080] The third barrier 270 is disposed between the transmission lines 228 and 236, and is also between the transmission lines 236 and 238. According to an embodiment, the third barrier 270 is also a vertical barrier including one or more conductive vias (e.g., vias that interconnect two metal layers (e.g., layer 701 and 703) or portions of other metal layer sets through one or more dielectric layers 710). As Figure 3Best shown in, the through - holes of the third barrier 270 can be trench through - holes, or the through - holes of the third barrier 270 can have another cross - section (e.g., circular). Although not depicted in Figure 2 and Figure 3 the through - holes of the third barrier 270 are electrically coupled to a ground node (e.g., electrically coupled to a conductive ground node at the bottom surface 214 of the substrate 202).

[0081] As described above, one or more fourth barriers 280 are arranged between parallel segments of the second transmission line 236 and are also arranged between the second transmission line 236 and the peak amplifier die 232 including a power amplifier for peak signals. According to an embodiment, the fourth barrier 280 is also a vertical barrier, and each of the fourth barriers includes one or more conductive through - holes (e.g., through - holes that interconnect two metal layers (e.g., layers 701 and 703) or portions of other metal layer sets through one or more dielectric layers 710). As Figure 3 Best shown in, the through - holes of the fourth barrier 280 can be trench through - holes, or the through - holes of the fourth barrier 280 can have another cross - section (e.g., circular).

[0082] A portion of the barrier 280 can be staggered between adjacent segments of the second transmission line 236 to provide improved electromagnetic shielding performance. Although not depicted in Figure 2 and Figure 3 the through - holes of the fourth barrier 280 are electrically coupled to a ground node (e.g., electrically coupled to a conductive ground node at the bottom surface 214 of the substrate 202).

[0083] The barriers providing electromagnetic shielding are shown as discrete components arranged side - by - side. In another embodiment, each of the barriers can be formed as a continuous wall, or all of the barriers can be formed by only one continuous wall with rod - like through - holes or standard through - holes.

[0084] As Figure 6 Best shown in, in addition to including barriers 250, 260, 270, and 280, the electromagnetic shielding also includes a patterned horizontal portion 650 of one or more metal layers. For example, in an embodiment, the transmission line 236 can be a shielded stripline, the shielded stripline including the transmission line 236 in one metal layer (e.g., Figure 7 the metal layer 702 of Figure 7electromagnetic shielding of the overlying portion of a metal layer (e.g., metal layer 701) and the underlying portion of a metal layer (e.g., metal layer 703), wherein the overlying and underlying portions of the metal layer are electrically connected by conductive barriers 270 and 280. Additionally, the overlying and underlying portions of the metal layer have regions that generally cover the area occupied by transmission line 236. Similarly, for example, in an embodiment, transmission line 228 can be a shielded stripline that includes transmission line 228 in one metal layer (e.g., Figure 7 metal layer 703) and electromagnetic shielding of the overlying portion of a metal layer (e.g., Figure 7 metal layer 701) and the underlying portion of a metal layer (e.g., metal layer 705), wherein the overlying and underlying portions of the metal layer are electrically connected by conductive barriers 250, 260, and 270. Additionally, the overlying and underlying portions of the metal layer have regions that generally cover the area occupied by transmission line 228. Figure 6 shows a patterned horizontal portion 650 of a metal layer (e.g., Figure 7 layer 701) overlying transmission lines 228 and 236. A similarly shaped patterned horizontal portion of another metal layer (e.g., Figure 7 layer 703) underlies transmission lines 228 and 236, and the overlying and underlying patterned metal layer portions are electrically connected by conductive barriers 250, 260, 270, and 280.

[0085] Figure 4 shows an embodiment of a shielded stripline, e.g., transmission line 28 (TL1) and transmission line 36 (TL2). For a shielded stripline configuration (shown in a cross-sectional assembly), five layers can be used. The first layer 410 is a lower ground (metal) layer, the second layer 420 is a dielectric layer, the third layer 430 is a patterned conductive (metal) signal layer, the fourth layer 440 is another dielectric layer, and the fifth (metal) layer 450 is an upper ground (metal) layer. The signal layer 430 includes metal patterns for the transmission lines (e.g., TL1 and TL2). The dielectric layers are provided to prevent short circuits between the transmission line layer 430 and the lower ground layer 410 and the upper ground layer 450.

[0086] Figure 5 shows an embodiment of a microstrip transmission line, e.g., transmission line 38 (TL3). For a microstrip configuration (shown in cross-section), three layers can be used. The first layer 510 can be a lower ground (metal) layer, the second layer 520 can be a dielectric layer, and the third layer 530 can be a patterned conductive (metal) signal layer that includes the transmission line pattern. In this embodiment, no additional dielectric layer and ground layer are required. In Figure 4 and Figure 5In an embodiment, the lower ground layers 410 and 510 can be the same layer, and the dielectric layers 420 and 520 can be the same layer. Also, the signal layers 430 and 530 can be coplanar but include different metal patterns corresponding to different arrangements of the transmission lines.

[0087] As previously mentioned, Figure 6 shows Figure 2 and Figure 3 a plan view (or top view) of an exemplary configuration of a portion of the electromagnetic shield in Figure 6 The electromagnetic shield shown shows the configuration of the patterned conductive upper shield or ground layer 650 (e.g., Figure 4 the upper ground layer 450 in Figure 6 overlying the signal line / layer of the transmission lines when the transmission lines 28, 228 (TL1) and the transmission lines 36, 236 (TL2) are implemented as shielded striplines. The microstrip transmission line may not have an upper ground layer. Thus,

[0088] Figure 7 shows an embodiment of a substrate 700 that can be used to implement shielded striplines and microstrip transmission lines within the package 200 of a power amplifier module. More specifically, Figure 7 is a cross-sectional view of a substrate 700 (e.g., a printed circuit board, a multi-layer ceramic substrate, or other suitable substrate) that supports and electrically connects the various components of the power amplifier module. The substrate 700 includes a plurality of metal layers 701, 702, 703, 704, and 705 (or M1 to M5), with dielectric layers 710 (e.g., ceramic, FR-4, or other suitable material) interleaved between adjacent metal layers 701-705. Although the substrate 700 is shown as including five metal layers 701-705 and four interleaved dielectric layers 710, other embodiments of the substrate may include more or fewer metal layers and dielectric layers. Conductive vias 720 (only a few conductive vias are shown by way of example) extend through the dielectric layer 710 to electrically connect portions of the metal layers 701-705 when needed. For example, additional dielectric 730 is adjacent to the top surface of the substrate 700, and the dielectric can be air or a plastic sealant.

[0089] The metal layers 701-705 can be arranged and patterned to implement the transmission lines TL1, TL2, and TL3 (e.g., Figure 2 the transmission lines 228, 236, and 238 in Figure 4 ). For example, TL1 and TL2 are shielded transmission lines and can include patterned signal lines implemented in a conductive signal layer (e.g., Figure 4A patterned conductive shielding structure implemented in the layers 410, 450), where the conductive ground layer is located below and above the conductive signal layer. For example, in the substrate 700, the patterned conductive shielding structure is implemented as part of the metal layers 701 and 703, and the patterned signal lines can be implemented as the patterned part of the metal layer 702. The patterned conductive shielding structures can be electrically connected together through vias 720, and the patterned conductive shielding structures can be electrically connected to the lowest metal layer 705 (e.g., the ground metal layer provided at the bottom of the substrate 700) using additional vias 720.

[0090] As another example, TL3 is a microstrip transmission line, which can include a patterned signal line implemented in a conductive signal layer (e.g., Figure 5 the layer 530), and a conductive ground structure implemented in a conductive ground layer (e.g., Figure 5 the layer 510), where the conductive ground layer is located below the conductive signal layer. For example, in the substrate 700, the conductive ground structure can be implemented as the metal layer 705, and the patterned signal lines can be implemented as the patterned part of the metal layer 701. Although the above description indicates that the conductive signal lines and the associated ground structures can be implemented in various metal layers, in other embodiments, the signal lines and the ground structures can be present on different metal layers.

[0091] To make the description clearer, the following table provides examples of sets of metal layers ( Figure 7 ) that can be used to implement the first transmission lines 28, 228, the second transmission lines 36, 236, and the third transmission lines 38, 238. It should be understood that this table is provided for illustrative purposes and not for limitation, and various transmission lines can be implemented using sets of layers different from those listed in the following table.

[0092] Transmission line Signal layer Top shield Bottom shield / ground layer TL1(28, 228) M3(703) M1(701) M5(705) TL2(36, 236) M2(702) M1(701) M3(703) and lower layers TL3(38, 238) M1(701) Not applicable M5(705)

[0093] According to one or more of the above embodiments, a power amplifier module includes a first phase shifter configured to shift a first amplified signal by a first phase angle, where the first phase shifter includes a first transmission line assembly; a second phase shifter configured to shift a second amplified signal by a second phase angle different from the first phase angle. The second phase shifter includes a second transmission line assembly, and an electromagnetic shield is located between the first phase shifter and the second phase shifter, where the electromagnetic shield is arranged to protect the first transmission line assembly from interference by the second transmission line assembly.

[0094] The electromagnetic shielding may include at least one vertical barrier. The at least one vertical barrier includes one or more dielectric layers interleaved between a plurality of metal layers. The plurality of metal layers may be electrically connected to at least one of the first transmission line assembly and the second transmission line assembly, and at least one of the plurality of metal layers includes or is connected to a ground layer.

[0095] The power amplifier module may include a plurality of conductive vias that extend through the one or more dielectric layers to connect a first metal layer of the metal layers to a second metal layer of the metal layers. The first metal layer of the metal layers may be connected to the first transmission line assembly, and the second metal layer of the metal layers may be connected to the second transmission line assembly. The second transmission line assembly may include first and second transmission lines, the first metal layer of the metal layers may be connected to the first transmission line, and the second metal layer of the metal layers may be connected to the second transmission line.

[0096] The electromagnetic shielding may include a patterned horizontal portion that covers an area including at least one of the first transmission line assembly and the second transmission line assembly. The patterned horizontal portion may correspond to one of the metal layers of the at least one vertical barrier. The second transmission line assembly may include a first transmission line that shifts the second amplified signal by a third phase angle; and a second transmission line that shifts the second amplified signal by a fourth phase angle, wherein the sum of the third phase angle and the fourth phase angle may be equal to the second phase angle. At least a portion of the electromagnetic shielding may include a vertical barrier arranged to shield the first transmission line from interference by the second transmission line.

[0097] The first transmission line may be a first type of transmission line, and the second transmission line may be a second type of transmission line different from the first type of transmission line. The first transmission line assembly may include the first type of transmission line. The first type may be a shielded stripline, and the second type may be a microstrip.

[0098] According to one or more other embodiments, a power amplifier module includes a first amplifier configured to amplify a first signal; a first transmission line assembly coupled to the output of the first amplifier; a second amplifier configured to amplify a second signal; a second transmission line assembly coupled to the output of the second amplifier; and an electromagnetic shield between the first transmission line assembly and the second transmission line assembly. The first transmission line assembly is configured to shift the phase of the first amplified signal by a first phase angle, and the second transmission line assembly is configured to shift the phase of the second amplified signal by a second phase angle different from the first phase angle. The first amplifier may be arranged along a carrier signal path, the second amplifier may be arranged along a peak signal path, and the carrier and peak signal paths may be in a Doherty amplifier configuration.

[0099] The power amplifier module may include a phase regulator configured to shift the first signal input to the first amplifier by a third phase angle, and the sum of the first phase angle and the third phase angle is substantially equal to the second phase angle. The first phase angle may be in a first range between 0° and 90°, and the second phase angle may be in a second range between 90° and 180°. The power amplifier module may include a combiner coupled to the outputs of the first transmission line assembly and the second transmission line assembly. The first transmission line assembly may be coupled between the first amplifier and the combiner, and the second transmission line assembly may be coupled between the second amplifier and the combiner.

[0100] The electromagnetic shield may include at least one vertical barrier. The at least one vertical barrier includes one or more dielectric layers interleaved between a plurality of metal layers. The plurality of metal layers may be electrically connected to at least one of the first transmission line assembly and the second transmission line assembly, and at least one of the plurality of metal layers may include or be connected to a ground layer. A plurality of conductive vias may extend through the one or more dielectric layers to connect a first metal layer of the metal layers to a second metal layer of the metal layers. The first metal layer of the metal layers may be connected to the first transmission line assembly, and the second metal layer of the metal layers may be connected to the second transmission line assembly.

[0101] The second transmission line assembly may include first and second transmission lines. The first metal layer in the metal layer may be connected to the first transmission line, and the second metal layer in the metal layer may be connected to the second transmission line. The electromagnetic shield may include a patterned horizontal portion that covers an area including at least one of the first transmission line assembly and the second transmission line assembly. The patterned horizontal portion may correspond to one of the metal layers in the at least one vertical barrier.

[0102] No element, for which a benefit, advantage, solution to a problem, or any element that causes any benefit, advantage, or solution to occur or become more apparent, should be construed as a critical, required, or essential feature or element of any or all of the claims. The present invention is defined solely by the appended claims, including any amendments made during the pendency of this application and all equivalents of the issued claims.

[0103] Although various exemplary embodiments have been described in detail with particular reference to certain exemplary aspects of the present invention, it should be understood that the present invention is capable of having other example embodiments and that details can be modified in various obvious aspects. It will be apparent to those skilled in the art that changes and modifications can be made without departing from the spirit and scope of the present invention. Accordingly, the foregoing disclosure, description, and drawings are for illustrative purposes only and do not limit the present invention in any way, which is defined solely by the claims.

Claims

1. A power amplifier module, characterized in that, comprising: a first phase shifter configured to shift a first amplified signal by a first phase angle, wherein the first phase shifter includes a first transmission line assembly; a second phase shifter configured to shift a second amplified signal by a second phase angle different from the first phase angle, wherein the second phase shifter includes a second transmission line assembly; and an electromagnetic shield between the first phase shifter and the second phase shifter, wherein the electromagnetic shield is arranged to protect the first transmission line assembly from interference by the second transmission line assembly, wherein the electromagnetic shield includes at least one vertical barrier, the at least one vertical barrier including one or more dielectric layers interleaved between a plurality of metal layers, the plurality of metal layers being electrically connected to at least one of the first transmission line assembly and the second transmission line assembly, and at least one of the plurality of metal layers including or being connected to a ground layer.

2. The power amplifier module according to claim 1, characterized in that, further comprising: a plurality of conductive vias extending through the one or more dielectric layers to connect a first metal layer among the metal layers to a second metal layer among the metal layers.

3. The power amplifier module according to claim 2, characterized in that, the first metal layer among the metal layers is connected to the first transmission line assembly, and the second metal layer among the metal layers is connected to the second transmission line assembly.

4. The power amplifier module according to claim 2, characterized in that: the second transmission line assembly includes first and second transmission lines, the first metal layer among the metal layers is connected to the first transmission line, and the second metal layer among the metal layers is connected to the second transmission line.

5. The power amplifier module according to claim 1, characterized in that, the electromagnetic shield includes a patterned horizontal portion covering an area including at least one of the first transmission line assembly and the second transmission line assembly.

6. The power amplifier module according to claim 5, characterized in that, the patterned horizontal portion corresponds to one of the metal layers of the at least one vertical barrier.

7. The power amplifier module according to claim 1, characterized in that, the second transmission line assembly includes: a first transmission line that shifts the second amplified signal by a third phase angle, and a second transmission line that shifts the second amplified signal by a fourth phase angle, wherein the sum of the third phase angle and the fourth phase angle is equal to the second phase angle.

8. The power amplifier module according to claim 7, characterized in that, the vertical barrier is arranged to protect the first transmission line from interference by the second transmission line.

9. A power amplifier module, characterized in that, comprising: a first amplifier configured to amplify a first signal; a first transmission line assembly coupled to the output of the first amplifier; A second amplifier configured to amplify a second signal; A second transmission line assembly coupled to an output of the second amplifier; And An electromagnetic shield between the first transmission line assembly and the second transmission line assembly, wherein the first transmission line assembly is configured to shift a phase of a first amplified signal by a first phase angle and the second transmission line assembly is configured to shift a phase of a second amplified signal by a second phase angle different from the first phase angle, wherein the electromagnetic shield includes at least one vertical barrier including one or more dielectric layers interleaved between a plurality of metal layers, the plurality of metal layers being electrically connected to at least one of the first transmission line assembly and the second transmission line assembly, and at least one of the plurality of metal layers including or being connected to a ground layer.

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