A multi-stage ultrawideband power amplifier

Abstract

This invention discloses a multi-stage ultra-wideband power amplifier, comprising: a first directional coupler and a second directional coupler disposed between the output matching of a pre-stage power amplifier and the input matching of a post-stage power amplifier; the output terminal of the output matching is connected to the input terminal of the first directional coupler, the through terminal of the first directional coupler outputs a 0° through signal, and the coupled terminal of the first directional coupler outputs a coupled signal that differs from the through terminal by a certain angle; the through terminal and the coupled terminal of the second directional coupler are respectively connected to one of the two input terminals of the second directional coupler, and the output terminal of the second directional coupler is connected to the input terminal of the input matching. This invention solves the problem of mutual interference between the pre- and post-stage matching in multi-stage broadband links, and reduces the difficulty of inter-stage matching in broadband matching design.

Description

Technical Field

[0001] This invention relates to the field of power amplifier technology, and in particular to a multi-stage ultra-wideband power amplifier. Background Technology

[0002] To facilitate large-scale interconnection between people, people and things, and things themselves, the need to develop high-efficiency radio frequency (RF) front-end transmission systems supporting multiple standards has become increasingly urgent. RF power amplifiers are key components of the RF link, determining its power, efficiency, and other core performance indicators. To cover multiple cellular frequency bands in mobile communication networks and to save costs, ultra-wideband (UWB) power amplifiers with octave bands are needed. Beyond mobile communication systems, UWB power amplifiers are also crucial components in electronic warfare and radar systems. UWB radar systems can better track and locate stealth targets, enabling more precise strikes.

[0003] Ultra-wideband RF power amplifiers require broadband matching design to achieve optimal impedance matching between the input and output of the power transistors, thus balancing overall performance across the wide bandwidth. The input and output impedances of the power transistors are functions of frequency, while the matching circuit is fixed and does not change with frequency, which presents a challenge for broadband matching. This is especially true between two amplifier stages, where the output impedance of the preceding stage and the input impedance of the following stage both change with frequency and influence each other, making inter-stage matching particularly difficult in broadband matching design. (See also...) Figure 1 The diagram shown is a schematic of direct matching of a multi-stage RF power amplifier.

[0004] Traditionally, isolators are added between stages to prevent interference between the matching impedances of successive stages, thereby improving the interstage matching of multi-stage amplifiers. However, a drawback is that the larger the operating bandwidth of the isolator, the greater the insertion loss, making it unsuitable for use in ultra-wideband links. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and propose a multi-stage ultra-wideband power amplifier that combines two directional couplers. By utilizing their excellent broadband performance, the output impedance of the preceding stage and the input impedance of the following stage are isolated to prevent mutual interference. This improves the inter-stage matching of the ultra-wideband power amplifier and avoids the problem that isolators used in traditional methods have higher insertion loss as the bandwidth increases, making them unusable in ultra-wideband links.

[0006] The technical solution adopted by this invention to solve its technical problem is:

[0007] A multi-stage ultra-wideband power amplifier includes: a first directional coupler and a second directional coupler disposed between a pre-stage power amplifier and a post-stage power amplifier; the output terminal of the pre-stage power amplifier is connected to the input terminal of the first directional coupler, the through terminal of the first directional coupler outputs a 0° through signal, and the coupling terminal of the first directional coupler outputs a coupling signal that is at a certain angle to the through terminal; the through terminal of the first directional coupler is connected to one input terminal of the second directional coupler, the coupling terminal of the first directional coupler is connected to the other input terminal of the second directional coupler, and the output terminal of the second directional coupler is connected to the input terminal of the post-stage power amplifier.

[0008] Preferably, the first directional coupler splits the output signal of the preamplifier; the second directional coupler combines the split signals from the through end and the coupling end of the first directional coupler for output.

[0009] Preferably, the through end and the coupling end of the first directional coupler have a 90° phase difference; the two input ends of the second directional coupler have a 90° phase difference.

[0010] Preferably, both the first directional coupler and the second directional coupler are 3dB couplers.

[0011] Preferably, the first directional coupler and the second directional coupler further include an isolation terminal; the isolation terminal is matched with a load.

[0012] Preferably, both the first directional coupler and the second directional coupler include four ports; the first port of the first directional coupler is an input terminal, the second port of the first directional coupler is an isolation terminal, the third port of the first directional coupler is a coupling terminal, and the fourth port of the first directional coupler is a through terminal; the first port of the second directional coupler is a first input terminal, the second port of the second directional coupler is a second input terminal, the third port of the second directional coupler is an isolation terminal, and the fourth port of the second directional coupler is an output terminal; wherein, the fourth port of the first directional coupler is connected to the second port of the second directional coupler, and the third port of the first directional coupler is connected to the first port of the second directional coupler.

[0013] Preferably, both the first directional coupler and the second directional coupler include four ports; the first port of the first directional coupler is an input terminal, the second port of the first directional coupler is an isolation terminal, the third port of the first directional coupler is a coupling terminal, and the fourth port of the first directional coupler is a through terminal; the first port of the second directional coupler is a first input terminal, the second port of the second directional coupler is a second input terminal, the third port of the second directional coupler is an output terminal, and the fourth port of the second directional coupler is an isolation terminal; wherein, the fourth port of the first directional coupler is connected to the first port of the second directional coupler, and the third port of the first directional coupler is connected to the second port of the second directional coupler.

[0014] Preferably, both the first directional coupler and the second directional coupler include four ports; the first port of the first directional coupler is an isolation terminal, the second port of the first directional coupler is an input terminal, the third port of the first directional coupler is a through terminal, and the fourth port of the first directional coupler is a coupling terminal; the first port of the second directional coupler is a first input terminal, the second port of the second directional coupler is a second input terminal, the third port of the second directional coupler is an output terminal, and the fourth port of the second directional coupler is an isolation terminal; wherein, the fourth port of the first directional coupler is connected to the second port of the second directional coupler, and the third port of the first directional coupler is connected to the first port of the second directional coupler.

[0015] Preferably, both the first directional coupler and the second directional coupler include four ports; the first port of the first directional coupler is an isolation terminal, the second port of the first directional coupler is an input terminal, the third port of the first directional coupler is a through terminal, and the fourth port of the first directional coupler is a coupling terminal; the first port of the second directional coupler is a first input terminal, the second port of the second directional coupler is a second input terminal, the third port of the second directional coupler is an isolation terminal, and the fourth port of the second directional coupler is an output terminal; wherein, the fourth port of the first directional coupler is connected to the first port of the second directional coupler, and the third port of the first directional coupler is connected to the second port of the second directional coupler.

[0016] Preferably, the ultra-wideband power amplifier includes multiple stages; each pre-stage power amplifier and the connected post-stage power amplifier are provided with the first directional coupler and the second directional coupler.

[0017] Preferably, the first directional coupler and the second directional coupler are positioned between the output matching of the preamplifier and the input matching of the power amplifier.

[0018] The present invention has the following beneficial effects:

[0019] This invention discloses a multi-stage ultra-wideband power amplifier. A first directional coupler and a second directional coupler are placed between the output matching of the pre-stage power amplifier and the input matching of the post-stage power amplifier. One coupler performs power splitting, while the other performs power combining. The combined use of the two directional couplers avoids phase differences in the signals output by the directional couplers. Regardless of changes in the matching circuits of the pre-stage and post-stage power amplifiers, the load impedance of the pre-stage and the source impedance of the post-stage do not interfere with each other. This improves the inter-stage matching of the ultra-wideband power amplifier and avoids the problem of isolators used in traditional methods, where the insertion loss increases with increasing bandwidth, making them unusable in ultra-wideband links.

[0020] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments, but the multi-stage ultra-wideband power amplifier of the present invention is not limited to the embodiments. Attached Figure Description

[0021] Figure 1 A schematic diagram of direct matching for a multi-stage RF power amplifier;

[0022] Figure 2 This is a schematic diagram of the structure of the multi-stage ultra-wideband power amplifier according to Embodiment 1 of the present invention;

[0023] Figure 3 The graph shows the trajectory of the input impedance (circle) and output impedance (triangle) as a function of frequency in Embodiment 1 of the present invention.

[0024] Figure 4 This is a circuit diagram of the multi-stage ultra-wideband power amplifier of Embodiment 1 of the present invention and an existing directly matched multi-stage radio frequency power amplifier;

[0025] Figure 5 This is a schematic diagram comparing the matching gain effect of the multi-stage ultra-wideband power amplifier in this embodiment with the existing direct matching gain effect.

[0026] Figure 6 This is a schematic diagram of the structure of the multi-stage ultra-wideband power amplifier according to Embodiment 2 of the present invention;

[0027] Figure 7 This is a schematic diagram of the structure of the multi-stage ultra-wideband power amplifier in Embodiment 3 of the present invention;

[0028] Figure 8 This is a schematic diagram of the structure of a multi-stage ultra-wideband power amplifier according to Embodiment 4 of the present invention. Detailed Implementation

[0029] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0030] In the description of this invention, it should be noted that the terms "comprising," "including," or any other variations thereof are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0031] In the description of this invention, it should be noted that the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0032] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installed", "equipped", "sleeved / connected", "connected", etc., should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be a connection within two components. For those skilled in the art, the specific meaning of the above terms in this invention can be understood according to the specific circumstances.

[0033] In the description of this invention, it should be noted that the term "multi-level" includes two or more levels.

[0034] Example 1

[0035] See Figure 2As shown in the figure, this embodiment discloses a multi-stage ultra-wideband power amplifier, including multiple cascaded power amplifiers PA1, PA2, ... and PAn. Each power amplifier includes an input match and an output match, and a two-phase directional coupler is provided between the output match of the preceding power amplifier and the input match of the following power amplifier. In this embodiment, taking PA1 and PA2 as examples, PA1 includes an input match 11 and an output match 12, and PA2 includes an input match 21 and an output match 22. Between output match 12 and input match 21, a first directional coupler HC1 and a second directional coupler HC2 are provided. The output terminal of output match 12 is connected to the input terminal of the first directional coupler HC1. After the power is divided equally, the through terminal of the first directional coupler HC1 outputs a 0° through signal, and the coupling terminal of the first directional coupler HC1 outputs a coupling signal that is at a certain angle from the through terminal. The through terminal of the second directional coupler HC2 is connected to one input terminal of the second directional coupler HC2, and the coupling terminal of the second directional coupler HC2 is connected to the other input terminal of the second directional coupler HC2. After the power is combined, the output terminal of the second directional coupler HC2 is connected to the input terminal of input match 21.

[0036] In this embodiment, the first directional coupler HC1 is a splitter; the second directional coupler HC2 is a combiner. Both the first directional coupler HC1 and the second directional coupler HC2 are 3dB 90° bridges, and the corresponding angle is 90°.

[0037] Figure 1 In this configuration, both the first directional coupler HC1 and the second directional coupler HC2 have four ports. The first port a1 of the first directional coupler HC1 is an input terminal, the second port a2 is an isolation terminal, the third port a3 is a coupling terminal, and the fourth port a4 is a through terminal. The first port b1 of the second directional coupler HC2 is a first input terminal, the second port b2 is a second input terminal, the third port b3 is an isolation terminal, and the fourth port b4 is an output terminal. The fourth port a4 of the first directional coupler HC1 is connected to the second port b2 of the second directional coupler HC2, and the third port a3 of the first directional coupler HC1 is connected to the first port b1 of the second directional coupler HC2. The first port b1 of the second directional coupler HC2 is a through terminal, and the second port b2 of the second directional coupler HC2 is a coupling terminal.

[0038] The connection between the first directional coupler HC1 and the second directional coupler HC2 can use all radio frequency connection methods. Connection methods may include radio frequency microstrip lines, coaxial cables, and waveguides, etc.

[0039] Specifically, the transmission process of the signal output by output matching 12 through the first directional coupler HC1 and the second directional coupler HC2 is as follows.

[0040] After passing through the first directional coupler HC1, the two output phases of a1 are a4 and a3, respectively. a4 and a3 are then connected to the input terminals b2 and b1 of the second directional coupler HC2, and the combined signal is output at b4. That is, the signal from a1 to b4 undergoes a process of separation followed by recombining, as shown below:

[0041] (1) a1→a4→b2→b4;

[0042] (2) a1→a3→b1→b4.

[0043] The phase of point a1 is 0 degrees, branching into two paths a4 and a3, which are then combined at b4 (ignoring the phase length within the bridge). a1→a4(b2) produces a phase of 0 degrees, meaning the phase of node a4(b2) relative to node a1 is 0 degrees. a4(b2)→b4 produces a phase of 90 degrees, meaning the phase of node b4 relative to node a4(b2) is -90 degrees. Therefore, the phase of b4 relative to a1 is -90 degrees. a1→a3(b1) produces a phase of 90 degrees, meaning the phase of node a3(b1) relative to node a1 is -90 degrees. a3(b1)→b4 produces a phase of 0 degrees, meaning the phase of node b4 relative to node a3(b1) is 0 degrees. Therefore, the phase of b4 relative to a1 is -90 degrees. From the above, we can see that in both paths, the phase of b4 relative to a1 is -90 degrees, or in other words, the length of both paths is 90 degrees.

[0044] It should be noted that the type and model of the first directional coupler HC1 and the second directional coupler HC2 can be selected according to the needs, as long as they can meet the requirements of bandwidth including the actual working bandwidth and the two total transmission paths being equal, that is, the two signals having no phase difference at the junction.

[0045] Because the first directional coupler HC1 and the second directional coupler HC2 have ultra-wideband characteristics, the impedances of the four ports of the two directional couplers remain constant across the entire frequency band, thus avoiding direct matching between the output (a1) of PA1 and the input (b4) of PA2. Using the structure of this invention, regardless of how the output and input impedances of the preceding and following power amplifiers change with frequency, each receives the fixed port impedance of the directional coupler, thereby achieving mutual non-interference, i.e., optimized and improved inter-stage isolation and matching.

[0046] The following comparison of the gain effects of existing direct matching and the structural matching of the present invention will be conducted using a specific matching circuit to demonstrate that the load impedance of the front stage and the source impedance of the back stage do not interfere with each other.

[0047] See Figure 3 The image shows a pie chart illustrating the variation of the input impedance (circle) and output impedance (triangle) of a gallium nitride (GaN) device with frequency (0.5 GHz - 4.5 GHz). Figure 3 As can be seen, the input and output impedances vary greatly, making wideband matching between stages quite difficult.

[0048] See Figure 4 The diagram shows a circuit diagram of the multi-stage ultra-wideband power amplifier of Embodiment 1 of the present invention and an existing directly matched multi-stage radio frequency power amplifier.

[0049] In the figure, taking gallium nitride (GaN) devices as an example for each amplifier stage, this embodiment uses a first directional coupler and a second directional coupler for matching, as well as existing direct matching, to cascade two GaN devices and achieve broadband matching across the entire frequency band. In this embodiment, the bandwidth supported by the GaN devices is 0.5GHz-4.5GHz.

[0050] It should be noted that, although Figure 4 The invention uses gallium nitride devices as an example, but it is understood that the ultra-wideband power amplifier of the present invention can also be an LDMOS device, a Si device, etc. Figure 4 The top part is a simulation diagram of an embodiment of the present invention, and the bottom part is a simulation diagram of a prior art comparative example.

[0051] The model is entered into the simulation software, and the matching of the first directional coupler and the second directional coupler in this embodiment and the existing direct matching are performed respectively. The symbols are represented as follows.

[0052] HYB1 is the first directional coupler and HYB2 is the second directional coupler. HYB1 and HYB2 are 90-degree phase-shifted bridges.

[0053] TermG101 and TermG201 are the output impedance models of the preamplifier, and TermG102 and TermG202 are the input impedance models of the power amplifier.

[0054] R1, R2: Load. In this embodiment, R1 and R2 can be set to 50 ohms. Specifically, they can be set according to actual needs, and this embodiment does not impose any restrictions.

[0055] The dashed box contains matching circuits with the same strategy, and both cases have achieved optimal modulation bandwidth.

[0056] See Figure 5 The figure shows the simulation results, where the solid line represents the matched gain result of the dual-bridge scheme in this embodiment, and the dashed line represents the direct matched gain effect. When the gain difference does not exceed 10dB, the gain at each frequency point is more gradual within the bandwidth. Figure 5As can be seen, the dual-bridge scheme in this embodiment has a stable bandwidth range of about 0.5 to 4.5 GHz, while the existing direct matching is about 2.5 to 3 GHz. It is evident that the dual-bridge scheme significantly broadens the operating frequency band of the device.

[0057] It should be noted that, although Figure 2 The diagram only shows that the output matching of the preamplifier PA1 and the input matching of the power amplifier PA2 are connected by a first directional coupler and a second directional coupler. However, it can be understood that for multiple cascaded power amplifiers PA1, PA2, ... and PAn, each power amplifier includes an input matching and an output matching, and the output matching of any preamplifier is connected to the input matching of its power amplifier by two connected first directional couplers and second directional couplers.

[0058] Example 2

[0059] See Figure 6 As shown, the difference between this embodiment and Embodiment 1 is that different ports are used as input, output and isolation terminals for the second directional coupler HC2.

[0060] Specifically, in the first directional coupler HC1, port a1 is the input terminal, port a2 is the isolation terminal, port a3 is the coupling terminal, and port a4 is the through terminal; in the second directional coupler HC2, port b1 is the first input terminal, port b2 is the second input terminal, port b3 is the output terminal, and port b4 is the isolation terminal. Port a4 of the first directional coupler HC1 is connected to port b1 of the second directional coupler HC2, and port a3 of the first directional coupler HC1 is connected to port b2 of the second directional coupler HC2. Port b1 of the second directional coupler HC2 is the coupling terminal, and port b2 of the second directional coupler HC2 is the through terminal.

[0061] The working principle and technical effects of this embodiment are the same as those of Embodiment 1.

[0062] Example 3

[0063] See Figure 7 As shown, the difference between this embodiment and Embodiment 1 is that different ports are used as the input terminal, isolation terminal, through terminal and coupling terminal for the first directional coupler HC1.

[0064] Specifically, in the first directional coupler HC1, port a1 is the isolation terminal, port a2 is the input terminal, port a3 is the through terminal, and port a4 is the coupling terminal; in the second directional coupler HC2, port b1 is the first input terminal, port b2 is the second input terminal, port b3 is the output terminal, and port b4 is the isolation terminal. Port a4 of the first directional coupler HC1 is connected to port b2 of the second directional coupler HC2, and port a3 of the first directional coupler HC1 is connected to port b1 of the second directional coupler HC2. Port b1 of the second directional coupler HC2 is the coupling terminal, and port b2 of the second directional coupler HC2 is the through terminal.

[0065] The working principle and technical effects of this embodiment are the same as those of Embodiment 1.

[0066] Example 4

[0067] See Figure 8 The difference between this embodiment and Embodiment 3 is that different ports are used for the input, output and isolation terminals of the second directional coupler HC2.

[0068] Specifically, in the first directional coupler HC1, port a1 is the isolation terminal, port a2 is the input terminal, port a3 is the pass-through terminal, and port a4 is the coupling terminal; in the second directional coupler HC2, port b1 is the first input terminal, port b2 is the second input terminal, port b3 is the isolation terminal, and port b4 is the output terminal. Port a4 of the first directional coupler HC1 is connected to port b1 of the second directional coupler HC2, and port a3 of the first directional coupler HC1 is connected to port b2 of the second directional coupler HC2. Port b1 of the second directional coupler HC2 is the pass-through terminal, and port b2 of the second directional coupler HC2 is the coupling terminal.

[0069] The working principle and technical effects of this embodiment are the same as those of Embodiment 3.

[0070] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements can be made without departing from the principle of the present invention, and these improvements should also be considered within the scope of protection of the present invention.

Claims

1. A multi-stage ultra-wideband power amplifier, characterized in that, include: A first directional coupler and a second directional coupler are disposed between the preamplifier and the power amplifier to isolate the output impedance of the preamplifier and the input impedance of the power amplifier. The output terminal of the preamplifier is connected to the input terminal of the first directional coupler. The first directional coupler splits the output signal of the preamplifier, and the through terminal of the first directional coupler outputs a 0° through signal, while the coupled terminal of the first directional coupler outputs a coupled signal that is at a certain angle to the through terminal. The through terminal of the first directional coupler is connected to one input terminal of the second directional coupler, and the coupled terminal of the first directional coupler is connected to the other input terminal of the second directional coupler. The second directional coupler combines the split signals from the through terminal and the coupled terminal of the first directional coupler and outputs them. The output terminal of the second directional coupler is connected to the input terminal of the power amplifier.

2. The multi-stage ultra-wideband power amplifier according to claim 1, characterized in that, The first directional coupler has a 90° phase difference between its through-end and coupling end; the second directional coupler has a 90° phase difference between its two input ends.

3. The multi-stage ultra-wideband power amplifier according to claim 1, characterized in that, Both the first directional coupler and the second directional coupler are 3dB couplers.

4. The multi-stage ultra-wideband power amplifier according to claim 1, characterized in that, The first directional coupler and the second directional coupler each include an isolation terminal; the isolation terminal is matched with a load.

5. The multi-stage ultra-wideband power amplifier according to claim 4, characterized in that, Both the first and second directional couplers include four ports; the first port of the first directional coupler is an input terminal, the second port is an isolation terminal, the third port is a coupling terminal, and the fourth port is a through terminal; the first port of the second directional coupler is a first input terminal, the second port is a second input terminal, the third port is an isolation terminal, and the fourth port is an output terminal; wherein, the fourth port of the first directional coupler is connected to the second port of the second directional coupler, and the third port of the first directional coupler is connected to the first port of the second directional coupler.

6. The multi-stage ultra-wideband power amplifier according to claim 4, characterized in that, Both the first and second directional couplers include four ports; the first port of the first directional coupler is an input terminal, the second port is an isolation terminal, the third port is a coupling terminal, and the fourth port is a through terminal; the first port of the second directional coupler is a first input terminal, the second port is a second input terminal, the third port is an output terminal, and the fourth port is an isolation terminal; wherein, the fourth port of the first directional coupler is connected to the first port of the second directional coupler, and the third port of the first directional coupler is connected to the second port of the second directional coupler.

7. The multi-stage ultra-wideband power amplifier according to claim 4, characterized in that, Both the first and second directional couplers include four ports; the first port of the first directional coupler is an isolation terminal, the second port is an input terminal, the third port is a through terminal, and the fourth port is a coupling terminal; the first port of the second directional coupler is a first input terminal, the second port is a second input terminal, the third port is an output terminal, and the fourth port is an isolation terminal; wherein, the fourth port of the first directional coupler is connected to the second port of the second directional coupler, and the third port of the first directional coupler is connected to the first port of the second directional coupler.

8. The multi-stage ultra-wideband power amplifier according to claim 4, characterized in that, Both the first and second directional couplers include four ports; the first port of the first directional coupler is an isolation terminal, the second port is an input terminal, the third port is a through terminal, and the fourth port is a coupling terminal; the first port of the second directional coupler is a first input terminal, the second port is a second input terminal, the third port is an isolation terminal, and the fourth port is an output terminal; wherein, the fourth port of the first directional coupler is connected to the first port of the second directional coupler, and the third port of the first directional coupler is connected to the second port of the second directional coupler.

9. The multi-stage ultra-wideband power amplifier according to claim 1, characterized in that, The ultra-wideband power amplifier comprises multiple stages; each pre-stage power amplifier and its connected post-stage power amplifier are equipped with the first directional coupler and the second directional coupler.

10. The multi-stage ultra-wideband power amplifier according to claim 1 or 9, characterized in that, The first directional coupler and the second directional coupler are positioned between the output match of the preamplifier and the input match of the power amplifier.

Images