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EP-3987657-B1 - POWER AMPLIFIER WITH LARGE OUTPUT POWER

EP3987657B1EP 3987657 B1EP3987657 B1EP 3987657B1EP-3987657-B1

Inventors

  • BAO, MINGQUAN

Dates

Publication Date
20260513
Application Date
20190624

Claims (9)

  1. A power amplifier (700, 1000) comprising: a number n of power cells A i , where i=1, ..n, each power cell has an input terminal (Ain) and an output terminal (Aout); a number n of output transmission lines TL 1i for combining output powers from the power cells, where i=1,...n, wherein each output transmission line has a first terminal (T1) and a second terminal (T2), the second terminal (T2) of the i-th transmission line is connected to the first terminal (T1) of the (i+1)-th transmission line such that the number n of output transmission lines are connected in series; a number n of input transmission lines TL 0i , where i=1, ...n, connected in series, each input transmission line has a first terminal and a second terminal, where the second terminal of the i-th transmission line is connected to the first terminal of the (i+1)-th transmission line, and wherein the input terminal of the i-th power cell is connected to the second terminal of the i-th transmission line via a capacitor, and an input port (Pin) of the whole power amplifier is connected with the first terminal of the first transmission line (TL 01 ); and a number n of impedance transformation network ITN i , where i=1,... n, each impedance transformation network has an input terminal (ITNin) and output terminal (ITNout); wherein the output terminal of i-th power cell is connected to the input terminal of the i-th impedance transformation network and the output terminal of the i-th impedance transformation network is connected to the first terminal of the i-th output transmission line, characterized in that each impedance transformation network is an upward impedance transformation network for transforming an output impedance of each power cell at the input terminal of the impedance transformation network into a higher impedance at the output terminal of the impedance transformation network, and wherein each impedance transformation network is a tapped capacitor impedance transformation network or a tapped inductor impedance transformation network, and a tapped node of the impedance transformation network is the input terminal of the impedance transformation network.
  2. The power amplifier (700, 1000) according to claim 1, wherein each power cell comprise a common-source configured transistor, and wherein a gate of each transistor is connected to the input terminal of the power cell and a drain of each transistor is connected to the output terminal of the power cell, a source of each transistor is connected to a ground.
  3. The power amplifier (700, 100) according to any one of claims 1-2, wherein the tapped capacitor impedance transformation network comprises a first and second capacitors connected in series, where a second terminal of the first capacitor is connected to a first terminal of the second capacitor to form a tapped node, and wherein the input terminal of the impedance transformation network is connected to the tapped node, the output terminal of the impedance transformation network is connected to a first terminal of the first capacitor, a second terminal of the second capacitor is connected to a ground.
  4. The power amplifier (700, 1000) according to claim 3, wherein parasitic capacitance of a transistor in each power cell is a part of the tapped capacitor impedance transformation network.
  5. The power amplifier according to any one of claims 1-2, wherein the tapped inductor impedance transformation network comprises a first and second inductors connected in series, where a second terminal of the first inductor is connected to a first terminal of the second inductor to form a tapped node, and wherein the input terminal of the impedance transformation network is connected to the tapped node, the output terminal of the impedance transformation network is connected to a first terminal of the first inductor, a second terminal of the second inductor is connected to a ground.
  6. The power amplifier according to any one of claims 1-5, wherein the output transmission lines have different widths and lengths.
  7. The power amplifier according to any one of claims 1-5, wherein each of the output transmission lines has the same width and length.
  8. An electronic device comprising a power amplifier according to any one of claims 1-7.
  9. The electronic device according to claim 8 is any one of a transmitter, a transceiver, a base station, a mobile device, a user equipment in a wireless communication system.

Description

TECHNICAL FIELD Embodiments herein relate to a power amplifier. In particular, they relate to a power amplifier with large output power, an electronic device and a transmitter comprising the power amplifier. BACKGROUND Power amplifiers (PA) are widely used for example in radio base stations and user equipments in wireless communication systems, as well as in radar systems. A power amplifier in a transmitter typically amplifies an input signal into an output signal ready for radio transmission. In a micro or millimeter wave transmitter, a PA needs to deliver a large output power for long-distance communication or radar-detection. One approach to boost the output power is combining output powers from several power cells, i.e., transistors, on-chip. The power combiner must add output powers from the power cells constructively, i.e. in-phase, and provide impedance matching for each power cell, as well as outside load impedance. A 2-way Wilkinson power combiners is widely used, which consists of two quarter wavelength (λg/4) transmission lines and one resistor, as shown in Figure 1. A 4-way power combiner can be comprised of three Wilkinson power combiners. To minimize the combiner's footprint, as well as the loss, short micro strip transmission lines (e.g. λg/36) may be used, and the resistor in a Wilkinson power combiner is skipped, such as an 8-way power combiner disclosed in E. Ojefors, et.al., "An 8-Way Power-Combining E-band Amplifier in a SiGe HBT technology", Proceedings of the 9th European Microwave Integrated Circuits Conference, pp. 45-48, 2014. Such a power combiner presents high impedance (e.g. >50Ω) for each power cell. Transformers are often used for combining power as shown in Figure 2. Transformers may be configured to combine the powers in series, as shown in Figure 2(a), or in parallel as shown Figure 2(b). It is also possible to mix a series- and a parallel-combining as shown in Figure 2(c). For the series-combing transformers, the power combiner provides an impedance of Rload/N approximately for each power cell, where, Rload is the impedance of the output port, and N is the number of power cells. While, for the parallel-combining transformers, the corresponding impedance for each power cell is N*Rload. It should be pointed out, for the sick of large output power, the series-combining transformers is superior to the parallel-combining one, because lower impedance for power cells or transistors is desired. Assuming Ropt is the required intrinsic load for the transistor to deliver its peak output power, Ropt is given by Ropt=Vdd−Vk22Ppeak where Vdd is drain voltage bias, vk is transistor's knee voltage. Ppeak denotes peak output power. Equation (1) shows that, the larger Ppeak is, the small is Ropt. The output powers also can be combined in series by utilizing transmission lines. Such kind of amplifier is so-called distributed amplifier (DP) as shown in Figure 3, where the drain parasitic capacitance Cd and the transmission line Ld form an artificial transmission line. The input power is distributed to each transistor through another artificial transmission line, i.e. Lg and Cg sections, at the gate. If the gate and the drain transmission line provide the same phase shifts, the drain currents from multiple transistors are added up constructively at the load Zod. Combining by transmission lines is superior to combining by transformers in term of losses, because the losses associated with the second winding and coupling between two windings are avoided. The distributed amplifier mentioned above has a gain response with a frequency range from DC to a cutoff frequency, i.e. a low pass amplifier. A band-pass distributed amplifier is introduced in N.P. Mehta and P.N. Shastry "Design guidelines for a novel bandpass distributed amplifier", European Microwave Conference (EuMC), pp. 1-4, 2005, and H. Rashtian and O. Momeni, "Gain boosting in distributed amplifiers for close-to-fmax operation in silicon", IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES, Vol. 67, 2019, which is shown in Figure 4, where shunted inductors L2 is added at both gate and drain transmission lines. Capacitor Cb is used for dc-decoupling. However, the uniform distributed amplifier where transmission lines has the same width and length has drawbacks such as: input power for each transistor is unequal, because the transistors in front takes off a portion of power; a portion of output power travels to left and gets dissipated at resistor Zod; transistors are not equally or optimally loaded because the load of the transistor is modulated by the output currents from other transistors. Therefore, nonuniform distributed power amplifier is proposed to deal with those problems, as shown in Figure 5, which is disclosed in C. F. Campbell, "Evolution of the nonuniform distributed power amplifier", IEEE Microwave Magazine, Vol. 20 , No.1, pp. 18-27, 2019. In a nonuniform DP, resistor Zod is removed, and the drain of the transistor at the m