US-12620948-B2 - RF amplifier circuit arrangement and electronic device

Abstract

The present invention relates to a RF amplifier circuit arrangement for amplifying at least one RF input signal to an output signal for delivery to a load. The RF amplifier circuit arrangement uses a simple and low-cost RF clipping circuit within a load modulated balanced amplifier arrangement which passes RF input signals to output linearly up to the signal input reaches a predefined amplitude. Beyond that predefined amplitude the clipping circuit clips excess amplitudes. The present invention further relates to an electronic device.

Inventors

• Paul Lloyd

Assignees

• ROHDE & SCHWARZ GMBH & CO. KG

Dates

Publication Date

20260505

Application Date

20230414

Claims (20)

1. 1 . A RF amplifier circuit arrangement for amplifying at least one radio frequency (RF) input signal, the RF amplifier circuit arrangement comprising: an RF signal splitting circuit configured to split a RF input signal into a first RF input signal and a second RF input signal; an RF signal clipping circuit configured and arranged such to receive the first RF input signal and to produce a clipped RF input signal thereof; a load modulated balanced amplifier (LMBA) coupled to the RF signal splitting circuit and the RF signal clipping circuit, the LMBA comprising a first quadrature hybrid coupler at an input side of the LMBA wherein the first quadrature hybrid coupler is arranged such to receive the clipped RF input signal and the second RF input signal.
2. 2 . The RF amplifier circuit arrangement of claim 1 , wherein the RF signal splitting circuit is a passive RF signal splitting circuit configured to split the RF input signal into two identical first and second RF input signals.
3. 3 . The RF amplifier circuit arrangement of claim 1 , wherein the RF signal splitting circuit is a symmetrical power divider.
4. 4 . The RF amplifier circuit arrangement of claim 1 , wherein the RF signal splitting circuit comprises a symmetrical Wilkinson power divider and in particular a 3-way Wilkinson splitter.
5. 5 . The RF amplifier circuit arrangement of claim 1 , wherein the RF signal clipping circuit comprises a diode limiter circuit comprising at least one diode.
6. 6 . The RF amplifier circuit arrangement of claim 5 , wherein the diode limiter circuit comprises at least two diodes which are connected antiparallel to each other.
7. 7 . The RF amplifier circuit arrangement of claim 1 , wherein the RF signal clipping circuit is configured such to set a predefined clipping level.
8. 8 . The RF amplifier circuit arrangement of claim 1 , wherein the LMBA is an orthogonal load modulated balanced amplifier (OLMBA).
9. 9 . The RF amplifier circuit arrangement of claim 1 , wherein the first quadrature hybrid coupler comprises a first input port and a reverse input port and wherein the first quadrature hybrid coupler is arranged such to receive the clipped RF input signal at its reverse input port.
10. 10 . The RF amplifier circuit arrangement of claim 1 , wherein the LMBA further comprises a second quadrature hybrid coupler at an output side of the LMBA and wherein the LMBA further comprises a main amplifier and an auxiliary amplifier that are arranged between the first and second quadrature hybrid coupler.
11. 11 . The RF amplifier circuit arrangement of claim 1 , wherein the LMBA further comprises a negative resistance amplifier circuit being coupled to a third port of the second quadrature hybrid coupler and having a reflection coefficient greater than or equal to 1.
12. 12 . The RF amplifier circuit arrangement of claim 11 , wherein at least one of the auxiliary amplifiers of the LMBA and the negative resistance amplifier circuit being selectively operable to operate in combination with the main amplifier of the LMBA.
13. 13 . The RF amplifier circuit arrangement of claim 11 , wherein the negative resistance amplifier comprises a control terminal for receiving a control signal and wherein the negative resistance amplifier is configured such to set a predetermined magnitude of the reflection coefficient depending on the received control signal.
14. 14 . The RF amplifier circuit arrangement of claim 11 , wherein the gain of the negative resistance amplifier is below 3 dB and in particular in the range of 1 dB or below.
15. 15 . The RF amplifier circuit arrangement of claim 1 , wherein the negative resistance amplifier circuit comprises at least one of: at least one RF reflection amplifier; at least one IMPATT diode; at least one circulators.
16. 16 . The RF amplifier circuit arrangement of claim 1 , further comprising a sharpening filter coupled between the negative resistance amplifier and the third port of the second quadrature hybrid coupler.
17. 17 . The RF amplifier circuit arrangement of claim 1 , further comprising one single RF input terminal for receiving the RF input signal and an RF output terminal connected to a fourth port of the second quadrature hybrid coupler for providing an RF output signal and for coupling the amplifier circuit arrangement to a load.
18. 18 . The amplifier circuit arrangement of claim 1 , further comprising at least one matching network, wherein each matching network is coupled to a respective one of the four ports of the first or second quadrature hybrid couplers in order to perform impedance transformation, wherein at least one of the matching networks comprises a transmission line or a lumped element.
19. 19 . An electronic device comprising a RF amplifier circuit arrangement for amplifying at least one radio frequency (RF) input signal, the RF amplifier circuit arrangement comprising: an RF signal splitting circuit configured to split a RF input signal into a first RF input signal and a second RF input signal; an RF signal clipping circuit configured and arranged such to receive the first RF input signal and to produce a clipped RF input signal thereof; a LMBA coupled to the signal splitting device and the amplitude limiting device, the LMBA comprising a first quadrature hybrid coupler at an input side of the LMBA wherein the first quadrature hybrid coupler is arranged such to receive directly the clipped input signal and the second input signal.
20. 20 . The electronic device of claim 19 , wherein the electronic device comprises at least on one of: a radio transmitter, a TV transmitter, a radio base station, a bargaining chip.

Description

CROSS-REFERENCE TO RELATED APPLICATION This application claims the benefit of U.S. provisional application No. 63/341,016, filed on May 12, 2022, the content of which is hereby incorporated by reference in its entirety. TECHNICAL FIELD The present invention relates to a RF amplifier circuit arrangement for amplifying at least one RF input signal to an output signal for delivery to a load. The present invention further relates to an electronic device. BACKGROUND OF THE INVENTION RF amplifiers are utilized for a variety of applications, such as in wireless communications systems. As a result, the RF amplifiers must be able to handle the power requirements associated with such wireless communications systems. A RF power amplifier is a unit that strengthens the RF signal to combat losses in transmission by converting DC electric power to the added RF output power. With the rapid development of wireless communications, the design and development of high-efficiency power amplifier design has become one of the most prevalent topics, in particular due to the fact that the RF power amplifier consumes a high portion of the transmitter energy and thus its power efficiency directly impacts the performance of the wireless communications system. In addition, as a power amplifier is the main source of distortion generated by the transmitter, linearity is another concern in the design of power amplifiers, particularly in wideband systems. Modulated signals with high peak to average power ratio (PAPR) are commonly used in modern wireless communications systems to improve spectral efficiency, creating a strong demand for power amplifiers to have high efficiency performance not only at peak power. Many power amplifier architectures have been introduced that are configured to envelope the tracking and outphasing. Among them, the commonly known Doherty power amplifier has become one of the most widely used power amplifier architecture in cellular communication systems, particularly in high power base-stations. However, with further increase of bandwidth, Doherty power amplifier design becomes difficult. Another modern RF amplifier architecture is the so-called load modulated balanced amplifier—or shortly LMBA, which was initially described in US 2005 0134377 A1. In the LMBA architecture described in US 2005 0134377 A1, the RF input signal is equally split via a quadrature splitter between a first and a second amplifier. The outputs of the two amplifiers are then connected to the two input ports of a quadrature coupler. An additional auxiliary drive signal, amplified by an auxiliary amplifier, is injected to an auxiliary or isolated port of the coupler. The load is connected to an output port of the quadrature coupler. Due to the functional property of the quadrature splitter, there is a 90° phase difference between the signal input to the first and second amplifiers. The quadrature coupler behaves in exactly the same manner as the splitter, which also introduces a 90° phase difference between the input signals. Therefore, the signals from the two primary amplifiers arrive at the load with the same phase and add constructively, while the signals arrive at the auxiliary or silent port with 180° out of phase and thus add destructively LMBAs show a similar behavior than Doherty amplifiers, but LMBAs have a wider bandwidth which makes them suitable for a wider range of applications. However, a LMBA has several more or less independent parameters wherein each of these parameters needs to be optimized to achieve maximum performance. One of these parameters is the phase shift and there is the need to provide an exact phase shift for the signals provided to the amplifiers in order to guarantee a proper operation of the LMBA. Present solutions employ multiple baseband inputs or digitally controlled precision level inputs where both of these solutions are comparatively complex and thus expensive. Against this background, there is the need to provide an easier and in particular cheaper RF amplifier arrangement. SUMMARY OF THE INVENTION The present invention provides an RF amplifier circuit arrangement and an electronic device having the features of the independent claims. According to a first aspect, a RF amplifier circuit arrangement for amplifying at least one radio frequency (RF) input signal is provided, wherein the RF amplifier circuit arrangement comprising: an RF signal splitting circuit configured to split a RF input signal into a first RF input signal and a second RF input signal; an RF signal clipping circuit configured and arranged such to receive the first RF input signal and to produce a clipped RF input signal thereof; and a load modulated amplifier coupled to the signal splitting device and the amplitude limiting device, the load modulated amplifier comprising a first quadrature hybrid coupler at an input side of the load modulated amplifier wherein the first quadrature hybrid coupler is arranged such to receive directly the