WO2021197922A1

WO2021197922A1 - Tower mounted amplifier

Info

Publication number: WO2021197922A1
Application number: PCT/EP2021/057408
Authority: WO
Inventors: Markku Tiihonen; Yngve Alnes ERIKSEN; Hannu HEISKALA
Original assignee: Kaelus Ab
Priority date: 2020-04-01
Filing date: 2021-03-23
Publication date: 2021-10-07
Also published as: SE2251113A1; CN219227597U

Abstract

In accordance with one or more embodiments herein, a tower mounted amplifier (TMA) (100) arranged for receiving duplexed radio frequency (RF) signals is provided. The TMA (100) comprises: a first port (110), arranged to receive a Tx signal and output an Rx signal; a second port (120), arranged to receive an Rx signal and output a Tx signal; an RF power harvester (150), arranged to generate a DC voltage and/or a DC current from the Tx signal received on the first port (110); and at least one amplifier (130), e.g. low noise amplifier (LNA), arranged to amplify the signal received on the second port (120) on its way to the first port (110).

Description

TOWER MOUNTED AMPLIFIER

TECHNICAL FIELD

The present disclosure relates generally to tower mounted amplifiers (TMA) arranged for receiving duplexed radio frequency (RF) signals.

BACKGROUND

Tower mounted amplifiers are typically mounted in base station towers. The transmitting power from a base station tower is generally very high, in order for RF signals from the base station antenna to be able to reach mobile telephones located far from the base station tower with a high signal quality. However, the RF signals received by the base station antenna generally have rather low power, since the mobile telephones themselves do not have very high transmission power. Furthermore, as the antenna is mounted in top of the base station tower, while the actual base station is normally further down, the cable between the two will introduce loss. The signals received by the base station antenna must therefore be amplified, e.g. using a TMA, in order to overcome this loss.

Time division duplex (TDD) uses a single frequency channel to transmit signals in both the transmitting (Tx) and receiving (Rx) directions by transmitting the signals in different time slots. TDD operates by toggling transmission directions at high speed over a time interval. To support the use of a single frequency channel, TDD normally requires a silent time interval between transmit and receive data streams.

US20190296792 describes a TDD signal booster that amplifies the signals in the two directions in different ways.

US6812786 describes a zero-bypass switching circuit using mismatched 90 degrees hybrid couplers.

US10523260 describes base station antennas having transmitters and receivers therein that support TDD with enhanced bias control for high speed switching.

PROBLEMS WITH THE PRIOR ART

The purpose of a TMA is to amplify signals received by a base station antenna. However, if the amplifier in the TMA is dimensioned for amplifying the RF signals received by the base station antenna (Rx signals), the RF signals transmitted by the base station antenna (Tx signals) may be powerful enough to case malfunction if they reach the amplifier, since the Tx signals are so much more powerful than the Rx signals. When TDD signals are received in a TMA, there is thus a need to prevent the Tx signals from reaching the amplifier.

In US20190296792, there is a control circuit that detects the silent time interval and controls the amplifier circuit to change configuration, in order for the signals in the two directions to be amplified in different ways. However, if the difference in power between the signals in the two directions is very large, such a control may be inadequate to protect the amplifier.

US6812786 describes a zero-bypass switching circuit using mismatched 90 degrees hybrid couplers and biased PIN diodes. In such a solution, it is necessary to ensure that there is a DC voltage and/or a DC current available for biasing the diodes. Further, the arrangement described in US6812786 would not be able to handle a powerful Tx signal without destroying the amplifier components, and therefore uses a duplex filter to separate the Tx signal from the Rx signal. It is not possible to use such duplex filters for TDD signals.

There is thus a need for an improved TMA.

SUMMARY

The above described problem is addressed by the claimed TMA arranged for receiving duplexed RF signals. The TMA may comprise: a first port, arranged to receive a Tx signal and output an Rx signal; a second port, arranged to receive an Rx signal and output a Tx signal; an RF power harvester, arranged to generate a DC voltage and/or a DC current from the signal received on the first port; and at least one amplifier, arranged to amplify the signal received on the second port before it is outputted on the first port. The second port is preferably connected to a base station antenna.

In embodiments, the generated DC voltage and/or DC current is used for feeding components within the TMA, preferably components that are used for preventing RF signals received on the first port from reaching the at least one amplifier. Such components may e.g. be diodes, that may e.g. be biased using a negative voltage generated by the RF power harvester.

In embodiments, the TMA comprises functionality for detecting power received on the first port., e.g. using the RF power harvester. In embodiments, the TMA comprises short-circuit points that are arranged to, when power is detected on the first port, short-circuit any RF signal that does not flow to the second port, so that it is reflected instead of reaching the at least one amplifier. The short-circuit points may e.g. be arranged to short-circuit any RF signal that does not flow through a switching arrangement in the TMA.

In embodiments, the short-circuit points are short-circuited using PIN diodes, and the generated DC voltage and/or DC current is used for biasing said PIN diodes.

In embodiments, the TMA comprises a switching arrangement. The switching arrangement may be arranged to, when power is detected on the first port, prevent the signal received on the first port from reaching the at least one amplifier.

In embodiments, the switching arrangement is arranged to: when power is detected on the first port, be set to allow the signal received on the first port to flow through the switching arrangement directly to the second port, without passing the at least one amplifier; and when no power is detected on the first port, be set to prevent the signal received on the second port from flowing through the switching arrangement on its way to the first port, so that the signal received on the second port is instead fed to the at least one amplifier, allowing the at least one amplifier to amplify the signal received on the second port before outputting it on the first port. The second port is preferably connected to a base station antenna.

In embodiments, the TMA comprises at least one circulator that is arranged to prevent any signal received on the first port from reaching the at least one amplifier. If any part of the Tx signal received on the first port would not flow through the switching arrangement, e.g. due to leakage through the isolation port of a hybrid coupler, the circulator will ensure that the Tx signal anyhow cannot reach the at least one amplifier.

In embodiments, the switching arrangement comprises a combination of hybrid couplers, and/or circulators, and one or more PIN diodes, and the generated DC voltage and/or DC current is used for biasing the one or more PIN diodes in the switching arrangement. The one or more PIN diodes may e.g. be biased for short- circuiting various short-circuit points in the switching arrangement.

The above described problem is further addressed by the claimed method for generating a DC voltage and/or a DC current in a TMA arranged for receiving duplexed RF signals. The method may comprise: receiving a Tx signal on a first port; generating a DC voltage and/or a DC current from the signal received on the first port, e.g. using an RF power harvester; receiving an Rx signal on a second port; amplifying the signal received on the second port; and outputting said amplified signal on the first port. The second port is preferably connected to a base station antenna. In embodiments, the method comprises using the generated DC voltage and/or DC current for feeding components within the TMA, preferably components that are used for preventing RF signals received on the first port from reaching the at least one amplifier. Such components may e.g. be diodes, that may e.g. be biased using a negative voltage generated by the RF power harvester.

In embodiments, the method comprises detecting power on the first port, e.g. using an RF power harvester.

In embodiments, the method comprises, when power is detected on the first port, short-circuiting any RF signal that does not flow to the second port in short-circuit points, so that the signal is reflected instead of reaching the at least one amplifier. The short-circuit points may e.g. be arranged to short-circuit any RF signal that does not flow through a switching arrangement in the TMA.

In embodiments, the method comprises using the generated DC voltage and/or DC current for biasing PIN diodes used for short-circuiting the short-circuit points.

In embodiments, the method comprises, when power is detected on the first port, using a switching arrangement to prevent as much as possible of the signal received on the first port from reaching the at least one amplifier.

In embodiments, the method comprises: when power is detected on the first port, setting the switching arrangement to allow the signal received on the first port to flow through the switching arrangement directly to the second port, without passing the at least one amplifier; and when no power is detected on the first port, setting the switching arrangement to prevent the signal received on the second port from flowing through the switching arrangement on its way to the first port, so that the signal received on the second port is instead fed to the at least one amplifier, allowing the at least one amplifier to amplify the signal received on the second port before outputting it on the first port.

In embodiments, the method comprises using at least one circulator to prevent any signal received on the first port from reaching the at least one amplifier. If any part of the Tx signal received on the first port would not flow through the switching arrangement, e.g. due to leakage through the isolation port of a hybrid coupler, the circulator will ensure that the Tx signal anyhow cannot reach the at least one amplifier.

In embodiments, the switching arrangement comprises a combination of hybrid couplers, and/or circulators, and one or more PIN diodes, and the method comprises using the generated DC voltage and/or DC current for biasing the one or more PIN diodes in the switching arrangement. The one or more PIN diodes may e.g. be biased for short-circuiting various short-circuit points in the switching arrangement.

In embodiments, the TMA is a time division multiplex TMA (TDD-TMA). The scope of the invention is defined by the claims, which are incorporated into this section by reference. A more complete understanding of embodiments of the invention will be afforded to those skilled in the art, as well as a realization of additional advantages thereof, by a consideration of the following detailed description of one or more embodiments. Reference will be made to the appended sheets of drawings that will first be described briefly.

BRIEF DESCRIPTION OF THE DRAWINGS

Figures 1-7 schematically illustrate various embodiments of a TMA arranged for receiving duplexed RF signals, in accordance with one or more embodiments described herein.

Figure 8 schematically illustrates an embodiment of a RF power harvester, in accordance with one or more embodiments described herein.

Figure 9 schematically illustrates a method 900 for generating a DC voltage and/or a DC current in a TMA 100 arranged for receiving duplexed RF signals, in accordance with one or more embodiments described herein.

Embodiments of the present disclosure and their advantages are best understood by referring to the detailed description that follows. It should be appreciated that like reference numerals are used to identify like elements illustrated in one or more of the figures.

DETAILED DESCRIPTION

The present disclosure relates generally to tower mounted amplifiers (TMA) arranged for receiving duplexed radio frequency (RF) signals. Embodiments of the disclosed solution are presented in more detail in connection with the figures.

Figures 1-7 schematically illustrate various embodiments of a TMA 100 arranged for receiving duplexed RF signals, in accordance with one or more embodiments described herein. The various TMA 100 embodiments schematically illustrated in figures 1-7 each comprise a first port 110 and a second port 120. The second port 120 is preferably connected to a base station antenna, which is arranged to transmit a Tx signal and receive an Rx signal. The TMA also comprises at least one amplifier 130, e.g. an LNA, that is arranged to amplify the Rx signal received from the antenna on the second port 120 on its way to the first port 110, where it is outputted.

Since the at least one amplifier 130 is preferably dimensioned for amplifying the Rx signals, the Tx signals may be powerful enough to case malfunction if they reach the at least one amplifier 130, since the Tx signal is so much more powerful than the Rx signal. There is thus a need to prevent the Tx signals from reaching the at least one amplifier 130.

The various TMA 100 embodiments schematically illustrated in figures 1-7 each comprises an RF power harvester 150, that is arranged to generate a DC voltage and/or a DC current from the Tx signal received on the first port 110. The generated DC voltage and/or DC current may e.g. be used for feeding components within the TMA 100, such as e.g. various components that are used for preventing the Tx signals received on the first port 110 from reaching the at least one amplifier 130. The RF power harvester 150 may e.g. generate a negative DC voltage that may be used for biasing diodes in the TMA 100. The diodes in the TMA 100 may in this case be biased also when no external DC voltage is available, which means that the intermodulation will be much better than if the diodes are "floating”.

The RF power harvester 150 may be used also for detecting power received on the first port 110, since DC voltage and/or DC current can only be generated when there is power on the first port 110. Since power detected on the first port 110 means that a Tx signal is being received in the TMA 100, this can be used for controlling the TMA 100 to transfer the Tx signals to the second port 120, where they can be transmitted to the antenna, while at the same time preventing the Tx signals from reaching the at least one amplifier 130. This control is preferably effected by controlling components within the TMA 100, such as e.g. by forward or reverse biasing diodes in the TMA 100.

The various TMA 100 embodiments schematically illustrated in figures 1-6 each comprises short-circuit points 160 that may be used to short-circuit any RF signal that does not flow to the second port 120, so that it is reflected instead of reaching the at least one amplifier 130. In order to ensure that no Tx signal reaches the at least one amplifier 130, the short-circuit points 160 may be controlled to short-circuit when power is detected on the first port 110. In the TMA 100 embodiments schematically illustrated in figures 1-3 and 5, the short-circuit points 160 are short-circuited by forward biasing PIN diodes 165, and the generated DC voltage and/or DC current is used for forward biasing said PIN diodes 165.

The various TMA 100 embodiments schematically illustrated in figures 1-7 each comprises a switching arrangement 140 that may be used to prevent the Tx signal received on the first port 110 from reaching the at least one amplifier 130. In order to ensure that no Tx signal reaches the at least one amplifier 130, the switching arrangement 140 may be controlled to prevent the Tx signal received on the first port 110 from reaching the at least one amplifier 130 when power is detected on the first port 110.

In the TMA 100 embodiments schematically illustrated in figures 1, 2 and 7, the switching arrangement 140 comprises a combination of hybrid couplers 181, 182 and PIN diodes 195. The PIN diodes 195 in the switching arrangement 140 may e.g. be biased using the generated DC voltage and/or DC current. Hybrid couplers are four-port devices that split the incident power signal into two output ports. The phase difference between the two output ports of a hybrid coupler may be 0 degrees, 90 degrees, or 180 degrees, depending on the type used. The hybrid couplers 181, 182 are preferably 90 degree hybrid couplers, where the signals at the outputs have a 90 degree phase difference with respect to each other. Reflections due to mismatches are sent to the isolation port, preventing any power from reflecting back to the input port.

The loss in a PIN diode is dependent on the line impedance. By utilizing the possibility to transform the impedance with an impedance transforming hybrid coupler, such as e.g. the impedance transforming hybrid coupler described in US8174338, the loss of the PIN diode can be minimized.

In the TMA 100 schematically illustrated in figure 1, when power is detected on the first port 110, the PIN diodes 195 are reverse biased, so that short-circuit points 190 are not short-circuited, and this allows the Tx signal received on the first port 110 to flow through the switching arrangement 140 to the second port 120 for further transmission to the antenna, without passing the at least one amplifier 130. However, when no power is detected on the first port 110, the PIN diodes 195 are forward biased, thereby short-circuiting the short- circuit points 190, so that the Rx signal is reflected and sent via the isolation port of the hybrid coupler 182 through amplifier 130 instead of being allowed to flow through the hybrid coupler 181. In this way, the Rx signal received from the antenna on the second port 120 is prevented from flowing through the switching arrangement 140 on its way to the first port 110, and is instead fed to the at least one amplifier 130, allowing the at least one amplifier 130 to amplify the Rx signal received on the second port 120 before outputting it on the first port 110.

In the TMA 100 schematically illustrated in figure 2, when power is detected on the first port 110, the PIN diodes 195 are forward biased, so that the Tx signal received on the first port 110 is allowed to flow through the switching arrangement 140 to the second port 120 for further transmission to the antenna, without passing the at least one amplifier 130. However, when no power is detected on the first port 110, the PIN diodes 195 are reverse biased, so that the Rx signal is reflected and sent via the isolation port of the hybrid coupler 182 through amplifier 130 instead of being allowed to flow through the hybrid coupler 181. In this way, the Rx signal received from the antenna on the second port 120 is prevented from flowing through the switching arrangement 140 on its way to the first port 110, and is instead fed to the at least one amplifier 130, allowing the at least one amplifier 130 to amplify the Rx signal received on the second port 120 before outputting it on the first port 110.

In the various TMA 100 embodiments schematically illustrated in figures 3-6, the switching arrangement 140 comprises a combination of circulators 171, 172 and a PIN diode 195. The PIN diode 195 in the switching arrangement 140 may e.g. be biased using the generated DC voltage and/or DC current. In the TMA 100 embodiments schematically illustrated in figures 3 and 4, when power is detected on the first port 110, the PIN diode 195 is forward biased, so that the Tx signal received on the first port 110 is allowed to flow through the switching arrangement 140 to the second port 120 for further transmission to the antenna, without passing the at least one amplifier 130. However, when no power is detected on the first port 110, the PIN diode 195 is reverse biased, so that the Rx signal is reflected and sent via the circulator 172 through amplifier 130 instead of being allowed to flowthrough the circulator 171. In this way, the Rx signal received from the antenna on the second port 120 is prevented from flowing through the switching arrangement 140 on its way to the first port 110, and is instead fed to the at least one amplifier 130, allowing the at least one amplifier 130 to amplify the Rx signal received on the second port 120 before outputting it on the first port 110.

In the TMA 100 embodiments schematically illustrated in figures 5 and 6, when power is detected on the first port 110, the PIN diode 195 is reverse biased, so that short-circuit point 190 is not short-circuited, and this allows the Tx signal received on the first port 110 to flow through the switching arrangement 140 to the second port 120 for further transmission to the antenna, without passing the at least one amplifier 130. However, when no power is detected on the first port 110, the PIN diode 195 is forward biased, thereby short-circuiting the short-circuit point 190, so that the Rx signal is reflected and via the circulator 172 through amplifier 130 instead of being allowed to flowthrough the circulator 171. In this way, the Rx signal received from the antenna on the second port 120 is prevented from flowing through the switching arrangement 140 on its way to the first port 110, and is instead fed to the at least one amplifier 130, allowing the at least one amplifier 130 to amplify the Rx signal received on the second port 120 before outputting it on the first port 110.

In the TMA 100 embodiments schematically illustrated in figures 1-6, the Tx signal received on the first port 110 is allowed to flow through the switching arrangement 140 to the second port 120 for further transmission to the antenna. In these embodiments, the at least one amplifier 130 is arranged outside of the switching arrangement 140.

The TMA 100 embodiments schematically illustrated in figures 1 and 2 further comprises a circulator 170 that is arranged to prevent any Tx signal received on the first port 110 from flowing to the at least one amplifier 130, instead of flowing through the switching arrangement 140. If any part of the Tx signal received on the first port 110 would leak through the isolation port of the hybrid coupler 181 and thus not flow through the switching arrangement 140, the circulator 170 will ensure that it anyhow cannot reach the at least one amplifier 130. The extra protection provided by the circulator 170 is beneficial if the amplifier 130 cannot withstand Tx power even for a short interval, before the diodes 165 short-circuit the short-circuit points 160. However, with an amplifier 130 that can withstand Tx power for a short interval, there is no need for any circulator 170. In the TMA 100 schematically illustrated in figure 7, the switching arrangement 140 comprises a combination of hybrid couplers 181, 182, circulators 170, and PIN diodes 195, and there are two amplifiers 130 arranged within the switching arrangement 140. The PIN diodes 195 in the switching arrangement 140 may e.g. be biased using the generated DC voltage and/or DC current. When power is detected on the first port 110, the PIN diodes 195 are forward biased, thereby short-circuiting the short-circuit points 190, so that the Tx signal is reflected and sent via the isolation port of the first hybrid coupler 181 to the second hybrid coupler 182, and then reflected again and sent via the isolation port of the second hybrid coupler 182 to the second port 120 for further transmission to the antenna. In this way, the Tx signal received on the first port is prevented from reaching the amplifiers 130. However, when no power is detected on the first port 110, the PIN diodes 195 are reverse biased, so that short-circuit points 190 are not short-circuited, and this allows the Rx signal received on the second port 120 to flow through the amplifiers 130 to the first port 110, thereby allowing the amplifiers 130 to amplify the Rx signal received on the second port 120 before outputting it on the first port 110.

In the TMA 100 schematically illustrated in figure 7, the Tx signal received on the first port 110 is thus prevented from flowing through the switching arrangement 140. In this embodiment, the at least one amplifier 130 is arranged inside the switching arrangement 140.

The TMA 100 schematically illustrated in figure 7 further comprises circulators 170 that are arranged to prevent any Tx signal received on the first port 110 from flowing to the amplifiers 130. If any part of the Tx signal received on the first port 110 would leak through the short-circuit points 190, the circulators 170 will ensure that it anyhow cannot reach the at least one amplifier 130.

Figure 8 schematically illustrates an embodiment of a RF power harvester 150, arranged to generate a DC voltage and/or a DC current on output port 810, 820 from the Tx signal. The RF power harvester 150 schematically illustrated in figure 8 essentially works as an envelope detector, which provides an output on output port 810, 820 that is the envelope of the Tx signal. The schematic circuit in figure 8 may be cascaded to obtain higher DC voltage and/or DC current.

The RF power harvester 150 may couple a fraction of the Tx power into a forward coupled line and a fraction into a reversed coupled line, e.g. so that the reverse coupled line provides an output on output port 810 and the forward coupled line provides an output on output port 820, as illustrated in figure 8. A DC voltage and/or a DC current may thus be generated on both outputs 810, 820, but the RF power harvester 150 may also be arranged to generate a DC voltage on one of the outputs 810, 820 and a DC current on another of the outputs 810, 820. Instead of coupling a fraction of the Tx power into a forward coupled line and a reversed coupled line, an RF probe could be used, but there is in that case a risk that the reflected power could cancel out the forward power. In case both a DC voltage and a DC current is needed, the RF power may be splinted, to feed RF power to both a DC voltage converter to a DC current converter.

The RF power harvester 150 may be used also for detecting that a Tx signal is being received in the TMA 100. This can be used for controlling the TMA 100 to transfer the Tx signals to the second port 120, where they can be transmitted to the antenna, while at the same time preventing the Tx signals from reaching the at least one amplifier 130. This control is preferably effected by using the generated DC voltage and/or DC current for controlling components within the TMA 100, such as e.g. by forward or reverse biasing diodes in the TMA 100. The diodes in the TMA 100 may in this case be biased also when no external DC voltage or current is available, which means that the intermodulation will be much better than if the diodes are "floating””. The RF power harvester 150 may e.g. generate a negative DC voltage that may be used for biasing diodes in the TMA 100.

The invention is especially interesting when the TMA is a time division multiplex TMA (TDD-TMA).

Figure 9 schematically illustrates a method 900 for generating a DC voltage and/or a DC current in a TMA 100 arranged for receiving duplexed RF signals, in accordance with one or more embodiments of the invention. The method 900 may comprise:

Step 910: receiving a Tx signal on a first port 110.

Step 920: generating a DC voltage and/or a DC current from the signal received on the first port 110, e.g. using an RF power harvester 150.

Step 940: receiving an Rx signal on a second port 120.

Step 950: amplifying the signal received on the second port 120.

Step 960: outputting said amplified signal on the first port 110.

The method 900 may further comprise at least one of:

Step 925: using the generated DC voltage and/or DC current for feeding components within the TMA 100. Such components may e.g. be diodes, that may e.g. be biased using a negative voltage generated by the RF power harvester.

Step 930: detecting power on the first port 110, e.g. using an RF power harvester 150. Step 970: when power is detected on the first port 110, short-circuiting any RF signal that does not flow to the second port 120 in short-circuit points 160, so that the signal is reflected instead of reaching the at least one amplifier 130.

Step 975: using the generated DC voltage and/or DC current for biasing PIN diodes 165 used for short- circuiting the short-circuit points 160.

Step 980: when power is detected on the first port 110, using a switching arrangement 140 to prevent as much as possible of the signal received on the first port 110 from reaching the at least one amplifier 130.

Step 985: when power is detected on the first port 110, setting the switching arrangement 140 to allow the signal received on the first port 110 to flow through the switching arrangement 140 directly to the second port 120, without passing the at least one amplifier 130, and when no power is detected on the first port 110, setting the switching arrangement 140 to prevent the signal received on the second port 120 from flowing through the switching arrangement 140 on its way to the first port 110) so that the signal received on the second port 120 is instead fed to the at least one amplifier 130, allowing the at least one amplifier 130 to amplify the signal received on the second port 120 before outputting it on the first port 110.

Step 990: using at least one circulator 170 to prevent any signal received on the first port 110 from reaching the at least one amplifier 130. If any part of the Tx signal received on the first port 110 would not flow through the switching arrangement 140, e.g. due to leakage through the isolation port of a hybrid coupler 181, the circulator 170 will ensure that the Tx signal anyhow cannot reach the at least one amplifier 130.

In embodiments, the switching arrangement 140 comprises a combination of hybrid couplers 181, 182, and/or circulators 170, 171, 172, and one or more PIN diodes 195, and the method comprises using the generated DC voltage and/or DC current for biasing the one or more PIN diodes 195 in the switching arrangement 140. The one or more PIN diodes 195 may e.g. be biased for short-circuiting various short- circuit points in the switching arrangement 140.

In embodiments, the TMA 100 is a time division multiplex TMA (TDD-TMA).

The foregoing disclosure is not intended to limit the present invention to the precise forms or particular fields of use disclosed. It is contemplated that various alternate embodiments and/or modifications to the present invention, whether explicitly described or implied herein, are possible in light of the disclosure. The TMA embodiments described herein all comprise a number of different components arranged for preventing the Tx signal from reaching the amplifier, and it is of course not necessary to provide all these different components in the TMA 100. Much simpler TMA embodiments with just some of the described functionalities can be readily arranged by a person skilled in the art based on the TMA embodiments described herein. Accordingly, the scope of the invention is defined only by the claims.

Claims

1. Tower mounted amplifier (TMA) (100), arranged for receiving duplexed radio frequency (RF) signals, the TMA (100) comprising: a first port (110), arranged to receive a Tx signal and output an Rx signal; a second port (120), arranged to receive an Rx signal and output a Tx signal; an RF power harvester (150), arranged to generate a DC voltage and/or a DC current from the signal received on the first port (110); and at least one amplifier (130), arranged to amplify the signal received on the second port (120) before it is outputted on the first port (110). 2. TMA (100) according to claim 1, wherein the generated DC voltage and/or DC current is used for feeding components within the TMA (100), preferably components that are used for preventing RF signals received on the first port (110) from reaching the at least one amplifier (130).

3. TMA (100) according to claim 1 or 2, wherein the TMA (100) comprises functionality for detecting power received on the first port (110), e.g. using the RF power harvester (150). 4. TMA (100) according to claim 3, wherein the TMA (100) comprises short-circuit points (160) that are arranged to, when power is detected on the first port (110), short-circuit any RF signal that does not flow to the second port (120), so that it is reflected instead of reaching the at least one amplifier (130).

5. TMA (100) according to claim 4, wherein the short-circuit points (160) are short-circuited using PIN diodes (165), and the generated DC voltage and/or DC current is used for biasing said PIN diodes (165). 6. TMA (100) according to any one of claims 3-5, wherein the TMA (100) comprises a switching arrangement (140), wherein the switching arrangement (140) is arranged to, when power is detected on the first port (110), prevent the signal received on the first port (110) from reaching the at least one amplifier (130).

7. TMA (100) according to claim 6, wherein the switching arrangement (140) is arranged to: when power is detected on the first port (110), be set to allow the signal received on the first port (110) to flow through the switching arrangement (140) directly to the second port (120), without passing the at least one amplifier (130); and when no power is detected on the first port (110), be set to prevent the signal received on the second port (120) from flowing through the switching arrangement (140) on its way to the first port (110), so that the signal received on the second port (120) is instead fed to the at least one amplifier (130), allowing the at least one amplifier (130) to amplify the signal received on the second port (120) before outputting it on the first port (110).

8. TMA (100) according to claim 6 or 7, wherein the TMA (100) comprises at least one circulator (170) that is arranged to prevent any signal received on the first port (110) from reaching the at least one amplifier (130).

9. TMA (100) according to any one of claims 6-8, wherein the switching arrangement (140) comprises a combination of hybrid couplers (181, 182), and/or circulators (170, 171, 172), and one or more PIN diodes (195), and the generated DC voltage and/or DC current is used for biasing the one or more PIN diodes (195) in the switching arrangement (140).

10. TMA (100) according to any one of claims 1-9, wherein the TMA is a time division multiplex TMA (TDD- TMA).

11. Method (900) for generating a DC voltage and/or a DC current in a tower mounted amplifier (TMA)

(100) arranged for receiving duplexed radio frequency (RF) signals, the method (900) comprising: receiving (910) a Tx signal on a first port (110); generating (920) a DC voltage and/or a DC current from the signal received on the first port (110), e.g. using an RF power harvester (150); receiving (940) an Rx signal on a second port (120); amplifying (950) the signal received on the second port (120); and outputting (960) said amplified signal on the first port (110).

12. Method (900) according to claim 11, further comprising using (925) the generated DC voltage and/or DC current for feeding components within the TMA (100), preferably components that are used for preventing RF signals received on the first port (110) from reaching the at least one amplifier (130).

13. Method (900) according to claim 11 or 12, further comprising detecting (930) power on the first port (110), e.g. using an RF power harvester (150).

14. Method (900) according to claim 13, further comprising, when power is detected on the first port (110), short-circuiting (970) any RF signal that does not flow to the second port (120) in short-circuit points (160), so that the signal is reflected instead of reaching the at least one amplifier (130).

15. Method (900) according to claim 14, further comprising using (975) the generated DC voltage and/or DC current for biasing PIN diodes (165) used for short-circuiting the short-circuit points (160).

16. Method (900) according to any one of claims 13-15, further comprising, when power is detected on the first port (110), using (980) a switching arrangement (140) to prevent as much as possible of the signal received on the first port (110) from reaching the at least one amplifier (130).

17. Method (900) according to claim 16, further comprising: when power is detected on the first port (110), setting (985) the switching arrangement (140) to allow the signal received on the first port (110) to flow through the switching arrangement (140) directly to the second port (120), without passing the at least one amplifier (130); and when no power is detected on the first port (110), setting (985) the switching arrangement (140) to prevent the signal received on the second port (120) from flowing through the switching arrangement (140) on its way to the first port (110), so that the signal received on the second port (120) is instead fed to the at least one amplifier (130), allowing the at least one amplifier (130) to amplify the signal received on the second port (120) before outputting it on the first port (110).

18. Method (900) according to claim 16 or 17, further comprising using (990) at least one circulator (170) to prevent any signal received on the first port (110) from reaching the at least one amplifier (130). 19. Method (900) according to any one of claims 16-18, wherein the switching arrangement (140) comprises a combination of hybrid couplers (181, 182), and/or circulators (170, 171, 172), and one or more PIN diodes (195), further comprising using the generated DC voltage and/or DC current for biasing the one or more PIN diodes (195) in the switching arrangement (140).

20. Method (900) according to any one of claims 11-19, wherein the TMA is a time division multiplex TMA (TDD-TMA).