Remote radio head unit system with wideband power amplifier and method

• US 8,730,786 B2
• Filed: 12/21/2010
• Issued: 05/20/2014
• Est. Priority Date: 12/21/2009
• Status: Active Grant

• Current Assignee: Dali Systems Co., Ltd.
• Original Assignee: Dali Systems Co., Ltd.
• Inventors: Wang, Chengxun, Stapleton, Shawn Patrick
• Primary Examiner(s): Harper, Kevin C
• Application Number:
  US12/928,933
• Publication Number:
  US 20110158081A1
• Time in Patent Office: 1,246 Days
• Field of Search: None
• US Class Current: 370/201
• CPC Class Codes: H03F 1/304 and using digital means
• CPC Class Codes: H03F 1/3241 using predistortion circuits H03F1/3211, H03F1/3217 take precedence
• CPC Class Codes: H03F 1/3247 using feedback acting on predistortion circuits H03F1/3264 takes precedence
• CPC Class Codes: H03F 1/3258 based on polynomial terms
• CPC Class Codes: H03F 2200/18 the bias of the gate of a FET being controlled by a control signal
• CPC Class Codes: H03F 2200/204 A hybrid coupler being used at the output of an amplifier circuit
• CPC Class Codes: H03F 2200/207 A hybrid coupler being used as power measuring circuit at the output of an amplifier circuit
• CPC Class Codes: H03F 2200/447 the amplifier being protected to temperature influence
• CPC Class Codes: H03F 2200/451 the amplifier being a radio frequency amplifier
• CPC Class Codes: H03F 2201/3206 Multiple channels are combined and amplified by only one amplifier
• CPC Class Codes: H03F 2201/3209 the amplifier comprising means for compensating memory effects
• CPC Class Codes: H03F 2201/3212 Using a control circuit to adjust amplitude and phase of a signal in a signal path
• CPC Class Codes: H03F 2201/3215 To increase the output power or efficiency
• CPC Class Codes: H03F 2201/3224 Predistortion being done for compensating memory effects
• CPC Class Codes: H03F 2201/3227 Adaptive predistortion based on amplitude, envelope or power level feedback from the output of the main amplifier
• CPC Class Codes: H03F 3/087 with IC amplifier blocks H03F3/085 takes precedence
• CPC Class Codes: H03F 3/19 with semiconductor devices only
• CPC Class Codes: H03F 3/24 of transmitter output stages
• CPC Class Codes: H04L 25/03343 Arrangements at the transmitter end
• CPC Class Codes: H04L 25/067 providing soft decisions, i.e. decisions together with an estimate of reliability H04L25/068 and H04L25/069 take precedence; sequence estimation techniques H04L25/03178
• CPC Class Codes: H04L 25/08 : Modifications for reducing interference; Modifications for reducing effects due to line faults ; Receiver end arrangements for detecting or overcoming line faults
• CPC Class Codes: H04L 27/0008 : arrangements for allowing a transmitter or receiver to use more than one type of modulation negotiating modulation type for two-way transmission paths H04L5/1453
• CPC Class Codes: H04L 27/368 : adaptive predistortion
• CPC Class Codes: H04W 24/02 : Arrangements for optimising operational condition

Abstract

A remote radio head unit (RRU) system for multiple operating frequency bands, multi-channels, driven by a single or more wide band power amplifiers. More specifically, the present invention enables multiple-bands RRU to use fewer power amplifiers in order to reduce size and cost of the multi-band RRU. The present invention is based on the method of using duplexers and/or interference cancellation system technique to increase the isolation between the transmitter signal and receiver signal of the RRU.

Claims

1. An interference mitigation system for improving isolation between transmitters and receivers in wireless communications systems comprising:

a power amplifier that amplifies a transmit signal that is transmitted by the system;

a feedback coupler that generates a feedback signal based on the amplified transmit signal, wherein the feedback signal is representative of an interference characteristic attributed to the amplified transmit signal,

an interference cancellation unit that;

monitors the interference characteristic;

adjusts an interference-reduction variable based on the interference characteristic;

processes the feedback signal in accordance with the interference-reduction variable to generate a processed signal; and

a combiner that combines an intake signal received from a receiver and the processed signal to generate a combined signal, wherein the intake signal includes a first component from a signal and a second component from interference from the transmit signal; and

a switch that changes its position from a first position to a second position at times corresponding to a time-division duplexing technique, wherein the intake signal is combined with the processed signal while the switch is in the second position.

2. The interference mitigation system of claim 1, wherein the interference cancellation unit includes a delay block, an attenuator and a phase shifter.

3. The interference mitigation system of claim 1, further comprising switch-operating logic that controls the position of the switch.

4. The interference mitigation system of claim 1, further comprising a second switch that changes its position at times corresponding to the time-division duplexing technique.

5. The interference mitigation system of claim 1, further comprising a multiplexer that isolates each of a plurality of frequency bands within the amplified transmit signal, wherein the amplified transmit signal processed by the interference cancellation unit includes an isolated frequency band of the amplified transmit signal.

6. The interference mitigation system of claim 1, further comprising a second feedback coupler for generating a second feedback signal based on the combined signal, wherein the second feedback signal is representative of the combined signal, wherein the interference cancellation unit further processes the second feedback signal to generate the processed signal.

7. The interference mitigation system of claim 6, wherein the interference cancellation unit processes the feedback signal and the second feedback signal using a correlation technique.

8. The interference mitigation system of claim 6, wherein the interference cancellation unit is comprised of a delay block, an attenuator and a phase shifter.

9. The interference mitigation system of claim 6, further comprising one or more switches and switch-operating logic that controls a position of each of the one or more switches, wherein the switch-operating logic causes switch changes to occur at times corresponding to a time-division duplexing technique.

10. The interference mitigation system of claim 6 further comprising a multiplexer that isolates each of a plurality of frequency bands within the amplified transmit signal, wherein the amplified transmit signal processed by the interference cancellation unit includes an isolated frequency band of the amplified transmit signal.

11. The interference mitigation system of claim 6, further comprising a circulator and duplexer that isolate the intake signal by isolating a Frequency Division Multiplexed signal.

12. The interference mitigation system of claim 6, wherein the intake signal corresponds to a signal received from a first antenna, and wherein the transmit signal is transmitted via a second antenna, and wherein the separate antennae enable the system to operate in Frequency Duplex Mode.

13. The interference mitigation system of claim 6, wherein the interference cancellation unit is comprised of a variable delay block, variable attenuator and variable phase shifter.

14. A method for improving isolation between transmitters and receivers in wireless communications systems, the method comprising:

amplifying a transmit signal;

transmitting the transmit signal;

generating a feedback signal based on the amplified transmit signal, wherein the feedback signal is representative of an interference characteristic attributed to the amplified transmit signal; and

monitoring the interference characteristic;

adjusting an interference-reduction variable based on the interference characteristic;

processing the feedback signal in accordance with the interference-reduction variable to generate a processed signal;

combining an intake signal and the processed signal to generate a combined signal, wherein the intake signal includes a first component from a signal received by a receiver and a second component from interference from the transmit signal; and

causing a position of a switch to change from a first position to a second position at times corresponding to a time-division duplexing technique, wherein the intake signal is combined with the processed signal while the switch is in the second position.

15. The method of claim 14, wherein the processing includes one or more of introducing a delay, attenuation and phase shift to the feedback signal.

16. The method of claim 14, further comprising causing a position of a second switch to change at times corresponding to the time-division duplexing technique.

17. The method of claim 14, further comprising isolating each of a plurality of frequency bands within the amplified transmit signal, wherein the amplified transmit signal being processed includes an isolated frequency band of the amplified transmit signal.

18. The method of claim 14, further comprising generating a second feedback signal based on the combined signal, wherein the second feedback signal is representative of the combined signal, and wherein the feedback signal is processed with the second feedback signal to generate the processed signal.

19. The method of claim 18, wherein the feedback signal and the second feedback signal are processed using a correlation technique.