System combining radio frequency transmitter and receiver using circulator and method for canceling transmission signal thereof

• US 6,567,648 B1
• Filed: 09/07/2000
• Issued: 05/20/2003
• Est. Priority Date: 11/23/1999
• Status: Expired due to Fees

• Current Assignee: Dal Ahn, Telwave, Inc.
• Original Assignee: Dal Ahn, Telwave, Inc.
• Inventors: Ahn, Dal, Park, Jun Seok, Park, Jong Chul, Kwak, Won Jun, Yoon, Chul Sang
• Primary Examiner(s): Le, Thanh Cong
• Assistant Examiner(s): TRINH, TAN H
• Application Number:
  US09/656,945
• Time in Patent Office: 985 Days
• Field of Search: 455/78, 455/80, 455/81, 455/82, 455/83, 455/24, 455/63, 455/278.1, 333/126, 333/129, 333/132, 333/134, 333/1.1, 333/24.2
• US Class Current: 455/83
• CPC Class Codes: H04B 1/525 with means for reducing leakage of transmitter signal into the receiver

Abstract

A transmitter/receiver combination system and a transmission signal canceling method for use in a wireless communication system using a single common antenna are provided. The system includes a circulator for receiving an original transmission signal from the transmitter, transmitting the received transmission signal to an antenna without a signal loss, and transmitting a reception signal received from the antenna to other ends without a signal loss, and a transmission signal canceller for dividing the transmission signal input in an attenuated form as much as a predetermined magnitude via the circulator together with the reception signal into two paths, producing two is phase inverted transmission signals with the same magnitude and delay time as those of the original transmission signal, and recombining the produced two transmission signals with each other, to thereby canceling the transmission signal and transmitting only the reception signal to the receiver.

Claims

1. A transmitter/receiver combination system for combining a transmitter and a receiver into a single antenna in a wireless communication system, the transmitter/receiver combination system comprising:

a circulator for receiving a transmission signal Tx from the transmitter, transmitting the received transmission signal to an antenna without causing a signal loss, and transmitting a reception signal Rx received from the antenna to other ends without causing a signal loss; and

at least one transmission signal canceller for dividing the transmission signal Tx input in an attenuated form as much as a predetermined magnitude via the circulator together with the reception signal Rx into at least two paths, producing two phase inverted transmission signals (−

Tx, Tx) with the same magnitude and delay time as those of the incoming transmission signal, and recombining the produced two transmission signals with each other, to thereby canceling the transmission signal Tx and transmitting only the reception signal Rx to the receiver.

2. The transmitter/receiver combination system of claim 1, wherein said transmission signal canceller comprises:

a first coupler for attenuating a part of the transmission/reception signal Tx+Rx which is input to the transmission signal canceller to branch the same and simultaneously performing a 90°

phase delay;

a first variable band rejection filter for canceling the reception signal Rx and passing through only a transmission signal Tx with respect to a low power transmission/reception signal Tx+Rx which has been branched via the first coupler;

a signal amplifier for amplifying the transmission signal Tx of the first variable band rejection filter into the same magnitude as that of the transmission signal Tx;

phase delay means for delaying a time so that the transmission/reception signal Tx+Rx unbranched in the first coupler is consistent with the inverted signal of the branched transmission signal Tx; and

a second coupler for 90°

phase delaying the output signal of the signal amplifier additionally, and recombining the phase delayed result with the output signal Tx+Rx of the phase delay means, to thereby offset the unbranched transmission signal Tx with the phase inverted transmission signal −

Tx and output only the reception signal Rx.

3. The transmitter/receiver combination system of claim 1, wherein said transmitter comprises a first variable filter for varying a pass band of a transmission signal Tx by several thousand number of times per second and transferring the varied result to a next stage, a power amplifier for large-scale power amplifying the output of the first variable filter, and a harmonic filter for removing a harmonic component included in a power-amplified transmission signal, and

wherein said receiver comprises a second variable filter whose pass band is varied in order to remove an unnecessary wave other than the reception signal Rx, in which its pass band is set to only the reception signal Rx output from the canceller, and a low noise amplifier for low-noise-amplifying the received feeble reception signal Rx.

4. The transmitter/receiver combination system of claim 2, further comprising at least one noise signal attenuation means disposed between the transmitter and the circulator for generating a signal together with the transmission signal Tx from the transmitter and attenuating only a noise signal Nx of a reception band input to the receiver.

5. The transmitter/receiver combination system of claim 4, wherein said noise signal attenuation means comprises:

a third coupler for branching a portion of the noise signal Nx and the transmission signal Tx amplified together with the transmission signal Tx and for phase delaying the branched signal by 90°

;

a second variable band rejection filter for rejecting the transmission signal Tx and passing only the noise signal Nx with respect to the low power transmission/noise signal (Tx+Nx) branched via the third coupler;

a signal amplifier for amplifying the noise signal Nx from the second variable band rejection filter into the same magnitude of that of the unbranched noise signal Nx;

a harmonic cancel/delay line filter for making the transmission/noise signal Tx+Nx unbranched from the third coupler have the same delay as that of the branched noise signal Nx and simultaneously canceling harmonic components, and

a fourth coupler for additionally phase delaying the output signal Nx of the signal amplifier by 90° and

recombining the phase delayed result with the output signal Tx+Nx from the harmonic cancel/delay line filter, to thereby offset the unbranched noise signal Nx and the phase inverted noise signal −

Nx with each other, and thus output only a desired large power transmission signal Tx to the circulator.

6. The transmitter/receiver combination system of claim 5, wherein the transmission/reception frequencies of the transmission/reception signals, and the rejection bands of the first and second variable band rejection filters are varied.

7. The transmitter/receiver combination system of claim 5, wherein the transmission/reception frequencies of the transmission/reception signals are inverted with each other.

8. A transmitter/receiver combination system for combining a transmitter and a receiver into a single antenna in a wireless communication system, the transmitter/receiver combination system comprises:

noise signal attenuation means connected to the output of the transmitter, for attenuating only a noise signal of a reception band generated together with a transmission signal from the transmitter;

a circulator for receiving the transmission signal from the noise signal attenuation means, transmitting the received signal to an antenna without causing a signal loss, and transmitting the reception signal received from the antenna to other ends without causing a signal loss; and

a first variable filter for canceling the transmission signal input in an attenuated form as much as a predetermined magnitude via the circulator together with the reception signal and transmitting only a reception signal to the receiver.

9. The transmitter/receiver combination system of claim 8, wherein said receiver comprises:

a low noise amplifier for low noise amplifying the feeble reception signal received in the first variable filter; and

a second variable filter whose pass band is varied in order to remove an unnecessary wave other than the reception signal, in which only the reception signal becomes a pass band.

10. A transmitter/receiver combination system for combining a transmitter and a receiver into a single antenna in a wireless communication system, the transmitter/receiver combination system comprising:

a first circulator for receiving an original transmission signal from the transmitter, and transmitting the received transmission signal to a next stage without causing a signal loss;

a second circulator for receiving the transmission signal from the first circulator, transmitting the received signal to an antenna without causing a signal loss, and transmitting the reception signal received from the antenna to other ends without causing a signal loss;

a first pad and a second pad for receiving a first transmission signal input in an attenuated form as much as a predetermined magnitude via the other end of the first circulator and a second transmission signal input in an attenuated form as much as a predetermined magnitude via the other end of the second circulator, and for converting the first and second transmission signals into two transmission signals whose magnitudes are same and phases are inverted, respectively; and

signal combination means for combining the output signals of the first and second pads, canceling the first and second transmission signals and transmitting only the reception signal to the receiver.

11. The transmitter/receiver combination system of claim 10, wherein said at least one of the first and second pads comprises:

an attenuator for attenuating the magnitude of a transmission signal in the same magnitude as that of the other transmission signal; and

phase delay means for delaying the phase of the signal in order to have a 180°

phase difference with respect to the other transmission signal.

12. The transmitter/receiver combination system of claim 11, wherein said phase delay means is provided in the first pad.

13. The transmitter/receiver combination system of claim 10, wherein said transmitter comprises a first variable filter for varying a pass band of a transmission signal by several thousand number of times per second and transferring the varied result to a next stage, a power amplifier for large-scale power amplifying the output of the first variable filter, and a harmonic filter for removing a harmonic component included in a power-amplified transmission signal, and

wherein said receiver comprises a second variable filter whose pass band is varied in order to remove an unnecessary wave other than the reception signal, in which only the reception signal Rx output from the canceller becomes a pass band, and a low noise amplifier for low-noise-amplifying the received feeble reception signal.

14. A front-end for use in a wireless communication system:

a first variable filter for varying a pass band of a transmission signal Tx by several thousand number of times per second and transferring the varied result to a next stage;

a power amplifier for large-scale power amplifying the output of the first variable filter;

a harmonic filter for removing a harmonic component included in a power-amplified transmission signal;

a circulator for receiving the transmission signal via a first end, transmitting the received transmission signal to a second end, and transmitting a reception signal Rx received from the second end to a third end without causing a signal loss;

a transmission/reception common antenna connected to the second end of the circulator, radiating the transmission signal Tx in the air and receiving the reception signal to be transferred to the circulator;

at least one transmission signal canceller for dividing the transmission signal input in an attenuated form as much as a predetermined magnitude via the circulator together with the reception signal into at least two paths, producing two phase inverted transmission signals (−

Tx, Tx) with the same magnitude and delay time as those of the incoming transmission signal, recombining the produced two transmission signals with each other, to thereby canceling the transmission signal and transmitting only the reception signal to the receiver;

a second variable filter whose pass band is varied in order to remove an unnecessary wave other than the reception signal Rx, in which only the reception signal Rx output from the canceller becomes a pass band; and

a low noise amplifier for low-noise-amplifying the received feeble reception signal Rx.

15. The front-end for use in a wireless communication system of claim 14, further comprising noise signal attenuation means for generating a signal together with the transmission signal from the transmitter disposed between the transmitter and the circulator and attenuating only a noise signal of a reception band input to the receiver.

16. The front-end for use in a wireless communication system of claim 14, wherein the transmission/reception frequencies of the transmission/reception signals, and the pass bands of the first and second variable filters are varied.

17. A front-end for use in a wireless communication system:

a first variable filter for varying a pass band of a transmission signal by several thousand number of times per second and transferring the varied result to a next stage;

a power amplifier for large-scale power amplifying the output of the first variable filter;

a harmonic filter for removing a harmonic component included in a power-amplified transmission signal;

a first circulator for receiving the transmission signal from the harmonic filter, and transmitting the received transmission signal to a next stage, without causing a signal loss;

a second circulator for receiving the transmission signal from the first circulator, transmitting the received signal to an antenna without causing a signal loss, and transmitting the reception signal received from the antenna to other ends without causing a signal loss;

a first pad and a second pad for receiving a first transmission signal input in an attenuated form as much as a predetermined magnitude via the other end of the first circulator and a second transmission signal input in an attenuated form as much as a predetermined magnitude via the other end of the second circulator, and for converting the first and second transmission signals into two transmission signals whose magnitudes are same and phases are inverted, respectively;

signal combination means for combining the output signals of the first and second pads, canceling the first and second transmission signals and transmitting only a reception signal to a receiver;

a second variable filter whose pass band is varied in order to remove an unnecessary wave other than the reception signal, in which only the reception signal output from the signal combination means becomes a pass band; and

a low noise amplifier for low-noise-amplifying the received feeble reception signal.

18. A transmission signal canceling method in a transmitter/receiver combination system for combining a transmitter and a receiver into a single antenna in a wireless communication system, the transmission signal canceling method comprising the steps of:

(a) receiving an original transmission signal from the transmitter, transmitting the received transmission signal to an antenna via a first path without causing a signal loss, and transmitting a reception signal received from the antenna via a second path;

(b) 90°

phase delaying for delaying part of the transmission signal the reception signal input to the receiver in an attenuated form as much as a predetermined magnitude via the second path and branching the phase delayed result into a third path;

(c) canceling the reception signal among the transmission signal the reception signal which branched via the third path, and amplifying the transmission signal in the same magnitude as that of the second path;

(d) delaying the transmission signal and the reception signal of the unbranched second path to have a phase difference of 180°

from the transmission signal of the branched third path; and

(e) combining the phase inverted transmission signal of the third path with the phase delayed transmission signal and the reception signal of the second path, canceling the transmission signal and transmitting only a reception signal to the receiver.

19. The transmission signal canceling method of claim 18, further comprising the step of (f) generating a signal together with the transmission signal before the step (a) and attenuating only the noise signal of the reception band input to the receiver.

20. A transmission signal canceling method in a transmitter/receiver combination system for combining a transmitter and a receiver into a single antenna in a wireless communication system, the transmission signal canceling method comprising the steps of:

(a) transmitting a transmission signal received from the transmitter, via a first path without causing a signal loss and generating a first transmission signal which has been attenuated as much as a predetermined magnitude via a second path;

(b) transmitting the received transmission signal to an antenna without causing a signal loss, and transmitting the reception signal received from the antenna to a third path without causing a signal loss;

(c) receiving the first transmission signal via the second path, and a second transmission signal input in an attenuated form as much as a predetermined magnitude via the third path by the transmission signal together with the reception signal, and converting the first and second transmission signals into two transmission signals whose magnitudes are same and phases are inverted; and

(d) combining the outputs of the second and third paths so that the first and second transmission signals are cancelled.