Transmitter image suppression in TDD transceivers

• US 6,717,981 B1
• Filed: 12/14/1999
• Issued: 04/06/2004
• Est. Priority Date: 12/14/1999
• Status: Expired due to Term

• Current Assignee: ST-Ericcson SA (Telefonaktiebolaget LM Ericsson)
• Original Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Inventors: Mohindra, Rishi
• Primary Examiner(s): TSE, YOUNG TOI
• Application Number:
  US09/460,929
• Time in Patent Office: 1,575 Days
• Field of Search: 375/219, 375/221, 375/222, 375/259, 375/377, 375/279, 375/280, 375/281, 375/283, 455/76, 455/78, 455/83, 455/88, 455/24, 455/69, 370/278, 370/280, 370/282, 370/294
• US Class Current: 375/219
• CPC Class Codes: H04B 1/0475 with means for limiting noise, interference or distortion H04B1/0483 takes precedence

Abstract

In a transceiver comprising a time-division-duplex (TDD) of transmit and receive functions, the characteristics of unwanted image signal energy being transmitted from the transceiver are determined, and thereafter feedback is provided to the transmitter to reduce this unwanted image signal energy. The image signal energy is measured by the receiver component of the transceiver and fed back to the transmitter component of the transceiver. The transmitter component uses the fed back information to adjust the gain and or phase relationship between the quadrature signals that are subsequently quadrature-phase modulated and transmitted. A variety of techniques can be employed to allow the image signal energy to be measured directly by the receiver component. The phase modulation signals at the transmitter can be interchanged, so that the unwanted image signal energy is transmitted in the sideband of the intended signal. Alternatively, the phase modulation signals at the receiver can be interchanged, so that the receiver'"'"'s operating frequency is shifted from the frequency of the transmitter'"'"'s intended signal sideband to the frequency of the transmitter'"'"'s unwanted image signal sideband.

Claims

1. A transceiver comprising:

a transmitter that is configured to receive an input signal and produces therefrom an in-phase transmit signal and a quadrature-phase transmit signal,

a modulator that is configured to modulate the in-phase transmit signal and the quadrature-phase transmit signal and to produce therefrom a composite signal that includes an intended signal component and an unwanted signal component,

a demodulator that is selectively configured to demodulate the composite signal and to produce therefrom an in-phase receive signal and a quadrature-phase receive signal, and

a receiver that is configured to receive the in-phase receive signal and the quadrature-phase receive signal, and to produce therefrom a characterization signal that is correlated substantially to the unwanted signal component of the composite signal,

wherein

the transceiver is configured to adjust at least one of a phase and an amplitude of at least one of the in-phase transmit signal and the quadrature-phase transmit signal, based on the characterization signal.

2. The transceiver of claim 1, further including

a local oscillator that is configured to provide a first oscillation signal and a second oscillation signal, and

wherein

the phase of the least one of the in-phase transmit signal and the quadrature-phase transmit signal is adjusted by modifying a phase relationship between the first oscillation signal and the second oscillation signal.

3. The transceiver of claim 2, further comprising a switch which is configured to interchange said first oscillation signal and said second oscillation signal to form a first interchanged oscillation signal and a second interchanged oscillation signal;

wherein said modulator produces said composite signal in response to one of said first oscillation signal and said second oscillation signal and said first interchanged oscillation signal and said second interchanged oscillation signal, and said demodulator demodulates said composite signal in response to another of said first oscillation signal and said second oscillation signal and said first interchanged oscillation signal and said second interchanged oscillation signal.

4. The transceiver of claim 1, further comprising:

a double quadrature module that provides a high image rejection at the receiver, thereby providing a high sensitivity to the characterization signal.

5. The transceiver of claim 1, wherein

the intended signal component is located at a first sideband frequency,

the unwanted signal component is located at a second sideband frequency, and

the transceiver further includes a switch that is configured to effect a frequency change at the receiver such that the receiver is centered at the second sideband frequency.

6. The transceiver of claim 5, further including

a local oscillator that is configured to provide an in-phase oscillation signal and a quadrature-phase oscillation signal, and

wherein

the demodulator is configured to demodulate the composite signal based on the in-phase oscillation signal and the quadrature-phase oscillation signal, and

the switch is configured to effect the tuning frequency change by interchanging the in-phase oscillation signal and the quadrature-phase oscillation signal.

7. The transceiver of claim 1, wherein

the receiver is further configured to produce the characterization signal based on a receiver tuning frequency, and

the transceiver further includes a switch that is configured to effect a change in the modulator so that the unwanted signal component is produced at the receiver tuning frequency.

8. The transceiver of claim 7, further including

a local oscillator that is configured to provide an in-phase oscillation signal and a quadrature-phase oscillation signal, and

wherein

the modulator is configured to produce the composite signal based on the in-phase oscillation signal and the quadrature-phase oscillation signal, and

the switch is configured to effect the change in the modulator to produce the unwanted signal component at the receiver tuning frequency by interchanging the in-phase oscillation signal and the quadrature-phase oscillation signal.

9. The transceiver of claim 1, further comprising an oscillator that is configured to form a first oscillating signal and a second oscillating signal;

and a switch which is configured to interchange said first oscillating signal and said second oscillating signal to form a first interchanged oscillating signal and a second interchanged oscillating signal;

said modulator being configured to receive one of said first oscillating signal and said second oscillating signal and said first interchanged oscillating signal and said second interchanged oscillating signal, and said demodulator being configured to receive another of said first oscillating signal and said second oscillating signal and said first interchanged oscillating signal and said second interchanged oscillating signal.

10. A method of suppressing an unwanted signal component from a transmission of a transceiver, the method comprising:

receiving an input signal and producing therefrom an in-phase transmit signal and a quadrature-phase transmit signal,

modulating the in-phase transmit signal and the quadrature-phase transmit signal and producing therefrom a composite signal that includes an intended signal component and the unwanted signal component,

demodulating the composite signal and producing therefrom an in-phase receive signal and a quadrature-phase receive signal,

receiving the in-phase receive signal and the quadrature-phase receive signal, and producing therefrom a characterization signal that is correlated substantially to the unwanted signal component of the composite signal,

and adjusting at least one of a phase and an amplitude of at least one of the in-phase transmit signal and the quadrature-phase transmit signal, based on the characterization signal, to suppress the unwanted signal component.

11. The method of claim 10, wherein

the intended signal component is located at a first sideband frequency,

the unwanted signal component is located at a second sideband frequency, and

the method further includes

changing a receiver center frequency such that the characterization signal is based on a measure of a signal that is received at the second sideband frequency.

12. The method of claim 11, further including

providing an in-phase oscillation signal and a quadrature-phase oscillation signal, and

wherein

the demodulating of the composite signal includes

demodulating the composite,signal based on the in-phase oscillation signal and the quadrature-phase oscillation signal, and

the changing of the receiver center frequency includes

interchanging the in-phase oscillation signal and the quadrature-phase oscillation signal.

13. The method of claim 11, wherein

producing the characterization signal is based on the receiver center frequency, and

modulating the in-phase transmit signal and the quadrature-phase transmit signal is effected so as to provide the unwanted signal component at the receiver center frequency.

14. The method of claim 13, further including

providing an in-phase oscillation signal and a quadrature-phase oscillation signal, and

wherein

modulating the in-phase transmit signal and the quadrature-phase transmit signal to provide the unwanted signal component at the receiver center frequency is effected by interchanging the in-phase oscillation signal and the quadrature-phase oscillation signal.

15. The method of claim 10, wherein

adjusting the phase of at least one of the in-phase transmit signal and the quadrature-phase transmit signal includes adjusting the relative phase of a first oscillation signal and a second oscillation signal that are used to effect at least one of modulating the in-phase transmit signal and the quadrature-phase transmit signal and demodulating the composite signal.

16. A transceiver comprising:

a receiver that is configured to receive first information signals,

a transmitter that is configured to transmit second information signals, and

a switch that is configured to couple the transmitter and the receiver so that the first information signals received by the receiver correspond to the second information signals that are transmitted from the transmitter during a calibration mode,

wherein

the transceiver is configured to provide for an adjustment of at least one of a phase and a gain of the second information signals in dependence upon the first information signals that are received during the calibration mode,

wherein said switch is further configured to interchange an I transmit signal and a Q transmit signal from a local oscillator to form a Q receive signal from said I transmit signal and an I receive signal from said Q transmit signal, said Q receive signal and said I receive signal being provided to said receiver.

17. A method of calibrating a transmitter in a transceiver that includes a receiver comprising:

transmitting a first signal via the transmitter,

interchanging an I transmit signal and a Q transmit signal from a local oscillator to form a Q receive signal from said I transmit signal and an I receive signal from said Q transmit signal,

receiving the first signal, said Q receive signal, and said I receive signal via the receiver to provide a characterization signal, and

adjusting the transmitter in dependence upon the characterization signal.

18. The method of claim 17, wherein

adjusting the transmitter includes adjusting at least one of a phase or a gain of the transmitter to facilitate reduction of unwanted signals.

19. The method of claim 17, wherein

adjusting the transmitter includes adjusting a phase of one or more oscillation signals provided to said transmitter to facilitate rejection of unwanted signals.

20. A transceiver comprising:

a transmitter that is configured to transmit a first signal;

a receiver that is configured to receive a second signal which is derived from said first signal;

a local oscillator that is configured to provide a transmit oscillating signal to said transmitter and a receive oscillating signal to said receiver, wherein said transmit oscillating signal is out of phase with said receive oscillating signal so that at least one of a phase and a gain of said first signal is adjusted in dependence upon the second signal; and

a switch, said transmit oscillating signal including an I transmit signal and a Q transmit signal, and said receive oscillating signal including an I receive signal and a Q receive signal;

wherein said switch is configured to interchange said I transmit signal and said Q transmit signal to form said Q receive signal from said I transmit signal and said I receive signal from said Q transmit signal.

21. The transceiver of claim 20, further comprising an attenuator which attenuates said first signal to form said second signal.

22. The transceiver of claim 20, wherein said second signal includes said first signal in an attenuated form.

23. The transceiver of claim 20, wherein said switch that is configured to provide said first signal from said transmitter to said receiver as said second signal.