US 8,913,694 B2Granted

Fast LO leakage calibration of direct up-conversion transmitters using three measurements

AssigneeMStar Semiconductor, Inc.

InventorsWael Al-Qaq, Dennis Mahoney

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Abstract

A direct conversion transmitter has a mixer stage to up-convert an input signal to the frequency of a local oscillator (LO). A DC offset circuit is coupled to an input signal port to apply a set of DC offset signal values. A processor determines a set of optimal DC offset signal values by no more than three differential spectral measurements made at the transmitter output port with a test signal applied at the input port. Optimal DC offset signal values are those that, when applied to the input signal at the input port of the transmitter, minimize an LO leakage component of the transmit signal at the output signal port of the transmitter. The optimal DC offset values are stored in memory and retrieved and applied to information bearing signals provided as the input signal once those optimal DC offset values have been determined.

Claims19

Dependent claims

An apparatus comprising:

a direct conversion transmitter in a communication device, the direct conversion transmitter comprising:
an input signal port to receive an input signal;
an output signal port to output a transmit signal at a transmit frequency for transmission;
a mixer stage to up-convert a representation of the input signal to a local oscillator (LO) frequency of a LO coupled thereto;
and
a DC offset circuit to apply a set of DC offset signal values to the input signal;
a memory to store the DC offset signal values;
and
a processor configured to:
determine an optimal set of the DC offset signal values by at most three differential spectral measurements made at the transmitter output port with a calibration signal applied at the input port, the set of optimal DC offset signal values being those that minimizes a LO leakage component of the transmit signal at the output signal port of the transmitter when the set of optimal DC offset signal values are applied to the input signal at the input port of the transmitter;
store the optimal set of DC offset values in the memory;
and
apply the stored optimal set of DC offset values to information bearing signals provided as the input signal subsequent to the determination of the set of optimal DC offset signal values.

10 more elements

A method comprising:

providing a calibration signal to an input port of a transmitter of a communication device;
determining an optimal set of DC offset signal values by at most three differential spectral measurements made at an output port of the transmitter while the calibration signal is applied at the input port, the set of optimal DC offset signal values being those that minimizes a local oscillator (LO) leakage component of the transmit signal at the output signal port of the transmitter when the set of optimal DC offset signal values are applied to an input signal at the input port of the transmitter;
storing the set of optimal DC offset values in the memory;
and
applying, to a DC offset circuit coupled to the input port of the transmitter, the stored set of optimal DC offset values to information bearing signals provided as the input signal subsequent to the determination of the optimal set of DC offset signal values.

2 more elements

A tangible, non-transitory computer readable medium having encoded thereon processor instructions that, when executed by a processor coupled to a direct conversion transmitter in a communication device, where the direct conversion transmitter comprising an input signal port to receive an input signal, an output signal port to output a transmit signal for transmission, a mixer stage to up-convert a representation of the input signal to a frequency of a local oscillator (LO) coupled thereto, and a DC offset circuit to apply a set of DC offset signal values at the input signal port, configures the processor to:

determine an optimal set of the DC offset signal values by at most three differential spectral measurements made at the transmitter output port with a calibration signal applied at the input port, the set of optimal DC offset signal values being those that minimizes an LO leakage component of the transmit signal at the output signal port of the transmitter when the optimal set of DC offset signal values is applied to the input signal at the input port of the transmitter;
store the set of optimal DC offset values in a memory;
and
apply the stored set of optimal DC offset values to information bearing signals provided as the input signal subsequent to the determination of the optimal set of DC offset values.

1 more element

Dependencies are inferred from the claim text.