Patent Description:
A transmit (TX) circuit in a wireless system chip is used to perform an up-conversion process that converts a TX signal from a lower frequency to a higher frequency for signal transmission. A receive (RX) circuit in the wireless system chip is used to perform a down-conversion process that converts an RX signal from a higher frequency to a lower frequency for signal reception. Further, each of the up-conversion process and the down-conversion process requires a local oscillator (LO) signal with a proper LO frequency setting. Typically, the LO signal is derived from a reference clock that is supplied from an off-chip oscillator. For example, the off-chip oscillator is a passive oscillator (e.g., a typical crystal oscillator (XO)). When the wireless system chip is used by an application device, the off-chip oscillator is also used by the application device due to the fact that the reference clock needed by the wireless system chip is supplied from the off-chip oscillator (e.g., XO). If the off-chip oscillator can be omitted, the BOM (bill of material) cost and the PCB (printed circuit board) area of the application device can be reduced.

<CIT> discloses a reference frequency calibration module.

<CIT> discloses a crystal-less communication device for use in wire-line/wireless communication system.

<CIT> disclose to a lock generator using passive mixer and associated clock generating method.

One of the objectives of the claimed invention is to provide a wireless system that uses a local oscillator signal derived from a reference clock output of an active oscillator that has no electromechanical resonator (e.g., crystal).

According the present invention, there is provided a wireless system according to claim <NUM>.

Certain terms are used throughout the following description and claims, which refer to particular components. As one skilled in the art will appreciate, electronic equipment manufacturers may refer to a component by different names. This document does not intend to distinguish between components that differ in name but not in function. In the following description and in the claims, the terms "include" and "comprise" are used in an open-ended fashion, and thus should be interpreted to mean "include, but not limited to. Also, the term "couple" is intended to mean either an indirect or direct electrical connection. Accordingly, if one device is coupled to another device, that connection may be through a direct electrical connection, or through an indirect electrical connection via other devices and connections.

The present invention proposes a crystal-less (XOless) technique for a wireless system. For example, the XOless technique may be integrated in a wireless system chip. Since an off-chip oscillator such as a crystal oscillator (XO) is not needed by the proposed wireless system chip, a BOM cost of an application device using the proposed wireless system chip can be reduced. Further details of the XOless technique are described with reference to the accompanying drawings.

<FIG> is a diagram illustrating a first wireless system according to an embodiment of the present invention. For example, the wireless system <NUM> may be a Radio Detection and Ranging (radar) system. For another example, the wireless system <NUM> may be a wireless communications system such as a Wi-Fi system. In this embodiment, the wireless system <NUM> is implemented on a chip <NUM>, and therefore has a plurality of on-chip components including an active oscillator <NUM>, a front-end circuit <NUM>, a digital macro <NUM>, a calibration circuit <NUM>, and a plurality of frequency processing circuits <NUM> and <NUM>. The active oscillator <NUM> includes at least one active component (e.g., transistor(s) and/or amplifier(s)), and does not include an electromechanical resonator such as a crystal, a bulk acoustic wave (BAW) resonator, or a microelectromechanical system (MEMS) resonator. That is, the active oscillator <NUM> is an electromechanical-resonator-less oscillator (e.g., a crystal-less oscillator), and does not consist of passive components (e.g., inductor(s), resistor(s), and/or capacitor(s)) only. For example, the active oscillator <NUM> may be an LC oscillator having an amplifier circuit and an LC frequency-selective network, where the LC frequency-selective network consists of on-chip passive components only, and is used to create a resonator needed for reference clock generation. For another example, the active oscillator <NUM> may be an RC oscillator having an amplifier circuit and an RC frequency-selective network, where the RC frequency-selective network consists of on-chip passive components only, and is used to create a resonator needed for reference clock generation. In this embodiment, the active oscillator <NUM> is an on-chip oscillator circuit arranged to generate and output a reference clock CK_REF.

In this embodiment, pin(s) of the chip <NUM> are not coupled to an off-chip oscillator <NUM> when the wireless system <NUM> is in operation. For example, the off-chip oscillator <NUM> is a crystal oscillator which uses the mechanical resonance of a vibrating crystal of piezoelectric material to create an electrical signal with a precise frequency. In other words, a normal operation of the wireless system <NUM> can be achieved with the reference clock CK_REF provided by the on-chip oscillator (i.e., active oscillator <NUM>), and does not require a reference clock supplied from the off-chip oscillator <NUM> such as a typical crystal oscillator. The off-chip oscillator <NUM> can be omitted in an application device when the proposed wireless system <NUM> is used by the application device. In this way, the BOM cost of the application device using the proposed wireless system <NUM> can be reduced.

The reference clock CK_REF may act as a system clock of the wireless system <NUM>. Hence, the reference clock CK_REF generated from the active oscillator <NUM> can be used to create periodical signals needed by normal operations of other on-chip components, including the front-end circuit <NUM>, the digital macro <NUM>, etc..

The front-end circuit <NUM> is arranged to process a transmit (TX) signal and/or a receive (RX) signal according to a local oscillator (LO) signal S_LO. In this embodiment, the front-end circuit <NUM> is a transceiver circuit having a TX circuit <NUM> and an RX circuit <NUM>, where the TX circuit <NUM> is coupled to an off-chip TX antenna <NUM>, and the RX circuit <NUM> is coupled to an off-chip RX antenna <NUM>. The TX circuit <NUM> is used to perform an up-conversion process that converts the TX signal from a lower frequency to a higher frequency for signal transmission via the TX antenna <NUM>. The RX circuit <NUM> is used to receive the RX signal from the RX antenna <NUM>, and perform a down-conversion process that converts the RX signal from a higher frequency to a lower frequency for signal reception. An LO frequency of the LO signal S_LO should be properly set to meet requirements of the up-conversion process and the down-conversion process. For example, the LO frequency may be set by a frequency value at a millimeter wave (mmWave) band, lower than the mmWave band, or higher than the mmWave band, depending upon the actual design considerations. In a case where the wireless system <NUM> is a radar system (e.g., an automotive radar system), the LO signal S_LO may have the LO frequency at a <NUM>-<NUM> band, <NUM>, <NUM>, a <NUM>-<NUM> band, or a <NUM>-<NUM> band. However, this is for illustrative purposes only, and is not meant to be a limitation of the present invention.

As shown in <FIG>, one frequency processing circuit <NUM> is arranged to receive the reference clock CK_REF with a reference frequency different from the LO frequency, generate the LO signal S_LO with the LO frequency according to the reference clock CK_REF, and output the LO signal S_LO to the front-end circuit <NUM> (particularly, TX circuit <NUM> and RX circuit <NUM>). For example, the frequency processing circuit <NUM> may include a phase-locked loop (PLL) circuit, a frequency multiplier circuit, and/or a frequency divider circuit, depending upon the discrepancy between the LO frequency of the LO signal S_LO and the reference frequency of the reference clock CK_REF.

The digital macro <NUM> is arranged to perform at least one data processing function according to a first clock CK_1 with a first frequency. For example, the digital macro <NUM> may have a digital circuit such as an on-chip central processing unit (CPU) or an on-chip radar signal processor (RSP). As shown in <FIG>, another frequency processing circuit <NUM> is arranged to receive the reference clock CK_REF with the reference frequency different from the first frequency, generate the first clock CK_1 with the first frequency according to the reference clock CK_REF, and output the first clock CK_1 to the digital macro <NUM>. For example, the frequency processing circuit <NUM> may include a PLL circuit, a frequency multiplier circuit, and/or a frequency divider circuit, depending upon the discrepancy between the first frequency of the first clock CK_1 and the reference frequency of the reference clock CK_REF.

Moreover, the first clock CK_1 generated from the frequency processing circuit <NUM> may be output to an external device <NUM> that is located outside of the chip <NUM>. The external device <NUM> is coupled to the chip <NUM> via an interface <NUM> such as a UART (universal asynchronous receiver/transmitter) interface, an OWI (one-wire communication interface), a <NUM>-wire interface, an SPI (serial peripheral interface), an LIN (local interconnect network) bus, or a CAN (controller area network) bus. In other words, the on-chip digital macro <NUM> and the external device <NUM> can share the same first clock CK_1 output from the frequency processing circuit <NUM>. For example, the external device <NUM> may be a digital signal processor (DSP) device or a Flash memory device.

Compared to a reference clock generated from an off-chip crystal oscillator, a reference clock generated from an on-chip active oscillator may have less stability and accuracy. In this embodiment, the calibration circuit <NUM> is arranged to control the active oscillator <NUM> for calibrating the reference frequency of the reference clock CK_REF. The active oscillator <NUM> changes the reference frequency of the reference clock CK_REF in response to a control signal S_CTRL generated from the calibration circuit <NUM>. For example, the calibration circuit <NUM> is a self-calibration circuit that applies frequency calibration to the active oscillator <NUM> in response to frequency drift resulting from temperature variation.

In the embodiment shown in <FIG>, the reference frequency of the reference clock CK_REF generated from the active oscillator <NUM> is different from (e.g., higher than or lower than) the LO frequency needed by the front-end circuit <NUM>. Hence, the frequency processing circuit <NUM> is implemented to process the reference clock CK_REF for creating the LO signal S_LO with the needed LO frequency. However, this is for illustrative purposes only, and is not meant to be a limitation of the present invention. In an alternative design, the frequency processing circuit <NUM> can be omitted when the reference frequency of the reference clock CK_REF generated from the active oscillator <NUM> is equal to the LO frequency needed by the front-end circuit <NUM>.

<FIG> is a diagram illustrating a second wireless system according to an embodiment of the present invention. For example, the wireless system <NUM> may be a radar system such as an automotive radar system. For another example, the wireless system <NUM> may be a wireless communication system such as a Wi-Fi system. In this embodiment, the wireless system <NUM> is implemented on a chip <NUM>, and therefore has a plurality of on-chip components. The major difference between the wireless systems <NUM> and <NUM> is that the wireless system <NUM> has a direct path <NUM> connected between an output port of the active oscillator <NUM> and an input port of the front-end circuit <NUM>. Hence, the reference clock CK_REF with a reference frequency equal to an LO frequency is supplied to the front-end circuit <NUM> via the direct path <NUM>, such that the reference clock CK_REF received by the front-end circuit <NUM> acts as the LO signal S_LO directly.

In the embodiment shown in <FIG>, the reference frequency of the reference clock CK_REF generated from the active oscillator <NUM> is different from (e.g., higher than or lower than) the clock frequency needed by both of the digital macro <NUM> and the external device <NUM>. Hence, the frequency processing circuit <NUM> is implemented to process the reference clock CK_REF for creating the first clock CK_1 with the needed first frequency, where the same first clock CK_1 is shared by the on-chip digital macro <NUM> and the external device <NUM>. However, this is for illustrative purposes only, and is not meant to be a limitation of the present invention. In an alternative design, the clock frequency needed by the digital macro <NUM> and the clock frequency needed by the external device <NUM> are not necessarily the same. When the clock frequency needed by the digital macro <NUM> is different from (e.g., higher than or lower than) the clock frequency needed by the external device <NUM>, multiple frequency processing circuits may be used in a wireless system.

<FIG> is a diagram illustrating a third wireless system according to an embodiment of the present invention. For example, the wireless system <NUM> may be a radar system such as an automotive radar system. For another example, the wireless system <NUM> may be a wireless communication system such as a Wi-Fi system. In this embodiment, the wireless system <NUM> is implemented on a chip <NUM>, and therefore has a plurality of on-chip components. The major difference between the wireless systems <NUM> and <NUM> is that the wireless system <NUM> further includes a frequency processing circuit <NUM>, and the first clock CK_1 is not output to the external device <NUM>.

The frequency processing circuit <NUM> is arranged to receive the reference clock CK_REF with the reference frequency different from a second frequency (which may be different from the first frequency of the first clock CK_1), generate a second clock CK_2 with the second frequency according to the reference clock CK_REF, and output the second clock CK_2 to the external device <NUM> via the interface <NUM>. For example, the frequency processing circuit <NUM> may include a PLL circuit, a frequency multiplier circuit, and/or a frequency divider circuit, depending upon the discrepancy between the second frequency of the second clock CK_2 and the reference frequency of the reference clock CK_REF.

<FIG> is a diagram illustrating a fourth wireless system according to an embodiment of the present invention. For example, the wireless system <NUM> may be a radar system such as an automotive radar system. For another example, the wireless system <NUM> may be a wireless communication system such as a Wi-Fi system. In this embodiment, the wireless system <NUM> is implemented on a chip <NUM>, and therefore has a plurality of on-chip components. The major difference between the wireless systems <NUM> and <NUM> is that the wireless system <NUM> has a direct path <NUM> connected between an output port of the active oscillator <NUM> and an input port of the front-end circuit <NUM>. Hence, the reference clock CK_REF with a reference frequency equal to an LO frequency is supplied to the front-end circuit <NUM> via the direct path <NUM>, such that the reference clock CK_REF received by the front-end circuit <NUM> acts as the LO signal S_LO directly.

In some embodiments of the present invention, the frequency processing circuit <NUM> used in the wireless system <NUM>/<NUM> may be modified to generate a range of frequencies according to the reference frequency of the reference clock CK_REF and then select one frequency from the range of frequencies as the LO frequency. Selecting an accurate frequency from the range of frequencies can compensate for the drift of the reference frequency, either before or after the frequency calibration of the active oscillator <NUM>. In this way, the frequency regulation can be met.

As mentioned above, the calibration circuit <NUM> may be a self-calibration circuit that applies frequency calibration to the active oscillator <NUM>. However, this is for illustrative purposes only, and is not meant to be a limitation of the present invention. Alternatively, the frequency calibration of the active oscillator <NUM> may be based on an external source.

<FIG> is a diagram illustrating a fifth wireless system according to an embodiment of the present invention. For example, the wireless system <NUM> may be a radar system such as an automotive radar system. For another example, the wireless system <NUM> may be a wireless communication system such as a Wi-Fi system. In this embodiment, the wireless system <NUM> is implemented on a chip <NUM>, and therefore has a plurality of on-chip components. The major difference between the wireless systems <NUM> and <NUM> is that the wireless system <NUM> has a calibration circuit <NUM> that is arranged to receive an external reference clock CK_EXT from an external source device <NUM> located outside of the chip <NUM> and apply frequency calibration to the active oscillator <NUM> according to the external reference clock CK_EXT.

<FIG> is a diagram illustrating a sixth wireless system according to an embodiment of the present invention. For example, the wireless system <NUM> may be a radar system such as an automotive radar system. For another example, the wireless system <NUM> may be a wireless communication system such as a Wi-Fi system. In this embodiment, the wireless system <NUM> is implemented on a chip <NUM>, and therefore has a plurality of on-chip components. The major difference between the wireless systems <NUM> and <NUM> is that the wireless system <NUM> has the calibration circuit <NUM> that is arranged to receive the external reference clock CK_EXT from the external source device <NUM> located outside of the chip <NUM> and apply frequency calibration to the active oscillator <NUM> according to the external reference clock CK_EXT.

<FIG> is a diagram illustrating a seventh wireless system according to an embodiment of the present invention. For example, the wireless system <NUM> may be a radar system such as an automotive radar system. For another example, the wireless system <NUM> may be a wireless communication system such as a Wi-Fi system. In this embodiment, the wireless system <NUM> is implemented on a chip <NUM>, and therefore has a plurality of on-chip components. The major difference between the wireless systems <NUM> and <NUM> is that the wireless system <NUM> has the calibration circuit <NUM> that is arranged to receive the external reference clock CK_EXT from the external source device <NUM> located outside of the chip <NUM> and apply frequency calibration to the active oscillator <NUM> according to the external reference clock CK_EXT.

<FIG> is a diagram illustrating an eighth wireless system according to an embodiment of the present invention. For example, the wireless system <NUM> may be a radar system such as an automotive radar system. For another example, the wireless system <NUM> may be a wireless communication system such as a Wi-Fi system. In this embodiment, the wireless system <NUM> is implemented on a chip <NUM>, and therefore has a plurality of on-chip components. The major difference between the wireless systems <NUM> and <NUM> is that the wireless system <NUM> has the calibration circuit <NUM> that is arranged to receive the external reference clock CK_EXT from the external source device <NUM> located outside of the chip <NUM> and apply frequency calibration to the active oscillator <NUM> according to the external reference clock CK_EXT.

For example, when the wireless system <NUM>/<NUM>/<NUM>/<NUM> is an automotive radar system, the external source device <NUM> may be an electronic control unit (ECU). Hence, the calibration circuit <NUM> may receive an ECU reference clock from a defined interface, and may apply frequency calibration to the active oscillator <NUM> according to the ECU reference clock, where the frequency calibration may be real-time calibration or power-on calibration. In this way, clock alignment with the external ECU located outside of the chip <NUM>/<NUM>/<NUM>/<NUM> can be achieved. For another example, the external reference clock CK_EXT needed by frequency calibration of the active oscillator <NUM> may be extracted from a radio-frequency (RF) signal and then supplied by the external source device <NUM>.

Claim 1:
A wireless system (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>) comprising:
an active oscillator (<NUM>), arranged to generate and output a reference clock, wherein the active oscillator (<NUM>) comprises at least one active component, and does not include an electromechanical resonator;
a front-end circuit (<NUM>), arranged to process a transmit, TX, signal or a receive, RX, signal according to a local oscillator, LO, signal, by performing an up-conversion process that converts the TX signal from a lower frequency to a higher frequency for signal transmission,
and/or by performing a down-conversion process that converts the RX signal from a higher frequency to a lower frequency for signal reception, wherein the LO signal is derived from the reference clock; and
a calibration circuit coupled to the active oscillator and configured to control the active oscillator to calibrate the LO frequency of the reference clock;
wherein the reference clock with an LO frequency is supplied to the front-end circuit via a direct path (<NUM>, <NUM>), and the reference clock received by the front-end circuit acts as the LO signal directly.