Miscellaneous active electrical nonlinear devices – circuits – and – Signal converting – shaping – or generating – Phase shift by less than period of input
Reexamination Certificate
2003-01-17
2004-09-14
Callahan, Timothy P. (Department: 2816)
Miscellaneous active electrical nonlinear devices, circuits, and
Signal converting, shaping, or generating
Phase shift by less than period of input
C327S361000
Reexamination Certificate
active
06791388
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to data transceivers.
2. Background Art
A communication device including a transmitter and a receiver is known as a transceiver. Known transceivers can transmit and receive data signals. There are demands on such transceivers to transmit and receive such data signals with low error rates and at ever increasing data rates, to reduce power dissipation, cost, and size. Therefore, there is a general need for a transceiver capable of satisfying such demands.
It is desirable to integrate transceiver circuits on an integrated circuit (IC) chip to reduce size and power dissipation of the transceiver. The circuits on the IC chip typically operate in accordance with timing signals. However, oscillators used to generate such timing signals have disadvantages, including typically large sizes, high power dissipation, and deleterious electromagnetic radiative properties (that is, the oscillators tend to radiate electromagnetic interference across the IC chip). Also, oscillators used in communication devices often need to be tunable in both phase and frequency and in response to rapidly changing signals. This requires complex oscillator circuitry. Moreover, multiple oscillators on a common IC chip are subjected to undesired phenomena, such as phase and/or frequency injection locking, whereby one oscillator can deleteriously influence the operation of another oscillator.
Therefore, there is a general need to integrate transceiver circuits on an IC chip. There is a related need to reduce the number and complexity of oscillators constructed on the IC chip, to thereby avoid or substantially reduce all of the above-mentioned disadvantages associated with such oscillators.
To reliably process a received data signal, a receiver typically needs to match its operating characteristics with the characteristics of the received data signal. For example, in the case of baseband data transmissions, the receiver can derive a sampling signal, and then use the sampling signal to sample the received data signal at sample times that produce optimal data recovery. In this way, data recovery errors can be minimized.
Precision timing control techniques are required to achieve and maintain such optimal sampling times, especially when the received data signals have high data rates, such as multi-gigabit-per-second data rates. Such timing control includes control of the phase and frequency of a sampling signal used to sample the received data signal.
As the received data signal rate increases into the multi-gigabit-per-second range, the difficulty in effectively controlling sampling processes in the receiver (such as controlling phase and frequency characteristics of the sampling signal) correspondingly increases. For example, semiconductor circuits, such as complementary metal oxide semiconductor (CMOS) circuits, are often unable to operate at sufficiently high frequencies to optimally control the sampling processes. For example, it becomes increasingly difficult at such high received signal data rates to provide sufficiently short time delays usable for controlling sampling phases of the sampling signal.
Accordingly, there is a need for systems and techniques in a data receiver that provide effective sampling of high data rate signals. There is a related need to reduce the number of circuit components required to provide such effective data signal sampling, thereby reducing cost, size, and power dissipation in the data receiver.
BRIEF SUMMARY OF THE INVENTION
I. Phase Interpolator
The present invention is directed to a phase interpolation system. The phase interpolation system includes a stage controller adapted to produce a plurality of stage control signals, and a plurality of reference stages that are each adapted to convert one of a plurality of reference signals into a corresponding component signal. Each reference stage performs this conversion in response to a respective one of the stage control signals. Each of the component signals has a distinct phase that is determined by the corresponding reference signal phase.
The phase interpolation system also includes a combining node that is adapted to combine (e.g., sum) the component signals into an output signal having an interpolated phase.
Each of the plurality of reference stages may include a conversion module and one or more scaling modules. The conversion module is adapted to convert the corresponding reference signal into the corresponding component signal according to a scaling factor. The one or more scaling modules are adapted to adjust the scaling factor in response to a value of the corresponding stage control signal.
Each of the stage control signals may include a plurality of binary control subsignals. In this embodiment, the value of each stage control signal is the sum of the corresponding binary control signals. Each of these subsignals may be received by one of a plurality of scaling modules. As a result, the scaling factor of the respective reference stage increases with the value of the corresponding stage control signal.
In a specific implementation, four reference stages are each adapted to convert one of four reference signals into a corresponding component signal in response to a respective one of the stage control signals. These four reference signals each have one of four phases that are separated at substantially 90 degrees intervals.
The conversion module of each reference stage may include a transconductance device, such as a field effect transistor (FET).
The output signal as well as each of the reference and component signals may be differential signals.
The stage controller may be a phase control signal rotator adapted to adjust the plurality stage control signals such that the output signal is phase aligned with a serial data signal.
Without the use of conventional techniques, such as time-delays, the phase interpolator advantageously provides output signal phases that span a complete rotation of 360 degrees.
II. Timing Recovery System
A receiver of the present invention includes a timing recovery system to recover timing information from a received serial data signal. The receiver uses such recovered timing information to compensate for frequency and phase offsets that can occur between the received serial data signal and a receiver sampling signal used to sample the serial data signal. The timing recovery module of the present invention recovers/extracts phase and frequency information from the received serial data signal. The timing recovery module derives the sampling signal using the phase and frequency information. The timing recovery module phase aligns and frequency synchronizes the sampling signal with the serial data signal to enable the receiver to optimally sample the serial data signal.
The timing recovery system of the present invention includes a phase interpolator. The phase interpolator derives a sampling signal having an interpolated phase in response to 1) phase control inputs derived by the timing recovery system, and 2) a set of reference signals derived from a master timing signal. The timing recovery system causes the interpolator to align the interpolated phase of the sampling signal with the serial data signal phase. In addition, the timing recovery system can cause the interpolator to rotate the interpolated phase of the sampling signal at a controlled rate to synchronize the sampling signal frequency to the serial data signal frequency.
The present invention advantageously simplifies a master oscillator used to generate the master timing signal (mentioned above) because the phase interpolator, not the oscillator, tunes the phase and frequency of the sampling signal. In other words, the master oscillator need not include complex phase and frequency tuning circuitry, since the need for such functionality is met using the timing recovery system. Additionally, multiple, independent timing recovery systems can operate off of a single, common master timing signal, and thus, a single master oscillator. This advantag
Baumer Howard A.
Buchwald Aaron W.
Jiang Xicheng
Le Michael
Madisetti Avanindra
Broadcom Corporation
Callahan Timothy P.
Cox Cassandra
Sterne Kessler Goldstein & Fox PLLC
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