Abstract: The present invention, generally speaking, provides a power-efficient method of driving a switch mode power supply at higher frequencies than those typically attainable in the prior art. In an exemplary embodiment, driver transistors exhibit gate capacitance, which is exploited by charging the gate capacitance using a pulse signal and thereafter allowing the gate capacitance to discharge. With the gate capacitance charged, the driver transistor remains on for the desired period of time even without a drive signal being continuously applied, thus conserving power. In essence, the gate capacitance is exploited in the manner of a memory cell. Furthermore, at higher-frequency operation, instead of the gate capacitance being fully charged, leading to increased turn-off time, the gate capacitance is only partially charged, allowing for quicker turn around. The envelope-following capability of the switch mode power supply, in telecommunications applications, is therefore increased.

Abstract: The present invention, generally speaking, provides for high-efficiency power control of a high-efficiency (e.g., hard-limiting or switch-mode) power amplifier. In one embodiment, the invention exploits the recognition that, for a constant-resistance circuit, power is equal to the square of the voltage across the circuit divided by the resistance of the circuit. In the case of certain switch mode amplifiers, such as Class E and Class F amplifiers, as well as saturated linear amplifiers, the amplifier may reasonably be regarded as having a constant resistance with varying power supply. In an exemplary embodiment, the supply voltage is controlled using a combination of two stages, a switch-mode converter stage that accomplishes gross power level control and a subsequent linear regulator stage that accomplishes more precise power envelope control, e.g., burst control.

Abstract: An apparatus (135), method and computer program are provided for determining and indicating a quality of a signal received by a first wireless communication device (105) from a second wireless communication device (110). In one embodiment, the apparatus (135) includes a bit-error-rate (BER) circuit (215) for measuring a BER of the signal, a comparator (145) for comparing the BER with a predetermined value to determine a relative signal quality, and an indicator (160) for indicating the quality of the signal to a user of the first device (105). Alternatively, the apparatus (135) includes a circuit for measuring the strength of the signal (230), a calculator (235) for calculating a signal-to-noise ratio (SNR) of the signal using the strength of the signal and a predetermined noise value, and a comparator (145) for comparing the SNR with a predetermined value to determine a relative signal quality.

Abstract: This invention controls and modulates switched-mode power amplifiers to enable the production of signals that include amplitude modulation (and possibly, but not necessarily, phase modulation), the average power of which may be controlled over a potentially wide range.

Abstract: Methods of and apparatus for digitally controlling, with sub-sample resolution, the relative timing of the magnitude and phase paths in a polar modulator. The timing resolution is limited by the dynamic range of the system as opposed to the sample rate. The methods and apparatus of the invention use a digital filter to approximate a sub-sample time delay. Various techniques for approximating a sub-sample time delay using digital signal processing may be used to achieve the approximation. Ideally, the filter will have an all-pass magnitude response and a linear phase response. In practice, the magnitude may be low-pass and the phase may not be perfectly linear. Such deviation from the ideal response will introduce some distortion. However, this distortion may be acceptably small depending on the particular signal being processed.

Abstract: The present invention, generally speaking, provides for high-efficiency power control of a high-efficiency (e.g., bard-limiting or switch-mode) power amplifier in such a manner as to achieve a desired control or modulation. Unlike the prior art, feedback is not required. That is, the amplifier may be controlled without continuous or frequent feedback adjustment. In one embodiment, the spread between a maximum frequency of the desired modulation and the operating frequency of a switch-mode DC-DC converter is reduced by following the switch-mode converter with an active linear regulator. The linear regulator is designed so as to control the operating voltage of the power amplifier with sufficient bandwidth to faithfully reproduce the desired amplitude modulation waveform. The linear regulator is further designed to reject variations on its input voltage even while the output voltage is changed in response to an applied control signal.

Abstract: Switchmode DC-DC power converters using one or more non-Silicon-based switching transistors and a Silicon-based (e.g. CMOS) controller are disclosed. The non-Silicon-based switching transistors may comprise, but are not necessarily limited to, III-V compound semiconductor devices such as gallium arsenide (GaAs) metal-semiconductor field effect transistors (MESFETS) or heterostructure FETs such as high electron mobility transistors (HEMTs). According to an embodiment of the invention, the low figure of merit (FoM), &tgr;FET, of the non-Silicon-based switching transistors allows the converters of the present invention to be employed in envelope tracking amplifier circuits of wireless devices designed for high-bandwidth technologies such as, for example, EDGE and UMTS, thereby improving the efficiency and battery saving capabilities of the wireless devices.

Abstract: The present invention, generally speaking, uses multiple selectable power supply paths, a saturation detector, or combinations of the same to achieve efficient power supply processing. In one aspect of the invention, a power supply processing circuit includes a first switched converter stage and a second linear stage. Depending on the power supply desired, the first stage may be bypassed to avoid conversion losses. In another aspect of the invention, a saturation detector is used to control the first stage such that the second stage operates efficiently just short of saturation, thereby avoiding distortion.

Abstract: Two fixed-phase-related signals of arbitrary (unequal) magnitude are combined without incurring combining loss by use of a signal reflection technique wherein the higher magnitude signal is phase-synchronously reinforced along its path through the combining system. In a specific embodiment, two signal sources are fed as equal phase signals through respective counter-rotating circulators to a four-port first combiner, wherein the first output port of the combiner is provided with a one-eighth wavelength phase delay to a termination and the second output port is directly terminated, so that reflected signals as seen at both input ports return exactly in phase and of equal magnitude to one another. Thereupon the reflected signals are directed by the respective circulators as phase-synchronized signals to a second combiner which combines the phase synchronized signals into a common output signal. The resultant output is the sum of the inputs irrespective of relative magnitudes of the inputs.

Abstract: A system and method of amplitude modulation is described in which first and second 180 degrees out-of-phase signals are produced and are each amplified by one of two (different amplification factor) non-linear amplifiers. One of the signals is amplified using constant amplification by a first non-linear amplifier to generate a relatively small amplified signal. The other of the signals is modulated using variable amplification by a second non-linear amplifier to generate a relatively larger amplitude modulated signal. The two resulting 180 degree out-of-phase signals are combined, such that the smaller signal effectively cancels out lower level distortion exhibited by the larger amplitude modulated signal. Alternatively, a symmetrical structure can be used for generating AM signals which include phase reversals of the carrier.

Abstract: This invention controls and modulates switched-mode power amplifiers to enable the production of signals that include amplitude modulation (and possibly, but not necessarily, phase modulation), the average power of which may be controlled over a potentially wide range.

Abstract: The present invention, generally speaking, achieves a highly efficient line driver for high crest-factor signals such as DMT/ADSL signals. In an exemplary embodiment, a digital signal produced by a digital signal processor or the like is processed by a sigma-delta modulator (SDM) to produce one or more binary signal pairs. The signals of a signal pair are low-pass filtered, if necessary, and applied across the winding of a transformer. The transformer has a single secondary winding connected to the line and may has as many primary windings as the number of signal pairs. The transformer may have a unity turns ratio or may have a turns ratio for accomplishing voltage step-up. For one signal pair, the number of possible resulting signals levels on the secondary side is three, for two signal pairs five, etc. Using more than two signal levels, it becomes possible to recreate from the digital signals the corresponding analog waveform with the required accuracy.

Abstract: The present invention, generally speaking, provides a method and apparatus for accurately measuring a communications signal. In accordance with one aspect of the invention, DC offset effects and nonlinearities attributable to a communications amplifier are made spectrally separable from DC offset effects and nonlinearities attributable to the measurement apparatus. Spectral separability may be accomplished, for example, by adding an offset frequency to a local oscillator used by a downconverter of the measurement apparatus. As a result, the signal of interest is moved away from baseband (zero frequency) to the offset frequency. Similarly, other nonlinearities in the video amplifier (such as third order distortion) manifest theselves mostly at harmonics of the offset frequency. Hence spectral separability between the power amplifier characteristics and these nonlinear impairments of the measurement system is achieved.

Abstract: The present invention, generally speaking, satisfies the foregoing requirements using in combination within a frequency synthesis loop an SDM-based synthesizer and an SDM-based frequency digitizer. Since both blocks are SDM-based, the resulting signals can be differenced and filtered to produce a control signal for an oscillator. Low noise (and low spurs), fine frequency resolution and fast switching times may all be achieved simultaneously.

Abstract: The present invention, generally speaking, provides a highly efficient RF power amplifier having a large output dynamic range. The amplifier avoid the large power dissipation that occurs in the LINC combiner at lower output levels. In general, this is achieved by using power-controlled switch-mode power amplifiers to vary output power at large power outputs, and reverting to LINC only at low output powers. Thus the present invention achieves the desirable combination of high efficiency at all output powers, while maintaining the fine output power control of the LINC method. More particularly, the power amplifier is based on a highly efficient structure in which amplitude modulation/power control of the output of an RF amplifier is achieved by operating the amplifier in switch mode and varying the power supply of the amplifier, as described more fully in U.S. patent application Ser. No. 09/637,269 entitled High-Efficiency Modulating RF Amplifier, filed Aug. 10, 2000 and incorporated herein by reference.

Abstract: The present invention, generally speaking, provides a controlled oscillator that attains the foregoing objectives. The structure of the oscillator is, in general, that of a ring; however, timing of the oscillator is governed largely by an RC time constant. Since the delay is mostly RC-based, phase noise is minimal compared to an active implementation. Furthermore, in a preferred embodiment, two ring oscillators of this type are combined to form a differential oscillator circuit having still lower phase noise. In an exemplary embodiment, the ring oscillators are three-stage ring oscillators. The operation of two inverters is unaffected by the RC time constant. Because the speed of these inverters is very fast compared to the RC time constant, the oscillation frequency is quite constant versus temperature and supply voltage.

Abstract: A first amplified signal is produced at a first amplifier, a second amplified signal is produced at a second amplifier, and a differential signal representing difference between the first amplified signal and the second amplified signal is generated at a subtraction unit receiving the first amplified signal and second amplified signal, the differential signal being a final amplified signal having a final modulated amplitude and a final modulated phase.

Abstract: A system and method of modulation is described that initially over-modulates with an information signal at a scale that is N times an intended modulation scale and then subsequently, frequency-divides the over-modulated signal by the same factor of N to generate a modulated signal having the intended modulation scale wherein distortion of the resulting modulated signal is reduced by a factor of 20 log10(N)dB.

Abstract: The present invention, generally speaking, provides for high-efficiency power control of a high-efficiency (e.g., hard-limiting or switch-mode) power amplifier in such a manner as to achieve a desired control or modulation. Unlike the prior art, feedback is not required. That is, the amplifier may be controlled without continuous or frequent feedback adjustment. In one embodiment, the spread between a maximum frequency of the desired modulation and the operating frequency of a switch-mode DC-DC converter is reduced by following the switch-mode converter with an active linear regulator. The linear regulator is designed so as to control the operating voltage of the power amplifier with sufficient band-width to faithfully reproduce the desired amplitude modulation waveform. The linear regulator is further designed to reject variations on its input voltage even while the output voltage is changed in response to an applied control signal.

Abstract: Two fixed-phase-related signals of arbitrary (unequal) magnitude are combined without incurring combining loss by use of a signal reflection technique wherein the higher magnitude signal is phase-synchronously reinforced along its path through the combining system. In a specific embodiment, two signal sources are fed as equal phase signals through respective counter-rotating circulators to a four-port first combiner, wherein the first output port of the combiner is provided with a one-eighth wavelength phase delay to a termination and the second output port is directly terminated, so that reflected signals as seen at both input ports return exactly in phase and of equal magnitude to one another. Thereupon the reflected signals are directed by the respective circulators as phase-synchronized signals to a second combiner which combines the phase synchronized signals into a common output signal. The resultant output is the sum of the inputs irrespective of relative magnitudes of the inputs.