Abstract: A wireless communication device (WCD) performs DC removal on a received signal using a coarse DC removal unit that removes relatively large DC components and a fine DC removal loop that removes residual DC components. The coarse DC removal unit can be implemented in a receiver, and the fine DC removal loop can be implemented in a modem. In addition, a coarse DC estimation loop implemented on the modem may be coupled to the coarse DC removal unit to update DC offset values stored in the DC removal unit. By storing coarse DC offset values locally on the receiver, DC removal can be achieved very quickly.

Abstract: Techniques for suppressing spurs in a receiver are described. A processor (e.g., within a wireless device) receives digital samples for a desired signal having a spur located within the bandwidth of the desired signal. A spur is an undesired signal that may be generated internally at the receiver or may come from an external interfering source. The processor filters the digital samples to suppress the spur and provides output samples having the spur suppressed. The processor may detect for the spur, e.g., by performing an FFT on the digital samples and examining the spectral response. The processor may filter the digital samples with a notch filter having an adjustable notch frequency and/or an adjustable notch bandwidth. For example, the notch frequency may be set based on the frequency of the spur, and the notch bandwidth may be set based on the amplitude of the spur.

Abstract: A wireless device achieves good performance using a crystal oscillator that is not compensated for temperature. The crystal oscillator provides a reference signal having a temperature dependent frequency error. A control unit estimates the frequency error (e.g., based on a received pilot) and provides a frequency error estimate. A clock generator generates a digital clock, which tracks chip timing, based on the reference signal and the frequency error estimate. A receiver frequency downconverts an input RF signal with a receive LO signal having the frequency error and provides an analog baseband signal. An ADC digitizes the analog baseband signal based on a sampling clock having the frequency error and provides ADC samples. A re-clocking circuit re-clocks the ADC samples based on a digital clock and provides data samples. A digital rotator frequency translates the data samples based on the frequency error estimate and provides frequency-translated samples centered near DC.

Abstract: An adaptive multi-channel (AMC) modem that can receive one or multiple spread spectrum signals simultaneously includes an adjustable filter, a ?? ADC, and a digital processor. The adjustable filter filters an input signal with an adjustable bandwidth and provides an output signal comprised of a selected number of spread spectrum signals. The ?? ADC digitizes the output signal and provides data samples. The sampling rate and/or the reference voltage of the ?? ADC may be varied to obtain the desired performance. The digital processor processes the data samples for each spread spectrum signal to recover data sent in that signal. A controller ascertains the operating conditions (e.g., the desired signal level, the undesired signal level, and so on) and selects the number of spread spectrum signals to receive based on the operating conditions, user requirements, and possibly other factors.

Abstract: A wireless device configured to support a wireless networking protocol may utilize signal processing techniques that can mitigate the effects of jammer signals. For example, when a measured power associated with a digital sample of a received wireless signal is greater than a threshold, the wireless device may determine if the wireless signal corresponds to a wireless networking packet to be demodulated. If the wireless signal does not correspond to a wireless networking packet to be demodulated, the wireless device may adjust the threshold so that the power associated with the digital sample is less than the threshold. In other words, if the signal is a jammer signal, the wireless device may adjust its noise floor upward so that continuous reception of the same jammer signal does not trigger demodulation a second time.

Abstract: A wireless communication device (WCD) implements an improved architecture for performing automatic gain control (AGC). For example, a WCD including a wireless receiver and a modem may incorporate a digital variable gain amplifier (DVGA) and an automatic gain control (AGC) unit that have the improved architecture. In particular, the architecture of the DVGA and AGC unit may be simplified and improved specifically for handling signals modulated according to a wireless networking standard such as one of the IEEE 802.11 standards.

Abstract: Transmitter architectures for a communications system having improved performance over conventional transmitter architectures. The improvements include a combination of the following: faster response time for the control signals, improved linearity, reduced interference, reduced power consumption, lower circuit complexity, and lower costs. For a cellular application, these improvements can lead to increased system capacity, smaller telephone size, increased talk and standby times, and greater acceptance of the product. Circuitry is provided to speed up the response time of a control signal. The control loop for various elements in the transmit signal path are integrated. A gain control mechanism allows for accurate adjustment of the output transmit power level. Control mechanisms are provided to power down the power amplifier, or the entire transmit signal path, when not needed.

Abstract: An apparatus for coarse compensation of a direct current (DC) offset in a direct to baseband receiver architecture utilizes a serial analog to digital converter (ADC), such as a Delta-Sigma converter, to convert the received signal to digital form. The output of the ADC is sampled for a predetermined number of samples and a counter coupled to the ADC is incremented each time the sample generated by the ADC is a logic one. The counter is not incremented if the sample from the ADC is a logic zero. After the predetermined number of samples is obtained, the counter value is indicative of the DC offset in the received signal. The counter value may be converted by a code converter to a correction value for easy operation of a digital to analog converter (DAC). If the number of samples from the ADC is a power of two, the code converted may be readily implemented by simply inverting the most significant bit (MSB) from the counter to thereby generate a twos complement version of the counter value.

Abstract: A novel and improved dielectric lens assembly (100) includes a dielectric extension (108) on a hemispherical dielectric lens (104), to provide a dielectric lens which exhibits properties of an elliptical lens. The extended dielectric lens can be implemented with a feed antenna (112) to improve the directivity of the antenna. The extension portion (108) of the lens assembly (100) is fabricated using a plurality of dielectric wafers disposed on the bottom surface of the hemisphere, an angled extension (516), or a cylindrical extension. The entire hemispherical lens and extension assembly (508) can be a single piece of dielectric material formed into the desired shape, or the assembly can be fabricated using a plurality of dielectric components (512, 516) coupled together to form the lens assembly.

Abstract: A bent-segment helical antenna utilizes one or more radiators wrapped in a helical fashion. The radiators are comprised of a plurality of segments. A first segment extends from a feed network at a first end of a radiator portion of the antenna toward a second end of the radiator portion. A second segment is adjacent to and offset from the first segment. A third segment connects the first and second segments at the second end of the radiator portion.

Abstract: A dual-band helical antenna provides operation in two frequency bands. The dual-band helical antenna includes two single-band antennas, each having a feed network, a ground plane opposite the feed network, and a set of one or more radiators extending from feed network. According to one aspect of the invention, a tab extends from the feed network of one of the antennas which provides a feed for that antenna. The tab also provides a path for current to flow from the radiators of the second antenna along the axis of the second antenna to thereby increase the energy radiated in the directions perpendicular to the axis. According to another feature of the invention, the ground plane of one antenna is used as a shorting ring for the other antenna.

Abstract: A coupled multi-segment helical antenna is provided having a length that is shorter than otherwise obtainable for a conventional half-wavelength antenna. The coupled multi-segment helical antenna includes radiator portion having a plurality of helically wound radiators extending from one end of the radiator portion to the other end of the radiator portion. Each radiator is made up of a set of two or more segments. A first segment extends in a helical fashion from the first end of the radiator portion toward the second end of the radiator portion. The second segment extends in a helical fashion from the second end of the radiator portion toward the first end of the radiator portion, wherein a portion of the first radiator segment is in proximity with a portion of the second radiator segment such that the first and second radiator segments are electromagnetically coupled to one another.

Abstract: A dual-band coupled-segment helical antenna provides operation in two frequency bands. The dual-band coupled-segment helical antenna includes a radiator portion having two sets of one or more helically wound radiators extending from one end of the radiator portion to the other end of the radiator portion. Radiators of the first set of radiators are comprised of two segments: a first radiator segment extends in a helical fashion from one end of the radiator portion toward the other end of the radiator portion; and a second radiator segment is U-shaped and extends in a helical fashion from the first end of the radiator portion toward the second end of the radiator portion. Radiators of the second set of radiators are comprised of a radiator disposed within said U-shaped segment. The first set of radiators resonates at a first frequency and the second set of radiators resonates at a second frequency thereby providing dual-band operation, with minimal coupling between the frequency bands.

Abstract: An receiver receives, amplifies, filters, and downconverts an RF signal to obtain an FM signal. The FM signal is then limited by a limiter and sampled by an ADC. The FM samples from the ADC are provided to an edge detector which detects transitions in the FM samples. The transitions correspond to zero crossings in the FM signal. The time period between the zero crossings, or the cycle width, is measured with a counter to determine the instantaneous frequency f.sub.c of the FM signal. The demodulated output is proportional to the instantaneous frequency which can be determined from the measured cycle periods as f.sub.c =1/2T.sub.c, f.sub.c .apprxeq.-.alpha.T.sub.c, or f.sub.c .varies.T.sub.c, where T.sub.c is the measured cycle period, and .alpha. is a constant based on the slope of 1/2T.sub.c,avg, where T.sub.c,avg is the average cycle period. The sample rate of the demodulated output can be reduced, through resampling, to minimize power consumption in the subsequent signal processing blocks.