Abstract:
A half-duplex mobile terminal having first and second receiver branches connected, during a receive mode, to respective antennas, is disclosed. One of the antennas is selectively connected to the first receiver branch or to a transmitter circuit. The first antenna is connected to the first receiver branch during a first interval, during which interval data is detected using outputs from both the first and second receiver branches. The first antenna is disconnected from the first receiver branch at the end of the first interval, and, during a second interval immediately following the first interval, data is detected using the output of the second receiver branch. A portion of the incoming transmission that arrives during the transition between the receive mode and transmit mode in a half-duplex transceiver is thus received and detected, improving performance of the half-duplex transceiver.
Abstract:
A modulation circuit for use in a radiofrequency transmitter includes a local oscillator circuit configured to generate one or more local oscillator signals at a desired frequency and with a duty cycle at or about twenty-five percent, and a modulator configured to generate one or more modulated signals responsive to the one or more local oscillator signals and one or more baseband information signals. In at least one embodiment, the modulation circuit includes a modulator comprising a combined mixing and transconductance circuit that includes a transistor circuit for each baseband information signal serving as a modulation input to the modulator. Each transistor circuit comprises a first transistor driven by the baseband information signal and coupling a modulator output node to a corresponding transconductance element, and a second transistor driven by one of the one or more local oscillator signals and coupling the corresponding transconductance element to a signal ground node.
Abstract:
Circuits and methods are disclosed for compensating for received signal distortion caused by non-linearities in wideband receivers. An exemplary receiver includes a distortion waveform generator configured to approximate non-linear response characteristics of a downconverter circuit used to downconvert the received radio frequency signal. The resulting estimated distortion waveform is filtered, using filter(s) substantially similar to those used for filtering an intermediate frequency signal that includes the desired signal and non-linear distortion products caused by strong interfering signals. The filtered estimated distortion waveform and intermediate frequency signal are sampled, to obtain a sampled distortion signal and a sampled signal of interest. The sampled distortion signal and the sampled signal of interest are divided into a plurality of frequency channels. For a selected number of frequency channels, the sampled distortion signal for a frequency channel is scaled, and subtracted from the corresponding sampled signal of interest for the same frequency channel to obtain reduced-interference signal samples for the frequency channel.
Abstract:
Methods and apparatus are disclosed for automatically adjusting antenna impedance match in a wireless transceiver employing phase-amplitude modulation. According to some embodiments of the invention, a wireless transceiver comprises a transmitter circuit and a receiver circuit connected to the antenna by a transmit/receive duplexer. An electronically adjustable matching network is located between the transmitter output and the antenna. To control the adjustable matching network, a directional coupler is located between the transmitter output and the matching network to separate transmit signals reflected from the antenna system, including the antenna, the matching network and the T/R duplexer. The reflected transmit signals are routed to the receiver circuit, which digitizes the reflected signal and determines an antenna reflection coefficient based on the digitized reflected signal and the modulation signal used to create the transmit signal. The complex antenna reflection coefficient is used to determine any adjustment needed to the antenna matching network.
Abstract:
A modulation circuit for use in a radiofrequency transmitter includes a local oscillator circuit configured to generate one or more local oscillator signals at a desired frequency and with a duty cycle at or about twenty-five percent, and a modulator configured to generate one or more modulated signals responsive to the one or more local oscillator signals and one or more baseband information signals. In at least one embodiment, the modulation circuit includes a modulator comprising a combined mixing and transconductance circuit that includes a transistor circuit for each baseband information signal serving as a modulation input to the modulator. Each transistor circuit comprises a first transistor driven by the baseband information signal and coupling a modulator output node to a corresponding transconductance element, and a second transistor driven by one of the one or more local oscillator signals and coupling the corresponding transconductance element to a signal ground node.
Abstract:
A method and apparatus for minimizing harmonic content in a digital signal driver circuit are disclosed. A digital input signal applied to an input node generates a corresponding digital output in a circuit with two or more MOS devices in cascode connection with each other. The slew rate of leading or trailing edge transitions associated with the output signal are controlled using one or more parasitic capacitances associated with the fabrication of two or cascode connected MOS devices. The two or more cascode connected MOS devices may further each have gate electrodes connected to a fixed potential so as to minimize the harmonic content. A control signal may further be applied to each gate electrode to turn off a leakage current path between source and drain electrodes. Harmonics may further be controlled by limiting a conductance between gate electrodes and fixed potentials using an active or passive device.
Abstract:
A method and apparatus for frequency synthesis in a transceiver are based on providing a primary frequency synthesizer configured to synthesize a receiver frequency signal from a receiver reference frequency signal, and providing an offset frequency synthesizer configured to synthesize a transmitter frequency signal from the receiver frequency signal using fractional-N division, which allows it to operate at an intermediate frequency that is a non-integer multiple of the receiver frequency signal. That arrangement enables non-integer duplex frequency distances between desired receive and transmit frequencies. The primary frequency synthesizer also may be operated as a fractional-N frequency synthesizer, meaning that the receiver frequency signal may have a non-integer relationship to the receiver reference frequency signal. Configuring the primary and offset frequency synthesizers to operate with fractional-N frequency synthesis allows independent frequency tuning/optimization of the primary and secondary frequency synthesizers.
Abstract:
An entire radio transceiver can be completely integrated into one IC chip. In order to integrate the IF filters on the chip, a heterodyne architecture with a low IF is used. A single, directly modulated VCO is used for both up-conversion during transmission, and down-conversion during reception. Bond-wires are used as resonators in the oscillator tank for the VCO. A TDD scheme is used in the air interface to eliminate cross-talk or leakage. A Gaussian-shaped binary FSK modulation scheme is used to provide a number of other implementation advantages.
Abstract:
A dual-radio communication apparatus has a first radio device, such as a Bluetooth radio, for use in a first frequency band, and a second radio device, such as a Globalstar satellite radio, for use in a second frequency band, which is proximate to the first frequency band. The communication apparatus also has a controller coupled to the first and second radio devices. The first radio device may comprise a frequency-hopping spread-spectrum transmitter. Moreover, the first radio device has a first operating mode employing a first frequency range. The first radio device also has a second operating mode employing a second frequency range, which is smaller than the first frequency range. The controller is adapted to set the first radio device in its second operating mode, when the second radio device is in operation, and otherwise set the first radio device in its first operating mode.
Abstract:
A method and apparatus for minimizing harmonic content in a digital signal driver circuit are disclosed. A digital input signal applied to an input node generates a corresponding digital output in a circuit with two or more MOS devices in cascode connection with each other. The slew rate of leading or trailing edge transitions associated with the output signal are controlled using one or more parasitic capacitances associated with the fabrication of two or cascode connected MOS devices. The two or more cascode connected MOS devices may further each have gate electrodes connected to a fixed potential so as to minimize the harmonic content. A control signal may further be applied to each gate electrode to turn off a leakage current path between source and drain electrodes. Harmonics may further be controlled by limiting a conductance between gate electrodes and fixed potentials using an active or passive device.