Abstract: FM radio transmitter is being widely used in portable devices as a convenient way to output audio contents to ubiquitously available FM radio receivers in cars or homes. However, the signal from the FM radio transmitter may be interfering with the signal being broadcast by an FM radio station. A scan system is incorporated into the FM radio transmitter to quickly and reliably identify a vacant channel for the FM radio transmitter to use. The scan system measures on-channel and out-of-channel signal quality and selects a best channel for transmission based on the measured on-channel and out-of-channel signal quality. The scan system is also incorporated into an FM radio receiver to quickly and reliably tune to a valid channel. The scan system selects the valid channel based on the measured on-channel and out-of-channel signal quality.

Abstract: A method of the present invention includes coordinating tuning to the same channel of a radio band wherein the following steps are performed: tuning to a channel, within a radio band, that uses a side band; receiving control information in the side band of the channel; and processing the received audio information in the channel using the control information.

Abstract: In an embodiment of the present invention, a clock generator circuit is disclosed to include a phase locked loop (PLL) that is responsive to a reference frequency and operative to generate a single clock frequency and a clock signal quadrature output frequency and a clock signal in-phase output with the frequency of the clock signal quadrature output frequency and the clock signal in-phase output frequency being a fraction of the frequency of the single clock frequency. The PLL includes a single voltage controlled oscillator (VCO) that generates the single clock frequency. A plurality of dividers is included in the clock generator circuit and is responsive to the clock signal quadrature output frequency and the clock signal in-phase output frequency and generates multiple clock frequencies, each clock frequency being a unique frequency, each of the plurality of dividers generating an output, the final output of the plurality of dividers being synchronized to the reference frequency.

Abstract: A device and method of duplex audio communication over a broadcast channel are disclosed. The device and method disclosed in the present invention use the clear channel technique to automatically select an un-occupied channel for the transmit side and utilizes an identification embedded in a sub-channel to allow the receiver to automatically tune to the channel used by the transmitter. The clear channels may be determined by respective transceivers or determined by a master transceiver.

Abstract: A scan system receives signals within a band from an antenna and divides the band into sub-bands and scans the channels of each sub-band to determine a candidate channel based on the lowest figure of merit (FOM) and includes an on-channel selection block responsive to a received digital signal and operative to select only the on-channel frequencies and to substantially disregard the out-of-channel frequencies from the digital signal. The scan system generates a FOM on-channel signal representing a measurement of the signal quality of the on-channel signal and includes an out-of-channel selection block responsive to the digital signal and operative to select only the out-of-channel frequencies and to substantially disregard the on-channel frequencies from the digital signal and operative to generate a FOM out-of-channel signal representing a measurement of the signal quality of the out-of-channel signal.

Abstract: A device and method of duplex audio communication over a broadcast channel are disclosed. Low-power transmission over a broadcast channel is permissible for personal use as long as the transmitted power level is below a level allowed by respective regulatory. For example, low-power FM transmitter can be used to provide a wireless audio link between two audio devices. One such application scenario is a wireless speakerphone used as an audio extension from a cellphone for group conference purposes. Such applications face issues of potential interference from other users of the same channel and the need of manually selecting and tuning a pair of channels. The device and method disclosed in the present invention use the clear channel technique to automatically select an un-occupied channel for the transmit side and utilizes an identification embedded in a sub-channel to allow the receiver to automatically tune to the channel used by the transmitter.

Abstract: Apparatus and methods for removing dc offsets in feedback loops such as may be used in communication circuits are disclosed. A comparator may be used to sample the output of the feedback loop, with the comparator output applied to a DSP module. The DSP module is configured to determine a dc offset in the output signal and generate an offset correction signal, which may then be applied to the input of the feedback loop to adjust the de offset.

Abstract: Apparatus and methods for providing transmit signals in polar transmitters are described. A modulation signal may be provided from a VCO to low noise and low power signal paths and selectively combined based on a desired output power level. CMOS and CML divider circuits may be used to implement the low noise and low power signal paths respectively, and logic may be provided to select desired signals from the low noise and low power signal stages based on the desired output power level.

Abstract: Systems and methods of clock generation for radio frequency receiver. In radio frequency receiver, the system requires accurate local oscillating (LO) signal and system clocks for proper operation and to ensure high quality performance. In order to achieve accurate LO frequency and system clock, a crystal or and accurate reference clock is provide to the clock generation circuit. How a low-cost receiver, it is desirable to eliminate the requirement for a crystal or an accurate reference clock. The present invention discloses systems and methods to utilize a pilot signal embedded in the transmitted signal. The pilot signal usually has very accurate frequency which is particular true for broadcast system such as FM broadcast. In various embodiments of the present invention, the systems and methods measure the relation between the frequency of the pilot signal and the current clock generated.

Abstract: Systems of clock generation for integrated radio frequency receiver. In an integrated radio frequency receiver, a mixer is often used to down convert the incoming radio frequency signal. The down converted signal is then digitized and digital signal processing circuitry is used for efficient and flexible implementation of various functions to receive the underlying audio and/or data information. The mixer requires clock generation circuitry to provide a proper local oscillator signal for a selected channel. On the other hand, the digital signal processing circuitry requires its separate digital clock for proper operations. The clock generation system utilizes single local oscillator generation circuitry to provide the local oscillator signals required by the mixer and the digital clock signals required by the digital signal processing circuitry.

Abstract: FM radio transmitter is being widely used in portable devices as a convenient way to output audio contents to ubiquitously available FM radio receivers in cars or homes. However, the signal from the FM radio transmitter may be interfering with the signal being broadcast by an FM radio station. A scan system is incorporated into the FM radio transmitter to quickly and reliably identify a vacant channel for the FM radio transmitter to use. The scan system measures on-channel and out-of-channel signal quality and selects a best channel for transmission based on the measured on-channel and out-of-channel signal quality. The scan system is also incorporated into an FM radio receiver to quickly and reliably tune to a valid channel. The scan system selects the valid channel based on the measured on-channel and out-of-channel signal quality.

Abstract: An LNA circuit for providing a wide range of gain while maintaining the output headroom. In a radio frequency (RF) receiver, the signal received by the receiver may be extremely small. For a transmitter in a short distance, the received signal may be relatively strong. A low power amplifier usually is used to amplify the input signal. The LNA has to be designed to accommodate a wide range of gain. A convention LNA circuit supporting a wide range of gain often suffers from reduced output headroom due to increased current through the load resistor. The present invention discloses the use of current bleeding branch to allow a portion of current to flow through the current bleeding branch and consequently reduces the current that would have flown through the load resistor. Consequently, the voltage across the load resistor may be maintained low to allow adequate output headroom.

Abstract: FM radio transmitter is being widely used in portable devices as a convenient way to output audio contents to ubiquitously available FM radio receivers in cars or homes. However, the signal from the FM radio transmitter may be interfering with the signal being broadcast by an FM radio station. A scan system is incorporated into the FM radio transmitter to quickly and reliably identify a vacant channel for the FM radio transmitter to use. The scan system measures on-channel and out-of-channel signal quality and selects a best channel for transmission based on the measured on-channel and out-of-channel signal quality. The scan system is also incorporated into an FM radio receiver to quickly and reliably tune to a valid channel. The scan system selects the valid channel based on the measured on-channel and out-of-channel signal quality.

Abstract: A system and method of clock generation to provide divided-by-2 clocks with prescribed phase shifts are disclosed. In a communication system with high-order harmonic mixing, the system requires LO signals with a set of prescribed phase shifts, such as 0°, 45°, 90°, and 135°, or 0°, 60° and 120°. Often, the clock generation system involves a divide-by-2 divider to derive the clock signals with the prescribed phase shifts. In a conventional implementation of the divide-by-2 divider, the system is subject to phase uncertainty in the output signal. Accordingly, a system comprises multiple latch pairs and respective differential clocks are used to generate the clocks with the set of correct prescribed phase shifts.

Abstract: A system and method for sharing a switched capacitor array (SCA) by two tuning circuits are disclosed. In a multiple-band radio receiver, there is a need to use multiple tuning circuits for signals in different bands. The tuning circuit typically comprised an adjustable capacitance device and other tuning components, where the adjustable capacitance device is often implemented in SCA. The present invention discloses a system and method comprising n sections of capacitor elements where each capacitor element comprises a capacitor and switches to selectively connect the capacitor to one of the tuning circuit. Consequently, the SCA can be shared by the two tuning circuits. The control bits for the switched may be provided from a programmable control register.

Abstract: A system and method for signal mixing using high-order harmonics of a local oscillation (LO) signal. In a radio frequency (RF) system, the input RF signal is converted to a lower frequency signal such as an intermediate frequency (IF) signal or a baseband signal for further processing. A voltage controlled oscillator (VCO) is often used to generate a VCO signal which is then divided down to provide the needed LO signals for down conversion. The present invention discloses a system and method for generating a composite harmonic signal based on a linear combination of divided down LO signals with specific phase shifts. Consequently a VCO signal with lower frequency can be used to conserve power. The composite harmonic signal is mixed with the input RF signal to generate a series of mixed signal including one associated with a high-order harmonic of the divided down LO signal.

Abstract: Apparatus and methods for improving the spectral performance of a polar modulator are described. A composite FM signal component of a composite polar transmit signal may be processed by monitoring the FM signal to detect a transient burst component, and, responsive to detection of a transient burst, generating a spectrally friendly replacement signal component that may be combined with the FM signal to improve spectral performance of the composite signal. In addition, an associated AM component of the composite transmit signal may be filtered to further improve spectral performance.

Abstract: A device and method of duplex audio communication over a broadcast channel are disclosed. Low-power transmission over a broadcast channel is permissible for personal use as long as the transmitted power level is below a level allowed by respective regulatory. For example, low-power FM transmitter can be used to provide a wireless audio link between two audio devices. One such application scenario is a wireless speakerphone used as an audio extension from a cellphone for group conference purposes. Such applications face issues of potential interference from other users of the same channel and the need of manually selecting and tuning a pair of channels. The device and method disclosed in the present invention use the clear channel technique to automatically select an un-occupied channel for the transmit side and utilizes an identification embedded in a sub-channel to allow the receiver to automatically tune to the channel used by the transmitter.

Abstract: Apparatus and methods for adjustment of spectral signal characteristics in polar modulators are described. A composite signal detection circuit is configured to detect when a signal trajectory of a composite signal provided to the polar modulator passes near the origin of a complex plane associated with the composite signal, and then adjusts the composite signal to pass through the origin. A spectral adjustment circuit is described to adjust AM and FM or PM components of the composite signal to reduce the deviation of an FM component of the composite signal.

Abstract: In a communication system, the signal received or transmitted is required to be maintained within a range for proper operation. For example, a radio frequency signal received from an antenna is usually amplified by a low-noise amplifier (LNA) with adjustable gain. The input RF signal is properly amplified by the LNA further processing by subsequently receive path of the receiver. A peak detector may be used to detect the peak amplitude of the amplified input and provides a proper gain for the LNA. The detected peak amplitude may be affected by the noises which may inadvertently cause the gain control to fluctuate randomly. In order to avoid the above issues, some hysteresis has to be built into the peak detection so that the gain control will not be so sensitive to the noise. The present invention discloses a system and method for peak detection with accurate hysteresis.