1731 results about "Local oscillator signal" patented technology

A millimeter wave pulsed radar system includes a radar synthesizer having a voltage controlled oscillator/phase locked loop (VCO/PLL) circuit, direct digital synthesizer (DDS) circuit and quadrature modulator circuit that are operative to generate an intermediate frequency local oscillator signal (IF/LO signal). A radar transceiver is operative with the radar synthesizer for receiving the IF/LO signal. A transmitter section has a frequency multiplier that multiplies the IF/LO signal up to a millimeter wave (MMW) radar signal and a receiver section and includes a direct conversion mixer that receives a MMW radar signal and the IF/LO signal to produce I/Q baseband signals that are later digitized and processed.

The present invention is related to methods and apparatus that compensate for quadrature impairments of an analog quadrature modulator and/or demodulator over a relatively wide signal bandwidth. One embodiment pre-distorts baseband signals in a quadrature modulator compensation signal processor (QMCSP) to negate the quadrature impairment of an analog quadrature modulator and corrects a received baseband signal in a quadrature demodulator compensation signal processor (QDCSP) to cancel the quadrature impairment of an analog quadrature demodulator. The QMCSP and the QDCSP contain adaptive digital filter correction structures that pre-compensate and post-compensate, respectively, for the quadrature impairments introduced by the analog quadrature modulator and the analog quadrature demodulator over a relatively wide bandwidth. A phase shifter advantageously shifts the phase of a local oscillator signal to the analog quadrature demodulator to distinguish quadrature impairments introduced by the modulation path from quadrature impairments introduced by the demodulation path.

A receiver for a digital beamforming radar system includes a plurality of antenna elements, low-noise block converters, one or more analog-to-digital converters, and a processor. The antenna elements receive a radar signal and output a received signal. The low-noise block converters are modified commercially available components used in satellite television systems, respond to the received signal from a corresponding antenna element, and output an intermediate frequency signal. The low-noise block converters include at least one amplifier, a mixer, and a local oscillator input. The local oscillator input enables an external local oscillator signal to be inputted to the mixer. The analog-to-digital converters are responsive to the intermediate frequency signal of a corresponding low-noise block converter. The processor is responsive to the digital signals output by the analog-to-digital converters.

A radio frequency (RF) demodulation circuit comprising a harmonic rejection mixing stage capable of receiving and mixing an incoming radio frequency (RF) signal having a frequency RF and a reference local oscillator (LO) signal having a frequency LO and generating an output signal in which out-of-band harmonic signals are suppressed. The harmonic rejection mixing stage comprises 1) a multiphase local oscillator (LO) generator for receiving the reference LO signal and generating M phase-shifted local oscillator signals having frequencies LO and 2) M mixers, each of the M mixers receiving the incoming radio frequency signal and one of the M phase-shifted local oscillator signals. Each of the M mixers generates a subcomponent signal. The subcomponent signals are then scaled and combined to produce the output signal.

An optical mixer that, in one embodiment, has a single optical hybrid optically coupled to a single polarization beam splitter. The optical hybrid mixes a polarization-multiplexed optical communication signal and a local-oscillator signal to generate four mixed signals, each corresponding to a different relative phase shift between the communication and local-oscillator signals. The polarization beam splitter separates each of the mixed signals into two polarization components, subsequent processing of which enables an optical receiver employing the optical mixer to recover the data carried by the communication signal.

In a frequency modulation radio receiver with direct conversion, a local oscillator signal is generated having a frequency within a preselected frequency range and the frequency is varied in response to a variable low frequency signal; the local oscillator signal is mixed with a received signal to provide a baseband signal. The variable low frequency signal is generated by a controlled oscillator in inverse relationship to a direct current component in said baseband signal. In a frequency modulation radio transceiver a broadcast function is provided by varying the low frequency signal with an information signal with the resulting local oscillator frequency being varied accordingly and amplified for broadcast. The transceiver is controlled to operate alternately in either a receive mode and a broadcast mode at substantially the same frequency. While in the receive mode the controlled oscillator causes the local oscillator signal to be drawn toward the carrier frequency of a received signal yielding preferred direct conversion of modulating information into the base band.

A technique to share a local oscillator signal between two radio frequency integrated circuits (RFICs). The local oscillator signal generated internally by one RFIC is ported to the other RFIC for use in transmit and/or receive operation. The local oscillator signal that is ported may be an RF local oscillator signal. Each RFIC may include a bi-directional port circuit that can be operated to make the RFIC a master, slave or may be totally disabled to disable the porting feature. This is particularly useful in RFICs that are used to communicate using MIMO radio algorithms which rely for optimum performance on phase and frequency coherency among a plurality of transmitters and a plurality of receivers.

An N-phase radio receiver front-end for converting an input signal having a first frequency to output signals having a second frequency, and a method for converting an input signal in an N-phase radio receiver front-end. An input port of the N-phase radio receiver front-end is directly connected to an input port of a low noise amplifier (50). A mixer arrangement (50a) is a current mode mixer arrangement. An output port of the low-noise amplifier is directly connected to an input port of the mixer arrangement. A signal generator operatively connected to the mixer arrangement is adapted to generate N phase shifted local oscillator signals.

An electromagnetic transmission and reception system comprises a transmitter section and a receiver section. The transmitter section has a first signal source, a second signal source at a lower frequency than the first signal source, and means for generating from the first and second signal sources a plurality of signals with fixed frequency spacing derived from the second signal source frequency. One or more pairs of the plurality of signals are selected, and for the or each pair, the signals of the pair are combined to derive an output signal having a frequency derived from the difference between the frequencies of the signals of the pair. The receiver section combines a received signal, which comprises a received version of the output signal, with a local oscillator signal for frequency down-conversion of the received signal. This local oscillator signal is generated by the transmitter section. This provides a system in which the generation of signals of the desired frequency is achieved by mixing signals of specific frequencies. The reception uses frequency down-conversion using the same signal sources as used for the transmission. This enables a low noise system to be implemented.

A receiver circuit includes an oscillator circuit configured to generate a calibration tone and a phase locked loop (PLL) reference signal. An output frequency of the VCO may be divided by respective amounts to derive a desired calibration tone frequency and a desired PLL reference signal frequency. In addition to the oscillator circuit, the receiver circuit may further include a phase locked circuit configured to generate a PLL output signal that is phase locked in relation to the PLL reference signal. During a calibration mode, a quadrature generator may be used to generate quadrature mixer local oscillator signals dependent upon the PLL output signal, and an in-phase/quadrature mixer may be used to mix the calibration tone with the quadrature mixer LO signals.

A lightweight millimeter wave outdoor unit includes a lightweight housing with a heat sink and mounting member configured for mounting on the antenna to form a wireless link. A millimeter wave transceiver board is formed of ceramic material and mounted within the housing. It includes a millimeter wave transceiver circuit that has microwave monolithic integrated circuit (MMIC) chips and operable with the transmit and receive boards. An intermediate frequency (IF) board has components forming an intermediate frequency circuit operable with the millimeter wave transceiver circuit. A frequency synthesizer board has a signal generating circuit for generating local oscillator signals to the transceiver circuit. A controller board has surface mounted DC and low frequency discrete devices thereon forming power and control circuits that supply respective power and control signals to other circuits on other boards. A quick connect/disconnect assembly is operative with the housing for allowing the housing to be rapidly connected and disconnected to the antenna circuit contact members interconnect circuits between boards.

The present invention is a quadrature VLIF receiver, including calibration circuitry, and methods to closely match signal processing of an in-phase signal path and a quadrature-phase signal path to optimize VLIF image rejection. The calibration circuitry includes a variable gain variable-phase calibration signal generator, a variable gain amplifier for each signal path, phase adjustment circuitry for each signal path, and switching circuitry to support calibration steps. The calibration signal generator supplies a calibration signal at the same frequency as mixer local oscillator signals; therefore, during calibration, all signals downstream of the VLIF mixer are at DC, which simplifies calibration measurements, thereby minimizing calibration times.

Ensuring that a tunable device, such as a tunable optical filter, accurately tracks the wavelength of a local oscillator signal involves generating at least one synchronization signal as the local oscillator signal is swept across a range of wavelengths and adjusting an operating characteristic of the tunable device in response to the at least one synchronization signal. Before the local oscillator signal is swept across the range of wavelengths, the operating characteristic of the tunable device and the wavelength of the local oscillator signal are initially set to matching values.

A receiver (1100) includes a direct digital frequency synthesizer (130), a mixer (105), and a clock source (1110, 1130). The direct digital frequency synthesizer has an input terminal for receiving a first clock signal at a first frequency, and an output terminal for providing a digital local oscillator signal synchronously with the first clock signal. The mixer (105) has a first input terminal for receiving a radio frequency (RF) signal, a second input terminal coupled to the output terminal of the direct digital frequency synthesizer (130), and an output terminal for providing an IF signal having a spectrum centered about a selectable one of a plurality of center frequencies. The clock source (1110, 1130) has an output terminal for providing the first clock signal without using any harmonic frequency that overlaps the spectrum for any of the plurality of center frequencies.

Receiver architectures and methods of processing harmonic rich input signals employing harmonic suppression mixers are disclosed herein. The disclosed receivers, mixers, and methods enable a receiver to achieve the advantages of switching mixers while greatly reducing the mixer response to the undesired harmonics. A harmonic mixer can include a plurality of mixers coupled to an input signal. A plurality of phases of a local oscillator signal can be generated from a single local oscillator output. Each of the phases can be used to drive an input of one of the mixers. The mixer outputs can be combined to generate a frequency converted output that has harmonic rejection.

A circuit module for a phased array (10) incorporates radio frequency (RF) mixers (54a, 54b) connected to an RF splitter/combiner (52) and to in-phase and quadrature RF reference signals. The RF mixers (54a, 54b) are also connected to intermediate frequency (IF) processing circuitry (60 to 68) providing for phase control of RF signals and IF reference signals. In transmission mode, the RF mixer (54a, 54b) receive phase-controlled, digitally synthesised IF signals from clock-activated generators (68a, 68b). Their outputs are combined at the RF splitter/combiner (52) to provide single sideband upconversion of the phase-controlled IF signals. In reception mode, the RF splitter/combiner (52) and the RF mixers (54a, 54b) act as an image rejection mixer circuit in which the phase-controlled IF signals are local oscillator signals. Beamforming is carried out by computer control of the IF phase together with, in the case of reception, analogue or digital summation of output signals from an array of modules (12).

PCT No. PCT/GB95/01607 Sec. 371 Date Dec. 10, 1997 Sec. 102(e) Date Dec. 10, 1997 PCT Filed Jul. 7, 1995 PCT Pub. No. WO97/03367 PCT Pub. Date Jan. 30, 1997A circuit module for a phased array radar (10) incorporates radar frequency (RF) mixers (54a, 54b) connected to an RF splitter/combiner (52) and to in-phase and quadrature RF reference signals. The RF mixers (54a, 54b) are also connected to intermediate frequency (IF) processing circuitry (60 to 68) providing for phase control of RF signals and IF reference signals. In transmission mode, the RF mixer (54a, 54b) receive phase-controlled, digitally synthesised IF signals from clock-activated generators (68a, 68b). Their outputs are combined at the RF splitter/combiner (52) to provide single sideband upconversion of the phase-controlled IF signals. In reception mode, the RF splitter/combiner (52) and the RF mixers (54a, 54b) act as an image rejection mixer circuit in which the phase-controlled IF signals are local oscillator signals. Beamforming is carried out by computer control of the IF phase together with, in the case of reception, analogue or digital summation of output signals from an array of modules (12).

An OFDM transceiver has a transmitter, a receiver, and a loopback switch. The loopback switch configured is for selectively establishing a physical connection between an output terminal of the transmitter and an input terminal of the receiver. The transmitter is configured for outputting to the output terminal an OFDM signal generated based on a local oscillator signal. The receiver is configured for demodulating the OFDM signal, received via the physical connection, using the local oscillator signal and determining amplitude and phase imbalance parameters based on performing frequency-domain estimation of amplitude and phase imbalances. Hence, the receiver is configured for performing imbalance compensation on a received wireless OFDM signal based on the determined amplitude and phase imbalance parameters. Hence, amplitude and phase imbalances can be estimated accurately despite channel fading and frequency variations encountered between the transmitter of the wireless OFDM signal and the receiver.

A receiver (200) includes a transconductance mixer (310), a polyphase filter (320), and a transimpedance amplifier (330). The transconductance mixer (310) mixes a radio frequency (RF) voltage signal into a current signal having a plurality of phases using a local oscillator signal. The polyphase filter (320) filters the current signal to provide a filtered current signal. The transimpedance amplifier (330) converts the filtered current signal into an output voltage signal.