Abstract: Radio receivers are known in the art. A conventional receiver requires external components for RF/image selectivity, IF selectivity and demodulation. Other solutions are, for example, a number of correction algorithms, which is an expensive solution. Instead, the “weak” image point is positioned at the side of the desired channel with the lowest unwanted RF signal strength. While this does not necessarily increase the actual image rejection, the perceived image rejection is clearly improved.

Abstract: An architecture for a multiple-band wireless transceiver with quadrature conversion receiver and transmitter circuits. Dual dedicated local oscillators provide the necessary frequency up and down conversion signals for the transmitter and receiver circuits, respectively, thereby allowing for duplex transmit and receive operations. Each of the transmitter and receiver circuits include multiple, e.g., three, signal paths for providing multiple-band operation. In the transmitter, the outgoing baseband data is quadrature modulated. The modulated data signals are then frequency up converted using another quadrature signal mixing process which avoids any need for image signal rejection filters within the signal transmission path. Similarly, in the receiver, quadrature signal mixing is used for the frequency down conversion process, thereby avoiding any need for image signal rejection filters within the signal reception path.

Abstract: In a system and method for simultaneously receiving or switching between dual frequency carrier signals in a GPS receiver, the GPS receiver is adapted to utilize different harmonics of a sub-harmonic frequency generator, which may include a lower frequency voltage controlled oscillator (VCO) to detect the L1 and L2 GPS carriers. A sub-harmonic mixer may be used to simultaneously down convert the L1 and L2 signals to a lower intermediate frequency (IF). A second mixer may be an image reject (IR) mixer used to separate the downconverted L1 and L2 signals. This mixer may be configured to simultaneously monitor the L1 and L2 signals, or to switch between the L1 and L2 signals. High frequency switching is not required of the radio frequency (RF) input or local oscillator signals, and simultaneous L1 and L2 reception is enabled without a 3dB image noise degradation.

Abstract: A communications receiver includes a baseband signal recovery circuit which uses a low-IF architecture for data reception. The baseband signal recovery circuit uses a full-analog implementation for channel selection and filtering. Thus, the overhead placed on the design of analog-to-digital converter is greatly relaxed and most of hardware can be re-used for multi-mode applications with only a slight modification.

Abstract: A method and system is described for several embodiments of a communication system. In a first embodiment, a method and system is described wherein a signal is received and down-converted and wherein power consumption can be characterized as “ultra-low.” In a second embodiment, a method and system is described wherein undesirable images are rejected in a down-conversion system. In a third embodiment, a method and system is described wherein a signal is transmitted in a highly efficient manner. In one implementation the present invention is used in a family radio system.

Abstract: An RF mixer circuit having reduced intermodulation products includes a cascode transconductance amplifier including a first transistor having a control electrode connected to receive an input signal and serially connected with a second transistor having a control electrode connected to receive a bias potential. A balanced mixer is coupled to the second transistor by a first inductive element for receiving an amplified input signal current, and receiving a local oscillator signal and producing an output signal with an intermediate frequency related to the frequencies of the amplifier input signal and the local oscillator. A feedback circuit is provided from the second transistor to the control electrode of the first transistor including a resistor serially connected with a capacitor, whereby the feedback circuit compensates for signal phase shift by the inductive element.

Abstract: With the rising popularity in wireless personal communication systems (PCS), there is a need for low-power, low-cost radio receivers. Low cost can be achieved by integrating the required functions as much as possible, thus minimizing the number of off-chip components. The present invention discloses a novel topology for integrating an image reject filter with a traditional low-noise amplifier (LNA) for use in the front-end of a superheterodyne receiver. Previous topologies employing additional filter stages after the LNA have suffered from poor performance and excessive current consumption. Advantageously, the topology of the present invention requires minimal additional circuitry to perform the filtering function, uses only minimal additional current and does not suffer from the same performance limitations as previous topologies.

Abstract: A system for receiving a transmitted signal is provided. The system includes a first receiver that can receive the transmitted signal and decode the transmitted signal according to a first demodulation format, such as a CDMA or PCS format. A second receiver, such as an FM demodulator, is connected to the first receiver at a suitable location, such as after initial signal amplification and processing has been completed. The second receiver can decode the transmitted signal according to a second demodulation format, such as AMPS.

Abstract: An image reject mixer arrangement 1 comprises a transconductor 2, first and second mixer cores 3 and 4, first and second phase shifters 5 and 6 and a summer or combiner 7. The mixer arrangement 1 receives a single-ended RF voltage signal on a terminal 8, a differential local oscillator signal on I-LO terminals indicated at 9 and a 90° phase shifted differential local oscillator signal on Q-LO terminals 10, and provides differential IF output signals on output terminals 11. From the output of the transconductor 2 to the output of the combiner 7, the image reject mixer arrangement 1 carries signals in what can be described as a “current mode”, i.e. it is the current, not the voltage, which conveys the desired signal. In this current mode, it is advantageous to provide each active circuit block with a high output impedance and a low input impedance wherever possible.

Abstract: A tuner includes a tunable filter for selecting a desired RF signal in response to a tuning control signal and a tunable image trap for rejecting the undesired image signal corresponding to the desired RF signal responsive to the tuning control signal coupled in cascade between an RF amplifier and a mixer. The tunable trap also serves as an impedance transformation element between the tunable filter and said mixer. The arrangement is particularly useful in a tuner in which the frequency range of the local oscillator signal is below the frequency range of the received RF signals.

Abstract: In an image-rejection receiver having a first frequency conversion stage (1, 2, 9) having a pair of frequency mixers (1,2) each supplied external radio frequency signal (RF) and first local frequency signal (LOCAL1) with quadrature phase relations (9), a second frequency conversion stage (3-6, 10) having two pairs of frequency mixers (3-4, 5-6) at each output of each first stage mixer and second local frequency signal (LOCAL2) with quadrature phase relations (10), and an adder (7) and a subtractor (8) for providing sum and difference of amplitude of outputs of said second frequency conversion stage to provide inphase component (BBI) and quadrature-phase component (BBQ), no filter is used for removing an undesirable image signal which is generated in frequency conversion. A control circuit (11) is provided to keep accurate quadrature phase relations for said first local frequency signal, and said second local frequency signal, by measuring D.C. component of a product of outputs of two of mixers.

Abstract: Alignment methods and apparatus for I/Q phase and amplitude error correction and image rejection improvement that may be used at the time of circuit fabrication or on chip for use during operation. The alignment method may be used to improve the I/Q phase and amplitude accuracy of a direct conversion transceiver or to improve image rejection in an up or downconversion mixer. For alignment purposes, a pilot tone of a selected frequency is used to provide a calibration reference, with adjustments being made in phase and amplitude to drive the I and Q phase and amplitude mismatch toward a minimum.

Abstract: A multi-carrier receiver selects antennas (A31, A32), i.e. carriers whereto a small amount of power and data is allocated, for estimation of characteristics of a narrowband disturber (RFI-Signal-3) in the Radio Frequency Interference band (RFI-Band), a predetermined band for e.g. radio amateur transmission. These antennas (A31, A32) can be selected amongst all carriers located inside the Radio Frequency Interference band (RFI-Band) and at least two carriers (C1, C2) located outside the Radio Frequency Interference band (RFI-Band).

Abstract: A surface acoustic wave includes a surface acoustic wave element including a piezoelectric substrate having IDTs, input/output terminals, and reference potential terminals provided thereon and a package enclosing the surface acoustic element and having electrode lands and external terminals. The resonance frequency of the resonator defined by inductances generated by the reference potential terminals of the external terminals of the package, is positioned in the vicinity of an image frequency occurring at a time of performing frequency conversion in a super heterodyne system.

Abstract: A radio-frequency (RF) front-end is described. In one embodiment, the RF front-end comprises a low noise amplifier (LNA), a first mixer and an I/Q quadrature mixer. The LNA amplifies a received signal at a carrier frequency, the LNA having inductive loads. The first mixer is coupled to the low noise amplifier and mixes an amplified received signal with a first local oscillator (LO) signal to down convert the amplified received signal to an intermediate frequency (IF). The first mixer has inductive loads. The first frequency is related to the carrier frequency such that an image channel associated with the carrier and the LO frequency is outside the bandwidth of the inductive loads of the LNA. The I/Q quadrature mixer stage has a second mixer and a third mixer coupled to the first mixer. The I/Q quadrature mixer converts the amplified received signal at the IF to I and Q signals using a second LO signal related to the first LO signal.

Abstract: An image reject mixer for a radio receiver comprises transconductors 21 and 22, mixer stages 30 and 23 and a phase shift and combiner circuit 26. The transconductors 21 and 22 provide differential output current signals to their respective mixer stage 30 and 23. Capacitors 28 and 29 are connected between equivalent outputs of the transconductors 21 and 22 respectively. The capacitors 28 and 29 have the effect of correlating the output noise of the transconductors 21 and 22 and correlating the noise generated by the mixer stage transistors which is leaked to the inputs of the mixer stages 30 and 23, the image frequency components of which noise are thereby cancelled by the operation of the mixer stages 30 and 23 and the phase shift and combiner circuit 26. The capacitors 28 and 29 also compensate the second harmonic of the local oscillators which leak through to the inputs of the mixer stages 30 and 23. Overall, gain, noise figure and linearity can all be improved without an increase in current consumption.

Abstract: Radio receivers are known in the art. A conventional receiver requires external components for RF/image selectivity, IF selectivity and demodulation. Other solutions are for example a number of correction algorithms, which is an expensive solution.

Abstract: An object of the present invention is to lower the power dissipation of the image rejection mixer. The image rejection mixer includes distribution means supplied with local signals having a phase difference to distribute the local signals, first and second mixing means for mixing the distributed local signals and RF signals having a phase difference and outputting respective IF current signals, phase shift means for shifting in phase the respective mixed IF current signals so as to provide them with a relative phase difference of 90 degrees, and addition means for adding the respective phase shifted intermediate frequency current signals. The phase shift means shifts the phases of the respective IF current signals outputted from the first and second mixing means.

Abstract: A radio apparatus comprises a local oscillation signal generator which includes a first local oscillation unit for generating a first local oscillation signal having a frequency f.sub.LO1 to be divided into third and fourth local oscillation signals having a phase difference of 90 degrees and a second local oscillation unit for generating a second local oscillation signal having a frequency f.sub.LO2 to be divided into fifth and sixth local oscillation signals having a phase difference of 90 degrees. The local oscillation signal generator includes an arithmetic unit for adding or subtracting the multiplication result of the third and fifth local oscillation signals and the multiplication result of the fourth and sixth local oscillation signals to obtain a local oscillation signal from which an image signal is removed.

Abstract: An image rejection circuit (10) receives an incoming signal (RF.sub.IN) and an oscillator signal (V.sub.OSC) generated by a local oscillator (26). Output signals (I.sub.OUT20 and I.sub.OUT40) are generated by first mixer circuits (14 and 34) by multiplying the incoming signal (RF.sub.IN) with the oscillator signal (V.sub.OSC) Second mixer circuits (24 and 44) multiply the output signals (I.sub.OUT20 and I.sub.OUT40) with a counter signal that is a divided oscillator signal (V.sub.OSC). A summing circuit (46) sums the signals generated by the second mixer circuits (24 and 44) and provides a signal (IF.sub.OUT). Phase shift circuits (22, 29, 31, and 42) provide a shifted oscillator signal (V.sub.OSC) and a shifted counter signal to the first and second mixer circuits (14, 24, 34, and 44) that cause cancellation of unwanted image signals in the signal (IF.sub.OUT).

Abstract: The wireless receiver band is divided into a plurality of smaller bands using a tunable duplexer to produce a first IF signal of a much lower frequency enabling better unwanted signal filtering using a filter of a certain Q.

Abstract: The device forms first and second signals by mixing the input radio signal with two respective quadrature waves of frequency f.sub.O. An algebraic sum of these two signals is phase-shifted by .+-.45.degree. or .+-.135.degree. at an intermediate frequency f.sub.I. An output signal is formed by an algebraic sum between the phase-shifted signal and the first or second signal, in such a way that, at the intermediate frequency f.sub.I, the output signal has a phase representative of that possessed by the input radio signal at a communication frequency f.sub.C of the form f.sub.O -f.sub.I or f.sub.O +f.sub.I, with rejection of the phase of the input radio signal at the image frequency 2f.sub.O -f.sub.C.

Abstract: A synchronous tracking filter circuit for use in a broadcast satellite tuner that comprises four varactors and a strip-shaped inductor plate or pcb-printed strip line which produces a resonant frequency. The circuit is used in a doubly tuned resonant circuit to incorporate the tracking with the frequency changes of a voltage controlled oscillator (VCO) synchronously. The circuit can also control the image interference. This type of design is applicable in the tuner of an indoor broadcast satellite receiver unit to act as the synchronous tracking filter of input frequencies.

Abstract: In a device for rejecting the image signal of a signal converted to a predetermined intermediate frequency, a local oscillator supplies a local signal at a frequency chosen according to the frequency of the signal and the intermediate frequency. A first phase-shifter has two passive phase-shifter cells including resistive and capacitive components and respectively connected to the output of the oscillator to supply two mixer signals in phase quadrature. Two mixers receive an input signal containing a signal and its image signal and a respective mixer signal and supply two intermediate signals at the intermediate frequency. A second phase-shifter comprises two passive phase-shifter cells comprising resistive and capacitive components and respectively connected to the outputs of the two mixers to introduce a further phase quadrature relationship between the two intermediate signals.

Abstract: A radio receiver in which the received signal is spread and subsequently despread in order to identify unwanted signals. One embodiment of the present invention is comprised of a frequency-hopping spreading synthesizer that operates in synchronization with a despreader synthesizer such that unwanted signals are effectively suppressed based upon different spreading characteristics of the desired and undesired signals. Use of a logic device, in one case a digital signal processor, in combination with a state-level monitor allows for the reconfiguring of the receiver such that a state containing a large interferer can be removed from further signal processing.

Abstract: A tunable/switchable notch filter adapted for use in the front end of a television receiver removes an image frequency on the low side of the UHF passband without degrading desired frequencies. The tunable/switchable notch filter can be switched out when in a VHF mode so as not to degrade VHF performance and switched in for UHF operation for filtering out a difference image frequency which varies with and is a predetermined frequency less than the desired UHF signal.

Abstract: A tunable notch filter for the front end of an RF receiver includes magnetically coupled input and output tunable stages each responsive to a tuning voltage provided thereto. Each of the input and output stages includes a respective series and parallel resonant circuit wherein the parallel resonant circuits are tuned to a selected RF frequency and the series resonant circuits are tuned to a frequency approximately equal to that of a local oscillator. By using the series resonant circuits to create a notch at a frequency approximating that of the local oscillator, conducted local oscillator leakage from the receiver's antenna is substantially reduced and local oscillator image frequency rejection is substantially improved.

Abstract: In a superheterodyne receiver, such as a typical television receiver, a radio frequency coupling arrangement includes a first resonant circuit coupled to receive the input signal and further coupled to a second resonant circuit by a first coupling. Both resonant circuits are tuned to the desired signal frequency. The capacitive branch of the first resonant circuit includes a circuit impedance for providing a neutralizing voltage, at least a portion of which is coupled by a second coupling to the inductive branch of the second resonant circuit. The circuit impedance is selected to cause cancellation in the inductive branch between image frequency components coupled by the first coupling and image frequency components coupled by the second coupling, without substantially affecting the desired signals.

Abstract: The invention is a high frequency hetrodyne receiver front end for receiving a communications signal comprising a desired information frequency and an undesired image frequency. The receiver comprises a bandpass filter, a preamplifier responsive to the bandpass filter, a mixer and a coupler means between the preamplifier and the bandpass filter. The coupler means defines a reactive short at the undesired image frequency due to impedance characteristics of the coupler means. The coupler means thereby eliminates the image frequency noise at the input of the preamplifier. Preferrably the coupler means is a transmission line of a length L where L equals .eta..pi./.beta. and .eta. is an integer and .beta. is proportional to the wavelength of the image frequency.

Abstract: The local oscillator frequency in a communication tuning system is selected to either high side mix or low side mix as appropriate to place the local oscillator frequency and image frequency outside the bandpass range of the bandpass filter. This allows bandpass filters having a frequency range equal to approximately twice the IF frequency in a transmitter, and approximately four times the IF frequency in a receiver.