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 receiver for rejecting an image signal is provided that does not require a phase-shifter and that requires less mixers than prior receivers. Thus, the phase imbalances and gain mismatches imparted by phase shifters are avoided, and harmonics due to non-liner effects in the mixers are reduced.

Abstract: In a communications receiver for quadrature demodulation, a feedback technique for reducing the image response of the receiver. The communications receiver includes an I demodulator and a Q demodulator. A local oscillator (LO) signal is provided by a PLL to a quadrature LO generator that provides an LO_I signal to an I demodulator and an LO_Q signal to a Q demodulator. The LO_I and LO_Q signals are amplitude and phase-controlled versions of the LO signal. An image/signal ratio (I/S) detector detects the relative phase difference and the relative amplitude difference between the respective output terminals of the I demodulator and the Q demodulator and applies an amplitude control signal and a phase control signal to corresponding amplitude control and phase control inputs of the quadrature LO generator. The I/S detector calibrates the quadrature LO generator during the interstitial interval between the reception of data packets.

Abstract: A Radio Frequency (RF) receiver includes a low noise amplifier (LNA) and a mixer coupled to the output of the LNA. The gain of the LNA is adjusted to maximize signal-to-noise ratio of the mixer and to force the mixer to operate well within its linear region when an intermodulation interference component is present. The RF receiver includes a first received signal strength indicator (RSSI_A) coupled to the output of the mixer that measures the strength of the wideband signal at that point. A second received signal strength indicator (RSSI_B) couples after the BPF and measures the strength of the narrowband signal. The LNA gain is set based upon these signal strengths. By altering the gain of the LNA by one step and measuring the difference between a prior RSSI_B reading and a subsequent RSSI_B′ reading will indicate whether intermodulation interference is present.

Abstract: A method and apparatus for performing image rejection filtering in a radio signal processing device. In a specific example of implementation, the apparatus is a radio transceiver that includes a transmitter and a receiver, each comprising an image rejection filter. A control signal, already available in the usual radio transceiver architecture, is used to simultaneously tune the LO frequency of the transceiver and the image rejection frequency of the image rejection filters. The image rejection filters are designed such that their image reject frequency accurately tracks the Local Oscillator (LO) frequency of the transceiver over a range of frequencies.

Abstract: An image reject receiver is provided. The image reject receiver includes a first type low-intermediate frequency receiver, a zero-intermediate frequency receiver and a second low-intermediate frequency receiver. The first type low-intermediate frequency receiver is used for receiving image signal and transferring the image signal into a mirrored image signal with a frequency used in the first low-intermediate frequency receiver. The mirrored image signal is sent to the zero-intermediate frequency receiver and is suppressed to a zero frequency. The signal with the zero frequency is outputted to the second low-intermediate frequency receiver and is then transferred to be with the second intermediate frequency for easily demodulating in the following operation.

Abstract: A superhet receiver in which an input signal is frequency down-converted in a first mixer (14) to produce a first IF signal comprising a wanted channel signal and an image channel signal. The first IF signal, without image rejection filtering, is frequency down-converted in a second mixer (24) to produce a second, lower IF signal comprising at least the wanted channel signal having a bandwidth corresponding to a predetermined passband of a channel filter (32) coupled to the output of the second mixer. The local oscillator signals used in the first and second frequency down conversion processes are varied in order to produce successively different image channel signals in the first IF signal and to maintain the wanted channel signal in the second IF signal within the passband of the channel filter (32).

Abstract: To overcome problems in an image reject mixer in a radio frequency receiver when there is a degradation in image rejection due to process variations, such as variations in the values of components, a reactance feedback path of a first differential amplifier in the intermediate frequency combiner of the image reject mixer is tuned during assembly of the radio frequency receiver. This tuning places the first differential amplifier and a second differential amplifier in the intermediate frequency combiner in phase quadrature when the pole frequency of reactance feedback path is at least ten times lower than the frequency of the intermediate frequency and sets the gain of the two differential amplifiers to be equal when the reactance of the reactance feed back path in the first differential amplifier is equal to the resistance of a resistance feedback path in second differential amplifier.

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: An image rejection mixer includes first and second mixers, a phase shift circuit and a summer. The first mixer receives an RF input signal and a first local oscillator (LO) signal and generates a first intermediate frequency (IF) output signal. The second mixer receives the RF input signal and a second LO signal and generates a second IF output signal. The first LO signal is a phase lag signal (sin &ohgr;lot) and the second LO signal is a phase lead signal (−cos &ohgr;lot), where &ohgr;lot is a frequency signal generated by a local oscillator. The phase shift circuit is connected between the summer and the first mixer, receives the first IF output signal and generates a phase lag signal. The phase shift circuit causes the phase lag signal to lag the first IF output signal by about 90 degrees. The summer is connected to the phase shift circuit and the second mixer, receives the second IF output signal and the phase lag signal, and generates a combined IF output signal.

Abstract: A commutating image-reject mixer includes first and second branches, each having first and second stage mixers for converting the frequency of a desired channel to an intermediate frequency (IF) and rejecting the image channel. The local oscillator (LO) ports of all the mixers are commutated between quadrature and in-phase LO signals, and the output of the branches are commutated between each other, by two complementary, 50% duty cycle clock signals. The commutating image-reject mixer exhibits improved immunity to amplitude and phase mismatches that may be present in each branch.

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 method and apparatus for determining a delay vector from inputs of in-phase and quadrature phase low pass filters to an output of the demodulator of a dual mixer radio receiver and from such delay measurement computing and providing DC offset correction to said receiver.

Abstract: An input trap circuit removes a predetermined frequency component included in an input signal and then outputs the input signal to a circuit at a later stage. The input trap circuit is provided with: a parallel oscillation circuit in which a pair of variable capacitance diodes are connected in series such that cathodes thereof are connected to each other at a junction portion and in which an inductance is connected in parallel to the variable capacitance diodes between anodes of the variable capacitance diodes at both ends thereof; a voltage applying device for applying a voltage to the junction portion so as to vary capacitance values of the variable capacitance diodes on the basis of reverse voltage characteristics of the variable capacitance diodes respectively; and a variable capacitor element connected between the junction portion and a ground.

Abstract: A feed forward power amplifier system and method identify active channels across a frequency band to suppress unwanted intermodulation distortion (IMD) products in a communications signal such as a single- or multi-carrier communications signal. A scanning receiver identifies at least one active channel in a frequency band, and identifies at least one portion of the frequency band likely to include IMD products based upon the identified active channel(s). Based upon the identified portion of the frequency band, IMD products are suppressed from the communications signal, e.g., by controlling the magnitude and/or phase of a suppression signal mixed with the communications signal.

Abstract: A radio receiver of the is provided with a local oscillation circuit, a mixing circuit to perform a frequency conversion from a received signal into an intermediate frequency signal by using an oscillation signal generated by the oscillation circuit, an ALC circuit to detect a level of the oscillation signal and control the level of the oscillation signal at a specified value, and a switching circuit switch the operation of the ALC circuit from the operational state to the non-operational state and vice versa. The receiver thus constructed will not receive an influence from the image signal, and even when the receiver is used in an area where a strong interference wave is present, the receiver is able to operate the local oscillation circuit in a normal condition.

Abstract: This invention is a method of carrier suppression tuning of a wireless communication device (100) utilizing a quadrature modulator (104) in a transmission path (102). A power detector (128) and a processor (132) are coupled to the ends of the transmission path (102) to provide feedback to the quadrature modulator (104) and, thus, minimizes carrier feedthrough. For this invention, the transmission path (102) of the device (100) is enabled and “I” and “Q” DC offset values are set to default values. Then, output voltages from the power detector (128) are sampled and the “I” DC offset value is adjusted based on the sampled voltages. Similarly, output voltages from the power detector (128) are sampled and the “Q” DC offset value is adjusted based on the sampled voltages.

Abstract: A passive bandpass tracking filter tracks the frequency of an RF input signal received within a radio receiver's tracking range of RF frequencies. The bandpass filter includes parallel inductor and capacitor circuits connected in shunt between the input and output filter ports. A tracking control signal is selectively applied to change the capacitance of the LC circuits in order to shift the filter's frequency characteristics/profile as the filter tracks through the tracking band. The filter attenuates half-IF, receiver IF, and image spurious signals. In particular, the filter substantially attenuates the image spurious signal throughout the tracking frequency range by 50 dB or more below the filter output signal level. The filter also attenuates the half-IF spurious signal throughout the tracking frequency range by well over 10 dB or more below the filter output signal level. The receiver IF spurious signal is attenuated about 40 dB.

Abstract: The present invention pertains to a frequency-lock filtering receiver and the method for the same. The receiver enters a tuning mode before receiving signals. A frequency synthesizer then generates the radio frequency (RF) to be received and adjusts the central frequency of a tunable filter through feedback control so as to lock in the RF to be received. Afterwards, the receiver enters a receiving mode to receive RF signals using an antenna and uses the central frequency of the tunable filter locked in the tuning mode to filter the RF signals and to receive signals.

Abstract: An RF tuner and tuning method employs analog quadrature mixing with a coarse-stepwise tunable local oscillator to a near-baseband passband region, followed by A/D conversion of the I and Q signals, correction of phase, group delay, and amplitude errors, image rejection, and translation to baseband by (1) fixed frequency translation, (2) stepwise channelized translation, or (3) essentially continuously variable tuning over a given digital tuning range. The near-baseband passband region is sized and located such that alternating image rejection provides non-redundant and complete tuning coverage of a desired high frequency spectrum with a local oscillator step size equal to about twice the digital tuning range or about twice the number of channels digitally stepwise tunable times the channel width, effectively doubling the typical local oscillator step size.

Abstract: A front end and a high frequency receiver (1) provided therewith are described, which front end comprises a quadrature low noise amplifier (2-1, 2-2) as a low noise amplifier. A high isolation between local oscillators (6-1, 6-2) and quadrature mixers (3-1, 3-2) is achieved thereby, reducing a DC offset at mixer outputs (7, 8). The quadrature low noise amplifier may be implemented as a differential class AB cascode arrangement of MOST or FET semiconductors (15). A low distortion receiver (1) having a high linearity is the result.

Abstract: An RF tuner and tuning method employs analog quadrature mixing with a coarse-stepwise tunable local oscillator to a near-baseband passband region, followed by A/D conversion of the I and Q signals, correction of phase, group delay, and amplitude errors, image rejection, and translation to baseband by (1) fixed frequency translation, (2) stepwise channelized translation, or (3) essentially continuously variable tuning over a given digital tuning range. The near-baseband passband region is sized and located such that alternating image rejection provides non-redundant and complete tuning coverage of a desired high frequency spectrum with a local oscillator step size equal to about twice the digital tuning range or about twice the number of channels digitally stepwise tunable times the channel width, effectively doubling the typical local oscillator step size.

Abstract: A system and method for effecting wideband image rejection. In a receiver implementation, the inventive method includes the steps of receiving a first signal in a first frequency band and generating in-phase and quadrature signals therefrom. The phase of the in-phase signal is shifted to provide a second signal and the phase of the quadrature signal is shifted to provide a third signal. A predetermined phase relationship is thereby effected between the second and the third signals. The second and third signals are then summed to provide an output signal which has minimal interference from a mixing signal. In an illustrative receiver application, the phase shifting is achieved via the use of all pass networks. Each of the all pass networks include a differential amplifier having first and second input terminals. The first and the second terminals are connected to a first end of first and second resistive elements, respectively.

Abstract: The circuit arrangement utilizes both outputs of a mixer attenuating the image frequency, whereby one of the desired frequency bands is obtained from a “signal port” and the other desired frequency band from the “port of the image signal”. Thus a desired intermediate frequency signal band (IF) corresponding to the radio frequency Input signal (RF) can be selected using a switch (24), the intermediate frequency signal band (IF) being filtered by an intermediate frequency filter (20, 22). The frequency (LO) of the local oscillator is selected to be in the middle of the radio bands (RF).

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: Imager rejection circuitry includes a first digital path including a finite impulse response filter 202 having a variable gain stage 204 operable to apply a gain to a first digital signal in response to a coefficient selected from a coefficient table 206 and an adder 205 for summing the first digital signal to the output of the variable gain stage 205 to produce a corrected first digital signal. A second digital path processes a second digital signal and error calculation circuitry 207 determines an error between the first and second signals for selecting a coefficient from the coefficient table 206.

Abstract: A circuit configuration for filtering a radio-frequency signal, in particular, in tuners for television sets, includes a control signal connection for feeding in a control signal, a controllable-frequency oscillator, at least one filter having an adjustable passband for a useful signal, and a device for providing a correction signal. The filters are, preferably, tracking filters whose filter band can be shifted by a control signal. At least one filter has a variable-frequency element with a first connection and a second connection. The first connection is coupled to the control signal connection, and the correction signal device is coupled to the second connection. For fine tuning production tolerances, the filters are supplied with a correction signal, which is applied to the other pole of the variable-frequency element of the filter as compared with the control signal. The value range of the correction signals is limited to the correction range and is much lower than the value range for the control signal.

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: 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: A phasing receiver includes a quadrature mixing arrangement for frequency converting an input or high IF information signal to a pair of quadrature related low IF signals. The low IF signals are applied to a polyphase filter which functions as a low pass and adjacent channel rejection filter. One or more elements effecting a fine adjustment of relative phase away from quadrature and/or relative amplitude away from equality of the low IF signals are incorporated in information or oscillator signal paths in or about the mixing arrangement or a superhet stage preceding the quadrature mixing arrangement. These elements effect a predistortion of relative phase and/or relative amplitude of the low IF signals in order to compensate for mismatches in an input stage of the filter, and thereby improve image rejection by the filter.

Abstract: To reduce the impact of image frequencies generated by mixing an incident carrier signal down to a relatively low intermediate frequency signal used in subsequent signal processing, a mixing frequency is selected such that the generated intermediate frequency signal has a frequency offset relative to DC that is substantially that of a single channel spacing between frequency adjacent incident carrier signals, as shown in FIG. 2. Image rejection is further improved through the integration of a current-driven polyphase filter (36) directly between an input stage (Q1 to Q4) and a mixer stage (Q5 to Q12) of an image reject mixer (FIG. 4) such as to mitigate quadrature divergence between separate in-phase and quadrature paths within the image reject mixer.

Abstract: The following description regards a frequency converter (1) for applications on millimetric radio waves. The circuit structure comprises a diplexer filter realized in thin film on an alumina layer connected to a balun set up by a quartz plate on which two mixing diodes in GaAs have been mounted, placed in the center of a rectangular cavity (2) closed on one side by a short circuit plate and on the opposite side communicating with a rectangular waveguide (4) transporting a radio frequency signal (RF). On the upper side of the plate three parallel metallic bands have been put in the sense of the width of the cavity, between the bands the diodes are connected in series. The most external bands are welded to the walls of the cavity (2), the central one on the other hand is connected to the point common to both sections of the diplexing filter by means of a metallic strap in the air welded to a microstrip.

Abstract: In one embodiment, an apparatus comprising a mixing network coupled to a summing stage is presented. The mixing network is operative to receive a signal and process the received signal along a first branch of the mixing network to produce a first mixed signal containing an image signal, and along a second branch of the mixing network to produce a second mixed signal containing the image signal and a desired signal. The summing stage, coupled to the first and second branch of the mixing network, is operative to subtract the first mixed signal from the second mixed signal to produce a downconverted signal comprising the desired signal while rejecting the image signal.

Abstract: In one embodiment, an apparatus comprising a mixing network coupled to a summing stage is presented. The mixing network is operative to receive a signal and process the received signal along a first branch of the mixing network to produce a first mixed signal containing an image signal, and along a second branch of the mixing network to produce a second mixed signal containing the image signal and a desired signal. The summing stage, coupled to the first and second branch of the mixing network, is operative to subtract the first mixed signal from the second mixed signal to produce a downconverted signal comprising the desired signal while rejecting the image signal.

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: An image reject transceiver (10) provides both phase and gain adjustments that causes unwanted images to be rejected. A reference signal (RF.sub.IN) is frequency translated by two mixer circuits (28, 34) in a receiver circuit (16) to provide both an in-phase and an out-of-phase replica signal of the reference signal (RF.sub.IN) during normal operation. In a calibration mode a single frequency generated by a transmitter VCO (22) replaces the reference signal (RF.sub.IN). A phase detector circuit (38) provides a phase difference value that is fed back through a first switch (45) to a phase shift circuit (36) for adjusting the phase separation between the two replica signals. An amplitude detector circuit (40) provides an amplitude error value that is fed back through a second switch (47) to the mixer circuit (34) for adjusting and matching the gain of the two replica signals.

Abstract: A receiver for receiving both first-type reception signals, for example TV signals, and second-type reception signals, for example, FM-radio signals. The receiver may be used in multimedia applications. In the receiver, a reception signal is fed via an input section RFI-L, RFA-L, BPF-L to a mixer MIX-L. To obtain a relatively good performance, a band-pass filter BPF-L in the input section can be tuned through a frequency band, in which reception signals of both the first and the second type are present. The filter characteristics of the band-pass filter BPF-L are switched in accordance with the type of reception signal desired. For example, switching provides a passband which is substantially narrower for FM reception than for TV reception.

Abstract: For use with a first transceiver, a system for, and method of, calibrating a first image reject mixer in the first transceiver and having first and second image products. In one embodiment, the system includes: (1) a second image reject mixer, associated with a second transceiver and tuned to a rejected one of the first and second image products. The system further includes a signal strength circuit, coupled to the second image reject mixer, that determines a signal strength of the rejected one. The system still further includes a trimmer, associated with the first image reject mixer, that trims the first image reject mixer to move the rejected one toward an optimal value of the signal strength.

Abstract: A small elliptic high pass filter is incorporated into a low noise block downconverter (LNB) to reject image frequencies in a 12 GHz Direct home satellite television Broadcasting System (DBS). A waveguide transition with separate electric probes receives Ku-band satellite signals and transmits the signals to low noise amplifiers (LNAs), a power combiner, an elliptic high pass filter, and a HEMT MMIC receiver. Within the HEMT MMIC receiver, the signal is passed through an RF amplifier stage. A mixer mixes the signal from the RF amplifier stage with a local oscillator signal to produce an intermediate frequency (IF). An IF amplifier stage amplifies the IF signal which is further processed by a television decoder box. Due to the unique response of the elliptic high pass filter, the elliptic high pass filter provides a superior image rejection with lower insertion loss for the LNB, and therefore provides improved television reception quality.

Abstract: An image-rejecting receiver comprises a tunable mixer stage, a time-share I-Q mixer stage, a complex filter, and an image rejector. The time-share I-Q mixer stage includes a switch assembly, inphase and quadrature polarity inverters, and a clock generator. The switch assembly generates pulses and distributes them in alternation to the polarity inverters. Performing distribution prior to polarity inversion preserves the orthogonality of the inphase and quadrature target signal components despite pulse-to-pulse bleeding. Charge accumulated at the distributor switch input is dumped between pulses to further minimize such bleeding. A current-mode field-effect-transistor implementation ensures unity gain across each polarity inverter so that they are gain-matched. Gain matching and preservation of orthogonality optimize the conditions for the complex filter to attenuate and for the image rejector to cancel an image signal.

Abstract: A satellite broadcasting receiving tuner having a band-pass filter capable of adequately attenuating and removing disturbing wave components having frequencies in the vicinity of 480 MHz and capable of being easily tuned to the high-end frequency. The tuner has at least the band-pass filter for transmitting a down-converted received satellite broadcasting signal and a frequency converter section for converting the received satellite broadcasting signal transmitted through the band-pass filter into a signal having an intermediate frequency.

Abstract: An image-reject mixer includes a process for adding a signal to a RF input signal. Any imbalance in the mixer circuitry, which would lead to imperfect image suppression, is corrected by detecting any resulting local oscillator component in the mixer output signal, and adjusting the balance to minimize the size of the local oscillator component.

Abstract: An integrated transceiver circuit packaged component including a transceiver circuit having a bandstop filter (29) provided therein for filtering both the received and transmitted signals to remove unwanted components therefrom.

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 high dynamic range receiver IF system using limited dynamic range IF filters is disclosed. A variable gain amplifier amplifies a first IF signal. The amplified first IF signal is then applied to an image suppression mixer for suppressing an image component of the amplified first IF signal to provide adequate image suppression for a radio system, wherein the image suppression mixer outputting an image suppressed second IF signal. An active bandpass filter then filters the unwanted components from the second IF signal. The filtered signal is then hard limited in a limiting amplifier which outputs a limited IF signal. A logarithmic detector then provides a received signal strength indicator.

Abstract: A radio frequency receiver and method for operating one is disclosed. The receiver includes a tuning unit, an inphase-quadrature (I/Q) mixer, and a calibrated image rejection processor. The tuning unit selectably tunes to a tuning frequency close but not equal to an input modulated radio frequency and creates thereby a periodic signal having the tuning frequency. The I/Q mixer convolves the modulated radio frequency signal with inphase and quadrature versions of the periodic signal and low pass filters the resultant signals. The calibrated image rejection processor corrects at least one of the filtered resultant signals and performs image rejection on the corrected signals.

Abstract: A radio selective calling receiver having at least two, i.e., a first and a second, local oscillators constituted by respective synthesizers. The oscillation frequencies of the local oscillator are controlled by the apparatus including a frequency calculator for executing frequency calculations according to the received call signal frequency and the oscillation frequencies of the first and second local oscillators so that harmonics of either one of the oscillation frequencies are not interference frequencies to the other oscillation frequency or the received signal frequency.