Abstract: An apparatus includes a current generator (101) having an output. A plurality of mixers (103, 105, and 107) is switchably coupled to the current generator output, such that a first average power output level is provided when a first mixer (103) of the plurality of mixers is engaged and a second average power output level is provided when a second mixer (105) of the plurality of mixers is engaged. Alternatively, a first average power output level is provided when a first mixer (103) and a second mixer (105) of the plurality of mixers is engaged and a second average power output level is provided when the first mixer (103) of the plurality of mixers is engaged. The first average power output level and the second average power output level are different.

Abstract: A signal generator 5 which generates one of two input signals to a frequency mixing circuit 1 for outputting a signal having a frequency which is a difference between frequencies of the two signals or a sum thereof. In the present invention, an attenuating circuit 6 for attenuating an output signal from a voltage-controlled oscillator 2 for generating one of the input signals as well as a filter circuit 7 for limiting a frequency band of an output signal from the attenuating circuit are interposed between the frequency mixing circuit and a voltage-controlled oscillator 2.

Abstract: The present invention teaches parallel coupling what are herein termed a “switching stage” and a “steering stage,” thereby arranging the mixer and variable gain amplifier circuitry as a single merged circuit. The merged variable gain mixers of the present invention provide mixing and gain functionality utilizing only that power needed for a basic mixer function and only the transconductance of the basic mixer function (thereby eliminating non-linearities introduced by additional transconductance stages of prior art circuitry). Further, in the merged variable gain mixers described herein, no additional headroom is needed other than what is required by the basic mixer function. The present invention contemplates a variety of merged variable gain mixers including AC and DC coupled merged variable gain mixer of both single and double balanced configuration.

Abstract: A first local signal required for a downconverter of a reception system and an upconverter of a transmission system in a first band is generated by a synthesizer for generating a variable high frequency local signal. A second local signal required for a downconverter of a reception system and an upconverter of a transmission system in a second band is generated by mixing a signal generated by an oscillator for generating a signal at a relatively low fixed frequency with the first local signal using a mixer and filtering the result using a high-pass filter.

Abstract: The present invention is directed to a multiplex radio transmission/receiving system. The system includes a plurality of transmission sections provided so as to correspond to a plurality of channels, and a plurality of receiving sections provided so as to correspond to the plurality of channels. Each transmission section includes a modulation section, a first frequency conversion section, a first band-pass filter, a second frequency conversion section, and a second band-pass filter. Each receiving section includes a third band-pass filter, a third frequency conversion section, a fourth band-pass filter, a fourth frequency conversion section, and a demodulation section. By selection of an optimum value for a second intermediate frequency of a transmitter and for a third intermediate frequency of a receiver, a group of transmission radio frequencies (RF) signals and a group of local frequency signals are allocated without overlap.

Abstract: A broadband integrated television receiver for receiving a standard antenna or cable input and outputting an analog composite video signal and composite audio signal is disclosed. The receiver employs an up-conversion mixer and a down-conversion mixer in series to produce an IF signal. An IF filter between the mixers performs coarse channel selection. The down-conversion mixer may be an image rejection mixer to provide additional filtering. The received RF television signals are converted to a standard 45.75 MHz IF signal for processing on-chip by additional circuitry.

Abstract: A multi-band microwave detector includes an antenna, a plurality of reception systems connected to the antenna in a parallel arrangement, a judgement circuit for judging whether or not a microwave signal detected by the reception systems is a detection target microwave signal, an alarm circuit for outputting an alarm when the judgement circuit judges the detected microwave signal to be a detection target microwave signal, wherein each reception system is constructed from a superheterodyne reception circuit having a prescribed intermediate frequency that is mutually different from the intermediate frequencies of all the other reception systems, and wherein all the reception systems are operated simultaneously during one detection cycle.

Abstract: A novel frequency scheme for a police radar detector enables improved sweeping of the X, K, Ku and Ka radar bands. The novel frequency scheme requires two initial frequency conversions for detection of the X, K and Ka radar bands and a single initial frequency conversion for the Ku radar band with single initial frequency conversion being enabled by disabling the second mixer. During sweeping of the X, K and Ka bands, selectable, i.e., upper or lower, sideband suppression is employed to reduce undesired image sidebands and noise prior to the second frequency conversion. In addition, noise at the second IF frequency is reduced to prevent this noise from feeding through the second mixer into the second IF amplifier. During the Ku band sweep, the second mixer is bypassed and shunting of signals at the second IF frequency is disabled so that these signals enter the second IF amplifier.

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 a receiving and transmitting apparatus, a frequency of a direct digital synthesizer provided in a local oscillating circuit is controlled in order to reduce a frequency error, based on data of a frequency error detecting circuit. The direct digital synthesizer includes a digital operation circuit for inputting data designating the frequency and outputting an amplitude value of a periodic signal synchronous with a reference clock, and digital-analog converter for converting the amplitude value of the periodic signal to an analog signal.

Abstract: An apparatus includes a current generator (101) having an output. A plurality of mixers (103, 105, and 107) is switchably coupled to the current generator output, such that a first average power output level is provided when a first mixer (103) of the plurality of mixers is engaged and a second average power output level is provided when a second mixer (105) of the plurality of mixers is engaged. The first average power output level and the second average power output level are different.

Abstract: A mixer circuit, and an associated method, mixes together differential input signals with differential mixing signals to form differential output signals. The differential output signals are substantially linearly related to the input signals over an entire range of input signal values. The mixer circuit forms, in exemplary implementations, portions of a radio receiver device or a radio transmitter device, such as the radio receiver and transmitter portions of a cellular radio telephone.

Abstract: In general, the present invention provides a low cost mechanism for reducing the settling time and/or improving the phase noise performance of a frequency synthesizer in a mobile station. In one embodiment, the present invention eliminates the need for using two transmit offset synthesizers in a mobile station which must be able to operate on two different frequency bands characterized by different transmit-receive (TX-RX) channel separation. According to the present invention, one or both of the transmit offset synthesizers may be eliminated by deriving an appropriate transmit offset signal from an auxiliary synthesizer in the mobile station through a relatively simple and inexpensive frequency scaling circuit (e.g., frequency divider or multiplier), and by using a fast settling main channel synthesizer to hop between two different frequencies when the mobile station is switching between transmitting and receiving, respectively.

Abstract: An improved multiple conversion CATV settop terminal eliminates the adverse effects of oscillator difference beats by selectively controlling local oscillators and the use of a wideband bandpass filter. The wideband bandpass filter is coupled between the output of an up converter mixer and the input of a down converter mixer. Each mixer receives a second input from its corresponding local oscillator. A system microprocessor is programmed to control each local oscillator such that the oscillator difference beat frequencies are translated out of a following IF filter passband. Once translated, the oscillator difference beat frequencies no longer present a source of distortion to the received information signal.

Abstract: A receiver, especially useful for MMIC semiconductor communications circuits, in which plural mixers replace LRC filter networks to produce notched bandwidth filters. In a preferred embodiment, the input signal and a the output of a variable oscillator are mixed to produce a beat frequency. As an operator changes the desired frequency notch of the receiver, the output frequency of variable oscillator similarly changes to ensure that the beat frequency is the same regardless of desired frequency. Circuity downstream may be thus fixed, eliminating the need for large variable capacitors, which MMIC technology cannot fabricate in desirably small sizes.

Abstract: A double superheterodyne type receiving circuit having a first local oscillating circuit for converting a received signal into a first intermediate frequency signal and a second local oscillating circuit for converting the first intermediate frequency signal into a second intermediate frequency signal, comprising an oscillator 16 composing the first local oscillating circuit, a first variable frequency divider 17 composing the second oscillating circuit for dividing the frequency of an output signal of the first oscillator, a second variable frequency divider 18 for dividing the frequency of an output signal of the first variable frequency divider, a variable frequency dividing controlling circuit 23 for controlling frequency dividing values of the first and second variable frequency dividers on the base of an exponential function relation, at least one fixed frequency divider 19 for dividing the frequency of an output signal of the second variable frequency divider 18, a reference oscillator 20 for outputtin

Abstract: A wayside station communicates with a plurality of mobile stations over a wireless communication network. In one embodiment, a wayside station includes a transceiver configured to receive an inbound signal from a mobile station and to transmit an outbound signal to the mobile station. The transceiver has a first switch that is configured to selectively deliver the inbound signal to one of a first band pass filter (BPF) and a second BPF. A second switch is coupled to the first BPF and to the second BPF, and configured to selectively receive the inbound signal from one of the first BPF and the second BPF. A detector is coupled to the second switch and configured to detect the inbound signal, to convert the inbound signal to inbound data and to transfer the inbound data to a processor. The processor decodes the inbound data and processes the data.

Abstract: An amplifier and a portable telephone apparatus using the same in which a resonance circuit is provided for each of different frequencies and bypass capacitors of the ground terminal of a transistor are properly switched according to the different frequencies. Two capacitors connected to each other in series for the parallel resonance circuits to be connected to the output terminal of the amplifying transistor are used for the resonance capacitors for the higher frequency. For the lower frequency, one of the tow capacitors that is on the ground side is used as a bypass capacitor that grounds the ground terminal of the transistor in a high frequency manner, the other capacitor being functioned as a resonance capacitor at that frequency.

Abstract: A receiver system and method of operation are used to tune a selected channel from an input spectrum. The receiver includes an up-converter which responds to a selection setting for up-converting the input spectrum, including the selected channel and an unwanted spectrum; a first diplexer for dissipating the energy of the unwanted spectrum in a manner to reduce distortion effects on the up-converter; a down-converter for down-converting the up-converted selected channel having associated upper and lower sidebands and an intermediate frequency component; and a second diplexer for dissipating the energy of the upper and lower sidebands of the down-converted selected channel in a manner to improve intermodulation of the down-converter.

Abstract: A heterodyne receiver operating on the principle of synchronous modulation for time-signal reception where a first mixer is driven by the first phase-locking loop which is fed from a reference frequency source and a switchable precharging value. By means of switched frequency dividers and the precharging values, internationally different clock frequencies (JP: 40 kHz; USA/GB: 60 kHz; EU/D: 77.5 kHz) can be processed and converted to the intermediate frequencies. These are then synchronously demodulated by means of a second mixer which receives its signal from the second phase-locking loop that is driven through the intermediate frequency signal via the phase comparator, and also through the control signal of the phase-locking loop, so that only residual error adjustment need be performed.

Abstract: A double super tuner for receiving television signals from conventional broadcast, CATV, satellite broadcast, and HDTV. A first frequency converter converts an input high-frequency signal in a first intermediate frequency band signal based on a first local oscillator signal. The output of the first frequency converter is band-pass filtered by a dielectric filter. A second frequency converter converts the output of the dielectric filter into a second intermediate frequency band signal based on a second local oscillator signal.

Abstract: According to a second embodiment of the invention, a mobile phone receiver comprises a first down converter using a first local oscillator frequency which can be tuned in frequency steps by a programmable digital frequency synthesizer PLL which is locked to a reference frequency. The first down converter converts received signals to a first IF for filtering. A second down converter using a second local oscillator converts first IF signals to a second IF. The second local oscillator frequency is generated using a second digital frequency synthesizer PLL which locks the second oscillator to the reference frequency. A third down converter mixes the transmit frequency with the first local oscillator frequency to produce a lock frequency. A third digital frequency synthesizer PLL compares the lock frequency and the reference frequency to control generation of the transmit frequency.

Abstract: A circuit arrangement includes a tuner and a splitter-modulator having a splitter and a modulator. The splitter includes an RF signal input for receiving an RF input signal, an RF signal output for supplying an RF output signal, a first line for applying the RF input signal to the tuner and a second line for receiving an RF output signal from the modulator. The tuner is adapted to demodulate the RF input signal, and the modulator is adapted to convert a baseband signal into the RF output signal to be supplied by said modulator. The circuit arrangement further includes devices for generating reference oscillations for the tuner and the splitter-modulator, these devices having at least one quartz crystal which is common for the tuner and the splitter-modulator, and a phase-locked loop which is common for the tuner and the splitter-modulator.

Abstract: A radio frequency (rf) receiver adapted to receive a number of different digitally modulated rf input signals such as quadrature amplitude modulated (QAM) and vestigial side band (VSB) rf input signals includes circuitry for down converting the rf input signals to an intermediate frequency (IF) range having a center frequency fc2 and a bandwidth of Bhz and converter circuitry for sampling the IF signals and then producing corresponding baseband signals. In a preferred embodiment, the intermediate frequency signals are applied to a sample and hold circuit which is sampled at a frequency fs and whose output is coupled via a low pass filter to an analog-to-digital converter whose output is then applied to a Hilbert filter for demodulating the sampled signals and producing baseband signals. In-phase (I) and quadrature (Q) signals are produced whose phase and amplitude are not a function of different components and their tolerance of different conduction paths, as in the prior art.

Abstract: The present invention is a method and apparatus for signal conditioning which reduces non-linear distortion caused by RF/FM transmitters by lowering the carrier frequency of the modem transmit signal. This is accomplished by lowering the highest frequency in the input signal to the RF/FM transmitter. In one embodiment, modem datapumps are modified so that the optimal modem carrier frequency is utilized for data modulation. The optimal carrier frequency is computed by placing the lowest frequency component in the transmit spectrum at the low band-edge of the RF channel. In other embodiments, a conventional modem transmit spectrum is shifted to the optimal carrier frequency, which is determined by the method described above. Another aspect of the present invention involves the modification of the receiving modem to operate with both conventional land-line modems and the present invention modified-carrier modems used in conjunction with the cellular telephone network.

Abstract: In radio transmitting equipment that develops a carrier frequency using a mixer, techniques are used to "shift" or "hide" spurious mixer outputs so that they do not significantly degrade spectral purity of the transmitter output. These techniques generally involve establishing a predetermined frequency relationship between the two signals inputted to the transmitter mixer (TXIF (VCO) and TXLO) in addition to the relationship required to provide the desired difference frequency when the two signals are mixed in the mixer. By establishing a certain predetermined frequency relationship between these two signals it is possible to precisely locate the frequencies of the undesirable mixer output products so that they can be filtered out and/or fall onto the desired output frequency. While generally applicable, these techniques provide special advantages in equipment in which other considerations constrain the design of the transmitter circuitry and frequency inputs thereto.

Abstract: The device includes a first frequency synthesizer loop with fractional division to a apply a first wide frequency band transposition signal to an input of the first mixing stage of the receiver, a second phase-lock frequency synthesizer loop to apply a second narrow frequency band transposition signal to an input of the second mixer stage of the receiver and a common frequency source coupled to the first loop and to the second loop for the application, to their reference inputs, of a frequency reference signal. Application to wideband (20 MHz to GHz) V/UHF receivers.

Abstract: There is disclosed a fully integrated television receiver for receiving a standard antenna or cable input and outputting a standard video baseband signal and a standard audio baseband signal. The receiver employs an up-conversion mixer and a down-conversion image-rejection mixer in series to produce an on-chip IF signal. Audio detection of the IF signal is performed via an audio delay-locked loop operating in quadrature to the audio FM signal. Video detection of the IF signal is performed by frequency mixing the IF signal with the extracted video carrier of the IF signal. Variable load drive capability is provided for both the video output and the audio output.

Abstract: The dual band code division multiple access radio of the present invention operates on multiple frequencies simultaneously on either transmit or receive. The transmit path operates by splitting the transmit intermediate frequency (IF) path (103) and mixing the IF to two different transmit frequencies using two frequency synthesizers (140 and 145). The receive path (104) has two RF channels (116 and 117) that are mixed with the frequencies generated by the synthesizers (140 and 145) and summed into one IF strip. Thus the radio of the present invention can perform a soft hand-off between frequencies while communicating with both base stations simultaneously. Additional mixing paths and synthesizers can be added if it is desired to communicate with more than two base stations simultaneously.

Abstract: A method of processing an electronic signal so as to facilitate the reduction of spurious signals, which includes mixing the electronic signal with a first synthesized signal of varying frequency to form a combined signal, passing the combined signal through at least one electronic component to produce an exiting signal, and mixing the exiting signal with a second synthesized signal of varying frequency which is correlated to the first synthesized signal, to form an output signal having spurious signals which are spread.

Abstract: A device for generating a first signal and a second signal in a receiver for reception of a number of radio frequency signals. The first signal is mixed in a first mixer with the received radio frequency signals in order to generate an intermediate frequency signal which is subsequently mixed with the second signal in a second mixer. A first oscillator generates a signal which, after frequency multiplication in a frequency multiplier, is the first signal, the frequency of which can be changed in a number of frequency steps. A second oscillator generates the second signal, the frequency of which also can be changed in a number of frequency steps. The magnitude of the frequency steps by which the first signal can be changed is a multiple of the frequency steps by which the second signal can be changed.

Abstract: The number of oscillators required to construct a digital radiocommunication terminal can be reduced and a circuit used for the digital radiocommunication terminal can be reduced in size. For this purpose, the digital radiocommunication terminal for effecting information transmission using an N (integer)-phase-shift-keyed signal (identification symbol number N=4 upon .pi./4 shifted QPSK modulation), is constructed such that an oscillation frequency generated from a reference oscillator employed with a frequency synthesizer is selected to have a common multiple of a second intermediate frequency and an identification symbol phase N and is supplied to a detector for outputting received data therefrom.

Abstract: A multiple conversion receiver system capable of avoiding receiver spurs by combined switching of multiple local oscillator frequencies, including combinations of high-side and low-side injection and IF shifting.

Abstract: A cordless telephone system includes a single base unit and at least two remote handunits, where the base unit employs two transmitter channels coupled together through a low impedance and coupled to a single antenna. The transmitter channels include voltage controlled crystal oscillators (VCXOs) and frequency tripler circuitry, rather than PLLs in order to keep intermodulation distortion at the outputs of the transmitter amplifiers to a minimum.

Abstract: A method and apparatus utilizing the techniques of frequency shifting and filtering for converting an input signal having a desired signal at intermediate frequency and an undesired DC offset to a baseband frequency signal in which the undesired DC offset is eliminated. The apparatus includes a first multiplier for multiplying the input signal by a signal having substantially the same intermediate frequency plus an offset frequency (.DELTA.f) to produce a first output signal wherein the desired signal is shifted in frequency to the offset frequency (.DELTA.f) and the undesired DC offset is unaffected. The apparatus also includes a second multiplier coupled to the first multiplier for multiplying the first output signal by a signal having substantially the same offset frequency (.DELTA.f) to produce a second output signal having the desired signal shifted to baseband frequency and the undesired DC offset shifted in frequency to the offset frequency .DELTA.f.

Abstract: A method of receiving a data signal in a radio transceiver by passing an input receive signal through an input bandpass filter having a bandwidth sufficient to reject signals with frequencies equal to or greater than the receive signal frequency plus a first intermediate frequency (IF) signal frequency plus a first standard IF signal frequency and also to reject signals with frequencies less than the receive signal frequency minus twice the first IF frequency, and downconverting the input filter filtered input receive signal by the transmit frequency to produce the first IF signal. The first IF signal is filtered in an LC filter, and the filtered first IF signal is mixed with a local oscillator signal having a difference frequency therefrom which is equal to the first standard IF frequency to produce the first standard IF signal.

Abstract: It is desirable that a cordless telephone system include a single base unit and at least two remote handunits. With such a system, two users may maintain participation in a three-way conversation while being free to move about within reasonable transmitting distance to and from the base unit. Circuitry is provided in which a signal received from one handunit is transmitted to the other handunit, and sidetone from one handunit is transmitted back to that handunit.

Abstract: A radio frequency (RF) transceiver for modulating and demodulating RF signals with a direct modulation transmitter and a dual intermediate frequency (IF) receiver, respectively, includes a local oscillator, three frequency converters, a demodulator, a carrier generator, a modulator, a controller and two signal switches. The local oscillator (e.g. phase lock loop PLL!) provides a first local oscillator (LO) signal. One frequency converter (e.g. mixer) frequency converts an incoming modulated RF signal with the first LO signal to provide a first modulated IF signal. A second frequency converter frequency converts the first modulated IF signal with a second LO signal to provide a second modulated IF signal. The demodulator also receives the second LO signal and demodulates therewith the second modulated IF signal. The carrier generator (e.g. voltage-controlled oscillator VCO!) receives a transmitter control signal and in accordance therewith generates a transmitter carrier signal.

Abstract: A frequency synthesizer using a fixed oscillator driving a comb line generator to generate a spectrum of comb lines, one of which is selected by a switched array of fixed-tuned, YIG passband filters. The selected comb line is combined in a mixer with a signal from a local oscillator, which, preferably, is a direct digital synthesizer. The output of the mixer is fed to another switched array of fixed-tuned YIG passband filters where only the desired sideband is selected and the comb line and the other sideband is filtered out. In various alternative embodiments, tunable YIG filters are substituted for each array. Some embodiments also use a reverse slope equalizer to break up the coherent energy in the comb line spectrum at the output of the comb line generator to allow RF amplification to be applied without saturating the amplifier.

Abstract: A sound carrier detecting circuit for use in a television or a video tape recorder is disclosed. During the sound carrier detection, the carrier frequency of the sound signals is corrected by utilizing pulse width modulation signals output from a microprocessor, so that the noise due to shifting of the detected frequency can be eliminated. The circuit includes a key input part provided with one or more keys for selecting a tuning state, and a microprocessor for outputting pulse width modulating signals and manual sound tuning signals in response to appropriate settings of the key input means. A variable oscillating part for converting the pulse width modulating signals into dc component signals and, in turn, outputting variable frequency signals in accordance with the level of the dc component signals is provided alongside a frequency modulating and oscillating part which oscillates and outputs set frequency signals set to a specific frequency in accordance with the relevant broadcasting method.

Abstract: A wideband microwave detector includes: a first local oscillator outputting a first local oscillation output containing a basic wave component, a secondary high harmonic component and a tertiary high harmonic component and being swept within a predetermined frequency range; a first mixer performing frequency mixing of the first local oscillation output and an antenna input input through an antenna and outputting a first mixing output; a second local oscillator outputting a second local oscillation output; a second mixer performing frequency mixing of the first mixing output and the second local oscillation output for generating a second mixing output, a single frequency discriminator for detecting a specific frequency in a discrimination input, and mode selector switch alternately switching a single super heterodyne reception mode, in which the first mixing output of the first mixer is introduced into the frequency discriminator as the discrimination input and a double super heterodyne reception mode, in whic

Abstract: A radio receiver, and associated method therefor, for generating a baseband signal having signal component portions of time-varying frequencies. The oscillating signal generated by at least one of the local oscillators of down-mixing circuitry of the receiver is modulated by a low-frequency signal thereby to cause the resultant, baseband signal to be comprised of signal component portions of time-varying frequencies. Because the signal component portions of the baseband signal are of time-varying frequencies, attenuation of such signal component portions and resultant distortion of the received signal, as a result of undesirable notches in the frequency response of a radio receiver is avoided.

Abstract: The frequency of a first local oscillator signal (1.LO) is offset in reference to the center frequency of a first bandpass filter (4), and the frequency of a second local oscillator signal (2.LO) is offset in reference to the center frequency of a second bandpass filter (7). The frequency offsets are selected so that only a portion (x, y) of the filter (4, 7) bandwidths (bw, BW) will add to an "imaginary" effective narrow bandwidth (NBW). The amounts of frequency offset are continuously adjustable by programmable controller.

Abstract: A double super-heterodyne tuner provided with an up-converting section and a down-converting section, and including an input filter constituted by single tuning to be supplied with an input signal, an RF amplifier for amplifying the signal passing through the input filter, and an inter-stage tuning circuit constituted by single tuning connected to an output end of the RF amplifier and provided at an input portion of the up-converting section. The input filter and the inter-stage tuning circuit are supplied with a tuning voltage different from that supplied to a first local oscillator so as to alter its filter characteristics for simplification of the circuit construction and improvement of NF (noise factor).

Abstract: High receiver sensitivity and narrowband coherent resolution can be achieved at millimeter and submillimeter wavelengths through the process of heterodyning or intermediate frequency (IF) generation. The two frequencies, whose IF is being generated, need not be very stable in frequency or phase themselves. The requirement is only, that they fluctuate identically in frequency and phase, so that their fluctuations cancel at the IF. This can be achieved by deriving both from one and the same source. We have applied this process twice in a millimeter and submillimeter receiver of high sensitivity and resolution. At the same time the receiver is very simple, since the frequency and phase stability of the two sources involved does not affect sensitivity and resolution.

Abstract: A radio receiver with two receiving systems includes a CPU for selecting the appropriate ranges of local signal generators in the two receiving systems so that local signals generated by the local signal generators do not fall into the frequency range of a received RF signal.

Abstract: A radio receiver for data communication of the type handing digital signals has a radio frequency (RF) section for receiving an RF signal having a predetermined frequency band from an electromagnetic wave which comes in through an antenna. A first frequency converting section converts the RF signal received by the RF section to a first intermediate frequency (IF) signal. A first IF filter filters the first IF signal and is implemented by a surface acoustic wave filter. A second frequency converting section converts the output signal of the first IF filter to a second IF signal. A data amplifying section picks up the above-mentioned frequency band from the output of the second frequency converting section and amplifies the resultant, picked-up band. A detector detects the output of the data amplifying section. An equalizer corrects a deviation of group delay time with each of respective frequencies of the output of the detector.

Abstract: An offset frequency converter for the intermediate frequency (IF) stages of a multi-channel radio frequency (RF) phase/amplitude measurement receiver, particularly useful for measuring the performance characteristics of antennas. The converter allows use of noncoherent transmitter and receiver local oscillator sources which utilize digital frequency synthesizers and enables harmonic mixing to be employed when the tuning resolution of the receiver local oscillator is incremental. The converter samples an incoming first intermediate frequency signal IF.sub.1 in a reference channel, which typically is obtained by mixing an LO source in the receiver with an incoming signal from a reference antenna. The IF.sub.1 sample is then upconverted with an upconversion signal to a higher frequency, filtered, and the downconverted with a downconversion signal to an IF.sub.1 +IF.sub.2 signal offset from the IF.sub.1 sample by a lower second intermediate frequency IF.sub.2. The added frequency offset IF.sub.

Abstract: A radio transceiver is coupled to a source of a reference waveform, and includes transmit mode receive modes. The transceiver comprises a first down mixer, a first low pass filter coupled the first down mixer, and a first selective coupling switch. The first down mixer is coupled to receive an input signal having an input frequency, for mixing the input signal with the reference waveform to produce a first signal. The first signal has a frequency substantially lower than the input frequency. The first low pass filter is coupled the first down mixer for producing a filtered first signal. The first selective coupling switch couples the first down mixer and the low pass filter when the radio transceiver is in the receive mode, and decouples the first down mixer and the low pass filter when the radio transceiver is in the transmit mode, thus substantially eliminating transient disturbances.

Abstract: Both the low and high intermediate frequencies (IF) are amplified simultaneously in a single IF amplifier strip. For proper operation it is required that the two IFs be sufficiently isolated from each other so that independent tuning can be achieved. In operation, the RF signal is amplified and mixed down by a first local oscillator (LO). The RF signal is amplified in the IF strip to obtain IF #1. IF #1 from the strip is mixed down with a second LO in a feedback arrangement to obtain IF #2 simultaneously with IF #1 from the strip.