Abstract: Techniques for detecting and mitigating interference are described. A device (e.g., a cellular phone) senses interference levels and digitally reconstructs the expected interference in the received signal. The device may correlate the reconstructed interference with the received signal and determine interference in the received signal based on correlation results. The device may adjust the operation of one or more circuit blocks (e.g., a mixer, an LNA, etc.) in a receiver based on the detected interference in the received signal. Alternatively or additionally, the device may condition the digital interference to obtain conditioned reconstructed interference matching the interference in the received signal and may then subtract the conditioned interference from the received signal.

Abstract: An audio receiver may include a mono/stereo detector that causes the audio receiver to output either a monophonic or a stereophonic signal based on a difference between a pilot energy signal and a filtered pilot energy signal. The audio receiver includes a filter that filters the pilot energy signal to generate a filtered pilot energy signal, wherein a variable leakage factor associated with the filter is used to minimize a noise level of the filtered pilot energy signal and to reduce a response time of the audio receiver.

Abstract: A data interface method includes differentially amplifying differential data signals based on a mode control signal indicating a first mode, transmitting the amplified differential data signals to a receiving semiconductor device via first and second transmission lines, and driving one of the differential data signals and a strobe signal to the first and second transmission lines, respectively, based on the mode control signal indicating a second mode, for transmitting the one of the differential data signals and the strobe signal to the receiving semiconductor device. The receiving semiconductor device samples the received differential data signals according to differential signaling, in response to a controlled sampling clock signal based on the mode control signal indicating a first mode; and samples the one of the differential data signals in response to a strobe signal, received from the transmitting semiconductor device, based on the mode control signal indicating a second mode.

Abstract: In a control method of a communication system, a Base Station (BS) receives noise and interference information from at least one neighboring BS in charge of a neighboring cell being adjacent to a serving cell of the BS, calculates a control value of Mobile Stations (MSs) located in the serving cell according to the received noise and interference information, and generates control information according to the calculated control value, and transmits the generated control information to the MSs.

Abstract: The present invention reduces the degradation in performance of one or more radio signals that are co-transmitted with a first radio signal from the same transmitting antenna in the same frequency channel and received by the same antenna due to multipath or other shared interference, where the one or more radio signals can be separated from the first radio signal.

Abstract: A system for detecting and removing undesirable noise, such as beats and tones, from radio signals. The system includes a manual oscillator that is a manually tuned by a user to a selected manual frequency from one of a plurality of frequencies. An electronic oscillator is electronically tuned to a selected electronic frequency from one of the plurality of frequencies. A processor isolates and stores at least one interference frequency associated the selected electronic frequency and determines a correction signal to correct any interference frequencies within a particular selected electronic frequency. The selected manual frequency is corrected using the determined correction signal for the particular selected electronic frequency when the selected manual frequency is the same as the particular selected electronic frequency.

Abstract: Disclosed are methods and apparatus to control the actions of a user terminal (UT) located at a remote location, possibly far from a gateway (GW), which has an interface to the Public Switched Telephone Network (PSTN) and/or to the Internet. The methods and apparatus provide for operation of a mobile satellite communication system having at least one gateway (GW), at least one user terminal (UT), and a constellation of satellites. The methods and apparatus allow access to the communication satellites by specifying an exclusion zone having a confidence limit (CL) associated therewith. The methods and apparatus selectively provide service to a UT depending on a determined location of the UT relative to the exclusion zone and on an estimated error (E) of the determined UT location, wherein location of the UT is determined by the UT, and transmitted to the GW, or location of the UT is determined by the GW.

Abstract: An analog die (3) and a digital die (4) are supported by a plate (1) consisting of an electrically conductive material. Pads (5) of the dies (3, 4) are connected to each other, to plate (1) or to pins (2) surrounding the latter by bond wires (6). The upper side of the plate (1) is covered by a plastic mold (7) encapsulating the dies (3, 4), the bond wires (6) and, in part, the pins (2). For the suppression of external jamming signals as well as internal ones picked up by bond wires the digital die (4) comprises an adjustable notch filter which suppresses narrow frequency bands where jamming signals have been detected.

Abstract: A method for frequency conversion within a satellite-based repeater system. An uplink radio frequency signal having a frequency fRF is received. A first and at least a second local oscillator signal having frequencies fL01 and fLO2, respectively, is generated. The uplink signal is mixed at a first frequency conversion stage with the first local oscillator signal to generate an intermediate signal having a frequency fMF. The intermediate signal is mixed at a second frequency conversion stage with the at least second local oscillator signal to generate a downlink signal having a frequency fIF. The generation and mixing of the signals are performed such that: fLO1 and fLO2>fRF and fIF fMF=fLO1?fRF, and fIF=fLO2?fMF.

Abstract: The present invention can reduce interference generated by processors and other computing devices when a connected radio is active. In one embodiment, the invention may include determining a start of reception of radio signals by a radio, generating a radio active signal, transmitting the radio active signal to a coupled computer to affect the radio interference generated by the coupled computer. The embodiment may further include determining an end of reception of radio signals by the radio, generating a radio not active signal, and transmitting the radio not active signal to the coupled computer to affect the radio interference generated by the coupled computer.

Abstract: A multiplication section multiplies a signal output from a GPS antenna by a local oscillation signal generated by a local oscillation signal generation section to down-convert the signal output from the GPS antenna into an intermediate-frequency signal. A sampling circuit section samples a generated signal generated by a portable electronic circuit using a sampling clock signal having a frequency lower than a frequency of the generated signal. An attenuation section generates a cancellation signal by attenuating the sampled signal, and an addition section adds the cancellation signal to the signal output from the multiplication section to cancel in-band noise superimposed on the received signal.

Abstract: According to an example embodiment, an apparatus is provided in a wireless transceiver. The apparatus may include a circuit configured to generate a first frequency signal (e.g., a VCO signal). A local oscillator (LO) generator may be provided that includes a frequency divider to divide the first frequency signal, and an image rejection mixer configured to mix the first frequency signal with an output of the frequency divider to generate an LO signal. In this manner, the LO generator may generate a desired LO signal while substantially rejecting or suppressing an unwanted sideband or image signal, according to an example embodiment.

Abstract: A method for successive interference cancellation in code division multiple access (CDMA) systems is provided that uses variable interferer weights. This method allows interfering signals to be cancelled in order to recover a transmitted data signal. This method involves receiving the data signal subject to interference from at least one interfering signal. A first interfering signal is identified. Then an interferer weight coefficient associated with the first interfering signal is generated. This allows the first interfering signal to be cancelled from the received data signal using the interferer weight coefficient. These processes may then be reiterated for other interfering signals. It is then possible to recover the transmitted data signal from the received data signal.

Abstract: The radio frequency integrated circuit (RFIC) electrostatic discharge (ESD) circuit includes an integrated circuit pad and a radio frequency (RF) ESD circuit. The integrated circuit pad provides coupling to an antenna. The RF ESD circuit is coupled to the integrated circuit pad, wherein the RF ESD circuit provides ESD protection at the integrated circuit pad, provides coupling of inbound RF signals from the antenna to low noise amplifier, and provides coupling of outbound RF signals from a power amplifier to the antenna.

Abstract: A mobile wireless communications device includes a circuit board carried by a housing. A microprocessor, RF transceiver and circuitry are carried by the circuit board and operative with each other. Clock buffer circuitry is carried by the circuit board and connected to the RF transceiver and circuitry and microprocessor for isolating a clock signal from the noise of the microprocessor and allowing greater isolation for the RF transceiver from RF circuitry.

Abstract: In communications between a pair of stations using modulated carrier signals, a first station estimates the carrier frequency offset with respect to the second station and transmits signals that are responsive to the estimated carrier frequency offset. The first station may adjust the carrier frequency of the signals it transmits in response to the estimated carrier frequency offset, and/or transmit data to the second station representing the estimated carrier frequency offset. The second station adjusts the carrier frequency of the signals it transmits to the first station, and/or compensates for carrier frequency offset in its processing of received signals, in response to estimated carrier frequency offset data received from the first station.

Abstract: An electronic device includes a first circuit board having a first audio source and a first reference grounding end, a second circuit board having a second audio source and a second reference grounding end, a flexible board cable, a grounding wiring, a selection unit, and a receiver. The flexible board cable couples the first audio source to the second circuit board. The grounding wiring couples the first grounding end to the second circuit board. The selection unit is used for selecting one from the first and second audio sources to output and selecting one from the first and second reference grounding ends to output. An input end of the receiver is controlled by the selection unit to be connected to the first or second audio sources, and a grounding end of the receiver is controlled by the selection unit to be connected to the first or second reference grounding ends.

Abstract: A system having a signal processor for detection of a signal type of a signal is disclosed. One embodiment includes a processor designed to determine a first variable which is characteristic of a first spectrum element of the signal spectrum, and to determine a second variable which is characteristic of a second spectrum element of the signal spectrum. A system is provided for determination of a ratio between the first variable and the second variable, and a detector which is designed to detect the signal type on the basis of the ratio.

Abstract: Systems and methods for an RF nulling scheme are provided. An RF nulling scheme can minimize the level of unwanted RF signal reflections entering the receiver without attenuating the desired signal response from an RFID tag. In one aspect of the RF nulling scheme a synthesizer signal can be split between a main path and a nulling path. In the nulling path the signal from the splitter can be routed through an electronically variable phase shifter and variable gain amplifier to create a nulling signal. The nulling signal can cancel the unwanted reflected signal. The phase or amplitude of the nulling signal can then be adjusted to improve cancellation as necessary.

Abstract: During a telephony session, a determination is made on a mobile computing device that one or more designated conditions exist by which radio interference generated from the mobile computing device is to be reduced. In response, a power state of a set of one or more components of the mobile computing device is lowered. This reduces radio interference from those components. The set of components are ancillary to the mobile computing device's ability to maintain the telephony session, so that the telephony session is not affected by the reduction of power to the components.

Abstract: A MCM (multi-carrier modulation) receiver that utilizes a plurality tones to transmit information. Identify a first subset of tones that have negligible ISI (inter-symbol interference) and ICI (inter-carrier interference), and a second subset of tones that ISI/ICI cancellation is needed to improve the performance. For tones in the first subset, conventional FEQ (frequency-domain equalization) is performed to obtained soft decisions from the raw decisions. For those tones in the second subset, perform FEQ along with ICI/ISI cancellation. For tones in the second subset, identify a third subset (one for each of the tones in the second subset) to perform ICI cancellation and a series of fourth subsets (one for each of the tones in the second subset) to perform ISI cancellation.

Abstract: A radio frequency (RF) receiver and receiving method are provided which can remove a leakage component from a received signal by using a local signal. In the RF receiver, a noise removing unit controls a gain and a phase of a local signal LOI according to a phase THETA and a gain AMPTD detected in a MODEM, estimates a signal Vcal corresponding to a noise component introduced into a received RF signal RXIN, and removes the estimated signal Vcal from the received RF signal RXIN. In this manner, a clean RF signal RXO, which does not include a noise component, is frequency-down converted in a receiving unit.

Abstract: An embodiment of the present invention provides an apparatus, comprising a radio frequency identification transceiver adapted for self jammer suppression. The transceiver may further comprise a phase shifter and variable attenuator/variable amplifier adjusted to minimize the power injected into a receive chain by the self jammer. In an embodiment of the present invention the present transceiver may further comprise at least one RF peak power detector to determine the power injected into the receive chain.

Abstract: Methods, apparatus, and articles of manufacture are disclosed for removing an undesired component from a low intermediate frequency signal having an intermediate center frequency and an undesired component at a first frequency. One example method may include determining an amplitude of the undesired component; frequency shifting the low intermediate frequency signal from the intermediate center frequency to produce a zero intermediate frequency signal; filtering the zero intermediate frequency signal; generating a tone based on the amplitude of the undesired component; and subtracting the tone from the filtered zero intermediate frequency signal to remove the undesired component.

Abstract: Described are communication systems that convey differential and common-mode signals over the same differential channel. Noise-tolerant communication schemes use low-amplitude common-mode signals that are easily rejected by differential receivers, thus allowing for very high differential data rates. Some embodiments employ the common-mode signals to transmit backchannel signals for adjusting the characteristics of the differential transmitter. Backchannel control signals are effectively conveyed even if the forward channel transmitter is so maladjusted that the received differential data is unrecognizable. Systems in accordance with the above-described embodiments obtain these advantages without additional pins or communications channels, and are compatible with both AC-coupled and DC-coupled communications channels. Data coding schemes and corresponding data recovery circuits eliminate the need for complex, high-speed CDR circuits.

Abstract: A telephone signal cancellation circuit, a digital broadcasting reception circuit and a portable digital broadcasting reception apparatus is provided. The telephone signal cancellation circuit, includes a signal coupler for separating a part of a reception signal, a telephone signal selection filter for passing a telephone signal among signals from the signal coupler, a phase shifter for performing phase inversion on the telephone signal among the signals from the telephone signal selection filter, and a combiner for combining the signal from the phase shifter and the reception signal, and canceling the telephone signal included in the reception signal.

Abstract: A squelch detector that differentially detects a presence of a communication signal on a communication channel. The squelch detector being coupled to outputs of a differential offset bias amplifier to receive differential offset biased signals and generate a differential direct current signal.

Abstract: There is disclosed a radio frequency (RF) demodulation circuit comprising: 1) a first RF mixer having a first input port for receiving an in-phase RF signal having a frequency of RF and a second input port for receiving an in-phase local oscillator (LO) signal having a frequency of LO, wherein LO is approximately equal to one-half of RF, and wherein the first RF mixer generates a first intermediate frequency (IF) signal having a frequency of LO; 2) a second RF mixer having a first input port for receiving an out-of-phase RF signal having a frequency of RF and a second input port for receiving an out-of-phase local oscillator (LO) signal having a frequency of LO, and wherein the second RF mixer generates a second intermediate frequency (IF) signal having a frequency of LO; and 3) a first signal combiner for combining the first and second IF signals to generate a composite IF signal, wherein the first signal combiner combines a first leakage signal from the first RF mixer and a second leakage signal from the se

Abstract: Methods and apparatus for reducing the effect of surrounding noise in a push-to-talk (PTT) system are disclosed. In one embodiment, a method includes obtaining a first media stream using a microphone when a PTT functionality of a PTT communications system is in a first state, and identifying a first set of characteristics associated with noise in the first media stream. The method also includes obtaining a second media stream using the microphone that includes the noise and a first sound when the PTT functionality is in a second state. A second set of characteristics associated with the first sound in the second media stream is identified, and parameters associated with a filtering arrangement are determined using the first and second sets of characteristics. Finally, the method includes applying the filtering arrangement to the second media stream to filter out the noise such that a communications stream is created.

Abstract: A low noise amplification circuit comprises a low noise amplifier and a filter coupled to the input terminal of the low noise amplifier. The low noise amplifier comprises an amplifying element and a matching input circuit coupled to the input terminal of the amplifying element. When gamma.sub.s shows a reflection factor in the case that signals flow from the input terminal of the amplifying element to the output terminal of the matching input circuit, impedance conversion for setting the gamma.sub.s at a desired value is made entirely or in part by means of setting the output impedance of the filter at the value different from that of characteristic impedance.

Abstract: A high frequency receiver capable of stably canceling interference by a transmission signal even if a transmission signal input from a TV antenna is changed. Phase shifter (212) for changing a phase of an interfering distributed transmission signal, detector (216) for detecting a level of a transmission signal included in a receive signal input via an antenna, and level regulator (213) for changing a level of the distributed transmission signal in accordance with this level are provided. A signal input via level regulator (213) and phase shifter (212) and a receive signal are synthesized to be input into mixer (206). Since a transmission signal can be cancelled even if a transmission signal input from an antenna is changed, a high frequency receiver can receive a signal stably when a transmission signal is changed.

Abstract: A DC offset removal method and apparatus for use with a receiver, such as a direct conversion receiver. The DC offset error can be upconverted to an intermediate frequency where it appears as a DC offset spurious signal. The DC offset spurious signal can be amplified and downconverted back to a DC signal. The DC signal can be used to determine an offset correction value that can be coupled to a signal path to substantially remove the DC offset error. An embodiment is disclosed that allows a single module to be used to remove the static and dynamic DC offset error components. Another embodiment includes separate portions for the removal of static and dynamic offset errors.

Abstract: A system and method for detecting cell phone noise induced in telecommunication equipment, especially in microphones and other unshielded electronic units connected to a communication terminal. A noise detector is configured to execute a so-called “cepstrum” transform of a captured signal exposed to cell phone noise. Due to the characteristics of cell phone radio signals using TDMA, cell phone induced can then easily be detected from the cepstrum transform as peaks at known samples, and noise elimination or attenuation may then be executed on the captured signal when cell phone noise is detected.

Abstract: The present invention reduces the degradation in performance of one or more radio signals that are co-transmitted with a first radio signal from the same transmitting antenna in the same frequency channel and received by the same antenna due to multipath or other shared interference, where the one or more radio signals can be separated from the first radio signal.

Abstract: The present invention provides a DC offset correction system for a wireless communication device that removes a DC offset from a baseband receive signal during “training time” when the baseband receive signal should ideally have no DC content. In general, the DC offset correction system includes multiple configurable feedback loops that operate to remove or cancel the DC offset from the baseband receive signal. One or more of the multiple configurable feedback loops is activated for a period of time during operation when it is known that the received signal should ideally contain no DC content. This training time varies depending on the particular communication standard being used by the wireless communication device. For example, the training time may be during reception of the preamble and header of an IEEE 802.11 packet.

Abstract: A mobile device is provided that includes a digit input that can be manipulated by a user's fingers or thumb, an air conduction microphone and an alternative sensor that provides an alternative sensor signal indicative of speech. Under some embodiments, the mobile device also includes a proximity sensor that provides a proximity signal indicative of the distance from the mobile device to an object. Under some embodiments, the signal from the air conduction microphone, the alternative sensor signal, and the proximity signal are used to form an estimate of a clean speech value. In further embodiments, a sound is produced through a speaker in the mobile device based on the amount of noise in the clean speech value. In other embodiments, the sound produced through the speaker is based on the proximity sensor signal.

Abstract: An intermediate frequency receiver includes mixers for generating first and second IF signals from a RF signal and local oscillator signals. A magnitude calibration loop adjusts a gain of the first and/or second IF signals generated from the mixers depending on a magnitude difference between the IF signals. The phase calibration loop adjusts a phase of a local oscillator signal before being used at the mixers depending on a phase difference between the IF signals.

Abstract: An apparatus for generating an in-phase/quadrature-phase (I/Q) signal in a wireless transceiver is disclosed, including a local oscillator for generating an oscillation signal, and first and second mixers for mixing an oscillation signal with a transmission/reception signal to convert the transmission/reception signal into a baseband or high-frequency signal. The apparatus includes a phase locked circuit for controlling the local oscillator, and a polyphase filter installed between the local oscillator and the mixers, for separating the oscillation signal from the local oscillator into an I signal and a Q signal depending on a control signal from the phase locked circuit, and outputting the separated I and Q signals to the first and second mixers, respectively.

Abstract: A device (10) for reducing vibration effects on position measurement includes a receiver (12) for providing position signals (13); and a vibration control circuit (18) operative to control position information generation based on the position signals (13), to prevent position information generation during mechanical vibration of the device (10). A method for reducing vibration effects on position measurement includes receiving position signals through a receiver; and controlling position information generation based on the position signals to prevent the position information generation during mechanical vibration of the device.

Abstract: An SW control circuit turns ON and OFF a switch circuit provided between a reception antenna and an RF amplifier circuit, based on a noise removal control signal which is generated by a timing generation circuit and has a constant pulse width and a constant pulse interval, and thus the antenna is periodically short-circuited. In this way, even when the antenna receives a signal mixed with noise signals, accumulated energy due to the noise signals is periodically released, and thus the noise signals can be removed from the reception signal, and long lasting influence caused by the accumulated energy of the noise signals can be also removed.

Abstract: A mobile wireless communications device includes a housing and circuit board carried by the housing. Radio frequency (RF) circuitry carried by the circuit board forms a transmitter and receiver. A processor is carried by the circuit board and operative with the RF circuitry. A keyboard connector is mounted on the circuit board. A plurality of Key_Out and Key_In connection lines are carried by the circuit board and connect the keyboard connector and processor. A keypad is carried by the housing and operatively connected to the keyboard connector. A filter is operative with each connection line for limiting degradation in receiver sensitivity.

Abstract: A wireless communications noise suppression system comprises an electronic device having wireless module communicatively coupled to an antenna via a cable, an intermediate portion of the cable conductively coupled to ground.

Abstract: Some embodiments of the invention provide devices, systems and methods of noise identification and cancellation. For example, an apparatus in accordance with an embodiment of the invention includes: a characterizer to estimate a non-linear mutual relation between: a characteristic of an incoming interference signal, and an estimated portion of noise level in an incoming signal-of-interest caused by the incoming interference signal; and a noise canceller to reduce an effect of the interference signal on the signal-of-interest by applying a noise reduction algorithm based on said non-linear mutual relation.

Abstract: Various embodiments of the present invention adjust an operating mode of a configurable receiver based at least in part on a selected communication service to be provided and an available signal quality. A control unit receives data related to one or more selected communication services to be provided. The control unit also receives information about the environmental operating conditions in which the configurable receiver is operating, via one or more signal quality metrics. The control unit adjusts the operating mode of the configurable receiver by modifying the gain of a received signal, the channel bandwidth, or controlling the synthesizers or equalizers.

Abstract: A mixer for tuning to an intermediate frequency signal, an intermediate frequency amplifier provided at a rear stage of the mixer, an intermediate frequency tuning circuit interposed between the mixer and the intermediate frequency amplifier for tuning to the intermediate frequency signal, and a trap circuit interposed between the mixer and the intermediate frequency amplifier for attenuating the signal of an adjacent channel are comprised. By connecting a first switch means to the trap circuit in parallel to turn on the first switch means, the RF characteristic at an input port of the intermediate frequency amplifier or an output port of the mixer can be observed, without being influenced by the trap circuit.

Abstract: A mobile wireless communications device, system and associated method includes a housing and circuit board that includes radio frequency (RF) circuitry and processor operative with each other. The RF circuitry includes a low-IF receiver circuit that is operative for maintaining an interferer signal at a same frequency side as a wanted signal relative to a local oscillator frequency setting, creating an interferer image signal, and filtering the image signal as substantially baseband frequency.

Abstract: Described herein is technology for, among other things, reducing offset errors in RMS-to-DC converters. The technology involves generating first and second feedback signals with first and second feedback paths respectively. A multiplier is then employed to receive first and second signals and provide a third signal based on multiplying the first signal and the second signal. The first signal is based on an input signal and the first feedback signal, and the second signal is based on the input signal and the second feedback signal. A chopper is then employed to receive an output signal, which is based on the third signal, and a chopping signal, and in turn provide a fourth signal based on multiplying the output signal with the chopping signal. As a consequence, the fourth signal represents the output signal shifted to a frequency different than that of low-frequency noise components of the first and second signals.

Abstract: In one embodiment, a method that includes detecting a level on each of a plurality of data channels; summing the levels of a subset of data channels to get a summed level, the subset of data channels containing the lowest levels present in the plurality of data channels; comparing the summed level with the highest level present in the plurality of data channels; and rejecting a common mode interference in each of the plurality of data channels if the summed level exceeds the highest level present in the plurality of data channels. In another embodiment, an apparatus that includes a plurality of data channels; an array of input filters coupled to the plurality of data channels; a pulse detection circuit coupled to the array of input filters; a common mode rejection circuit coupled to the pulse detection circuit; and a pulse data queuing and transmission circuit coupled to the common mode rejection circuit. Other methods and apparatuses are disclosed.

Abstract: Described are communication systems that convey differential and common-mode signals over the same differential channel. Noise-tolerant communication schemes use low-amplitude common-mode signals that are easily rejected by differential receivers, thus allowing for very high differential data rates. Some embodiments employ the common-mode signals to transmit backchannel signals for adjusting the characteristics of the differential transmitter. Backchannel control signals are effectively conveyed even if the forward channel transmitter is so maladjusted that the received differential data is unrecognizable. Systems in accordance with the above-described embodiments obtain these advantages without additional pins or communications channels, and are compatible with both AC-coupled and DC-coupled communications channels. Data coding schemes and corresponding data recovery circuits eliminate the need for complex, high-speed CDR circuits.

Abstract: An objective of this invention is to obtain a signal processing circuit and a signal processing method that reduce temperature-induced distortion when inputting a signal to a mixer and changing the frequency of the signal to a desired frequency. If a sensing result from a temperature sensor 133 is lower than a predetermined temperature, the attenuation factor of a first variable attenuator 102 is large while the attenuation factor of a second variable attenuator 108 is small. The magnitude relationship between the attenuation factors is reversed in a temperature range of the predetermined temperature or more. In a mixer 104 in which at a low temperature, the gain increases, and distortion increases, an increase in IM3 distortion can be prevented by increasing the attenuation factor at a low temperature. The same applies to a case where a mixer that has an amplifier arranged at a preceding stage thereof and makes the amplification factor of the amplifier large at a low temperature is used.