Abstract: A frequency switching method is used to make switching among a plurality of frequency signal sources each providing a specific frequency range covering multiple bands. The method includes steps of providing a target frequency data; selecting one of the frequency signal sources to output a first clock signal; generating a first frequency data according to the clock signal of the first frequency to compare with the target frequency data; outputting a second clock signal with the highest band of another one of the frequency signal sources possessing a frequency range higher than that of the selected frequency signal source when the target frequency data is greater than the first frequency data; and outputting the second clock signal with the lowest band of the selected frequency signal source when the target frequency data is smaller than the first frequency data.

Abstract: A mixer in a smaller signal differential model includes a load circuit, a switch quad, and a transconductor. The switch quad further including a first current path and a second current path is coupled to the load circuit. The connecting node of the switch quad and the load circuit is a differential-output terminal. The transconductor further includes a first resistor, a first operational amplifier, a second operational amplifier, a first current mirror, and a second current mirror. The resistor is coupled between two first input terminals of the first operational amplifier and the second operational amplifier. A current control terminal of the first current mirror is coupled to the first input terminal of the first operational amplifier, and a current mirroring terminal of the first current mirror is coupled to the first current path.

Abstract: A mixer having high linearity and an associated transconductor combining programmable gain amplifier and mixer functions are provided. The transconductor includes first and second resistors, a differential amplifier, first and second feedback circuits, and first and second transistors. A differential voltage signal is inputted to first and second input ends of the differential amplifier via the first and second resistors. The first and second feedback circuits are provided between a first output end and the first input end, and a second output end and the second input end of the differential amplifier, respectively. The first output end outputs a first output signal for controlling a first current passing through the first transistor. The second output end outputs a second output signal for controlling a second current passing through the second transistor. The first current and the second current determine a differential current.

Abstract: A sigma-delta modulator includes a loop filter, a single bit quantizer, a single bit DAC, an adder. The loop filter is for filtering a summed signal to generate a filtered signal. The single bit quantizer is coupled to the loop filter, for performing a quantization process to the filtered signal to generate a quantized signal. The single bit DAC is coupled to the single bit quantizer, has an adjustable configuration, and is for generating a feedback signal according to the quantized signal and the configuration thereof. The adder is coupled to the loop filter and the single bit DAC, for summing an input signal and the feedback signal to generate the summed signal.

Abstract: A fingerprint sensing circuit for detecting a fingerprint of a user, including a signal source, at least a sensing unit, a resistor, an electrode, and a detecting circuit. The signal source provides a reference signal. The electrode is coupled to a reference level. The sensing unit generates a sensed value according to the electrode and the fingerprint of the user. The resistor is coupled between the signal source and the output node. The detecting circuit is coupled to the output node. The resistor, the sensing unit, and the electrode constitute a filter circuit to the signal source. At least a first signal is generated to the output node according to the reference signal and the sensed value, and the detecting circuit detects the first signal to generate a corresponding detected result indicative of the fingerprint.

Abstract: A mixer using a small signal differential model includes a load circuit, a switch quad, and a transconductor. The switch quad further including a first current path and a second current path is coupled to the load circuit. The connecting node of the switch quad and the load circuit is a differential-output terminal. The transconductor further includes a first resistor, a first operational amplifier, a second operational amplifier, a first current mirror, and a second current mirror. The resistor is coupled between two first input terminals of the first operational amplifier and the second operational amplifier. A current control terminal of the first current mirror is coupled to the first input terminal of the first operational amplifier, and a current mirroring terminal of the first current mirror is coupled to the first current path.

Abstract: A navigating system with RFID function includes a GPS module for receiving a plurality of satellite signals for location, and an RFID reader for receiving an RFID signal. The navigating system performs navigation according to a first position information and the location function of the GPS module if the RFID signal includes the first position information.

Abstract: A television tuner employs a triple-conversion architecture to translate VHF/UHF TV signals to various standard IF frequencies. The television tuner includes a harmonic rejection mixer, a first image rejection mixer and a second image rejection mixer. The television tuner receives a television signal. The harmonic rejection mixer up-converts the television signal into a first IF signal according to a first reference signal with a fixed frequency. The first image rejection mixer further up-converts the first IF signal into a second IF signal according to a second reference signal with a tunable frequency. The second image rejection mixer down-converts the second IF signal into a third IF signal according to a third reference signal with a tunable frequency.

Abstract: A television tuner employs a double quadrature mixing architecture to frequency-translate VHF/UHF TV signals to various standard IF frequencies. In the television tuner, a quadrature mixer converts the input television signal into a first in-phase signal and a first quadrature-phase signal according to a first reference signal, and a double quadrature mixer converts the first in-phase signal and first quadrature-phase signal into a second in-phase signal and a second quadrature-phase signal according to a second reference signal, and a polyphase filter filters the second in-phase signal and second quadrature-phase signal to produce an output signal.

Abstract: A television tuner employs a single down-conversion architecture to translate VHF/UHF TV signals to various standard IF frequencies. The television tuner includes a harmonic rejection and quadrature mixer and a quadrature mixer. The harmonic rejection and quadrature mixer mixes a first-band signal with a reference signal to output a first pair of in-phase and quadrature-phase signals with a harmonic-frequency component eliminated from the resulting signals. A quadrature mixer mixes a second-band signal with the reference signal to output a second pair of in-phase and quadrature-phase signals. A digital signal processing circuit coupled to both the harmonic rejection and quadrature mixer and the quadrature mixer for selectively processing either the first pair of in-phase and quadrature-phase signals or the second pair of in-phase and quadrature-phase signals to generate an output signal corresponding to a desired channel.

Abstract: A frequency switching method is used to make switching among a plurality of frequency signal sources each providing a specific frequency range covering multiple bands. The method includes steps of providing a target frequency data; selecting one of the frequency signal sources to output a first clock signal; generating a first frequency data according to the clock signal of the first frequency to compare with the target frequency data; outputting a second clock signal with the highest band of another one of the frequency signal sources possessing a frequency range higher than that of the selected frequency signal source when the target frequency data is greater than the first frequency data; and outputting the second clock signal with the lowest band of the selected frequency signal source when the target frequency data is smaller than the first frequency data.

Abstract: A method and an apparatus utilizing the RFID technology for the login security of a computing device are disclosed. The computing device includes a processing unit, an RFID reader, and a memory. The RFID reader is coupled to the processing unit for communicating with an external RFID tag in which a user data is stored. The memory is coupled to the processing unit for storing a login data. The RFID reader reads the user data from the RFID tag and the processing unit compares the user data with the login data. If the user data matches the login data, the processing unit allows the computing device to be accessed.