Abstract: There is provided a frequency converter for suppressing generation of an image signal using a simple adaptive algorithm. In the frequency converter, an orthogonal converter 21 converts an RF/IF signal to a complex signal along with frequency conversion and ADCs quantize the complex signal. An image signal canceller achieves the complex conjugate of the quantized complex signal by inverting the imaginary part of the quantized signal through a multiplier. An LMS core adaptively processes the complex signal using the complex conjugate signal as a reference signal and the output of the image signal canceller as an error signal. The resulting cancellation signals are level-matched in attenuators. Subtracters combine the complex signal with the level-adjusted complex conjugate signal.

Abstract: A digital frequency converter is provided that maintains a high power efficiency in an EER scheme despite the inclusion of digital signal processing. An inputted modulated signal is converted into phase information and amplitude information of a polar coordinate type. The amplitude information is outputted as amplitude information of the digital frequency converter. Meanwhile, phase change of a frequency f2, which is outputted from an accumulator, corresponding to lower ‘Q’ figures of phase data PD for frequency conversion is added to the phase information by an adder. In addition, a sampling frequency of the phase information outputted from the adder is upsampled by an interpolator, and also, phase change of a frequency f3, is converted into a phase-modulated signal of an orthogonal coordinate type, and then outputted as phase information of the digital frequency converter.

Abstract: Disclosed is a receiver for achieving optimum power consumption and optimum reception performance according to use, purpose, and required performance. A control circuit calculates an evaluation value H relating to a detection method and a reception state of a received signal. When a delay detection is selected depending on the evaluation value H, a delay detection circuit and a judgment circuit operate, and a selection circuit selects and outputs an output signal of the judgment circuit. When a semi-synchronous detection is selected depending on the evaluation value H, the semi-synchronous detection circuit, the signal judgment unit and the differential decoder operate, and the selection circuit selects and outputs an output signal of the differential decoder. When a dynamic controlled detection is selected depending on the evaluation value H, the delay detection and the semi-synchronous detection are controlled to be dynamically changed.

Abstract: Disclosed is an automatic gain controller capable of reducing signal saturation or signal distortion caused by out-of-band signals of a filter extracting an object signal or delay of a control signal and capable of precisely measuring a signal level in a filter band. An AGC response control section compares a level of control voltage (“V2_I terminal” signal) outputted from a first AGC control section and inputted into a “V2_I terminal” with a level of control voltage (“V3_I terminal” signal) outputted from a second AGC control section and inputted into a “V3_I terminal”. If the control voltage, which is the “V3_I terminal” signal, outputted from the second AGC control section is less than the control voltage, which is a “V2_I terminal” signal, outputted from the first AGC control section, the AGC response control section controls an AGC amplifier by using the control voltage outputted from the second AGC control section.

Abstract: A numerical control oscillator (NCO) for reducing a circuit size and power consumption while maintaining a desired frequency deviation, and suppressing generation of a spurious as much as possible. The NCO comprises a phase accumulator for accumulating input phase difference data to generate phase data, and a read only memory (ROM) for storing a phase/amplitude conversion table to output amplitude data corresponding to the phase data generated by the phase accumulator. The phase accumulator includes a phase register and a phase calculator. If a sampling frequency of an output signal from the NCO is Fs, the upper limit of a desired frequency setting interval of the output signal is FD and K and L are arbitrary integers, the phase calculator adds or subtracts the input phase difference data and phase data from the phase register to or from each other by a modulo operation taking the nearest integer of M as a modulus, where M=Fs/FD×K/L.

Abstract: Disclosed are a wireless phone and a wireless communication method wherein communication quality estimation is made for both circuit switching and packet communication modes and sound of both the modes is interpolated mutually so as to improve the sound quality. The switching between first and second sound signals is performed at intervals of a speech pitch period based on quality information of first and second sound signals, where the first and second signals are received and decoded, respectively, through a first wireless communication in circuit switching mode and a second wireless communication in packet communication mode. A delay control signal is outputted to compensate for the time difference between the first and second sound signals, based on the quality information of the two sound signals, and the time difference is compensated for based on the delay control signal.

Abstract: Radio equipment including a characteristic compensator for compensating for an orthogonality error of a mixer with low consumption power is disclosed. In radio equipment, an orthogonal detector converts a received real signal into a complex reception signal of an intermediate frequency. Further, when a complex reception signal converted into a digital signal by A/D converters includes a desired signal (quasi-desired signal), which includes an image signal of a non-desired signal, and a non-desired signal (preparatory desired signal), which includes an image signal of a desired signal, a frequency of the quasi-desired signal is frequency-converted to a signal closer to a direct current component by a frequency converter and a frequency of the preparatory desired signal is frequency-converted to a signal closer to a direct current component by a frequency converter. A decimator respectively performs a filtering and a down-sampling on the frequency-converted quasi-desired signal and preparatory desired signal.

Abstract: Radio equipment capable of application to transmission and reception signals based on an FDD mode, and of compensation of characteristics of transmission signals with the use of a small-scaled circuit construction. In the radio equipment, a receiver causes an RF (Radio Frequency) band of signals obtained from an antenna sharer to be converted into signals having an intermediate frequency (IF) by means of a mixer and to be changed into digital signals by means of Analog-to Digital Converter. Further, both reception signals and image signals of transmission signals, both of which have the IF A and are contained in the converted signals, are converted into reception signals having the IF B and image signals having the IF C, respectively, both of which have positive and negative carrier frequencies symmetrical to a direct current component having a frequency of zero and are represented as a complex number, by a quadrature detector 18.

Abstract: A frequency synthesizer that improves a unique DDS characteristic, while maintaining a circuit scale (ROM size) of a direct digital synthesizer (DDS). A first digital signal generator generates a quantized frequency signal, and a second digital signal generator generates a frequency signal having a fine frequency resolution and many spurious signals as compared with the first digital signal generator. A filter performs band rejection on an output of the second digital signal generator, and a mixer mixes an output of the first digital signal generator with an output of the filter.

Abstract: A multichannel receiver for effectively receiving multichannel signals at the same time without any restrictions in the symbol timing and channel interval of modulated signals. A quadrature detector of the multichannel receiver includes first and second multipliers. The first multiplier multiplies a received signal by a real number axis signal generated from a quadrature carrier oscillator. The second multiplier multiplies a received signal by an imaginary number axis signal. The quadrature detector converts a carrier of a center signal of odd signals into a DC component of zero frequency, and converts the center signal into a complex baseband signal, and at the same time converts carrier signals other than the center carrier signal into a complex IF signal symmetrical to the DC component of zero frequency. ADCs (Analog-to-Digital Converters) convert the complex IF signals into complex IF digital signals.

Abstract: There is provided a frequency converter for suppressing generation of an image signal using a simple adaptive algorithm. In the frequency converter, an orthogonal converter 21 converts an RF/IF signal to a complex signal along with frequency conversion and ADCs quantize the complex signal. An image signal canceller achieves the complex conjugate of the quantized complex signal by inverting the imaginary part of the quantized signal through a multiplier. An LMS core adaptively processes the complex signal using the complex conjugate signal as a reference signal and the output of the image signal canceller as an error signal. The resulting cancellation signals are level-matched in attenuators. Subtracters combine the complex signal with the level-adjusted complex conjugate signal.

Abstract: Disclosed is a frequency converter with an excellent frequency characteristic, having a minimized number of multipliers. A digital down-converter includes a decimator/mixer, an interpolator and a channel filter. The decimator/mixer performs quadrature conversion from a real signal to complex signals, frequency conversion by a frequency K&ohgr;, and 1/(M×I)-fold decimation on a signal obtained by sampling an RF/IF signal S(i) by an A/D converter. The interpolator is comprised of I-fold up-samplers and lowpass filters, and performs I-fold interpolation on the outputs from the decimator/mixer. The channel filter is comprised of lowpass filters having a band characteristic given to a communication channel, and outputs band-rejected baseband signals i(j) and q(j) by filtering the outputs of the interpolator.

Abstract: A transmitter for data communication capable of reducing generation of spurious signals without an increase in a ROM size of a DDS (Direct Digital Synthesizer), which causes an increase in power consumption, and without restricting a transmission frequency. The transmitter comprises a first mixer for converting an output of a modulator to a first IF (Intermediate Frequency) signal using a first local signal generator; a digital filter for suppressing a predetermined out-band signal among the first IF signal; and a second mixer for D/A (Digital-to-Analog)-converting an output of the digital filter, and converting the D/A-converted signal to a second analog IF signal or RF (Radio Frequency) signal using a second local signal generator. A frequency step of the first local signal generator is less than a frequency step of the second local signal generator.

Abstract: A frequency synthesizer that improves a unique DDS characteristic, while maintaining a circuit scale (ROM size) of a direct digital synthesizer (DDS). A first digital signal generator generates a quantized frequency signal, and a second digital signal generator generates a frequency signal having a fine frequency resolution and many spurious signals as compared with the first digital signal generator. A filter performs band rejection on an output of the second digital signal generator, and a mixer mixes an output of the first digital signal generator with an output of the filter.

Abstract: A digital down-converter and a receiver capable of reducing power consumption. The digital down-converter converts a frequency of a signal, received at a radio receiver and sampled with a radio frequency (RF) or an intermediate frequency (IF), to a detection frequency for a detection process. The digital down-converter comprises a first mixer for converting a frequency of the received signal to a frequency of a first IF signal; and a second mixer for converting the first IF signal converted by the first mixer to a second IF signal of the detection frequency, and complexing the converted signal.

Abstract: A digital filter including an Infinite Impulse Response (IIR) digital filter; limit cycle suppression signal generating means for generating a limit cycle suppression signal whose amplitude level is larger than a critical input amplitude level in a dead band range in which an output of the IIR digital filter is set to a dead band amplitude level and whose frequency component exists in only a useless frequency band of a signal system; and adding (subtracting) means for adding (subtracting) an input signal to be inputted to the IIR digital filter and the limit cycle suppression signal and for inputting an output to the IIR digital filter.

Abstract: A digital amplitude modulation apparatus for amplitude-modulating a digital carrier having a frequency fc by a digital modulating wave associated with a sampling frequency fs1, at a sampling frequency fs2, wherein the conditions m.times.fs1=fs2, and fc=n/4.times. fs2 are satisfied, where m is a positive integer (2, 4, 6, . . . ) and n is a positive integer (1, 3, 5, . . . ). A fold distortion relative to an original digital amplitude modulated wave is not generated even if a fold component elimination filter is not used.

Abstract: In an SSB modulation/demodulation apparatus having a band-pass filter having a plurality of switchable bandwidths for restricting a signal transmission bandwidth, and a Hilbert converter constructed of a network having a pass band over all frequency ranges, the Hilbert converter is a digital Hilbert converter arranged to be set with switchable Hilbert conversion coefficients.