Kabushikikaisha Kenwood

Atsushi Shinoda

Kenichi Shiraishi

Shoichi Suzuki

Yasuhide Okuhata

Toshiyuki Takegahara

Hiroyuki Nagasaka

Ryuichi Okazaki

A diversity receiver capable of stably receiving an orthogonal frequency division multiplex signal, wherein a demodulator is so operated that the attenuation of the received signal is varied step by step every time a period corresponding to a guard interval section comes if it is determined that the reception level is increased by switching the attenuation in any one of variable attenuators, and the demodulator is so operated that the variable attenuator designated by an antenna control pointer is changed and the attenuation is varied if it is determined that the variable attenuator designated by an antenna control pointer is identical with the variable attenuator designated by an antenna fixing pointer.

Diversity receiver, and method for receiving orthogonal frequency division multiplex signal

Reception timing of a signal consisting of a valid symbol section and a guard interval section is controlled properly. According to a result of auto-correlation calculation performed by a guard correlation processor, a timing adjustment block generates a control voltage for adjusting the reception timing of the valid symbol section. A first and a second loop filter filter the control voltage signal generated by the timing adjustment block and sends it to a switch. An inter-symbol interference decision block decides whether an inter-symbol interference is generated according to the result of the auto-correlation calculation performed by the guard correlation processor, and controls the switch according to the decision result. Where, in the first loop filter, a comparatively large gain is set while in the second loop filter, a comparatively small gain is set.

Orthogonal frequency division multiple signal reception apparatus, reception apparatus, orthogonal frequency division multiple signal reception method, and reception method

An AM neighboring interference removing method and circuit is provided which can select only a desired AM modulation wave even if an interference AM modulation wave is partially superposed upon the desired AM modulation wave. An AM modulation wave desired to be received is multiplied at multipliers by local oscillation signals having frequencies 3fc/2 and fc/2 where fc is the carrier frequency of a neighboring interference AM modulation wave. High frequency components contained in the outputs of the multipliers are removed by low-pass filters. Of the outputs of the low-pass filters, the carrier frequency of the neighboring interference wave is fc/2 and the AM carrier frequencies of the AM stereo modulation wave are (fc/2+f&#x3b1;) and (fc/2&#x2212;f&#x3b1;), where f&#x3b1; is a difference frequency between the AM carrier frequency of the AM stereo modulation wave and the carrier frequency of the neighboring interference wave. A subtractor subtracts the output of one of the low-pass filter from the output of the other to thereby cancel out the neighboring interference wave. This subtraction signal is passed through a low-pass filter having a cut-off frequency of fc/2 to derive only the AM stereo modulation wave.

Method for removing AM neighboring interference and a circuit for the same

A carrier reproducing circuit capable of judging the polarity of alienation frequency. A TMCC section is detected from the synchronous detection output from a synchronous detection circuit () by a TMCC section detecting circuit (), the synchronous detection output is converted to a signal point arrangement by a signal point arrangement converting circuit (), the phase of the converted signal point position signal is rotated at a predetermined angular velocity for each symbol of the TMCC by a phase rotating circuit (), the signal position signal whose phase is rotated is phase-detected by a phase detector (), an auto-correlation function of the phase detection output in the TMCC section is determined by an auto-correlation function determining circuit () and angular velocity information based on the period of the waveform of the determined auto-correlation function is obtained, the phase-rotation angular velocity at the phase rotation circuit () is subtracted from the obtained angular velocity by a subtracting circuit (), and sine and cosine wave data on frequency based on the output of the subtraction are generated and sent to the phase detection circuit () by a numerical control oscillator ().

Carrier reproducing circuit

The present invention provides an AM modulated wave eliminating circuit which is capable of extracting a digital modulated wave by cancelling an AM modulated wave from an AM data multiplex modulated wave. A composite wave is composed of an AM carrier wave in-phase signal, an AM carrier wave reverse-phase signal and a digital modulated wave is extracted from an AM data multiplex modulated wave composed of an AM stereo modulated wave multiplexed with a digital modulated wave within the same frequency band, values corresponding to different phase deflection angles of an AM stereo output from a phase level generator (,) are multiplied by the AM carrier wave in-phase signal with multipliers (,through,), multiplication outputs are added to the composite wave with adders (,through,), a phase deflection angle corresponding to an output at a minimum level out of addition outputs is determined with a phase presumer (,), a value corresponding to a determined phase deflection angle is selected from an output of a phase level generator (,) with a phase level selector (,), a selected value is multiplied by an AM carrier wave in-phase signal component with a multiplier (,), a multiplication output is added to the composite wave with an adder (,) and an addition output is used as a digital modulated wave.

AM modulated wave eliminating circuit

An apparatus for demodulating an AM data multiplexed modulated wave signal in which an analog modulated signal and digital modulated signals are multiplexed, in order to derive therefrom a baseband digital signal. The demodulation apparatus aims to derive the digital baseband signal from the AM data multiplexed modulated wave signal in which the analog modulated signal obtained by amplitude modulating a carrier having a frequency fc with an analog signal and the digital modulated signals at frequency position of (fc+f.alpha.) and (fc-f.alpha.) line-symmetrical with respect to a frequency axis of the frequency fc are multiplexed. A demodulation apparatus includes an AM type modulated wave signal eliminating circuit for removing an AM modulated wave signal from an input AM data multiplexed modulated wave signal, and a data demodulation circuit for receiving an output of the AM type modulated wave signal eliminating circuit and for deriving therefrom a baseband digital signal.

Apparatus for demodulating AM data multiplexed modulated wave signal

An AM data multiplexing modulation apparatus for multiplexing a digital signal to an AM modulation signal without adversely affecting an AM sync detection output even if AM sync detection is performed. An AM modulator AM modulates a carrier having a frequency fc by an input signal, an orthogonal modulator 3 orthogonally modulates a carrier having a frequency (fc+f.alpha.) by a QPSK baseband digital signal generated by a QPSK baseband digital signal generator 2, a sign inverter and a complex conjugate unit change the sign of a signal having the same phase as a reference carrier of vector shift and corresponding to a dibit formed by the QPSK baseband digital signal generated by the QPSK baseband digital signal generator, another orthogonal modulator orthogonally modulates a carrier having a frequency (fc-f.alpha.) by an output of the complex conjugate unit, the outputs of the two orthogonal modulators are added by an adder, this addition result is added to the output of the AM modulator by another adder which outputs an AM data multiplexing modulation output.

Growing community of inventors

Sagamihara, Japan

Atsushi Shinoda