Nippon Hoso' Kyokai

Japan Radio Co., Ltd.

Tokin Corporation

Hisashi Naka

Kazuhisa Hayeiwa

Yutaka Kojima

Michikazu Kondo

Tadasu Ishikawa

Michitoshi Minami

Yoshiro Sato

Kazuaki Wakai

Yoshikazu Toba

Tetsuroh Miyazaki

Michitosi Minami

Tohru Mizokami

An amplitude modulation circuit and method. A predetermined number of (e.g., 6) drivers and differentially switched power amplifiers are provided in pairs. A program sound signal which has been quantized into a predetermined number of bits (e.g., 12 bits) is divided through a ROM into a plurality of bit groups each consisting of a predetermined number of bits (e.g., 2 bits), which are in turn distributed to the respective driver and differentially switched power amplifier pairs. In response to the value of the distributed bit group, each driver selects two different phase-shift carriers from seven different phase-shift carriers, and provides as its outputs .phi..sub.A and .phi..sub.B. With the output phase-shift carriers (.phi..sub.A and .phi..sub.B), each driver differentially switches the differentially switched power amplifier corresponding thereto. The output of each differentially switched power amplifier is weighted. The outputs of all the differentially switched power amplifiers are combined by a power combiner and then filtered through a BPF, thereby obtaining a broadcast output which has been amplitude modulated by the program sound. Thus, a digital amplitude modulation can be realized using a lower number of power amplifiers than before.

Amplitude modulation circuit and method

An electric field sensor comprises an electric field sensor head (3) for varying an intensity of a propagating light beam in response to an electric field intensity of an input signal received by a reception antenna (1). The electric field sensor head (3) comprises an incident optical waveguide (9), two phase-shift optical waveguides (10) having a variable refractive index which varies in response to the electric field intensity, an outgoing optical waveguide (11) and, at least one modulation electrode (12) formed in the vicinity of at least one of the two phase-shift optical waveguides (19). The electric field sensor further comprises a circuit element (2) connected between the modulation electrode (12) and the reception antenna (1). The modulation electrode (12) has a thickness not smaller than 1 .mu.m. The modulation electrode (12) may comprise a plurality of split electrodes which are split in a light propagating direction and which are capacitively coupled. The reception antenna (1) is preferably implemented by a low radiation resistance antenna.

Electric field sensor

An amplitude modulation system. An input analog signal indicating audio, etc., is converted into a digital form and the low-order bits of the resultant digital signal are converted into analog form. The resultant analog signal is used to control a gain of an analog controlled amplifier. On the other hand, a plurality of digitally controlled amplifiers are selectively turned on/off in response to the value of the high-order bits of the digital signal. Carrier amplified by the analog controlled amplifier are combined with carriers amplified by the plurality of digitally controlled amplifiers. Comparatively rough amplitude constituents are provided by outputs of the plurality of digitally controlled amplifiers and comparatively fine amplitude constituents are provided by output of the analog controlled amplifier.

Amplitude modulation method and broadcasting apparatus for carrying out

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Tokyo, Japan

Hisashi Naka