摘要:
The invention relates to a demodulator and to a radio receiver having such a demodulator and, more particularly, to a demodulator for demodulating signals which were digitized by a direct detecting method in which a circuit scale is small and an electric power consumption is small. Particularly, it is a characteristic that a limiter in the demodulator comprises: a circuit for obtaining absolute values of the digital signals (I signal, Q signal) which are produced from an angle modulated wave and whose phases are mutually orthogonal; a circuit for outputting the sum (.vertline.I.vertline.+.vertline.Q.vertline.) of the absolute values or the larger one M(.vertline.I.vertline., .vertline.Q.vertline.) of the absolute values; a controller for producing a control signal according to an output of the above circuit; and scalers which change the amplitudes of the first and second digital signals in accordance with the control signal and which are constructed by a plurality of shift registers and adders.
摘要:
A method of controlling the time constant of a filter for use in a radio receiver which receives a signal, transmitted from a transmitting station at a predetermined period, intermittently at the predetermined period and demodulates and delivers the received signal, a filter circuit having the time constant control function based on the method, and a radio receiver having the filter circuit. Preferably, the filter has its time constant switchable stepwise and specifically, parallel connection of capacitors or shortcircuiting of resistors is controlled by turning on/off switches. A controller within the filter circuit or the radio receiver performs control for applying a predetermined periodical signal (or standard pulse signal) to the filter and controlling the time constant of the filter in accordance with an output signal (or triangular pulse) during a first time zone within each operation interval for the intermittent reception and for filtering the signal from the transmitting station and causing a demodulating circuit to demodulate and deliver a filtered signal.
摘要:
There is provided a signal processing device and a wireless apparatus capable of not erroneously determining polarity, appropriately performing a spread modulation process, a carrier modulation process, and reception data demodulation process, improving reception accuracy, and miniaturizing a circuit, even when IF carrier frequency shift occurs. The signal processing device and the wireless apparatus includes a spread modulation unit which includes a first differential encoding process section for performing a differential encoding process on a reception data, a differential encoding process section for performing a second differential encoding process on the output, and a spread modulation process section for performing a spread modulation process on the output using a spread code; a carrier modulation unit which quadrature-modulates a transmission data spread modulation signal and a continuous wave; and a reception data decoding unit which performs a correlation process twice and a delay detection process twice.
摘要:
An object of the present invention is to provide a sensing instrument capable to detect a substance existing in a very small quantity, such as environmental pollutants, instantly with a high degree of precision. As a specific means for solving the problem, a frequency signal from a crystal oscillator is sampled using a frequency signal from a reference clock generating part, the sampling value is outputted in a digital signal, quadrature detection is conducted with the digital signal for a frequency signal corresponding to the output signal, the rotational vector rotating at a frequency corresponding to the difference between the frequency of the frequency signal and the frequency of a sinusoidal wave used for the quadrature detection is taken out, and the variation of the frequency is detected by detecting the velocity of the rotational vector based on the respective sampling values. In addition to that, the measurement range of the variation of frequency can be widened by multiplying the above-described rotational vector by the reversely rotational vector corresponding to the velocity of the rotational vector.
摘要:
An object of the present invention provides a frequency synthesizer having a broad frequency entraining range which can finely set a frequency over a broad band by a novel principle.As s specific solving means, a sinusoidal signal of an output frequency of a voltage-controlled oscillator is subjected to orthogonal detection, a vector rotating at the differential frequency (speed) between the output frequency and the frequency of the frequency signal used for the detection is created, and the frequency of a vector when the output frequency of the voltage-controlled oscillator is equal to a set value is calculated in advance. The voltage signal corresponding to the difference between the frequency of the vector and the calculated frequency is fed back to the voltage-controlled oscillator when the voltage-controlled oscillator is driven, and PLL is formed so that the difference is equal to zero. Accordingly, the output frequency of the voltage-controlled oscillator is adjusted to the set frequency when PLL is locked. After the difference between both the frequencies is increased after PLL is locked, the set value is integrated by the integrating circuit portion and added to the control voltage.
摘要:
A VCO driving circuit and a frequency synthesizer wherein the impedance viewed from a VCO control terminal is reduced to prevent the VCO phase noise characteristic from degrading. A VCO driving circuit and a frequency synthesizer having the VCO driving circuit, which comprises a coarse adjustment DAC that receives a digital data, which has a coarse adjustment frequency, to output an analog signal; a fine adjustment DAC that receives a digital data, which has a fine adjustment frequency, to output an analog signal; a low response speed LPF5 that removes noise from the output signal from the coarse adjustment DAC and then provides the resultant signal as an input to a VCO control terminal; a high response speed LPF7 that converts the output signal from the fine adjustment DAC to a voltage, thereby smoothing the signal; a resistor that connects an input stage of the LPF5 to that of the LPF7; and a capacitor used for providing a capacitive coupling such that the output of the LPF7 is added to that of the LPF5.
摘要:
A data transmission system for transmitting data from a transmitter to a receiver located away therefrom. The transmitter includes circuitry for transmitting together a main signal having a carrier modulated with main data to be transmitted and as well as a sub-signal to be used in frequency conversion and generated by modulating a carrier of a predetermined frequency out of a frequency band of the main signal. The receiver includes circuitry for receiving a receive signal from the transmitter and extracting the sub-signal therefrom and also includes circuitry for generating a signal to be used as a reference at the time of converting the receive signal to a signal having a predetermined frequency on the basis of the extracted sub-signal.
摘要:
A digital signal communication system includes a transmission circuit or a receiving circuit for digitally transmitting two types of signals by orthogonal modulation. The transmission circuit includes an orthogonal modulator and a nonrecursive digital low-pass filter having the same frequency characteristic as a predetermined frequency characteristic of the output signal of the orthogonal modulator. The receiving circuit includes an orthogonal demodulator and a nonrecursive digital low-pass filter having the same frequency characteristic as a predetermined frequency characteristic of the output signal of the orthogonal demodulator. The total number of taps required for determining the frequency characteristic of the nonrecursive digital low-pass filter is set to H, and the series of tap coefficients is set as C1, C2, C3, . . . , CH, where H is an arbitrary positive integer of not less than 2. The nonrecursive digital low-pass filters include a first low-pass filter for filtering one of the two types of signal and a second low-pass filter for filtering the other type of the signal. The first low-pass filter has taps about one half of H including a tap coefficient series C1, C3, C5, . . . , CODD, and the second low-pass filter has taps about one half of H including a tap coefficient series C2, C4, C6, . . . , CEVEN.
摘要:
An orthogonal frequency division multiplex (OFDM) modulator of such a system as to add guard intervals to a temporal waveform generated by modulating an input data train into a large number of (sub)carriers, conducting quadrature modulation, and outputting an OFDM signal. The OFDM modulator includes an IFFT circuit for conducting inverse fast Fourier transform processing to modulate the input data train into a large number of (sub)carriers, a guard interval adder for adding a guard interval to each effective symbol duration of a composite carrier signal supplied from the IFFT circuit and outputting a resultant signal, a control signal generator for generating, in synchronism with each guard interval of the composite carrier signal having the guard intervals added thereto, such a control signal as to attenuate signal amplitude of the composite carrier signal over an interval substantially equal in length to each guard interval; and an amplitude controller, responsive to the control signal, to attenuate the amplitude of the composite carrier signal supplied from the guard interval adder and output a resultant signal, only over an interval substantially equal in length to each guard interval. The amplitude controller outputting, in remaining intervals, the composite carrier signal supplied from the guard interval adder as it is.
摘要:
This invention proposes a radio communication system including a plurality of radio terminals, a relay apparatus (including a plurality of base stations and an exchange station) connected to each radio terminal so that the radio terminals can interchange information from each other, and a data processing unit connected to the relay apparatus, each radio terminal having a circuit for inputting and outputting a voice signal and a circuit for inputting and outputting data whereby it can communicate with another radio terminals or with the data processing unit through the relay apparatus. The radio terminal of this invention further has a clock, and a circuit for storing a schedule inputted by the user thereby to automatically select a receiving mode such as a ringing mode or a nonringing mode in accordance with the contents of the schedule, the present time and so on.