Radio receiving apparatus for receiving communication signals of different bandwidths
First Claim
1. A radio receiving apparatus for a radio system in which carrier frequencies are channel-positioned at equal frequency intervals and which employs a quadrature demodulation scheme, said radio receiving apparatus comprising:
- means supplied with a received signal including a signal of a reception-desired channel, for selectively converting, into an intermediate frequency band, a frequency band including three channels on each of upper and lower sides of a center frequency that is an upper or lower end of the reception-desired channel or a boundary frequency with an adjacent channel thereof;
means for sampling the frequency-converted signal at a frequency that is 16-fold a bandwidth of the reception-desired channel or 16-fold of a 1/2 frequency of a channel interval frequency of the radio system;
means for extracting orthogonal components in a phase domain from the sampled signal; and
means for extracting the signal of the reception-desired channel from a real-axis signal component and an imaginary-axis signal component of the extracted orthogonal components.
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Accused Products
Abstract
A received signal obtained from an antenna is subjected to high-frequency amplification. The amplified signal is supplied to a first bandpass filter, which extracts only signals of all the channels of a communications system concerned while filtering out other radio signals. The extracted signals are frequency-converted by using a local oscillation frequency, and only a desired wave is passed by a second bandpass filter. The desired wave is supplied to a sample-and-hold circuit, which performs sampling according to the bandwidth-limiting sampling theorem. A resulting discrete signal is supplied to an I-axis-component and Q-axis-component separating circuits, where the polarity of sample values is inverted for every other clock pulse with respect to each of the I and Q axes to thereby effect Hilbert transform. Resulting two orthogonal components on a phase plane are supplied to a complex coefficient filter.
30 Citations
8 Claims
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1. A radio receiving apparatus for a radio system in which carrier frequencies are channel-positioned at equal frequency intervals and which employs a quadrature demodulation scheme, said radio receiving apparatus comprising:
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means supplied with a received signal including a signal of a reception-desired channel, for selectively converting, into an intermediate frequency band, a frequency band including three channels on each of upper and lower sides of a center frequency that is an upper or lower end of the reception-desired channel or a boundary frequency with an adjacent channel thereof; means for sampling the frequency-converted signal at a frequency that is 16-fold a bandwidth of the reception-desired channel or 16-fold of a 1/2 frequency of a channel interval frequency of the radio system; means for extracting orthogonal components in a phase domain from the sampled signal; and means for extracting the signal of the reception-desired channel from a real-axis signal component and an imaginary-axis signal component of the extracted orthogonal components. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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Specification