EP0335037A1
Expired / Lapsed
EP
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Direct conversion radio
Assignee: STC PLC
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Filing: 1988-10-17
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Granted: —
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Expires: 2008-10-17
Abstract
Abstract A digital direct-conversion or zero-IF radio receiver in which analogue RF signals are down-converted to form a complex pair of analogue signals (I and Q) which are separately digitised and the digitised signals are digitally processed to produce an output signal. The digitising is performed by separate I and Q oversampling analogue-to-digital converters 17, 17a (ADC) operating at sampling rates not less than 10 times the Nyquist rate. The output of each oversampling ADC is applied to respective I and Q digital filters 18, 18a. The outputs of the I and Q digital filters are fed to a digital signal processor 19 to produce the output signal.
Inventors
- 👤 John Masterton
- 👤 Philip Stuart Gaskell
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-09 08:42
CPC Classifications
H; H03; H03D; H03D1/00; H03D1/22; H03D1/2245; H03C; H03C1/00; H03D3/00; H03D3/007; H03C2200/00; H03C2200/0037; H03C2200/0058; H03C2200/0079; H03C3/00; H03C3/38; H03C3/40; H03D2200/00; H03D2200/0041; H03D2200/005; H03D2200/0052; H03D2200/0054; H03D2200/0056; H03D2200/006; H03D3/006
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
44 words
A digital direct-conversion or zero-IF radio in which analogue RF signals are converted to or from digital baseband signals in quadrature, characterised in that the analogue-to-digital or digital-to-analogue conversion is performed by oversampling converters operating at sampling rates in excess of the Nyquist rate.
Claim 2
Dependent Claim
44 words
A digital direct-conversion or zero-IF radio in which analogue RF signals are converted to or from digital baseband signals in quadrature, characterised in that the analogue-to-digital or digital-to-analogue conversion is performed by oversampling converters operating at sampling rates in excess of the Nyquist rate.
Claim 3
Dependent Claim
103 words
A digital direct-conversion or zero-IF radio receiver in which analogue RF signals are down-converted to form analogue quadrature baseband (I and Q) signals which are separately digitised and these digitised signals are digitally processed to produce an output signal, characterised in that the digitising is performed by separate I and Q oversampling analogue-to-digital converters (ADC) operating at sampling rates not less than 10 times the Nyquist rate, the output of each oversampling ADC being applied to respective I and Q digital filters, the outputs of the I and Q digital filters being fed to a digital signal processor to produce the output signal.
Claim 4
Dependent Claim
103 words
A digital direct-conversion or zero-IF radio receiver in which analogue RF signals are down-converted to form analogue quadrature baseband (I and Q) signals which are separately digitised and these digitised signals are digitally processed to produce an output signal, characterised in that the digitising is performed by separate I and Q oversampling analogue-to-digital converters (ADC) operating at sampling rates not less than 10 times the Nyquist rate, the output of each oversampling ADC being applied to respective I and Q digital filters, the outputs of the I and Q digital filters being fed to a digital signal processor to produce the output signal.
Claim 5
Dependent Claim
40 words
A receiver according to claim 2 characterised in that the I and Q filters each include means for reducing the high sample rate of the ADC output to a low sample rate of less than 10 times the Nyquist rate.
Claim 6
Dependent Claim
24 words
A receiver according to claim 2 or 3 characterised in that the ADC includes frequency-dependent feedback whereby the noise is reduced at baseband frequencies.
Claim 7
Dependent Claim
20 words
A receiver according to claim 2, 3 or 4 characterised in that the ADC comprises a pulse density modulator (PDM).
Claim 8
Dependent Claim
16 words
A receiver according to claim 5 characterised in that the PDM is a clocked D-type flip-flop.
Claim 9
Dependent Claim
100 words
A digital direct-conversion or zero-IF radio transmitter characterised in that digitised quadrature baseband I and Q signals from a digital baseband modulator are separately converted by digital oversampling means into streams of data words of reduced wordwidth and applied to respective digital-to-analogue converters (DAC) the outputs of which are passed through respective reconstruction filters and are separately mixed with two quadrature local oscillator signals running at the transmitter carrier frequency, the mixer outputs being combined to form an analogue RF output, characterised in that the sampling rate of the oversampling means is not less than 10 times the Nyquist rate.
Claim 10
Dependent Claim
100 words
A digital direct-conversion or zero-IF radio transmitter characterised in that digitised quadrature baseband I and Q signals from a digital baseband modulator are separately converted by digital oversampling means into streams of data words of reduced wordwidth and applied to respective digital-to-analogue converters (DAC) the outputs of which are passed through respective reconstruction filters and are separately mixed with two quadrature local oscillator signals running at the transmitter carrier frequency, the mixer outputs being combined to form an analogue RF output, characterised in that the sampling rate of the oversampling means is not less than 10 times the Nyquist rate.
Claim 11
Dependent Claim
14 words
A transmitter according to claim 7 characterised in that the DAC's are one-bit DAC's.
References Cited (Backward Citations)
EP0143539A2
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EP0180339A2
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EP0186568A2
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EP0197708A2
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WO1986005936A1
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EP0310796A1
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