Improvements relating to signal processing
First Claim
1. A method of sampling a radio frequency signal comprising:
- (i) receiving the radio frequency signal;
(ii) modulating an optical signal with the radio frequency signal to generate a modified optical signal;
(iii) modulating the modified optical signal with an oscillator signal to generate a modulated optical signal;
(iv) converting the optical signal to a radio frequency electrical signal;
(v) applying a filter to the radio frequency electrical signal to select an intermediate frequency signal, the filter having an intermediate pass band and an intermediate roll-off, the intermediate pass band and the intermediate roll-off in combination defining an intermediate frequency band having a first bandwidth; and
(vi) sampling the intermediate frequency signal at a sampling frequency using a number of analogue-to-digital converters that alternately sample the intermediate frequency signal;
the oscillator signal and the sampling frequency in combination being arranged such that the intermediate frequency band is defined between consecutive multiples of half of the sampling frequency.
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Accused Products
Abstract
A method of sampling a radio frequency signal comprises: receiving the radio frequency signal; modulating an optical signal with the radio frequency signal and an oscillator signal to generate a modulated signal; applying a filter to the modulated signal to generate an intermediate frequency signal, the filter having an intermediate pass band and an intermediate roll-off, the intermediate pass band and the intermediate roll-off in combination defining a intermediate frequency band having a first bandwidth; and sampling the intermediate frequency signal at a sampling frequency using a number of optically interleaved analog-to-digital converters. The oscillator signal and the sampling frequency in combination are arranged such that the intermediate frequency band is defined between consecutive multiples of half of the sampling frequency.
Corresponding apparatus for sampling a radio frequency signal is also disclosed. Apparatus and methods for synthesizing a radio frequency signal, using similar techniques to the above, are also disclosed.
35 Citations
26 Claims
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1. A method of sampling a radio frequency signal comprising:
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(i) receiving the radio frequency signal; (ii) modulating an optical signal with the radio frequency signal to generate a modified optical signal; (iii) modulating the modified optical signal with an oscillator signal to generate a modulated optical signal; (iv) converting the optical signal to a radio frequency electrical signal; (v) applying a filter to the radio frequency electrical signal to select an intermediate frequency signal, the filter having an intermediate pass band and an intermediate roll-off, the intermediate pass band and the intermediate roll-off in combination defining an intermediate frequency band having a first bandwidth; and (vi) sampling the intermediate frequency signal at a sampling frequency using a number of analogue-to-digital converters that alternately sample the intermediate frequency signal; the oscillator signal and the sampling frequency in combination being arranged such that the intermediate frequency band is defined between consecutive multiples of half of the sampling frequency. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. Sampling apparatus for sampling a radio frequency signal, the apparatus comprising:
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(i) a receiver configured to receive a radio frequency signal; (ii) a modulator configured to modulate an optical signal with the radio frequency signal to generate a modified optical signal, and then to modulate the modified optical signal with an oscillator signal to generate a modulated optical signal; (iii) a converter configured to convert the modulated optical signal to a radio frequency electrical signal; (iv) a filter operable to filter the radio frequency electrical signal to select an intermediate frequency signal, the filter having an intermediate pass band and an intermediate roll-off, the intermediate pass band and the intermediate roll-off in combination defining an intermediate frequency band having a first bandwidth; and (v) a sampler configured to sample the intermediate frequency signal at a sampling frequency; the oscillator signal and the sampling frequency in combination being arranged such that the intermediate frequency band is defined between consecutive multiples of half of the sampling frequency. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19, 20)
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21. A method of synthesising a radio frequency signal comprising:
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(i) generating an intermediate analogue frequency signal from a digital signal by applying the digital signal to a number of digital to analogue converters, alternately accessing the outputs of the digital to analogue converters using a commutator switch to interleave the outputs of the digital to analogue converters and thereby generate a combined D/A output, and applying a band pass filter to the combined D/A output; (ii) generating a modified optical signal by modulating an optical signal with the intermediate analogue frequency signal; (iii) generating a modulated optical signal by modulating the modified optical signal with an oscillator signal; (iv) converting the modulated optical signal to a radio frequency electrical signal; and (v) applying a first filter to the radio frequency electrical signal to select the radio-frequency signal, the first filter having a first pass band and a first roll-off, and the first pass band and the first roll-off in combination defining a first bandwidth, wherein an effective sample rate of the digital signal is selected such that the first bandwidth is less than, or equal to the bandwidth defined between consecutive multiples of half the effective sampling rate. - View Dependent Claims (22)
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23. Synthesising apparatus for synthesising a radio frequency signal, the apparatus comprising:
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(i) an intermediate frequency generator configured to generate an intermediate frequency signal from a digital signal by applying the digital signal to a number of digital to analogue converters, alternately accessing the outputs of the digital to analogue converters using a commutator switch to interleave the outputs of the digital to analogue converters and thereby generate a combined D/A output, and applying a band pass filter to the combined D/A output; (ii) a modulator configured to modulate an optical signal with the intermediate frequency signal to generate a modified optical signal, and then to modulate the modified optical signal with an oscillator signal to generate a modulated optical signal; (iii) a converter configured to convert the modulated optical signal to a radio frequency electrical signal; and (iv) a first filter operable to select the radio-frequency signal from the radio frequency electrical signal, the first filter having a first pass band and a first roll-off, and the first pass band and the first roll-off in combination defining a first bandwidth, wherein an effective sample rate of the digital signal is selected such that the first bandwidth is less than, or equal to the bandwidth defined between consecutive multiples of half the effective sampling rate. - View Dependent Claims (24)
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25. Apparatus comprising:
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a) a sampling apparatus for sampling a first radio frequency signal, the sampling apparatus comprising; (i) a receiver to receive the first radio frequency signal; (ii) a first modulator to modulate a first optical signal with the first radio frequency signal and a first oscillator signal to generate a first modulated signal; (iii) a first filter operable to filter the first modulated signal to select a first intermediate frequency signal, the first filter having a first intermediate pass band and a first intermediate roll-off, the first intermediate pass band and the first intermediate roll-off in combination defining a first intermediate frequency band having a first bandwidth; and (iv) a sampler to sample the first intermediate frequency signal at a first sampling frequency to create a digital signal; the first oscillator signal and the first sampling frequency in combination being arranged such that the first intermediate frequency band is defined between consecutive multiples of half of the first sampling frequency; b) a synthesising apparatus for synthesising a second radio frequency signal, the synthesising apparatus comprising; (i) an intermediate frequency generator to generate a second intermediate frequency signal from the digital signal by applying the digital signal to a number of digital to analogue converters and alternately accessing the outputs of the digital to analogue converters; (ij) a second modulator to modulate a second optical signal with the second intermediate frequency signal and a second oscillator signal; and (iii) a second filter operable to select the second radio-frequency signal from the second modulated signal. the second filter having a second pass band and a second roll-off, and the second pass band and the second roll-off in combination defining a second bandwidth, wherein an effective sampling rate of the digital signal is selected such that the second bandwidth is less than, or equal to the bandwidth defined between consecutive multiples of half the effective sampling rate; and c) a digital radio frequency memory; the sampling apparatus, synthesising apparatus and digital radio frequency memory being operable in combination to receive the first radio frequency signal, digitally process the first radio frequency signal to create the second radio frequency signal, and to transmit the second radio frequency signal.
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26. A method of sampling a radio frequency signal comprising:
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(i) receiving the radio frequency signal; (ii) modulating a signal with the radio frequency signal to generate a modified signal; (iii) modulating the modified signal with an oscillator signal to generate a modulated signal; (iv) applying a filter to the modulated signal to generate an intermediate frequency signal, the filter having an intermediate pass band and an intermediate roll-off, the intermediate pass band and the intermediate roll-off in combination defining an intermediate frequency band having a first bandwidth; and (v) sampling the intermediate frequency signal at a sampling frequency;
the oscillator signal and the sampling frequency in combination being arranged such that the intermediate frequency band is defined between consecutive multiples of half of the sampling frequency.
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Specification