FREQUENCY SYNTHESISER
First Claim
1. A frequency synthesizer for providing a signal having a predetermined continuous function analogue waveform, said synthesizer comprising a source of clock frequency signals;
- a digital memory arranged to contain the amplitude values of a series of incremental points on the waveforms;
selection means for composing an address for said digital memory and applying said address to said memory at a clock frequency derived from said clock frequency source, said selection means being arranged to compose said address from a plurality of data input signals, a first set of which is preset, and a second set of which is derived from an output of said memory; and
digital to analogue converter means arranged to produce sample pulses and said converter means being coupled to a filter means to convert the series of sample pulses representing incremental points on the waveform to a continuous waveform having a predetermined selectable frequency.
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Accused Products
Abstract
A frequency synthesiser, which may be used in Modem systems MCVFT systems and F.M. receivers, produces a predetermined waveform signal by using the digital values of incremental points on the waveform, which values are selected in a sequence determined by a address selection arrangement from a digital storage memory of the read-only type. The output from the readonly memory is a digital signal which may be filtered and distributed to a number of channels or it may be passed by way of a digital-to-analogue converter to generate the predetermined phase continuous waveform.
41 Citations
10 Claims
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1. A frequency synthesizer for providing a signal having a predetermined continuous function analogue waveform, said synthesizer comprising a source of clock frequency signals;
- a digital memory arranged to contain the amplitude values of a series of incremental points on the waveforms;
selection means for composing an address for said digital memory and applying said address to said memory at a clock frequency derived from said clock frequency source, said selection means being arranged to compose said address from a plurality of data input signals, a first set of which is preset, and a second set of which is derived from an output of said memory; and
digital to analogue converter means arranged to produce sample pulses and said converter means being coupled to a filter means to convert the series of sample pulses representing incremental points on the waveform to a continuous waveform having a predetermined selectable frequency.
- a digital memory arranged to contain the amplitude values of a series of incremental points on the waveforms;
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2. A frequency synthesizer as claimed in claim 1 in which selection means is an arithmetic unit including a digital signal adder arranged to add a predetermined increment derived from said first set of inputs to each consecutive memory address.
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3. A frequency synthesizer as claimed in claim 2 in which said digital memory is arranged to store the incremental amplitude values of a sine waveform.
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4. A frequency synthesizer for providing a phase continuous function signal when switched between a number of predetermined frequencies, said synthesizer comprising:
- a clock frequency source;
a digital read-only memory arranged to contain the amplitude values of a series of incremental points on a sine waveform;
selection means for composing an address for said read-only memory and applying said address to the memory at a clock frequency obtained from the clock frequency source;
data input switching means controlling the selection means so as to address the desired amplitude increment in said memory; and
a memory output converter arranged to apply the selected predetermined amplitude sample to a filter.
- a clock frequency source;
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5. A frequency synthesizer as claimed in claim 4 in which a plurality of channels are multiplexed by means of an input multiplexer driven at the clock frequency from said clock frequency source.
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6. A frequency synthesizer as claimed in claim 5 in which the memoRy output converter signal is applied to a multiplexed digital filter.
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7. A frequency synthesizer as claimed in claim 5 in which the signal from said memory output converter is fed to an output channel distributor and said signal from the memory output converter is translated to an analogue signal in a digital-to-analogue converter.
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8. A frequency synthesizer for providing a continuous function signal having a predetermined waveform said synthesizer comprising:
- a clock frequency source;
a digital memory having a multiple bit word store arranged to contain the digital amplitude values of incremental points on the waveform;
selection means for composing an address for said digital memory and applying said address to the memory at a clock frequency produced from said clock frequency source; and
a digital-to-analogue converter means for producing the predetermined analogue waveform from the digital output of said memory so as to generate time-staggered amplitude values for a plurality of channels.
- a clock frequency source;
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9. A frequency synthesizer as claimed in claim 8 in which the digital memory consists of a read-only memory of sine table values.
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10. A frequency synthesizer as claimed in claim 9 including a data input section and an inhibit selection unit arranged to inhibit those inputs to said data input section which are not required.
Specification