FREQUENCY SYNTHESISER

• US 3,772,681 A
• Filed: 10/12/1971
• Issued: 11/13/1973
• Est. Priority Date: 10/14/1970
• Status: Expired due to Term

• Current Assignee: Gerald David Skingle
• Original Assignee: Gerald David Skingle
• Inventors: Skingle, Gerald David
• Primary Examiner(s): Wilbur, Maynard R.
• Assistant Examiner(s): Glassman, Jeremiah
• Application Number:
  US05/188,367
• Time in Patent Office: 763 Days
• Field of Search: 340/347DA 321/1.7 324/85 325/9,13 328/14,16,23,27,181,185,133 235/154,197 329/110
• US Class Current: 708/272
• CPC Class Codes: G06F 1/0353 by using symmetrical properties of the function, e.g. using most significant bits for quadrant control
• CPC Class Codes: H04J 1/06 Arrangements for supplying the carrier waves ; Arrangements for supplying synchronisation signals synchronisation in general H03B; frequency multiplication H03B19/00, H03B21/00; mixing H03D7/00, H03D9/00; carrier supply H04L5/10
• CPC Class Codes: H04L 27/2003 for continuous phase modulation frequency shift keying H04L27/10
• CPC Class Codes: H04L 5/06 the signals being represented by different frequencies combined with time-division multiplexing H04L5/26

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.

Claims

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.

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.

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.

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.

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.

6. A frequency synthesizer as claimed in claim 5 in which the memoRy output converter signal is applied to a multiplexed digital filter.

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.

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.

9. A frequency synthesizer as claimed in claim 8 in which the digital memory consists of a read-only memory of sine table values.

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.