# US 6,295,020 B1 · Master frequency generator > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 6,295,020 B1 - Document ID: US6295020B1 - Status: Granted - Kind: B1 - Application number: 09/379,645 - Filed: 1999-08-23 - Granted: 2001-09-25 - Earliest claimed: 1999-08-23 - Assignees: Lockheed Martin Corporation - Inventors: Michael Koechlin - Web page: https://patentgrep.com/patent/US6295020B1 ## CPC - H03B 21/02: by plural beating, i.e. for frequency synthesis {; Beating in combination with multiplication or division of frequency (digital frequency synthesis using a ROM G06F1/02; digital frequency synthesis in general H03K; indirect frequency synthesis using a PLL H03L7/16)} - H03B: GENERATION OF OSCILLATIONS, DIRECTLY OR BY FREQUENCY-CHANGING, BY CIRCUITS EMPLOYING ACTIVE ELEMENTS WHICH OPERATE IN A NON-SWITCHING MANNER; GENERATION OF NOISE BY SUCH CIRCUITS (generators adapted for electrophonic musical instruments G10H; masers or lasers H01S; generation of oscillations in plasma H05H) ## Abstract A system is provided for generating multiple frequencies in a specified frequency band, with a specified step size between frequencies, in which the spectral purity of the frequencies is assured. The switching speed between frequencies is very fast, limited only by the speed of the switches used. In one embodiment, only five tones are generated as the base for the rest of the synthesis, in which the relationship of the five tones is f0+/−⅛f0 and +/−{fraction (1/16)}f0. The subject system in one embodiment, utilizes a channel synthesizer and a doppler offset synthesizer which may be utilized in air defense systems for generating the transmit channels to be able to permit a missile seeker to transmit a signal at the appropriate frequency. In one embodiment, spectral purity is achieved by providing a number of stages of up converting, expanding, and dividing down of an input signal. ## Claims ### Claim 1 A system for generating a plurality of substantially spur-free frequencies for use in the generation of substantially spur-free RF signals in which at least some of the plurality of frequencies are preselected, comprising: a master frequency generator for generating a plurality of tones; and a first mixer, including a channel synthesizer for mixing selected ones of said plurality of tones thereby generating one of said preselected frequencies, and a frequency offset synthesizer for mixing said one of said preselected frequencies with a predetermined frequency offset signal. ### Claim 2 (depends on 1) A system in accordance with claim 1, wherein said plurality of tones is five tones, and wherein a relationship between said five tones is f0, f0+⅛f0, f0−⅛f0, f0+{fraction (1/16)}f0, and f0−{fraction (1/16)}f0. ### Claim 3 (depends on 1) A system in accordance with claim 1, wherein said plurality of tones is five tones, and wherein said master frequency generator includes a reference oscillator, a divide-by-8 divider coupled to an output of said reference oscillator, a divide-by-2 divider coupled to an output of said divide-by-8 divider, a combiner for combining the output of said divide-by-8 divider and an output of said divide-by-2 divider, a second mixer for mixing an output of said combiner and the output of said reference frequency oscillator, and a separator, coupled to an output of said second mixer, for separating the output of said second mixer into four of said five tones, wherein the fifth of said five tones is the output of said reference oscillator. ### Claim 4 (depends on 3) A system in accordance with claim 3, wherein said separator includes a quadraplexer. ### Claim 5 (depends on 1) A system in accordance with claim 1, and further including a missile seeker having a millimeter radar transmitter for transmitting radar signals in one of a plurality of frequency channels, wherein said channel synthesizer is capable of generating a plurality of frequencies from said plurality of tones, and wherein said first mixer includes a reference oscillator and an up-converter coupled to both said reference oscillator and said channel synthesizer, said first mixer generating one of said RF signals, said one of said RF signals having a frequency in one of said plurality of frequency channels specified by said channel synthesizer. ### Claim 6 (depends on 1) A system in accordance with claim 1, wherein the system further includes up-conversion by mixing followed by a divider resulting in substantially spur-free RF signals. ### Claim 7 (depends on 6) A system in accordance with claim 6, wherein said frequency offset synthesizer is a Doppler offset synthesizer, and wherein at least one of said preselected frequencies generated by said channel synthesizer is mixed with a predetermined frequency offset signal from said Doppler offset synthesizer. ### Claim 8 (depends on 1) A system in accordance with claim 1, wherein said plurality of tones is five tones, and wherein a relationship between said five tones is f0, f0+{fraction (1+L /x)}f0, f0−{fraction (1+L /x)}f0, f0+{fraction (1/2+L x)}f0, and f0−{fraction (1/2+L x)}f0. ### Claim 9 (depends on 1) A system in accordance with claim 1, wherein a relationship between said plurality of tones is a non-integer multiple. ### Claim 10 (depends on 1) A system in accordance with claim 1, wherein said plurality of tones is at least five tones, and wherein a relationship between said five tones is a non-integer multiple. ### Claim 11 (depends on 1) A system in accordance with claim 1, wherein a number of the substantially spur-free frequencies generated satisfies an equation F=41/128 FA+K/4(N1/1+N2/2+N3/8+N4/32) where F is the number of substantially spur-free frequencies to be generated, FA is the lowest tone, K is the tone spacing, and N is one of 0 and an integer. ### Claim 12 (depends on 1) A system in accordance with claim 1, wherein said master frequency generator is provided with a master frequency oscillator and said master frequency oscillator generates said plurality of tones. ### Claim 13 (depends on 1) A system in accordance with claim 1, wherein there is a non-harmonic relationship between ones of said plurality of tones. ### Claim 14 (depends on 1) A system in accordance with claim 1, wherein said plurality of tones comprises at least one pair of tones symmetrically offset about a central one of said plurality of tones, and wherein there is a non-harmonic relationship between said plurality of tones. ### Claim 15 (depends on 1) A system in accordance with claim 1, wherein said plurality of tones comprises at least two pair of tones symmetrically offset about a central one of said plurality of tones, and wherein one pair of said at least two pair of tones has a non-harmonic relationship with respect to another pair of said at least two pair of tones and said central one of said plurality of tones.