High precision, low phase noise synthesizer with vector modulator

• US 6,683,918 B2
• Filed: 02/19/2002
• Issued: 01/27/2004
• Est. Priority Date: 12/13/1994
• Status: Expired due to Fees

• Current Assignee: Hughes Electronics Corporation (Rtx Corporation)
• Original Assignee: Hughes Electronics Corporation (Rtx Corporation)
• Inventors: Tang, Hai, Jackson, Thomas, Bourner, David
• Primary Examiner(s): TSE, YOUNG TOI
• Application Number:
  US10/079,615
• Publication Number:
  US 20020094036A1
• Time in Patent Office: 707 Days
• Field of Search: 375/279, 375/282, 375/295, 375/305, 375/306, 375/307, 375/308, 455/76, 327/105, 332/103, 332/144, 332/145, 332/163, 332/127, 332/128
• US Class Current: 375/308
• CPC Class Codes: H03B 27/00 Generation of oscillations providing a plurality of outputs of the same frequency but differing in phase, other than merely two anti-phase outputs
• CPC Class Codes: H03B 28/00 Generation of oscillations by methods not covered by groups H03B5/00 - H03B27/00, including modification of the waveform to produce sinusoidal oscillations analogue function generators for performing computing operations G06G7/26; use of transformers for conversion of waveform in ac-ac converters H02M5/18
• CPC Class Codes: H03C 3/0908 using a phase locked loop
• CPC Class Codes: H03C 3/0983 containing in the loop a mixer other than for phase detection
• CPC Class Codes: H03C 5/00 Amplitude modulation and angle modulation produced simultaneously or at will by the same modulating signal H03C7/00 takes precedence
• CPC Class Codes: H03D 7/00 Transference of modulation from one carrier to another, e.g. frequency-changing H03D9/00, H03D11/00 take precedence; dielectric amplifiers, magnetic amplifiers, parametric amplifiers used as a frequency-changers H03F
• CPC Class Codes: H03L 7/1806 the frequency divider comprising a phase accumulator generating the frequency divided signal
• CPC Class Codes: H03L 7/23 with pulse counters or frequency dividers

Abstract

An apparatus for generating a modulated signal which includes a modulator operative for receiving a first signal and input data signals, and modulating the first signal in accordance with the input data signals so as to produce a modulated reference signal; a first frequency divider coupled to the modulator output, operative to reduce the frequency of the modulated reference signal by a predetermined factor; a signal generator operative to produce a second signal; a first mixer having a first input coupled to an output of the first frequency divider and a second input coupled to the output of the signal generator. The first mixer operates to frequency translate the modulated reference signal by an amount equal to the frequency of the second signal. In addition, the signal generator of the present invention contains a direct digital synthesizer coupled to a second phase lock loop which operates to up-convert the output signal of the DDS to the microwave region. The feedback network of the second phase lock loop utilizes frequency translation to down-convert the output signal in order to close the loop.

Claims

1. An apparatus for generating a modulated signal comprising:

a modulator operative for receiving a first signal and input data signals, and modulating said first signal in accordance with said input data signals so as to p roduce a modulated reference signal;

a first frequency divider coupled to an output of said modulator, said frequency divider operative to reduce the frequency of said modulated reference signal by a predetermined factor;

a signal generator operative to produce a second signal;

a first mixer having a first and second input, said first input coupled to an output of said first frequency divider and said second input coupled to an output of said signal generator, said first mixer operative to frequency translate said modulated reference signal by an amount equal to the frequency of said second signal to generate said modulated signal;

a local oscillator for generating an rf signal; and

a first phase lock loop for multiplying the frequency of said rf signal by a predetermined amount so as to generate said first signal, said first phase lock loop having an input for receiving said rf signal, and a feedback network comprising a second and third frequency divider coupled in series; and

wherein said signal generator comprises;

a direct digital synthesizer for generating a tunable signal, said synthesizer having a first and second input, said first input operative to receive a tuning frequency signal, said second input operative to receive a first reference signal; and

a second phase lock loon for multiplying the frequency of said tunable signal by a predetermined amount so as to generate said second signal; and

wherein said second phase lock loop comprises a feedback network including a second mixer having a first and second input, said first input coupled to an output of said first phase lock loop and said second input coupled to a second reference signal, said second mixer operative to frequency translate said second reference signal by an amount equal to the frequency of said output of said first phase lock loop.

2. An apparatus for generating a modulated signal according to claim 1, wherein said second input of said second mixer is coupled to an output of said second frequency divider of said first phase lock loop.

3. An apparatus for generating a modulated signal according to claim 1, wherein said second input of said direct digital synthesizer is coupled to an output of said second frequency divider of said first phase lock loop.

4. A method for generating a modulated signal comprising:

generating a first signal and input data signals;

modulating said first signal in accordance with said input data signals so as to produce a modulated reference signal;

frequency dividing said modulated reference signal so as to reduce the frequency of said modulated reference signal by a predetermined factor;

generating a second signal by means of a signal generator;

frequency translating said modulated reference signal by an amount equal to the frequency of said second signal to generate said modulated signal;

generating an if signal by means of a local oscillator; and

multiplying the frequency of said rf signal by a predetermined amount by a first phase lock loon so as to generate said first signal, said first phase lock loon having an input for receiving said if signal, and a feedback network comprising a frequency divider; and

wherein said signal generator comprises;

a direct digital synthesizer for generating a tunable signal, said synthesizer having a first and second input, said first input operative to receive a tuning frequency signal, said second input operative to receive a first reference signal; and

a second phase lock loon for multiplying the frequency of said tunable signal by a predetermined amount so as to generate said second signal; and

wherein said second phase lock loop comprises a feedback network including a mixer having a first and second input, said first input coupled to an output of said first phase lock loop and said second input is coupled to a second reference signal, said mixer operative to frequency translate said second reference signal by an amount equal to the frequency of said output of said first phase lock loop.

5. A method for generating a modulated signal according to claim 4, wherein said second input of said mixer is coupled to an output at said frequency divider of said first phase lock loop.

6. A method for generating a modulated signal according to claim 4, wherein said second input of said direct digital synthesizer is coupled to an output of said frequency divider of said first phase lock loop.