US3913013A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Spectrum analyzer
Assignee: United States Department of the Army
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Filing: 1974-07-30
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Granted: 1975-10-14
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Expires: 1994-07-30
Abstract
Abstract A spectrum analyzer for measuring near-carrier spectrums utilizes only closed loop operation for measuring the spectral energy. Frequency modulated sidebands near a microwave frequency carrier can be examined without introducing any frequency translation byproducts which cannot be cancelled out of the measurement. A highly stable oscillator operating at a relatively low frequency has an output mixed with the input microwave carrier to provide a modulated output signal to a second mixer. The modulated signal is again mixed with the microwave carrier to eliminate the carrier from the spectrum, having the spectrum superimposed on the oscillator signal. The superimposed sideband spectrum is then picked off for observation or measurement.
Inventors
- 👤 Thomas A Barley
- 👤 Jr Gustaf J Rast
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 21:33
CPC Classifications
G; G01; G01R; G01R23/00; G01R23/16; G01R23/165
Claims Analysis
Total Claims: 9
Claim 1
Independent Claim
147 words
Apparatus for measuring frequency modulated spectral energy comprising: first and second frequency mixers, an output of said first mixer being coupled as a first input of said second mixer; a stable local oscillator having an output coupled as a first input of said first mixer, a radio frequency input for receiving radio frequency input signals, a directional coupler having an input and first and second outputs, a tunable bandpass filter coupled between said radio frequency input and said directional coupler input for selectably tuning a desired radio frequency input signal from an octave band of frequencies to be analyzed, said directional coupler outputs being coupled to respective second inputs of said first and second mixers for selectably mixing the radio frequency input signal with an output signal of said oscillator and thereby obtaining the oscillator frequency with RF spectral sidebands as an output of said second mixer.
Claim 2
Dependent Claim
147 words
Apparatus for measuring frequency modulated spectral energy comprising: first and second frequency mixers, an output of said first mixer being coupled as a first input of said second mixer; a stable local oscillator having an output coupled as a first input of said first mixer, a radio frequency input for receiving radio frequency input signals, a directional coupler having an input and first and second outputs, a tunable bandpass filter coupled between said radio frequency input and said directional coupler input for selectably tuning a desired radio frequency input signal from an octave band of frequencies to be analyzed, said directional coupler outputs being coupled to respective second inputs of said first and second mixers for selectably mixing the radio frequency input signal with an output signal of said oscillator and thereby obtaining the oscillator frequency with RF spectral sidebands as an output of said second mixer.
Claim 3
Dependent Claim
54 words
Apparatus for measuring frequency modulated spectral energy as set forth in claim 1 and further comprising a phase detector having a first input coupled to the output of said local oscillator and a second input coupled to the output of said second mixer for obtaining the RF spectral sidebands as a differential output signal.
Claim 4
Dependent Claim
60 words
Apparatus for measuring frequency modulated spectral energy as set forth in claim 2 and further comprising a hybrid junction having an input connected to the output of said local oscillator, a first output of said junction being coupled to the first input of said first mixer and a second output being coupled to the first input of said phase detector.
Claim 5
Dependent Claim
74 words
Apparatus for measuring frequency modulated spectral energy as set forth in claim 3 and further comprising a first phase shifter connected between said directional coupler and said second input of said first mixer for aligning the phase of said RF input signal with the RF input signal coupled directly to the second input of said second mixer; and a second phase shifter coupled between the first input of said phase detector and said hybrid.
Claim 6
Dependent Claim
67 words
Apparatus for measuring frequency modulated spectral energy as set forth in claim 4 and further comprising a first IF amplifier connected between the output of said second mixer and the second input of said phase detector, and a second IF amplifier connected between the second output of said hybrid and the input of said phase shifter for equalizing the level of amplitude of the oscillator output signal.
Claim 7
Dependent Claim
67 words
Apparatus as set forth in claim 5 and further comprising A first isolator connected between said first mixer and said directional coupler, a second isolator connected between said second mixer and said directional coupler, a third isolator connected between said first mixer and said hybrid, and a fourth isolator connected between said first mixer and said second mixer for preventing feedback of unwanted signals into respective stages.
Claim 8
Dependent Claim
44 words
Apparatus as set forth in claim 6 and further comprising a series connected tunable filter and RF amplifier coupled between said first mixer output and the first input of said second mixer for enhancing the oscillator modulated, radio frequency output of said first mixer.
Claim 9
Dependent Claim
67 words
Apparatus as set forth in claim 7 and further comprising a third mixer coupled between said local oscillator output and said hybrid input, and an audio oscillator having an output connected to a second input of said mixer for coupling a calibrating signal thereto; said third mixer combining the output of said oscillators to provide audio sidebands on the output IF signal for providing said calibrating signal.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1978-10-13 | 1979-04-14 | 1979-10-14 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-10-13 | 1983-04-14 | 1983-10-14 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-10-13 | 1987-04-14 | 1987-10-14 | $7700.00 | Window Closed / Lapsed |