Delay Line Oscillator Circuit for Spurious Mode Suppression

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Solution Overview

Problem

Delay line oscillators, particularly optoelectronic oscillators, suffer from unwanted adjacent modes that generate spurious signals, reducing system performance in radio equipment such as telecommunications and RADAR systems.

Innovation Solution

A spurious suppression circuit using a frequency discriminator, phase shifters, and a mixer to cancel phase modulation from parasitic modes, employing all-electrical or opto-electrical components to suppress unwanted oscillatory modes without additional fiber loops or optical components.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a delay line oscillator is used to achieve low phase noise and wide tuning bandwidth, then oscillatory conditions are met at multiple frequencies spaced by the reciprocal of the delay, but unwanted adjacent modes generate spurious signals that reduce system performance

Engineering Contradiction:

Improvesystem performanceVSAvoidspurious signals

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The patent converts the harmful spurious signals into useful information by using a frequency discriminator to detect them. The detected spurious signals are then processed through phase shifters and a mixer to generate cancellation signals that are fed back to suppress the original spurious signals, effectively converting the harmful effect into a beneficial suppression mechanism

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The patent implements a feedback mechanism where the output of the mixer is fed back to the input of the delay line oscillator. This feedback loop continuously monitors and suppresses spurious signals by adjusting the cancellation signals in real-time, thereby improving system performance through dynamic correction

Inventive Principle:

Principle #23Feedback

2Object-generated harmful factors

If additional fiber loops or optical components are used to suppress unwanted modes, then spurious signal suppression may be achieved, but device complexity increases

Engineering Contradiction:

Improvespurious signalsVSAvoidcircuit complexity

Core Design Contradiction:

Object-generated harmful factorsVSDevice complexity

Solution Approach 1:

The patent replaces complex optical components and fiber loops with an all-electrical suppression circuit. The electrical circuit uses a frequency discriminator, phase shifters, and a mixer to achieve spurious signal suppression without requiring additional optical infrastructure, thereby reducing device complexity while maintaining suppression effectiveness

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent introduces an intermediary electrical suppression circuit that acts as a mediator between the delay line oscillator and the output. This intermediary circuit processes the oscillator signal through electrical components to cancel spurious signals before output, avoiding the need for complex optical suppression mechanisms

Inventive Principle:

Principle #24Intermediary (Mediator)

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

Achieves significant spurious signal suppression, improving system performance by reducing spurious signals by up to 45 dB, enhancing sub-clutter visibility and bit error rate in RADAR and communication systems.

Implementation Method 1

a frequency discriminator having an insertion phase error proportional to an offset from a center frequency, the frequency discriminator configured to receive the discriminator input signal and provide a discriminator output having a plurality of oscillatory modes

Methodology Applied

Scientific EffectPhase detection:

Implementation Method 2

a first phase shifter configured to receive the discriminator output and apply a phase shift compensating for a mixer port phase differential

Methodology Applied

Scientific EffectPhase shifting:

Implementation Method 3

a mixer configured to provide a mixer output having a DC component proportional to a phase difference between inputs received at first and second mixer ports

Methodology Applied

Scientific EffectMixing:

Implementation Method 4

a second phase shifter configured to receive the mixer output and to phase modulate the second phase shifter input based on the DC component

Methodology Applied

Scientific EffectPhase modulation: Phase Modulation

Data Source

PatentUS20260074683A1Spurious suppression circuit

Publication Date: 2026.03.12 NANOWAVE TECHNOLOGIES INC

AI summary

A circuit and method for suppressing, in a delay line oscillator, modes spaced by the reciprocal of the oscillator delay that are not located at the center frequency of the mode selection filter that sets the oscillatory mode. The circuit may include: a frequency discriminator configured to receive a delay line output and provide a discriminator output having a plurality of oscillatory modes; a phase shifter configured to receive the discriminator output and compensate for a mixer port phase differential; a mixer configured to provide a mixer output having a DC component proportional to a phase difference between inputs received at first and second mixer ports; a second phase shifter configured to output a phase modulated signal; and a circuit coupler configured to provide a first circuit coupler output as an output of the circuit, and to provide a second circuit coupler output as an input to the delay line.