Signal-to-Noise Ratio Generator Circuit for Receiver Testing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing electronic test systems face challenges in maintaining a controlled signal-to-noise ratio for evaluating the performance of electronic communication systems, particularly in radio receivers, due to fluctuations in received signal amplitude and operating temperature.
Innovation Solution
An electronic circuit design that generates a controlled signal-to-noise ratio by using two mixers and filters to create an intermediate frequency signal and an image frequency signal from the same RF input, ensuring the ratio is independent of signal amplitude and temperature through equal mixer conversion loss for both frequencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a noise source is used to create a known signal-to-noise ratio with received RF signal, then the receiver performance can be tested, but the signal-to-noise ratio becomes difficult to control due to fluctuations in received signal levels and operating temperature
Solution Approach 1:
The patent introduces an intermediary signal processing path that generates a test signal independent of the received RF signal. Instead of directly combining the noisy received signal with a reference signal, the system uses a clean local oscillator signal that is split into two paths: one path goes through the device under test, and the other path serves as a clean reference. This intermediary approach eliminates the problem of received signal fluctuations affecting the signal-to-noise ratio.
Solution Approach 2:
The patent creates a copy of the local oscillator signal to serve as a clean reference signal. By copying the oscillator signal rather than using the received RF signal as the reference, the system ensures that the reference remains stable and unaffected by received signal variations. This copied reference signal is then used to generate the intermediate frequency signal for comparison with the noisy output.
2Measurement precision
If the noise source is combined with received RF signal to create a known signal-to-noise ratio, then receiver testing is enabled, but the system becomes sensitive to operating temperature changes
Solution Approach 1:
The patent uses a clean local oscillator signal as an intermediary reference that is insensitive to temperature changes. By basing the signal-to-noise ratio calculation on this temperature-stable reference signal rather than on the received RF signal or thermal noise source, the system achieves temperature independence. The intermediary reference signal maintains its properties across temperature variations.
Solution Approach 2:
The patent changes the fundamental parameter used for signal-to-noise ratio calculation from thermal noise (which is temperature-dependent according to kTB) to a clean intermediate frequency signal derived from a stable local oscillator. This parameter change from thermal-based reference to oscillator-based reference eliminates temperature sensitivity in the measurement system.
3Measurement precision
If received signal levels fluctuate, then the signal-to-noise ratio cannot be maintained at a known level, but increasing signal level control complexity is required
Solution Approach 1:
The patent copies the local oscillator signal to create a stable reference that does not require active control. Instead of copying and actively controlling the received signal level (which would be complex), the system copies the clean oscillator signal and uses it as the reference. This approach achieves signal-to-noise ratio stability without requiring complex signal level control circuitry.
Solution Approach 2:
The patent allows the clean local oscillator signal to serve itself as the reference without requiring external adjustment or control mechanisms. The oscillator naturally provides a stable frequency and amplitude reference that requires no active control systems, thereby achieving signal-to-noise ratio stability through self-service rather than complex control circuitry.
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
The circuit provides a stable signal-to-noise ratio that is insensitive to fluctuations in RF signal amplitude and operating temperature, allowing for reliable performance evaluation of electronic devices.
Implementation Method 1
A first mixer is coupled to the RF input and provides a first output signal that includes two key components; the first being a signal at the (RF signal frequency plus the first local oscillator signal frequency) and the second being a signal at the (RF signal frequency minus the first local oscillator signal frequency)
Data Source
AI summary
The invention is an electronic circuit for testing a receiver. In detail, the circuit includes a RF signal generator providing an RF signal to a first mixer. A first oscillator providing a first signal to the first mixer. The first mixer receives the RF signal and the first signal and provides a first output signal comprising the RF signal plus the first signal and the RF signal minus the first signal. A first filter is coupled to the first mixer for receiving the first output signal and providing a second output signal wherein the RF signal plus the first output signal is removed. A second mixer is coupled to the first filter and is adapted to receive the second output signal and a second input signal from a second oscillator; and provides a third output signal to a second filter. A fourth output signal from the second filter provides a fifth output signal for testing the receiver that is amplitude and temperature insensitive.