Programmable Notch Filter in RF Transmitter Front Ends
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Solution Overview
Problem
Conventional wireless communication systems face challenges in effectively filtering out-of-band noise while maintaining in-band signal integrity, particularly in multi-standard and multi-frequency environments, which can degrade receiver performance and increase power consumption.
Innovation Solution
A radio transmitter front end is designed with a notch filter and feedback mechanism that generates filter control signals to selectively filter out-of-band noise, using a cascode amplifier and active Q boost circuit to enhance noise rejection while preserving in-band frequencies, and includes a switch matrix for flexible configuration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional filtering methods are used to remove out-of-band noise, then noise reduction is achieved, but in-band signal integrity deteriorates
Solution Approach 1:
The patent implements a notch filter that provides selective frequency-dependent filtering, creating a localized deep attenuation notch at specific out-of-band frequencies while maintaining passband flatness. This allows aggressive noise rejection at targeted frequencies without degrading the overall in-band signal integrity, as the filter's quality factor (Q) is programmably adjusted to optimize the balance between notch depth and bandwidth.
Solution Approach 2:
The patent employs programmable filter parameters including quality factor (Q), center frequency, and bandwidth that can be dynamically adjusted based on communication standards and operating conditions. This enables the filter to adapt its characteristics to achieve optimal noise rejection while preserving signal integrity for different modulation schemes and frequency allocations, resolving the contradiction between aggressive filtering and signal preservation.
2Reliability
If fixed filtering is applied to meet specific communication standards, then compliance is achieved, but adaptability to multi-standard environments deteriorates
Solution Approach 1:
The patent implements a dynamically reconfigurable notch filter where the quality factor (Q), center frequency, and bandwidth parameters can be programmably adjusted in real-time. This allows the same hardware filter to adapt its characteristics to meet the specific spectral requirements of different communication standards (e.g., Wi-Fi, Bluetooth, cellular) and operating conditions, achieving both standard compliance and multi-standard versatility without requiring multiple fixed filters.
Solution Approach 2:
The patent creates a universal filter platform that can serve multiple communication standards and applications through programmable control. A single notch filter implementation can be configured to support various Wi-Fi standards (802.11a/b/g/n/ac), Bluetooth frequencies, and other wireless protocols by adjusting its parameters, eliminating the need for separate fixed filters for each standard and enabling seamless multi-standard operation.
3Object-affected harmful factors
If aggressive noise filtering is implemented, then out-of-band rejection is improved, but power consumption increases
Solution Approach 1:
The patent applies filtering action selectively and proportionally rather than uniformly across all frequencies. The programmable notch filter concentrates its aggressive filtering action only at specific out-of-band frequencies where interference is present, while maintaining minimal impact on in-band signals. This partial action approach achieves effective noise rejection at problem frequencies without the excessive power consumption that would result from broad-spectrum aggressive filtering.
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
This solution effectively reduces out-of-band noise interference, improves signal-to-noise ratio, and minimizes power consumption by dynamically adjusting the notch filter's frequency response to match specific communication standards like 802.11ac, enhancing overall wireless communication system performance.
Implementation Method 1
a notch filter, coupled to the control signal generator and the at least one amplifier stage, operable to filter out of band noise while passing in-band frequencies
Implementation Method 2
a feedback generator, coupled to the at least one amplifier stage, operable to generate a transmit feedback signal in response to the transmit signal
Data Source
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AI summary
A radio transmitter front end for use in a radio frequency (RF) transceiver includes at least one amplifier stage operable to generate a transmit signal in response to an upconverted signal. A feedback generator is operable to generate a transmit feedback signal in response to the transmit signal. A control signal generator is operable to generate at least one filter control signal in response to the transmit feedback signal. A notch filter is operable to filter out of band noise while passing in-band frequencies to the at least one amplifier stage, under control of the at least one filter control signal.