Wireless Transmitter Harmonic Rejection via Segmented Sub-Band Mixers
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Solution Overview
Problem
Conventional TV-band transmitters face challenges in managing unwanted harmonic emission without complex or power-intensive filtering, particularly due to the constraint of high-frequency reference local oscillators (LOref) in existing harmonic rejection mixer (HRM)-based architectures, which limits their operating bandwidth and efficiency.
Innovation Solution
A wireless transmitter design utilizing a two-stage 14-path harmonic-rejection mixer for lower sub-bands and a two-stage 6-path harmonic-rejection mixer for upper sub-bands, combined with passive filtering and driver amplifiers, along with an 8- and 16-phase LO generator to manage harmonic rejection ratio (HRR) and reduce gain mismatch, achieving a wideband operation with favorable power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional HRM-based architectures use high-frequency reference LO (LOref=9×RF or higher) to achieve harmonic rejection, then harmonic rejection ratio is improved, but operating bandwidth is limited and power consumption increases
Solution Approach 1:
The transmitter is divided into two independent sub-band transmitters: a first sub-band transmitter covering 54-432 MHz and a second sub-band transmitter covering 432-864 MHz. Each transmitter uses its own low-frequency reference LO (432-864 MHz for first sub-band, 864-1728 MHz for second sub-band), eliminating the need for a single high-frequency reference LO and enabling wideband operation across the entire TV band.
Solution Approach 2:
The system dynamically selects which sub-band transmitter to use based on the desired operating frequency. A frequency determination unit identifies whether the target frequency falls in the lower or upper sub-band, and the corresponding transmitter is activated. This dynamic selection allows the system to maintain optimal performance across the entire 54-1728 MHz range.
2Manufacturing precision
If conventional HRM-based architectures use high-frequency reference LO to achieve harmonic rejection, then harmonic rejection ratio is improved, but power consumption increases
Solution Approach 1:
By segmenting the frequency range into two sub-bands and using separate low-frequency reference LOs for each, the system avoids the need for a single high-frequency reference LO that would consume excessive power. Each reference LO operates at manageable frequencies (432-864 MHz and 864-1728 MHz), significantly reducing power consumption compared to conventional high-frequency reference LO approaches.
3Adaptability or versatility
If a single wideband transmitter is used to cover the entire TV band, then adaptability is improved, but gain mismatch and harmonic rejection performance deteriorate
Solution Approach 1:
The frequency coverage is segmented into two distinct sub-bands (54-432 MHz and 432-864 MHz), each handled by a dedicated transmitter optimized for its specific range. This segmentation allows each transmitter to be precisely tuned and calibrated for its sub-band, eliminating the gain mismatch problems that would arise in a single wideband transmitter attempting to cover the entire range.
Solution Approach 2:
Each sub-band transmitter is optimized with local quality characteristics specific to its frequency range. The first sub-band transmitter uses a reference LO of 432-864 MHz optimized for lower frequencies, while the second uses 864-1728 MHz optimized for upper frequencies. This localized optimization ensures optimal gain matching and harmonic rejection performance in each sub-band without compromise.
Data Source
AI summary
A wireless transmitter for resolving gain mismatch of TV band is disclosed. In one embodiment, a wireless transmitter comprises a two-stage 14-path harmonic-rejection mixer to manage harmonic rejection ratio in lower sub-bands, and a two-stage 6-path harmonic-rejection mixer to manage harmonic rejection ratio in upper sub-bands. The gain mismatch is resolved by selecting gain ratios of the first and the second stage of the two-stage 14-path harmonic-rejection mixer and the two-stage 6-path harmonic-rejection mixer.