Bipolar TDC Phase Ordering for Accurate Phase Error Capture
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Solution Overview
Problem
Conventional time-to-digital converters (TDCs) face challenges in accurately measuring phase differences between input signals due to unipolar detection limitations, leading to incorrect operations, long measurement times, and increased jitter and power consumption, especially in digital phase-locked loops (DPLLs) with uncontrolled phase relationships or phase modulation.
Innovation Solution
A bipolar TDC apparatus with phase detection and signal switching circuitry, utilizing a multiplexer and phase detector to handle signal phase orders, ensuring the earlier phase starts the measurement and the later phase triggers it, thereby enabling bipolarity detection and reducing phase error magnitude.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If unipolar detection is used in conventional TDC, then the TDC structure is simple, but the measurement range is limited and requires long average run time to guarantee correct phase order
Solution Approach 1:
The patent introduces a phase detector that detects the polarity of phase difference between input signals, enabling the TDC to handle both unipolar and bipolar phase orders. This inversion of the conventional unipolar-only approach allows the system to adapt to varying phase relationships without requiring long average run times or complex switching mechanisms.
Solution Approach 2:
The patent makes the TDC operation dynamic by using a phase detector to determine the polarity of phase difference and automatically adjusting the measurement mode accordingly. This dynamic adaptation allows the TDC to switch between handling unipolar and bipolar phase orders based on the actual input signal conditions, eliminating the need for fixed long average run times.
2Measurement precision
If long average run time is used to guarantee correct phase order, then measurement accuracy improves, but jitter and power consumption increase significantly
Solution Approach 1:
The patent performs preliminary phase polarity detection before the actual phase difference measurement. The phase detector determines the polarity of the phase difference in advance, allowing the TDC to configure its measurement elements appropriately beforehand. This preliminary action eliminates the need for long average run times to guarantee correct phase order, thereby reducing both measurement time and power consumption while maintaining accuracy.
3Ease of operation
If unipolar detection is used, then the TDC operation is straightforward, but reversed phase order causes invalid output or requires waiting for next proper order
Solution Approach 1:
The patent implements feedback through a phase detector that continuously monitors the polarity of the phase difference between input signals. This feedback mechanism provides real-time information about the phase order, allowing the TDC to adjust its operation accordingly. As a result, the system maintains high reliability by ensuring valid output regardless of phase order, while keeping the operation relatively simple through automated polarity-based control.
4Adaptability or versatility
If large offset is added to cover dynamic range of phase error, then correct phase order is guaranteed, but significant jitter is induced
Solution Approach 1:
The patent changes the operational parameters of the TDC based on the detected phase polarity. Instead of using a fixed large offset to cover all possible phase errors, the system dynamically adjusts its measurement parameters according to the actual phase relationship determined by the phase detector. This parameter adaptation allows the TDC to cover the required dynamic range of phase errors while minimizing jitter by avoiding unnecessary large offsets.
Data Source
AI summary
A bipolar TDC apparatus with a phase detection and signal switching circuitry and a phase error measurement circuitry. The phase detection and signal switching circuitry include a multiplexer and phase detector, together referred to as PD_MUX. The PD_MUX is used to handle the order of the two input signal phases of a TDC, or in other words, to enable TDC the bipolarity detection of the phase error. The apparatus detects first the polarity of the phase error and then prepares the right phase order when they arrive at the TDC measurement elements of the phase error measurement circuitry to ensure that always the earlier one starts the TDC and the later one triggers the measurement event. As such, the phase measurement circuitry (or measurement block) provides the phase error magnitude information, while the PD_MUX provides the sign—polarity information.