Direct-Conversion FSK Receiver With Low-Rate Phase Switching
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Solution Overview
Problem
Conventional FSK radio frequency signal receivers face high power consumption and low sensitivity due to rapid phase switching and the need for broad bandwidth filters, making them unsuitable for communication systems with multiple channels.
Innovation Solution
A low rate direct conversion radio frequency signal receiver with a phase shift circuit that performs a 0° to 90° phase shift in each semi-period of a phase switching cycle, using a single mixer and a low-pass filter with a narrow bandwidth, and employing magic circuits to reconstruct signals during pause times for continuous demodulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If rapid phase switching is used in conventional FSK receivers, then data demodulation can be performed, but power consumption increases and sensitivity decreases
Solution Approach 1:
The patent applies periodic action by using a phase switching circuit that alternates between 0° and 90° phase shifts at a controlled frequency. This periodic phase switching enables the single mixer to generate both in-phase and quadrature components sequentially, allowing data demodulation while operating at lower power consumption compared to conventional rapid switching approaches.
Solution Approach 2:
The patent implements preliminary action through magic circuits that reconstruct signal components during pause times. These circuits prepare and maintain signal integrity before the next phase switching cycle begins, ensuring continuous demodulation capability without requiring rapid switching, thus reducing power consumption while maintaining sensitivity.
2Adaptability or versatility
If broad bandwidth filters are used to handle rapid phase switching, then phase switching can be performed, but device complexity and power consumption increase
Solution Approach 1:
By using periodic phase switching at a controlled frequency rather than rapid continuous switching, the patent enables the use of narrow band filters. The periodic nature of the switching allows filter design that targets specific frequency components, reducing the need for broad bandwidth filters and simplifying the overall device complexity.
3Device complexity
If a single mixer is used instead of two mixers, then device complexity is reduced, but phase switching requirements become more stringent
Solution Approach 1:
The magic circuits perform preliminary action by reconstructuring signal components during pause times in the phase switching cycle. This pre-preparation of signal components compensates for the stricter phase switching requirements imposed by using a single mixer, maintaining demodulation accuracy without requiring overly complex phase switching mechanisms.
Solution Approach 2:
The magic circuits act as intermediary elements between the single mixer output and the demodulation stage. These circuits bridge the gap created by the single mixer's limited output, reconstructing missing signal components and enabling accurate demodulation despite the simplified mixer configuration.
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 design reduces power consumption while maintaining high sensitivity and enabling efficient demodulation, even at low data rates, by slowing down phase switching and using magic circuits to ensure continuous signal reconstruction.
Implementation Method 1
a phase shift circuit for performing a 0° to 90° phase shift and vice versa in the oscillating signals or the incoming FSK radio frequency signals, in each semi-period of a phase switching cycle
Implementation Method 2
a mixer for successively mixing the in-phase and quadrature signals with the filtered and amplified incoming FSK radio frequency signals
Implementation Method 3
at least one low-pass filter for filtering the intermediate in-phase and quadrature signals
Implementation Method 4
a low noise amplifier for amplifying and filtering the signals picked up by the antenna
Data Source
AI summary
The receiver (1) picks up low rate FSK radio frequency signals. This receiver includes an antenna (2) for receiving FSK radio frequency signals, a low noise amplifier (3) connected to the antenna, a local oscillator (7) for supplying oscillating signals (LO), a phase shift circuit (16) for performing a 0° to 90° phase shift, and vice versa, in the oscillating signals (LO) or the incoming FSK radio frequency signals in each semi-period of a phase switching cycle (1/fs). The phase shift circuit alternately and successively generates in-phase and quadrature oscillating signals, or in-phase and quadrature incoming FSK radio frequency signals. The receiver includes a single mixer (4) for mixing the oscillating signals successively with the incoming FSK radio frequency signals, so as to generate alternately intermediate in-phase and quadrature baseband signals (INT) as a function of the phase shift circuit. The receiver further includes a low-pass filter (8) for filtering the intermediate in-phase and quadrature signals, and a demodulation stage (20) for demodulating the data (DOUT) from the filtered intermediate signals. The receiver is arranged such that the phase shift circuit (16) is switched by a phase selection signal (SEL) to a phase switching cycle frequency (fs) which is lower than the frequency deviation (Δf) of the modulated data in the FSK radio frequency signals and higher than the data rate frequency. Magic circuits (14, 15) in the demodulation stage reconstruct the intermediate signals during each switch operation for continuous demodulation in the demodulator (12).