Novatek Microelectronics Corp.

David Shiung

Yung-Lung Chen

A frequency synthesizing and back-end processing circuit and method thereof are provided. This circuit includes a fully digital frequency synthesizer by using interpolation and a linear feedback shift register to synthesize a frequency. After digital-to-analog conversion, it provides two options of the digital and analog signals. Then the selected signal will be mixed by the corresponding mixer. Finally, the filer removes the undesired noise to obtain the desired synthesized frequency signal. This frequency synthesizer does not require complex digital or analog circuits and can achieve a high frequency resolution with a lower circuit complexity, which is superior to the conventional art. The present invention also includes mixers for different frequencies and filters for back-end processing.

Frequency synthesizing and back-end processing circuit and method thereof

An algorithm for bit synchronization in a frequency shift keying (FSK) receiver. In the algorithm, a training sequence is received from a transmitter. The training sequence has a plurality of bits. A starting point of a next bit received by the FSK receiver after the training sequence is determined according to peak values of the bits of the training sequence.

Algorithm of bit synchronization for a digital FSK correlation receiver

A non-coherent frequency shift keying transmitter for up-converting a baseband signal to a radio frequency signal is provided. The non-coherent frequency shift keying transmitter applies the interpolation method in a digital frequency synthesizer to replace the conventional Phase Locked Loop (PLL) circuit. The micro processing unit receives a baseband signal firstly, then the baseband signal is converted to a RF signal via a digital synthesizer, a numerical controlled oscillator, a cascaded integrator-comb filter, and a digital-analog converter. The RF signal is then transmitted via a local oscillator, a band-pass filter, a power amplifier, and a transmitting end. This circuit eliminates unnecessary analog devices so that fabrication migration issue is avoided. Further, the modulated RF signal is more stable than that of the conventional modulator, and has a more efficient spectrum control and a better performance on the receiver end. A non-coherent FSK transmitting system is also provided in the present invention.

Non-coherent frequency shift keying transmitter using a digital interpolation synthesizer

A non-coherent frequency shift key demodulator comprising an oversampling device, a chain of registers, and a threshold device is disclosed. The oversampling device receives an input digital non-coherent frequency shift signal, and examines for transitions therein, and thereby generating data bit signals in the form of logic high level '1' or logic low level '0' accordingly. The chain of registers receives, counts and stores the number of 1's data bit signals. Following, the threshold device compares the stored number of 1's in the chain of registers with a predetermined threshold value to extract the digital signal of the input digital non-coherent frequency shift signal. The non-coherent frequency shift key demodulator, by the use of a simple circuit and implementation, combats miscellaneous system impairments, such as frequency offset, and further support multi-rate transmission.

Non-coherent FSK demodulator

The present invention provides an all-digital frequency synthesizer circuit using interpolation technique and Linear Feedback Shift Register (LFSR). This synthesizer adaptively outputs two sequences stored in a bank of memory, or shift register. Using the idea of interpolation, all synthesizable frequencies located between two predetermined threshold frequencies can be obtained, and resolution is determined by the order of LFSR thereby. A frequency synthesizing system is also included in the present invention.

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Tainan, Taiwan

David Shiung