Abstract:
Systems, methods, and devices are disclosed for implementing frequency calibration circuits. The devices may include a data source configured to generate a first data signal based on a first data value and a second data signal based on a second data value. The devices may include a gain control circuit configured to receive the first and second data signals from the data source, and generate a first modified data signal and a second modified data signal. The devices may include an oscillator circuit configured to generate a first output signal and a second output signal based, at least in part, on the first and second modified data signals. The devices may include a calibration circuit configured to determine an adjustment value based on the first and second output signals, and further configured to change a gain of the gain control circuit based on the determined adjustment value.
Abstract:
A digital phase-locked loop (DPLL) supporting two-point modulation is described. In one design, the DPLL includes a phase-to-digital converter and a loop filter operating in a loop, a first processing unit for a lowpass modulation path, and a second processing unit for a highpass modulation path. The first processing unit receives an input modulating signal and provides a first modulating signal to a first point inside the loop after the phase-to-digital converter and prior to the loop filter. The second processing unit receives the input modulating signal and provides a second modulating signal to a second point inside the loop after the loop filter. The first processing unit may include an accumulator that accumulates the input modulating signal to convert frequency to phase. The second processing unit may include a scaling unit that scales the input modulating signal with a variable gain.
Abstract:
A self-calibrating modulator apparatus (300) includes a modulator having a controlled oscillator (326) and an oscillator gain calibration circuit (304). The oscillator gain calibration circuit includes an oscillator gain coefficient calculator (332) configured to calculate a plurality of frequency dependent oscillator gain coefficients from results of measurements taken at the output of the controlled oscillator in response to a test pattern signal representing a plurality of different reference frequencies. The plurality of frequency dependent gain coefficients determined from the calibration process are stored in a look up table (LUT) (334), where they are made available after the calibration process ends to scale a modulation signal applied to the modulator. By scaling the modulation signal prior to it being applied to the control input of the controlled oscillator, the nonlinear response of the controlled oscillator is countered and the modulation accuracy of the modulator is thereby improved.
Abstract:
The present invention relates to a polar modulation apparatus and method, in which an in-phase and a quadrature-phase signal are processed in the analog domain to generate an analog signal corresponding to a derivative of a phase component of said polar- modulated signal. The analog signal is then input to a control input of a controlled oscillator (40). As an example, the processing may be based on a differentiate - and - multiply algorithm in the analog domain. Thereby, phase and envelope signals are generated in the analog domain and bandwidth enlargement due to the processing of the polar signals and corresponding aliasing can be prevented to obtain a highly accurate polar-modulated output signal.
Abstract:
The invention relates to a circuit arrangement provided with a phase locked loop (1), which can be used particularly as a mobile-radio transmitter. The reference frequency of the PLL (1) provided with the source (3) is multiplied by a multiplier (10) and is down-mixed on an intermediate frequency plane in a step-down-controller (9) with the output signal of the PLL, and evaluated in such a way that a modulator (13), which is connected to the input of oscillator (6), can be adjusted. Preferably, the inventive principle can be used advantageously with two-point modulators to provide economical, integratable mobile radio transmitters exhibiting good noise characteristics.
Abstract:
The invention relates to a two-point modulator (1) comprising a PLL circuit (2). Said two-point modulator (1) comprises a first circuit branch for injecting an analog modulation signal (17) into a first point of the PLL circuit (2), and a second circuit branch for injecting a digital modulation signal (16) into a second point of the PLL circuit (2). The second circuit branch controls a frequency distributor (9) in the feedback branch of the PLL circuit (2) and contains a digital filter (10) having a rectangular impulse response.
Abstract:
A narrow band radio receiver (1) comprises a signal mixer (5) which mixes the received signal with a variable frequency output signal received from a variable frequency signal generating circuit (6). A signal, the frequency of which is the difference between the frequencies of the received signal and the variable frequency output signal is relayed to an intermediate filter (10) which filters out signals of frequencies other than an intermediate frequency, which is similar to the difference frequency. The filtered signal is amplified and demodulated through an amplifier (12), demodulator (14) and is passed through an output circuit (15) where it is read by a microprocessor (16). On the microprocessor (16) determining that the signal is in valid format the signal is outputted through a gate (18). The circuit (6) is in the form of a phase locked loop circuit and a voltage controlled oscillator (23) generates the variable frequency output signal. A phase comparator (25) compares the signal frequency outputted by the voltage controlled oscillator (23) with a constant frequency signal from a signal generator (20) and applies a signal proportional to the phase difference to a control input port (28) of the voltage controlled oscillator (23) through an adder (30). A first switch (SW1) breaks the feedback loop (27) when the circuit has locked-up and a capacitive circuit (36) retains the DC voltage on pin (1) of the adder (30) at the locked-up voltage. The microprocessor (16) through a digital to analogue converter (32) applies a stepped staircase voltage to a pin (2) of the adder (30) which is added to the locked-up voltage which in turn causes the voltage controlled oscillator (23) to sweep the frequency of the variable frequency output signal through incremental frequency steps in a staircase fashion.