摘要:
A radio receiver comprising: an antenna for receiving a radio frequency signal amplitude modulated with an audio frequency signal; a digitiser for periodically sampling the radio frequency signal and generating a digital reception signal representative of the amplitude of the radio frequency signal; and a demodulator for demodulating the digital reception signal to generate a representation of the audio frequency signal.
摘要:
A switch circuit comprising a mechanical switch having two contact elements, the switch being operable to bring the two contact elements into physical contact and thereby output an analogue switch signal representative of operation of the switch and a sigma-delta modulator arranged to receive the analogue switch signal and to output a digital switch signal in dependence thereon, the sigma-delta modulator having a frequency response such that it can suppress a relatively high frequency component of the analogue input signal and thereby effectively debounce the output of the switch.
摘要:
A radio receiver comprising: an antenna for receiving a radio frequency signal amplitude modulated with an audio frequency signal; a digitiser for periodically sampling the radio frequency signal and generating a digital reception signal representative of the amplitude of the radio frequency signal; and a demodulator for demodulating the digital reception signal to generate a representation of the audio frequency signal.
摘要:
A random number generator comprising a sigma-delta modulator, the sigma- delta modulator having a modulation unit comprising: a summation unit arranged to receive an analogue input signal that varies due to noise over a first voltage range, the summation unit being arranged to sum the analogue input signal with an adjustment signal to form a summation output signal; a loop filter arranged to receive the summation output signal and form a filtered output signal dependent thereon; and a quantiser arranged to receive the filtered output signal, compare the filtered output signal with a quantiser threshold and form a digital output signal by selecting between one of two predetermined voltage levels for the digital output signal in dependence on the comparison; and the sigma-delta modulator further comprising: a feedback loop arranged to receive the digital output signal and form the adjustment signal in dependence on the digital output signal such that at any given time instant the absolute difference between an amplitude of the summation output signal and the quantiser threshold is less than the first voltage range, the random number generator thereby being capable of forming a digital output signal derived from the analogue input signal and having a high degree of entropy.
摘要:
A method for cancelling a beat frequency in a radio receiver capable of receiving a radio signal, forming a first demodulated signal (8) by mixing a signal derived from the radio signal with a first local oscillator signal (6), and forming a second demodulated signal (9) by mixing a signal derived from the radio signal with a second local oscillator signal (7) having a quadrature relationship with the first local oscillator signal, the method comprising repeatedly performing the steps of: a. determining the modulus of the first demodulated signal; b. determining the modulus of the second demodulated signal; c. comparing the modulus of the first demodulated signal with the modulus of the second demodulated signal; d. determining a quotient by dividing the greater of the moduli of the first demodulated signal and the second demodulated signal by the lesser of the moduli of the first demodulated signal and the second demodulated signal; e. determining a cancellation factor having the value of the reciprocal of the cosine of the arctangent of the quotient; and f. forming a beat cancelled signal by multiplying one of the first and second demodulated signals by the cancellation factor.
摘要:
A method for cancelling a beat frequency in a radio receiver capable of receiving a radio signal, forming a first demodulated signal (8) by mixing a signal derived from the radio signal with a first local oscillator signal (6), and forming a second demodulated signal (9) by mixing a signal derived from the radio signal with a second local oscillator signal (7) having a quadrature relationship with the first local oscillator signal, the method comprising repeatedly performing the steps of: a. determining the modulus of the first demodulated signal; b. determining the modulus of the second demodulated signal; c. comparing the modulus of the first demodulated signal with the modulus of the second demodulated signal; d. determining a quotient by dividing the greater of the moduli of the first demodulated signal and the second demodulated signal by the lesser of the moduli of the first demodulated signal and the second demodulated signal; e. determining a cancellation factor having the value of the reciprocal of the cosine of the arctangent of the quotient; and f. forming a beat cancelled signal by multiplying one of the first and second demodulated signals by the cancellation factor.
摘要:
A random number generator comprising a sigma-delta modulator, the sigma- delta modulator having a modulation unit comprising: a summation unit arranged to receive an analogue input signal that varies due to noise over a first voltage range, the summation unit being arranged to sum the analogue input signal with an adjustment signal to form a summation output signal; a loop filter arranged to receive the summation output signal and form a filtered output signal dependent thereon; and a quantiser arranged to receive the filtered output signal, compare the filtered output signal with a quantiser threshold and form a digital output signal by selecting between one of two predetermined voltage levels for the digital output signal in dependence on the comparison; and the sigma-delta modulator further comprising: a feedback loop arranged to receive the digital output signal and form the adjustment signal in dependence on the digital output signal such that at any given time instant the absolute difference between an amplitude of the summation output signal and the quantiser threshold is less than the first voltage range, the random number generator thereby being capable of forming a digital output signal derived from the analogue input signal and having a high degree of entropy.
摘要:
A radio receiver comprising: an antenna for receiving a radio frequency signal amplitude modulated with an audio frequency signal; a digitiser for periodically sampling the radio frequency signal and generating a digital reception signal representative of the amplitude of the radio frequency signal; and a demodulator for demodulating the digital reception signal to generate a representation of the audio frequency signal.