초록 ▼

A local oscillator for a radio receiver includes a voltage controlled oscillator (VCO), a decoder and controller for providing a control voltage to the VCO, an error detector circuit for detecting an error in the frequency of the VCO on the basis of a received signal processed with the oscillating s

A local oscillator for a radio receiver includes a voltage controlled oscillator (VCO), a decoder and controller for providing a control voltage to the VCO, an error detector circuit for detecting an error in the frequency of the VCO on the basis of a received signal processed with the oscillating signal from the VCO, a temperature probe and a memory. The local oscillator is initially set up during manufacture by detecting any errors in the frequency at selected temperatures, and storing data in the memory indicative of the control voltage required to compensate for the frequency error for each temperature. In operation the decoder and controller applies the appropriate control voltage to the VCO on the basis of the data stored in the memory relative to the temperature detected by the temperature probe. If, for example as a result of ageing of the oscillator, the error detector detects an error in the frequency, the decoder and controller adjusts the control voltage to the VCO so as to compensate for the error, and the updated value is stored in the memory for subsequent use. If the received signal is mixed with the oscillating signal in a mixer, the output of intermediate frequency stages can be used for error detection. Alternatively, demodulated data can be used for this purpose, for example in a direct conversion receiver.

대표청구항 ▼

A local oscillator for a radio receiver, said local oscillator comprising: a voltage controlled oscillator for generating an oscillating signal at a nominal required frequency; a memory for storing data; temperature sensing means for providing a temperature-dependent signal; control means responsive

A local oscillator for a radio receiver, said local oscillator comprising: a voltage controlled oscillator for generating an oscillating signal at a nominal required frequency; a memory for storing data; temperature sensing means for providing a temperature-dependent signal; control means responsive to the temperature-dependent signal to select data from said memory in accordance with the temperature-dependent signal and to generate a control voltage for said voltage controlled oscillator according to the selected data; and error detecting means for detecting an error in the frequency of the oscillating signal from said voltage controlled oscillator on the basis of a received signal which has been mixed with the oscillating signal in the radio receiver; and wherein said control means is connected to said error detecting means and is operable when said error detecting means detects a frequency error (a) to adjust the control voltage to said voltage controlled oscillator so as to compensate for the frequency error and (b) to store data relating to the adjusted control voltage and to the respective temperature-dependent signal in said memory for subsequent use in temperature compensation, thereby to compensate for ageing effects in said voltage controlled oscillator.