Tuner with quadrature downconverter for pulse amplitude modulated data applications

An apparatus for converting pulse amplitude modulated radio frequency (RF PAM) signals to baseband signals, said apparatus comprising:

• means for receiving an RF input signal;
• local oscillator means for producing a low phase noise local oscillator signal with good microphonic performance, said local oscillator means including a microstrip resonator substantially immune to mechanical vibration and having as a current delay element a microstrip transmission line forming a delay line and operative to apply a tuning voltage across a varactor diode through said microstrip transmission line, said local oscillator means comprising a low loop bandwidth phase locked loop synthesizer having a voltage controlled oscillator with fine frequency resolution, the loop bandwidth being sufficiently small such that noise effects of said local oscillator means are dominated by the voltage controlled oscillator;
• means coupled to said receiving means and to said first local oscillator means for mixing the RF input signal over a range of frequencies with the low noise local oscillator signal to obtain an IF signal at an IF frequency of sufficient bandwidth and of sufficient quality to allow extraction of digital data;
• and
• means coupled to receive said IF signal for extracting an in-phase (I) signal and a quadrature-phase (Q) signal at a baseband for use in digitally demodulating the I signal and the Q signal.

An apparatus for converting pulse amplitude modulated radio frequency (RF PAM) signals to baseband signals, said apparatus comprising:

• means for receiving an RF input signal;
• local oscillator means for producing a low phase noise local oscillator signal with good microphonic performance, said local oscillator means comprising a low loop bandwidth phase locked loop synthesizer having a voltage controlled oscillator with fine frequency resolution, the loop bandwidth being sufficiently small such that noise effects of said local oscillator means are dominated by the voltage controlled oscillator, wherein said low loop bandwidth phase locked loop synthesizer of said local oscillator means has a phase locked loop realized with a high loop divide ratio and a low loop bandwidth such that the loop divide ratio of said phase locked loop is less than is suited for its intended tuning range so that phase noise is determined primarily by noise of the low noise voltage controlled oscillator, and further including a microstrip resonator substantially immune to mechanical vibration to attain the good microphonic performance;
• means coupled to said receiving means and to said first local oscillator means for mixing the RF input signal over a range of frequencies with the low noise local oscillator signal to obtain an IF signal at an IF frequency of sufficient bandwidth and of sufficient quality to allow extraction of digital data;
• and
• means coupled to receive said IF signal for extracting an in-phase (I) signal and a quadrature-phase (Q) signal at a baseband for use in digitally demodulating the I signal and the Q signal.

An apparatus for converting pulse amplitude modulated radio frequency (RF PAM) signals to baseband signals, said apparatus comprising:

• means for receiving an RF input signal;
• local oscillator means for producing a low phase noise local oscillator signal with good microphonic performance, wherein local oscillator means comprises a low loop bandwidth phase locked loop synthesizer having a voltage controlled oscillator, said phase locked loop synthesizer having a phase locked loop realized with a high loop divide ratio and a low loop bandwidth such that the loop divide ratio of said phase locked loop is less than is suited for its intended tuning range so that phase noise is determined primarily by noise of the low noise voltage controlled oscillator;
• said local oscillator means comprising a low loop bandwidth phase locked loop synthesizer having a voltage controlled oscillator with fine frequency resolution, the loop bandwidth being sufficiently small such that noise effects of said local oscillator means are dominated by the voltage controlled oscillator;
• means coupled to said receiving means and to said first local oscillator means for mixing the RF input signal over a range of frequencies with the low noise local oscillator signal to obtain an IF signal at an IF frequency of sufficient bandwidth and of sufficient quality to allow extraction of digital data;
• and
• means coupled to receive said IF signal for extracting an in-phase (I) signal and a quadrature-phase (Q) signal at a baseband for use in digitally demodulating the I signal and the Q signal.