US 5,263,197 A · Dual port oscillator for two-stage direct conversion receiver

Abstract

A two-stage direct conversion receiver. A first mixer (13) converts the incoming signal to an intermediate frequency (IF) signal. A second mixer (16) converts the IF signal to a baseband signal. A detector (17), receiver logic circuit (18), and alerting device circuit (19) act upon the baseband output signal. A two port oscillator (14) provides a fundamental frequency output (FO) and a tripled output frequency (3 FO). The tripled output frequency is again tripled (9 FO) by a frequency multiplier (15) and is provided as a mixing signal to the first mixer (13). The fundamental frequency output is provided to a phase locked loop (20, 21, 22). The output frequency (FV) of the phase locked loop is doubled (2 FV) by a frequency multiplier (23) and provided to a phase shift circuit (24). The output of the phase shift circuit (24) is provided as the second mixing signal to the second mixer (16). The phase locked loop comprises a phase locked loop controller (20), a phase locked loop filter (21), and a voltage controlled oscillator (22). The main oscillator (14) is configured as a crystal controlled Colpitts oscillator, which has an emitter resonant circuit selected to produce oscillation at the fundamental frequency, and a collector resonant circuit selected to extract the third harmonic of the fundamental oscillation frequency. A single active device can therefore provide both the fundamental frequency and the third harmonic frequency. Calibration of the receiver is effected by simply tuning the oscillator (14) to produce a baseband output signal at the output of the second mixer (16). Single step calibration is therefore effected because the voltage controlled oscillator (22) is locked to the main oscillator (14).

Claims20

Dependent claims

An oscillator, comprising:

an amplifying device having an input terminal, a first output terminal, and a second output terminal;
a crystal, having a predetermined characteristic frequency, functionally connected to said input terminal;
a first resonant circuit, having a resonant frequency selected to cause said amplifying device to oscillate only at approximately said predetermined characteristic frequency, and functionally connected to said first output terminal;
and
a second resonant circuit, having a resonant frequency being approximately N times said predetermined characteristic frequency, and being functionally connected to said second output terminal, N being an integer greater than one;
wherein said first output terminal primarily provides a first output signal having a frequency approximately the same as said predetermined characteristic frequency, and said second output terminal primarily provides a second output signal having a frequency approximately N times said predetermined characteristic frequency.

3 more elements

A direct conversion receiver, comprising:

a first mixer responsive to an input signal and a first mixing signal for providing an intermediate frequency (IF) output signal;
a first oscillator for providing a first oscillator signal to said first mixer as said first mixing signal;
a second mixer responsive to said IF output signal and a second mixing signal for providing a baseband output signal;
a second oscillator for providing a second oscillator signal to said second mixer as said second mixing signal;
and
locking means for locking said second oscillator signal in a predetermined relationship to said first oscillator signal;
wherein said first oscillator has a first port for providing a reference signal having a first frequency to said locking means, and a second port for providing said first oscillator signal having a frequency of N times said first frequency, where N is an integer greater than 1.

4 more elements

Dependencies are inferred from the claim text.

Dual port oscillator for two-stage direct conversion receiver

Life of this patent

Dual port oscillator for two-stage direct conversion receiver

Life of this patent

Abstract

Claims20