US 5,353,311 A · Radio transmitter

Abstract

A radio transmitter suitable for a frequency hopping communication system which transmits a phase modulated signal with a minimum of spurious signals and phase noise. A direct digital frequency synthesizer (DDS) generates a frequency hopping signal lying in the VHF band. A first phase locked oscillator reduces the spurious components of the frequency hopping signal to produce a corresponding signal lying in the UHF band. This UHF band signal is used as a reference signal for a second phase locked oscillator which sends the phase modulated signal via a voltage controlled oscillator (VCO) built therein. The second phase locked oscillator includes a modulator for further modulating the phase of the phase modulated signal or a frequency divided version thereof by a modulating signal. The output of the modulator is used as a signal to be compared by a phase comparator or a source of signal to be compared. Since the second phase locked oscillator has a phase locked loop band sufficiently broader than the signal band of the modulating signal, it not only generates the phase modulated signal capable of sufficiently following the modulating signal, but also suppresses phase noise of the phase modulated signal ascribable to the VCO.

Claims14

Dependent claims

A radio transmitter comprising:

reference signal inputting means for receiving a reference signal;
modulating signal inputting means for receiving a modulating signal;
transmit signal outputting means for outputting a transmit signal;
voltage controlled oscillating means responsive to a control signal for generating the transmit signal phase locked to the reference signal;
and
phase locking means responsive to the reference signal, the modulating signal and the transmit signal for generating the control signal;
said phase locking means comprising phase modulating means for generating a phase modulated signal by modulating a phase of a signal associated with the transmit signal by the modulating signal.

4 more elements

A radio transmitter comprising:

reference signal inputting means for receiving a reference signal;
modulating signal inputting means for receiving a modulating signal;
transmit signal outputting means for outputting a transmit signal;
first frequency dividing means for dividing the reference signal to produce a frequency divided reference signal;
multiplying means for multiplying the reference signal to produce a frequency multiplied reference signal;
voltage controlled oscillating means responsive to a control signal for generating the transmit signal phase locked to the frequency divided reference signal;
frequency combining means for combining a frequency of the transmit signal and a frequency of the frequency multiplied reference signal to produce a difference frequency signal;
phase modulating means for modulating a phase of the difference frequency signal by the modulating signal to produce a phase modulated signal;
second frequency dividing means for dividing the phase modulated signal to produce a frequency divided modulated signal;
phase comparing means for comparing a phase of the frequency divided reference signal and a phase of the frequency divided modulated signal;
and
loop filter means for producing the control signal by limiting an output of said phase comparing means to a predetermined signal band.

9 more elements

Dependencies are inferred from the claim text.

Radio transmitter

Life of this patent

Radio transmitter

Life of this patent

Abstract

Claims14