US 6,668,025 B1 · Tuning demodulator for digitally modulated RF signals

Abstract

A tuning demodulator for digitally modulated signals tunes and detects a desired RF signal by an I/Q detection circuit and a tuning oscillation circuit composed of a PLL synthesizer having an output frequency close to the desired RF signal, and being provided with electrical or mechanical signal separating components to suppress the leaked output power from the tuning oscillation circuit. The signal separation components include an arrangement of circuits inside a metallic case, a metallic partition board, and an arrangement of power supply terminals. When the tuning demodulator detects a frequency error by a frequency error detection circuit, it adjusts a voltage-controlled reference oscillator that gives the PLL synthesizer an exact frequency reference, and hence it prevents deterioration of the bit error rate of the detected signals. Further, an error correction circuit can be added to compensate the fluctuations in characteristics of constituent parts.

Claims18

Dependent claims

A tuning demodulator for digitally modulated RF signals, comprising;

(a) an RF input terminal for receiving a digitally modulated RF signal,
(b) an RF circuit for receiving said RF signal through said RF input terminal,
(c) an I/Q detection circuit for receiving the output signal of said RF circuit,
(d) an oscillation circuit for detection for generating an unmodulated RF wave an putting into said I/Q detection circuit,
(e) a plurality of I/Q output terminals for issuing a detection output signal of said I/Q detection circuit,
(f) at least one of electrical and mechanical signal separating means for suppressing leakage of the unmodulated RF wave from said RF input terminal, and
(g) a metallic casing for accommodating (a) to (f),
wherein as said signal separating means being an arrangement of the circuits (b) to (d), said RF circuit is arranged so that said oscillation circuit is not adjacent thereto, and hence said RF circuit being physically separated from said oscillation circuit, and invasion of radiated signal from said oscillation circuit into said RF circuit is reduced, and
wherein, as said signal separating means, a plane region of a single-layer printed circuit board is divided into two sections, a print pattern of said RF circuit is formed in the surface of one region, a print pattern of said oscillation circuit for detection is formed on a back side of another region, and a plurality of through-holes are provided for electrically shorting between grounding surface of print pattern of said RF circuit and said oscillation circuit for detection.

6 more elements

A tuning demodulator for digitally modulated RF signals, comprising:

(a) an RF input terminal for receiving a digitally modulated RF signal,
(b) an RF circuit for receiving said RF signal through said RF input terminal,
(c) an I/Q detection circuit for receiving the output signal of said RF circuit,
(d) an oscillation circuit for detection for generating an unmodulated RF wave and putting into said I/Q detection circuit,
(e) a plurality of I/Q output terminals for issuing a detection output signal of said I/Q detection circuit,
(f) at least one of electrical and mechanical signal separating means for suppressing leakage of the unmodulated RF wave from said RF input terminal, and
(h) a metallic casing for accommodating (a) to (f),
wherein said signal separating means being an arrangement of the circuits (b) to (d), said RF circuit is arranged so that said oscillation circuit is not adjacent thereto and hence said RF circuit being physically separated from said oscillation circuit, and invasion of a radiated signal from said oscillation circuit into said RF circuit is reduced, and
wherein, as said signal separating means, a low pass filter is connected to a power supply terminal for said oscillation circuit to prevent the oscillation signal from leaking to said power supply terminal and radiating from said power supply terminal.

6 more elements

A tuning demodulator for digitally modulated RF signals, comprising:

(a) an RF input terminal for receiving a digitally modulated RF signal,
(b) an I/Q detection circuit for receiving said RF signal through said RF input terminal,
(c) an oscillation circuit for detection for generating an unmodulated RF wave and feeding into said I/Q detection circuit,
(d) a voltage-controlled reference oscillation signal source for generating a reference oscillation signal for determining the frequency of output signal of said oscillation circuit,
(e) at least one of electrical and mechanical signal separating means for suppressing leakage of the unmodulated RF wave from said RF input terminal,
(f) an A/D converter for receiving an output signal of said I/Q detection circuit,
(g) a complex multiplier for receiving an output signal of said A/D converter,
(h) a data detection circuit for receiving an output signal of said complex multiplier,
(i) a plurality of data output terminals for issuing an output signal of said data detection circuit,
(j) a frequency error detection circuit for detecting a frequency error between said RF signal and the output signal of said oscillation circuit, by using the output signal of said complex multiplier,
(k) a PLL frequency synthesizer containing a phase lock loop for comparing the phase of both output signals of said oscillation circuit and said voltage-controlled reference oscillation signal source, and controlling the frequency of the output signal of said oscillation circuit in a direction of compensating for said frequency error, and
(l) a metallic casing for accommodating (a) to (k),
wherein the frequency of said voltage-controlled reference oscillation signal source is controlled by the output signal value of said frequency error detection circuit.

10 more elements

A tuning demodulator for digitally modulated RF signals, comprising:

an RF input terminal for receiving a digitally modulated RF signal,
an J/Q detection circuit for receiving said RF signal through said input terminal,
an oscillation circuit for detection for generating an unmodulated RF wave and feeding into said I/Q detection circuit,
a reference oscillation signal source for generating a reference oscillation signal for determining the frequency of output signal of said oscillation circuit for detection,
signal separating means provided between said RF input terminal and said oscillation circuit for detection,
an A/D converter for receiving an output signal of said I/Q detection circuit,
a complex multiplier for receiving an output signal of said A/D converter,
a data detection circuit for receiving an output signal of said complex multiplier,
a plurality of data output terminals for issuing an output signal of said data detection, circuit,
a frequency error detection circuit for detecting a frequency error between said RF signal and the output signal of the oscillation circuit for detection, by using the output signal of said complex multiplier, and
a PLL frequency synthesizer containing a phase lack loop for comparing the phase of both output signals of said oscillation circuit for detection and reference oscillation signal source, and controlling the frequency of the output signal of the oscillation, circuit for detection in a direction of compensating for said frequency error,
wherein the frequency of sold reference oscillation signal is controlled by the output signal value of the frequency error detection circuit, and
wherein if said frequency error exceeds the detectable range of said frequency error detection circuit determined by the method of said digital modulation and the synchronism of sold phase lock loop is not established, the output signal value of said frequency error detection circuit is changed sequentially and issued, and the frequency of the output signal of said oscillation circuit for detection is changed and the synchronism of said phase lock loop is established.

10 more elements

Dependencies are inferred from the claim text.

Tuning demodulator for digitally modulated RF signals

Life of this patent

Tuning demodulator for digitally modulated RF signals

Life of this patent

Abstract

Claims18