# US 5,352,885 A · Frequency converter for varying the frequency of a local signal over a wide band

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- Number: US 5,352,885 A
- Document ID: US5352885A
- Status: Granted
- Kind: A
- Application number: 08/021,985
- Filed: 1993-02-24
- Granted: 1994-10-04
- Earliest claimed: 1992-03-03
- Assignees: Advantest Corporation
- Inventors: Shoji Niki
- Web page: https://patentgrep.com/patent/US5352885A

## CPC

- H04B 10/60: Receivers
- H03D 9/0608: {by means of diodes}
- H04B: TRANSMISSION
- H03D: DEMODULATION OR TRANSFERENCE OF MODULATION FROM ONE CARRIER TO ANOTHER (masers, lasers H01S; circuits capable of acting both as modulator and demodulator H03C; details applicable to both modulators and frequency-changers H03C; demodulating pulses H03K9/00; transforming types of pulse modulation H03K11/00; coding, decoding or code conversion, in general H03M; repeater stations H04B7/14; demodulators adapted for AC systems of digital information transmission H04L27/00; synchronous demodulators adapted for colour television H04N9/66)

## Abstract

An input signal of a frequency f.sub.0 is supplied to one end of a photodiode. Optical signals of frequencies F.sub.0 and F.sub.0 +.DELTA.F from two light sources are combined by a semitransparent mirror and the resulting interference light is applied to the photodiode. The interference light is converted by the photodiode to an electrical local signal of a frequency .DELTA.F. The electrical local signal and the input signal are frequency mixed in accordance with the nonlinear characteristic of the photodiode and an intermediate-frequency signal of a frequency corresponding to the frequency difference between them is provided at an output terminal.

## Claims

### Claim 1

A frequency converter comprising:
an electrical input terminal for receiving an input electrical signal having a frequency f.sub.0 ;
photodetector means, connected to said electrical input terminal, for receiving said input electrical signal, said photodetector means having a nonlinear characteristic;
local light source means for simultaneously applying two optical signals having different frequencies F.sub.0 and F.sub.0 +.DELTA.F to said photodetector means; and
signal extracting means for electrically extracting an electrical intermediate frequency signal from said photodetector means, the electrical intermediate-frequency signal having a frequency which is the difference between the frequency f.sub.0 of said input electrical signal and a frequency difference .DELTA.F between said two optical signals.

### Claim 2 (depends on 1)

The frequency converter of claim 1, wherein said signal extracting means includes filter means connected to said photodetector means at a side opposite said input terminal, for grounding a high-frequency component.

### Claim 3 (depends on 1)

The frequency converter of claim 1, wherein said signal extracting means includes filter means connected to said photodetector means on the same side as said input terminal, for grounding a high-frequency component.

### Claim 4 (depends on 1)

The frequency converter of claim 1, wherein said photodetector means includes two photodetectors connected in series in the forward direction;
wherein said signal extracting means includes:
filter means connected between both ends of the series connection of said two photodetectors and ground, for grounding a high-frequency component; and
an output transformer having a primary coil connected between both ends of the series connection of said two photodetectors, for outputting a frequency-converted signal to a secondary coil; and
wherein said input terminal is connected to the connection point of said two photodetectors.

### Claim 5 (depends on 4)

The frequency converter of claim 4, wherein said local light source means includes:
Peltier element means having a heat absorbing face and a heat radiating face;
two laser diodes mounted on the heat-absorbing face and the heat-radiating face of said Peltier element means, respectively, for outputting said optical signals; and
optical coupler means for combining said two optical signals into interference light and for applying said interference light to each of said two photodetectors.