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Transmit-receive fm-cw radar apparatus

Transmit-receive fm-cw radar apparatus description/claims

This application is a divisional of U.S. patent application Ser. No. 11/503,342, filed Aug. 10, 2006 which is a divisional application of U.S. patent application Ser. No. 10/802,642, filed Mar. 17, 2004, which claims priority of Japanese Patent Application No. 2003-78246, filed Mar. 20, 2003, the disclosure of each of which is incorporated by reference herein.

1. Field of the Invention

The present invention relates to an FM-CW radar apparatus that uses a frequency-modulated (FM) continuous wave (CW) transmit signal and, more particularly, to a transmit-receive FM-CW radar apparatus that switches between transmission and reception by time division.

2. Description of the Related Art

FM-CW radar is used as a radar system for measuring the distance, the relative velocity, etc. of a target object. As FM-CW radar can measure the distance and the relative velocity of a vehicle traveling ahead by using a simple signal processing circuit, and as its transmitter and receiver can be constructed with simple circuitry, this type of radar is used as an automotive collision avoidance radar.

There is disclosed as a transmit-receive FM radar a time-division multiplexing FM radar system that does not require the provision of a high-frequency, high-gain receiving amplifier circuit which supplies reflected FM frequencies, received via a transmit-receive common antenna, to a common mixer while amplifying the received frequencies intermittently in time division fashion (refer to Japanese Unexamined Patent Publication No. H10-90397).

There is also disclosed an FM-CW radar apparatus that subtracts FM-AM conversion noise from a beat signal thereby removing the FM-AM conversion noise before the beat signal is input to an A/D converter (refer to Japanese Unexamined Patent Publication No. 2002-189074).

There is further disclosed a transmit-receive FM-CW radar apparatus that can reduce the leakage of noise components between transmitter and receiver (refer to Japanese Unexamined Patent Publication No. 11-148972).

An object of the present invention is to reduce FM-AM conversion noise in a transmit-receive FM-CW radar apparatus.

A transmit-receive FM-CW radar apparatus which switches between transmission and reception by time division control according to the present invention comprises: a mixer for downconverting an IF signal; a switch provided on an input side of the mixer; and a switch controller for controlling the switch on and off in different modes and selecting the IF signal in the different modes for supply to the mixer.

In one preferred mode of the invention, the radar apparatus comprises a plurality of mixers, each for downconverting the IF signal, and a plurality of switches one each provided on the input side of each of the plurality of mixers, and the switch controller controls the plurality of switches on and off in different modes and selects the IF signal in the different modes for supply to the plurality of mixers respectively (FIG. 7).

In another preferred mode of the invention, the radar apparatus comprises: a selector switch for supplying the IF signal to each of the plurality of mixers by switching a connection thereof between the mixers; and a switching controller for controlling timing for connecting the selector switch to each of the plurality of mixers, and for causing the selector switch to select the IF signal in the different modes for supply to each of the plurality of mixers (FIG. 12).

According to the transmit-receive FM-CW radar apparatus of the present invention, the mixer for downconverting the IF signal is a single mixer, and the radar apparatus includes: a switch for turning on and off the IF signal to be input to the mixer; and a mode selector for controlling the switch on and off in different modes while selecting the on/off mode by switching between the different modes (FIG. 14).

According to the transmit-receive FM-CW radar apparatus of the present invention, the mixer for downconverting the IF signal is a single mixer, and the switch for turning on and off the IF signal to be input to the mixer is provided on the input side of the mixer, wherein the radar apparatus includes a mode controller for turning the switch on and off in a specific mode (FIG. 16).

The different modes consist of a short-range mode for selecting an IF signal containing a signal from a short-range target, a mid-range mode for selecting an IF signal containing a signal from a mid-range target, and a long-range mode for selecting an IF signal containing a signal from a long-range target (FIGS. 9 and 10).

The mode selector switches the mode to any one of the different modes, i.e., the short-range mode, the mid-range mode, or the long-range mode. Alternatively, the mode selector switches the mode sequentially through the short-range mode, the mid-range mode, and the long-range mode (FIGS. 9 and 10).

The specific mode is any one of the above modes, i.e., the short-range mode, the mid-range mode, or the long-range mode (FIGS. 9 and 10).

The different modes consist of a mode for selecting an IF signal corresponding to a portion occupying up to a point about ⅓ from the leading edge of a receive timing interval, a mode for selecting an IF signal corresponding to a portion occupying up to a point about ⅔ from the leading edge of the receive timing interval, and a mode for selecting an IF signal corresponding to an entire portion of the receive timing interval (FIG. 9).

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