BACKGROUND

Technological Field

The present invention relates to an antenna device.

Description of the Related Art

Conventionally, there is a navigation satellite system that measures a position of a moving object such as a motor vehicle. In the navigation satellite system, a receiver provided in the moving object receives a signal transmitted from a satellite of the navigation satellite system with an antenna device, and uses the received signal to measure the position of the moving object itself. GPS (Global Positioning System) is known as a communication standard of the navigation satellite system. GPS is a standard in the United States, and the frequency bands of carrier waves include an L1 band (center frequency: 1575.42 [MHz]), L2 band (center frequency: 1227.60 [MHz]), L3 band, L4 band, and L5 band (center frequency: 1176.45: [MHz]), depending on its usage and the like.

Furthermore, GLONASS (Global Navigation Satellite System) is known as a communication standard of a Russian navigation satellite system, and the frequency bands of carrier waves include an L1 band (center frequency: 1598.0625 [MHz] to 1605.375 [MHz]), L2 band (center frequency: 1242.9375 [MHz] to 1248.625 [MHz]), and the like. QZSS (Quasi-Zenith Satellite System, Michibiki) is known as a communication standard of a Japanese navigation satellite system, and uses an L1 band, L2 band, L5 band, L6 band (LEX (L-band EXperiment), center frequency: 1278.75 [MHz]), and the like. Thus, there are known various standards of navigation satellite system using different frequencies.

There is known an antenna device that receives signals in the L1 band (for code positioning) and the L2 band (for carrier wave positioning) of GPS in order to improve the positioning accuracy. Such an antenna device for two frequency bands has a dielectric substrate with two loop antenna elements for the L1 band and the L2 band thereon.

Another antenna device for two frequency bands is known to be a stacked patch antenna provided with a first single-feed patch antenna having a feed pin and a dielectric layer that deals with a frequency band of SDARS (Satellite Digital Audio Radio Service), and a second single-feed patch antenna having a feed pin and a dielectric layer that deals with a frequency band of GPS (see Japanese Patent Application Publication No. 2009-506730).

However, in the above-described antenna device having the two loop antenna elements and the above-described stacked patch antenna, a good axial ratio can be obtained only from limited frequency ranges, for example, from the L1 band of GPS and the L2 band of GPS, but not from the L1 band of GPS and the L1 band of GLONASS or from the L2 band of GPS and the L2 band of GLONASS. Generally, a two-feed patch antenna can deal with larger bandwidths, however, an active antenna requires one block of an LNA (Low Noise Amplifier) for each frequency band.

SUMMARY

An object of the present invention is to simplify a circuit configuration that deals with a plurality of frequency bands.

In order to solve the above problems, according to an aspect of the present invention, there is provided an antenna device including:

an antenna unit that receives radio waves of a plurality of first frequency bands and outputs received signals; and

a first band pass filter that transmits, out of the received signals that are output, received signals of at least two second frequency bands out of the first frequency bands.

