Printed circuit board and diplexer circuit

1. A printed circuit board for forming a diplexer circuit comprising: a first connector for connecting a first filter and a second connector for connecting a second filter, wherein the first connector and the second connector are located on opposite sides of the printed circuit board, wherein the printed circuit board further comprises two layers of a non-conductive substrate and two isolated conductive layers between the two non-conductive substrate layers, the two isolated conductive layers being separated by an isolating layer, wherein the two isolated conductive layers are parallel and forming a wave guide structure, which is configured to a quarter of the wavelength of a center frequency based on a transmission band determined by the first filter and a reception band determined by the second filter, wherein the first filter is electrically connected to the first connector for filtering a transmit signal in the transmission band, and the second filter is electrically connected to the second connector for filtering a receive signal in the reception band, wherein the wave guide structure is located between the first and second filters, wherein the two conductive layers form a projection or shielding around the first connector and the second connector, wherein the two conductive layers are connected through a further connector or a via underneath the first and second connectors, wherein the projection or shielding extends at least a quarter of the wavelength of the center frequency from the further connector or via.

2. The printed circuit board of claim 1 , wherein the first connector corresponds to a first solder-patch and the second connector corresponds to a second solder patch.

3. The printed circuit board of claim 1 comprising at least one first connection or first via between the first connector and the conductive layers, and/or comprising at least one second connection or second via between the second connector and the conductive layer.

4. The printed circuit board of claim 1 , wherein the conductive layers have a connector for grounding the conductive layers.

5. The printed circuit board of claim 1 , wherein the wave guide structure is configured to guide an electromagnetic wave for at least a quarter of a wavelength of the electromagnetic wave.

6. A method for manufacturing a printed circuit board for forming a diplexer circuit comprising: forming a wave guide structure in the printed circuit board comprising two non-conductive substrate layers and two isolated conductive layers between the two non-conductive substrate layers, the two isolated conductive layers being separated by an isolating layer, wherein the two isolated conductive layers are parallel and wherein the wave guide structure is configured to a quarter of the wavelength of a center frequency based on a transmission band determined by the first filter and a reception band determined by the second filter; implementing a first connector for connecting a first filter on a first side of the printed circuit board; and implementing a second connector for connecting a second filter on a second side of the printed circuit board, wherein the first side and the second side are located on opposite sides of the printed circuit board; wherein the wave guide structure is located between the first and second connectors, wherein the conductive layers form a projection or shielding around the first connector and the second connector, wherein the conductive layers are connected through a further connector or a via underneath the first and second connectors, wherein the projection or shielding extends at least a quarter of the wavelength of the center frequency from the further connector or via.

7. A diplexer circuit comprising the circuit board of claim 1 , a first filter connected to the first connector for filtering a transmit signal in a transmission band, and a second filter connected to the second connector for filtering a receive signal in a reception band.

8. The diplexer circuit of claim 7 , wherein the first and the second filters are further connected to an antenna using a first feed-line and a second feed-line, wherein the first feed-line and the second feed-line are located in parallel to the printed circuit board, or wherein the first and the second filter are connected to the antenna using a common antenna port and wherein the printed circuit board comprises a feed connector or via for connecting the first and the second filter to the common antenna port.

9. A method for manufacturing a diplexer, comprising manufacturing a printed circuit board for forming a diplexer circuit according to claim 6 ; mounting a first filter on the first connector; and mounting a second filter on the second connector of the printed circuit board.