Furuno GN-86F, GN-87F, GN-8615, GN-8715, GV-86 User Manual

...

FURUNO GPS/ GNSS Receiver

Model: GN-86/87, GV-86/87 and

GT-86/87 Series

User’s Design Guide

(Document No. SE13-900-001-06)

FURUNO GPS/GNSS Receiver 86/87 Series User's Design Guide

SE13-900-001-06

IMPORTANT NOTICE

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FURUNO does not warrant that the functions contained in the "Application Note" will meet your requirements, or that the operation of the "Application Note" will be uninterrupted or error-free, or that defects in the "Application Note" will be corrected.

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FURUNO GPS/GNSS Receiver 86/87 Series User's Design Guide

SE13-900-001-06

Version

Description

Date

Initial release

2013.06.07

2nd preliminary release

2013.06.14

3rd preliminary release

2013.07.18 3 Formal revision release

2013.12.11

Corrected Figure 3-1, 3-2 and 3-6

Updated Chapter 1, Chapter 6 and Contact Information

2014.10.09

Corrected the cover

2015.05.26 6 Corrected section 3.5.1

2015.10.30

Revision History

FURUNO GPS/GNSS Receiver 86/87 Series User's Design Guide

SE13-900-001-06

Table of contents

1 General Description ········································································································ 1 2 RF Section PCB Layout Design ························································································ 1

2.1 PCB Ground Layout Design ······················································································· 3

2.2 Microstrip Line Design ······························································································ 4

2.3 ESD protection by λ/4 short stub ················································································ 6

2.4 DC Feed Inductor ······································································································ 8

3 Antenna Interface ········································································································· 11

3.1 LNA Gain Selection ································································································· 11

3.2 Bias Circuit Design for Active Antenna ····································································· 12

3.3 Passive Antenna Connection ··················································································· 13

3.4 SAW Filter Insertion ································································································ 14

3.5 Antenna Detection Circuit ························································································ 15

3.5.1 Antenna Detection Circuit Overview ··································································· 15

3.5.2 Antenna Detection/Protection Circuit ·································································· 16

3.5.3 Modification of Antenna Short/Open Threshold ··················································· 18

3.5.4 Modification of Over Current Protection Threshold ·············································· 18

3.6 Layout design with Patch Antenna ··········································································· 19

3.6.1 Incurrence to Antenna characteristics by layout ·················································· 19

3.6.2 Noise Influence Issue by Layout ········································································· 24 4 Bypass Capacitor for VCC ····························································································· 25 5 Mechanical Stress Control····························································································· 25 6 Related Documents ······································································································ 26 7 Contact Information ······································································································ 26

FURUNO GPS/GNSS Receiver 86/87 Series User's Design Guide

SE13-900-001-06

:λ/4 Short Stub Block

:Active Antenna Power Supply Line : 1.5GHz / 1.6GHz 50Ω Microstrip Line

　: Ground

39nH DC Feed Inductor

33pF Capacitor

Antenna Connector (for connecting an active antenna)

#11 RF_IN #12 GND

#10 GND

86/87 Series

Module

λ/4 Short Stub

50Ω Microstrip Line

1 General Description

This document presents the useful design guidance to improve the performance and the quality of our customers’ products that contain FURUNO 86/87 series GPS/GNSS receiver modules (86/87 series module) listed as below.

- GN-86F - GV-86 - GT-86

- GN-87F - GV-87 - GT-87

- GN-8615 - GV-8615

- GN-8715 - GV-8715 Please insure the quality of your own design with the final design guide.

2 RF Section PCB Layout Design

Figure 2-1 shows an overview of the RF section PCB design for using the active antenna. 39nH inductor is placed to bias the active antenna, 33pF capacitor is placed to block the DC voltage, and

λ/4 short stub works to bypass ESD noise to the ground. The line from the antenna connector to RF_IN pin through 33pF capacitor should be designed to have 50Ω

characteristic impedance with using the PCB design technique known as microstrip line. Since the input impedance of 86/87 series module is design to be 50Ω, so it is not needed to place 50Ω matching network between the antenna connector through the receiver RF_IN pin.

Figure 2-1 RF Section PCB Layout Design Overview for Active Antenna

FURUNO GPS/GNSS Receiver 86/87 Series User's Design Guide

SE13-900-001-06

:λ/4 Short Stub

: 1.5GHz / 1.6GHz 50Ω Micro Strip Line

　: Ground

Passive Antenna (Patch Antenna)

#11 RF_IN #12 GND

#10 GND

86/87 Series

Module

λ/4 Short Stub

50Ω Microstrip Line

Figure 2-2 shows an overview of the RF section PCB design for using the passive antenna. There is no need to bias the antenna, so 39nH inductor and 33pF capacitor are removed from Figure 2-1.

But λ/4 short stub is placed to keep the higher robustness against ESD noise. The routing between the passive antenna and RF_IN should be designed as 50Ω microstrip line, and there

is no need to place any matching network externally as same as the active antenna case.

Figure 2-2 RF Section PCB Layout Design Overview for Passive Antenna

FURUNO GPS/GNSS Receiver 86/87 Series User's Design Guide

SE13-900-001-06

33pF Capacitor

Antenna

Connector

#11 RF_IN #12 GND

#10 GND

86/87 Series

Module

λ/4 Short Stub

50Ω Micro Strip Line

Jumper Resistor

DC Feed Inductor

(39nH)

2.1 PCB Ground Layout Design

At the bottom of the module, there are some signal lines and via holes. For avoiding any signal shortage, please do not put any signal line nor via hole at the part of the user’s board where is facing to the bottom of the module. This also contributes to reduce noise influence.

If a double-sided board is used, the back side of the RF line should be a ground plane. If a multi-layer board is used, the 2nd layer below the RF line should be a ground plane.

For better noise suppression, the guarding ground plane around the RF signal line is also recommended. Details are described in Section 2.2.

Figure 2-3 An Example of PCB Design around RF Section in Evaluation Kit

FURUNO GPS/GNSS Receiver 86/87 Series User's Design Guide

SE13-900-001-06

2.2 Microstrip Line Design

The PCB design of RF line from the antenna connector to RF_IN pin is very important for keeping the reception sensitivity performance of the receiver module. For achieving the best performance, please follow the design guidelines below.

- Use the microstrip line for RF line to keep 50Ω characteristic impedance.

- Make the length of RF line as short as possible.

- Do not place any digital signal source nor signal line around RF line.

- Use guarding ground plane for decoupling the noise source such as Figure 2-6.

The microstrip line is the most popular technique to obtain 50Ω characteristic impedance line on usual PCB. The basic structure is shown at the bottom-right in Figure 2-4. The conductor part at the upper side is the signal transmission path, and the conductor part at the lower side is ground. The characteristic impedance (Zc) of microstrip line is determined by the following parameters relevant to the specifications of PCB materials.

- Dielectric constant of PCB: Er

- Distance between signal line and ground: H

- Signal line thickness: Tmet

- Signal line width: W

For the calculation of the characteristic impedance, Microstrip Analysis/Synthesis Calculator

(*1)

(MASC) is recommended, which is a free software, useful to design the microstrip line onto customer’s board. Figure 2-4 shows an example of the calculation result by MASC. For details, please see the web site below.

The transmission loss per length of the microstrip line is determined by the following parameters relevant to the specifications of PCB materials.

- Metal resistivity relative to copper: Rho

- Loss tangent of the dielectric: Tanσ

- Metal surface roughness: Rough

reserved). See URL below.

http://mcalc.sourceforge.net/,

Figure 2-4 An Example of Microstrip Line Design by MASC

FURUNO GPS/GNSS Receiver 86/87 Series User's Design Guide

SE13-900-001-06

MSub

MLIN

MSUB

Term Term

TL7

MSub1

Term1 Term2

L=23.5 mm

W=0.31 mm

Subst="MSub1"

Cond=5.96e7

Rough=0.00127 mm

TanD=0.018

T=0.043 mm

Hu=1000 mm

Mur=1

Er=4.3

H=0.178 mm

Z=50 Ohm

Num=1

Z=50 Ohm

Num=2

0.5 1.0 1.5 2.0 2.50.0 3.0

-1.75

-1.50

-1.25

-1.00

-0.75

-0.50

-0.25

-2.00

0.00

freq, GHz

dB(S(2,1))

Transmission, dB

m1 freq= dB(S(2,1))=-0.181

1.589GHz

Figure 2-5 shows Transmission Loss-Frequency characteristics of the microstrip line shown in Figure 2-4. It is simulated by Agilent ADSTM.

Figure 2-5 Simulation Result on Transmission Loss-Frequency Characteristics of the Microstrip line

by Agilent ADSTM

Usually the microstrip line is routed at the surface layer of the PCB, and it is not protected from the radio interference. So sometimes the interference causes the degradation of the receiver performance. In such case, the guarding ground plane can improve the performance with decoupling the interference noise source. The guarding ground plane is the ground placed around the microstrip line as shown in Figure 2-6. The important thing for designing and layouting the guarding ground plane is to keep the gap between the microstrip line and guarding ground plane wider than the microstrip line width. Otherwise this line is not able to work as microstrip line but coplanar line.

Figure 2-6 Example of Layout of Microstrip Line

+ 21 hidden pages

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