{"id":{"repo_id":"aalto","oai_identifier":"oai:aaltodoc.aalto.fi:123456789/131558"},"canonical_url":"https://search.dev.ndltd.org/etd/aalto/oai:aaltodoc.aalto.fi:123456789/131558","repository":{"repo_id":"aalto","name":"Aalto University","base_url":"https://aaltodoc.aalto.fi/server/oai/request"},"display":{"title":"The Gopher Antenna: A New Type of Ground Penetrating Radar Antenna","abstract":"Currently, ground penetrating radar (GPR) antennas for ground-coupled setups are inefficient. They use resistors and/or dissipative material to improve the impedance bandwidth and thus achieve optimal pulse shape. These antennas are mostly bowtie dipoles and have an omnidirectional pattern, although the casing and the electrical properties of the ground modify the pattern. The center frequency of the antennas in free space is often 500 MHz, and the required bandwidth is wide: the spectrum ratio is from 1:2 to 1:10 at a −10 dB limit. The phase center must remain stable over the whole bandwidth. The main objective of this dissertation is to develop an antenna that is more efficient and has good directivity. The concept of a patch antenna with a dual resonant structure was used as a basis. To achieve this goal, a feed antenna with three resonant frequencies was used. The novel point in the design is the second resonant frequency (not the first, as is typical) of the feed that is matched to the line impedance by a coupled dual resonant parasitic patch structure. Around the center frequency, the matching is good, and there are no dissipative materials. Therefore, the antenna is efficient. The radiated spectrum expands well beyond the matched impedance area and thus is not efficient in that part of the radiated spectrum, but it provides a Gaussian spectrum which is preferred by GPR users. The patch antenna design provides an inherent directivity, often 9 dBi, and combining the feed improves the directivity further. For practical reasons, this antenna type was given the name the \"Gopher antenna\". A reasonably priced GPR without an antenna was provided by one manufacturer. This was partly modified by the author to fit better the Gopher antenna so that the tests could be performed. Measurements were done in settings where there were known objects underground, and on a lake where the lake bottom was visible. The received data needed extensive processing. The sophisticated free software for the processing did not read the files from the system, thus a simple processing software was designed by the author. This had the advantage of enabling the testing of various pre- and postprocessing methods, and the trace integration method with optional deconvolution and cross-correlation methods were found to be useful with this data. The antenna was implemented, and the measured results validate the concept. The lake profiles are quite clear, and the ground profiles show reflections from known objects in the expected size range. As there was no standard way of describing the antenna radiation in the ground, I propose that the highest electric field magnitude is stored in each FDTD pixel during the simulation. This provides a useful graphic with which to compare antenna patterns. The pattern was also tested in a case study by tilting the antenna. With this efficient and directive antenna, the GPR is expected to see deeper.","abstract_html":"Currently, ground penetrating radar (GPR) antennas for ground-coupled setups are inefficient. They use resistors and/or dissipative material to improve the impedance bandwidth and thus achieve optimal pulse shape. These antennas are mostly bowtie dipoles and have an omnidirectional pattern, although the casing and the electrical properties of the ground modify the pattern. The center frequency of the antennas in free space is often 500 MHz, and the required bandwidth is wide: the spectrum ratio is from 1:2 to 1:10 at a −10 dB limit. The phase center must remain stable over the whole bandwidth. The main objective of this dissertation is to develop an antenna that is more efficient and has good directivity. The concept of a patch antenna with a dual resonant structure was used as a basis. To achieve this goal, a feed antenna with three resonant frequencies was used. The novel point in the design is the second resonant frequency (not the first, as is typical) of the feed that is matched to the line impedance by a coupled dual resonant parasitic patch structure. Around the center frequency, the matching is good, and there are no dissipative materials. Therefore, the antenna is efficient. The radiated spectrum expands well beyond the matched impedance area and thus is not efficient in that part of the radiated spectrum, but it provides a Gaussian spectrum which is preferred by GPR users. The patch antenna design provides an inherent directivity, often 9 dBi, and combining the feed improves the directivity further. For practical reasons, this antenna type was given the name the "Gopher antenna". A reasonably priced GPR without an antenna was provided by one manufacturer. This was partly modified by the author to fit better the Gopher antenna so that the tests could be performed. Measurements were done in settings where there were known objects underground, and on a lake where the lake bottom was visible. The received data needed extensive processing. The sophisticated free software for the processing did not read the files from the system, thus a simple processing software was designed by the author. This had the advantage of enabling the testing of various pre- and postprocessing methods, and the trace integration method with optional deconvolution and cross-correlation methods were found to be useful with this data. The antenna was implemented, and the measured results validate the concept. The lake profiles are quite clear, and the ground profiles show reflections from known objects in the expected size range. As there was no standard way of describing the antenna radiation in the ground, I propose that the highest electric field magnitude is stored in each FDTD pixel during the simulation. This provides a useful graphic with which to compare antenna patterns. The pattern was also tested in a case study by tilting the antenna. With this efficient and directive antenna, the GPR is expected to see deeper.","abstract_has_math":false,"creators":["Voipio, Veli"],"institution":"Aalto University","degree_name":null,"degree_level":null,"degree_discipline":null,"degree_department":"Elektroniikan ja nanotekniikan laitos","school":null,"contributors":["Aalto-yliopisto","Aalto University"],"advisors":["Viikari, Ville, Prof., Aalto University, Department of Electronics and Nanoengineering, Finland"],"committee_chairs":[],"committee_members":[],"year":2024,"date_issued":"2024","date_published":"2024","updated_at":"2026-08-21T22:21:56Z","subjects":[],"languages":["en"],"rights":[],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"https://aaltodoc.aalto.fi/handle/123456789/131558","outbound_label":"Repository record","outbound_source":"dc:identifier.uri"},"source_record":{"url":"https://aaltodoc.aalto.fi/server/oai/request?verb=GetRecord&metadataPrefix=dim&identifier=oai%3Aaaltodoc.aalto.fi%3A123456789%2F131558","prefix":"dim"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Aalto-yliopisto","Aalto University"]},{"key":"dc:contributor.advisor","label":"Advisor","values":["Viikari, Ville, Prof., Aalto University, Department of Electronics and Nanoengineering, Finland"]},{"key":"dc:contributor.department","label":"Department","values":["Elektroniikan ja nanotekniikan laitos","Department of Electronics and Nanoengineering"]},{"key":"dc:contributor.supervisor","label":"Supervisor","values":["Viikari, Ville, Prof., Aalto University, Department of Electronics and Nanoengineering, Finland"]},{"key":"dc:creator","label":"Author","values":["Voipio, Veli"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date.accessioned","label":"Dc Date Accessioned","values":["2024-11-12T10:00:13Z"]},{"key":"dc:date.available","label":"Dc Date Available","values":["2024-11-12T10:00:13Z"]},{"key":"dc:date.issued","label":"Date","values":["2024"]},{"key":"dc:publisher","label":"Institution","values":["Aalto University","Aalto-yliopisto"]},{"key":"dc:type","label":"Dc Type","values":["G5 Artikkeliväitöskirja"]},{"key":"dc:type.dcmitype","label":"Dc Type Dcmitype","values":["text"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language.iso","label":"Language (ISO)","values":["en"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier.uri","label":"Identifier URI","values":["https://aaltodoc.aalto.fi/handle/123456789/131558"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description.abstract","label":"Abstract","values":["Currently, ground penetrating radar (GPR) antennas for ground-coupled setups are inefficient. They use resistors and/or dissipative material to improve the impedance bandwidth and thus achieve optimal pulse shape. These antennas are mostly bowtie dipoles and have an omnidirectional pattern, although the casing and the electrical properties of the ground modify the pattern. The center frequency of the antennas in free space is often 500 MHz, and the required bandwidth is wide: the spectrum ratio is from 1:2 to 1:10 at a −10 dB limit. The phase center must remain stable over the whole bandwidth. The main objective of this dissertation is to develop an antenna that is more efficient and has good directivity. The concept of a patch antenna with a dual resonant structure was used as a basis. To achieve this goal, a feed antenna with three resonant frequencies was used. The novel point in the design is the second resonant frequency (not the first, as is typical) of the feed that is matched to the line impedance by a coupled dual resonant parasitic patch structure. Around the center frequency, the matching is good, and there are no dissipative materials. Therefore, the antenna is efficient. The radiated spectrum expands well beyond the matched impedance area and thus is not efficient in that part of the radiated spectrum, but it provides a Gaussian spectrum which is preferred by GPR users. The patch antenna design provides an inherent directivity, often 9 dBi, and combining the feed improves the directivity further. For practical reasons, this antenna type was given the name the \"Gopher antenna\". A reasonably priced GPR without an antenna was provided by one manufacturer. This was partly modified by the author to fit better the Gopher antenna so that the tests could be performed. Measurements were done in settings where there were known objects underground, and on a lake where the lake bottom was visible. The received data needed extensive processing. The sophisticated free software for the processing did not read the files from the system, thus a simple processing software was designed by the author. This had the advantage of enabling the testing of various pre- and postprocessing methods, and the trace integration method with optional deconvolution and cross-correlation methods were found to be useful with this data. The antenna was implemented, and the measured results validate the concept. The lake profiles are quite clear, and the ground profiles show reflections from known objects in the expected size range. As there was no standard way of describing the antenna radiation in the ground, I propose that the highest electric field magnitude is stored in each FDTD pixel during the simulation. This provides a useful graphic with which to compare antenna patterns. The pattern was also tested in a case study by tilting the antenna. With this efficient and directive antenna, the GPR is expected to see deeper.","Nykyisten maaperätutkan antennien hyötysuhde on useimmiten huono, koska niissä käytetään vastuksia hyvänmuotoisen pulssin saavuttamiseksi. Niissä käytetään tavallisimmin rusettityyppistä dipoliantennia ja niiden suuntakuvio on ympärisäteilevä, joskin antennin kotelo ja maaperä vaikuttavat suunta¬kuvioon. Näiden antennien keskitaajuus on 500 MHz:n luokkaa vapaassa tilassa ja niiltä vaaditaan hyvin leveää taajuuskaistaa: taajuussuhde 1:2 ja 1:10 välillä 10 dB rajalla. Vaihekeskipisteen tulee olla vakaa koko taajuusalueella. Tämän väitöskirjan tavoitteena on kehittää antenni, jolla on hyvä hyötysuhde ja joka on suuntaava. Kehitystyö on tehty mikroliuska-antennitekniikan pohjalta käyttäen kaksoisresonanssipiiriä. Syöttöantennissa on kolme resonanssia. Tässä työssä on uutta se, että käytetään syöttöantennin toista resonanssia (ei siis alinta resonanssia) kytketyn rinnalla värähtelevän mikroliuska-antennin kanssa. Antennin keskitaajuudella impedanssisovitus on hyvä. Koska antennirakenteessa ei ole häviöllisiä materiaaleja, antennin hyötysuhde on hyvä. Antennin säteilevä spektri on paljon laajempi kuin sovitetun impedanssispektrin alue, joten koko spektrin alueella hyötysuhde ei ole yhtä hyvä, mutta antenni tuottaa Gaussin käyrän mukaisen spektrin, jota maaperätutkan käyttäjät suosivat. Mikroliuska-antenni on luonnostaan suuntaava, usein 9 dBi, ja tämä yhdessä syöttöantennin ja toisen antennin kanssa vielä parantaa sitä. Käytännöllisistä syistä antennille annettiin lyhyt nimi: Gopher (taskurotta) -antenni. Nykyiset maaperätutkat ovat kalliita laitteita \"mustassa laatikossa\". Yksi valmistaja antoi kuitenkin käyttöön kohtuuhintaisen maaperätutkan ilman antennia. Kirjoittaja muokkasi sitä hieman uuden antennin toiminnan mittauksia varten. Mittauksia tehtiin paikoissa, joissa on tunnettuja kohteita maan alla, ja järvessä, jonka pohja näkyi. Mittausdataa täytyy jälkikäsitellä paljon. Koska käyttöön ei löytynyt sopivaa valmisohjelmisto¬kokonaisuutta, kirjoittaja teki omaa koodia. Siitä oli se hyöty, että kirjoittaja saattoi kokeilla uusia vaihtoehtoja ja mitatun datan integrointi osoittautui hyväksi ristikorrelaation kanssa. Tässä työssä antenni on toteutettu ja se on mitattu toiminnan varmistamiseksi. Järvestä saadut mittausprofiilit ovat selkeitä ja maasta mitatut profiilit näyttävät heijastuksia tunnetuista kohteista. Toistaiseksi ei ole yleisesti sovittua tapaa esittää antennin säteilyä maassa antennin lähellä, joten tein ehdotuksen: simulaatiossa jokaisessa ruudussa tallennetaan suurin sähkökentän arvo simulaation aikana. Sen pohjalta tehty kuva antaa mahdollisuuden verrata antennien säteilyä maassa. Säteilyn suuntaavuutta testattiin myös kallistamalla antennia maan suhteen. Koska tehty antenni on tehokas ja suuntaava, sen odotetaan näkevän syvemmälle kuin nykyiset maaperätutkan antennit."]},{"key":"dc:format.mimetype","label":"Dc Format Mimetype","values":["application/pdf"]},{"key":"dc:title","label":"Title","values":["The Gopher Antenna: A New Type of Ground Penetrating Radar Antenna","Gopher antenni: Uudentyyppinen maaperätutkan antenni"]}]}],"canonical_facts":{"dc:contributor":["Aalto-yliopisto","Aalto University"],"dc:contributor.advisor":["Viikari, Ville, Prof., Aalto University, Department of Electronics and Nanoengineering, Finland"],"dc:contributor.department":["Elektroniikan ja nanotekniikan laitos","Department of Electronics and Nanoengineering"],"dc:contributor.supervisor":["Viikari, Ville, Prof., Aalto University, Department of Electronics and Nanoengineering, Finland"],"dc:creator":["Voipio, Veli"],"dc:date.accessioned":["2024-11-12T10:00:13Z"],"dc:date.available":["2024-11-12T10:00:13Z"],"dc:date.issued":["2024"],"dc:description.abstract":["Currently, ground penetrating radar (GPR) antennas for ground-coupled setups are inefficient. They use resistors and/or dissipative material to improve the impedance bandwidth and thus achieve optimal pulse shape. These antennas are mostly bowtie dipoles and have an omnidirectional pattern, although the casing and the electrical properties of the ground modify the pattern. The center frequency of the antennas in free space is often 500 MHz, and the required bandwidth is wide: the spectrum ratio is from 1:2 to 1:10 at a −10 dB limit. The phase center must remain stable over the whole bandwidth. The main objective of this dissertation is to develop an antenna that is more efficient and has good directivity. The concept of a patch antenna with a dual resonant structure was used as a basis. To achieve this goal, a feed antenna with three resonant frequencies was used. The novel point in the design is the second resonant frequency (not the first, as is typical) of the feed that is matched to the line impedance by a coupled dual resonant parasitic patch structure. Around the center frequency, the matching is good, and there are no dissipative materials. Therefore, the antenna is efficient. The radiated spectrum expands well beyond the matched impedance area and thus is not efficient in that part of the radiated spectrum, but it provides a Gaussian spectrum which is preferred by GPR users. The patch antenna design provides an inherent directivity, often 9 dBi, and combining the feed improves the directivity further. For practical reasons, this antenna type was given the name the \"Gopher antenna\". A reasonably priced GPR without an antenna was provided by one manufacturer. This was partly modified by the author to fit better the Gopher antenna so that the tests could be performed. Measurements were done in settings where there were known objects underground, and on a lake where the lake bottom was visible. The received data needed extensive processing. The sophisticated free software for the processing did not read the files from the system, thus a simple processing software was designed by the author. This had the advantage of enabling the testing of various pre- and postprocessing methods, and the trace integration method with optional deconvolution and cross-correlation methods were found to be useful with this data. The antenna was implemented, and the measured results validate the concept. The lake profiles are quite clear, and the ground profiles show reflections from known objects in the expected size range. As there was no standard way of describing the antenna radiation in the ground, I propose that the highest electric field magnitude is stored in each FDTD pixel during the simulation. This provides a useful graphic with which to compare antenna patterns. The pattern was also tested in a case study by tilting the antenna. With this efficient and directive antenna, the GPR is expected to see deeper.","Nykyisten maaperätutkan antennien hyötysuhde on useimmiten huono, koska niissä käytetään vastuksia hyvänmuotoisen pulssin saavuttamiseksi. Niissä käytetään tavallisimmin rusettityyppistä dipoliantennia ja niiden suuntakuvio on ympärisäteilevä, joskin antennin kotelo ja maaperä vaikuttavat suunta¬kuvioon. Näiden antennien keskitaajuus on 500 MHz:n luokkaa vapaassa tilassa ja niiltä vaaditaan hyvin leveää taajuuskaistaa: taajuussuhde 1:2 ja 1:10 välillä 10 dB rajalla. Vaihekeskipisteen tulee olla vakaa koko taajuusalueella. Tämän väitöskirjan tavoitteena on kehittää antenni, jolla on hyvä hyötysuhde ja joka on suuntaava. Kehitystyö on tehty mikroliuska-antennitekniikan pohjalta käyttäen kaksoisresonanssipiiriä. Syöttöantennissa on kolme resonanssia. Tässä työssä on uutta se, että käytetään syöttöantennin toista resonanssia (ei siis alinta resonanssia) kytketyn rinnalla värähtelevän mikroliuska-antennin kanssa. Antennin keskitaajuudella impedanssisovitus on hyvä. Koska antennirakenteessa ei ole häviöllisiä materiaaleja, antennin hyötysuhde on hyvä. Antennin säteilevä spektri on paljon laajempi kuin sovitetun impedanssispektrin alue, joten koko spektrin alueella hyötysuhde ei ole yhtä hyvä, mutta antenni tuottaa Gaussin käyrän mukaisen spektrin, jota maaperätutkan käyttäjät suosivat. Mikroliuska-antenni on luonnostaan suuntaava, usein 9 dBi, ja tämä yhdessä syöttöantennin ja toisen antennin kanssa vielä parantaa sitä. Käytännöllisistä syistä antennille annettiin lyhyt nimi: Gopher (taskurotta) -antenni. Nykyiset maaperätutkat ovat kalliita laitteita \"mustassa laatikossa\". Yksi valmistaja antoi kuitenkin käyttöön kohtuuhintaisen maaperätutkan ilman antennia. Kirjoittaja muokkasi sitä hieman uuden antennin toiminnan mittauksia varten. Mittauksia tehtiin paikoissa, joissa on tunnettuja kohteita maan alla, ja järvessä, jonka pohja näkyi. Mittausdataa täytyy jälkikäsitellä paljon. Koska käyttöön ei löytynyt sopivaa valmisohjelmisto¬kokonaisuutta, kirjoittaja teki omaa koodia. Siitä oli se hyöty, että kirjoittaja saattoi kokeilla uusia vaihtoehtoja ja mitatun datan integrointi osoittautui hyväksi ristikorrelaation kanssa. Tässä työssä antenni on toteutettu ja se on mitattu toiminnan varmistamiseksi. Järvestä saadut mittausprofiilit ovat selkeitä ja maasta mitatut profiilit näyttävät heijastuksia tunnetuista kohteista. Toistaiseksi ei ole yleisesti sovittua tapaa esittää antennin säteilyä maassa antennin lähellä, joten tein ehdotuksen: simulaatiossa jokaisessa ruudussa tallennetaan suurin sähkökentän arvo simulaation aikana. Sen pohjalta tehty kuva antaa mahdollisuuden verrata antennien säteilyä maassa. Säteilyn suuntaavuutta testattiin myös kallistamalla antennia maan suhteen. Koska tehty antenni on tehokas ja suuntaava, sen odotetaan näkevän syvemmälle kuin nykyiset maaperätutkan antennit."],"dc:format.mimetype":["application/pdf"],"dc:identifier.uri":["https://aaltodoc.aalto.fi/handle/123456789/131558"],"dc:language.iso":["en"],"dc:publisher":["Aalto University","Aalto-yliopisto"],"dc:title":["The Gopher Antenna: A New Type of Ground Penetrating Radar Antenna","Gopher antenni: Uudentyyppinen maaperätutkan antenni"],"dc:type":["G5 Artikkeliväitöskirja"],"dc:type.dcmitype":["text"]},"updated_at":"2026-08-21T22:21:56Z"}