Radar tech­nol­o­gy in vehi­cles plays a piv­otal role in enhanc­ing safe­ty, com­fort, and con­ve­nience for dri­vers and pas­sen­gers alike.  By uti­liz­ing elec­tro­mag­net­ic waves to detect objects and obsta­cles in the vehicle’s vicin­i­ty, radar sys­tems pro­vide crit­i­cal infor­ma­tion to onboard com­put­er sys­tems, enabling a range of advanced dri­ver assis­tance fea­tures. These include adap­tive cruise con­trol, which auto­mat­i­cal­ly adjusts vehi­cle speed to main­tain a safe dis­tance from the vehi­cle ahead, col­li­sion avoid­ance sys­tems that pro­vide warn­ings or inter­ven­tion to pre­vent acci­dents, and park­ing assis­tance sys­tems that aid dri­vers in maneu­ver­ing into tight spaces with pre­ci­sion. By inte­grat­ing radar sen­sors into vehi­cles, man­u­fac­tur­ers can sig­nif­i­cant­ly reduce the like­li­hood of acci­dents, improve over­all dri­ving expe­ri­ences, and pave the way for the devel­op­ment of autonomous dri­ving tech­nolo­gies in the future. Auto­mo­tive radars oper­ate on spe­cif­ic fre­quen­cy bands. Over time, a sig­nif­i­cant tran­si­tion has tak­en place, mov­ing from the tra­di­tion­al 24 GHz band to the more advanced and flex­i­ble 77 GHz band. This arti­cle explores the rea­sons behind this shift and sheds light on the advan­tages of the 77 GHz band over the 24 GHz band.

Frequency Bands Dedicated to Automotive Radars

Auto­mo­tive radars pri­mar­i­ly use four fre­quen­cy bands glob­al­ly, includ­ing the 24 GHz and 77 GHz bands. The table below sum­ma­rizes these bands, high­light­ing their respec­tive char­ac­ter­is­tics:

Transition in Europe

The 24 GHz band had been tem­porar­i­ly used for auto­mo­tive radars in Europe for col­li­sion avoid­ance and oth­er safe­ty appli­ca­tions. How­ev­er, due to increas­ing demand for spec­trum and reg­u­la­to­ry changes, fur­ther use of the 24 GHz band for auto­mo­tive radars is no longer fea­si­ble.

The FCC (Fed­er­al Com­mu­ni­ca­tions Com­mis­sion) in the Unit­ed States and the Euro­pean Telecom­mu­ni­ca­tions Stan­dards Insti­tute (ETSI) have imposed spec­trum reg­u­la­tions that affect the use of the 24 GHz band for auto­mo­tive radars. These reg­u­la­tions may restrict or phase out the use of the 24 GHz band for auto­mo­tive radar appli­ca­tions.

In response to these reg­u­la­to­ry changes, the Euro­pean Com­mis­sion has pro­posed tran­si­tion­ing to the 77 GHz band for auto­mo­tive radars as a replace­ment for the 24 GHz band. The 77 GHz band is inter­na­tion­al­ly avail­able and offers sev­er­al advan­tages over the 24 GHz band, mak­ing it per­fect­ly ade­quate for auto­mo­tive radar appli­ca­tions.

Advantages of the 77 GHz Band Over 24 GHz for Automotive Radars

1. Larg­er Avail­able Band­width & Bet­ter Res­o­lu­tion

The 77 GHz fre­quen­cy band for auto­mo­tive radar appli­ca­tions cov­ers the range from 76 to 81 GHz, with a band­width of over 4 GHz, com­pared to a 200 MHz band­width avail­able for auto­mo­tive radar appli­ca­tions at 24 GHz. This wider band­width enhances radar range and veloc­i­ty res­o­lu­tion, enabling the iden­ti­fi­ca­tion of close­ly spaced objects, mak­ing these radars ide­al for auto­mat­ed park­ing appli­ca­tions.

As sen­sors shift from 24 GHz to 77 GHz, veloc­i­ty mea­sure­ments can improve by a fac­tor of 3, thanks to dif­fer­ences in phase between the trans­mit­ted and received sig­nals.

This enhanced res­o­lu­tion also improves the detec­tion and avoid­ance of larg­er objects like cars and allows the avoid­ance of small­er ones, such as pedes­tri­ans. It pro­vides dri­vers with bet­ter object res­o­lu­tion in sit­u­a­tions with poor vis­i­bil­i­ty.

2. Small­er Size

77 GHz radar sys­tems are small­er than their 24 GHz coun­ter­parts are. The lin­ear rela­tion­ship between anten­na size and fre­quen­cy means that the wave­length of 77 GHz sig­nals is one-third of that of a 24 GHz sys­tem. As a result, the area need­ed for a 77 GHz radar anten­na is one-ninth the size of a sim­i­lar 24 GHz anten­na.

3. High­er Pow­er Lev­els

77 GHz radars have high­er per­mit­ted trans­mit pow­er lev­els. The Effec­tive Isotrop­ic Radi­at­ed Pow­er (EIRP) for auto­mo­tive radars in the 77 GHz band is 55 dBm (-3 dBm/MHz), where­as, for 24 GHz radars, the peak lim­it is only 20 dBm EIRP.

These advan­tages are the main rea­sons for the shift from the 24 GHz band to the 77 GHz band.

Use case: South Africa

In South Africa, the reg­u­la­to­ry author­i­ties have des­ig­nat­ed spe­cif­ic fre­quen­cy bands for vehi­cle radar sys­tems to ensure effi­cient and safe oper­a­tion on the road. These bands include 24.05 – 24.075 GHz, 24.075 – 24.15 GHz, and 24.75 – 24.25 GHz, cater­ing to var­i­ous auto­mo­tive radar appli­ca­tions such as adap­tive cruise con­trol, col­li­sion avoid­ance, and park­ing assis­tance. Addi­tion­al­ly, the coun­try allows the use of the 76–77GHz band, known for its high-res­o­lu­tion sens­ing capa­bil­i­ties, fur­ther enhanc­ing the effec­tive­ness of radar-based safe­ty fea­tures in vehi­cles. By allo­cat­ing these fre­quen­cy bands, South Africa aims to facil­i­tate the adop­tion of advanced radar tech­nolo­gies in vehi­cles, con­tribut­ing to improved road safe­ty and dri­ving expe­ri­ences across the coun­try.

The fol­low­ing table shows the bands allowed by ICASA for Road Trans­port and Traf­fic Telem­at­ic appli­ca­tions:

In a nut­shell, radar tech­nol­o­gy in vehi­cles has rev­o­lu­tion­ized auto­mo­tive safe­ty and com­fort, paving the road for a new era of advanced dri­ver assis­tance fea­tures. From adap­tive cruise con­trol to col­li­sion avoid­ance and park­ing assis­tance sys­tems, radar sen­sors have become indis­pens­able com­po­nents in mod­ern vehi­cles, enhanc­ing dri­ver aware­ness and reduc­ing the risk of acci­dents.

The tran­si­tion from the tra­di­tion­al 24 GHz band to the more resource­ful 77 GHz band rep­re­sents a sig­nif­i­cant mile­stone in the evo­lu­tion of auto­mo­tive radar tech­nol­o­gy. With wider band­width, bet­ter res­o­lu­tion, small­er size, and high­er pow­er lev­els, the 77 GHz band offers numer­ous advan­tages over its pre­de­ces­sor, enabling more pre­cise and effi­cient radar sens­ing capa­bil­i­ties. More­over, reg­u­la­to­ry author­i­ties world­wide, includ­ing South Africa, have rec­og­nized the impor­tance of allo­cat­ing spe­cif­ic fre­quen­cy bands for vehi­cle radar sys­tems, ensur­ing safe and effi­cient oper­a­tion on the road.

By embrac­ing advanced radar tech­nolo­gies and reg­u­la­to­ry frame­works, coun­tries can con­tin­ue to improve road safe­ty and dri­ving expe­ri­ences for motorists across the globe, lead­ing the way for a safer and more con­nect­ed future on our roads.