broadband vs x band radar

[glennhoward]

could someone explan the difference. thanks, glennhoward, cadet

 

[chuckz]

Re: broadband vs x band radar

There is no "broadband" radar. X band refers to the carrier frequency of the radar. All radar works by sending out a pulse (or series of pulses). Speed and distance is determined by measuring the doppler shift of the reflected pulses.

Police radar operates in either K or X band.

 

[sr280da]

Re: broadband vs x band radar

"There is no "broadband" radar."

Sorry, that statement is not entirely correct. Lowrance is currently marketing a new technology they are referring to as 'Broadband' radar. It uses a lower level of emitted energy and is supposed to have better resolution. The downside is that it has a lower overall range.

The benefits of this type of radar are the reduced levels of microwave energy allowing the scanner to be placed with a little more freedom than traditional radar. The resolution is said to be much better, or at least on par with resolutions obtained from open array systems. I don't know, I have not seen it in action.

As far as the loss of range is concerned, I understand it still has range to the horizon, but the ability to see tall objects over the horizon is limited.

 

[chuckz]

Re: broadband vs x band radar

Because they name their system "broadband" does not necessarily mean it is broadband in engineering terms. There are specific frequency bands allocated to radar, they cannot operate outside of those bands and those bands are pretty narrow. The fact the the CW signal is swept linearly also suggests a relatively narrow band of operation. They are really using CW radar as opposed to pulsed radar.

The lower level of energy is another misnomer. The CW level is certainly less than the peak pulsed power. However the CW is continuous and the pulse intermittent. If you integrate the power over several cycles, the pulse system transmits less power. This is why pulsed system are used, they are much more efficient than CW systems.

The lower range also indicates lower power. If you reduced the pulse system to the same range as the CW system, the pulse system would consume and generate much less power. So if you want the same "benefits" as the CW system out of your pulse system, reduce the plate voltage to the final output.

 

[sr280da]

Re: broadband vs x band radar

You seem to be up on the technical aspects of radar far more than I, good for you. So why didn't you explain this to the OP in your initial response?

 

[Texasmark]

Re: broadband vs x band radar

There is no "broadband" radar. X band refers to the carrier frequency of the radar. All radar works by sending out a pulse (or series of pulses). Speed and distance is determined by measuring the doppler shift of the reflected pulses.

Police radar operates in either K or X band.

Sorry, Doppler and Pulsed RADAR (RADAR DETECTION AND RANGEFINDING) are two separate critters.

Pulsed radar measures the time out and back and displays it on a A scope, J scope, or PPI scope, normally. X band is a good frequency for that ....roughly 10,000 MHz.

Doppler measures the "apparent" change in velocity of the returns; has nothing to do with range. If you don't know what that means, listen to something (airplane, train, truck, car, what have you) coming at you and mentally record the sound as it approaches and the sound as it departs. Totally different sounds because the "Doppler Effect" is increasing as it approaches and decreases and it departs.....but the origin of the sound hasn't changed a bit.

Weather radars you watch on TV have a combination of both; Pulsed radar to give you the range and Doppler to tell you what the weather is doing at that particular range.

The closer the range and the higher the definition required, the higher the frequency. RADAR that will detect rain at 250 miles takes a wide pulse and a low frequency. RADAR that you want to show you a blade of grass 50 feet in front of you takes a very narrow pulse and a very high frequency......and as the frequency increases the losses increase. So for 100W of power at X band to do a job, you may need 200-300W at K bands to do the same job.

Antenna dimensions are part of the frequency. The higher the frequency, the shorter the wavelength, and correspondingly, the smaller the antenna. It would be difficult to have a 30" antenna in a police patrol car to check on speeders if it were operated at X-Band.

K, KA, or KU bands, on the contrary are high enough frequencies that you can have a 4" antenna in the patrol car and get the desired result. The size of the antenna helps to determine the gain which is important in long range measurements. For police work, at short ranges it is a mute point. The K band is in the range of 25 GHz. One GHz is 1,000,000,000 oscillations per second..0 to + max, to 0 to - max, back to 0...one oscillation.......That is fast and there are RADARS that run at 100 GHz (P Band as I recall). The power to your home that runs your light bulbs, TV, microwave, dishwasher, washing machine and all, runs at 60 oscillations per second.

The other thing is that RADAR range is part of the power requirement and antenna gain requirement. A police car is tracking you at 300'; lot of difference in that and tracking weather or a target at 300 miles.

Want more just ask.

Only spent 45 years of my life in the field.....know a little about it.

Mark

 

[bruceb58]

Re: broadband vs x band radar

Sorry, Doppler and Pulsed RADAR (RADAR DETECTION AND RANGEFINDING) are two separate critters.

Actually that is not true either. Pulsed radar can also have doppler on it. Was a radar signal processor designer many years of my engineering career. Designed missile, aircraft and automotive radar systems.

You also don't need to have a pulsed radar to measure range. You can have a pseudo FM radar which will give you both range and speed. You just have to know what frequency you transmitted at time X and compare that to the frequency you received at time Y..subtract the frequencies and you have your range. By modulating it in an up and down linear ramp, you can get doppler and range. It is possible that is what this "broadband radars are doing. We designed this type of radar when I was designing auto collision avoidance systems. Way cheaper than a pulsed system.

EDIT:
Yep..that is what they are doing. Same as what we did with our collision avoidance systems.
http://www.lowrance.com/Products/Marine/Broadband-Radar/The-Technology/

 

[bruceb58]

Re: broadband vs x band radar

The way the broadband radar works is that a frequency is ramped up and then ramped down. Lets say the sweep frequency started at the carrier frequency of 10GHz and ramped up over a second to 10.1 GHz. If the receiver receives 10.05Ghz, you know the delay is 1/2 of a second and range can be calculated. What makes the equation difficult is that if the object is moving, you will have a doppler shift on it so it might be slightly off. In order to compensate for this, they ramp the frequency from 10.1 GHz back down to 10Ghz over 2 seconds instead of 1. They may have many of these different ramping rates to find the optimal calculations and to get rid of range ambiguities. If the object is moving, it will have the same doppler shift. You now have two equations and two unknowns so you can solve for the two variables of speed and distance. This broadband radar is really nothing new but is way cheaper to make and more reliable than a pulsed system.

 

[dingbat]

Re: broadband vs x band radar

This broadband radar is really nothing new but is way cheaper to make and more reliable than a pulsed system.

Thanks for the explaination. Would have put money on the cheaper to make part of it.

 

[bruceb58]

Re: broadband vs x band radar

That is why we chose that method to make something that would go in an auto.

 

[sr280da]

Re: broadband vs x band radar

This broadband radar is really nothing new but is way cheaper to make and more reliable than a pulsed system.

Do you mean nothing new in the context of radar technology in general, or nothing new in the context of consumer/recreational marine?

For me it comes down to; would I be better off upgrading my Raymarine Pathfinder system with a new C90W display and HD scanner, or converting to Lowrance's 'broadband' radar?

 

[chuckz]

Re: broadband vs x band radar

I didn't explain the difference first time because I didn't realize that a manufacturer was using the term broadband as a marketing gimmick. Once you identified the manufacturer I looked at their website to see what was really going on.

As far as which way is better to go, there is no simple answer. You need to consider: Is the loss of range important to you? What is the equipment cost difference? How old is the system you are upgrading? How long are you going to keep this boat/set up? What is the difference in installation cost and access?

And yes range finding and speed measurements are two different algorithms but many radar system can measure both. I think the previous posts explain this very well.

Sorry if you took offense to my previous post. Just trying to explain what the manufacturer wasn't telling you.

 

[dingbat]

Re: broadband vs x band radar

Do you mean nothing new in the context of radar technology in general, or nothing new in the context of consumer/recreational marine?

For me it comes down to; would I be better off upgrading my Raymarine Pathfinder system with a new C90W display and HD scanner, or converting to Lowrance's 'broadband' radar?

If I was buying a stand alone radar it would be a Furuno.

 

[Texasmark]

Re: broadband vs x band radar

The way the broadband radar works is that a frequency is ramped up and then ramped down. Lets say the sweep frequency started at the carrier frequency of 10GHz and ramped up over a second to 10.1 GHz. If the receiver receives 10.05Ghz, you know the delay is 1/2 of a second and range can be calculated. What makes the equation difficult is that if the object is moving, you will have a doppler shift on it so it might be slightly off. In order to compensate for this, they ramp the frequency from 10.1 GHz back down to 10Ghz over 2 seconds instead of 1. They may have many of these different ramping rates to find the optimal calculations and to get rid of range ambiguities. If the object is moving, it will have the same doppler shift. You now have two equations and two unknowns so you can solve for the two variables of speed and distance. This broadband radar is really nothing new but is way cheaper to make and more reliable than a pulsed system.

Geez Bruce, I knew you would jump on this. Beins you are a processor guy, and I was just the lowly guy that sent the microwave energy out, how was I to know the whole process; well I didn't know the current technology, but I knew the original technology and that is where my roots are.

Thanks for kicking in.

I know this info (what I am about to say) is on the www...any any POS in the world can view it, but Pfssssssssssst. My Doppler roots were with B-52 aircraft measuring ground speed and drift angle. The Doppler shift for just a forward transmitting antenna was not adequate so the systems we used took the forward delta freq and added it to the aft delta frequency (the antenna radiated fore and aft simultaneously) which doubled the frequency error. As I recall, at 176 knots of airspeed, the Doppler shift (measured for and aft additive) was 4 kHz and at twice that speed was 8kHz. A very small proportion of the 10GHz transmitted frequency. Since this info is 40 years old and was not classified Top Secret, Secret, or Confidential, I can say what I want and not worry about betraying my Country. 9 year USAF Vet and a Vietnam era Vet. I'd say Semper Fi; but I was not a US Marine........and all due respect, had no aspirations to be one. The USAF had no such term.

Mark

 

[Texasmark]

Re: broadband vs x band radar

Actually that is not true either. Pulsed radar can also have doppler on it. Was a radar signal processor designer many years of my engineering career. Designed missile, aircraft and automotive radar systems.

You also don't need to have a pulsed radar to measure range. You can have a pseudo FM radar which will give you both range and speed. You just have to know what frequency you transmitted at time X and compare that to the frequency you received at time Y..subtract the frequencies and you have your range. By modulating it in an up and down linear ramp, you can get doppler and range. It is possible that is what this "broadband radars are doing. We designed this type of radar when I was designing auto collision avoidance systems. Way cheaper than a pulsed system.

EDIT:
Yep..that is what they are doing. Same as what we did with our collision avoidance systems.
http://www.lowrance.com/Products/Marine/Broadband-Radar/The-Technology/

Well Bruce, that's what different types of systems design engineers do; they design different types of systems based upon the requirements for the system as dictated by the customer. I told the www what my experiences were; well part of the story...the tellable part. You told the www what yours were.

Mark

 

[kartinkent]

Re: broadband vs x band radar

A revolutionary new advanced Broadband Radar technology is available for a range of popular navigation systems, integrating superior radar performance with state-of-the-art charting, echo sounding and entertainment displays.The X-band is a segment of the microwave radio region of the electromagnetic spectrum.X-band is used in radar applications including continuous-wave, pulsed, single-polarization,dual-polarization, synthetic aperture radar, and phased arrays.X-band radar frequency sub-bands are used in civil, military, and government institutions for weather monitoring, air traffic control, maritime vessel traffic control, defense tracking, and vehicle speed detection for law enforcement.