Communication apparatus for transmitting and receiving signals on different frequency bands

• US 4,627,099 A
• Filed: 12/26/1984
• Issued: 12/02/1986
• Est. Priority Date: 12/28/1983
• Status: Expired due to Term

• Current Assignee: Pioneer Electronic Corporation (Pioneer Corporation)
• Original Assignee: Pioneer Electronic Corporation (Pioneer Corporation)
• Inventors: Shimakata, Masashi
• Primary Examiner(s): Ng, Jin F.
• Application Number:
  US06/686,581
• Time in Patent Office: 706 Days
• Field of Search: 455/76, 455/86, 455/87, 455/112, 455/113, 455/118, 455/119, 331/22, 331/31
• US Class Current: 455/76
• CPC Class Codes: H04B 1/50 using different frequencies for the two directions of communication

Abstract

A communication apparatus comprises a first oscillator for generating a frequency fp₁ at each channel step; a second oscillator for generating a modulated frequency fp₂ ; a first mixer for creating a transmission frequency which is a sum fp₁ +fp₂ of the frequencies of the first and second oscillators and a difference fp₁ -fp₂ therebetween on high and low band transmissions respectively; a third oscillator for generating a frequency fp₃ which is higher or lower than the frequency fp₂ of the second oscillator by a given frequency Δf; and a second mixer for creating a sum fp₁ +fp₃ of the frequencies of the first and third oscillators means and a difference fp₁ -fp₃ therebetween on low and high band transmissions respectively.

Claims

1. A communication apparatus for receiving and transmitting signals at different frequencies comprising

(a) a first oscillator means for generating a frequency fp₁ at each of a plurality of channels;

(b) a second oscillator means for generating a modulated frequency fp₂ ;

(c) a first mixer means for creating a transmission frequency which is a sum fp₁ +fp₂ of the frequencies of the first and second oscillator means and a difference fp₁ -fp₂ therebetween on high and low band transmissions respectively;

(d) a third oscillator means for generating a frequency fp₃ which is higher or lower than the frequency fp₂ of the second oscillator means by a given frequency Δ

f; and

(e) a second mixer means for creating a local oscillator frequency f_L which is a sum fp₁ +fp₃ of the frequencies of the first and third oscillation means at high band transmission and low band receiving modes and a difference fp₁ -fp₃ at low band transmission and high band receiving modes, and

(f) third mixer means for mixing a received signal with the local oscillator frequency f_L to provide an intermediate frequency signal f_IF.

2. The apparatus as defined in claim 1 and further including a circulator between the first mixer means and an antenna for feeding a transmission frequency f_t =fp₁ ±

fp₂ to the antenna from the first mixer means.

3. The apparatus as defined in claim 2 and wherein said third mixer means mixes a receiving frequency of a received signal f_R fed via the circulator with the local oscillator frequency f_L from the second mixer means to provide an intermediate frequency f_IF =|f_L -f_R |.

4. The apparatus as defined in claim 3 in which the receiving frequency f_R is equal to the transmission frequency f_t ±

an transmission-receiving frequency interval Δ

f₁.

5. The apparatus as defined in claim 4 in which the intermediate frequency f_IF is determined as a sum of the transmission receiving frequency interval Δ

f₁ and a difference Δ

f₂,3 between the frequencies fp₂ and fp₃ of the second and third oscillator means.

6. The apparatus as defined in claim 5 in which the frequency difference Δ

f₂,3 is 19.11 MHz and the frequency interval Δ

f₁ is 39 MHz so that the intermediate frequency f_IF is 58.11 MHz.

7. The apparatus as defined in claim 3 and further including a demodulator which demodulates the intermediate frequency signal.

8. The apparatus as defined in claim 3 in which the local frequency f_L from the second mixer means is injected into the third mixer means as lower and higher local frequencies at high and low band receiving modes respectively.

9. The apparatus as defined in claim 1 in which the second mixer means creates a local frequency fp₁ -fp₃ =878.905 MHz at low band transmission and high band receiving modes and a local frequency fp₁ +fp₃ =956.125 MHz at high band transmission and low band receiving modes.

10. The apparatus as defined in claim 1 in which the first, second and third oscillator means include a first, second and third phase locked loops (PLLs) respectively.

11. The apparatus as defined in claim 10 in which the first PLL which forms the first oscillator means has a comparison frequency identical with a channel separation.

12. The apparatus as defined in claim 11 in which the channel separation is 30 KHz and the first PLL provides an oscillation frequency fp₁ which is obtained by multiplying the channel separation by an integer N₁.

13. The apparatus as defined in claim 12 in which N₁ is 31028 and fp₁ is 930.849 MHz at a low band transmission mode and in which N₁ is 30118 and fp₁ is 903.540 MHz at a high band transmission mode.

14. The apparatus as defined in claim 12 further comprising means for switching communication channels by changing N₁.

15. The apparatus as defined in claim 10 in which the second PLL forming the second oscillator means has a comparison frequency which is 65 KHz and provides a frequency fp₂ which is obtained by multiplying the comparison frequency by an integer N₂.

16. The apparatus as defined in claim 15 in which N₂ is 505 and fp₂ is 32.825 MHz at a low band transmission mode and N₂ is 515 and the fp₂ is 33.475 MHz at a high band transmission mode.

17. The apparatus as defined in claim 16 in which direct FM modulation is made in the second oscillation means.

18. The apparatus as defined in claim 10 in which the third PLL forming a third oscillator means has a comparison frequency which is 65 KHz and provides a frequency fp₃ which is obtained by multiplying the comparison frequency by an integer N₃.

19. The apparatus as defined in claim 18 in which N₃ is 799 and fp₃ is 51.953 MHz at a low band transmission mode and the N₃ is 809 and the fp₃ is 52.585 MHz at a high band transmission mode.

20. The apparatus as defined in claim 10 and further including a reference oscillator and a first, second and third frequency dividers having a division ratios N₁, N₂ and N₃ respectively between the reference oscillator and the respective first, second and third oscillator means.

21. The apparatus as defined in claim 20 in which the oscillation frequency of the reference oscillator is a common multiple of the comparison frequencies of the first, second and third PLLs.

22. The apparatus as defined in claim 21 in which the oscillation frequency of the reference oscillator is 12.48 MHz and the frequency division ratio of the first frequency divider N₁ is 1/2⁵ ×

13 and the frequency division ratios of the second and third frequency dividers N₂ and N₃ are 1/2⁶ ×

3.

23. The apparatus as defined in claim 20 in which transmission frequency is changed when high and low band modes are switched by changing the frequency division ratios N₁, N₂ and N₃.